diff options
Diffstat (limited to 'src/feature/relay/relay_handshake.c')
| -rw-r--r-- | src/feature/relay/relay_handshake.c | 565 |
1 files changed, 565 insertions, 0 deletions
diff --git a/src/feature/relay/relay_handshake.c b/src/feature/relay/relay_handshake.c new file mode 100644 index 0000000000..030dc94956 --- /dev/null +++ b/src/feature/relay/relay_handshake.c @@ -0,0 +1,565 @@ +/* Copyright (c) 2001 Matej Pfajfar. + * Copyright (c) 2001-2004, Roger Dingledine. + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. + * Copyright (c) 2007-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * @file relay_handshake.c + * @brief Functions to implement the relay-only parts of our + * connection handshake. + * + * Some parts of our TLS link handshake are only done by relays (including + * bridges). Specifically, only relays need to send CERTS cells; only + * relays need to send or receive AUTHCHALLENGE cells, and only relays need to + * send or receive AUTHENTICATE cells. + **/ + +#include "orconfig.h" +#include "core/or/or.h" +#include "feature/relay/relay_handshake.h" + +#include "app/config/config.h" +#include "core/or/connection_or.h" +#include "lib/crypt_ops/crypto_rand.h" +#include "trunnel/link_handshake.h" +#include "feature/relay/routerkeys.h" +#include "feature/nodelist/torcert.h" + +#include "core/or/or_connection_st.h" +#include "core/or/or_handshake_certs_st.h" +#include "core/or/or_handshake_state_st.h" +#include "core/or/var_cell_st.h" + +#include "lib/tls/tortls.h" +#include "lib/tls/x509.h" + +/** Helper used to add an encoded certs to a cert cell */ +static void +add_certs_cell_cert_helper(certs_cell_t *certs_cell, + uint8_t cert_type, + const uint8_t *cert_encoded, + size_t cert_len) +{ + tor_assert(cert_len <= UINT16_MAX); + certs_cell_cert_t *ccc = certs_cell_cert_new(); + ccc->cert_type = cert_type; + ccc->cert_len = cert_len; + certs_cell_cert_setlen_body(ccc, cert_len); + memcpy(certs_cell_cert_getarray_body(ccc), cert_encoded, cert_len); + + certs_cell_add_certs(certs_cell, ccc); +} + +/** Add an encoded X509 cert (stored as <b>cert_len</b> bytes at + * <b>cert_encoded</b>) to the trunnel certs_cell_t object that we are + * building in <b>certs_cell</b>. Set its type field to <b>cert_type</b>. + * (If <b>cert</b> is NULL, take no action.) */ +static void +add_x509_cert(certs_cell_t *certs_cell, + uint8_t cert_type, + const tor_x509_cert_t *cert) +{ + if (NULL == cert) + return; + + const uint8_t *cert_encoded = NULL; + size_t cert_len; + tor_x509_cert_get_der(cert, &cert_encoded, &cert_len); + + add_certs_cell_cert_helper(certs_cell, cert_type, cert_encoded, cert_len); +} + +/** Add an Ed25519 cert from <b>cert</b> to the trunnel certs_cell_t object + * that we are building in <b>certs_cell</b>. Set its type field to + * <b>cert_type</b>. (If <b>cert</b> is NULL, take no action.) */ +static void +add_ed25519_cert(certs_cell_t *certs_cell, + uint8_t cert_type, + const tor_cert_t *cert) +{ + if (NULL == cert) + return; + + add_certs_cell_cert_helper(certs_cell, cert_type, + cert->encoded, cert->encoded_len); +} + +#ifdef TOR_UNIT_TESTS +int certs_cell_ed25519_disabled_for_testing = 0; +#else +#define certs_cell_ed25519_disabled_for_testing 0 +#endif + +/** Send a CERTS cell on the connection <b>conn</b>. Return 0 on success, -1 + * on failure. */ +int +connection_or_send_certs_cell(or_connection_t *conn) +{ + const tor_x509_cert_t *global_link_cert = NULL, *id_cert = NULL; + tor_x509_cert_t *own_link_cert = NULL; + var_cell_t *cell; + + certs_cell_t *certs_cell = NULL; + + tor_assert(conn->base_.state == OR_CONN_STATE_OR_HANDSHAKING_V3); + + if (! conn->handshake_state) + return -1; + + const int conn_in_server_mode = ! conn->handshake_state->started_here; + + /* Get the encoded values of the X509 certificates */ + if (tor_tls_get_my_certs(conn_in_server_mode, + &global_link_cert, &id_cert) < 0) + return -1; + + if (conn_in_server_mode) { + own_link_cert = tor_tls_get_own_cert(conn->tls); + } + tor_assert(id_cert); + + certs_cell = certs_cell_new(); + + /* Start adding certs. First the link cert or auth1024 cert. */ + if (conn_in_server_mode) { + tor_assert_nonfatal(own_link_cert); + add_x509_cert(certs_cell, + OR_CERT_TYPE_TLS_LINK, own_link_cert); + } else { + tor_assert(global_link_cert); + add_x509_cert(certs_cell, + OR_CERT_TYPE_AUTH_1024, global_link_cert); + } + + /* Next the RSA->RSA ID cert */ + add_x509_cert(certs_cell, + OR_CERT_TYPE_ID_1024, id_cert); + + /* Next the Ed25519 certs */ + add_ed25519_cert(certs_cell, + CERTTYPE_ED_ID_SIGN, + get_master_signing_key_cert()); + if (conn_in_server_mode) { + tor_assert_nonfatal(conn->handshake_state->own_link_cert || + certs_cell_ed25519_disabled_for_testing); + add_ed25519_cert(certs_cell, + CERTTYPE_ED_SIGN_LINK, + conn->handshake_state->own_link_cert); + } else { + add_ed25519_cert(certs_cell, + CERTTYPE_ED_SIGN_AUTH, + get_current_auth_key_cert()); + } + + /* And finally the crosscert. */ + { + const uint8_t *crosscert=NULL; + size_t crosscert_len; + get_master_rsa_crosscert(&crosscert, &crosscert_len); + if (crosscert) { + add_certs_cell_cert_helper(certs_cell, + CERTTYPE_RSA1024_ID_EDID, + crosscert, crosscert_len); + } + } + + /* We've added all the certs; make the cell. */ + certs_cell->n_certs = certs_cell_getlen_certs(certs_cell); + + ssize_t alloc_len = certs_cell_encoded_len(certs_cell); + tor_assert(alloc_len >= 0 && alloc_len <= UINT16_MAX); + cell = var_cell_new(alloc_len); + cell->command = CELL_CERTS; + ssize_t enc_len = certs_cell_encode(cell->payload, alloc_len, certs_cell); + tor_assert(enc_len > 0 && enc_len <= alloc_len); + cell->payload_len = enc_len; + + connection_or_write_var_cell_to_buf(cell, conn); + var_cell_free(cell); + certs_cell_free(certs_cell); + tor_x509_cert_free(own_link_cert); + + return 0; +} + +#ifdef TOR_UNIT_TESTS +int testing__connection_or_pretend_TLSSECRET_is_supported = 0; +#else +#define testing__connection_or_pretend_TLSSECRET_is_supported 0 +#endif + +/** Return true iff <b>challenge_type</b> is an AUTHCHALLENGE type that + * we can send and receive. */ +int +authchallenge_type_is_supported(uint16_t challenge_type) +{ + switch (challenge_type) { + case AUTHTYPE_RSA_SHA256_TLSSECRET: +#ifdef HAVE_WORKING_TOR_TLS_GET_TLSSECRETS + return 1; +#else + return testing__connection_or_pretend_TLSSECRET_is_supported; +#endif + case AUTHTYPE_ED25519_SHA256_RFC5705: + return 1; + case AUTHTYPE_RSA_SHA256_RFC5705: + default: + return 0; + } +} + +/** Return true iff <b>challenge_type_a</b> is one that we would rather + * use than <b>challenge_type_b</b>. */ +int +authchallenge_type_is_better(uint16_t challenge_type_a, + uint16_t challenge_type_b) +{ + /* Any supported type is better than an unsupported one; + * all unsupported types are equally bad. */ + if (!authchallenge_type_is_supported(challenge_type_a)) + return 0; + if (!authchallenge_type_is_supported(challenge_type_b)) + return 1; + /* It happens that types are superior in numerically ascending order. + * If that ever changes, this must change too. */ + return (challenge_type_a > challenge_type_b); +} + +/** Send an AUTH_CHALLENGE cell on the connection <b>conn</b>. Return 0 + * on success, -1 on failure. */ +int +connection_or_send_auth_challenge_cell(or_connection_t *conn) +{ + var_cell_t *cell = NULL; + int r = -1; + tor_assert(conn->base_.state == OR_CONN_STATE_OR_HANDSHAKING_V3); + + if (! conn->handshake_state) + return -1; + + auth_challenge_cell_t *ac = auth_challenge_cell_new(); + + tor_assert(sizeof(ac->challenge) == 32); + crypto_rand((char*)ac->challenge, sizeof(ac->challenge)); + + if (authchallenge_type_is_supported(AUTHTYPE_RSA_SHA256_TLSSECRET)) + auth_challenge_cell_add_methods(ac, AUTHTYPE_RSA_SHA256_TLSSECRET); + /* Disabled, because everything that supports this method also supports + * the much-superior ED25519_SHA256_RFC5705 */ + /* auth_challenge_cell_add_methods(ac, AUTHTYPE_RSA_SHA256_RFC5705); */ + if (authchallenge_type_is_supported(AUTHTYPE_ED25519_SHA256_RFC5705)) + auth_challenge_cell_add_methods(ac, AUTHTYPE_ED25519_SHA256_RFC5705); + auth_challenge_cell_set_n_methods(ac, + auth_challenge_cell_getlen_methods(ac)); + + cell = var_cell_new(auth_challenge_cell_encoded_len(ac)); + ssize_t len = auth_challenge_cell_encode(cell->payload, cell->payload_len, + ac); + if (len != cell->payload_len) { + /* LCOV_EXCL_START */ + log_warn(LD_BUG, "Encoded auth challenge cell length not as expected"); + goto done; + /* LCOV_EXCL_STOP */ + } + cell->command = CELL_AUTH_CHALLENGE; + + connection_or_write_var_cell_to_buf(cell, conn); + r = 0; + + done: + var_cell_free(cell); + auth_challenge_cell_free(ac); + + return r; +} + +/** Compute the main body of an AUTHENTICATE cell that a client can use + * to authenticate itself on a v3 handshake for <b>conn</b>. Return it + * in a var_cell_t. + * + * If <b>server</b> is true, only calculate the first + * V3_AUTH_FIXED_PART_LEN bytes -- the part of the authenticator that's + * determined by the rest of the handshake, and which match the provided value + * exactly. + * + * If <b>server</b> is false and <b>signing_key</b> is NULL, calculate the + * first V3_AUTH_BODY_LEN bytes of the authenticator (that is, everything + * that should be signed), but don't actually sign it. + * + * If <b>server</b> is false and <b>signing_key</b> is provided, calculate the + * entire authenticator, signed with <b>signing_key</b>. + * + * Return the length of the cell body on success, and -1 on failure. + */ +var_cell_t * +connection_or_compute_authenticate_cell_body(or_connection_t *conn, + const int authtype, + crypto_pk_t *signing_key, + const ed25519_keypair_t *ed_signing_key, + int server) +{ + auth1_t *auth = NULL; + auth_ctx_t *ctx = auth_ctx_new(); + var_cell_t *result = NULL; + int old_tlssecrets_algorithm = 0; + const char *authtype_str = NULL; + + int is_ed = 0; + + /* assert state is reasonable XXXX */ + switch (authtype) { + case AUTHTYPE_RSA_SHA256_TLSSECRET: + authtype_str = "AUTH0001"; + old_tlssecrets_algorithm = 1; + break; + case AUTHTYPE_RSA_SHA256_RFC5705: + authtype_str = "AUTH0002"; + break; + case AUTHTYPE_ED25519_SHA256_RFC5705: + authtype_str = "AUTH0003"; + is_ed = 1; + break; + default: + tor_assert(0); + break; + } + + auth = auth1_new(); + ctx->is_ed = is_ed; + + /* Type: 8 bytes. */ + memcpy(auth1_getarray_type(auth), authtype_str, 8); + + { + const tor_x509_cert_t *id_cert=NULL; + const common_digests_t *my_digests, *their_digests; + const uint8_t *my_id, *their_id, *client_id, *server_id; + if (tor_tls_get_my_certs(server, NULL, &id_cert)) + goto err; + my_digests = tor_x509_cert_get_id_digests(id_cert); + their_digests = + tor_x509_cert_get_id_digests(conn->handshake_state->certs->id_cert); + tor_assert(my_digests); + tor_assert(their_digests); + my_id = (uint8_t*)my_digests->d[DIGEST_SHA256]; + their_id = (uint8_t*)their_digests->d[DIGEST_SHA256]; + + client_id = server ? their_id : my_id; + server_id = server ? my_id : their_id; + + /* Client ID digest: 32 octets. */ + memcpy(auth->cid, client_id, 32); + + /* Server ID digest: 32 octets. */ + memcpy(auth->sid, server_id, 32); + } + + if (is_ed) { + const ed25519_public_key_t *my_ed_id, *their_ed_id; + if (!conn->handshake_state->certs->ed_id_sign) { + log_warn(LD_OR, "Ed authenticate without Ed ID cert from peer."); + goto err; + } + my_ed_id = get_master_identity_key(); + their_ed_id = &conn->handshake_state->certs->ed_id_sign->signing_key; + + const uint8_t *cid_ed = (server ? their_ed_id : my_ed_id)->pubkey; + const uint8_t *sid_ed = (server ? my_ed_id : their_ed_id)->pubkey; + + memcpy(auth->u1_cid_ed, cid_ed, ED25519_PUBKEY_LEN); + memcpy(auth->u1_sid_ed, sid_ed, ED25519_PUBKEY_LEN); + } + + { + crypto_digest_t *server_d, *client_d; + if (server) { + server_d = conn->handshake_state->digest_sent; + client_d = conn->handshake_state->digest_received; + } else { + client_d = conn->handshake_state->digest_sent; + server_d = conn->handshake_state->digest_received; + } + + /* Server log digest : 32 octets */ + crypto_digest_get_digest(server_d, (char*)auth->slog, 32); + + /* Client log digest : 32 octets */ + crypto_digest_get_digest(client_d, (char*)auth->clog, 32); + } + + { + /* Digest of cert used on TLS link : 32 octets. */ + tor_x509_cert_t *cert = NULL; + if (server) { + cert = tor_tls_get_own_cert(conn->tls); + } else { + cert = tor_tls_get_peer_cert(conn->tls); + } + if (!cert) { + log_warn(LD_OR, "Unable to find cert when making %s data.", + authtype_str); + goto err; + } + + memcpy(auth->scert, + tor_x509_cert_get_cert_digests(cert)->d[DIGEST_SHA256], 32); + + tor_x509_cert_free(cert); + } + + /* HMAC of clientrandom and serverrandom using master key : 32 octets */ + if (old_tlssecrets_algorithm) { + if (tor_tls_get_tlssecrets(conn->tls, auth->tlssecrets) < 0) { + log_fn(LOG_PROTOCOL_WARN, LD_OR, "Somebody asked us for an older TLS " + "authentication method (AUTHTYPE_RSA_SHA256_TLSSECRET) " + "which we don't support."); + } + } else { + char label[128]; + tor_snprintf(label, sizeof(label), + "EXPORTER FOR TOR TLS CLIENT BINDING %s", authtype_str); + int r = tor_tls_export_key_material(conn->tls, auth->tlssecrets, + auth->cid, sizeof(auth->cid), + label); + if (r < 0) { + if (r != -2) + log_warn(LD_BUG, "TLS key export failed for unknown reason."); + // If r == -2, this was openssl bug 7712. + goto err; + } + } + + /* 8 octets were reserved for the current time, but we're trying to get out + * of the habit of sending time around willynilly. Fortunately, nothing + * checks it. That's followed by 16 bytes of nonce. */ + crypto_rand((char*)auth->rand, 24); + + ssize_t maxlen = auth1_encoded_len(auth, ctx); + if (ed_signing_key && is_ed) { + maxlen += ED25519_SIG_LEN; + } else if (signing_key && !is_ed) { + maxlen += crypto_pk_keysize(signing_key); + } + + const int AUTH_CELL_HEADER_LEN = 4; /* 2 bytes of type, 2 bytes of length */ + result = var_cell_new(AUTH_CELL_HEADER_LEN + maxlen); + uint8_t *const out = result->payload + AUTH_CELL_HEADER_LEN; + const size_t outlen = maxlen; + ssize_t len; + + result->command = CELL_AUTHENTICATE; + set_uint16(result->payload, htons(authtype)); + + if ((len = auth1_encode(out, outlen, auth, ctx)) < 0) { + /* LCOV_EXCL_START */ + log_warn(LD_BUG, "Unable to encode signed part of AUTH1 data."); + goto err; + /* LCOV_EXCL_STOP */ + } + + if (server) { + auth1_t *tmp = NULL; + ssize_t len2 = auth1_parse(&tmp, out, len, ctx); + if (!tmp) { + /* LCOV_EXCL_START */ + log_warn(LD_BUG, "Unable to parse signed part of AUTH1 data that " + "we just encoded"); + goto err; + /* LCOV_EXCL_STOP */ + } + result->payload_len = (tmp->end_of_signed - result->payload); + + auth1_free(tmp); + if (len2 != len) { + /* LCOV_EXCL_START */ + log_warn(LD_BUG, "Mismatched length when re-parsing AUTH1 data."); + goto err; + /* LCOV_EXCL_STOP */ + } + goto done; + } + + if (ed_signing_key && is_ed) { + ed25519_signature_t sig; + if (ed25519_sign(&sig, out, len, ed_signing_key) < 0) { + /* LCOV_EXCL_START */ + log_warn(LD_BUG, "Unable to sign ed25519 authentication data"); + goto err; + /* LCOV_EXCL_STOP */ + } + auth1_setlen_sig(auth, ED25519_SIG_LEN); + memcpy(auth1_getarray_sig(auth), sig.sig, ED25519_SIG_LEN); + + } else if (signing_key && !is_ed) { + auth1_setlen_sig(auth, crypto_pk_keysize(signing_key)); + + char d[32]; + crypto_digest256(d, (char*)out, len, DIGEST_SHA256); + int siglen = crypto_pk_private_sign(signing_key, + (char*)auth1_getarray_sig(auth), + auth1_getlen_sig(auth), + d, 32); + if (siglen < 0) { + log_warn(LD_OR, "Unable to sign AUTH1 data."); + goto err; + } + + auth1_setlen_sig(auth, siglen); + } + + len = auth1_encode(out, outlen, auth, ctx); + if (len < 0) { + /* LCOV_EXCL_START */ + log_warn(LD_BUG, "Unable to encode signed AUTH1 data."); + goto err; + /* LCOV_EXCL_STOP */ + } + tor_assert(len + AUTH_CELL_HEADER_LEN <= result->payload_len); + result->payload_len = len + AUTH_CELL_HEADER_LEN; + set_uint16(result->payload+2, htons(len)); + + goto done; + + err: + var_cell_free(result); + result = NULL; + done: + auth1_free(auth); + auth_ctx_free(ctx); + return result; +} + +/** Send an AUTHENTICATE cell on the connection <b>conn</b>. Return 0 on + * success, -1 on failure */ +MOCK_IMPL(int, +connection_or_send_authenticate_cell,(or_connection_t *conn, int authtype)) +{ + var_cell_t *cell; + crypto_pk_t *pk = tor_tls_get_my_client_auth_key(); + /* XXXX make sure we're actually supposed to send this! */ + + if (!pk) { + log_warn(LD_BUG, "Can't compute authenticate cell: no client auth key"); + return -1; + } + if (! authchallenge_type_is_supported(authtype)) { + log_warn(LD_BUG, "Tried to send authenticate cell with unknown " + "authentication type %d", authtype); + return -1; + } + + cell = connection_or_compute_authenticate_cell_body(conn, + authtype, + pk, + get_current_auth_keypair(), + 0 /* not server */); + if (! cell) { + log_fn(LOG_PROTOCOL_WARN, LD_NET, "Unable to compute authenticate cell!"); + return -1; + } + connection_or_write_var_cell_to_buf(cell, conn); + var_cell_free(cell); + + return 0; +} |