From 8ffc92a1e8f376820c6870a025495525125693f3 Mon Sep 17 00:00:00 2001
From: k-stachowiak <krzysiek.stachowiak@gmail.com>
Date: Wed, 12 Dec 2018 14:21:59 +0100
Subject: [PATCH 1/6] Add parameter validation for the GCM module

---
 include/mbedtls/gcm.h                 |  87 +++++++++-----
 library/gcm.c                         |  46 +++++++-
 tests/CMakeLists.txt                  |   1 +
 tests/suites/helpers.function         |   1 -
 tests/suites/test_suite_gcm.function  | 160 ++++++++++++++++++++++++++
 tests/suites/test_suite_gcm.misc.data |   2 +
 6 files changed, 263 insertions(+), 34 deletions(-)
 create mode 100644 tests/suites/test_suite_gcm.misc.data

diff --git a/include/mbedtls/gcm.h b/include/mbedtls/gcm.h
index 93d15ee80..f68643d10 100644
--- a/include/mbedtls/gcm.h
+++ b/include/mbedtls/gcm.h
@@ -85,7 +85,7 @@ mbedtls_gcm_context;
  *                  cipher, nor set the key. For this purpose, use
  *                  mbedtls_gcm_setkey().
  *
- * \param ctx       The GCM context to initialize.
+ * \param ctx       The GCM context to initialize. This must not be \c NULL.
  */
 void mbedtls_gcm_init( mbedtls_gcm_context *ctx );
 
@@ -93,9 +93,10 @@ void mbedtls_gcm_init( mbedtls_gcm_context *ctx );
  * \brief           This function associates a GCM context with a
  *                  cipher algorithm and a key.
  *
- * \param ctx       The GCM context to initialize.
+ * \param ctx       The GCM context. This must be initialized.
  * \param cipher    The 128-bit block cipher to use.
- * \param key       The encryption key.
+ * \param key       The encryption key. This must be a readable buffer of at
+ *                  least \p keybits bits.
  * \param keybits   The key size in bits. Valid options are:
  *                  <ul><li>128 bits</li>
  *                  <li>192 bits</li>
@@ -122,7 +123,8 @@ int mbedtls_gcm_setkey( mbedtls_gcm_context *ctx,
  *                  authentic. You should use this function to perform encryption
  *                  only. For decryption, use mbedtls_gcm_auth_decrypt() instead.
  *
- * \param ctx       The GCM context to use for encryption or decryption.
+ * \param ctx       The GCM context to use for encryption or decryption. This
+ *                  must be initialized.
  * \param mode      The operation to perform:
  *                  - #MBEDTLS_GCM_ENCRYPT to perform authenticated encryption.
  *                    The ciphertext is written to \p output and the
@@ -136,21 +138,28 @@ int mbedtls_gcm_setkey( mbedtls_gcm_context *ctx,
  *                    calling this function in decryption mode.
  * \param length    The length of the input data, which is equal to the length
  *                  of the output data.
- * \param iv        The initialization vector.
+ * \param iv        The initialization vector. This must be a readable buffer of
+ *                  at least \p iv_len Bytes.
  * \param iv_len    The length of the IV.
- * \param add       The buffer holding the additional data.
+ * \param add       The buffer holding the additional data. If \p add_len is
+ *                  greater than zero, this must be of at least that size in
+ *                  Bytes.
  * \param add_len   The length of the additional data.
- * \param input     The buffer holding the input data. Its size is \b length.
- * \param output    The buffer for holding the output data. It must have room
- *                  for \b length bytes.
+ * \param input     The buffer holding the input data. If \p length is greater
+ *                  than zero, this must be a readable buffer of at least that
+ *                  size in Bytes.
+ * \param output    The buffer for holding the output data. If \p length is greater
+ *                  than zero, this must be a writable buffer of at least that
+ *                  size in Bytes.
  * \param tag_len   The length of the tag to generate.
- * \param tag       The buffer for holding the tag.
+ * \param tag       The buffer for holding the tag. This must be a readable
+ *                  buffer of at least \p tag_len Bytes.
  *
  * \return          \c 0 if the encryption or decryption was performed
  *                  successfully. Note that in #MBEDTLS_GCM_DECRYPT mode,
  *                  this does not indicate that the data is authentic.
- * \return          #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths are not valid or
- *                  a cipher-specific error code if the encryption
+ * \return          #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths or pointers are
+ *                  not valid or a cipher-specific error code if the encryption
  *                  or decryption failed.
  */
 int mbedtls_gcm_crypt_and_tag( mbedtls_gcm_context *ctx,
@@ -173,23 +182,31 @@ int mbedtls_gcm_crypt_and_tag( mbedtls_gcm_context *ctx,
  *                  input buffer. If the buffers overlap, the output buffer
  *                  must trail at least 8 Bytes behind the input buffer.
  *
- * \param ctx       The GCM context.
+ * \param ctx       The GCM context. This must be initialized.
  * \param length    The length of the ciphertext to decrypt, which is also
  *                  the length of the decrypted plaintext.
- * \param iv        The initialization vector.
+ * \param iv        The initialization vector. This must be a readable buffer
+ *                  of at least \p iv_len Bytes.
  * \param iv_len    The length of the IV.
- * \param add       The buffer holding the additional data.
+ * \param add       The buffer holding the additional data. If \p add_len is
+ *                  greater than zero, this must be of at least that size in
+ *                  Bytes.
  * \param add_len   The length of the additional data.
- * \param tag       The buffer holding the tag to verify.
+ * \param tag       The buffer holding the tag to verify. This must be a
+ *                  readable buffer of at least \p tag_len Bytes.
  * \param tag_len   The length of the tag to verify.
- * \param input     The buffer holding the ciphertext. Its size is \b length.
- * \param output    The buffer for holding the decrypted plaintext. It must
- *                  have room for \b length bytes.
+ * \param input     The buffer holding the ciphertext. If \p length is greater
+ *                  than zero, this must be a readable buffer of at least that
+ *                  size.
+ * \param output    The buffer for holding the decrypted plaintext. If \p length
+ *                  is greater than zero, this must be a writable buffer of at
+ *                  least that size.
  *
  * \return          \c 0 if successful and authenticated.
  * \return          #MBEDTLS_ERR_GCM_AUTH_FAILED if the tag does not match.
- * \return          #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths are not valid or
- *                  a cipher-specific error code if the decryption failed.
+ * \return          #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths or pointers are
+ *                  not valid or a cipher-specific error code if the decryption
+ *                  failed.
  */
 int mbedtls_gcm_auth_decrypt( mbedtls_gcm_context *ctx,
                       size_t length,
@@ -206,15 +223,16 @@ int mbedtls_gcm_auth_decrypt( mbedtls_gcm_context *ctx,
  * \brief           This function starts a GCM encryption or decryption
  *                  operation.
  *
- * \param ctx       The GCM context.
+ * \param ctx       The GCM context. This must be initialized.
  * \param mode      The operation to perform: #MBEDTLS_GCM_ENCRYPT or
  *                  #MBEDTLS_GCM_DECRYPT.
- * \param iv        The initialization vector.
+ * \param iv        The initialization vector. This must be a readable buffer of
+ *                  at least \p iv_len Bytes.
  * \param iv_len    The length of the IV.
  * \param add       The buffer holding the additional data, or NULL
  *                  if \p add_len is 0.
  * \param add_len   The length of the additional data. If 0,
- *                  \p add is NULL.
+ *                  \p add may be NULL.
  *
  * \return          \c 0 on success.
  */
@@ -237,11 +255,15 @@ int mbedtls_gcm_starts( mbedtls_gcm_context *ctx,
  *                  input buffer. If the buffers overlap, the output buffer
  *                  must trail at least 8 Bytes behind the input buffer.
  *
- * \param ctx       The GCM context.
+ * \param ctx       The GCM context. This must be initialized.
  * \param length    The length of the input data. This must be a multiple of
  *                  16 except in the last call before mbedtls_gcm_finish().
- * \param input     The buffer holding the input data.
- * \param output    The buffer for holding the output data.
+ * \param input     The buffer holding the input data. If \p length is greater
+ *                  than zero, this must be a readable buffer of at least that
+ *                  size in Bytes.
+ * \param output    The buffer for holding the output data. If \p length is
+ *                  greater than zero, this must be a writable buffer of at
+ *                  least that size in Bytes.
  *
  * \return         \c 0 on success.
  * \return         #MBEDTLS_ERR_GCM_BAD_INPUT on failure.
@@ -258,9 +280,11 @@ int mbedtls_gcm_update( mbedtls_gcm_context *ctx,
  *                  It wraps up the GCM stream, and generates the
  *                  tag. The tag can have a maximum length of 16 Bytes.
  *
- * \param ctx       The GCM context.
- * \param tag       The buffer for holding the tag.
- * \param tag_len   The length of the tag to generate. Must be at least four.
+ * \param ctx       The GCM context. This must be initialized.
+ * \param tag       The buffer for holding the tag. This must be a readable
+ *                  buffer of at least \p tag_len Bytes.
+ * \param tag_len   The length of the tag to generate. This must be at least
+ *                  four.
  *
  * \return          \c 0 on success.
  * \return          #MBEDTLS_ERR_GCM_BAD_INPUT on failure.
@@ -273,7 +297,8 @@ int mbedtls_gcm_finish( mbedtls_gcm_context *ctx,
  * \brief           This function clears a GCM context and the underlying
  *                  cipher sub-context.
  *
- * \param ctx       The GCM context to clear.
+ * \param ctx       The GCM context to clear. If this is \c NULL, the call has
+ *                  no effect.
  */
 void mbedtls_gcm_free( mbedtls_gcm_context *ctx );
 
diff --git a/library/gcm.c b/library/gcm.c
index c486ef765..3e41eda9d 100644
--- a/library/gcm.c
+++ b/library/gcm.c
@@ -57,6 +57,12 @@
 
 #if !defined(MBEDTLS_GCM_ALT)
 
+/* Parameter validation macros */
+#define GCM_VALIDATE_RET( cond ) \
+    MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_GCM_BAD_INPUT )
+#define GCM_VALIDATE( cond ) \
+    MBEDTLS_INTERNAL_VALIDATE( cond )
+
 /*
  * 32-bit integer manipulation macros (big endian)
  */
@@ -85,6 +91,7 @@
  */
 void mbedtls_gcm_init( mbedtls_gcm_context *ctx )
 {
+    GCM_VALIDATE( ctx != NULL );
     memset( ctx, 0, sizeof( mbedtls_gcm_context ) );
 }
 
@@ -164,6 +171,10 @@ int mbedtls_gcm_setkey( mbedtls_gcm_context *ctx,
     int ret;
     const mbedtls_cipher_info_t *cipher_info;
 
+    GCM_VALIDATE_RET( ctx != NULL );
+    GCM_VALIDATE_RET( key != NULL );
+    GCM_VALIDATE_RET( keybits == 128 || keybits == 192 || keybits == 256 );
+
     cipher_info = mbedtls_cipher_info_from_values( cipher, keybits, MBEDTLS_MODE_ECB );
     if( cipher_info == NULL )
         return( MBEDTLS_ERR_GCM_BAD_INPUT );
@@ -274,6 +285,10 @@ int mbedtls_gcm_starts( mbedtls_gcm_context *ctx,
     const unsigned char *p;
     size_t use_len, olen = 0;
 
+    GCM_VALIDATE_RET( ctx != NULL );
+    GCM_VALIDATE_RET( iv != NULL );
+    GCM_VALIDATE_RET( add_len == 0 || add != NULL );
+
     /* IV and AD are limited to 2^64 bits, so 2^61 bytes */
     /* IV is not allowed to be zero length */
     if( iv_len == 0 ||
@@ -356,6 +371,10 @@ int mbedtls_gcm_update( mbedtls_gcm_context *ctx,
     unsigned char *out_p = output;
     size_t use_len, olen = 0;
 
+    GCM_VALIDATE_RET( ctx != NULL );
+    GCM_VALIDATE_RET( length == 0 || input != NULL );
+    GCM_VALIDATE_RET( length == 0 || output != NULL );
+
     if( output > input && (size_t) ( output - input ) < length )
         return( MBEDTLS_ERR_GCM_BAD_INPUT );
 
@@ -409,8 +428,14 @@ int mbedtls_gcm_finish( mbedtls_gcm_context *ctx,
 {
     unsigned char work_buf[16];
     size_t i;
-    uint64_t orig_len = ctx->len * 8;
-    uint64_t orig_add_len = ctx->add_len * 8;
+    uint64_t orig_len;
+    uint64_t orig_add_len;
+
+    GCM_VALIDATE_RET( ctx != NULL );
+    GCM_VALIDATE_RET( tag != NULL );
+
+    orig_len = ctx->len * 8;
+    orig_add_len = ctx->add_len * 8;
 
     if( tag_len > 16 || tag_len < 4 )
         return( MBEDTLS_ERR_GCM_BAD_INPUT );
@@ -452,6 +477,13 @@ int mbedtls_gcm_crypt_and_tag( mbedtls_gcm_context *ctx,
 {
     int ret;
 
+    GCM_VALIDATE_RET( ctx != NULL );
+    GCM_VALIDATE_RET( iv != NULL );
+    GCM_VALIDATE_RET( add_len == 0 || add != NULL );
+    GCM_VALIDATE_RET( length == 0 || input != NULL );
+    GCM_VALIDATE_RET( length == 0 || output != NULL );
+    GCM_VALIDATE_RET( tag != NULL );
+
     if( ( ret = mbedtls_gcm_starts( ctx, mode, iv, iv_len, add, add_len ) ) != 0 )
         return( ret );
 
@@ -480,6 +512,13 @@ int mbedtls_gcm_auth_decrypt( mbedtls_gcm_context *ctx,
     size_t i;
     int diff;
 
+    GCM_VALIDATE_RET( ctx != NULL );
+    GCM_VALIDATE_RET( iv != NULL );
+    GCM_VALIDATE_RET( add_len == 0 || add != NULL );
+    GCM_VALIDATE_RET( tag != NULL );
+    GCM_VALIDATE_RET( length == 0 || input != NULL );
+    GCM_VALIDATE_RET( length == 0 || output != NULL );
+
     if( ( ret = mbedtls_gcm_crypt_and_tag( ctx, MBEDTLS_GCM_DECRYPT, length,
                                    iv, iv_len, add, add_len,
                                    input, output, tag_len, check_tag ) ) != 0 )
@@ -502,6 +541,9 @@ int mbedtls_gcm_auth_decrypt( mbedtls_gcm_context *ctx,
 
 void mbedtls_gcm_free( mbedtls_gcm_context *ctx )
 {
+    if( ctx == NULL ) {
+        return;
+    }
     mbedtls_cipher_free( &ctx->cipher_ctx );
     mbedtls_platform_zeroize( ctx, sizeof( mbedtls_gcm_context ) );
 }
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 58126bedc..9e15249ea 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -92,6 +92,7 @@ add_test_suite(gcm gcm.aes128_de)
 add_test_suite(gcm gcm.aes192_de)
 add_test_suite(gcm gcm.aes256_de)
 add_test_suite(gcm gcm.camellia)
+add_test_suite(gcm gcm.misc)
 add_test_suite(hkdf)
 add_test_suite(hmac_drbg hmac_drbg.misc)
 add_test_suite(hmac_drbg hmac_drbg.no_reseed)
diff --git a/tests/suites/helpers.function b/tests/suites/helpers.function
index 3aa5cd6d0..2e227f02c 100644
--- a/tests/suites/helpers.function
+++ b/tests/suites/helpers.function
@@ -632,4 +632,3 @@ int hexcmp( uint8_t * a, uint8_t * b, uint32_t a_len, uint32_t b_len )
     }
     return ret;
 }
-
diff --git a/tests/suites/test_suite_gcm.function b/tests/suites/test_suite_gcm.function
index 4d3bba161..434d42e81 100644
--- a/tests/suites/test_suite_gcm.function
+++ b/tests/suites/test_suite_gcm.function
@@ -103,6 +103,166 @@ exit:
 }
 /* END_CASE */
 
+/* BEGIN_CASE depends_on:MBEDTLS_CHECK_PARAMS:!MBEDTLS_PARAM_FAILED_ALT */
+void gcm_invalid_param( )
+{
+    mbedtls_gcm_context ctx;
+    unsigned char valid_buffer[] = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06 };
+    mbedtls_cipher_id_t valid_cipher = MBEDTLS_CIPHER_ID_AES;
+    int valid_mode = MBEDTLS_GCM_ENCRYPT;
+    int valid_len = sizeof(valid_buffer);
+    int valid_bitlen = 128, invalid_bitlen = 1;
+
+    mbedtls_gcm_init( &ctx );
+
+    /* mbedtls_gcm_init() */
+    TEST_INVALID_PARAM( mbedtls_gcm_init( NULL ) );
+
+    /* mbedtls_gcm_setkey */
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_setkey( NULL, valid_cipher, valid_buffer, valid_bitlen ) );
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_setkey( &ctx, valid_cipher, NULL, valid_bitlen ) );
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_setkey( &ctx, valid_cipher, valid_buffer, invalid_bitlen ) );
+
+    /* mbedtls_gcm_crypt_and_tag() */
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_crypt_and_tag( NULL, valid_mode, valid_len,
+                                   valid_buffer, valid_len,
+                                   valid_buffer, valid_len,
+                                   valid_buffer, valid_buffer,
+                                   valid_len, valid_buffer ) );
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_crypt_and_tag( &ctx, valid_mode, valid_len,
+                                   NULL, valid_len,
+                                   valid_buffer, valid_len,
+                                   valid_buffer, valid_buffer,
+                                   valid_len, valid_buffer ) );
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_crypt_and_tag( &ctx, valid_mode, valid_len,
+                                   valid_buffer, valid_len,
+                                   NULL, valid_len,
+                                   valid_buffer, valid_buffer,
+                                   valid_len, valid_buffer ) );
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_crypt_and_tag( &ctx, valid_mode, valid_len,
+                                   valid_buffer, valid_len,
+                                   valid_buffer, valid_len,
+                                   NULL, valid_buffer,
+                                   valid_len, valid_buffer ) );
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_crypt_and_tag( &ctx, valid_mode, valid_len,
+                                   valid_buffer, valid_len,
+                                   valid_buffer, valid_len,
+                                   valid_buffer, NULL,
+                                   valid_len, valid_buffer ) );
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_crypt_and_tag( &ctx, valid_mode, valid_len,
+                                   valid_buffer, valid_len,
+                                   valid_buffer, valid_len,
+                                   valid_buffer, valid_buffer,
+                                   valid_len, NULL ) );
+
+    /* mbedtls_gcm_auth_decrypt() */
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_auth_decrypt( NULL, valid_len,
+                                  valid_buffer, valid_len,
+                                  valid_buffer, valid_len,
+                                  valid_buffer, valid_len,
+                                  valid_buffer, valid_buffer) );
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_auth_decrypt( &ctx, valid_len,
+                                  NULL, valid_len,
+                                  valid_buffer, valid_len,
+                                  valid_buffer, valid_len,
+                                  valid_buffer, valid_buffer) );
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_auth_decrypt( &ctx, valid_len,
+                                  valid_buffer, valid_len,
+                                  NULL, valid_len,
+                                  valid_buffer, valid_len,
+                                  valid_buffer, valid_buffer) );
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_auth_decrypt( &ctx, valid_len,
+                                  valid_buffer, valid_len,
+                                  valid_buffer, valid_len,
+                                  NULL, valid_len,
+                                  valid_buffer, valid_buffer) );
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_auth_decrypt( &ctx, valid_len,
+                                  valid_buffer, valid_len,
+                                  valid_buffer, valid_len,
+                                  valid_buffer, valid_len,
+                                  NULL, valid_buffer) );
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_auth_decrypt( &ctx, valid_len,
+                                  valid_buffer, valid_len,
+                                  valid_buffer, valid_len,
+                                  valid_buffer, valid_len,
+                                  valid_buffer, NULL) );
+
+    /* mbedtls_gcm_starts() */
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_starts( NULL, valid_mode,
+                            valid_buffer, valid_len,
+                            valid_buffer, valid_len ) );
+
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_starts( &ctx, valid_mode,
+                            NULL, valid_len,
+                            valid_buffer, valid_len ) );
+
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_starts( &ctx, valid_mode,
+                            valid_buffer, valid_len,
+                            NULL, valid_len ) );
+
+    /* mbedtls_gcm_update() */
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_update( NULL, valid_len,
+                            valid_buffer, valid_buffer ) );
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_update( &ctx, valid_len,
+                            NULL, valid_buffer ) );
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_update( &ctx, valid_len,
+                            valid_buffer, NULL ) );
+
+    /* mbedtls_gcm_finish() */
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_finish( NULL, valid_buffer, valid_len ) );
+    TEST_INVALID_PARAM_RET(
+        MBEDTLS_ERR_GCM_BAD_INPUT,
+        mbedtls_gcm_finish( &ctx, NULL, valid_len ) );
+
+exit:
+    mbedtls_gcm_free( &ctx );
+}
+/* END_CASE */
+
 /* BEGIN_CASE depends_on:MBEDTLS_SELF_TEST */
 void gcm_selftest(  )
 {
diff --git a/tests/suites/test_suite_gcm.misc.data b/tests/suites/test_suite_gcm.misc.data
new file mode 100644
index 000000000..f22b7a3b7
--- /dev/null
+++ b/tests/suites/test_suite_gcm.misc.data
@@ -0,0 +1,2 @@
+GCM - Invalid parameters
+gcm_invalid_param:

From 5fccb3edf3d63c315e010be915a2f6b263340d63 Mon Sep 17 00:00:00 2001
From: k-stachowiak <krzysiek.stachowiak@gmail.com>
Date: Wed, 12 Dec 2018 15:51:26 +0100
Subject: [PATCH 2/6] Add tests for valid NULL in gcm_free()

---
 tests/suites/test_suite_gcm.function  | 9 +++++++++
 tests/suites/test_suite_gcm.misc.data | 3 +++
 2 files changed, 12 insertions(+)

diff --git a/tests/suites/test_suite_gcm.function b/tests/suites/test_suite_gcm.function
index 434d42e81..1fcb681b9 100644
--- a/tests/suites/test_suite_gcm.function
+++ b/tests/suites/test_suite_gcm.function
@@ -263,6 +263,15 @@ exit:
 }
 /* END_CASE */
 
+/* BEGIN_CASE */
+void gcm_valid_param( )
+{
+    TEST_VALID_PARAM( mbedtls_gcm_free( NULL ) );
+exit:
+    return;
+}
+/* END_CASE */
+
 /* BEGIN_CASE depends_on:MBEDTLS_SELF_TEST */
 void gcm_selftest(  )
 {
diff --git a/tests/suites/test_suite_gcm.misc.data b/tests/suites/test_suite_gcm.misc.data
index f22b7a3b7..cf0152653 100644
--- a/tests/suites/test_suite_gcm.misc.data
+++ b/tests/suites/test_suite_gcm.misc.data
@@ -1,2 +1,5 @@
 GCM - Invalid parameters
 gcm_invalid_param:
+
+GCM - Valid parameters
+gcm_valid_param:

From 2ae7ae5301e21188b455b5b39475b8043ca30217 Mon Sep 17 00:00:00 2001
From: k-stachowiak <krzysiek.stachowiak@gmail.com>
Date: Thu, 13 Dec 2018 14:48:30 +0100
Subject: [PATCH 3/6] Doxygen comments improvement

---
 include/mbedtls/gcm.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/mbedtls/gcm.h b/include/mbedtls/gcm.h
index f68643d10..6a49c39c4 100644
--- a/include/mbedtls/gcm.h
+++ b/include/mbedtls/gcm.h
@@ -143,7 +143,7 @@ int mbedtls_gcm_setkey( mbedtls_gcm_context *ctx,
  * \param iv_len    The length of the IV.
  * \param add       The buffer holding the additional data. If \p add_len is
  *                  greater than zero, this must be of at least that size in
- *                  Bytes.
+ *                  Bytes. If `add_len == 0`, this may be \c NULL.
  * \param add_len   The length of the additional data.
  * \param input     The buffer holding the input data. If \p length is greater
  *                  than zero, this must be a readable buffer of at least that
@@ -190,7 +190,7 @@ int mbedtls_gcm_crypt_and_tag( mbedtls_gcm_context *ctx,
  * \param iv_len    The length of the IV.
  * \param add       The buffer holding the additional data. If \p add_len is
  *                  greater than zero, this must be of at least that size in
- *                  Bytes.
+ *                  Bytes. If `add_len == 0`, this may be \c NULL.
  * \param add_len   The length of the additional data.
  * \param tag       The buffer holding the tag to verify. This must be a
  *                  readable buffer of at least \p tag_len Bytes.
@@ -229,10 +229,10 @@ int mbedtls_gcm_auth_decrypt( mbedtls_gcm_context *ctx,
  * \param iv        The initialization vector. This must be a readable buffer of
  *                  at least \p iv_len Bytes.
  * \param iv_len    The length of the IV.
- * \param add       The buffer holding the additional data, or NULL
- *                  if \p add_len is 0.
- * \param add_len   The length of the additional data. If 0,
- *                  \p add may be NULL.
+ * \param add       The buffer holding the additional data, or \c NULL
+ *                  if \p add_len is \c 0.
+ * \param add_len   The length of the additional data. If \c 0,
+ *                  \p add may be \c NULL.
  *
  * \return          \c 0 on success.
  */

From 9af22e479072bedd1f50b88b26a6dca50d754c7d Mon Sep 17 00:00:00 2001
From: k-stachowiak <krzysiek.stachowiak@gmail.com>
Date: Thu, 13 Dec 2018 14:49:27 +0100
Subject: [PATCH 4/6] Update change log

---
 ChangeLog | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ChangeLog b/ChangeLog
index 0ead78009..4d7eb196f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -47,6 +47,7 @@ API Changes
      in favour a new generic error MBEDTLS_ERR_CAMELLIA_BAD_INPUT_DATA.
    * Deprecate the Blowfish error MBEDTLS_ERR_BLOWFISH_INVALID_KEY_LENGTH
      in favour of a new generic error MBEDTLS_ERR_BLOWFISH_BAD_INPUT_DATA.
+   * Add validation checks for input parameters to functions in the GCM module.
 
 New deprecations
    * Deprecate mbedtls_ctr_drbg_update and mbedtls_hmac_drbg_update

From 21298a20c4eab443694a7d34bfb1e3a5a41f01af Mon Sep 17 00:00:00 2001
From: k-stachowiak <krzysiek.stachowiak@gmail.com>
Date: Thu, 13 Dec 2018 17:11:58 +0100
Subject: [PATCH 5/6] Improve parameter validation in mbedtls_gcm_free()

---
 include/mbedtls/gcm.h | 2 +-
 library/gcm.c         | 3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/include/mbedtls/gcm.h b/include/mbedtls/gcm.h
index 6a49c39c4..cf8bed9a1 100644
--- a/include/mbedtls/gcm.h
+++ b/include/mbedtls/gcm.h
@@ -298,7 +298,7 @@ int mbedtls_gcm_finish( mbedtls_gcm_context *ctx,
  *                  cipher sub-context.
  *
  * \param ctx       The GCM context to clear. If this is \c NULL, the call has
- *                  no effect.
+ *                  no effect. Otherwise, this must be initialized.
  */
 void mbedtls_gcm_free( mbedtls_gcm_context *ctx );
 
diff --git a/library/gcm.c b/library/gcm.c
index 3e41eda9d..675926a51 100644
--- a/library/gcm.c
+++ b/library/gcm.c
@@ -541,9 +541,8 @@ int mbedtls_gcm_auth_decrypt( mbedtls_gcm_context *ctx,
 
 void mbedtls_gcm_free( mbedtls_gcm_context *ctx )
 {
-    if( ctx == NULL ) {
+    if( ctx == NULL )
         return;
-    }
     mbedtls_cipher_free( &ctx->cipher_ctx );
     mbedtls_platform_zeroize( ctx, sizeof( mbedtls_gcm_context ) );
 }

From 6009ece91d6de0b137fb5afe740aaa55ee32555d Mon Sep 17 00:00:00 2001
From: k-stachowiak <krzysiek.stachowiak@gmail.com>
Date: Wed, 19 Dec 2018 13:24:29 +0100
Subject: [PATCH 6/6] Increase strictness of NULL parameter validity in GCM's
 doxygen

---
 include/mbedtls/gcm.h | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/include/mbedtls/gcm.h b/include/mbedtls/gcm.h
index cf8bed9a1..fccabb0d9 100644
--- a/include/mbedtls/gcm.h
+++ b/include/mbedtls/gcm.h
@@ -141,9 +141,8 @@ int mbedtls_gcm_setkey( mbedtls_gcm_context *ctx,
  * \param iv        The initialization vector. This must be a readable buffer of
  *                  at least \p iv_len Bytes.
  * \param iv_len    The length of the IV.
- * \param add       The buffer holding the additional data. If \p add_len is
- *                  greater than zero, this must be of at least that size in
- *                  Bytes. If `add_len == 0`, this may be \c NULL.
+ * \param add       The buffer holding the additional data. This must be of at
+ *                  least that size in Bytes.
  * \param add_len   The length of the additional data.
  * \param input     The buffer holding the input data. If \p length is greater
  *                  than zero, this must be a readable buffer of at least that
@@ -188,9 +187,8 @@ int mbedtls_gcm_crypt_and_tag( mbedtls_gcm_context *ctx,
  * \param iv        The initialization vector. This must be a readable buffer
  *                  of at least \p iv_len Bytes.
  * \param iv_len    The length of the IV.
- * \param add       The buffer holding the additional data. If \p add_len is
- *                  greater than zero, this must be of at least that size in
- *                  Bytes. If `add_len == 0`, this may be \c NULL.
+ * \param add       The buffer holding the additional data. This must be of at
+ *                  least that size in Bytes.
  * \param add_len   The length of the additional data.
  * \param tag       The buffer holding the tag to verify. This must be a
  *                  readable buffer of at least \p tag_len Bytes.