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mbedtls_cipher_check_tag: zeroize expected tag on tag mismatch

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Signed-off-by: Gilles Peskine <[email protected]>
This commit is contained in:
Gilles Peskine
2021-12-13 14:15:39 +01:00
parent 1f0f42f1d1
commit 8dc7b243ae
1 changed files with 10 additions and 7 deletions
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library/cipher.c
+10 -7
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@@ -967,6 +967,12 @@ int mbedtls_cipher_check_tag( mbedtls_cipher_context_t *ctx,
return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
}
/* Status to return on a non-authenticated algorithm. It would make sense
* to return MBEDTLS_ERR_CIPHER_INVALID_CONTEXT or perhaps
* MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA, but at the time I write this our
* unit tests assume 0. */
ret = 0;
#if defined(MBEDTLS_GCM_C)
if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
{
@@ -981,9 +987,7 @@ int mbedtls_cipher_check_tag( mbedtls_cipher_context_t *ctx,
/* Check the tag in "constant-time" */
if( mbedtls_constant_time_memcmp( tag, check_tag, tag_len ) != 0 )
return( MBEDTLS_ERR_CIPHER_AUTH_FAILED );
return( 0 );
ret = MBEDTLS_ERR_CIPHER_AUTH_FAILED;
}
#endif /* MBEDTLS_GCM_C */
@@ -1003,13 +1007,12 @@ int mbedtls_cipher_check_tag( mbedtls_cipher_context_t *ctx,
/* Check the tag in "constant-time" */
if( mbedtls_constant_time_memcmp( tag, check_tag, tag_len ) != 0 )
return( MBEDTLS_ERR_CIPHER_AUTH_FAILED );
return( 0 );
ret = MBEDTLS_ERR_CIPHER_AUTH_FAILED;
}
#endif /* MBEDTLS_CHACHAPOLY_C */
return( 0 );
mbedtls_platform_zeroize( check_tag, tag_len );
return( ret );
}
#endif /* MBEDTLS_GCM_C || MBEDTLS_CHACHAPOLY_C */