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TLS13: handle Key Update for decryption 

Generate new key upon receipt of Key Update message. Untested.
Note that the "traffic_secret" field in SslDecryptSession was unused and
since the client and server have two different encryption states, store
the application traffic secret in SslDecoder.

Change-Id: Iefca3f6cb75745a996fecb0fe7769c876dc9c4ee
Ping-Bug: 12779
Reviewed-on: https://code.wireshark.org/review/20013
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Peter Wu <peter@lekensteyn.nl>
This commit is contained in:
Peter Wu 2017-02-11 12:02:40 +01:00
parent eb1a63f3bc
commit 6cc7a7031d
3 changed files with 71 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

63
epan/dissectors/packet-ssl-utils.c
View File

@ -5176,13 +5176,68 @@ tls13_change_key(SslDecryptSession *ssl, ssl_master_key_map_t *mk_map,
}
/* TLS 1.3 secret found, set new keys. */
ssl->traffic_secret.data = (guchar *) wmem_realloc(wmem_file_scope(),
ssl->traffic_secret.data, secret->data_len);
ssl_data_set(&ssl->traffic_secret, secret->data, secret->data_len);
ssl_debug_printf("%s Retrieved TLS 1.3 traffic secret.\n", G_STRFUNC);
ssl_print_string("Client Random", &ssl->client_random);
ssl_print_string(label, secret);
tls13_generate_keys(ssl, secret, is_from_server);
if (tls13_generate_keys(ssl, secret, is_from_server)) {
/*
* Remember the application traffic secret to support Key Update. The
* other secrets cannot be used for this purpose, so free them.
*/
SslDecoder *decoder = is_from_server ? ssl->server : ssl->client;
StringInfo *app_secret = &decoder->app_traffic_secret;
if (type == TLS_SECRET_APP) {
app_secret->data = (guchar *) wmem_realloc(wmem_file_scope(),
app_secret->data,
secret->data_len);
ssl_data_set(app_secret, secret->data, secret->data_len);
} else {
wmem_free(wmem_file_scope(), app_secret->data);
app_secret->data = NULL;
app_secret->data_len = 0;
}
}
}
/**
* Update to next application data traffic secret for TLS 1.3. The previous
* secret should have been set by tls13_change_key.
*/
void
tls13_key_update(SslDecryptSession *ssl, gboolean is_from_server)
{
/* https://tools.ietf.org/html/draft-ietf-tls-tls13-18#section-7.2
* traffic_secret_N+1 = HKDF-Expand-Label(
* traffic_secret_N,
* "application traffic secret", "", Hash.length)
*
* Note that traffic_secret_N is of the same length (Hash.length).
*/
const SslCipherSuite *cipher_suite = ssl->cipher_suite;
SslDecoder *decoder = is_from_server ? ssl->server : ssl->client;
StringInfo *app_secret = decoder ? &decoder->app_traffic_secret : NULL;
if (!cipher_suite || !app_secret || app_secret->data_len == 0) {
ssl_debug_printf("%s Cannot perform Key Update due to missing info\n", G_STRFUNC);
return;
}
/*
* Previous traffic secret is available, so find the hash function,
* expand the new traffic secret and generate new keys.
*/
const char *hash_name = ssl_cipher_suite_dig(cipher_suite)->name;
int hash_algo = ssl_get_digest_by_name(hash_name);
const guint hash_len = app_secret->data_len;
guchar *new_secret;
if (!tls13_hkdf_expand_label(hash_algo, app_secret, "application traffic secret", "",
hash_len, &new_secret)) {
ssl_debug_printf("%s traffic_secret_N+1 expansion failed\n", G_STRFUNC);
return;
}
ssl_data_set(app_secret, new_secret, hash_len);
wmem_free(NULL, new_secret);
tls13_generate_keys(ssl, app_secret, is_from_server);
}
#endif /* HAVE_LIBGCRYPT */

10
epan/dissectors/packet-ssl-utils.h
View File

@ -316,6 +316,7 @@ typedef struct _SslDecoder {
guint64 seq; /**< Implicit (TLS) or explicit (DTLS) record sequence number. */
guint16 epoch;
SslFlow *flow;
StringInfo app_traffic_secret; /**< TLS 1.3 application traffic secret (if applicable), wmem file scope. */
} SslDecoder;
#define KEX_DHE_DSS 0x10
@ -412,7 +413,6 @@ typedef struct _SslDecryptSession {
StringInfo server_random;
StringInfo client_random;
StringInfo master_secret;
StringInfo traffic_secret; /**< TLS 1.3 traffic secret, wmem file scope. */
StringInfo handshake_data;
/* the data store for this StringInfo must be allocated explicitly with a capture lifetime scope */
StringInfo pre_master_secret;
@ -632,6 +632,9 @@ ssl_finalize_decryption(SslDecryptSession *ssl, ssl_master_key_map_t *mk_map);
extern void
tls13_change_key(SslDecryptSession *ssl, ssl_master_key_map_t *mk_map,
gboolean is_from_server, TLSRecordType type);
extern void
tls13_key_update(SslDecryptSession *ssl, gboolean is_from_server);
#else /* ! HAVE_LIBGCRYPT */
static inline void
ssl_finalize_decryption(SslDecryptSession *ssl _U_, ssl_master_key_map_t *mk_map _U_)
@ -643,6 +646,11 @@ tls13_change_key(SslDecryptSession *ssl _U_, ssl_master_key_map_t *mk_map _U_,
gboolean is_from_server _U_, TLSRecordType type _U_)
{
}
static inline void
tls13_key_update(SslDecryptSession *ssl _U_, gboolean is_from_server _U_)
{
}
#endif /* ! HAVE_LIBGCRYPT */
extern gboolean

3
epan/dissectors/packet-ssl.c
View File

@ -2190,6 +2190,9 @@ dissect_ssl3_handshake(tvbuff_t *tvb, packet_info *pinfo,
case SSL_HND_KEY_UPDATE:
tls13_dissect_hnd_key_update(&dissect_ssl3_hf, tvb, tree, offset);
if (ssl) {
tls13_key_update(ssl, is_from_server);
}
break;
case SSL_HND_ENCRYPTED_EXTS: