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Move deduction of internal record buffer pointers to function

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The SSL/TLS module maintains a number of internally used pointers
`out_hdr`, `out_len`, `out_iv`, ..., indicating where to write the
various parts of the record header.

These pointers have to be kept in sync and sometimes need update:
Most notably, the `out_msg` pointer should always point to the
beginning of the record payload, and its offset from the pointer
`out_iv` pointing to the end of the record header is determined
by the length of the explicit IV used in the current record
protection mechanism.

This commit introduces functions deducing these pointers from
the pointers `out_hdr` / `in_hdr` to the beginning of the header
of the current outgoing / incoming record.

The flexibility gained by these functions will subsequently
be used to allow shifting of `out_hdr` for the purpose of
packing multiple records into a single datagram.
This commit is contained in:
Hanno Becker 2018-08-06 09:26:08 +01:00
parent 38110dfc0e
commit 5aa4e2cedd
1 changed files with 88 additions and 50 deletions
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138
library/ssl_tls.c
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@ -96,6 +96,10 @@ static int ssl_check_timer( mbedtls_ssl_context *ssl )
return( 0 );
}
static void ssl_update_out_pointers( mbedtls_ssl_context *ssl,
mbedtls_ssl_transform *transform );
static void ssl_update_in_pointers( mbedtls_ssl_context *ssl,
mbedtls_ssl_transform *transform );
#if defined(MBEDTLS_SSL_PROTO_DTLS)
/*
* Double the retransmit timeout value, within the allowed range,
@ -2799,14 +2803,7 @@ static void ssl_swap_epochs( mbedtls_ssl_context *ssl )
memcpy( ssl->handshake->alt_out_ctr, tmp_out_ctr, 8 );
/* Adjust to the newly activated transform */
if( ssl->transform_out != NULL &&
ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
{
ssl->out_msg = ssl->out_iv + ssl->transform_out->ivlen -
ssl->transform_out->fixed_ivlen;
}
else
ssl->out_msg = ssl->out_iv;
ssl_update_out_pointers( ssl, ssl->transform_out );
#if defined(MBEDTLS_SSL_HW_RECORD_ACCEL)
if( mbedtls_ssl_hw_record_activate != NULL )
@ -5171,16 +5168,7 @@ int mbedtls_ssl_parse_change_cipher_spec( mbedtls_ssl_context *ssl )
#endif /* MBEDTLS_SSL_PROTO_DTLS */
memset( ssl->in_ctr, 0, 8 );
/*
* Set the in_msg pointer to the correct location based on IV length
*/
if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
{
ssl->in_msg = ssl->in_iv + ssl->transform_negotiate->ivlen -
ssl->transform_negotiate->fixed_ivlen;
}
else
ssl->in_msg = ssl->in_iv;
ssl_update_in_pointers( ssl, ssl->transform_negotiate );
#if defined(MBEDTLS_SSL_HW_RECORD_ACCEL)
if( mbedtls_ssl_hw_record_activate != NULL )
@ -5631,16 +5619,7 @@ int mbedtls_ssl_write_finished( mbedtls_ssl_context *ssl )
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write finished" ) );
/*
* Set the out_msg pointer to the correct location based on IV length
*/
if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
{
ssl->out_msg = ssl->out_iv + ssl->transform_negotiate->ivlen -
ssl->transform_negotiate->fixed_ivlen;
}
else
ssl->out_msg = ssl->out_iv;
ssl_update_out_pointers( ssl, ssl->transform_negotiate );
ssl->handshake->calc_finished( ssl, ssl->out_msg + 4, ssl->conf->endpoint );
@ -5999,6 +5978,78 @@ static int ssl_cookie_check_dummy( void *ctx,
}
#endif /* MBEDTLS_SSL_DTLS_HELLO_VERIFY && MBEDTLS_SSL_SRV_C */
/* Once ssl->out_hdr as the address of the beginning of the
* next outgoing record is set, deduce the other pointers.
*
* Note: For TLS, we save the implicit record sequence number
* (entering MAC computation) in the 8 bytes before ssl->out_hdr,
* and the caller has to make sure there's space for this.
*/
static void ssl_update_out_pointers( mbedtls_ssl_context *ssl,
mbedtls_ssl_transform *transform )
{
#if defined(MBEDTLS_SSL_PROTO_DTLS)
if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
{
ssl->out_ctr = ssl->out_hdr + 3;
ssl->out_len = ssl->out_hdr + 11;
ssl->out_iv = ssl->out_hdr + 13;
}
else
#endif
{
ssl->out_ctr = ssl->out_hdr - 8;
ssl->out_len = ssl->out_hdr + 3;
ssl->out_iv = ssl->out_hdr + 5;
}
/* Adjust out_msg to make space for explicit IV, if used. */
if( transform != NULL &&
ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
{
ssl->out_msg = ssl->out_iv + transform->ivlen - transform->fixed_ivlen;
}
else
ssl->out_msg = ssl->out_iv;
}
/* Once ssl->in_hdr as the address of the beginning of the
* next incoming record is set, deduce the other pointers.
*
* Note: For TLS, we save the implicit record sequence number
* (entering MAC computation) in the 8 bytes before ssl->in_hdr,
* and the caller has to make sure there's space for this.
*/
static void ssl_update_in_pointers( mbedtls_ssl_context *ssl,
mbedtls_ssl_transform *transform )
{
#if defined(MBEDTLS_SSL_PROTO_DTLS)
if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
{
ssl->in_ctr = ssl->in_hdr + 3;
ssl->in_len = ssl->in_hdr + 11;
ssl->in_iv = ssl->in_hdr + 13;
}
else
#endif
{
ssl->in_ctr = ssl->in_hdr - 8;
ssl->in_len = ssl->in_hdr + 3;
ssl->in_iv = ssl->in_hdr + 5;
}
/* Offset in_msg from in_iv to allow space for explicit IV, if used. */
if( transform != NULL &&
ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
{
ssl->in_msg = ssl->in_iv + transform->ivlen - transform->fixed_ivlen;
}
else
ssl->in_msg = ssl->in_iv;
}
/*
* Initialize an SSL context
*/
@ -6036,37 +6087,24 @@ int mbedtls_ssl_setup( mbedtls_ssl_context *ssl,
return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
}
/* Set the incoming and outgoing record pointers. */
#if defined(MBEDTLS_SSL_PROTO_DTLS)
if( conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
{
ssl->out_hdr = ssl->out_buf;
ssl->out_ctr = ssl->out_buf + 3;
ssl->out_len = ssl->out_buf + 11;
ssl->out_iv = ssl->out_buf + 13;
ssl->out_msg = ssl->out_buf + 13;
ssl->in_hdr = ssl->in_buf;
ssl->in_ctr = ssl->in_buf + 3;
ssl->in_len = ssl->in_buf + 11;
ssl->in_iv = ssl->in_buf + 13;
ssl->in_msg = ssl->in_buf + 13;
ssl->in_hdr = ssl->in_buf;
}
else
#endif
#endif /* MBEDTLS_SSL_PROTO_DTLS */
{
ssl->out_ctr = ssl->out_buf;
ssl->out_hdr = ssl->out_buf + 8;
ssl->out_len = ssl->out_buf + 11;
ssl->out_iv = ssl->out_buf + 13;
ssl->out_msg = ssl->out_buf + 13;
ssl->in_ctr = ssl->in_buf;
ssl->in_hdr = ssl->in_buf + 8;
ssl->in_len = ssl->in_buf + 11;
ssl->in_iv = ssl->in_buf + 13;
ssl->in_msg = ssl->in_buf + 13;
ssl->out_hdr = ssl->out_buf + 8;
ssl->in_hdr = ssl->in_buf + 8;
}
/* Derive other internal pointers. */
ssl_update_out_pointers( ssl, NULL /* no transform enabled */ );
ssl_update_in_pointers ( ssl, NULL /* no transform enabled */ );
if( ( ret = ssl_handshake_init( ssl ) ) != 0 )
return( ret );