Check architectural bound for max record payload len in one place
The previous code performed architectural maximum record length checks
both before and after record decryption. Since MBEDTLS_SSL_IN_CONTENT_LEN
bounds the maximum length of the record plaintext, it suffices to check
only once after (potential) decryption.
This must not be confused with the internal check that the record
length is small enough to make the record fit into the internal input
buffer; this is done in mbedtls_ssl_fetch_input().
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 5f81939..9682bbb 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -5025,43 +5025,13 @@
/* Check length against bounds of the current transform and version */
- if( ssl->transform_in == NULL )
- {
- if( ssl->in_msglen > MBEDTLS_SSL_IN_CONTENT_LEN )
- {
- MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
- return( MBEDTLS_ERR_SSL_INVALID_RECORD );
- }
- }
- else
+ if( ssl->transform_in != NULL )
{
if( ssl->in_msglen < ssl->transform_in->minlen )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
return( MBEDTLS_ERR_SSL_INVALID_RECORD );
}
-
-#if defined(MBEDTLS_SSL_PROTO_SSL3)
- if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_0 &&
- ssl->in_msglen > ssl->transform_in->minlen + MBEDTLS_SSL_IN_CONTENT_LEN )
- {
- MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
- return( MBEDTLS_ERR_SSL_INVALID_RECORD );
- }
-#endif
-#if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1) || \
- defined(MBEDTLS_SSL_PROTO_TLS1_2)
- /*
- * TLS encrypted messages can have up to 256 bytes of padding
- */
- if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_1 &&
- ssl->in_msglen > ssl->transform_in->minlen +
- MBEDTLS_SSL_IN_CONTENT_LEN + 256 )
- {
- MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
- return( MBEDTLS_ERR_SSL_INVALID_RECORD );
- }
-#endif
}
return( 0 );
@@ -5166,12 +5136,7 @@
}
#endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */
- if( ssl->in_msglen > MBEDTLS_SSL_IN_CONTENT_LEN )
- {
- MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
- return( MBEDTLS_ERR_SSL_INVALID_RECORD );
- }
- else if( ssl->in_msglen == 0 )
+ if( ssl->in_msglen == 0 )
{
#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_3
@@ -5244,6 +5209,14 @@
}
#endif
+ /* Check actual (decrypted) record content length against
+ * configured maximum. */
+ if( ssl->in_msglen > MBEDTLS_SSL_IN_CONTENT_LEN )
+ {
+ MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
+ return( MBEDTLS_ERR_SSL_INVALID_RECORD );
+ }
+
return( 0 );
}