Allow some parameters to be NULL if the length is 0.

This change permits users of the ChaCha20/Poly1305 algorithms
(and the AEAD construction thereof) to pass NULL pointers for
data that they do not need, and avoids the need to provide a valid
buffer for data that is not used.

include/mbedtls/aead_chacha20_poly1305.h

@@ -124,6 +124,7 @@ int mbedtls_aead_chacha20_poly1305_starts( mbedtls_aead_chacha20_poly1305_contex
  * \param aad_len       The length (in bytes) of the AAD. The length has no
  *                      restrictions.
  * \param aad           Buffer containing the AAD.
+ *                      This pointer can be NULL if aad_len == 0.
  *
  * \return              MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA is returned
  *                      if \p ctx or \p aad are NULL.
@@ -151,7 +152,9 @@ int mbedtls_aead_chacha20_poly1305_update_aad( mbedtls_aead_chacha20_poly1305_co
  * \param ctx           The ChaCha20-Poly1305 context.
  * \param len           The length (in bytes) of the data to encrypt or decrypt.
  * \param input         Buffer containing the data to encrypt or decrypt.
+ *                      This pointer can be NULL if len == 0.
  * \param output        Buffer to where the encrypted or decrypted data is written.
+ *                      This pointer can be NULL if len == 0.
  *
  * \return              MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA is returned
  *                      if \p ctx, \p input, or \p output are NULL.
@@ -195,9 +198,12 @@ int mbedtls_aead_chacha20_poly1305_finish( mbedtls_aead_chacha20_poly1305_contex
  *                      parameter does not matter.
  * \param aad_len       The length (in bytes) of the AAD data to process.
  * \param aad           Buffer containing the additional authenticated data (AAD).
+ *                      This pointer can be NULL if aad_len == 0.
  * \param ilen          The length (in bytes) of the data to encrypt or decrypt.
  * \param input         Buffer containing the data to encrypt or decrypt.
+ *                      This pointer can be NULL if ilen == 0.
  * \param output        Buffer to where the encrypted or decrypted data is written.
+ *                      This pointer can be NULL if ilen == 0.
  * \param mac           Buffer to where the computed 128-bit (16 bytes) MAC is written.
  *
  * \return              MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA is returned

include/mbedtls/chacha20.h

@@ -136,7 +136,9 @@ int mbedtls_chacha20_keystream_block( const mbedtls_chacha20_context *ctx,
  * \param ctx       The ChaCha20 context.
  * \param size      The length (in bytes) to process. This can have any length.
  * \param input     Buffer containing the input data.
+ *                  This pointer can be NULL if size == 0.
  * \param output    Buffer containing the output data.
+ *                  This pointer can be NULL if size == 0.
  *
  * \return          MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA if the ctx, input, or
  *                  output pointers are NULL.

include/mbedtls/poly1305.h

@@ -85,6 +85,7 @@ int mbedtls_poly1305_setkey( mbedtls_poly1305_context *ctx,
  * \param ctx           The Poly1305 context.
  * \param ilen          The input length (in bytes). Any value is accepted.
  * \param input         Buffer containing the input data to Process.
+ *                      This pointer can be NULL if ilen == 0.
  *
  * \return              MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA is returned if ctx
  *                      or input are NULL.

library/aead_chacha20_poly1305.c

@@ -174,10 +174,15 @@ int mbedtls_aead_chacha20_poly1305_update_aad( mbedtls_aead_chacha20_poly1305_co
                                                size_t aad_len,
                                                const unsigned char *aad )
 {
-    if ( ( ctx == NULL ) || ( aad == NULL ) )
+    if ( ctx == NULL )
     {
         return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA );
     }
+    else if ( ( aad_len > 0U ) && ( aad == NULL ) )
+    {
+        /* aad pointer is allowed to be NULL if aad_len == 0 */
+        return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA );
+    }
     else if ( ctx->state != AEAD_CHACHA20_POLY1305_STATE_AAD )
     {
         return (MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_STATE );
@@ -197,6 +202,11 @@ int mbedtls_aead_chacha20_poly1305_update( mbedtls_aead_chacha20_poly1305_contex
     {
         return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA );
     }
+    else if ( ( len > 0U ) && ( ( input == NULL ) || ( output == NULL ) ) )
+    {
+        /* input and output pointers are allowed to be NULL if len == 0 */
+        return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA );
+    }
     else if ( ( ctx->state != AEAD_CHACHA20_POLY1305_STATE_AAD ) &&
               ( ctx->state != AEAD_CHACHA20_POLY1305_STATE_CIPHERTEXT ) )
     {

library/chacha20.c

@@ -291,10 +291,15 @@ int mbedtls_chacha20_update( mbedtls_chacha20_context *ctx,
     size_t offset = 0U;
     size_t i;
 
-    if ( ( ctx == NULL ) || ( input == NULL ) || ( output == NULL ) )
+    if ( ctx == NULL )
     {
         return( MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA );
     }
+    else if ( ( size > 0U ) && ( ( input == NULL ) || ( output == NULL ) ) )
+    {
+        /* input and output pointers are allowed to be NULL only if size == 0 */
+        return( MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA );
+    }
 
     /* Use leftover keystream bytes, if available */
     while ( ( size > 0U ) && ( ctx->keystream_bytes_used < CHACHA20_BLOCK_SIZE_BYTES ) )

library/poly1305.c

@@ -293,12 +293,17 @@ int mbedtls_poly1305_update( mbedtls_poly1305_context *ctx,
     size_t queue_free_len;
     size_t nblocks;
 
-    if ( ( ctx == NULL ) || ( input == NULL ) )
+    if ( ctx == NULL )
     {
         return( MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
     }
+    else if ( ( ilen > 0U ) && ( input == NULL ) )
+    {
+        /* input pointer is allowed to be NULL only if ilen == 0 */
+        return( MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
+    }
 
-    if ( ctx->queue_len > 0U )
+    if ( ( remaining > 0U ) && ( ctx->queue_len > 0U ) )
     {
         queue_free_len = ( POLY1305_BLOCK_SIZE_BYTES - ctx->queue_len );