diff options
| -rw-r--r-- | src/openvpn/ssl.c | 36 | ||||
| -rw-r--r-- | src/openvpn/ssl_backend.h | 20 | ||||
| -rw-r--r-- | src/openvpn/ssl_mbedtls.c | 73 | ||||
| -rw-r--r-- | src/openvpn/ssl_mbedtls.h | 12 | ||||
| -rw-r--r-- | src/openvpn/ssl_openssl.c | 43 |
5 files changed, 114 insertions, 70 deletions
diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c index f16114c..3fcaa25 100644 --- a/src/openvpn/ssl.c +++ b/src/openvpn/ssl.c @@ -2412,6 +2412,40 @@ error: return false; } +static void +export_user_keying_material(struct key_state_ssl *ssl, + struct tls_session *session) +{ + if (session->opt->ekm_size > 0) + { + unsigned int size = session->opt->ekm_size; + struct gc_arena gc = gc_new(); + + unsigned char *ekm; + if ((ekm = key_state_export_keying_material(session, + session->opt->ekm_label, + session->opt->ekm_label_size, + session->opt->ekm_size, + &gc))) + { + unsigned int len = (size * 2) + 2; + + const char *key = format_hex_ex(ekm, size, len, 0, NULL, &gc); + setenv_str(session->opt->es, "exported_keying_material", key); + + dmsg(D_TLS_DEBUG_MED, "%s: exported keying material: %s", + __func__, key); + secure_memzero(ekm, size); + } + else + { + msg(M_WARN, "WARNING: Export keying material failed!"); + setenv_del(session->opt->es, "exported_keying_material"); + } + gc_free(&gc); + } +} + /** * Handle reading key data, peer-info, username/password, OCC * from the TLS control channel (cleartext). @@ -2541,7 +2575,7 @@ key_method_2_read(struct buffer *buf, struct tls_multi *multi, struct tls_sessio if ((ks->authenticated > KS_AUTH_FALSE) && plugin_defined(session->opt->plugins, OPENVPN_PLUGIN_TLS_FINAL)) { - key_state_export_keying_material(&ks->ks_ssl, session); + export_user_keying_material(&ks->ks_ssl, session); if (plugin_call(session->opt->plugins, OPENVPN_PLUGIN_TLS_FINAL, NULL, NULL, session->opt->es) != OPENVPN_PLUGIN_FUNC_SUCCESS) { diff --git a/src/openvpn/ssl_backend.h b/src/openvpn/ssl_backend.h index 7f52ab1..cf9fba2 100644 --- a/src/openvpn/ssl_backend.h +++ b/src/openvpn/ssl_backend.h @@ -394,13 +394,21 @@ void backend_tls_ctx_reload_crl(struct tls_root_ctx *ssl_ctx, * derived from existing TLS channel. This exported keying material can then be * used for a variety of purposes. * - * @param ks_ssl The SSL channel's state info * @param session The session associated with the given key_state - */ - -void -key_state_export_keying_material(struct key_state_ssl *ks_ssl, - struct tls_session *session) __attribute__((nonnull)); + * @param label The label to use when exporting the key + * @param label_size The size of the label to use when exporting the key + * @param ekm_size THe size of the exported/returned key material + * @param gc gc_arena that might be used to allocate the string + * returned + * @returns The exported key material, the caller may zero the + * string but should not free it + */ + +unsigned char* +key_state_export_keying_material(struct tls_session *session, + const char* label, size_t label_size, + size_t ekm_size, + struct gc_arena *gc) __attribute__((nonnull)); /**************************************************************************/ /** @addtogroup control_tls diff --git a/src/openvpn/ssl_mbedtls.c b/src/openvpn/ssl_mbedtls.c index 9c87478..4287b59 100644 --- a/src/openvpn/ssl_mbedtls.c +++ b/src/openvpn/ssl_mbedtls.c @@ -206,51 +206,54 @@ mbedtls_ssl_export_keys_cb(void *p_expkey, const unsigned char *ms, { struct tls_session *session = p_expkey; struct key_state_ssl *ks_ssl = &session->key[KS_PRIMARY].ks_ssl; - unsigned char client_server_random[64]; + struct tls_key_cache *cache = &ks_ssl->tls_key_cache; - ks_ssl->exported_key_material = gc_malloc(session->opt->ekm_size, - true, NULL); + static_assert(sizeof(ks_ssl->ctx->session->master) + == sizeof(cache->master_secret), "master size mismatch"); - memcpy(client_server_random, client_random, 32); - memcpy(client_server_random + 32, server_random, 32); + memcpy(cache->client_server_random, client_random, 32); + memcpy(cache->client_server_random + 32, server_random, 32); + memcpy(cache->master_secret, ms, sizeof(cache->master_secret)); + cache->tls_prf_type = tls_prf_type; - const size_t ms_len = sizeof(ks_ssl->ctx->session->master); - int ret = mbedtls_ssl_tls_prf(tls_prf_type, ms, ms_len, - session->opt->ekm_label, client_server_random, - sizeof(client_server_random), ks_ssl->exported_key_material, - session->opt->ekm_size); - - if (!mbed_ok(ret)) - { - secure_memzero(ks_ssl->exported_key_material, session->opt->ekm_size); - } - - secure_memzero(client_server_random, sizeof(client_server_random)); - - return ret; + return true; } -#endif /* HAVE_EXPORT_KEYING_MATERIAL */ -void -key_state_export_keying_material(struct key_state_ssl *ssl, - struct tls_session *session) +unsigned char * +key_state_export_keying_material(struct tls_session *session, + const char* label, size_t label_size, + size_t ekm_size, + struct gc_arena *gc) { - if (ssl->exported_key_material) + ASSERT(strlen(label) == label_size); + + struct tls_key_cache *cache = &session->key[KS_PRIMARY].ks_ssl.tls_key_cache; + + /* If the type is NONE, we either have no cached secrets or + * there is no PRF, in both cases we cannot generate key material */ + if (cache->tls_prf_type == MBEDTLS_SSL_TLS_PRF_NONE) { - unsigned int size = session->opt->ekm_size; - struct gc_arena gc = gc_new(); - unsigned int len = (size * 2) + 2; + return NULL; + } - const char *key = format_hex_ex(ssl->exported_key_material, - size, len, 0, NULL, &gc); - setenv_str(session->opt->es, "exported_keying_material", key); + unsigned char *ekm = (unsigned char *) gc_malloc(ekm_size, true, gc); + int ret = mbedtls_ssl_tls_prf(cache->tls_prf_type, cache->master_secret, + sizeof(cache->master_secret), + label, cache->client_server_random, + sizeof(cache->client_server_random), + ekm, ekm_size); - dmsg(D_TLS_DEBUG_MED, "%s: exported keying material: %s", - __func__, key); - gc_free(&gc); + if (mbed_ok(ret)) + { + return ekm; + } + else + { + secure_memzero(ekm, session->opt->ekm_size); + return NULL; } } - +#endif /* HAVE_EXPORT_KEYING_MATERIAL */ bool tls_ctx_set_options(struct tls_root_ctx *ctx, unsigned int ssl_flags) @@ -1178,7 +1181,7 @@ key_state_ssl_free(struct key_state_ssl *ks_ssl) { if (ks_ssl) { - free(ks_ssl->exported_key_material); + CLEAR(ks_ssl->tls_key_cache); if (ks_ssl->ctx) { diff --git a/src/openvpn/ssl_mbedtls.h b/src/openvpn/ssl_mbedtls.h index 0525134..17aae55 100644 --- a/src/openvpn/ssl_mbedtls.h +++ b/src/openvpn/ssl_mbedtls.h @@ -82,6 +82,15 @@ struct external_context { void *sign_ctx; }; +/** struct to cache TLS secrets for keying material exporter (RFC 5705). + * The constants (64 and 48) are inherent to TLS version and + * the whole keying material export will likely change when they change */ +struct tls_key_cache { + unsigned char client_server_random[64]; + mbedtls_tls_prf_types tls_prf_type; + unsigned char master_secret[48]; +}; + /** * Structure that wraps the TLS context. Contents differ depending on the * SSL library used. @@ -114,8 +123,7 @@ struct key_state_ssl { mbedtls_ssl_context *ctx; /**< mbedTLS connection context */ bio_ctx *bio_ctx; - /** Keying material exporter cache (RFC 5705). */ - uint8_t *exported_key_material; + struct tls_key_cache tls_key_cache; }; diff --git a/src/openvpn/ssl_openssl.c b/src/openvpn/ssl_openssl.c index 5ba7440..f52c7c3 100644 --- a/src/openvpn/ssl_openssl.c +++ b/src/openvpn/ssl_openssl.c @@ -158,35 +158,26 @@ tls_ctx_initialised(struct tls_root_ctx *ctx) return NULL != ctx->ctx; } -void -key_state_export_keying_material(struct key_state_ssl *ssl, - struct tls_session *session) -{ - if (session->opt->ekm_size > 0) - { - unsigned int size = session->opt->ekm_size; - struct gc_arena gc = gc_new(); - unsigned char *ekm = (unsigned char *) gc_malloc(size, true, &gc); +unsigned char* +key_state_export_keying_material(struct tls_session *session, + const char* label, size_t label_size, + size_t ekm_size, + struct gc_arena *gc) - if (SSL_export_keying_material(ssl->ssl, ekm, size, - session->opt->ekm_label, - session->opt->ekm_label_size, - NULL, 0, 0)) - { - unsigned int len = (size * 2) + 2; +{ + unsigned char *ekm = (unsigned char *) gc_malloc(ekm_size, true, gc); - const char *key = format_hex_ex(ekm, size, len, 0, NULL, &gc); - setenv_str(session->opt->es, "exported_keying_material", key); + SSL* ssl = session->key[KS_PRIMARY].ks_ssl.ssl; - dmsg(D_TLS_DEBUG_MED, "%s: exported keying material: %s", - __func__, key); - } - else - { - msg(M_WARN, "WARNING: Export keying material failed!"); - setenv_del(session->opt->es, "exported_keying_material"); - } - gc_free(&gc); + if (SSL_export_keying_material(ssl, ekm, ekm_size, label, + label_size, NULL, 0, 0) == 1) + { + return ekm; + } + else + { + secure_memzero(ekm, ekm_size); + return NULL; } } |