From aebde4488e82a3bd7d71189aa6b1d64f072e2fa7 Mon Sep 17 00:00:00 2001
From: Sukhmani Minhas <50919130+sukhmanm@users.noreply.github.com>
Date: Wed, 10 Mar 2021 13:35:49 -0500
Subject: [PATCH 01/15] ISO formatting

---
 source/sigv4.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)

diff --git a/source/sigv4.c b/source/sigv4.c
index e69de29b..99e55dde 100644
--- a/source/sigv4.c
+++ b/source/sigv4.c
@@ -0,0 +1,91 @@
+/*
+ * SigV4 Utility Library v1.0.0
+ * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+/**
+ * @file sigv4.c
+ * @brief Implements the user-facing functions in sigv4.h
+ */
+
+#include <assert.h>
+#include <string.h>
+#include <time.h>
+
+#include "sigv4.h"
+
+/*-----------------------------------------------------------*/
+
+SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
+                                         size_t dateLen,
+                                         char pDateISO8601[ 17 ] )
+{
+    SigV4Status_t returnStatus = SigV4Success;
+    size_t lenFormatted = 0U;
+    char * pLastChar = NULL;
+    struct tm tm;
+
+    /* Check for NULL parameters. */
+    if( pDate == NULL )
+    {
+        LogError( ( "Parameter check failed: pDate is NULL." ) );
+        returnStatus = SigV4InvalidParameter;
+    }
+    else if( pDateISO8601 == NULL )
+    {
+        LogError( ( "Parameter check failed: pDateISO8601 is NULL." ) );
+        returnStatus = SigV4InvalidParameter;
+    }
+    /* Check validity of the date header size provided. */
+    else if( dateLen == 0U )
+    {
+        LogError( ( "Parameter check failed: dateLen must be greater than 0." ) );
+        returnStatus = SigV4InvalidParameter;
+    }
+
+    if( returnStatus == SigV4Success )
+    {
+        memset( &tm, 0, sizeof( struct tm ) );
+        pLastChar = strptime( pDate, "%Y-%m-%dT%H:%M:%SZ", &tm );
+
+        if( pLastChar == NULL )
+        {
+            LogError( ( "Error matching input to ISO8601 format string." ) );
+            returnStatus == SigV4ISOFormattingError;
+        }
+        else if( pLastChar != '\0' )
+        {
+            LogWarn( ( "Input contained more characters than expected." ) );
+        }
+    }
+
+    if( returnStatus == SigV4Success )
+    {
+        lenFormatted = strftime( pDateISO8601, 17, "%Y%m%dT%H%M%SZ", &tm );
+
+        if( lenFormatted != 16 )
+        {
+            LogError( ( "Formatted string is not of expected length 16." ) );
+            returnStatus = SigV4ISOFormattingError;
+        }
+    }
+
+    return returnStatus;
+}

From 68f8b59656117f764ea991bd22e9270cce92094f Mon Sep 17 00:00:00 2001
From: Sukhmani Minhas <50919130+sukhmanm@users.noreply.github.com>
Date: Tue, 16 Mar 2021 18:01:31 -0400
Subject: [PATCH 02/15] Add buffer size function parameter

---
 source/sigv4.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/source/sigv4.c b/source/sigv4.c
index 99e55dde..fddbb0f4 100644
--- a/source/sigv4.c
+++ b/source/sigv4.c
@@ -35,7 +35,8 @@
 
 SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
                                          size_t dateLen,
-                                         char pDateISO8601[ 17 ] )
+                                         char pDateISO8601[ 17 ],
+                                         size_t dateISO8601Len )
 {
     SigV4Status_t returnStatus = SigV4Success;
     size_t lenFormatted = 0U;
@@ -48,15 +49,23 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
         LogError( ( "Parameter check failed: pDate is NULL." ) );
         returnStatus = SigV4InvalidParameter;
     }
+    /* Check validity of the date header size provided. */
+    else if( dateLen == 0U )
+    {
+        LogError( ( "Parameter check failed: dateLen must be greater than 0." ) );
+        returnStatus = SigV4InvalidParameter;
+    }
     else if( pDateISO8601 == NULL )
     {
         LogError( ( "Parameter check failed: pDateISO8601 is NULL." ) );
         returnStatus = SigV4InvalidParameter;
     }
-    /* Check validity of the date header size provided. */
-    else if( dateLen == 0U )
+
+    /* Check that the buffer provided is large enough for the formatted
+     * output string. */
+    else if( dateISO8601Len < 17U )
     {
-        LogError( ( "Parameter check failed: dateLen must be greater than 0." ) );
+        LogError( ( "Parameter check failed: dateISO8601Len must be at least 17." ) );
         returnStatus = SigV4InvalidParameter;
     }
 
@@ -70,7 +79,7 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
             LogError( ( "Error matching input to ISO8601 format string." ) );
             returnStatus == SigV4ISOFormattingError;
         }
-        else if( pLastChar != '\0' )
+        else if( pLastChar[ 0 ] != '\0' )
         {
             LogWarn( ( "Input contained more characters than expected." ) );
         }

From 19efd2da08c4355dc10d687427932aeed9abdb96 Mon Sep 17 00:00:00 2001
From: Sukhmani Minhas <50919130+sukhmanm@users.noreply.github.com>
Date: Thu, 18 Mar 2021 13:01:35 -0400
Subject: [PATCH 03/15] Rename struct + modify return values

---
 source/sigv4.c | 37 ++++++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/source/sigv4.c b/source/sigv4.c
index fddbb0f4..690e4d14 100644
--- a/source/sigv4.c
+++ b/source/sigv4.c
@@ -38,10 +38,10 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
                                          char pDateISO8601[ 17 ],
                                          size_t dateISO8601Len )
 {
-    SigV4Status_t returnStatus = SigV4Success;
+    SigV4Status_t returnStatus = SigV4ISOFormattingError;
     size_t lenFormatted = 0U;
     char * pLastChar = NULL;
-    struct tm tm;
+    struct tm dateInfo;
 
     /* Check for NULL parameters. */
     if( pDate == NULL )
@@ -63,16 +63,16 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
 
     /* Check that the buffer provided is large enough for the formatted
      * output string. */
-    else if( dateISO8601Len < 17U )
+    else if( dateISO8601Len < ISO_BUFFER_MIN_LEN )
     {
-        LogError( ( "Parameter check failed: dateISO8601Len must be at least 17." ) );
+        LogError( ( "Parameter check failed: dateISO8601Len must be at least %u.",
+                    ISO_BUFFER_MIN_LEN ) );
         returnStatus = SigV4InvalidParameter;
     }
-
-    if( returnStatus == SigV4Success )
+    else
     {
-        memset( &tm, 0, sizeof( struct tm ) );
-        pLastChar = strptime( pDate, "%Y-%m-%dT%H:%M:%SZ", &tm );
+        memset( &dateInfo, 0, sizeof( struct tm ) );
+        pLastChar = strptime( pDate, "%Y-%m-%dT%H:%M:%SZ", &dateInfo );
 
         if( pLastChar == NULL )
         {
@@ -83,16 +83,19 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
         {
             LogWarn( ( "Input contained more characters than expected." ) );
         }
-    }
-
-    if( returnStatus == SigV4Success )
-    {
-        lenFormatted = strftime( pDateISO8601, 17, "%Y%m%dT%H%M%SZ", &tm );
-
-        if( lenFormatted != 16 )
+        else
         {
-            LogError( ( "Formatted string is not of expected length 16." ) );
-            returnStatus = SigV4ISOFormattingError;
+            lenFormatted = strftime( pDateISO8601, ISO_BUFFER_MIN_LEN, "%Y%m%dT%H%M%SZ", &dateInfo );
+
+            if( lenFormatted != ISO_BUFFER_MIN_LEN - 1 )
+            {
+                LogError( ( "Formatted string is not of expected length 16." ) );
+                returnStatus = SigV4ISOFormattingError;
+            }
+            else
+            {
+                returnStatus = SigV4Success;
+            }
         }
     }
 

From 2c61688eb0a103af373e25f4b626368959ac47b4 Mon Sep 17 00:00:00 2001
From: Sukhmani Minhas <50919130+sukhmanm@users.noreply.github.com>
Date: Thu, 18 Mar 2021 15:46:11 -0400
Subject: [PATCH 04/15] Remove formatting failure status

---
 source/sigv4.c | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/source/sigv4.c b/source/sigv4.c
index 690e4d14..556071b2 100644
--- a/source/sigv4.c
+++ b/source/sigv4.c
@@ -38,7 +38,7 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
                                          char pDateISO8601[ 17 ],
                                          size_t dateISO8601Len )
 {
-    SigV4Status_t returnStatus = SigV4ISOFormattingError;
+    SigV4Status_t returnStatus = SigV4InvalidParameter;
     size_t lenFormatted = 0U;
     char * pLastChar = NULL;
     struct tm dateInfo;
@@ -47,50 +47,48 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
     if( pDate == NULL )
     {
         LogError( ( "Parameter check failed: pDate is NULL." ) );
-        returnStatus = SigV4InvalidParameter;
     }
     /* Check validity of the date header size provided. */
     else if( dateLen == 0U )
     {
         LogError( ( "Parameter check failed: dateLen must be greater than 0." ) );
-        returnStatus = SigV4InvalidParameter;
     }
     else if( pDateISO8601 == NULL )
     {
         LogError( ( "Parameter check failed: pDateISO8601 is NULL." ) );
-        returnStatus = SigV4InvalidParameter;
     }
-
-    /* Check that the buffer provided is large enough for the formatted
-     * output string. */
+    /* Check that the buffer provided is large enough for the formatted output
+     * string. */
     else if( dateISO8601Len < ISO_BUFFER_MIN_LEN )
     {
         LogError( ( "Parameter check failed: dateISO8601Len must be at least %u.",
                     ISO_BUFFER_MIN_LEN ) );
-        returnStatus = SigV4InvalidParameter;
     }
     else
     {
         memset( &dateInfo, 0, sizeof( struct tm ) );
+
+        /* Parse pDate according to the input's expected string format, and
+         * populate the date struct with its components.  */
         pLastChar = strptime( pDate, "%Y-%m-%dT%H:%M:%SZ", &dateInfo );
 
         if( pLastChar == NULL )
         {
             LogError( ( "Error matching input to ISO8601 format string." ) );
-            returnStatus == SigV4ISOFormattingError;
         }
         else if( pLastChar[ 0 ] != '\0' )
         {
+            /* The expected pattern was found, but additional characters remain
+             * unparsed in the input string. */
             LogWarn( ( "Input contained more characters than expected." ) );
         }
         else
-        {
+            /* Construct ISO 8601 string using members of populated date struct. */
             lenFormatted = strftime( pDateISO8601, ISO_BUFFER_MIN_LEN, "%Y%m%dT%H%M%SZ", &dateInfo );
 
             if( lenFormatted != ISO_BUFFER_MIN_LEN - 1 )
             {
                 LogError( ( "Formatted string is not of expected length 16." ) );
-                returnStatus = SigV4ISOFormattingError;
             }
             else
             {

From f74fce828ecc5eb2acd04042a15da0c76455abee Mon Sep 17 00:00:00 2001
From: Sukhmani Minhas <50919130+sukhmanm@users.noreply.github.com>
Date: Thu, 18 Mar 2021 16:27:35 -0400
Subject: [PATCH 05/15] Undo enum deletion + allow longer inputs

---
 source/sigv4.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/source/sigv4.c b/source/sigv4.c
index 556071b2..8f350295 100644
--- a/source/sigv4.c
+++ b/source/sigv4.c
@@ -57,6 +57,7 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
     {
         LogError( ( "Parameter check failed: pDateISO8601 is NULL." ) );
     }
+
     /* Check that the buffer provided is large enough for the formatted output
      * string. */
     else if( dateISO8601Len < ISO_BUFFER_MIN_LEN )
@@ -75,20 +76,24 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
         if( pLastChar == NULL )
         {
             LogError( ( "Error matching input to ISO8601 format string." ) );
-        }
-        else if( pLastChar[ 0 ] != '\0' )
-        {
-            /* The expected pattern was found, but additional characters remain
-             * unparsed in the input string. */
-            LogWarn( ( "Input contained more characters than expected." ) );
+            returnStatus = SigV4ISOFormattingError;
         }
         else
+        {
+            if( pLastChar[ 0 ] != '\0' )
+            {
+                /* The expected pattern was found, but additional characters remain
+                 * unparsed in the input string. */
+                LogWarn( ( "Input contained more characters than expected." ) );
+            }
+
             /* Construct ISO 8601 string using members of populated date struct. */
             lenFormatted = strftime( pDateISO8601, ISO_BUFFER_MIN_LEN, "%Y%m%dT%H%M%SZ", &dateInfo );
 
             if( lenFormatted != ISO_BUFFER_MIN_LEN - 1 )
             {
                 LogError( ( "Formatted string is not of expected length 16." ) );
+                returnStatus = SigV4ISOFormattingError;
             }
             else
             {

From dcce43067681c1a34947609d56a8c9f7bab441e0 Mon Sep 17 00:00:00 2001
From: Sukhmani Minhas <50919130+sukhmanm@users.noreply.github.com>
Date: Fri, 19 Mar 2021 15:20:40 -0400
Subject: [PATCH 06/15] Replace strptime() with sscanf()

---
 source/sigv4.c | 38 +++++++++++++++++++++-----------------
 1 file changed, 21 insertions(+), 17 deletions(-)

diff --git a/source/sigv4.c b/source/sigv4.c
index 8f350295..6b531c61 100644
--- a/source/sigv4.c
+++ b/source/sigv4.c
@@ -25,6 +25,7 @@
  * @brief Implements the user-facing functions in sigv4.h
  */
 
+#include <stdio.h>
 #include <assert.h>
 #include <string.h>
 #include <time.h>
@@ -35,12 +36,11 @@
 
 SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
                                          size_t dateLen,
-                                         char pDateISO8601[ 17 ],
+                                         char * pDateISO8601,
                                          size_t dateISO8601Len )
 {
     SigV4Status_t returnStatus = SigV4InvalidParameter;
     size_t lenFormatted = 0U;
-    char * pLastChar = NULL;
     struct tm dateInfo;
 
     /* Check for NULL parameters. */
@@ -60,10 +60,10 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
 
     /* Check that the buffer provided is large enough for the formatted output
      * string. */
-    else if( dateISO8601Len < ISO_BUFFER_MIN_LEN )
+    else if( dateISO8601Len < SIV4_ISO_STRING_LEN + 1 )
     {
         LogError( ( "Parameter check failed: dateISO8601Len must be at least %u.",
-                    ISO_BUFFER_MIN_LEN ) );
+                    SIV4_ISO_STRING_LEN + 1 ) );
     }
     else
     {
@@ -71,28 +71,32 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
 
         /* Parse pDate according to the input's expected string format, and
          * populate the date struct with its components.  */
-        pLastChar = strptime( pDate, "%Y-%m-%dT%H:%M:%SZ", &dateInfo );
-
-        if( pLastChar == NULL )
+        if( sscanf( pDate, "%4d-%2d-%2dT%2d:%2d:%2dZ",
+                    &dateInfo.tm_year,
+                    &dateInfo.tm_mon,
+                    &dateInfo.tm_mday,
+                    &dateInfo.tm_hour,
+                    &dateInfo.tm_min,
+                    &dateInfo.tm_sec ) != SIV4_ISO_STRING_LEN - 10U )
         {
-            LogError( ( "Error matching input to ISO8601 format string." ) );
+            LogError( ( "sscanf() failed to parse the date string using the format expected." ) );
             returnStatus = SigV4ISOFormattingError;
         }
         else
         {
-            if( pLastChar[ 0 ] != '\0' )
-            {
-                /* The expected pattern was found, but additional characters remain
-                 * unparsed in the input string. */
-                LogWarn( ( "Input contained more characters than expected." ) );
-            }
+            /* Standardize month and year values for struct tm's specifications:
+             *  - tm_mon = "months from January" (0-11)
+             *  - tm_year = "years since 1900" */
+            dateInfo.tm_mon--;
+            dateInfo.tm_year -= 1900;
 
             /* Construct ISO 8601 string using members of populated date struct. */
-            lenFormatted = strftime( pDateISO8601, ISO_BUFFER_MIN_LEN, "%Y%m%dT%H%M%SZ", &dateInfo );
+            lenFormatted = strftime( pDateISO8601, SIV4_ISO_STRING_LEN + 1, "%Y%m%dT%H%M%SZ", &dateInfo );
 
-            if( lenFormatted != ISO_BUFFER_MIN_LEN - 1 )
+            if( lenFormatted != SIV4_ISO_STRING_LEN )
             {
-                LogError( ( "Formatted string is not of expected length 16." ) );
+                LogError( ( "Formatted string is not of expected length %u.",
+                            SIV4_ISO_STRING_LEN ) );
                 returnStatus = SigV4ISOFormattingError;
             }
             else

From 6672462f10a93d045e7f27f0695721651a76cc53 Mon Sep 17 00:00:00 2001
From: Sukhmani Minhas <50919130+sukhmanm@users.noreply.github.com>
Date: Fri, 19 Mar 2021 19:55:23 -0400
Subject: [PATCH 07/15] Add dateLen check

---
 source/include/sigv4.h |  1 +
 source/sigv4.c         | 17 ++++++++++-------
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/source/include/sigv4.h b/source/include/sigv4.h
index dd86e208..362b5333 100644
--- a/source/include/sigv4.h
+++ b/source/include/sigv4.h
@@ -67,6 +67,7 @@
 
 /**< Length of the date header in ISO 8601 format. */
 #define SIGV4_ISO_STRING_LEN                        16U
+#define SIGV4_EXPECTED_DATE_LEN                     20U
 /** @}*/
 
 /**
diff --git a/source/sigv4.c b/source/sigv4.c
index 6b531c61..9b6d5caa 100644
--- a/source/sigv4.c
+++ b/source/sigv4.c
@@ -48,17 +48,20 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
     {
         LogError( ( "Parameter check failed: pDate is NULL." ) );
     }
-    /* Check validity of the date header size provided. */
-    else if( dateLen == 0U )
-    {
-        LogError( ( "Parameter check failed: dateLen must be greater than 0." ) );
-    }
     else if( pDateISO8601 == NULL )
     {
         LogError( ( "Parameter check failed: pDateISO8601 is NULL." ) );
     }
 
-    /* Check that the buffer provided is large enough for the formatted output
+    /* Check that the date buffer provided is not shorter than the expected
+     * input format. */
+    else if( dateLen < SIGV4_EXPECTED_DATE_LEN + 1 )
+    {
+        LogError( ( "Parameter check failed: dateLen must be at least %u.",
+                    SIGV4_EXPECTED_DATE_LEN + 1 ) );
+    }
+
+    /* Check that the output buffer provided is large enough for the formatted
      * string. */
     else if( dateISO8601Len < SIV4_ISO_STRING_LEN + 1 )
     {
@@ -77,7 +80,7 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
                     &dateInfo.tm_mday,
                     &dateInfo.tm_hour,
                     &dateInfo.tm_min,
-                    &dateInfo.tm_sec ) != SIV4_ISO_STRING_LEN - 10U )
+                    &dateInfo.tm_sec ) != 6 )
         {
             LogError( ( "sscanf() failed to parse the date string using the format expected." ) );
             returnStatus = SigV4ISOFormattingError;

From 1f1db6c12dde56f5a7025446580dd6ff5d7b8517 Mon Sep 17 00:00:00 2001
From: Sukhmani Minhas <50919130+sukhmanm@users.noreply.github.com>
Date: Thu, 25 Mar 2021 17:46:57 -0400
Subject: [PATCH 08/15] Addressing feedback

---
 source/include/sigv4.h |  8 ++++++--
 source/sigv4.c         | 23 ++++++++++++-----------
 2 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/source/include/sigv4.h b/source/include/sigv4.h
index 362b5333..0c8e484d 100644
--- a/source/include/sigv4.h
+++ b/source/include/sigv4.h
@@ -67,7 +67,8 @@
 
 /**< Length of the date header in ISO 8601 format. */
 #define SIGV4_ISO_STRING_LEN                        16U
-#define SIGV4_EXPECTED_DATE_LEN                     20U
+/**< Length of the date header found in AWS IoT's HTTP response. */
+#define SIGV4_EXPECTED_AWS_IOT_DATE_LEN             20U
 /** @}*/
 
 /**
@@ -380,9 +381,12 @@ SigV4Status_t SigV4_GenerateHTTPAuthorization( const SigV4Parameters_t * pParams
 
 /**
  * @brief Parse the date header value from the AWS IoT response.
+ *
  * The AWS IoT response date is of the form: 2018-01-18T09:18:06Z.
+ * The ISO8601-formatted date is: 20180118T091806Z.
  *
- * @param[in] pDate The date header value.
+ * @param[in] pDate The RFC3339-formatted date header value, found in the HTTP
+ * response returned by AWS IoT (ex. "2018-01-18T09:18:06Z").
  * @param[in] dateLen length of the pDate header value.
  * @param[out] pDateISO8601 The ISO8601 format compliant date. This buffer must
  * be large enough to hold both the ISO8601-formatted date (16 characters) and
diff --git a/source/sigv4.c b/source/sigv4.c
index 9b6d5caa..acb9f53f 100644
--- a/source/sigv4.c
+++ b/source/sigv4.c
@@ -40,8 +40,6 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
                                          size_t dateISO8601Len )
 {
     SigV4Status_t returnStatus = SigV4InvalidParameter;
-    size_t lenFormatted = 0U;
-    struct tm dateInfo;
 
     /* Check for NULL parameters. */
     if( pDate == NULL )
@@ -55,22 +53,22 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
 
     /* Check that the date buffer provided is not shorter than the expected
      * input format. */
-    else if( dateLen < SIGV4_EXPECTED_DATE_LEN + 1 )
+    else if( dateLen < SIGV4_EXPECTED_AWS_IOT_DATE_LEN )
     {
         LogError( ( "Parameter check failed: dateLen must be at least %u.",
-                    SIGV4_EXPECTED_DATE_LEN + 1 ) );
+                    SIGV4_EXPECTED_AWS_IOT_DATE_LEN ) );
     }
 
     /* Check that the output buffer provided is large enough for the formatted
      * string. */
-    else if( dateISO8601Len < SIV4_ISO_STRING_LEN + 1 )
+    else if( dateISO8601Len < SIGV4_ISO_STRING_LEN + 1 )
     {
         LogError( ( "Parameter check failed: dateISO8601Len must be at least %u.",
-                    SIV4_ISO_STRING_LEN + 1 ) );
+                    SIGV4_ISO_STRING_LEN + 1 ) );
     }
     else
     {
-        memset( &dateInfo, 0, sizeof( struct tm ) );
+        struct tm dateInfo = { 0 };
 
         /* Parse pDate according to the input's expected string format, and
          * populate the date struct with its components.  */
@@ -87,6 +85,8 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
         }
         else
         {
+            size_t lenFormatted = 0U;
+
             /* Standardize month and year values for struct tm's specifications:
              *  - tm_mon = "months from January" (0-11)
              *  - tm_year = "years since 1900" */
@@ -94,12 +94,13 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
             dateInfo.tm_year -= 1900;
 
             /* Construct ISO 8601 string using members of populated date struct. */
-            lenFormatted = strftime( pDateISO8601, SIV4_ISO_STRING_LEN + 1, "%Y%m%dT%H%M%SZ", &dateInfo );
+            lenFormatted = strftime( pDateISO8601, SIGV4_ISO_STRING_LEN + 1, "%Y%m%dT%H%M%SZ", &dateInfo );
 
-            if( lenFormatted != SIV4_ISO_STRING_LEN )
+            if( lenFormatted != SIGV4_ISO_STRING_LEN )
             {
-                LogError( ( "Formatted string is not of expected length %u.",
-                            SIV4_ISO_STRING_LEN ) );
+                LogError( ( "Failed to generate ISO 8601 date: Call to strftime() for string formatting failed: "
+                            "ExpectedReturnValue=%u, ActualReturnValue=%lu.",
+                            SIGV4_ISO_STRING_LEN, lenFormatted ) );
                 returnStatus = SigV4ISOFormattingError;
             }
             else

From c132711073e057082d8d978e53ac4cad1786231a Mon Sep 17 00:00:00 2001
From: sukhmanm <sukhmanm@amazon.com>
Date: Fri, 26 Mar 2021 15:50:33 -0400
Subject: [PATCH 09/15] Doxygen updates

---
 source/include/sigv4.h | 30 +++++++++++++++++++++++-------
 source/sigv4.c         |  4 ++--
 2 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/source/include/sigv4.h b/source/include/sigv4.h
index 0c8e484d..098d6b40 100644
--- a/source/include/sigv4.h
+++ b/source/include/sigv4.h
@@ -380,19 +380,35 @@ SigV4Status_t SigV4_GenerateHTTPAuthorization( const SigV4Parameters_t * pParams
                                                size_t * signatureLen );
 
 /**
- * @brief Parse the date header value from the AWS IoT response.
+ * @brief Parse the date header value from the AWS IoT response, and generate
+ * the formatted ISO 8601 date required for authentication.
  *
- * The AWS IoT response date is of the form: 2018-01-18T09:18:06Z.
- * The ISO8601-formatted date is: 20180118T091806Z.
+ * This is an optional utility function available to the application, to assist
+ * with formatting of the date header obtained from AWS IoT (when requesting a
+ * temporary token or sending a POST request).
  *
- * @param[in] pDate The RFC3339-formatted date header value, found in the HTTP
- * response returned by AWS IoT (ex. "2018-01-18T09:18:06Z").
- * @param[in] dateLen length of the pDate header value.
+ * AWS SigV4 authentication requires an ISO 8601 date to be present in the
+ * "x-amz-date" request header, as well as in the credential scope (must be
+ * identical). For additional information on date handling, please see
+ * https://docs.aws.amazon.com/general/latest/gr/sigv4-date-handling.html.
+ *
+ * Formatting Overview:
+ * - The AWS IoT response date is of the form "YYYY-MM-DD'T'hh:mm:ss'Z'" (ex.
+ *   "2018-01-18T09:18:06Z").
+ * - The ISO8601-formatted date is of the form "YYYYMMDD'T'HHMMSS'Z'" (ex.
+ *   "20180118T091806Z").
+ *
+ * @param[in] pDate The date header (in
+ * [RFC339](https://tools.ietf.org/html/rfc3339) format), found in the HTTP
+ * response returned by AWS IoT. This value is expected to be 20 characters in
+ * length, to comply with the RFC339 formatting standard used in the response.
+ * @param[in] dateLen The length of the pDate header value. Must be at least
+ * #SIGV4_EXPECTED_AWS_IOT_DATE_LEN, for valid input parameters.
  * @param[out] pDateISO8601 The ISO8601 format compliant date. This buffer must
  * be large enough to hold both the ISO8601-formatted date (16 characters) and
  * the terminating null character (17 in total).
  * @param[in] dateISO8601Len The length of buffer pDateISO8601. Must be at least
- * 17 for valid input parameters.
+ * #SIGV4_ISO_STRING_LEN bytes, for valid input parameters.
  *
  * @return #SigV4Success code if successful, error code otherwise.
  */
diff --git a/source/sigv4.c b/source/sigv4.c
index acb9f53f..ca74fb4a 100644
--- a/source/sigv4.c
+++ b/source/sigv4.c
@@ -80,7 +80,7 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
                     &dateInfo.tm_min,
                     &dateInfo.tm_sec ) != 6 )
         {
-            LogError( ( "sscanf() failed to parse the date string using the format expected." ) );
+            LogError( ( "Failed to generate ISO 8601 date: call to sscanf() for input parsing failed." ) );
             returnStatus = SigV4ISOFormattingError;
         }
         else
@@ -98,7 +98,7 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
 
             if( lenFormatted != SIGV4_ISO_STRING_LEN )
             {
-                LogError( ( "Failed to generate ISO 8601 date: Call to strftime() for string formatting failed: "
+                LogError( ( "Failed to generate ISO 8601 date: call to strftime() for string formatting failed: "
                             "ExpectedReturnValue=%u, ActualReturnValue=%lu.",
                             SIGV4_ISO_STRING_LEN, lenFormatted ) );
                 returnStatus = SigV4ISOFormattingError;

From 39b00e48f4539254af2a86b498153d1ca225fa74 Mon Sep 17 00:00:00 2001
From: sukhmanm <sukhmanm@amazon.com>
Date: Tue, 30 Mar 2021 02:20:17 -0400
Subject: [PATCH 10/15] Add formatDate() and verify dateInfo

---
 source/include/sigv4.h |  11 +--
 source/sigv4.c         | 166 ++++++++++++++++++++++++++++++-----------
 2 files changed, 129 insertions(+), 48 deletions(-)

diff --git a/source/include/sigv4.h b/source/include/sigv4.h
index 098d6b40..67b6981d 100644
--- a/source/include/sigv4.h
+++ b/source/include/sigv4.h
@@ -398,11 +398,12 @@ SigV4Status_t SigV4_GenerateHTTPAuthorization( const SigV4Parameters_t * pParams
  * - The ISO8601-formatted date is of the form "YYYYMMDD'T'HHMMSS'Z'" (ex.
  *   "20180118T091806Z").
  *
- * @param[in] pDate The date header (in
- * [RFC339](https://tools.ietf.org/html/rfc3339) format), found in the HTTP
- * response returned by AWS IoT. This value is expected to be 20 characters in
- * length, to comply with the RFC339 formatting standard used in the response.
- * @param[in] dateLen The length of the pDate header value. Must be at least
+ * @param[in] pDate The date header (in [RFC3339
+ * format](https://tools.ietf.org/html/rfc3339)), found in the HTTP response
+ * returned by AWS IoT. This value should use UTC (indicated by the "Z"
+ * character postfix, with no time-zone offset), and be 20 characters in length
+ * (excluding the null character).
+ * @param[in] dateLen The length of the pDate header value. Must be
  * #SIGV4_EXPECTED_AWS_IOT_DATE_LEN, for valid input parameters.
  * @param[out] pDateISO8601 The ISO8601 format compliant date. This buffer must
  * be large enough to hold both the ISO8601-formatted date (16 characters) and
diff --git a/source/sigv4.c b/source/sigv4.c
index ca74fb4a..d6a809ea 100644
--- a/source/sigv4.c
+++ b/source/sigv4.c
@@ -34,59 +34,97 @@
 
 /*-----------------------------------------------------------*/
 
-SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
-                                         size_t dateLen,
-                                         char * pDateISO8601,
-                                         size_t dateISO8601Len )
-{
-    SigV4Status_t returnStatus = SigV4InvalidParameter;
+/**
+ * @brief Format an ISO 8601 date, and fill the output buffer with the result.
+ *
+ * @param[in] pDate The date to be formatted, in RFC3339 format.
+ * @param[in] pDateISO8601 The buffer to hold the ISO 8601 encoded date.
+ *
+ * @return #SigV4Success if successful, and #SigV4ISOFormattingError if a
+ * parsing error occurred due to an incorrectly formatted date. If pDate is
+ * correctly formatted but contains an out-of-range date, #SigV4InvalidParameter
+ * is returned.
+ */
+static SigV4Status_t formatDate( const char * pDate,
+                                 char * pDateISO8601 );
 
-    /* Check for NULL parameters. */
-    if( pDate == NULL )
-    {
-        LogError( ( "Parameter check failed: pDate is NULL." ) );
-    }
-    else if( pDateISO8601 == NULL )
-    {
-        LogError( ( "Parameter check failed: pDateISO8601 is NULL." ) );
-    }
+/*-----------------------------------------------------------*/
 
-    /* Check that the date buffer provided is not shorter than the expected
-     * input format. */
-    else if( dateLen < SIGV4_EXPECTED_AWS_IOT_DATE_LEN )
-    {
-        LogError( ( "Parameter check failed: dateLen must be at least %u.",
-                    SIGV4_EXPECTED_AWS_IOT_DATE_LEN ) );
-    }
+static SigV4Status_t formatDate( const char * pDate,
+                                 char * pDateISO8601 )
+{
+    SigV4Status_t returnStatus = SigV4ISOFormattingError;
+    struct tm dateInfo = { 0 };
 
-    /* Check that the output buffer provided is large enough for the formatted
-     * string. */
-    else if( dateISO8601Len < SIGV4_ISO_STRING_LEN + 1 )
+    /* Parse pDate according to the input's expected string format, and populate
+     * the date struct with its components.  */
+    if( sscanf( pDate, "%4d-%2d-%2dT%2d:%2d:%2dZ",
+                &dateInfo.tm_year,
+                &dateInfo.tm_mon,
+                &dateInfo.tm_mday,
+                &dateInfo.tm_hour,
+                &dateInfo.tm_min,
+                &dateInfo.tm_sec ) != 6 )
     {
-        LogError( ( "Parameter check failed: dateISO8601Len must be at least %u.",
-                    SIGV4_ISO_STRING_LEN + 1 ) );
+        LogError( ( "Failed to generate ISO 8601 date: call to sscanf() for input parsing failed." ) );
+        returnStatus = SigV4ISOFormattingError;
     }
     else
     {
-        struct tm dateInfo = { 0 };
-
-        /* Parse pDate according to the input's expected string format, and
-         * populate the date struct with its components.  */
-        if( sscanf( pDate, "%4d-%2d-%2dT%2d:%2d:%2dZ",
-                    &dateInfo.tm_year,
-                    &dateInfo.tm_mon,
-                    &dateInfo.tm_mday,
-                    &dateInfo.tm_hour,
-                    &dateInfo.tm_min,
-                    &dateInfo.tm_sec ) != 6 )
+        size_t lenFormatted = 0U;
+
+        if( ( dateInfo.tm_year < 1900 ) )
+        {
+            LogError( ( "Invalid 'year' value parsed from date string. "
+                        "Expected an integer larger than 1900, received: %ld",
+                        ( long int ) dateInfo.tm_year ) );
+            returnStatus = SigV4InvalidParameter;
+        }
+
+        if( ( dateInfo.tm_mon < 1 ) || ( dateInfo.tm_mon > 12 ) )
+        {
+            LogError( ( "Invalid 'month' value parsed from date string. "
+                        "Expected an integer between 1 and 12, received: %ld",
+                        ( long int ) dateInfo.tm_mon ) );
+            returnStatus = SigV4InvalidParameter;
+        }
+
+        if( ( dateInfo.tm_mday < 1 ) || ( dateInfo.tm_mday > 31 ) )
+        {
+            LogError( ( "Invalid 'day' value parsed from date string. "
+                        "Expected an integer between 1 and 31, received: %ld",
+                        ( long int ) dateInfo.tm_mday ) );
+            returnStatus = SigV4InvalidParameter;
+        }
+
+        if( ( dateInfo.tm_hour < 0 ) || ( dateInfo.tm_hour > 23 ) )
+        {
+            LogError( ( "Invalid 'hour' value parsed from date string. "
+                        "Expected an integer between 0 and 23, received: %ld",
+                        ( long int ) dateInfo.tm_hour ) );
+            returnStatus = SigV4InvalidParameter;
+        }
+
+        if( ( dateInfo.tm_min < 0 ) || ( dateInfo.tm_min > 59 ) )
         {
-            LogError( ( "Failed to generate ISO 8601 date: call to sscanf() for input parsing failed." ) );
-            returnStatus = SigV4ISOFormattingError;
+            LogError( ( "Invalid 'minute' value parsed from date string. "
+                        "Expected an integer between 0 and 59, received: %ld",
+                        ( long int ) dateInfo.tm_min ) );
+            returnStatus = SigV4InvalidParameter;
         }
-        else
+
+        /* C90 allows for an additional leap second corresponding to the (rare)
+         * UTC adjustment. */
+        if( ( dateInfo.tm_sec < 0 ) || ( dateInfo.tm_sec > 60 ) )
         {
-            size_t lenFormatted = 0U;
+            LogError( ( "Invalid 'second' value parsed from date string. "
+                        "Expected an integer between 0 and 60, received: %ld",
+                        ( long int ) dateInfo.tm_sec ) );
+            returnStatus = SigV4InvalidParameter;
+        }
 
+        if( returnStatus != SigV4InvalidParameter )
+        {
             /* Standardize month and year values for struct tm's specifications:
              *  - tm_mon = "months from January" (0-11)
              *  - tm_year = "years since 1900" */
@@ -100,7 +138,8 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
             {
                 LogError( ( "Failed to generate ISO 8601 date: call to strftime() for string formatting failed: "
                             "ExpectedReturnValue=%u, ActualReturnValue=%lu.",
-                            SIGV4_ISO_STRING_LEN, lenFormatted ) );
+                            SIGV4_ISO_STRING_LEN,
+                            ( unsigned long ) lenFormatted ) );
                 returnStatus = SigV4ISOFormattingError;
             }
             else
@@ -112,3 +151,44 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
 
     return returnStatus;
 }
+
+/*-----------------------------------------------------------*/
+
+SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
+                                         size_t dateLen,
+                                         char * pDateISO8601,
+                                         size_t dateISO8601Len )
+{
+    SigV4Status_t returnStatus = SigV4InvalidParameter;
+
+    /* Check for NULL parameters. */
+    if( pDate == NULL )
+    {
+        LogError( ( "Parameter check failed: pDate is NULL." ) );
+    }
+    else if( pDateISO8601 == NULL )
+    {
+        LogError( ( "Parameter check failed: pDateISO8601 is NULL." ) );
+    }
+
+    /* Check that the date provided is of the expected length. */
+    else if( dateLen != SIGV4_EXPECTED_AWS_IOT_DATE_LEN )
+    {
+        LogError( ( "Parameter check failed: dateLen must be %u.",
+                    SIGV4_EXPECTED_AWS_IOT_DATE_LEN ) );
+    }
+
+    /* Check that the output buffer provided is large enough for the formatted
+     * string. */
+    else if( dateISO8601Len < SIGV4_ISO_STRING_LEN + 1 )
+    {
+        LogError( ( "Parameter check failed: dateISO8601Len must be at least %u.",
+                    SIGV4_ISO_STRING_LEN + 1 ) );
+    }
+    else
+    {
+        returnStatus = formatDate( pDate, pDateISO8601 );
+    }
+
+    return returnStatus;
+}

From 3a7e5614dc0299d7da0b896b96d8348048235482 Mon Sep 17 00:00:00 2001
From: sukhmanm <sukhmanm@amazon.com>
Date: Thu, 1 Apr 2021 12:17:43 -0400
Subject: [PATCH 11/15] Add parsing implementation

---
 source/include/sigv4.h          |   6 +-
 source/include/sigv4_internal.h |  68 +++++++++
 source/sigv4.c                  | 236 +++++++++++++++++++++++++++-----
 3 files changed, 271 insertions(+), 39 deletions(-)
 create mode 100644 source/include/sigv4_internal.h

diff --git a/source/include/sigv4.h b/source/include/sigv4.h
index 67b6981d..13c89963 100644
--- a/source/include/sigv4.h
+++ b/source/include/sigv4.h
@@ -67,8 +67,10 @@
 
 /**< Length of the date header in ISO 8601 format. */
 #define SIGV4_ISO_STRING_LEN                        16U
-/**< Length of the date header found in AWS IoT's HTTP response. */
-#define SIGV4_EXPECTED_AWS_IOT_DATE_LEN             20U
+/**< Expected length of an RFC 3339 date input. */
+#define SIGV4_EXPECTED_LEN_RFC_3339                 20U
+/**< Expected length of an RFC 5322 date input. */
+#define SIGV4_EXPECTED_LEN_RFC_5322                 29U
 /** @}*/
 
 /**
diff --git a/source/include/sigv4_internal.h b/source/include/sigv4_internal.h
new file mode 100644
index 00000000..4db9d06d
--- /dev/null
+++ b/source/include/sigv4_internal.h
@@ -0,0 +1,68 @@
+/*
+ * SigV4 Utility Library v1.0.0
+ * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+/**
+ * @file sigv4_internal.h
+ * @brief Internal definitions for the SigV4 Client Utility Library.
+ */
+
+#ifndef SIGV4_INTERNAL_H_
+#define SIGV4_INTERNAL_H_
+
+/* Constants for date verification. */
+#define YEAR_MIN               1900L /**< Minimum year accepted. */
+
+/**
+ * @brief Month name abbreviations for RFC 5322 date parsing.
+ */
+#define MONTH_NAMES            { "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" }
+
+/**
+ * @brief Number of days in each respective month.
+ */
+#define MONTH_DAYS             { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
+
+#define FORMAT_RFC_3339        "%4Y-%2M-%2DT%2h:%2m:%2sZ"         /**< Format string to parse RFC 3339 date. */
+#define FORMAT_RFC_3339_LEN    sizeof( FORMAT_RFC_3339 ) - 1U     /**< Length of the RFC 3339 format string. */
+
+#define FORMAT_RFC_5322        "%3*, %2D %3M %4Y %2h:%2m:%2s GMT" /**< Format string to parse RFC 5322 date. */
+#define FORMAT_RFC_5322_LEN    sizeof( FORMAT_RFC_5322 ) - 1U     /**< Length of the RFC 3339 format string. */
+
+#define ISO_YEAR_LEN           4U                                 /**< Length of year value in ISO 8601 date. */
+#define ISO_NON_YEAR_LEN       2U                                 /**< Length of non-year values in ISO 8601 date. */
+
+/**
+ * @brief An aggregator representing the individually parsed elements of the
+ * user-provided date parameter. This is used to verify the complete date
+ * representation, and construct the final ISO 8601 string.
+ */
+typedef struct SigV4DateTime
+{
+    int32_t tm_year; /**< Year (>= 1900) */
+    int32_t tm_mon;  /**< Month (1 to 12) */
+    int32_t tm_mday; /**< Day of Month (1 to 28/29/20/31) */
+    int32_t tm_hour; /**< Hour (0 to 23) */
+    int32_t tm_min;  /**< Minutes (0 to 59) */
+    int32_t tm_sec;  /**< Seconds (0 to 60) */
+} SigV4DateTime_t;
+
+#endif /* ifndef SIGV4_INTERNAL_H_ */
diff --git a/source/sigv4.c b/source/sigv4.c
index d6a809ea..e2987477 100644
--- a/source/sigv4.c
+++ b/source/sigv4.c
@@ -25,15 +25,37 @@
  * @brief Implements the user-facing functions in sigv4.h
  */
 
-#include <stdio.h>
 #include <assert.h>
 #include <string.h>
-#include <time.h>
+#include <ctype.h>
 
 #include "sigv4.h"
+#include "sigv4_internal.h"
 
 /*-----------------------------------------------------------*/
 
+/**
+ * @brief Parses date according to format string parameter, and populates date
+ * representation struct SigV4DateTime_t with its elements.
+ *
+ * @param[in] pDate The date to be parsed.
+ * @param[in] dateLen Length of pDate, the date to be formatted.
+ * @param[in] pFormat The format string used to extract date pDateElements from pDate.
+ * This string, among other characters, may contain specifiers of the form
+ * "%LV", where L is the number of characters to be readLoc, and V is one of
+ * {Y, M, D, h, m, s, *}, representing a year, month, day, hour, minute, second,
+ * or skipped (un-parsed) value, respectively.
+ * @param[in] formatLen Length of the format string pFormat.
+ * @param[out] pDateElements The deconstructed date representation of pDate.
+ *
+ * @return The number of format specifiers found and filled in pDateElements.
+ */
+static size_t parseDate( const char * pDate,
+                         size_t dateLen,
+                         const char * pFormat,
+                         size_t formatLen,
+                         SigV4DateTime_t * pDateElements );
+
 /**
  * @brief Format an ISO 8601 date, and fill the output buffer with the result.
  *
@@ -68,26 +90,164 @@ static SigV4Status_t formatDate( const char * pDate,
     {
         LogError( ( "Failed to generate ISO 8601 date: call to sscanf() for input parsing failed." ) );
         returnStatus = SigV4ISOFormattingError;
-    }
-    else
+
+static size_t parseDate( const char * pDate,
+                         size_t dateLen,
+                         const char * pFormat,
+                         size_t formatLen,
+                         SigV4DateTime_t * pDateElements )
+{
+    size_t readLoc = 0U, lenToRead = 0U, formatIndex = 0U, count = 0U;
+    int32_t result = 0;
+    char * pMonthNames[] = MONTH_NAMES;
+
+    assert( pDate != NULL );
+    assert( pFormat != NULL );
+    assert( pDateElements != NULL );
+
+    /* Loop through format string. */
+    while( formatIndex < formatLen )
     {
-        size_t lenFormatted = 0U;
+        if( pFormat[ formatIndex ] == '%' )
+        {
+            /* '%' must be followed by a length and type specification. */
+            assert( formatIndex < formatLen - 2 );
 
-        if( ( dateInfo.tm_year < 1900 ) )
+            /* Numerical value of length specifier character. */
+            lenToRead = pFormat[ ++formatIndex ] - '0';
+            result = 0;
+
+            /* Ensure read is within buffer bounds. */
+            assert( readLoc + lenToRead - 1 < dateLen );
+
+            /* Read specified characters from pDate. */
+            do
+            {
+                if( !isdigit( pDate[ readLoc ] ) )
+                {
+                    /* Month and skipped characters can be non-numeric, and are
+                     * handled by the switch statement. */
+                    if( ( pFormat[ formatIndex + 1U ] != 'M' ) &&
+                        ( pFormat[ formatIndex + 1U ] != '*' ) )
+                    {
+                        LogError( ( "Parsing Error: Expected numerical string of type '%%%d%c', "
+                                    "but received '%.*s'.",
+                                    ( int ) lenToRead,
+                                    pFormat[ formatIndex + 1U ],
+                                    ( int ) lenToRead,
+                                    &pDate[ readLoc ] ) );
+                    }
+
+                    /* Set invalid value to allow switch statement to handle
+                     * case based on specifier. */
+                    result = -1;
+                    break;
+                }
+
+                result = result * 10 + ( pDate[ readLoc++ ] - '0' );
+            } while( --lenToRead );
+
+            switch( pFormat[ ++formatIndex ] )
+            {
+                case 'Y':
+                    pDateElements->tm_year = result;
+                    count += ( result != -1 ) ? 1 : 0;
+                    break;
+
+                case 'M':
+
+                    /* Numerical month representation (ex. RFC 3339). */
+                    if( result > 0 )
+                    {
+                        pDateElements->tm_mon = result;
+                        count++;
+                    }
+                    /* Non-numerical month representation (ex. RFC 5322). */
+                    else if( lenToRead == 3U )
+                    {
+                        result = 0;
+
+                        while( result < 12 )
+                        {
+                            /* If parsed value exists in pMonthNames, assign
+                             * numerical representation. */
+                            if( strncmp( pMonthNames[ result++ ], &pDate[ readLoc ], lenToRead ) == 0 )
+                            {
+                                pDateElements->tm_mon = result;
+                                readLoc += lenToRead;
+                                count++;
+                                break;
+                            }
+                        }
+                    }
+
+                    break;
+
+                case 'D':
+                    pDateElements->tm_mday = result;
+                    count += ( result != -1 ) ? 1 : 0;
+                    break;
+
+                case 'h':
+                    pDateElements->tm_hour = result;
+                    count += ( result != -1 ) ? 1 : 0;
+                    break;
+
+                case 'm':
+                    pDateElements->tm_min = result;
+                    count += ( result != -1 ) ? 1 : 0;
+                    break;
+
+                case 's':
+                    pDateElements->tm_sec = result;
+                    count += ( result != -1 ) ? 1 : 0;
+                    break;
+
+                case '*':
+                    readLoc += lenToRead;
+                    break;
+
+                default:
+                    LogError( ( "Parsing error: Unexpected character '%c' "
+                                "found in format string.",
+                                ( char ) pFormat[ ++formatIndex ] ) );
+                    break;
+            }
+        }
+        else
         {
-            LogError( ( "Invalid 'year' value parsed from date string. "
+            if( pDate[ readLoc++ ] != pFormat[ formatIndex ] )
+            {
+                LogError( ( "Parsing error: Expected character '%c', "
+                            "but received '%c'.",
+                            pFormat[ formatIndex ], pDate[ readLoc - 1 ] ) );
+                break;
+            }
+        }
+
+        formatIndex++;
+    }
+
+    return count;
+}
+
+/*-----------------------------------------------------------*/
+
+        if( ( dateInfo.tm_year < 1900 ) )
+    {
+        LogError( ( "Invalid 'year' value parsed from date string. "
                         "Expected an integer larger than 1900, received: %ld",
                         ( long int ) dateInfo.tm_year ) );
             returnStatus = SigV4InvalidParameter;
-        }
+    }
 
         if( ( dateInfo.tm_mon < 1 ) || ( dateInfo.tm_mon > 12 ) )
-        {
-            LogError( ( "Invalid 'month' value parsed from date string. "
-                        "Expected an integer between 1 and 12, received: %ld",
+    {
+        LogError( ( "Invalid 'month' value parsed from date string. "
+                    "Expected an integer between 1 and 12, received: %ld",
                         ( long int ) dateInfo.tm_mon ) );
             returnStatus = SigV4InvalidParameter;
-        }
+    }
 
         if( ( dateInfo.tm_mday < 1 ) || ( dateInfo.tm_mday > 31 ) )
         {
@@ -95,36 +255,36 @@ static SigV4Status_t formatDate( const char * pDate,
                         "Expected an integer between 1 and 31, received: %ld",
                         ( long int ) dateInfo.tm_mday ) );
             returnStatus = SigV4InvalidParameter;
-        }
+    }
 
         if( ( dateInfo.tm_hour < 0 ) || ( dateInfo.tm_hour > 23 ) )
-        {
-            LogError( ( "Invalid 'hour' value parsed from date string. "
-                        "Expected an integer between 0 and 23, received: %ld",
+    {
+        LogError( ( "Invalid 'hour' value parsed from date string. "
+                    "Expected an integer between 0 and 23, received: %ld",
                         ( long int ) dateInfo.tm_hour ) );
             returnStatus = SigV4InvalidParameter;
-        }
+    }
 
         if( ( dateInfo.tm_min < 0 ) || ( dateInfo.tm_min > 59 ) )
-        {
-            LogError( ( "Invalid 'minute' value parsed from date string. "
-                        "Expected an integer between 0 and 59, received: %ld",
+    {
+        LogError( ( "Invalid 'minute' value parsed from date string. "
+                    "Expected an integer between 0 and 59, received: %ld",
                         ( long int ) dateInfo.tm_min ) );
             returnStatus = SigV4InvalidParameter;
-        }
+    }
 
         /* C90 allows for an additional leap second corresponding to the (rare)
          * UTC adjustment. */
         if( ( dateInfo.tm_sec < 0 ) || ( dateInfo.tm_sec > 60 ) )
-        {
-            LogError( ( "Invalid 'second' value parsed from date string. "
-                        "Expected an integer between 0 and 60, received: %ld",
+    {
+        LogError( ( "Invalid 'second' value parsed from date string. "
+                    "Expected an integer between 0 and 60, received: %ld",
                         ( long int ) dateInfo.tm_sec ) );
             returnStatus = SigV4InvalidParameter;
-        }
+    }
 
         if( returnStatus != SigV4InvalidParameter )
-        {
+{
             /* Standardize month and year values for struct tm's specifications:
              *  - tm_mon = "months from January" (0-11)
              *  - tm_year = "years since 1900" */
@@ -135,18 +295,18 @@ static SigV4Status_t formatDate( const char * pDate,
             lenFormatted = strftime( pDateISO8601, SIGV4_ISO_STRING_LEN + 1, "%Y%m%dT%H%M%SZ", &dateInfo );
 
             if( lenFormatted != SIGV4_ISO_STRING_LEN )
-            {
+    {
                 LogError( ( "Failed to generate ISO 8601 date: call to strftime() for string formatting failed: "
                             "ExpectedReturnValue=%u, ActualReturnValue=%lu.",
                             SIGV4_ISO_STRING_LEN,
                             ( unsigned long ) lenFormatted ) );
                 returnStatus = SigV4ISOFormattingError;
-            }
-            else
-            {
+    }
+    else
+    {
                 returnStatus = SigV4Success;
             }
-        }
+    }
     }
 
     return returnStatus;
@@ -170,20 +330,22 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
     {
         LogError( ( "Parameter check failed: pDateISO8601 is NULL." ) );
     }
-
     /* Check that the date provided is of the expected length. */
-    else if( dateLen != SIGV4_EXPECTED_AWS_IOT_DATE_LEN )
+    else if( ( dateLen != SIGV4_EXPECTED_LEN_RFC_3339 ) &&
+             ( dateLen != SIGV4_EXPECTED_LEN_RFC_5322 ) )
     {
-        LogError( ( "Parameter check failed: dateLen must be %u.",
-                    SIGV4_EXPECTED_AWS_IOT_DATE_LEN ) );
+        LogError( ( "Parameter check failed: dateLen must be either %u or %u, "
+                    "for RFC 3339 and RFC 5322 formats, respectively.",
+                    SIGV4_EXPECTED_LEN_RFC_3339,
+                    SIGV4_EXPECTED_LEN_RFC_5322 ) );
     }
 
     /* Check that the output buffer provided is large enough for the formatted
      * string. */
-    else if( dateISO8601Len < SIGV4_ISO_STRING_LEN + 1 )
+    else if( dateISO8601Len < SIGV4_ISO_STRING_LEN )
     {
         LogError( ( "Parameter check failed: dateISO8601Len must be at least %u.",
-                    SIGV4_ISO_STRING_LEN + 1 ) );
+                    SIGV4_ISO_STRING_LEN ) );
     }
     else
     {

From 0de9696eceff29ff04b0e9c3a00d175b105a88b4 Mon Sep 17 00:00:00 2001
From: sukhmanm <sukhmanm@amazon.com>
Date: Sat, 3 Apr 2021 12:19:18 -0400
Subject: [PATCH 12/15] Validate + buffer write

---
 source/sigv4.c | 209 +++++++++++++++++++++++++++++++++++--------------
 1 file changed, 150 insertions(+), 59 deletions(-)

diff --git a/source/sigv4.c b/source/sigv4.c
index e2987477..a70f76e8 100644
--- a/source/sigv4.c
+++ b/source/sigv4.c
@@ -34,6 +34,20 @@
 
 /*-----------------------------------------------------------*/
 
+/**
+ * @brief Converts an integer value to its ASCII respresentation, and stores the
+ * result in the provided buffer.
+ *
+ * @param[in] value The value to convert to ASCII.
+ * @param[in, out] pBuffer The starting location of the buffer on input, and the
+ * ending location on output.
+ * @param[in] lenBuf Width of value to write (padded with leading 0s if
+ * necessary).
+ */
+static void intToAscii( int32_t value,
+                        char ** pBuffer,
+                        size_t lenBuf );
+
 /**
  * @brief Parses date according to format string parameter, and populates date
  * representation struct SigV4DateTime_t with its elements.
@@ -56,40 +70,58 @@ static size_t parseDate( const char * pDate,
                          size_t formatLen,
                          SigV4DateTime_t * pDateElements );
 
+/**
+ * @brief Verify date stored in a SigV4DateTime_t date representation.
+ *
+ * @param[in] pDateElements The date representation to be verified.
+ *
+ * @return #SigV4Success if successful, and #SigV4ISOFormattingError if any
+ * member of SigV4DateTime_t is invalid or represents an out-of-range date.
+ */
+static SigV4Status_t validateDateTime( SigV4DateTime_t * pDateElements );
+
 /**
  * @brief Format an ISO 8601 date, and fill the output buffer with the result.
  *
  * @param[in] pDate The date to be formatted, in RFC3339 format.
+ * @param[in] dateLen Length of pDate, the date to be formatted.
  * @param[in] pDateISO8601 The buffer to hold the ISO 8601 encoded date.
+ * @param[in] dateISO8601Len Length of pDateISO8601, the formatted date buffer.
  *
  * @return #SigV4Success if successful, and #SigV4ISOFormattingError if a
- * parsing error occurred due to an incorrectly formatted date. If pDate is
- * correctly formatted but contains an out-of-range date, #SigV4InvalidParameter
- * is returned.
+ * parsing error occurred due to an incorrectly formatted date, or if pDate
+ * contains an out-of-range date.
  */
-static SigV4Status_t formatDate( const char * pDate,
-                                 char * pDateISO8601 );
+static SigV4Status_t dateToIso8601( const char * pDate,
+                                    size_t dateLen,
+                                    char * pDateISO8601,
+                                    size_t dateISO8601Len );
 
 /*-----------------------------------------------------------*/
 
-static SigV4Status_t formatDate( const char * pDate,
-                                 char * pDateISO8601 )
+static void intToAscii( int32_t value,
+                        char ** pBuffer,
+                        size_t bufferLen )
 {
-    SigV4Status_t returnStatus = SigV4ISOFormattingError;
-    struct tm dateInfo = { 0 };
-
-    /* Parse pDate according to the input's expected string format, and populate
-     * the date struct with its components.  */
-    if( sscanf( pDate, "%4d-%2d-%2dT%2d:%2d:%2dZ",
-                &dateInfo.tm_year,
-                &dateInfo.tm_mon,
-                &dateInfo.tm_mday,
-                &dateInfo.tm_hour,
-                &dateInfo.tm_min,
-                &dateInfo.tm_sec ) != 6 )
+    int32_t currentVal = value;
+    size_t lenRemaining = bufferLen;
+
+    assert( pBuffer != NULL );
+    assert( bufferLen > 0U );
+
+    /* Write base-10 remainder in its ASCII representation, and fill any
+     * remaining width with '0' characters. */
+    while( lenRemaining-- )
     {
-        LogError( ( "Failed to generate ISO 8601 date: call to sscanf() for input parsing failed." ) );
-        returnStatus = SigV4ISOFormattingError;
+        ( *pBuffer )[ lenRemaining ] = ( currentVal % 10 ) + '0';
+        currentVal /= 10;
+    }
+
+    /* Move pointer to follow last written character. */
+    *pBuffer += bufferLen;
+}
+
+/*-----------------------------------------------------------*/
 
 static size_t parseDate( const char * pDate,
                          size_t dateLen,
@@ -233,80 +265,139 @@ static size_t parseDate( const char * pDate,
 
 /*-----------------------------------------------------------*/
 
-        if( ( dateInfo.tm_year < 1900 ) )
+static SigV4Status_t validateDateTime( SigV4DateTime_t * pDateElements )
+{
+    SigV4Status_t returnStatus = SigV4InvalidParameter;
+    int32_t daysPerMonth[] = MONTH_DAYS;
+
+    assert( pDateElements != NULL );
+
+    if( pDateElements->tm_year < YEAR_MIN )
     {
         LogError( ( "Invalid 'year' value parsed from date string. "
-                        "Expected an integer larger than 1900, received: %ld",
-                        ( long int ) dateInfo.tm_year ) );
-            returnStatus = SigV4InvalidParameter;
+                    "Expected an integer %ld or greater, received: %ld",
+                    ( long int ) YEAR_MIN,
+                    ( long int ) pDateElements->tm_year ) );
+        returnStatus = SigV4ISOFormattingError;
     }
 
-        if( ( dateInfo.tm_mon < 1 ) || ( dateInfo.tm_mon > 12 ) )
+    if( ( pDateElements->tm_mon < 1 ) || ( pDateElements->tm_mon > 12 ) )
     {
         LogError( ( "Invalid 'month' value parsed from date string. "
                     "Expected an integer between 1 and 12, received: %ld",
-                        ( long int ) dateInfo.tm_mon ) );
-            returnStatus = SigV4InvalidParameter;
+                    ( long int ) pDateElements->tm_mon ) );
+        returnStatus = SigV4ISOFormattingError;
     }
 
-        if( ( dateInfo.tm_mday < 1 ) || ( dateInfo.tm_mday > 31 ) )
+    /* Ensure that day value is within the valid range of its relevant month. */
+    else if( ( pDateElements->tm_mday < 1 ) ||
+             ( pDateElements->tm_mday > daysPerMonth[ pDateElements->tm_mon - 1 ] ) )
+    {
+        /* Check validity of a leap year date. */
+        if( ( pDateElements->tm_mon == 2 ) && ( pDateElements->tm_mday == 29 ) )
+        {
+            if( ( ( pDateElements->tm_year % 400 ) != 0 ) &&
+                ( ( ( pDateElements->tm_year % 4 ) != 0 ) ||
+                  ( ( pDateElements->tm_year % 100 ) == 0 ) ) )
+            {
+                LogError( ( "%ld is not a valid leap year.",
+                            ( long int ) pDateElements->tm_year ) );
+                returnStatus = SigV4ISOFormattingError;
+            }
+        }
+        else
         {
             LogError( ( "Invalid 'day' value parsed from date string. "
                         "Expected an integer between 1 and 31, received: %ld",
-                        ( long int ) dateInfo.tm_mday ) );
-            returnStatus = SigV4InvalidParameter;
+                        ( long int ) pDateElements->tm_mday ) );
+
+            returnStatus = SigV4ISOFormattingError;
+        }
     }
 
-        if( ( dateInfo.tm_hour < 0 ) || ( dateInfo.tm_hour > 23 ) )
+    if( ( pDateElements->tm_hour < 0 ) || ( pDateElements->tm_hour > 23 ) )
     {
         LogError( ( "Invalid 'hour' value parsed from date string. "
                     "Expected an integer between 0 and 23, received: %ld",
-                        ( long int ) dateInfo.tm_hour ) );
-            returnStatus = SigV4InvalidParameter;
+                    ( long int ) pDateElements->tm_hour ) );
+        returnStatus = SigV4ISOFormattingError;
     }
 
-        if( ( dateInfo.tm_min < 0 ) || ( dateInfo.tm_min > 59 ) )
+    if( ( pDateElements->tm_min < 0 ) || ( pDateElements->tm_min > 59 ) )
     {
         LogError( ( "Invalid 'minute' value parsed from date string. "
                     "Expected an integer between 0 and 59, received: %ld",
-                        ( long int ) dateInfo.tm_min ) );
-            returnStatus = SigV4InvalidParameter;
+                    ( long int ) pDateElements->tm_min ) );
+        returnStatus = SigV4ISOFormattingError;
     }
 
-        /* C90 allows for an additional leap second corresponding to the (rare)
-         * UTC adjustment. */
-        if( ( dateInfo.tm_sec < 0 ) || ( dateInfo.tm_sec > 60 ) )
+    /* An upper limit of 60 accounts for the occasional leap second UTC
+     * adjustment. */
+    if( ( pDateElements->tm_sec < 0 ) || ( pDateElements->tm_sec > 60 ) )
     {
         LogError( ( "Invalid 'second' value parsed from date string. "
                     "Expected an integer between 0 and 60, received: %ld",
-                        ( long int ) dateInfo.tm_sec ) );
-            returnStatus = SigV4InvalidParameter;
+                    ( long int ) pDateElements->tm_sec ) );
+        returnStatus = SigV4ISOFormattingError;
     }
 
-        if( returnStatus != SigV4InvalidParameter )
+    return ( returnStatus != SigV4ISOFormattingError ) ? SigV4Success : returnStatus;
+}
+
+/*-----------------------------------------------------------*/
+
+static SigV4Status_t dateToIso8601( const char * pDate,
+                                    size_t dateLen,
+                                    char * pDateISO8601,
+                                    size_t dateISO8601Len )
 {
-            /* Standardize month and year values for struct tm's specifications:
-             *  - tm_mon = "months from January" (0-11)
-             *  - tm_year = "years since 1900" */
-            dateInfo.tm_mon--;
-            dateInfo.tm_year -= 1900;
+    SigV4Status_t returnStatus = SigV4InvalidParameter;
+    SigV4DateTime_t date = { 0 };
+    char * pWriteLoc = pDateISO8601;
+    const char * pFormatStr = NULL;
+    size_t formatLen = 0U;
+
+    assert( pDate != NULL );
+    assert( pDateISO8601 != NULL );
+    assert( dateLen == SIGV4_EXPECTED_LEN_RFC_3339 ||
+            dateLen == SIGV4_EXPECTED_LEN_RFC_5322 );
+    assert( dateISO8601Len >= SIGV4_ISO_STRING_LEN );
 
-            /* Construct ISO 8601 string using members of populated date struct. */
-            lenFormatted = strftime( pDateISO8601, SIGV4_ISO_STRING_LEN + 1, "%Y%m%dT%H%M%SZ", &dateInfo );
+    /* Assign format string according to input type received. */
+    pFormatStr = ( dateLen == SIGV4_EXPECTED_LEN_RFC_3339 ) ?
+                 FORMAT_RFC_3339 : FORMAT_RFC_5322;
 
-            if( lenFormatted != SIGV4_ISO_STRING_LEN )
+    formatLen = ( dateLen == SIGV4_EXPECTED_LEN_RFC_3339 ) ?
+                FORMAT_RFC_3339_LEN : FORMAT_RFC_5322_LEN;
+
+    /* ISO 8601 contains 6 numerical date components requiring parsing. */
+    if( parseDate( pDate, dateLen, pFormatStr, formatLen, &date ) == 6U )
     {
-                LogError( ( "Failed to generate ISO 8601 date: call to strftime() for string formatting failed: "
-                            "ExpectedReturnValue=%u, ActualReturnValue=%lu.",
-                            SIGV4_ISO_STRING_LEN,
-                            ( unsigned long ) lenFormatted ) );
-                returnStatus = SigV4ISOFormattingError;
+        returnStatus = validateDateTime( &date );
     }
     else
     {
-                returnStatus = SigV4Success;
-            }
+        LogError( ( "Parsing Error: Date did not match expected string format." ) );
+        returnStatus = SigV4ISOFormattingError;
     }
+
+    if( returnStatus == SigV4Success )
+    {
+        /* Combine date elements into complete ASCII representation, and fill
+         * buffer with result. */
+        intToAscii( date.tm_year, &pWriteLoc, ISO_YEAR_LEN );
+        intToAscii( date.tm_mon, &pWriteLoc, ISO_NON_YEAR_LEN );
+        intToAscii( date.tm_mday, &pWriteLoc, ISO_NON_YEAR_LEN );
+        *pWriteLoc++ = 'T';
+
+        intToAscii( date.tm_hour, &pWriteLoc, ISO_NON_YEAR_LEN );
+        intToAscii( date.tm_min, &pWriteLoc, ISO_NON_YEAR_LEN );
+        intToAscii( date.tm_sec, &pWriteLoc, ISO_NON_YEAR_LEN );
+        *pWriteLoc++ = 'Z';
+
+        LogDebug( ( "Successfully formatted ISO 8601 date: \"%.*s\"",
+                    ( int ) dateISO8601Len,
+                    pDateISO8601 ) );
     }
 
     return returnStatus;
@@ -349,7 +440,7 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
     }
     else
     {
-        returnStatus = formatDate( pDate, pDateISO8601 );
+        returnStatus = dateToIso8601( pDate, dateLen, pDateISO8601, dateISO8601Len );
     }
 
     return returnStatus;

From bd5756b5101f9d7fcadb9cd997cf52c56023b4c5 Mon Sep 17 00:00:00 2001
From: sukhmanm <sukhmanm@amazon.com>
Date: Tue, 6 Apr 2021 06:08:21 -0400
Subject: [PATCH 13/15] MISRA/complexity updates

---
 source/include/sigv4_internal.h |   3 +-
 source/sigv4.c                  | 515 ++++++++++++++++++--------------
 test/unit-test/sigv4_utest.c    | 143 +++++++++
 3 files changed, 439 insertions(+), 222 deletions(-)
 create mode 100644 test/unit-test/sigv4_utest.c

diff --git a/source/include/sigv4_internal.h b/source/include/sigv4_internal.h
index 4db9d06d..02cf8bcc 100644
--- a/source/include/sigv4_internal.h
+++ b/source/include/sigv4_internal.h
@@ -35,6 +35,7 @@
  * @brief Month name abbreviations for RFC 5322 date parsing.
  */
 #define MONTH_NAMES            { "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" }
+#define MONTH_ASCII_LEN        3U
 
 /**
  * @brief Number of days in each respective month.
@@ -57,7 +58,7 @@
  */
 typedef struct SigV4DateTime
 {
-    int32_t tm_year; /**< Year (>= 1900) */
+    int32_t tm_year; /**< Year (1900 or later) */
     int32_t tm_mon;  /**< Month (1 to 12) */
     int32_t tm_mday; /**< Day of Month (1 to 28/29/20/31) */
     int32_t tm_hour; /**< Hour (0 to 23) */
diff --git a/source/sigv4.c b/source/sigv4.c
index a70f76e8..5f06eae5 100644
--- a/source/sigv4.c
+++ b/source/sigv4.c
@@ -27,7 +27,6 @@
 
 #include <assert.h>
 #include <string.h>
-#include <ctype.h>
 
 #include "sigv4.h"
 #include "sigv4_internal.h"
@@ -41,61 +40,89 @@
  * @param[in] value The value to convert to ASCII.
  * @param[in, out] pBuffer The starting location of the buffer on input, and the
  * ending location on output.
- * @param[in] lenBuf Width of value to write (padded with leading 0s if
+ * @param[in] bufferLen Width of value to write (padded with leading 0s if
  * necessary).
  */
 static void intToAscii( int32_t value,
                         char ** pBuffer,
-                        size_t lenBuf );
+                        size_t bufferLen );
 
 /**
- * @brief Parses date according to format string parameter, and populates date
- * representation struct SigV4DateTime_t with its elements.
+ * @brief Check if the date represents a valid leap year day.
  *
- * @param[in] pDate The date to be parsed.
- * @param[in] dateLen Length of pDate, the date to be formatted.
- * @param[in] pFormat The format string used to extract date pDateElements from pDate.
- * This string, among other characters, may contain specifiers of the form
- * "%LV", where L is the number of characters to be readLoc, and V is one of
- * {Y, M, D, h, m, s, *}, representing a year, month, day, hour, minute, second,
- * or skipped (un-parsed) value, respectively.
- * @param[in] formatLen Length of the format string pFormat.
- * @param[out] pDateElements The deconstructed date representation of pDate.
+ * @param[in] pDateElements The date representation to be verified.
  *
- * @return The number of format specifiers found and filled in pDateElements.
+ * @return #SigV4Success if the date corresponds to a valid leap year,
+ * #SigV4ISOFormattingError otherwise.
  */
-static size_t parseDate( const char * pDate,
-                         size_t dateLen,
-                         const char * pFormat,
-                         size_t formatLen,
-                         SigV4DateTime_t * pDateElements );
+static SigV4Status_t checkLeap( const SigV4DateTime_t * pDateElements );
 
 /**
- * @brief Verify date stored in a SigV4DateTime_t date representation.
+ * @brief Verify the date stored in a SigV4DateTime_t date representation.
  *
  * @param[in] pDateElements The date representation to be verified.
  *
- * @return #SigV4Success if successful, and #SigV4ISOFormattingError if any
- * member of SigV4DateTime_t is invalid or represents an out-of-range date.
+ * @return #SigV4Success if the date is valid, and #SigV4ISOFormattingError if
+ * any member of SigV4DateTime_t is invalid or represents an out-of-range date.
  */
-static SigV4Status_t validateDateTime( SigV4DateTime_t * pDateElements );
+static SigV4Status_t validateDateTime( const SigV4DateTime_t * pDateElements );
+
+/**
+ * @brief Append calculated integer value to the internal date representation.
+ *
+ * @param[in] formatChar The specifier identifying the struct member to fill.
+ * @param[in] result The value to assign to the specified struct member.
+ * @param[in, out] pDateElements The date representation structure to modify.
+ *
+ * @return #SigV4Success if the formatChar specifier corresponds to a
+ * SigV4DateTime_t member, #SigV4ISOFormattingError otherwise.
+ */
+static SigV4Status_t addToDate( const char formatChar,
+                                int32_t result,
+                                SigV4DateTime_t * pDateElements );
+
+/**
+ * @brief Interpret the value of the specified characters in date, based on the
+ * format specifier, and append to the internal date representation.
+ *
+ * @param[in] pDate The date to be parsed.
+ * @param[in] formatChar The format specifier used to interpret characters.
+ * @param[in] readLoc The index of pDate to read from.
+ * @param[in] lenToRead The number of characters to read.
+ * @param[in, out] pDateElements The date representation to modify.
+ *
+ * @return #SigV4Success if parsing succeeded, #SigV4ISOFormattingError if the
+ * characters read did not match the format specifier.
+ */
+static SigV4Status_t scanValue( const char * pDate,
+                                const char formatChar,
+                                size_t readLoc,
+                                size_t lenToRead,
+                                SigV4DateTime_t * pDateElements );
+
 
 /**
- * @brief Format an ISO 8601 date, and fill the output buffer with the result.
+ * @brief Parses date according to format string parameter, and populates date
+ * representation struct SigV4DateTime_t with its elements.
  *
- * @param[in] pDate The date to be formatted, in RFC3339 format.
+ * @param[in] pDate The date to be parsed.
  * @param[in] dateLen Length of pDate, the date to be formatted.
- * @param[in] pDateISO8601 The buffer to hold the ISO 8601 encoded date.
- * @param[in] dateISO8601Len Length of pDateISO8601, the formatted date buffer.
+ * @param[in] pFormat The format string used to extract date pDateElements from pDate.
+ * This string, among other characters, may contain specifiers of the form
+ * "%LV", where L is the number of characters to be readLoc, and V is one of
+ * {Y, M, D, h, m, s, *}, representing a year, month, day, hour, minute, second,
+ * or skipped (un-parsed) value, respectively.
+ * @param[in] formatLen Length of the format string pFormat.
+ * @param[out] pDateElements The deconstructed date representation of pDate.
  *
- * @return #SigV4Success if successful, and #SigV4ISOFormattingError if a
- * parsing error occurred due to an incorrectly formatted date, or if pDate
- * contains an out-of-range date.
+ * @return #SigV4Success if all format specifiers were matched successfully,
+ * #SigV4ISOFormattingError otherwise.
  */
-static SigV4Status_t dateToIso8601( const char * pDate,
-                                    size_t dateLen,
-                                    char * pDateISO8601,
-                                    size_t dateISO8601Len );
+static SigV4Status_t parseDate( const char * pDate,
+                                size_t dateLen,
+                                const char * pFormat,
+                                size_t formatLen,
+                                SigV4DateTime_t * pDateElements );
 
 /*-----------------------------------------------------------*/
 
@@ -111,9 +138,9 @@ static void intToAscii( int32_t value,
 
     /* Write base-10 remainder in its ASCII representation, and fill any
      * remaining width with '0' characters. */
-    while( lenRemaining-- )
+    while( lenRemaining-- > 0U )
     {
-        ( *pBuffer )[ lenRemaining ] = ( currentVal % 10 ) + '0';
+        ( *pBuffer )[ lenRemaining ] = ( char ) ( ( currentVal % 10 ) + '0' );
         currentVal /= 10;
     }
 
@@ -122,153 +149,37 @@ static void intToAscii( int32_t value,
 }
 
 /*-----------------------------------------------------------*/
-
-static size_t parseDate( const char * pDate,
-                         size_t dateLen,
-                         const char * pFormat,
-                         size_t formatLen,
-                         SigV4DateTime_t * pDateElements )
+static SigV4Status_t checkLeap( const SigV4DateTime_t * pDateElements )
 {
-    size_t readLoc = 0U, lenToRead = 0U, formatIndex = 0U, count = 0U;
-    int32_t result = 0;
-    char * pMonthNames[] = MONTH_NAMES;
+    SigV4Status_t returnStatus = SigV4ISOFormattingError;
 
-    assert( pDate != NULL );
-    assert( pFormat != NULL );
     assert( pDateElements != NULL );
 
-    /* Loop through format string. */
-    while( formatIndex < formatLen )
+    /* If the date represents a leap day, verify that the leap year is valid. */
+    if( ( pDateElements->tm_mon == 2 ) && ( pDateElements->tm_mday == 29 ) )
     {
-        if( pFormat[ formatIndex ] == '%' )
+        if( ( ( pDateElements->tm_year % 400 ) != 0 ) &&
+            ( ( ( pDateElements->tm_year % 4 ) != 0 ) ||
+              ( ( pDateElements->tm_year % 100 ) == 0 ) ) )
         {
-            /* '%' must be followed by a length and type specification. */
-            assert( formatIndex < formatLen - 2 );
-
-            /* Numerical value of length specifier character. */
-            lenToRead = pFormat[ ++formatIndex ] - '0';
-            result = 0;
-
-            /* Ensure read is within buffer bounds. */
-            assert( readLoc + lenToRead - 1 < dateLen );
-
-            /* Read specified characters from pDate. */
-            do
-            {
-                if( !isdigit( pDate[ readLoc ] ) )
-                {
-                    /* Month and skipped characters can be non-numeric, and are
-                     * handled by the switch statement. */
-                    if( ( pFormat[ formatIndex + 1U ] != 'M' ) &&
-                        ( pFormat[ formatIndex + 1U ] != '*' ) )
-                    {
-                        LogError( ( "Parsing Error: Expected numerical string of type '%%%d%c', "
-                                    "but received '%.*s'.",
-                                    ( int ) lenToRead,
-                                    pFormat[ formatIndex + 1U ],
-                                    ( int ) lenToRead,
-                                    &pDate[ readLoc ] ) );
-                    }
-
-                    /* Set invalid value to allow switch statement to handle
-                     * case based on specifier. */
-                    result = -1;
-                    break;
-                }
-
-                result = result * 10 + ( pDate[ readLoc++ ] - '0' );
-            } while( --lenToRead );
-
-            switch( pFormat[ ++formatIndex ] )
-            {
-                case 'Y':
-                    pDateElements->tm_year = result;
-                    count += ( result != -1 ) ? 1 : 0;
-                    break;
-
-                case 'M':
-
-                    /* Numerical month representation (ex. RFC 3339). */
-                    if( result > 0 )
-                    {
-                        pDateElements->tm_mon = result;
-                        count++;
-                    }
-                    /* Non-numerical month representation (ex. RFC 5322). */
-                    else if( lenToRead == 3U )
-                    {
-                        result = 0;
-
-                        while( result < 12 )
-                        {
-                            /* If parsed value exists in pMonthNames, assign
-                             * numerical representation. */
-                            if( strncmp( pMonthNames[ result++ ], &pDate[ readLoc ], lenToRead ) == 0 )
-                            {
-                                pDateElements->tm_mon = result;
-                                readLoc += lenToRead;
-                                count++;
-                                break;
-                            }
-                        }
-                    }
-
-                    break;
-
-                case 'D':
-                    pDateElements->tm_mday = result;
-                    count += ( result != -1 ) ? 1 : 0;
-                    break;
-
-                case 'h':
-                    pDateElements->tm_hour = result;
-                    count += ( result != -1 ) ? 1 : 0;
-                    break;
-
-                case 'm':
-                    pDateElements->tm_min = result;
-                    count += ( result != -1 ) ? 1 : 0;
-                    break;
-
-                case 's':
-                    pDateElements->tm_sec = result;
-                    count += ( result != -1 ) ? 1 : 0;
-                    break;
-
-                case '*':
-                    readLoc += lenToRead;
-                    break;
-
-                default:
-                    LogError( ( "Parsing error: Unexpected character '%c' "
-                                "found in format string.",
-                                ( char ) pFormat[ ++formatIndex ] ) );
-                    break;
-            }
+            LogError( ( "%ld is not a valid leap year.",
+                        ( long int ) pDateElements->tm_year ) );
         }
         else
         {
-            if( pDate[ readLoc++ ] != pFormat[ formatIndex ] )
-            {
-                LogError( ( "Parsing error: Expected character '%c', "
-                            "but received '%c'.",
-                            pFormat[ formatIndex ], pDate[ readLoc - 1 ] ) );
-                break;
-            }
+            returnStatus = SigV4Success;
         }
-
-        formatIndex++;
     }
 
-    return count;
+    return returnStatus;
 }
 
 /*-----------------------------------------------------------*/
 
-static SigV4Status_t validateDateTime( SigV4DateTime_t * pDateElements )
+static SigV4Status_t validateDateTime( const SigV4DateTime_t * pDateElements )
 {
     SigV4Status_t returnStatus = SigV4InvalidParameter;
-    int32_t daysPerMonth[] = MONTH_DAYS;
+    const int32_t daysPerMonth[] = MONTH_DAYS;
 
     assert( pDateElements != NULL );
 
@@ -289,29 +200,19 @@ static SigV4Status_t validateDateTime( SigV4DateTime_t * pDateElements )
         returnStatus = SigV4ISOFormattingError;
     }
 
-    /* Ensure that day value is within the valid range of its relevant month. */
-    else if( ( pDateElements->tm_mday < 1 ) ||
-             ( pDateElements->tm_mday > daysPerMonth[ pDateElements->tm_mon - 1 ] ) )
+    /* Ensure that the day of the month is valid for the relevant month. */
+    if( ( returnStatus != SigV4ISOFormattingError ) &&
+        ( ( pDateElements->tm_mday < 1 ) ||
+          ( pDateElements->tm_mday > daysPerMonth[ pDateElements->tm_mon - 1 ] ) ) )
     {
-        /* Check validity of a leap year date. */
-        if( ( pDateElements->tm_mon == 2 ) && ( pDateElements->tm_mday == 29 ) )
-        {
-            if( ( ( pDateElements->tm_year % 400 ) != 0 ) &&
-                ( ( ( pDateElements->tm_year % 4 ) != 0 ) ||
-                  ( ( pDateElements->tm_year % 100 ) == 0 ) ) )
-            {
-                LogError( ( "%ld is not a valid leap year.",
-                            ( long int ) pDateElements->tm_year ) );
-                returnStatus = SigV4ISOFormattingError;
-            }
-        }
-        else
+        /* Check if the date is a valid leap year day. */
+        returnStatus = checkLeap( pDateElements );
+
+        if( returnStatus == SigV4ISOFormattingError )
         {
             LogError( ( "Invalid 'day' value parsed from date string. "
                         "Expected an integer between 1 and 31, received: %ld",
                         ( long int ) pDateElements->tm_mday ) );
-
-            returnStatus = SigV4ISOFormattingError;
         }
     }
 
@@ -346,58 +247,194 @@ static SigV4Status_t validateDateTime( SigV4DateTime_t * pDateElements )
 
 /*-----------------------------------------------------------*/
 
-static SigV4Status_t dateToIso8601( const char * pDate,
-                                    size_t dateLen,
-                                    char * pDateISO8601,
-                                    size_t dateISO8601Len )
+static SigV4Status_t addToDate( const char formatChar,
+                                int32_t result,
+                                SigV4DateTime_t * pDateElements )
+{
+    SigV4Status_t returnStatus = SigV4Success;
+
+    assert( pDateElements != NULL );
+
+    switch( formatChar )
+    {
+        case 'Y':
+            pDateElements->tm_year = result;
+            break;
+
+        case 'M':
+            pDateElements->tm_mon = result;
+            break;
+
+        case 'D':
+            pDateElements->tm_mday = result;
+            break;
+
+        case 'h':
+            pDateElements->tm_hour = result;
+            break;
+
+        case 'm':
+            pDateElements->tm_min = result;
+            break;
+
+        case 's':
+            pDateElements->tm_sec = result;
+            break;
+
+        case '*':
+            break;
+
+        default:
+            LogError( ( "Parsing error: Unexpected character '%c' "
+                        "found in format string.",
+                        ( char ) formatChar ) );
+            returnStatus = SigV4ISOFormattingError;
+            break;
+    }
+
+    return returnStatus;
+}
+
+/*-----------------------------------------------------------*/
+
+static SigV4Status_t scanValue( const char * pDate,
+                                const char formatChar,
+                                size_t readLoc,
+                                size_t lenToRead,
+                                SigV4DateTime_t * pDateElements )
 {
     SigV4Status_t returnStatus = SigV4InvalidParameter;
-    SigV4DateTime_t date = { 0 };
-    char * pWriteLoc = pDateISO8601;
-    const char * pFormatStr = NULL;
-    size_t formatLen = 0U;
+    const char * pMonthNames[] = MONTH_NAMES;
+    const char * pLoc = pDate + readLoc;
+    size_t readLen = lenToRead;
+    int32_t result = 0;
 
     assert( pDate != NULL );
-    assert( pDateISO8601 != NULL );
-    assert( dateLen == SIGV4_EXPECTED_LEN_RFC_3339 ||
-            dateLen == SIGV4_EXPECTED_LEN_RFC_5322 );
-    assert( dateISO8601Len >= SIGV4_ISO_STRING_LEN );
+    assert( pDateElements != NULL );
 
-    /* Assign format string according to input type received. */
-    pFormatStr = ( dateLen == SIGV4_EXPECTED_LEN_RFC_3339 ) ?
-                 FORMAT_RFC_3339 : FORMAT_RFC_5322;
+    if( formatChar == '*' )
+    {
+        readLen = 0U;
+    }
 
-    formatLen = ( dateLen == SIGV4_EXPECTED_LEN_RFC_3339 ) ?
-                FORMAT_RFC_3339_LEN : FORMAT_RFC_5322_LEN;
+    /* Determine if month value is non-numeric. */
+    if( ( formatChar == 'M' ) && ( *pLoc >= 'A' ) && ( *pLoc <= 'Z' ) )
+    {
+        assert( readLen == MONTH_ASCII_LEN );
 
-    /* ISO 8601 contains 6 numerical date components requiring parsing. */
-    if( parseDate( pDate, dateLen, pFormatStr, formatLen, &date ) == 6U )
+        while( result++ < 12 )
+        {
+            /* Search month array for parsed string. */
+            if( strncmp( pMonthNames[ result - 1 ], pLoc, MONTH_ASCII_LEN ) == 0 )
+            {
+                returnStatus = SigV4Success;
+                break;
+            }
+        }
+
+        if( returnStatus != SigV4Success )
+        {
+            LogError( ( "Unable to match string '%.3s' to a month value.",
+                        pLoc ) );
+            returnStatus = SigV4ISOFormattingError;
+        }
+
+        readLen = 0U;
+    }
+
+    /* Interpret integer value of numeric representation. */
+    while( ( readLen > 0U ) && ( *pLoc >= '0' ) && ( *pLoc <= '9' ) )
     {
-        returnStatus = validateDateTime( &date );
+        result = ( result * 10 ) + ( int32_t ) ( *pLoc - '0' );
+        readLen--;
+        pLoc += 1;
     }
-    else
+
+    if( readLen != 0U )
     {
-        LogError( ( "Parsing Error: Date did not match expected string format." ) );
+        LogError( ( "Parsing Error: Expected numerical string of type '%%%d%c', "
+                    "but received '%.*s'.",
+                    ( int ) lenToRead,
+                    formatChar,
+                    ( int ) lenToRead,
+                    pLoc ) );
         returnStatus = SigV4ISOFormattingError;
     }
 
-    if( returnStatus == SigV4Success )
+    if( returnStatus != SigV4ISOFormattingError )
     {
-        /* Combine date elements into complete ASCII representation, and fill
-         * buffer with result. */
-        intToAscii( date.tm_year, &pWriteLoc, ISO_YEAR_LEN );
-        intToAscii( date.tm_mon, &pWriteLoc, ISO_NON_YEAR_LEN );
-        intToAscii( date.tm_mday, &pWriteLoc, ISO_NON_YEAR_LEN );
-        *pWriteLoc++ = 'T';
+        returnStatus = addToDate( formatChar,
+                                  result,
+                                  pDateElements );
+    }
 
-        intToAscii( date.tm_hour, &pWriteLoc, ISO_NON_YEAR_LEN );
-        intToAscii( date.tm_min, &pWriteLoc, ISO_NON_YEAR_LEN );
-        intToAscii( date.tm_sec, &pWriteLoc, ISO_NON_YEAR_LEN );
-        *pWriteLoc++ = 'Z';
+    return returnStatus;
+}
 
-        LogDebug( ( "Successfully formatted ISO 8601 date: \"%.*s\"",
-                    ( int ) dateISO8601Len,
-                    pDateISO8601 ) );
+/*-----------------------------------------------------------*/
+
+static SigV4Status_t parseDate( const char * pDate,
+                                size_t dateLen,
+                                const char * pFormat,
+                                size_t formatLen,
+                                SigV4DateTime_t * pDateElements )
+{
+    SigV4Status_t returnStatus = SigV4InvalidParameter;
+    size_t readLoc = 0U, lenToRead = 0U, formatIndex = 0U;
+
+    assert( pDate != NULL );
+    assert( pFormat != NULL );
+    assert( pDateElements != NULL );
+    ( void ) dateLen;
+
+    /* Loop through the format string. */
+    while( ( formatIndex < formatLen ) && ( returnStatus != SigV4ISOFormattingError ) )
+    {
+        if( pFormat[ formatIndex ] == '%' )
+        {
+            /* '%' must be followed by a length and type specification. */
+            assert( formatIndex < formatLen - 2 );
+            formatIndex++;
+
+            /* Numerical value of length specifier character. */
+            lenToRead = ( ( uint64_t ) pFormat[ formatIndex ] - ( uint64_t ) '0' );
+            formatIndex++;
+
+            /* Ensure read is within buffer bounds. */
+            assert( readLoc + lenToRead - 1 < dateLen );
+            returnStatus = scanValue( pDate,
+                                      pFormat[ formatIndex ],
+                                      readLoc,
+                                      lenToRead,
+                                      pDateElements );
+
+            readLoc += lenToRead;
+        }
+        else if( pDate[ readLoc ] != pFormat[ formatIndex ] )
+        {
+            LogError( ( "Parsing error: Expected character '%c', "
+                        "but received '%c'.",
+                        pFormat[ formatIndex ], pDate[ readLoc ] ) );
+            returnStatus = SigV4ISOFormattingError;
+        }
+        else
+        {
+            readLoc++;
+            LogDebug( ( "Successfully matched character '%c' found in format string.",
+                        pDate[ readLoc - 1 ] ) );
+        }
+
+        formatIndex++;
+    }
+
+    if( ( returnStatus != SigV4ISOFormattingError ) )
+    {
+        returnStatus = SigV4Success;
+    }
+    else
+    {
+        LogError( ( "Parsing Error: Date did not match expected string format." ) );
+        returnStatus = SigV4ISOFormattingError;
     }
 
     return returnStatus;
@@ -405,12 +442,17 @@ static SigV4Status_t dateToIso8601( const char * pDate,
 
 /*-----------------------------------------------------------*/
 
+
 SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
                                          size_t dateLen,
                                          char * pDateISO8601,
                                          size_t dateISO8601Len )
 {
     SigV4Status_t returnStatus = SigV4InvalidParameter;
+    SigV4DateTime_t date = { 0 };
+    char * pWriteLoc = pDateISO8601;
+    const char * pFormatStr = NULL;
+    size_t formatLen = 0U;
 
     /* Check for NULL parameters. */
     if( pDate == NULL )
@@ -440,7 +482,38 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
     }
     else
     {
-        returnStatus = dateToIso8601( pDate, dateLen, pDateISO8601, dateISO8601Len );
+        /* Assign format string according to input type received. */
+        pFormatStr = ( dateLen == SIGV4_EXPECTED_LEN_RFC_3339 ) ?
+                     ( FORMAT_RFC_3339 ) : ( FORMAT_RFC_5322 );
+
+        formatLen = ( dateLen == SIGV4_EXPECTED_LEN_RFC_3339 ) ?
+                    ( FORMAT_RFC_3339_LEN ) : ( FORMAT_RFC_5322_LEN );
+
+        returnStatus = parseDate( pDate, dateLen, pFormatStr, formatLen, &date );
+    }
+
+    if( returnStatus == SigV4Success )
+    {
+        returnStatus = validateDateTime( &date );
+    }
+
+    if( returnStatus == SigV4Success )
+    {
+        /* Combine date elements into complete ASCII representation, and fill
+         * buffer with result. */
+        intToAscii( date.tm_year, &pWriteLoc, ISO_YEAR_LEN );
+        intToAscii( date.tm_mon, &pWriteLoc, ISO_NON_YEAR_LEN );
+        intToAscii( date.tm_mday, &pWriteLoc, ISO_NON_YEAR_LEN );
+        *pWriteLoc = 'T';
+        pWriteLoc++;
+        intToAscii( date.tm_hour, &pWriteLoc, ISO_NON_YEAR_LEN );
+        intToAscii( date.tm_min, &pWriteLoc, ISO_NON_YEAR_LEN );
+        intToAscii( date.tm_sec, &pWriteLoc, ISO_NON_YEAR_LEN );
+        *pWriteLoc = 'Z';
+
+        LogDebug( ( "Successfully formatted ISO 8601 date: \"%.*s\"",
+                    ( int ) dateISO8601Len,
+                    pDateISO8601 ) );
     }
 
     return returnStatus;
diff --git a/test/unit-test/sigv4_utest.c b/test/unit-test/sigv4_utest.c
new file mode 100644
index 00000000..3ea0430f
--- /dev/null
+++ b/test/unit-test/sigv4_utest.c
@@ -0,0 +1,143 @@
+/*
+ * SigV4 Utility Library v1.0.0
+ * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <string.h>
+
+#include "unity.h"
+
+/* Include paths for public enums, structures, and macros. */
+#include "sigv4.h"
+#include "sigv4_internal.h"
+
+/* Size of valid output date buffer. */
+#define SIGV4_TEST_BUFFER_SIZE          ( 17 )
+
+/* Size of larger-than-required output date buffer. */
+#define SIGV4_TEST_BUFFER_SIZE_LONG     ( 30 )
+
+/* Size of an output date buffer of insufficient length. */
+#define SIGV4_TEST_BUFFER_SIZE_SHORT    ( 16 )
+
+/* Test valid date inputs. */
+static const char pTestDateExpected[] = "Wed, 18 Jan 2018 09:18:06 GMT"; /*"2018-01-18T09:18:06Z"; */
+static const char pTestDateLong[] = "2018-01-18T09:18:06Z00:00";
+static const char pOutputExpected[] = "20180118T091806Z";
+
+/* Test invalid date inputs. */
+static const char pTestDateShort[] = "2018-01T09:18Z";
+static const char pTestParsingFailure[] = "2018-01-18X09:18:06Z";
+static const char pTestFormatFailure[] = " 018-01-18T09:18:06Z";
+
+/* File-scoped global variables */
+static SigV4Status_t retCode = SigV4Success;
+static char testBufferValid[ SIGV4_TEST_BUFFER_SIZE ] = { 0 };
+static char testBufferLong[ SIGV4_TEST_BUFFER_SIZE_LONG ] = { 0 };
+static char testBufferShort[ SIGV4_TEST_BUFFER_SIZE_SHORT ] = { 0 };
+
+
+/* ============================ UNITY FIXTURES ============================== */
+/* Called before each test method. */
+void setUp()
+{
+}
+
+/* Called after each test method. */
+void tearDown()
+{
+    retCode = SigV4Success;
+    memset( &testBufferValid, 0, sizeof( testBufferValid ) );
+    memset( &testBufferLong, 0, sizeof( testBufferLong ) );
+    memset( &testBufferShort, 0, sizeof( testBufferShort ) );
+}
+
+/* Called at the beginning of the whole suite. */
+void suiteSetUp()
+{
+}
+
+/* Called at the end of the whole suite. */
+int suiteTearDown( int numFailures )
+{
+    return numFailures;
+}
+/* ==================== Testing SigV4_AwsIotDateToIso8601 =================== */
+
+/**
+ * @brief Test the happy path with zero-initialized and adequately sized output
+ * buffers.
+ */
+void test_SigV4_AwsIotDateToIso8601_Happy_Path()
+{
+    SigV4Status_t returnVal = SigV4Success;
+
+    returnVal = SigV4_AwsIotDateToIso8601( pTestDateExpected, SIGV4_EXPECTED_LEN_RFC_5322, testBufferValid, SIGV4_TEST_BUFFER_SIZE );
+
+    TEST_ASSERT_EQUAL( SigV4Success, returnVal );
+    TEST_ASSERT_EQUAL_STRING( pOutputExpected, testBufferValid );
+
+    /* returnVal = SigV4_AwsIotDateToIso8601( pTestDateLong, sizeof( pTestDateLong ), testBufferValid, SIGV4_TEST_BUFFER_SIZE ); */
+
+    /* TEST_ASSERT_EQUAL( SigV4Success, returnVal ); */
+    /* TEST_ASSERT_EQUAL_STRING( pOutputExpected, testBufferValid ); */
+}
+
+/**
+ * @brief Test NULL and invalid parameters, following order of else-if blocks in
+ * SigV4_AwsIotDateToIso8601().
+ */
+void test_SigV4_AwsIotDateToIso8601_Invalid_Params()
+{
+    SigV4Status_t returnVal = SigV4Success;
+
+    /* Test pDate == NULL */
+    returnVal = SigV4_AwsIotDateToIso8601( NULL, SIGV4_EXPECTED_LEN_RFC_3339, testBufferValid, SIGV4_TEST_BUFFER_SIZE );
+    TEST_ASSERT_EQUAL( SigV4InvalidParameter, returnVal );
+
+    /* Test pDateISO8601 == NULL */
+    returnVal = SigV4_AwsIotDateToIso8601( pTestDateExpected, SIGV4_EXPECTED_LEN_RFC_5322, NULL, SIGV4_TEST_BUFFER_SIZE );
+    TEST_ASSERT_EQUAL( SigV4InvalidParameter, returnVal );
+
+    /* Test dateLen < SIGV4_EXPECTED_LEN_RFC_3339 */
+    returnVal = SigV4_AwsIotDateToIso8601( pTestDateShort, sizeof( pTestDateShort ), testBufferValid, SIGV4_TEST_BUFFER_SIZE );
+    TEST_ASSERT_EQUAL( SigV4InvalidParameter, returnVal );
+
+    /* Test dateISO8601Len < SIGV4_ISO_STRING_LEN + 1 */
+    returnVal = SigV4_AwsIotDateToIso8601( pTestDateExpected, sizeof( pTestDateExpected ), testBufferShort, SIGV4_TEST_BUFFER_SIZE_SHORT );
+    TEST_ASSERT_EQUAL( SigV4InvalidParameter, returnVal );
+}
+
+/**
+ * @brief Test invalid input date formats.
+ */
+void test_SigV4_AwsIotDateToIso8601_Formatting_Error()
+{
+    SigV4Status_t returnVal = SigV4Success;
+
+    /* sscanf() failed to match input date to expected format string. */
+    returnVal = SigV4_AwsIotDateToIso8601( pTestParsingFailure, sizeof( pTestParsingFailure ) - 1U, testBufferValid, SIGV4_TEST_BUFFER_SIZE );
+    TEST_ASSERT_EQUAL( SigV4ISOFormattingError, returnVal );
+
+    /* sscanf() parsed the input successfully (by trimming extraneous
+     * spaces/zeros), feeding an invalid input to strftime(). */
+    returnVal = SigV4_AwsIotDateToIso8601( pTestFormatFailure, sizeof( pTestFormatFailure ) - 1U, testBufferValid, SIGV4_TEST_BUFFER_SIZE );
+    TEST_ASSERT_EQUAL( SigV4ISOFormattingError, returnVal );
+}

From 60b48787cee2409bea6be887171fb8a2246c1825 Mon Sep 17 00:00:00 2001
From: sukhmanm <sukhmanm@amazon.com>
Date: Tue, 6 Apr 2021 07:01:15 -0400
Subject: [PATCH 14/15] Requirement updates

---
 source/include/sigv4.h | 39 ++++++++++++++++++++++++---------------
 1 file changed, 24 insertions(+), 15 deletions(-)

diff --git a/source/include/sigv4.h b/source/include/sigv4.h
index 13c89963..d015ff08 100644
--- a/source/include/sigv4.h
+++ b/source/include/sigv4.h
@@ -394,22 +394,31 @@ SigV4Status_t SigV4_GenerateHTTPAuthorization( const SigV4Parameters_t * pParams
  * identical). For additional information on date handling, please see
  * https://docs.aws.amazon.com/general/latest/gr/sigv4-date-handling.html.
  *
- * Formatting Overview:
- * - The AWS IoT response date is of the form "YYYY-MM-DD'T'hh:mm:ss'Z'" (ex.
- *   "2018-01-18T09:18:06Z").
- * - The ISO8601-formatted date is of the form "YYYYMMDD'T'HHMMSS'Z'" (ex.
- *   "20180118T091806Z").
+ * Acceptable Input Formats:
+ * - RFC 5322 (ex. "Thu, 18 Jan 2018 09:18:06 GMT"), the preferred format in
+ *   HTTP 'Date' response headers. If using this format, the date parameter
+ *   should match "***, DD 'MMM' YYYY hh:mm:ss GMT" exactly.
+ * - RFC 3339 (ex. "2018-01-18T09:18:06Z"), found occasionally in 'Date' and
+ *   expiration headers. If using this format, the date parameter should match
+ *   "YYYY-MM-DD'T'hh:mm:ss'Z'" exactly.
  *
- * @param[in] pDate The date header (in [RFC3339
- * format](https://tools.ietf.org/html/rfc3339)), found in the HTTP response
- * returned by AWS IoT. This value should use UTC (indicated by the "Z"
- * character postfix, with no time-zone offset), and be 20 characters in length
- * (excluding the null character).
- * @param[in] dateLen The length of the pDate header value. Must be
- * #SIGV4_EXPECTED_AWS_IOT_DATE_LEN, for valid input parameters.
- * @param[out] pDateISO8601 The ISO8601 format compliant date. This buffer must
- * be large enough to hold both the ISO8601-formatted date (16 characters) and
- * the terminating null character (17 in total).
+ * Formatted Output:
+ * - The ISO8601-formatted date will be returned in the form
+ *   "YYYYMMDD'T'HHMMSS'Z'" (ex. "20180118T091806Z").
+ *
+ * @param[in] pDate The date header (in
+ * [RFC 3339](https://tools.ietf.org/html/rfc3339) or
+ * [RFC 5322](https://tools.ietf.org/html/rfc5322) formats). An acceptable date
+ * header can be found in the HTTP response returned by AWS IoT. This value
+ * should use UTC (with no time-zone offset), and be exactly 20 or 29 characters
+ * in length (excluding the null character), to comply with RFC 3339 and RFC
+ * 5322 formats, respectively.
+ * @param[in] dateLen The length of the pDate header value. Must be either
+ * #SIGV4_EXPECTED_LEN_RFC_3339 or #SIGV4_EXPECTED_LEN_RFC_5322, for valid input
+ * parameters.
+ * @param[out] pDateISO8601 The formatted ISO8601-compliant date. The date value
+ * written to this buffer will be exactly 16 characters in length, to comply
+ * with the ISO8601 standard required for SigV4 authentication.
  * @param[in] dateISO8601Len The length of buffer pDateISO8601. Must be at least
  * #SIGV4_ISO_STRING_LEN bytes, for valid input parameters.
  *

From 7fba5327f3b4a878959a5ff7452d87cadcd3223b Mon Sep 17 00:00:00 2001
From: sukhmanm <sukhmanm@amazon.com>
Date: Tue, 20 Apr 2021 14:10:04 -0400
Subject: [PATCH 15/15] Remove unit test file

---
 test/unit-test/sigv4_utest.c | 143 -----------------------------------
 1 file changed, 143 deletions(-)
 delete mode 100644 test/unit-test/sigv4_utest.c

diff --git a/test/unit-test/sigv4_utest.c b/test/unit-test/sigv4_utest.c
deleted file mode 100644
index 3ea0430f..00000000
--- a/test/unit-test/sigv4_utest.c
+++ /dev/null
@@ -1,143 +0,0 @@
-/*
- * SigV4 Utility Library v1.0.0
- * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy of
- * this software and associated documentation files (the "Software"), to deal in
- * the Software without restriction, including without limitation the rights to
- * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
- * the Software, and to permit persons to whom the Software is furnished to do so,
- * subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in all
- * copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
- * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
- * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
- * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
- * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
- */
-
-#include <string.h>
-
-#include "unity.h"
-
-/* Include paths for public enums, structures, and macros. */
-#include "sigv4.h"
-#include "sigv4_internal.h"
-
-/* Size of valid output date buffer. */
-#define SIGV4_TEST_BUFFER_SIZE          ( 17 )
-
-/* Size of larger-than-required output date buffer. */
-#define SIGV4_TEST_BUFFER_SIZE_LONG     ( 30 )
-
-/* Size of an output date buffer of insufficient length. */
-#define SIGV4_TEST_BUFFER_SIZE_SHORT    ( 16 )
-
-/* Test valid date inputs. */
-static const char pTestDateExpected[] = "Wed, 18 Jan 2018 09:18:06 GMT"; /*"2018-01-18T09:18:06Z"; */
-static const char pTestDateLong[] = "2018-01-18T09:18:06Z00:00";
-static const char pOutputExpected[] = "20180118T091806Z";
-
-/* Test invalid date inputs. */
-static const char pTestDateShort[] = "2018-01T09:18Z";
-static const char pTestParsingFailure[] = "2018-01-18X09:18:06Z";
-static const char pTestFormatFailure[] = " 018-01-18T09:18:06Z";
-
-/* File-scoped global variables */
-static SigV4Status_t retCode = SigV4Success;
-static char testBufferValid[ SIGV4_TEST_BUFFER_SIZE ] = { 0 };
-static char testBufferLong[ SIGV4_TEST_BUFFER_SIZE_LONG ] = { 0 };
-static char testBufferShort[ SIGV4_TEST_BUFFER_SIZE_SHORT ] = { 0 };
-
-
-/* ============================ UNITY FIXTURES ============================== */
-/* Called before each test method. */
-void setUp()
-{
-}
-
-/* Called after each test method. */
-void tearDown()
-{
-    retCode = SigV4Success;
-    memset( &testBufferValid, 0, sizeof( testBufferValid ) );
-    memset( &testBufferLong, 0, sizeof( testBufferLong ) );
-    memset( &testBufferShort, 0, sizeof( testBufferShort ) );
-}
-
-/* Called at the beginning of the whole suite. */
-void suiteSetUp()
-{
-}
-
-/* Called at the end of the whole suite. */
-int suiteTearDown( int numFailures )
-{
-    return numFailures;
-}
-/* ==================== Testing SigV4_AwsIotDateToIso8601 =================== */
-
-/**
- * @brief Test the happy path with zero-initialized and adequately sized output
- * buffers.
- */
-void test_SigV4_AwsIotDateToIso8601_Happy_Path()
-{
-    SigV4Status_t returnVal = SigV4Success;
-
-    returnVal = SigV4_AwsIotDateToIso8601( pTestDateExpected, SIGV4_EXPECTED_LEN_RFC_5322, testBufferValid, SIGV4_TEST_BUFFER_SIZE );
-
-    TEST_ASSERT_EQUAL( SigV4Success, returnVal );
-    TEST_ASSERT_EQUAL_STRING( pOutputExpected, testBufferValid );
-
-    /* returnVal = SigV4_AwsIotDateToIso8601( pTestDateLong, sizeof( pTestDateLong ), testBufferValid, SIGV4_TEST_BUFFER_SIZE ); */
-
-    /* TEST_ASSERT_EQUAL( SigV4Success, returnVal ); */
-    /* TEST_ASSERT_EQUAL_STRING( pOutputExpected, testBufferValid ); */
-}
-
-/**
- * @brief Test NULL and invalid parameters, following order of else-if blocks in
- * SigV4_AwsIotDateToIso8601().
- */
-void test_SigV4_AwsIotDateToIso8601_Invalid_Params()
-{
-    SigV4Status_t returnVal = SigV4Success;
-
-    /* Test pDate == NULL */
-    returnVal = SigV4_AwsIotDateToIso8601( NULL, SIGV4_EXPECTED_LEN_RFC_3339, testBufferValid, SIGV4_TEST_BUFFER_SIZE );
-    TEST_ASSERT_EQUAL( SigV4InvalidParameter, returnVal );
-
-    /* Test pDateISO8601 == NULL */
-    returnVal = SigV4_AwsIotDateToIso8601( pTestDateExpected, SIGV4_EXPECTED_LEN_RFC_5322, NULL, SIGV4_TEST_BUFFER_SIZE );
-    TEST_ASSERT_EQUAL( SigV4InvalidParameter, returnVal );
-
-    /* Test dateLen < SIGV4_EXPECTED_LEN_RFC_3339 */
-    returnVal = SigV4_AwsIotDateToIso8601( pTestDateShort, sizeof( pTestDateShort ), testBufferValid, SIGV4_TEST_BUFFER_SIZE );
-    TEST_ASSERT_EQUAL( SigV4InvalidParameter, returnVal );
-
-    /* Test dateISO8601Len < SIGV4_ISO_STRING_LEN + 1 */
-    returnVal = SigV4_AwsIotDateToIso8601( pTestDateExpected, sizeof( pTestDateExpected ), testBufferShort, SIGV4_TEST_BUFFER_SIZE_SHORT );
-    TEST_ASSERT_EQUAL( SigV4InvalidParameter, returnVal );
-}
-
-/**
- * @brief Test invalid input date formats.
- */
-void test_SigV4_AwsIotDateToIso8601_Formatting_Error()
-{
-    SigV4Status_t returnVal = SigV4Success;
-
-    /* sscanf() failed to match input date to expected format string. */
-    returnVal = SigV4_AwsIotDateToIso8601( pTestParsingFailure, sizeof( pTestParsingFailure ) - 1U, testBufferValid, SIGV4_TEST_BUFFER_SIZE );
-    TEST_ASSERT_EQUAL( SigV4ISOFormattingError, returnVal );
-
-    /* sscanf() parsed the input successfully (by trimming extraneous
-     * spaces/zeros), feeding an invalid input to strftime(). */
-    returnVal = SigV4_AwsIotDateToIso8601( pTestFormatFailure, sizeof( pTestFormatFailure ) - 1U, testBufferValid, SIGV4_TEST_BUFFER_SIZE );
-    TEST_ASSERT_EQUAL( SigV4ISOFormattingError, returnVal );
-}