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Incorporate CID into MAC computations during record protection

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This commit modifies ssl_decrypt_buf() and ssl_encrypt_buf()
to include the CID into authentication data during record
protection.

It does not yet implement the new DTLSInnerPlaintext format
from https://tools.ietf.org/html/draft-ietf-tls-dtls-connection-id-04
This commit is contained in:
Hanno Becker 2019-04-29 13:52:53 +01:00
parent f2ed4482d7
commit cab87e68b6
1 changed files with 89 additions and 26 deletions
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115
library/ssl_tls.c
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@ -1964,14 +1964,41 @@ static void ssl_read_memory( unsigned char *p, size_t len )
* Encryption/decryption functions
*/
/* add_data must have size ( 13 + SSL_CID_LEN_MAX ) Bytes */
static void ssl_extract_add_data_from_record( unsigned char* add_data,
size_t *add_data_len,
mbedtls_record *rec )
{
/* Quoting RFC 5246:
*
* additional_data = seq_num + TLSCompressed.type +
* TLSCompressed.version + TLSCompressed.length;
*
* For the CID extension, this is extended as follows:
*
* additional_data = seq_num + DTLSPlaintext.type +
* DTLSPlaintext.version +
* cid + // New input
* cid_length + // New input
* length_of_DTLSInnerPlaintext;
*/
memcpy( add_data, rec->ctr, sizeof( rec->ctr ) );
add_data[8] = rec->type;
memcpy( add_data + 9, rec->ver, sizeof( rec->ver ) );
add_data[11] = ( rec->data_len >> 8 ) & 0xFF;
add_data[12] = rec->data_len & 0xFF;
memcpy( add_data + 9, rec->ver, sizeof( rec->ver ) );
#if defined(MBEDTLS_SSL_CID)
memcpy( add_data + 11, rec->cid, rec->cid_len );
#endif /* MBEDTLS_SSL_CID */
add_data[11 + rec->cid_len + 0] = ( rec->data_len >> 8 ) & 0xFF;
add_data[11 + rec->cid_len + 1] = ( rec->data_len >> 0 ) & 0xFF;
#if defined(MBEDTLS_SSL_CID)
*add_data_len = 13 + rec->cid_len;
#else
*add_data_len = 13;
#endif /* MBEDTLS_SSL_CID */
}
int mbedtls_ssl_encrypt_buf( mbedtls_ssl_context *ssl,
@ -1983,7 +2010,8 @@ int mbedtls_ssl_encrypt_buf( mbedtls_ssl_context *ssl,
mbedtls_cipher_mode_t mode;
int auth_done = 0;
unsigned char * data;
unsigned char add_data[13];
unsigned char add_data[13 + SSL_CID_LEN_MAX ];
size_t add_data_len;
size_t post_avail;
/* The SSL context is only used for debugging purposes! */
@ -2012,7 +2040,8 @@ int mbedtls_ssl_encrypt_buf( mbedtls_ssl_context *ssl,
if( rec == NULL ||
rec->buf == NULL ||
rec->buf_len < rec->data_offset ||
rec->buf_len - rec->data_offset < rec->data_len )
rec->buf_len - rec->data_offset < rec->data_len ||
rec->cid_len != 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad record structure provided to encrypt_buf" ) );
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
@ -2033,6 +2062,15 @@ int mbedtls_ssl_encrypt_buf( mbedtls_ssl_context *ssl,
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
#if defined(MBEDTLS_SSL_CID)
/*
* Add CID information
*/
rec->cid_len = transform->out_cid_len;
memcpy( rec->cid, transform->out_cid, transform->out_cid_len );
MBEDTLS_SSL_DEBUG_BUF( 3, "CID", rec->cid, rec->cid_len );
#endif /* MBEDTLS_SSL_CID */
/*
* Add MAC before if needed
*/
@ -2066,10 +2104,10 @@ int mbedtls_ssl_encrypt_buf( mbedtls_ssl_context *ssl,
{
unsigned char mac[MBEDTLS_SSL_MAC_ADD];
ssl_extract_add_data_from_record( add_data, rec );
ssl_extract_add_data_from_record( add_data, &add_data_len, rec );
mbedtls_md_hmac_update( &transform->md_ctx_enc, add_data,
sizeof( add_data ) );
add_data_len );
mbedtls_md_hmac_update( &transform->md_ctx_enc,
data, rec->data_len );
mbedtls_md_hmac_finish( &transform->md_ctx_enc, mac );
@ -2172,14 +2210,14 @@ int mbedtls_ssl_encrypt_buf( mbedtls_ssl_context *ssl,
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
ssl_extract_add_data_from_record( add_data, rec );
ssl_extract_add_data_from_record( add_data, &add_data_len, rec );
MBEDTLS_SSL_DEBUG_BUF( 4, "IV used (internal)",
iv, transform->ivlen );
MBEDTLS_SSL_DEBUG_BUF( 4, "IV used (transmitted)",
data - explicit_iv_len, explicit_iv_len );
MBEDTLS_SSL_DEBUG_BUF( 4, "additional data used for AEAD",
add_data, 13 );
add_data, add_data_len );
MBEDTLS_SSL_DEBUG_MSG( 3, ( "before encrypt: msglen = %d, "
"including 0 bytes of padding",
rec->data_len ) );
@ -2190,7 +2228,7 @@ int mbedtls_ssl_encrypt_buf( mbedtls_ssl_context *ssl,
if( ( ret = mbedtls_cipher_auth_encrypt( &transform->cipher_ctx_enc,
iv, transform->ivlen,
add_data, 13, /* add data */
add_data, add_data_len, /* add data */
data, rec->data_len, /* source */
data, &rec->data_len, /* destination */
data + rec->data_len, transform->taglen ) ) != 0 )
@ -2326,14 +2364,14 @@ int mbedtls_ssl_encrypt_buf( mbedtls_ssl_context *ssl,
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
}
ssl_extract_add_data_from_record( add_data, rec );
ssl_extract_add_data_from_record( add_data, &add_data_len, rec );
MBEDTLS_SSL_DEBUG_MSG( 3, ( "using encrypt then mac" ) );
MBEDTLS_SSL_DEBUG_BUF( 4, "MAC'd meta-data", add_data,
sizeof( add_data ) );
add_data_len );
mbedtls_md_hmac_update( &transform->md_ctx_enc, add_data,
sizeof( add_data ) );
add_data_len );
mbedtls_md_hmac_update( &transform->md_ctx_enc,
data, rec->data_len );
mbedtls_md_hmac_finish( &transform->md_ctx_enc, mac );
@ -2378,7 +2416,8 @@ int mbedtls_ssl_decrypt_buf( mbedtls_ssl_context *ssl,
size_t padlen = 0, correct = 1;
#endif
unsigned char* data;
unsigned char add_data[13];
unsigned char add_data[13 + SSL_CID_LEN_MAX ];
size_t add_data_len;
#if !defined(MBEDTLS_DEBUG_C)
((void) ssl);
@ -2402,6 +2441,23 @@ int mbedtls_ssl_decrypt_buf( mbedtls_ssl_context *ssl,
data = rec->buf + rec->data_offset;
mode = mbedtls_cipher_get_cipher_mode( &transform->cipher_ctx_dec );
#if defined(MBEDTLS_SSL_CID)
/*
* Match record's CID with incoming CID.
*/
/* TODO - Uncomment this once CID parsing is in place */
/* if( rec->cid_len != transform->in_cid_len || */
/* memcmp( rec->cid, transform->in_cid, rec->cid_len ) != 0 ) */
/* { */
/* return( MBEDTLS_ERR_SSL_INVALID_RECORD ); */
/* } */
/* TODO - Remove this once CID parsing is in place */
rec->cid_len = transform->in_cid_len;
memcpy( rec->cid, transform->in_cid, transform->in_cid_len );
MBEDTLS_SSL_DEBUG_BUF( 3, "CID", rec->cid, rec->cid_len );
#endif /* MBEDTLS_SSL_CID */
#if defined(MBEDTLS_ARC4_C) || defined(MBEDTLS_CIPHER_NULL_CIPHER)
if( mode == MBEDTLS_MODE_STREAM )
{
@ -2476,9 +2532,9 @@ int mbedtls_ssl_decrypt_buf( mbedtls_ssl_context *ssl,
rec->data_offset += explicit_iv_len;
rec->data_len -= explicit_iv_len + transform->taglen;
ssl_extract_add_data_from_record( add_data, rec );
ssl_extract_add_data_from_record( add_data, &add_data_len, rec );
MBEDTLS_SSL_DEBUG_BUF( 4, "additional data used for AEAD",
add_data, 13 );
add_data, add_data_len );
memcpy( transform->iv_dec + transform->fixed_ivlen,
data - explicit_iv_len, explicit_iv_len );
@ -2493,7 +2549,7 @@ int mbedtls_ssl_decrypt_buf( mbedtls_ssl_context *ssl,
*/
if( ( ret = mbedtls_cipher_auth_decrypt( &transform->cipher_ctx_dec,
iv, transform->ivlen,
add_data, 13,
add_data, add_data_len,
data, rec->data_len,
data, &olen,
data + rec->data_len,
@ -2577,10 +2633,12 @@ int mbedtls_ssl_decrypt_buf( mbedtls_ssl_context *ssl,
/* Safe due to the check data_len >= minlen + maclen + 1 above. */
rec->data_len -= transform->maclen;
ssl_extract_add_data_from_record( add_data, rec );
ssl_extract_add_data_from_record( add_data, &add_data_len, rec );
MBEDTLS_SSL_DEBUG_BUF( 4, "MAC'd meta-data", add_data, 13 );
mbedtls_md_hmac_update( &transform->md_ctx_dec, add_data, 13 );
MBEDTLS_SSL_DEBUG_BUF( 4, "MAC'd meta-data", add_data,
add_data_len );
mbedtls_md_hmac_update( &transform->md_ctx_dec, add_data,
add_data_len );
mbedtls_md_hmac_update( &transform->md_ctx_dec,
data, rec->data_len );
mbedtls_md_hmac_finish( &transform->md_ctx_dec, mac_expect );
@ -2784,7 +2842,7 @@ int mbedtls_ssl_decrypt_buf( mbedtls_ssl_context *ssl,
*/
rec->data_len -= transform->maclen;
ssl_extract_add_data_from_record( add_data, rec );
ssl_extract_add_data_from_record( add_data, &add_data_len, rec );
#if defined(MBEDTLS_SSL_PROTO_SSL3)
if( transform->minor_ver == MBEDTLS_SSL_MINOR_VERSION_0 )
@ -2854,15 +2912,17 @@ int mbedtls_ssl_decrypt_buf( mbedtls_ssl_context *ssl,
case MBEDTLS_MD_SHA1:
case MBEDTLS_MD_SHA256:
/* 8 bytes of message size, 64-byte compression blocks */
extra_run = ( 13 + rec->data_len + padlen + 8 ) / 64 -
( 13 + rec->data_len + 8 ) / 64;
extra_run =
( add_data_len + rec->data_len + padlen + 8 ) / 64 -
( add_data_len + rec->data_len + 8 ) / 64;
break;
#endif
#if defined(MBEDTLS_SHA512_C)
case MBEDTLS_MD_SHA384:
/* 16 bytes of message size, 128-byte compression blocks */
extra_run = ( 13 + rec->data_len + padlen + 16 ) / 128 -
( 13 + rec->data_len + 16 ) / 128;
extra_run =
( add_data_len + rec->data_len + padlen + 16 ) / 128 -
( add_data_len + rec->data_len + 16 ) / 128;
break;
#endif
default:
@ -2872,7 +2932,8 @@ int mbedtls_ssl_decrypt_buf( mbedtls_ssl_context *ssl,
extra_run &= correct * 0xFF;
mbedtls_md_hmac_update( &transform->md_ctx_dec, add_data, 13 );
mbedtls_md_hmac_update( &transform->md_ctx_dec, add_data,
add_data_len );
mbedtls_md_hmac_update( &transform->md_ctx_dec, data,
rec->data_len );
/* Make sure we access everything even when padlen > 0. This
@ -3960,6 +4021,8 @@ int mbedtls_ssl_write_record( mbedtls_ssl_context *ssl, uint8_t force_flush )
ssl->conf->transport, rec.ver );
rec.type = ssl->out_msgtype;
rec.cid_len = 0;
if( ( ret = mbedtls_ssl_encrypt_buf( ssl, ssl->transform_out, &rec,
ssl->conf->f_rng, ssl->conf->p_rng ) ) != 0 )
{