Enable use of nullptr for 0 length plaintext/ciphertext in crypto (#1…

…0198) * Enable use of nullptr for 0 length plaintext/ciphertext in crypto * address review comments
project-chip · Nov 4, 2021 · 2f7868b · 2f7868b
1 parent 60ff8e0
commit 2f7868b
Show file tree

Hide file tree

Showing 5 changed files with 332 additions and 77 deletions.
diff --git a/src/crypto/CHIPCryptoPAL.h b/src/crypto/CHIPCryptoPAL.h
@@ -477,7 +477,9 @@ CHIP_ERROR ConvertIntegerRawToDerWithoutTag(const ByteSpan & raw_integer, Mutabl
  * @brief A function that implements AES-CCM encryption
  *
  * This implements the CHIP_Crypto_AEAD_GenerateEncrypt() cryptographic primitive
- * from the specification.
+ * from the specification. For an empty plaintext, the user of the API can provide
+ * an empty string, or a nullptr, and provide plaintext_length as 0. The output buffer,
+ * ciphertext can also be an empty string, or a nullptr for this case.
  *
  * @param plaintext Plaintext to encrypt
  * @param plaintext_length Length of plain_text
@@ -500,7 +502,9 @@ CHIP_ERROR AES_CCM_encrypt(const uint8_t * plaintext, size_t plaintext_length, c
  * @brief A function that implements AES-CCM decryption
  *
  * This implements the CHIP_Crypto_AEAD_DecryptVerify() cryptographic primitive
- * from the specification.
+ * from the specification. For an empty ciphertext, the user of the API can provide
+ * an empty string, or a nullptr, and provide ciphertext_length as 0. The output buffer,
+ * plaintext can also be an empty string, or a nullptr for this case.
  *
  * @param ciphertext Ciphertext to decrypt
  * @param ciphertext_length Length of ciphertext

diff --git a/src/crypto/CHIPCryptoPALOpenSSL.cpp b/src/crypto/CHIPCryptoPALOpenSSL.cpp
@@ -55,6 +55,8 @@ namespace Crypto {
 
 typedef struct stack_st_X509 X509_LIST;
 
+constexpr char kEmptyCryptoText[] = "";
+
 enum class DigestType
 {
     SHA256
@@ -132,6 +134,16 @@ CHIP_ERROR AES_CCM_encrypt(const uint8_t * plaintext, size_t plaintext_length, c
     int result               = 1;
     const EVP_CIPHER * type  = nullptr;
 
+    if (plaintext_length != 0)
+    {
+        VerifyOrExit(plaintext != nullptr, error = CHIP_ERROR_INVALID_ARGUMENT);
+        VerifyOrExit(ciphertext != nullptr, error = CHIP_ERROR_INVALID_ARGUMENT);
+    }
+    else if (plaintext == nullptr)
+    {
+        plaintext = Uint8::from_const_char(kEmptyCryptoText);
+    }
+
     VerifyOrExit(key != nullptr, error = CHIP_ERROR_INVALID_ARGUMENT);
     VerifyOrExit(_isValidKeyLength(key_length), error = CHIP_ERROR_INVALID_ARGUMENT);
     VerifyOrExit(iv != nullptr, error = CHIP_ERROR_INVALID_ARGUMENT);
@@ -214,6 +226,16 @@ CHIP_ERROR AES_CCM_decrypt(const uint8_t * ciphertext, size_t ciphertext_length,
     int result               = 1;
     const EVP_CIPHER * type  = nullptr;
 
+    if (ciphertext_length != 0)
+    {
+        VerifyOrExit(ciphertext != nullptr, error = CHIP_ERROR_INVALID_ARGUMENT);
+        VerifyOrExit(plaintext != nullptr, error = CHIP_ERROR_INVALID_ARGUMENT);
+    }
+    else if (ciphertext == nullptr)
+    {
+        ciphertext = Uint8::from_const_char(kEmptyCryptoText);
+    }
+
     VerifyOrExit(tag != nullptr, error = CHIP_ERROR_INVALID_ARGUMENT);
     VerifyOrExit(_isValidTagLength(tag_length), error = CHIP_ERROR_INVALID_ARGUMENT);
     VerifyOrExit(key != nullptr, error = CHIP_ERROR_INVALID_ARGUMENT);

diff --git a/src/crypto/CHIPCryptoPALmbedTLS.cpp b/src/crypto/CHIPCryptoPALmbedTLS.cpp
@@ -112,6 +112,8 @@ CHIP_ERROR AES_CCM_encrypt(const uint8_t * plaintext, size_t plaintext_length, c
     mbedtls_ccm_context context;
     mbedtls_ccm_init(&context);
 
+    VerifyOrExit(plaintext != nullptr || plaintext_length == 0, error = CHIP_ERROR_INVALID_ARGUMENT);
+    VerifyOrExit(ciphertext != nullptr || plaintext_length == 0, error = CHIP_ERROR_INVALID_ARGUMENT);
     VerifyOrExit(key != nullptr, error = CHIP_ERROR_INVALID_ARGUMENT);
     VerifyOrExit(_isValidKeyLength(key_length), error = CHIP_ERROR_UNSUPPORTED_ENCRYPTION_TYPE);
     VerifyOrExit(iv != nullptr, error = CHIP_ERROR_INVALID_ARGUMENT);
@@ -151,6 +153,8 @@ CHIP_ERROR AES_CCM_decrypt(const uint8_t * ciphertext, size_t ciphertext_len, co
     mbedtls_ccm_context context;
     mbedtls_ccm_init(&context);
 
+    VerifyOrExit(plaintext != nullptr || ciphertext_len == 0, error = CHIP_ERROR_INVALID_ARGUMENT);
+    VerifyOrExit(ciphertext != nullptr || ciphertext_len == 0, error = CHIP_ERROR_INVALID_ARGUMENT);
     VerifyOrExit(tag != nullptr, error = CHIP_ERROR_INVALID_ARGUMENT);
     VerifyOrExit(_isValidTagLength(tag_length), error = CHIP_ERROR_INVALID_ARGUMENT);
     VerifyOrExit(key != nullptr, error = CHIP_ERROR_INVALID_ARGUMENT);