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[tls] Treat handshake digest algorithm as a session parameter
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Simplify code by recording the active handshake digest algorithm as a
session parameter.  (Note that we must still accumulate digests for
all supported algorithms, since we don't know which digest will
eventually be used until we receive the Server Hello.)

Signed-off-by: Michael Brown <mcb30@ipxe.org>
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@mcb30
mcb30 committed Mar 20, 2012
1 parent a156c15 commit 7869f71
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Showing 2 changed files with 28 additions and 39 deletions.
4 changes: 4 additions & 0 deletions src/include/ipxe/tls.h
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Expand Up @@ -201,6 +201,10 @@ struct tls_session {
uint8_t handshake_md5_sha1_ctx[MD5_SHA1_CTX_SIZE];
/** SHA256 context for handshake verification */
uint8_t handshake_sha256_ctx[SHA256_CTX_SIZE];
/** Digest algorithm used for handshake verification */
struct digest_algorithm *handshake_digest;
/** Digest algorithm context used for handshake verification */
uint8_t *handshake_ctx;

/** TX sequence number */
uint64_t tx_seq;
Expand Down
63 changes: 24 additions & 39 deletions src/net/tls.c
View file
Expand Up @@ -697,22 +697,6 @@ static void tls_add_handshake ( struct tls_session *tls,
data, len );
}

/**
* Size of handshake output buffer
*
* @v tls TLS session
*/
static size_t tls_verify_handshake_len ( struct tls_session *tls ) {

if ( tls->version >= TLS_VERSION_TLS_1_2 ) {
/* Use SHA-256 for TLSv1.2 and later */
return SHA256_DIGEST_SIZE;
} else {
/* Use MD5+SHA1 for TLSv1.1 and earlier */
return MD5_SHA1_DIGEST_SIZE;
}
}

/**
* Calculate handshake verification hash
*
Expand All @@ -723,22 +707,11 @@ static size_t tls_verify_handshake_len ( struct tls_session *tls ) {
* messages seen so far.
*/
static void tls_verify_handshake ( struct tls_session *tls, void *out ) {
union {
uint8_t md5_sha1[MD5_SHA1_CTX_SIZE];
uint8_t sha256[SHA256_CTX_SIZE];
} ctx;
struct digest_algorithm *digest = tls->handshake_digest;
uint8_t ctx[ digest->ctxsize ];

if ( tls->version >= TLS_VERSION_TLS_1_2 ) {
/* Use SHA-256 for TLSv1.2 and later */
memcpy ( ctx.sha256, tls->handshake_sha256_ctx,
sizeof ( ctx.sha256 ) );
digest_final ( &sha256_algorithm, ctx.sha256, out );
} else {
/* Use MD5+SHA1 for TLSv1.1 and earlier */
memcpy ( ctx.md5_sha1, tls->handshake_md5_sha1_ctx,
sizeof ( ctx.md5_sha1 ) );
digest_final ( &md5_sha1_algorithm, ctx.md5_sha1, out );
}
memcpy ( ctx, tls->handshake_ctx, sizeof ( ctx ) );
digest_final ( digest, ctx, out );
}

/******************************************************************************
Expand Down Expand Up @@ -915,20 +888,21 @@ static int tls_send_change_cipher ( struct tls_session *tls ) {
* @ret rc Return status code
*/
static int tls_send_finished ( struct tls_session *tls ) {
struct digest_algorithm *digest = tls->handshake_digest;
struct {
uint32_t type_length;
uint8_t verify_data[12];
} __attribute__ (( packed )) finished;
uint8_t digest[ tls_verify_handshake_len ( tls ) ];
uint8_t digest_out[ digest->digestsize ];

memset ( &finished, 0, sizeof ( finished ) );
finished.type_length = ( cpu_to_le32 ( TLS_FINISHED ) |
htonl ( sizeof ( finished ) -
sizeof ( finished.type_length ) ) );
tls_verify_handshake ( tls, digest );
tls_verify_handshake ( tls, digest_out );
tls_prf_label ( tls, &tls->master_secret, sizeof ( tls->master_secret ),
finished.verify_data, sizeof ( finished.verify_data ),
"client finished", digest, sizeof ( digest ) );
"client finished", digest_out, sizeof ( digest_out ) );

return tls_send_handshake ( tls, &finished, sizeof ( finished ) );
}
Expand Down Expand Up @@ -1052,6 +1026,14 @@ static int tls_new_server_hello ( struct tls_session *tls,
DBGC ( tls, "TLS %p using protocol version %d.%d\n",
tls, ( version >> 8 ), ( version & 0xff ) );

/* Use MD5+SHA1 digest algorithm for handshake verification
* for versions earlier than TLSv1.2.
*/
if ( tls->version < TLS_VERSION_TLS_1_2 ) {
tls->handshake_digest = &md5_sha1_algorithm;
tls->handshake_ctx = tls->handshake_md5_sha1_ctx;
}

/* Copy out server random bytes */
memcpy ( &tls->server_random, &hello_a->random,
sizeof ( tls->server_random ) );
Expand Down Expand Up @@ -1254,12 +1236,13 @@ static int tls_new_server_hello_done ( struct tls_session *tls,
*/
static int tls_new_finished ( struct tls_session *tls,
const void *data, size_t len ) {
struct digest_algorithm *digest = tls->handshake_digest;
const struct {
uint8_t verify_data[12];
char next[0];
} __attribute__ (( packed )) *finished = data;
const void *end = finished->next;
uint8_t digest[ tls_verify_handshake_len ( tls ) ];
uint8_t digest_out[ digest->digestsize ];
uint8_t verify_data[ sizeof ( finished->verify_data ) ];

/* Sanity check */
Expand All @@ -1270,10 +1253,10 @@ static int tls_new_finished ( struct tls_session *tls,
}

/* Verify data */
tls_verify_handshake ( tls, digest );
tls_verify_handshake ( tls, digest_out );
tls_prf_label ( tls, &tls->master_secret, sizeof ( tls->master_secret ),
verify_data, sizeof ( verify_data ), "server finished",
digest, sizeof ( digest ) );
digest_out, sizeof ( digest_out ) );
if ( memcmp ( verify_data, finished->verify_data,
sizeof ( verify_data ) ) != 0 ) {
DBGC ( tls, "TLS %p verification failed\n", tls );
Expand Down Expand Up @@ -2014,8 +1997,8 @@ static void tls_tx_step ( struct tls_session *tls ) {
} else if ( tls->tx_pending & TLS_TX_CLIENT_KEY_EXCHANGE ) {
/* Send Client Key Exchange */
if ( ( rc = tls_send_client_key_exchange ( tls ) ) != 0 ) {
DBGC ( tls, "TLS %p could send Client Key Exchange: "
"%s\n", tls, strerror ( rc ) );
DBGC ( tls, "TLS %p could not send Client Key "
"Exchange: %s\n", tls, strerror ( rc ) );
goto err;
}
tls->tx_pending &= ~TLS_TX_CLIENT_KEY_EXCHANGE;
Expand Down Expand Up @@ -2099,6 +2082,8 @@ int add_tls ( struct interface *xfer, const char *name,
}
digest_init ( &md5_sha1_algorithm, tls->handshake_md5_sha1_ctx );
digest_init ( &sha256_algorithm, tls->handshake_sha256_ctx );
tls->handshake_digest = &sha256_algorithm;
tls->handshake_ctx = tls->handshake_sha256_ctx;
tls->tx_pending = TLS_TX_CLIENT_HELLO;
process_init ( &tls->process, &tls_process_desc, &tls->refcnt );

Expand Down

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