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Use uniform treatment for future messages and proper HS fragments

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This commit returns the error code MBEDTLS_ERR_SSL_EARLY_MESSAGE
for proper handshake fragments, forwarding their treatment to
the buffering function ssl_buffer_message(); currently, though,
this function does not yet buffer or reassembly HS messages, so:

! This commit temporarily disables support for handshake reassembly !
This commit is contained in:
Hanno Becker 2018-08-16 13:09:04 +01:00
parent 44650b7a74
commit 6d97ef5a03
2 changed files with 6 additions and 152 deletions
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2
include/mbedtls/ssl_internal.h
View file

@ -297,8 +297,6 @@ struct mbedtls_ssl_handshake_params
unsigned char verify_cookie_len; /*!< Cli: cookie length
Srv: flag for sending a cookie */
unsigned char *hs_msg; /*!< Reassembled handshake message */
uint32_t retransmit_timeout; /*!< Current value of timeout */
unsigned char retransmit_state; /*!< Retransmission state */
mbedtls_ssl_flight_item *flight; /*!< Current outgoing flight */

156
library/ssl_tls.c
View file

@ -3558,141 +3558,6 @@ static int ssl_prepare_reassembly_buffer( mbedtls_ssl_context *ssl, /* debug */
return( 0 );
}
/*
* Reassemble fragmented DTLS handshake messages.
*
* Use a temporary buffer for reassembly, divided in two parts:
* - the first holds the reassembled message (including handshake header),
* - the second holds a bitmask indicating which parts of the message
* (excluding headers) have been received so far.
*/
static int ssl_reassemble_dtls_handshake( mbedtls_ssl_context *ssl )
{
unsigned char *msg, *bitmask;
size_t frag_len, frag_off;
size_t msg_len = ssl->in_hslen - 12; /* Without headers */
if( ssl->handshake == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "not supported outside handshake (for now)" ) );
return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
}
/*
* For first fragment, check size and allocate buffer
*/
if( ssl->handshake->hs_msg == NULL )
{
ret = ssl_prepare_reassembly_buffer( msg_len, 1,
&ssl->handshake->hs_msg );
if( ret != 0 )
return( ret );
/* Prepare final header: copy msg_type, length and message_seq,
* then add standardised fragment_offset and fragment_length */
memcpy( ssl->handshake->hs_msg, ssl->in_msg, 6 );
memset( ssl->handshake->hs_msg + 6, 0, 3 );
memcpy( ssl->handshake->hs_msg + 9,
ssl->handshake->hs_msg + 1, 3 );
}
else
{
/* Make sure msg_type and length are consistent */
if( memcmp( ssl->handshake->hs_msg, ssl->in_msg, 4 ) != 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "fragment header mismatch" ) );
return( MBEDTLS_ERR_SSL_INVALID_RECORD );
}
}
msg = ssl->handshake->hs_msg + 12;
bitmask = msg + msg_len;
/*
* Check and copy current fragment
*/
frag_off = ( ssl->in_msg[6] << 16 ) |
( ssl->in_msg[7] << 8 ) |
ssl->in_msg[8];
frag_len = ( ssl->in_msg[9] << 16 ) |
( ssl->in_msg[10] << 8 ) |
ssl->in_msg[11];
if( frag_off + frag_len > msg_len )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid fragment offset/len: %d + %d > %d",
frag_off, frag_len, msg_len ) );
return( MBEDTLS_ERR_SSL_INVALID_RECORD );
}
if( frag_len + 12 > ssl->in_msglen )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid fragment length: %d + 12 > %d",
frag_len, ssl->in_msglen ) );
return( MBEDTLS_ERR_SSL_INVALID_RECORD );
}
MBEDTLS_SSL_DEBUG_MSG( 2, ( "adding fragment, offset = %d, length = %d",
frag_off, frag_len ) );
memcpy( msg + frag_off, ssl->in_msg + 12, frag_len );
ssl_bitmask_set( bitmask, frag_off, frag_len );
/*
* Do we have the complete message by now?
* If yes, finalize it, else ask to read the next record.
*/
if( ssl_bitmask_check( bitmask, msg_len ) != 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "message is not complete yet" ) );
return( MBEDTLS_ERR_SSL_CONTINUE_PROCESSING );
}
MBEDTLS_SSL_DEBUG_MSG( 2, ( "handshake message completed" ) );
if( frag_len + 12 < ssl->in_msglen )
{
/*
* We'got more handshake messages in the same record.
* This case is not handled now because no know implementation does
* that and it's hard to test, so we prefer to fail cleanly for now.
*/
MBEDTLS_SSL_DEBUG_MSG( 1, ( "last fragment not alone in its record" ) );
return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
}
if( ssl->in_left > ssl->next_record_offset )
{
/*
* We've got more data in the buffer after the current record,
* that we don't want to overwrite. Move it before writing the
* reassembled message, and adjust in_left and next_record_offset.
*/
unsigned char *cur_remain = ssl->in_hdr + ssl->next_record_offset;
unsigned char *new_remain = ssl->in_msg + ssl->in_hslen;
size_t remain_len = ssl->in_left - ssl->next_record_offset;
/* First compute and check new lengths */
ssl->next_record_offset = new_remain - ssl->in_hdr;
ssl->in_left = ssl->next_record_offset + remain_len;
if( ssl->in_left > MBEDTLS_SSL_IN_BUFFER_LEN -
(size_t)( ssl->in_hdr - ssl->in_buf ) )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "reassembled message too large for buffer" ) );
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
}
memmove( new_remain, cur_remain, remain_len );
}
memcpy( ssl->in_msg, ssl->handshake->hs_msg, ssl->in_hslen );
MBEDTLS_SSL_DEBUG_BUF( 3, "reassembled handshake message",
ssl->in_msg, ssl->in_hslen );
return( 0 );
}
#endif /* MBEDTLS_SSL_PROTO_DTLS */
static uint32_t ssl_get_hs_total_len( mbedtls_ssl_context *ssl )
@ -3772,15 +3637,14 @@ int mbedtls_ssl_prepare_handshake_record( mbedtls_ssl_context *ssl )
}
/* Wait until message completion to increment in_msg_seq */
/* Message reassembly is handled alongside buffering of future
* messages; the commonality is that both handshake fragments and
* future messages cannot be forwarded immediately to the handshake
* handshake logic layer. */
if( ssl_hs_is_proper_fragment( ssl ) == 1 )
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "found fragmented DTLS handshake message" ) );
if( ( ret = ssl_reassemble_dtls_handshake( ssl ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "ssl_reassemble_dtls_handshake", ret );
return( ret );
}
return( MBEDTLS_ERR_SSL_EARLY_MESSAGE );
}
}
else
@ -3812,13 +3676,6 @@ void mbedtls_ssl_update_handshake_status( mbedtls_ssl_context *ssl )
unsigned offset;
mbedtls_ssl_hs_buffer *hs_buf;
/* Clear up handshake reassembly structure, if any. */
if( ssl->handshake->hs_msg != NULL )
{
mbedtls_free( ssl->handshake->hs_msg );
ssl->handshake->hs_msg = NULL;
}
/* Increment handshake sequence number */
hs->in_msg_seq++;
@ -4554,7 +4411,7 @@ static int ssl_buffer_message( mbedtls_ssl_context *ssl )
break;
case MBEDTLS_SSL_MSG_HANDSHAKE:
/* No support for buffering handshake messages so far. */
/* TODO: Implement buffering and reassembly here. */
break;
default:
@ -8461,7 +8318,6 @@ void mbedtls_ssl_handshake_free( mbedtls_ssl_context *ssl )
#if defined(MBEDTLS_SSL_PROTO_DTLS)
mbedtls_free( handshake->verify_cookie );
mbedtls_free( handshake->hs_msg );
ssl_flight_free( handshake->flight );
ssl_buffering_free( ssl );
#endif