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Validate + buffer write
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@sukhmanm
sukhmanm committed Apr 3, 2021
1 parent 3a7e561 commit 0de9696
Showing 1 changed file with 150 additions and 59 deletions.
209 changes: 150 additions & 59 deletions source/sigv4.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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.
Expand All @@ -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,
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -349,7 +440,7 @@ SigV4Status_t SigV4_AwsIotDateToIso8601( const char * pDate,
}
else
{
returnStatus = formatDate( pDate, pDateISO8601 );
returnStatus = dateToIso8601( pDate, dateLen, pDateISO8601, dateISO8601Len );
}

return returnStatus;
Expand Down

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