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See http://spamassassin.org/tag/ for more details. -0.0 SPF_PASS SPF: sender matches SPF record X-Headers-End: 1gA9LN-004m9D-If Subject: [Openvpn-devel] [PATCH v6 3/7] tls-crypt-v2: generate tls-crypt-v2 keys X-BeenThere: openvpn-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: openvpn-devel-bounces@lists.sourceforge.net X-getmail-retrieved-from-mailbox: Inbox As a first step towards a full tls-crypt-v2 implementation, add functionality to generate tls-crypt-v2 client and server keys. Signed-off-by: Steffan Karger --- v3: Include length in WKc v4: Fix option verification (use ce->tls_*, not options->ce.tls_*) v5: Rebase on patch set v5 v6: - Reword commit message - Fix base64 length calculation - Change WKc length to ciphertext length (instead of plaintext length) doc/openvpn.8 | 51 +++++++++ src/openvpn/base64.h | 4 + src/openvpn/init.c | 33 +++++- src/openvpn/integer.h | 10 ++ src/openvpn/options.c | 69 +++++++++++- src/openvpn/options.h | 14 +++ src/openvpn/tls_crypt.c | 290 ++++++++++++++++++++++++++++++++++++++++++++++++ src/openvpn/tls_crypt.h | 83 ++++++++++++-- tests/t_lpback.sh | 40 ++++++- 9 files changed, 574 insertions(+), 20 deletions(-) diff --git a/doc/openvpn.8 b/doc/openvpn.8 index e94ab76..490bbca 100644 --- a/doc/openvpn.8 +++ b/doc/openvpn.8 @@ -5248,6 +5248,57 @@ degrading to the same security as using That is, the control channel still benefits from the extra protection against active man\-in\-the\-middle\-attacks and DoS attacks, but may no longer offer extra privacy and post\-quantum security on top of what TLS itself offers. + +For large setups or setups where clients are not trusted, consider using +.B \-\-tls\-crypt\-v2 +instead. That uses per\-client unique keys, and thereby improves the bounds to +\fR'rotate a client key at least once per 8000 years'. +.\"********************************************************* +.TP +.B \-\-tls\-crypt\-v2 keyfile + +Use client\-specific tls\-crypt keys. + +For clients, +.B keyfile +is a client\-specific tls\-crypt key. Such a key can be generated using the +.B \-\-tls\-crypt\-v2\-genkey +option. + +For servers, +.B keyfile +is used to unwrap client\-specific keys supplied by the client during connection +setup. This key must be the same as the key used to generate the +client\-specific key (see +.B \-\-tls\-crypt\-v2\-genkey\fR). + +On servers, this option can be used together with the +.B \-\-tls\-auth +or +.B \-\-tls\-crypt +option. In that case, the server will detect whether the client is using +client\-specific keys, and automatically select the right mode. +.\"********************************************************* +.TP +.B \-\-tls\-crypt\-v2\-genkey client|server keyfile [metadata] + +If the first parameter equals "server", generate a \-\-tls\-crypt\-v2 server +key and store the key in +.B keyfile\fR. + + +If the first parameter equals "client", generate a \-\-tls\-crypt\-v2 client +key, and store the key in +.B keyfile\fR. + +If supplied, include the supplied +.B metadata +in the wrapped client key. This metadata must be supplied in base64\-encoded +form. The metadata must be at most 735 bytes long (980 bytes in base64). + +.B TODO +Metadata handling is not yet implemented. This text will be updated by the +commit that introduces metadata handling. .\"********************************************************* .TP .B \-\-askpass [file] diff --git a/src/openvpn/base64.h b/src/openvpn/base64.h index 5679bc9..f49860f 100644 --- a/src/openvpn/base64.h +++ b/src/openvpn/base64.h @@ -34,6 +34,10 @@ #ifndef _BASE64_H_ #define _BASE64_H_ +/** Compute resulting base64 length. 6 bits per byte, padded to 4 bytes. */ +#define OPENVPN_BASE64_LENGTH(binary_length) \ + ((((8 * binary_length) / 6) + 3) & ~3) + int openvpn_base64_encode(const void *data, int size, char **str); int openvpn_base64_decode(const char *str, void *data, int size); diff --git a/src/openvpn/init.c b/src/openvpn/init.c index 52c64da..ade1035 100644 --- a/src/openvpn/init.c +++ b/src/openvpn/init.c @@ -1051,6 +1051,11 @@ print_openssl_info(const struct options *options) bool do_genkey(const struct options *options) { + /* should we disable paging? */ + if (options->mlock && (options->genkey || options->tls_crypt_v2_genkey_file)) + { + platform_mlockall(true); + } if (options->genkey) { int nbits_written; @@ -1058,11 +1063,6 @@ do_genkey(const struct options *options) notnull(options->shared_secret_file, "shared secret output file (--secret)"); - if (options->mlock) /* should we disable paging? */ - { - platform_mlockall(true); - } - nbits_written = write_key_file(2, options->shared_secret_file); if (nbits_written < 0) { @@ -1074,6 +1074,29 @@ do_genkey(const struct options *options) options->shared_secret_file); return true; } + if (options->tls_crypt_v2_genkey_type) + { + if(!strcmp(options->tls_crypt_v2_genkey_type, "server")) + { + tls_crypt_v2_write_server_key_file(options->tls_crypt_v2_genkey_file); + return true; + } + if (options->tls_crypt_v2_genkey_type + && !strcmp(options->tls_crypt_v2_genkey_type, "client")) + { + if (!options->tls_crypt_v2_file) + { + msg(M_USAGE, "--tls-crypt-v2-gen-client-key requires a server key to be set via --tls-crypt-v2"); + } + + tls_crypt_v2_write_client_key_file(options->tls_crypt_v2_genkey_file, + options->tls_crypt_v2_metadata, options->tls_crypt_v2_file, + options->tls_crypt_v2_inline); + return true; + } + + msg(M_USAGE, "--tls-crypt-v2-genkey type should be \"client\" or \"server\""); + } return false; } diff --git a/src/openvpn/integer.h b/src/openvpn/integer.h index a7e19d3..b1ae0ed 100644 --- a/src/openvpn/integer.h +++ b/src/openvpn/integer.h @@ -26,6 +26,16 @@ #include "error.h" +#ifndef htonll +#define htonll(x) ((1==htonl(1)) ? (x) : \ + ((uint64_t)htonl((x) & 0xFFFFFFFF) << 32) | htonl((x) >> 32)) +#endif + +#ifndef ntohll +#define ntohll(x) ((1==ntohl(1)) ? (x) : \ + ((uint64_t)ntohl((x) & 0xFFFFFFFF) << 32) | ntohl((x) >> 32)) +#endif + /* * min/max functions */ diff --git a/src/openvpn/options.c b/src/openvpn/options.c index e42029c..fa638f1 100644 --- a/src/openvpn/options.c +++ b/src/openvpn/options.c @@ -622,6 +622,13 @@ static const char usage_message[] = " attacks on the TLS stack and DoS attacks.\n" " key (required) provides the pre-shared key file.\n" " see --secret option for more info.\n" + "--tls-crypt-v2 key : For clients: use key as a client-specific tls-crypt key.\n" + " For servers: use key to decrypt client-specific keys. For\n" + " key generation (--tls-crypt-v2-genkey): use key to\n" + " encrypt generated client-specific key. (See --tls-crypt.)\n" + "--tls-crypt-v2-genkey client|server keyfile [base64 metadata]: Generate a\n" + " fresh tls-crypt-v2 client or server key, and store to\n" + " keyfile. If supplied, include metadata in wrapped key.\n" "--askpass [file]: Get PEM password from controlling tty before we daemonize.\n" "--auth-nocache : Don't cache --askpass or --auth-user-pass passwords.\n" "--crl-verify crl ['dir']: Check peer certificate against a CRL.\n" @@ -1510,6 +1517,7 @@ show_connection_entry(const struct connection_entry *o) SHOW_PARM(key_direction, keydirection2ascii(o->key_direction, false, true), "%s"); SHOW_STR(tls_crypt_file); + SHOW_STR(tls_crypt_v2_file); } @@ -1790,6 +1798,10 @@ show_settings(const struct options *o) SHOW_BOOL(push_peer_info); SHOW_BOOL(tls_exit); + SHOW_STR(tls_crypt_v2_genkey_type); + SHOW_STR(tls_crypt_v2_genkey_file); + SHOW_STR(tls_crypt_v2_metadata); + #ifdef ENABLE_PKCS11 { int i; @@ -2728,6 +2740,15 @@ options_postprocess_verify_ce(const struct options *options, const struct connec { msg(M_USAGE, "--tls-auth and --tls-crypt are mutually exclusive"); } + if (options->tls_client && ce->tls_crypt_v2_file + && (ce->tls_auth_file || ce->tls_crypt_file)) + { + msg(M_USAGE, "--tls-crypt-v2, --tls-auth and --tls-crypt are mutually exclusive in client mode"); + } + if (options->genkey && options->tls_crypt_v2_genkey_type) + { + msg(M_USAGE, "--genkey and --tls-crypt-v2-genkey are mutually exclusive"); + } } else { @@ -2762,6 +2783,7 @@ options_postprocess_verify_ce(const struct options *options, const struct connec MUST_BE_UNDEF(transition_window); MUST_BE_UNDEF(tls_auth_file); MUST_BE_UNDEF(tls_crypt_file); + MUST_BE_UNDEF(tls_crypt_v2_file); MUST_BE_UNDEF(single_session); MUST_BE_UNDEF(push_peer_info); MUST_BE_UNDEF(tls_exit); @@ -2871,12 +2893,12 @@ options_postprocess_mutate_ce(struct options *o, struct connection_entry *ce) } /* - * Set per-connection block tls-auth/crypt fields if undefined. + * Set per-connection block tls-auth/crypt/crypto-v2 fields if undefined. * - * At the end only one of the two will be really set because the parser - * logic prevents configurations where both are set. + * At the end only one of these will be really set because the parser + * logic prevents configurations where more are set. */ - if (!ce->tls_auth_file && !ce->tls_crypt_file) + if (!ce->tls_auth_file && !ce->tls_crypt_file && !ce->tls_crypt_v2_file) { ce->tls_auth_file = o->tls_auth_file; ce->tls_auth_file_inline = o->tls_auth_file_inline; @@ -2884,6 +2906,9 @@ options_postprocess_mutate_ce(struct options *o, struct connection_entry *ce) ce->tls_crypt_file = o->tls_crypt_file; ce->tls_crypt_inline = o->tls_crypt_inline; + + ce->tls_crypt_v2_file = o->tls_crypt_v2_file; + ce->tls_crypt_v2_inline = o->tls_crypt_v2_inline; } /* pre-cache tls-auth/crypt key file if persist-key was specified and keys @@ -3340,9 +3365,15 @@ options_postprocess_filechecks(struct options *options) errs |= check_file_access(CHKACC_FILE|CHKACC_INLINE|CHKACC_PRIVATE, ce->tls_crypt_file, R_OK, "--tls-crypt"); + errs |= check_file_access(CHKACC_FILE|CHKACC_INLINE|CHKACC_PRIVATE, + ce->tls_crypt_v2_file, R_OK, + "--tls-crypt-v2"); } errs |= check_file_access(CHKACC_FILE|CHKACC_INLINE|CHKACC_PRIVATE, + options->tls_crypt_v2_genkey_file, R_OK, + "--tls-crypt-v2-genkey"); + errs |= check_file_access(CHKACC_FILE|CHKACC_INLINE|CHKACC_PRIVATE, options->shared_secret_file, R_OK, "--secret"); errs |= check_file_access(CHKACC_DIRPATH|CHKACC_FILEXSTWR, @@ -8124,6 +8155,36 @@ add_option(struct options *options, } } + else if (streq(p[0], "tls-crypt-v2") && p[1] && !p[3]) + { + VERIFY_PERMISSION(OPT_P_GENERAL|OPT_P_CONNECTION); + if (permission_mask & OPT_P_GENERAL) + { + if (streq(p[1], INLINE_FILE_TAG) && p[2]) + { + options->tls_crypt_v2_inline = p[2]; + } + options->tls_crypt_v2_file = p[1]; + } + else if (permission_mask & OPT_P_CONNECTION) + { + if (streq(p[1], INLINE_FILE_TAG) && p[2]) + { + options->ce.tls_crypt_v2_inline = p[2]; + } + options->ce.tls_crypt_v2_file = p[1]; + } + } + else if (streq(p[0], "tls-crypt-v2-genkey") && p[2] && !p[4]) + { + VERIFY_PERMISSION(OPT_P_GENERAL); + options->tls_crypt_v2_genkey_type = p[1]; + options->tls_crypt_v2_genkey_file = p[2]; + if (p[3]) + { + options->tls_crypt_v2_metadata = p[3]; + } + } else if (streq(p[0], "key-method") && p[1] && !p[2]) { int key_method; diff --git a/src/openvpn/options.h b/src/openvpn/options.h index acbd108..3d2c770 100644 --- a/src/openvpn/options.h +++ b/src/openvpn/options.h @@ -139,6 +139,11 @@ struct connection_entry /* Shared secret used for TLS control channel authenticated encryption */ const char *tls_crypt_file; const char *tls_crypt_inline; + + /* Client-specific secret or server key used for TLS control channel + * authenticated encryption v2 */ + const char *tls_crypt_v2_file; + const char *tls_crypt_v2_inline; }; struct remote_entry @@ -576,6 +581,15 @@ struct options const char *tls_crypt_file; const char *tls_crypt_inline; + /* Client-specific secret or server key used for TLS control channel + * authenticated encryption v2 */ + const char *tls_crypt_v2_file; + const char *tls_crypt_v2_inline; + + const char *tls_crypt_v2_genkey_type; + const char *tls_crypt_v2_genkey_file; + const char *tls_crypt_v2_metadata; + /* Allow only one session */ bool single_session; diff --git a/src/openvpn/tls_crypt.c b/src/openvpn/tls_crypt.c index 36ead84..25212a1 100644 --- a/src/openvpn/tls_crypt.c +++ b/src/openvpn/tls_crypt.c @@ -29,11 +29,21 @@ #include "syshead.h" +#include "base64.h" #include "crypto.h" +#include "platform.h" #include "session_id.h" #include "tls_crypt.h" +const char *tls_crypt_v2_cli_pem_name = "OpenVPN tls-crypt-v2 client key"; +const char *tls_crypt_v2_srv_pem_name = "OpenVPN tls-crypt-v2 server key"; + +/** Metadata contains user-specified data */ +static const uint8_t TLS_CRYPT_METADATA_TYPE_USER = 0x00; +/** Metadata contains a 64-bit unix timestamp in network byte order */ +static const uint8_t TLS_CRYPT_METADATA_TYPE_TIMESTAMP = 0x01; + static struct key_type tls_crypt_kt(void) { @@ -264,3 +274,283 @@ error_exit: gc_free(&gc); return false; } + +static inline bool +tls_crypt_v2_read_keyfile(struct buffer *key, const char *pem_name, + const char *key_file, const char *key_inline) +{ + bool ret = false; + struct buffer key_pem = { 0 }; + struct gc_arena gc = gc_new(); + + if (strcmp(key_file, INLINE_FILE_TAG)) + { + key_pem = buffer_read_from_file(key_file, &gc); + if (!buf_valid(&key_pem)) + { + msg(M_WARN, "ERROR: failed to read tls-crypt-v2 key file (%s)", + key_file); + goto cleanup; + } + } + else + { + buf_set_read(&key_pem, (const void *)key_inline, strlen(key_inline)); + } + + if (!crypto_pem_decode(pem_name, key, &key_pem)) + { + msg(M_WARN, "ERROR: tls-crypt-v2 pem decode failed"); + goto cleanup; + } + + ret = true; +cleanup: + if (strcmp(key_file, INLINE_FILE_TAG)) + { + buf_clear(&key_pem); + } + gc_free(&gc); + return ret; +} + +static inline void +tls_crypt_v2_load_client_key(struct key_ctx_bi *key, const struct key2 *key2, + bool tls_server) +{ + const int key_direction = tls_server ? + KEY_DIRECTION_NORMAL : KEY_DIRECTION_INVERSE; + struct key_type kt = tls_crypt_kt(); + if (!kt.cipher || !kt.digest) + { + msg(M_FATAL, "ERROR: --tls-crypt-v2 not supported"); + } + init_key_ctx_bi(key, key2, key_direction, &kt, + "Control Channel Encryption"); +} + +void +tls_crypt_v2_init_client_key(struct key_ctx_bi *key, struct buffer *wkc_buf, + const char *key_file, const char *key_inline) +{ + struct buffer client_key = alloc_buf(TLS_CRYPT_V2_CLIENT_KEY_LEN + + TLS_CRYPT_V2_MAX_WKC_LEN); + + if (!tls_crypt_v2_read_keyfile(&client_key, tls_crypt_v2_cli_pem_name, + key_file, key_inline)) + { + msg(M_FATAL, "ERROR: invalid tls-crypt-v2 client key format"); + } + + struct key2 key2; + if (!buf_read(&client_key, &key2.keys, sizeof(key2.keys))) + { + msg(M_FATAL, "ERROR: not enough data in tls-crypt-v2 client key"); + } + + tls_crypt_v2_load_client_key(key, &key2, false); + secure_memzero(&key2, sizeof(key2)); + + *wkc_buf = client_key; +} + +void +tls_crypt_v2_init_server_key(struct key_ctx *key_ctx, bool encrypt, + const char *key_file, const char *key_inline) +{ + struct key srv_key; + struct buffer srv_key_buf; + + buf_set_write(&srv_key_buf, (void *)&srv_key, sizeof(srv_key)); + if (!tls_crypt_v2_read_keyfile(&srv_key_buf, tls_crypt_v2_srv_pem_name, + key_file, key_inline)) + { + msg(M_FATAL, "ERROR: invalid tls-crypt-v2 server key format"); + } + + struct key_type kt = tls_crypt_kt(); + if (!kt.cipher || !kt.digest) + { + msg(M_FATAL, "ERROR: --tls-crypt-v2 not supported"); + } + init_key_ctx(key_ctx, &srv_key, &kt, encrypt, "tls-crypt-v2 server key"); + secure_memzero(&srv_key, sizeof(srv_key)); +} + +static bool +tls_crypt_v2_wrap_client_key(struct buffer *wkc, + const struct key2 *src_key, + const struct buffer *src_metadata, + struct key_ctx *server_key, struct gc_arena *gc) +{ + cipher_ctx_t *cipher_ctx = server_key->cipher; + struct buffer work = alloc_buf_gc(TLS_CRYPT_V2_MAX_WKC_LEN + + cipher_ctx_block_size(cipher_ctx), gc); + + /* Calculate auth tag and synthetic IV */ + uint8_t *tag = buf_write_alloc(&work, TLS_CRYPT_TAG_SIZE); + if (!tag) + { + msg(M_WARN, "ERROR: could not write tag"); + return false; + } + uint16_t net_len = htons(sizeof(src_key->keys) + BLEN(src_metadata) + + TLS_CRYPT_V2_TAG_SIZE + sizeof(uint16_t)); + hmac_ctx_t *hmac_ctx = server_key->hmac; + hmac_ctx_reset(hmac_ctx); + hmac_ctx_update(hmac_ctx, (void *)&net_len, sizeof(net_len)); + hmac_ctx_update(hmac_ctx, (void *)src_key->keys, sizeof(src_key->keys)); + hmac_ctx_update(hmac_ctx, BPTR(src_metadata), BLEN(src_metadata)); + hmac_ctx_final(hmac_ctx, tag); + + dmsg(D_CRYPTO_DEBUG, "TLS-CRYPT WRAP TAG: %s", + format_hex(tag, TLS_CRYPT_TAG_SIZE, 0, gc)); + + /* Use the 128 most significant bits of the tag as IV */ + ASSERT(cipher_ctx_reset(cipher_ctx, tag)); + + /* Overflow check (OpenSSL requires an extra block in the dst buffer) */ + if (buf_forward_capacity(&work) < (sizeof(src_key->keys) + + BLEN(src_metadata) + + sizeof(net_len) + + cipher_ctx_block_size(cipher_ctx))) + { + msg(M_WARN, "ERROR: could not crypt: insufficient space in dst"); + return false; + } + + /* Encrypt */ + int outlen = 0; + ASSERT(cipher_ctx_update(cipher_ctx, BEND(&work), &outlen, + (void *)src_key->keys, sizeof(src_key->keys))); + ASSERT(buf_inc_len(&work, outlen)); + ASSERT(cipher_ctx_update(cipher_ctx, BEND(&work), &outlen, + BPTR(src_metadata), BLEN(src_metadata))); + ASSERT(buf_inc_len(&work, outlen)); + ASSERT(cipher_ctx_final(cipher_ctx, BEND(&work), &outlen)); + ASSERT(buf_inc_len(&work, outlen)); + ASSERT(buf_write(&work, &net_len, sizeof(net_len))); + + return buf_copy(wkc, &work); +} + +void +tls_crypt_v2_write_server_key_file(const char *filename) +{ + struct gc_arena gc = gc_new(); + struct key server_key = { 0 }; + struct buffer server_key_buf = clear_buf(); + struct buffer server_key_pem = clear_buf(); + + if (!rand_bytes((void *)&server_key, sizeof(server_key))) + { + msg(M_NONFATAL, "ERROR: could not generate random key"); + goto cleanup; + } + buf_set_read(&server_key_buf, (void *)&server_key, sizeof(server_key)); + if (!crypto_pem_encode(tls_crypt_v2_srv_pem_name, &server_key_pem, + &server_key_buf, &gc)) + { + msg(M_WARN, "ERROR: could not PEM-encode server key"); + goto cleanup; + } + + if (!buffer_write_file(filename, &server_key_pem)) + { + msg(M_ERR, "ERROR: could not write server key file"); + goto cleanup; + } + +cleanup: + secure_memzero(&server_key, sizeof(server_key)); + buf_clear(&server_key_pem); + gc_free(&gc); + return; +} + +void +tls_crypt_v2_write_client_key_file(const char *filename, + const char *b64_metadata, + const char *server_key_file, + const char *server_key_inline) +{ + struct gc_arena gc = gc_new(); + struct key_ctx server_key = { 0 }; + struct buffer client_key_pem = { 0 }; + struct buffer dst = alloc_buf_gc(TLS_CRYPT_V2_CLIENT_KEY_LEN + + TLS_CRYPT_V2_MAX_WKC_LEN, &gc); + struct key2 client_key = { 2 }; + + if (!rand_bytes((void *)client_key.keys, sizeof(client_key.keys))) + { + msg(M_FATAL, "ERROR: could not generate random key"); + goto cleanup; + } + ASSERT(buf_write(&dst, client_key.keys, sizeof(client_key.keys))); + + struct buffer metadata = alloc_buf_gc(TLS_CRYPT_V2_MAX_METADATA_LEN, &gc); + if (b64_metadata) + { + if (TLS_CRYPT_V2_MAX_B64_METADATA_LEN < strlen(b64_metadata)) + { + msg(M_FATAL, + "ERROR: metadata too long (%d bytes, max %u bytes)", + (int) strlen(b64_metadata), TLS_CRYPT_V2_MAX_B64_METADATA_LEN); + } + ASSERT(buf_write(&metadata, &TLS_CRYPT_METADATA_TYPE_USER, 1)); + int decoded_len = openvpn_base64_decode(b64_metadata, BPTR(&metadata), + BCAP(&metadata)); + if (decoded_len < 0) + { + msg(M_FATAL, "ERROR: failed to base64 decode provided metadata"); + goto cleanup; + } + ASSERT(buf_inc_len(&metadata, decoded_len)); + } + else + { + int64_t timestamp = htonll(now); + ASSERT(buf_write(&metadata, &TLS_CRYPT_METADATA_TYPE_TIMESTAMP, 1)); + ASSERT(buf_write(&metadata, ×tamp, sizeof(timestamp))); + } + + tls_crypt_v2_init_server_key(&server_key, true, server_key_file, + server_key_inline); + if (!tls_crypt_v2_wrap_client_key(&dst, &client_key, &metadata, &server_key, + &gc)) + { + msg(M_FATAL, "ERROR: could not wrap generated client key"); + goto cleanup; + } + + /* PEM-encode Kc || WKc */ + if (!crypto_pem_encode(tls_crypt_v2_cli_pem_name, &client_key_pem, &dst, + &gc)) + { + msg(M_FATAL, "ERROR: could not PEM-encode client key"); + goto cleanup; + } + + if (!buffer_write_file(filename, &client_key_pem)) + { + msg(M_FATAL, "ERROR: could not write client key file"); + goto cleanup; + } + + /* Sanity check: load client key (as "client") */ + struct key_ctx_bi test_client_key; + struct buffer test_wrapped_client_key; + msg(D_GENKEY, "Testing client-side key loading..."); + tls_crypt_v2_init_client_key(&test_client_key, &test_wrapped_client_key, + filename, NULL); + free_key_ctx_bi(&test_client_key); + free_buf(&test_wrapped_client_key); + +cleanup: + secure_memzero(&client_key, sizeof(client_key)); + free_key_ctx(&server_key); + buf_clear(&client_key_pem); + buf_clear(&dst); + + gc_free(&gc); +} diff --git a/src/openvpn/tls_crypt.h b/src/openvpn/tls_crypt.h index 067758c..f888c79 100644 --- a/src/openvpn/tls_crypt.h +++ b/src/openvpn/tls_crypt.h @@ -22,15 +22,13 @@ */ /** - * @defgroup tls_crypt Control channel encryption (--tls-crypt) + * @defgroup tls_crypt Control channel encryption (--tls-crypt, --tls-crypt-v2) * @ingroup control_tls * @{ * - * @par * Control channel encryption uses a pre-shared static key (like the --tls-auth * key) to encrypt control channel packets. * - * @par * Encrypting control channel packets has three main advantages: * - It provides more privacy by hiding the certificate used for the TLS * connection. @@ -38,11 +36,20 @@ * - It provides "poor-man's" post-quantum security, against attackers who * will never know the pre-shared key (i.e. no forward secrecy). * - * @par Specification + * --tls-crypt uses a tls-auth-style group key, where all servers and clients + * share the same group key. --tls-crypt-v2 adds support for client-specific + * keys, where all servers share the same client-key encryption key, and each + * clients receives a unique client key, both in plaintext and in encrypted + * form. When connecting to a server, the client sends the encrypted key to + * the server in the first packet (P_CONTROL_HARD_RESET_CLIENT_V3). The server + * then decrypts that key, and both parties can use the same client-specific + * key for tls-crypt packets. See doc/tls-crypt-v2.txt for more details. + * + * @par On-the-wire tls-crypt packet specification + * @parblock * Control channel encryption is based on the SIV construction [0], to achieve * nonce misuse-resistant authenticated encryption: * - * @par * \code{.unparsed} * msg = control channel plaintext * header = opcode (1 byte) || session_id (8 bytes) || packet_id (8 bytes) @@ -57,23 +64,23 @@ * output = Header || Tag || Ciph * \endcode * - * @par * This boils down to the following on-the-wire packet format: * - * @par * \code{.unparsed} * - opcode - || - session_id - || - packet_id - || auth_tag || * payload * * \endcode * - * @par * Where * - XXX - means authenticated, and * * XXX * means authenticated and encrypted. + * + * @endparblock */ #ifndef TLSCRYPT_H #define TLSCRYPT_H +#include "base64.h" #include "buffer.h" #include "crypto.h" #include "session_id.h" @@ -86,6 +93,16 @@ #define TLS_CRYPT_OFF_TAG (TLS_CRYPT_OFF_PID + TLS_CRYPT_PID_SIZE) #define TLS_CRYPT_OFF_CT (TLS_CRYPT_OFF_TAG + TLS_CRYPT_TAG_SIZE) +#define TLS_CRYPT_V2_MAX_WKC_LEN (1024) +#define TLS_CRYPT_V2_CLIENT_KEY_LEN (2048 / 8) +#define TLS_CRYPT_V2_SERVER_KEY_LEN (sizeof(struct key)) +#define TLS_CRYPT_V2_TAG_SIZE (TLS_CRYPT_TAG_SIZE) +#define TLS_CRYPT_V2_MAX_METADATA_LEN (unsigned)(TLS_CRYPT_V2_MAX_WKC_LEN \ + - (TLS_CRYPT_V2_CLIENT_KEY_LEN + TLS_CRYPT_V2_TAG_SIZE \ + + sizeof(uint16_t))) +#define TLS_CRYPT_V2_MAX_B64_METADATA_LEN \ + OPENVPN_BASE64_LENGTH(TLS_CRYPT_V2_MAX_METADATA_LEN - 1) + /** * Initialize a key_ctx_bi structure for use with --tls-crypt. * @@ -138,6 +155,56 @@ bool tls_crypt_wrap(const struct buffer *src, struct buffer *dst, bool tls_crypt_unwrap(const struct buffer *src, struct buffer *dst, struct crypto_options *opt); +/** + * Initialize a tls-crypt-v2 server key (used to encrypt/decrypt client keys). + * + * @param key Key structure to be initialized. Must be non-NULL. + * @parem encrypt If true, initialize the key structure for encryption, + * otherwise for decryption. + * @param key_file File path of the key file to load, or INLINE tag. + * @param key_inline Inline key file contents (or NULL if not inline). + */ +void tls_crypt_v2_init_server_key(struct key_ctx *key_ctx, bool encrypt, + const char *key_file, const char *key_inline); + +/** + * Initialize a tls-crypt-v2 client key. + * + * @param key Key structure to be initialized with the client + * key. + * @param wrapped_key_buf Returns buffer containing the wrapped key that will + * be sent to the server when connecting. Caller must + * free this buffer when no longer needed. + * @param key_file File path of the key file to load, or INLINE tag. + * @param key_inline Inline key file contents (or NULL if not inline). + */ +void tls_crypt_v2_init_client_key(struct key_ctx_bi *key, + struct buffer *wrapped_key_buf, + const char *key_file, + const char *key_inline); + +/** + * Generate a tls-crypt-v2 server key, and write to file. + * + * @param filename Filename of the server key file to create. + */ +void tls_crypt_v2_write_server_key_file(const char *filename); + +/** + * Generate a tls-crypt-v2 client key, and write to file. + * + * @param filename Filename of the client key file to create. + * @param b64_metadata Base64 metadata to be included in the client key. + * @param server_key_file File path of the server key to use for wrapping the + * client key, or INLINE tag. + * @param server_key_inline Inline server key file contents (or NULL if not + * inline). + */ +void tls_crypt_v2_write_client_key_file(const char *filename, + const char *b64_metadata, + const char *key_file, + const char *key_inline); + /** @} */ #endif /* TLSCRYPT_H */ diff --git a/tests/t_lpback.sh b/tests/t_lpback.sh index 2052c62..fb43211 100755 --- a/tests/t_lpback.sh +++ b/tests/t_lpback.sh @@ -21,8 +21,8 @@ set -eu top_builddir="${top_builddir:-..}" -trap "rm -f key.$$ log.$$ ; trap 0 ; exit 77" 1 2 15 -trap "rm -f key.$$ log.$$ ; exit 1" 0 3 +trap "rm -f key.$$ tc-server-key.$$ tc-client-key.$$ log.$$ ; trap 0 ; exit 77" 1 2 15 +trap "rm -f key.$$ tc-server-key.$$ tc-client-key.$$ log.$$ ; exit 1" 0 3 # Get list of supported ciphers from openvpn --show-ciphers output CIPHERS=$(${top_builddir}/src/openvpn/openvpn --show-ciphers | \ @@ -55,6 +55,40 @@ do fi done -rm key.$$ log.$$ +echo -n "Testing tls-crypt-v2 server key generation..." +"${top_builddir}/src/openvpn/openvpn" \ + --tls-crypt-v2-genkey server tc-server-key.$$ >log.$$ 2>&1 +if [ $? != 0 ] ; then + echo "FAILED" + cat log.$$ + e=1 +else + echo "OK" +fi + +echo -n "Testing tls-crypt-v2 key generation (no metadata)..." +"${top_builddir}/src/openvpn/openvpn" --tls-crypt-v2 tc-server-key.$$ \ + --tls-crypt-v2-genkey client tc-client-key.$$ >log.$$ 2>&1 +if [ $? != 0 ] ; then + echo "FAILED" + cat log.$$ + e=1 +else + echo "OK" +fi + +echo -n "Testing tls-crypt-v2 key generation (max length metadata)..." +"${top_builddir}/src/openvpn/openvpn" --tls-crypt-v2 tc-server-key.$$ \ + --tls-crypt-v2-genkey client tc-client-key.$$ \ + $(head -c732 /dev/zero | base64 -w0) >log.$$ 2>&1 +if [ $? != 0 ] ; then + echo "FAILED" + cat log.$$ + e=1 +else + echo "OK" +fi + +rm key.$$ tc-server-key.$$ tc-client-key.$$ log.$$ trap 0 exit $e