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Check architectural bound for max record payload len in one place

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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().
This commit is contained in:
Hanno Becker 2019-07-09 17:30:02 +01:00
parent 3be264e2c3
commit d96e10bf23
1 changed files with 10 additions and 37 deletions
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47
library/ssl_tls.c
View file

@ -5025,43 +5025,13 @@ static int ssl_parse_record_header( mbedtls_ssl_context *ssl )
/* 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 @@ static int ssl_prepare_record_content( mbedtls_ssl_context *ssl )
}
#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 @@ static int ssl_prepare_record_content( mbedtls_ssl_context *ssl )
}
#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 );
}