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Let MBEDTLS_SSL_MAX_CONTENT_LEN to be split into outward & inward sizes

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For the situation where the mbedTLS device has limited RAM, but the
other end of the connection doesn't support the max_fragment_length
extension. To be spec-compliant, mbedTLS has to keep a 16384 byte
incoming buffer. However the outgoing buffer can be made smaller without
breaking spec compliance, and we save some RAM.

See comments in include/mbedtls/config.h for some more details.

(The lower limit of outgoing buffer size is the buffer size used during
handshake/cert negotiation. As the handshake is half-duplex it might
even be possible to store this data in the "incoming" buffer during the
handshake, which would save even more RAM - but it would also be a lot
hackier and error-prone. I didn't really explore this possibility, but
thought I'd mention it here in case someone sees this later on a mission
to jam mbedTLS into an even tinier RAM footprint.)
This commit is contained in:
Angus Gratton 2016-05-25 20:56:48 +10:00
parent 2dbecc04cc
commit d8213d00db
7 changed files with 198 additions and 87 deletions
Download patch file Download diff file Expand all files Collapse all files

108
library/ssl_tls.c
View file

@ -141,14 +141,24 @@ static void ssl_reset_retransmit_timeout( mbedtls_ssl_context *ssl )
* } MaxFragmentLength;
* and we add 0 -> extension unused
*/
static unsigned int mfl_code_to_length[MBEDTLS_SSL_MAX_FRAG_LEN_INVALID] =
static unsigned int ssl_mfl_code_to_length( int mfl )
{
MBEDTLS_SSL_MAX_CONTENT_LEN, /* MBEDTLS_SSL_MAX_FRAG_LEN_NONE */
512, /* MBEDTLS_SSL_MAX_FRAG_LEN_512 */
1024, /* MBEDTLS_SSL_MAX_FRAG_LEN_1024 */
2048, /* MBEDTLS_SSL_MAX_FRAG_LEN_2048 */
4096, /* MBEDTLS_SSL_MAX_FRAG_LEN_4096 */
};
switch( mfl )
{
case MBEDTLS_SSL_MAX_FRAG_LEN_NONE:
return ( MBEDTLS_TLS_EXT_ADV_CONTENT_LEN );
case MBEDTLS_SSL_MAX_FRAG_LEN_512:
return 512;
case MBEDTLS_SSL_MAX_FRAG_LEN_1024:
return 1024;
case MBEDTLS_SSL_MAX_FRAG_LEN_2048:
return 2048;
case MBEDTLS_SSL_MAX_FRAG_LEN_4096:
return 4096;
default:
return ( MBEDTLS_TLS_EXT_ADV_CONTENT_LEN );
}
}
#endif /* MBEDTLS_SSL_MAX_FRAGMENT_LENGTH */
#if defined(MBEDTLS_SSL_CLI_C)
@ -956,11 +966,11 @@ int mbedtls_ssl_derive_keys( mbedtls_ssl_context *ssl )
if( ssl->compress_buf == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 3, ( "Allocating compression buffer" ) );
ssl->compress_buf = mbedtls_calloc( 1, MBEDTLS_SSL_BUFFER_LEN );
ssl->compress_buf = mbedtls_calloc( 1, MBEDTLS_SSL_COMPRESS_BUFFER_LEN );
if( ssl->compress_buf == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc(%d bytes) failed",
MBEDTLS_SSL_BUFFER_LEN ) );
MBEDTLS_SSL_COMPRESS_BUFFER_LEN ) );
return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
}
}
@ -1297,11 +1307,11 @@ static int ssl_encrypt_buf( mbedtls_ssl_context *ssl )
MBEDTLS_SSL_DEBUG_BUF( 4, "before encrypt: output payload",
ssl->out_msg, ssl->out_msglen );
if( ssl->out_msglen > MBEDTLS_SSL_MAX_CONTENT_LEN )
if( ssl->out_msglen > MBEDTLS_SSL_OUT_CONTENT_LEN )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "Record content %u too large, maximum %d",
(unsigned) ssl->out_msglen,
MBEDTLS_SSL_MAX_CONTENT_LEN ) );
MBEDTLS_SSL_OUT_CONTENT_LEN ) );
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
@ -1906,14 +1916,14 @@ static int ssl_decrypt_buf( mbedtls_ssl_context *ssl )
* Padding is guaranteed to be incorrect if:
* 1. padlen >= ssl->in_msglen
*
* 2. padding_idx >= MBEDTLS_SSL_MAX_CONTENT_LEN +
* 2. padding_idx >= MBEDTLS_SSL_IN_CONTENT_LEN +
* ssl->transform_in->maclen
*
* In both cases we reset padding_idx to a safe value (0) to
* prevent out-of-buffer reads.
*/
correct &= ( ssl->in_msglen >= padlen + 1 );
correct &= ( padding_idx < MBEDTLS_SSL_MAX_CONTENT_LEN +
correct &= ( padding_idx < MBEDTLS_SSL_IN_CONTENT_LEN +
ssl->transform_in->maclen );
padding_idx *= correct;
@ -2126,7 +2136,7 @@ static int ssl_compress_buf( mbedtls_ssl_context *ssl )
ssl->transform_out->ctx_deflate.next_in = msg_pre;
ssl->transform_out->ctx_deflate.avail_in = len_pre;
ssl->transform_out->ctx_deflate.next_out = msg_post;
ssl->transform_out->ctx_deflate.avail_out = MBEDTLS_SSL_BUFFER_LEN - bytes_written;
ssl->transform_out->ctx_deflate.avail_out = MBEDTLS_SSL_OUT_BUFFER_LEN - bytes_written;
ret = deflate( &ssl->transform_out->ctx_deflate, Z_SYNC_FLUSH );
if( ret != Z_OK )
@ -2135,7 +2145,7 @@ static int ssl_compress_buf( mbedtls_ssl_context *ssl )
return( MBEDTLS_ERR_SSL_COMPRESSION_FAILED );
}
ssl->out_msglen = MBEDTLS_SSL_BUFFER_LEN -
ssl->out_msglen = MBEDTLS_SSL_OUT_BUFFER_LEN -
ssl->transform_out->ctx_deflate.avail_out - bytes_written;
MBEDTLS_SSL_DEBUG_MSG( 3, ( "after compression: msglen = %d, ",
@ -2173,7 +2183,7 @@ static int ssl_decompress_buf( mbedtls_ssl_context *ssl )
ssl->transform_in->ctx_inflate.next_in = msg_pre;
ssl->transform_in->ctx_inflate.avail_in = len_pre;
ssl->transform_in->ctx_inflate.next_out = msg_post;
ssl->transform_in->ctx_inflate.avail_out = MBEDTLS_SSL_BUFFER_LEN -
ssl->transform_in->ctx_inflate.avail_out = MBEDTLS_SSL_IN_BUFFER_LEN -
header_bytes;
ret = inflate( &ssl->transform_in->ctx_inflate, Z_SYNC_FLUSH );
@ -2183,7 +2193,7 @@ static int ssl_decompress_buf( mbedtls_ssl_context *ssl )
return( MBEDTLS_ERR_SSL_COMPRESSION_FAILED );
}
ssl->in_msglen = MBEDTLS_SSL_BUFFER_LEN -
ssl->in_msglen = MBEDTLS_SSL_IN_BUFFER_LEN -
ssl->transform_in->ctx_inflate.avail_out - header_bytes;
MBEDTLS_SSL_DEBUG_MSG( 3, ( "after decompression: msglen = %d, ",
@ -2258,7 +2268,7 @@ int mbedtls_ssl_fetch_input( mbedtls_ssl_context *ssl, size_t nb_want )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
if( nb_want > MBEDTLS_SSL_BUFFER_LEN - (size_t)( ssl->in_hdr - ssl->in_buf ) )
if( nb_want > MBEDTLS_SSL_IN_BUFFER_LEN - (size_t)( ssl->in_hdr - ssl->in_buf ) )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "requesting more data than fits" ) );
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
@ -2344,7 +2354,7 @@ int mbedtls_ssl_fetch_input( mbedtls_ssl_context *ssl, size_t nb_want )
}
else
{
len = MBEDTLS_SSL_BUFFER_LEN - ( ssl->in_hdr - ssl->in_buf );
len = MBEDTLS_SSL_IN_BUFFER_LEN - ( ssl->in_hdr - ssl->in_buf );
if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER )
timeout = ssl->handshake->retransmit_timeout;
@ -2798,12 +2808,12 @@ int mbedtls_ssl_write_record( mbedtls_ssl_context *ssl )
if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
{
/* Make room for the additional DTLS fields */
if( MBEDTLS_SSL_MAX_CONTENT_LEN - ssl->out_msglen < 8 )
if( MBEDTLS_SSL_OUT_CONTENT_LEN - ssl->out_msglen < 8 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "DTLS handshake message too large: "
"size %u, maximum %u",
(unsigned) ( ssl->in_hslen - 4 ),
(unsigned) ( MBEDTLS_SSL_MAX_CONTENT_LEN - 12 ) ) );
(unsigned) ( MBEDTLS_SSL_OUT_CONTENT_LEN - 12 ) ) );
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
@ -3016,7 +3026,7 @@ static int ssl_reassemble_dtls_handshake( mbedtls_ssl_context *ssl )
MBEDTLS_SSL_DEBUG_MSG( 2, ( "initialize reassembly, total length = %d",
msg_len ) );
if( ssl->in_hslen > MBEDTLS_SSL_MAX_CONTENT_LEN )
if( ssl->in_hslen > MBEDTLS_SSL_IN_CONTENT_LEN )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "handshake message too large" ) );
return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
@ -3120,7 +3130,7 @@ static int ssl_reassemble_dtls_handshake( mbedtls_ssl_context *ssl )
ssl->next_record_offset = new_remain - ssl->in_hdr;
ssl->in_left = ssl->next_record_offset + remain_len;
if( ssl->in_left > MBEDTLS_SSL_BUFFER_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" ) );
@ -3496,7 +3506,7 @@ static int ssl_handle_possible_reconnect( mbedtls_ssl_context *ssl )
ssl->conf->p_cookie,
ssl->cli_id, ssl->cli_id_len,
ssl->in_buf, ssl->in_left,
ssl->out_buf, MBEDTLS_SSL_MAX_CONTENT_LEN, &len );
ssl->out_buf, MBEDTLS_SSL_OUT_CONTENT_LEN, &len );
MBEDTLS_SSL_DEBUG_RET( 2, "ssl_check_dtls_clihlo_cookie", ret );
@ -3593,7 +3603,7 @@ static int ssl_parse_record_header( mbedtls_ssl_context *ssl )
}
/* Check length against the size of our buffer */
if( ssl->in_msglen > MBEDTLS_SSL_BUFFER_LEN
if( ssl->in_msglen > MBEDTLS_SSL_IN_BUFFER_LEN
- (size_t)( ssl->in_msg - ssl->in_buf ) )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
@ -3687,7 +3697,7 @@ static int ssl_parse_record_header( mbedtls_ssl_context *ssl )
if( ssl->transform_in == NULL )
{
if( ssl->in_msglen < 1 ||
ssl->in_msglen > MBEDTLS_SSL_MAX_CONTENT_LEN )
ssl->in_msglen > MBEDTLS_SSL_IN_CONTENT_LEN )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
return( MBEDTLS_ERR_SSL_INVALID_RECORD );
@ -3703,7 +3713,7 @@ static int ssl_parse_record_header( mbedtls_ssl_context *ssl )
#if defined(MBEDTLS_SSL_PROTO_SSL3)
if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_0 &&
ssl->in_msglen > ssl->transform_in->minlen + MBEDTLS_SSL_MAX_CONTENT_LEN )
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 );
@ -3716,7 +3726,7 @@ static int ssl_parse_record_header( mbedtls_ssl_context *ssl )
*/
if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_1 &&
ssl->in_msglen > ssl->transform_in->minlen +
MBEDTLS_SSL_MAX_CONTENT_LEN + 256 )
MBEDTLS_SSL_IN_CONTENT_LEN + 256 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
return( MBEDTLS_ERR_SSL_INVALID_RECORD );
@ -3764,7 +3774,7 @@ static int ssl_prepare_record_content( mbedtls_ssl_context *ssl )
MBEDTLS_SSL_DEBUG_BUF( 4, "input payload after decrypt",
ssl->in_msg, ssl->in_msglen );
if( ssl->in_msglen > MBEDTLS_SSL_MAX_CONTENT_LEN )
if( ssl->in_msglen > MBEDTLS_SSL_IN_CONTENT_LEN )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
return( MBEDTLS_ERR_SSL_INVALID_RECORD );
@ -4325,10 +4335,10 @@ int mbedtls_ssl_write_certificate( mbedtls_ssl_context *ssl )
while( crt != NULL )
{
n = crt->raw.len;
if( n > MBEDTLS_SSL_MAX_CONTENT_LEN - 3 - i )
if( n > MBEDTLS_SSL_OUT_CONTENT_LEN - 3 - i )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "certificate too large, %d > %d",
i + 3 + n, MBEDTLS_SSL_MAX_CONTENT_LEN ) );
i + 3 + n, MBEDTLS_SSL_OUT_CONTENT_LEN ) );
return( MBEDTLS_ERR_SSL_CERTIFICATE_TOO_LARGE );
}
@ -5662,17 +5672,23 @@ int mbedtls_ssl_setup( mbedtls_ssl_context *ssl,
const mbedtls_ssl_config *conf )
{
int ret;
const size_t len = MBEDTLS_SSL_BUFFER_LEN;
ssl->conf = conf;
/*
* Prepare base structures
*/
if( ( ssl-> in_buf = mbedtls_calloc( 1, len ) ) == NULL ||
( ssl->out_buf = mbedtls_calloc( 1, len ) ) == NULL )
ssl->in_buf = mbedtls_calloc( 1, MBEDTLS_SSL_IN_BUFFER_LEN );
if( ssl->in_buf == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc(%d bytes) failed", len ) );
MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc(%d bytes) failed", MBEDTLS_SSL_IN_BUFFER_LEN) );
return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
}
ssl->out_buf = mbedtls_calloc( 1, MBEDTLS_SSL_OUT_BUFFER_LEN );
if( ssl->out_buf == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc(%d bytes) failed", MBEDTLS_SSL_OUT_BUFFER_LEN) );
mbedtls_free( ssl->in_buf );
ssl->in_buf = NULL;
return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
@ -5773,9 +5789,9 @@ static int ssl_session_reset_int( mbedtls_ssl_context *ssl, int partial )
ssl->transform_in = NULL;
ssl->transform_out = NULL;
memset( ssl->out_buf, 0, MBEDTLS_SSL_BUFFER_LEN );
memset( ssl->out_buf, 0, MBEDTLS_SSL_OUT_BUFFER_LEN );
if( partial == 0 )
memset( ssl->in_buf, 0, MBEDTLS_SSL_BUFFER_LEN );
memset( ssl->in_buf, 0, MBEDTLS_SSL_IN_BUFFER_LEN );
#if defined(MBEDTLS_SSL_HW_RECORD_ACCEL)
if( mbedtls_ssl_hw_record_reset != NULL )
@ -6100,7 +6116,7 @@ int mbedtls_ssl_conf_psk( mbedtls_ssl_config *conf,
/* Identity len will be encoded on two bytes */
if( ( psk_identity_len >> 16 ) != 0 ||
psk_identity_len > MBEDTLS_SSL_MAX_CONTENT_LEN )
psk_identity_len > MBEDTLS_SSL_OUT_CONTENT_LEN )
{
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
@ -6401,7 +6417,7 @@ void mbedtls_ssl_conf_arc4_support( mbedtls_ssl_config *conf, char arc4 )
int mbedtls_ssl_conf_max_frag_len( mbedtls_ssl_config *conf, unsigned char mfl_code )
{
if( mfl_code >= MBEDTLS_SSL_MAX_FRAG_LEN_INVALID ||
mfl_code_to_length[mfl_code] > MBEDTLS_SSL_MAX_CONTENT_LEN )
ssl_mfl_code_to_length( mfl_code ) > MBEDTLS_TLS_EXT_ADV_CONTENT_LEN )
{
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
@ -6679,15 +6695,15 @@ size_t mbedtls_ssl_get_max_frag_len( const mbedtls_ssl_context *ssl )
/*
* Assume mfl_code is correct since it was checked when set
*/
max_len = mfl_code_to_length[ssl->conf->mfl_code];
max_len = ssl_mfl_code_to_length( ssl->conf->mfl_code );
/*
* Check if a smaller max length was negotiated
*/
if( ssl->session_out != NULL &&
mfl_code_to_length[ssl->session_out->mfl_code] < max_len )
ssl_mfl_code_to_length( ssl->session_out->mfl_code ) < max_len )
{
max_len = mfl_code_to_length[ssl->session_out->mfl_code];
max_len = ssl_mfl_code_to_length( ssl->session_out->mfl_code );
}
return max_len;
@ -7241,7 +7257,7 @@ static int ssl_write_real( mbedtls_ssl_context *ssl,
#if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
size_t max_len = mbedtls_ssl_get_max_frag_len( ssl );
#else
size_t max_len = MBEDTLS_SSL_MAX_CONTENT_LEN;
size_t max_len = MBEDTLS_SSL_OUT_CONTENT_LEN;
#endif /* MBEDTLS_SSL_MAX_FRAGMENT_LENGTH */
if( len > max_len )
{
@ -7543,20 +7559,20 @@ void mbedtls_ssl_free( mbedtls_ssl_context *ssl )
if( ssl->out_buf != NULL )
{
mbedtls_platform_zeroize( ssl->out_buf, MBEDTLS_SSL_BUFFER_LEN );
mbedtls_platform_zeroize( ssl->out_buf, MBEDTLS_SSL_OUT_BUFFER_LEN );
mbedtls_free( ssl->out_buf );
}
if( ssl->in_buf != NULL )
{
mbedtls_platform_zeroize( ssl->in_buf, MBEDTLS_SSL_BUFFER_LEN );
mbedtls_platform_zeroize( ssl->in_buf, MBEDTLS_SSL_IN_BUFFER_LEN );
mbedtls_free( ssl->in_buf );
}
#if defined(MBEDTLS_ZLIB_SUPPORT)
if( ssl->compress_buf != NULL )
{
mbedtls_platform_zeroize( ssl->compress_buf, MBEDTLS_SSL_BUFFER_LEN );
mbedtls_platform_zeroize( ssl->compress_buf, MBEDTLS_SSL_COMPRESS_BUFFER_LEN );
mbedtls_free( ssl->compress_buf );
}
#endif