From 5aa4e2cedd819b4fd307531eaa64f4f5ca8a01d4 Mon Sep 17 00:00:00 2001 From: Hanno Becker Date: Mon, 6 Aug 2018 09:26:08 +0100 Subject: [PATCH] Move deduction of internal record buffer pointers to function 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. --- library/ssl_tls.c | 138 +++++++++++++++++++++++++++++----------------- 1 file changed, 88 insertions(+), 50 deletions(-) diff --git a/library/ssl_tls.c b/library/ssl_tls.c index 530f283b47..4607749efe 100644 --- a/library/ssl_tls.c +++ b/library/ssl_tls.c @@ -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 );