commit 5e710368b3e9a19862422d4bd43f2c1d8d0ceba8 Author: David Goulet dgoulet@torproject.org Date: Tue Mar 7 14:57:14 2017 -0500
prop224: Handle service INTRODUCE2 cell
At this commit, launching rendezvous circuit is not implemented, only a placeholder.
Signed-off-by: David Goulet dgoulet@torproject.org --- src/or/hs_cell.c | 318 ++++++++++++++++++++++++++++++++++++++++++++++++++++ src/or/hs_cell.h | 39 +++++++ src/or/hs_circuit.c | 66 +++++++++++ src/or/hs_circuit.h | 8 ++ src/or/hs_service.c | 77 ++++++++++++- src/or/hs_service.h | 3 + src/or/rendcommon.c | 2 +- 7 files changed, 511 insertions(+), 2 deletions(-)
diff --git a/src/or/hs_cell.c b/src/or/hs_cell.c index 0d34ef596..aff6ee04e 100644 --- a/src/or/hs_cell.c +++ b/src/or/hs_cell.c @@ -7,13 +7,180 @@ **/
#include "or.h" +#include "config.h" #include "rendservice.h"
#include "hs_cell.h" +#include "hs_ntor.h"
/* Trunnel. */ +#include "ed25519_cert.h" #include "hs/cell_common.h" #include "hs/cell_establish_intro.h" +#include "hs/cell_introduce1.h" + +/* Compute the MAC of an INTRODUCE cell in mac_out. The encoded_cell param is + * the cell content up to the ENCRYPTED section of length encoded_cell_len. + * The encrypted param is the start of the ENCRYPTED section of length + * encrypted_len. The mac_key is the key needed for the computation of the MAC + * derived from the ntor handshake of length mac_key_len. + * + * The length mac_out_len must be at least DIGEST256_LEN. */ +static void +compute_introduce_mac(const uint8_t *encoded_cell, size_t encoded_cell_len, + const uint8_t *encrypted, size_t encrypted_len, + const uint8_t *mac_key, size_t mac_key_len, + uint8_t *mac_out, size_t mac_out_len) +{ + size_t offset = 0; + size_t mac_msg_len; + uint8_t mac_msg[RELAY_PAYLOAD_SIZE] = {0}; + + tor_assert(encoded_cell); + tor_assert(encrypted); + tor_assert(mac_key); + tor_assert(mac_out); + tor_assert(mac_out_len >= DIGEST256_LEN); + + /* Compute the size of the message which is basically the entire cell until + * the MAC field of course. */ + mac_msg_len = encoded_cell_len + (encrypted_len - DIGEST256_LEN); + tor_assert(mac_msg_len <= sizeof(mac_msg)); + + /* First, put the encoded cell in the msg. */ + memcpy(mac_msg, encoded_cell, encoded_cell_len); + offset += encoded_cell_len; + /* Second, put the CLIENT_PK + ENCRYPTED_DATA but ommit the MAC field (which + * is junk at this point). */ + memcpy(mac_msg + offset, encrypted, (encrypted_len - DIGEST256_LEN)); + offset += (encrypted_len - DIGEST256_LEN); + tor_assert(offset == mac_msg_len); + + crypto_mac_sha3_256(mac_out, mac_out_len, + mac_key, mac_key_len, + mac_msg, mac_msg_len); + memwipe(mac_msg, 0, sizeof(mac_msg)); +} + +/* From a set of keys, subcredential and the ENCRYPTED section of an + * INTRODUCE2 cell, return a newly allocated intro cell keys structure. + * Finally, the client public key is copied in client_pk. On error, return + * NULL. */ +static hs_ntor_intro_cell_keys_t * +get_introduce2_key_material(const ed25519_public_key_t *auth_key, + const curve25519_keypair_t *enc_key, + const uint8_t *subcredential, + const uint8_t *encrypted_section, + curve25519_public_key_t *client_pk) +{ + hs_ntor_intro_cell_keys_t *keys; + + tor_assert(auth_key); + tor_assert(enc_key); + tor_assert(subcredential); + tor_assert(encrypted_section); + tor_assert(client_pk); + + keys = tor_malloc_zero(sizeof(*keys)); + + /* First bytes of the ENCRYPTED section are the client public key. */ + memcpy(client_pk->public_key, encrypted_section, CURVE25519_PUBKEY_LEN); + + if (hs_ntor_service_get_introduce1_keys(auth_key, enc_key, client_pk, + subcredential, keys) < 0) { + /* Don't rely on the caller to wipe this on error. */ + memwipe(client_pk, 0, sizeof(curve25519_public_key_t)); + tor_free(keys); + keys = NULL; + } + return keys; +} + +/* Using the given encryption key, decrypt the encrypted_section of length + * encrypted_section_len of an INTRODUCE2 cell and return a newly allocated + * buffer containing the decrypted data. On decryption failure, NULL is + * returned. */ +static uint8_t * +decrypt_introduce2(const uint8_t *enc_key, const uint8_t *encrypted_section, + size_t encrypted_section_len) +{ + uint8_t *decrypted = NULL; + crypto_cipher_t *cipher = NULL; + + tor_assert(enc_key); + tor_assert(encrypted_section); + + /* Decrypt ENCRYPTED section. */ + cipher = crypto_cipher_new_with_bits((char *) enc_key, + CURVE25519_PUBKEY_LEN * 8); + tor_assert(cipher); + + /* This is symmetric encryption so can't be bigger than the encrypted + * section length. */ + decrypted = tor_malloc_zero(encrypted_section_len); + if (crypto_cipher_decrypt(cipher, (char *) decrypted, + (const char *) encrypted_section, + encrypted_section_len) < 0) { + tor_free(decrypted); + decrypted = NULL; + goto done; + } + + done: + crypto_cipher_free(cipher); + return decrypted; +} + +/* Given a pointer to the decrypted data of the ENCRYPTED section of an + * INTRODUCE2 cell of length decrypted_len, parse and validate the cell + * content. Return a newly allocated cell structure or NULL on error. The + * circuit and service object are only used for logging purposes. */ +static trn_cell_introduce_encrypted_t * +parse_introduce2_encrypted(const uint8_t *decrypted_data, + size_t decrypted_len, const origin_circuit_t *circ, + const hs_service_t *service) +{ + trn_cell_introduce_encrypted_t *enc_cell = NULL; + + tor_assert(decrypted_data); + tor_assert(circ); + tor_assert(service); + + if (trn_cell_introduce_encrypted_parse(&enc_cell, decrypted_data, + decrypted_len) < 0) { + log_info(LD_REND, "Unable to parse the decrypted ENCRYPTED section of " + "the INTRODUCE2 cell on circuit %u for service %s", + TO_CIRCUIT(circ)->n_circ_id, + safe_str_client(service->onion_address)); + goto err; + } + + if (trn_cell_introduce_encrypted_get_onion_key_type(enc_cell) != + HS_CELL_ONION_KEY_TYPE_NTOR) { + log_info(LD_REND, "INTRODUCE2 onion key type is invalid. Got %u but " + "expected %u on circuit %u for service %s", + trn_cell_introduce_encrypted_get_onion_key_type(enc_cell), + HS_CELL_ONION_KEY_TYPE_NTOR, TO_CIRCUIT(circ)->n_circ_id, + safe_str_client(service->onion_address)); + goto err; + } + + if (trn_cell_introduce_encrypted_getlen_onion_key(enc_cell) != + CURVE25519_PUBKEY_LEN) { + log_info(LD_REND, "INTRODUCE2 onion key length is invalid. Got %ld but " + "expected %d on circuit %u for service %s", + trn_cell_introduce_encrypted_getlen_onion_key(enc_cell), + CURVE25519_PUBKEY_LEN, TO_CIRCUIT(circ)->n_circ_id, + safe_str_client(service->onion_address)); + goto err; + } + /* XXX: Validate NSPEC field as well. */ + + return enc_cell; + err: + trn_cell_introduce_encrypted_free(enc_cell); + return NULL; +}
/* Build a legacy ESTABLISH_INTRO cell with the given circuit nonce and RSA * encryption key. The encoded cell is put in cell_out that MUST at least be @@ -183,3 +350,154 @@ hs_cell_parse_intro_established(const uint8_t *payload, size_t payload_len) return ret; }
+/* Parsse the INTRODUCE2 cell using data which contains everything we need to + * do so and contains the destination buffers of information we extract and + * compute from the cell. Return 0 on success else a negative value. The + * service and circ are only used for logging purposes. */ +ssize_t +hs_cell_parse_introduce2(hs_cell_introduce2_data_t *data, + const origin_circuit_t *circ, + const hs_service_t *service) +{ + int ret = -1; + uint8_t *decrypted = NULL; + size_t encrypted_section_len; + const uint8_t *encrypted_section; + curve25519_public_key_t client_pk; + trn_cell_introduce1_t *cell = NULL; + trn_cell_introduce_encrypted_t *enc_cell = NULL; + hs_ntor_intro_cell_keys_t *intro_keys = NULL; + + tor_assert(data); + tor_assert(circ); + tor_assert(service); + + /* Parse the cell so we can start cell validation. */ + if (trn_cell_introduce1_parse(&cell, data->payload, + data->payload_len) < 0) { + log_info(LD_PROTOCOL, "Unable to parse INTRODUCE2 cell on circuit %u " + "for service %s", + TO_CIRCUIT(circ)->n_circ_id, + safe_str_client(service->onion_address)); + goto done; + } + + /* XXX: Add/Test replaycache. */ + + log_info(LD_REND, "Received a decodable INTRODUCE2 cell on circuit %u " + "for service %s. Decoding encrypted section...", + TO_CIRCUIT(circ)->n_circ_id, + safe_str_client(service->onion_address)); + + encrypted_section = trn_cell_introduce1_getconstarray_encrypted(cell); + encrypted_section_len = trn_cell_introduce1_getlen_encrypted(cell); + + /* Encrypted section must at least contain the CLIENT_PK and MAC which is + * defined in section 3.3.2 of the specification. */ + if (encrypted_section_len < (CURVE25519_PUBKEY_LEN + DIGEST256_LEN)) { + log_info(LD_REND, "Invalid INTRODUCE2 encrypted section length " + "for service %s. Dropping cell.", + safe_str_client(service->onion_address)); + goto done; + } + + /* Build the key material out of the key material found in the cell. */ + intro_keys = get_introduce2_key_material(data->auth_pk, data->enc_kp, + data->subcredential, + encrypted_section, &client_pk); + if (intro_keys == NULL) { + log_info(LD_REND, "Invalid INTRODUCE2 encrypted data. Unable to " + "compute key material on circuit %u for service %s", + TO_CIRCUIT(circ)->n_circ_id, + safe_str_client(service->onion_address)); + goto done; + } + + /* Validate MAC from the cell and our computed key material. The MAC field + * in the cell is at the end of the encrypted section. */ + { + uint8_t mac[DIGEST256_LEN]; + /* The MAC field is at the very end of the ENCRYPTED section. */ + size_t mac_offset = encrypted_section_len - sizeof(mac); + /* Compute the MAC. Use the entire encoded payload with a length up to the + * ENCRYPTED section. */ + compute_introduce_mac(data->payload, + data->payload_len - encrypted_section_len, + encrypted_section, encrypted_section_len, + intro_keys->mac_key, sizeof(intro_keys->mac_key), + mac, sizeof(mac)); + if (tor_memcmp(mac, encrypted_section + mac_offset, sizeof(mac))) { + log_info(LD_REND, "Invalid MAC validation for INTRODUCE2 cell on " + "circuit %u for service %s", + TO_CIRCUIT(circ)->n_circ_id, + safe_str_client(service->onion_address)); + goto done; + } + } + + { + /* The ENCRYPTED_DATA section starts just after the CLIENT_PK. */ + const uint8_t *encrypted_data = + encrypted_section + sizeof(data->client_pk); + /* It's symmetric encryption so it's correct to use the ENCRYPTED length + * for decryption. Computes the length of ENCRYPTED_DATA meaning removing + * the CLIENT_PK and MAC length. */ + size_t encrypted_data_len = + encrypted_section_len - (sizeof(data->client_pk) + DIGEST256_LEN); + + /* This decrypts the ENCRYPTED_DATA section of the cell. */ + decrypted = decrypt_introduce2(intro_keys->enc_key, + encrypted_data, encrypted_data_len); + if (decrypted == NULL) { + log_info(LD_REND, "Unable to decrypt the ENCRYPTED section of an " + "INTRODUCE2 cell on circuit %u for service %s", + TO_CIRCUIT(circ)->n_circ_id, + safe_str_client(service->onion_address)); + goto done; + } + + /* Parse this blob into an encrypted cell structure so we can then extract + * the data we need out of it. */ + enc_cell = parse_introduce2_encrypted(decrypted, encrypted_data_len, + circ, service); + memwipe(decrypted, 0, encrypted_data_len); + if (enc_cell == NULL) { + goto done; + } + } + + /* XXX: Implement client authorization checks. */ + + /* Extract onion key and rendezvous cookie from the cell used for the + * rendezvous point circuit e2e encryption. */ + memcpy(data->onion_pk.public_key, + trn_cell_introduce_encrypted_getconstarray_onion_key(enc_cell), + CURVE25519_PUBKEY_LEN); + memcpy(data->rendezvous_cookie, + trn_cell_introduce_encrypted_getconstarray_rend_cookie(enc_cell), + sizeof(data->rendezvous_cookie)); + + /* Extract rendezvous link specifiers. */ + for (size_t idx = 0; + idx < trn_cell_introduce_encrypted_get_nspec(enc_cell); idx++) { + link_specifier_t *lspec = + trn_cell_introduce_encrypted_get_nspecs(enc_cell, idx); + smartlist_add(data->link_specifiers, hs_link_specifier_dup(lspec)); + } + + /* Success. */ + ret = 0; + log_info(LD_REND, "Valid INTRODUCE2 cell. Launching rendezvous circuit."); + + done: + memwipe(&client_pk, 0, sizeof(client_pk)); + if (intro_keys) { + memwipe(intro_keys, 0, sizeof(hs_ntor_intro_cell_keys_t)); + tor_free(intro_keys); + } + tor_free(decrypted); + trn_cell_introduce1_free(cell); + trn_cell_introduce_encrypted_free(enc_cell); + return ret; +} + diff --git a/src/or/hs_cell.h b/src/or/hs_cell.h index 8e3402889..901ff81aa 100644 --- a/src/or/hs_cell.h +++ b/src/or/hs_cell.h @@ -9,14 +9,53 @@ #ifndef TOR_HS_CELL_H #define TOR_HS_CELL_H
+#include "or.h" #include "hs_service.h"
+/* Onion key type found in the INTRODUCE1 cell. */ +typedef enum { + HS_CELL_ONION_KEY_TYPE_NTOR = 1, +} hs_cell_onion_key_type_t; + +/* This data structure contains data that we need to parse an INTRODUCE2 cell + * which is used by the INTRODUCE2 cell parsing function. On a successful + * parsing, the onion_pk and rendezvous_cookie will be populated with the + * computed key material from the cell data. */ +typedef struct hs_cell_introduce2_data_t { + /*** Immutable Section. ***/ + + /* Introduction point authentication public key. */ + const ed25519_public_key_t *auth_pk; + /* Introduction point encryption keypair for the ntor handshake. */ + const curve25519_keypair_t *enc_kp; + /* Subcredentials of the service. */ + const uint8_t *subcredential; + /* Payload of the received encoded cell. */ + const uint8_t *payload; + /* Size of the payload of the received encoded cell. */ + size_t payload_len; + + /*** Muttable Section. ***/ + + /* Onion public key computed using the INTRODUCE2 encrypted section. */ + curve25519_public_key_t onion_pk; + /* Rendezvous cookie taken from the INTRODUCE2 encrypted section. */ + uint8_t rendezvous_cookie[REND_COOKIE_LEN]; + /* Client public key from the INTRODUCE2 encrypted section. */ + curve25519_public_key_t client_pk; + /* Link specifiers of the rendezvous point. Contains link_specifier_t. */ + smartlist_t *link_specifiers; +} hs_cell_introduce2_data_t; + ssize_t hs_cell_build_establish_intro(const char *circ_nonce, const hs_service_intro_point_t *ip, uint8_t *cell_out);
ssize_t hs_cell_parse_intro_established(const uint8_t *payload, size_t payload_len); +ssize_t hs_cell_parse_introduce2(hs_cell_introduce2_data_t *data, + const origin_circuit_t *circ, + const hs_service_t *service);
#endif /* TOR_HS_CELL_H */
diff --git a/src/or/hs_circuit.c b/src/or/hs_circuit.c index 51c07c0ba..a11699227 100644 --- a/src/or/hs_circuit.c +++ b/src/or/hs_circuit.c @@ -312,6 +312,18 @@ send_establish_intro(const hs_service_t *service, /* Public API */ /* ========== */
+int +hs_circ_launch_rendezvous_point(const hs_service_t *service, + const curve25519_public_key_t *onion_key, + const uint8_t *rendezvous_cookie) +{ + tor_assert(service); + tor_assert(onion_key); + tor_assert(rendezvous_cookie); + /* XXX: Implement rendezvous launch support. */ + return 0; +} + /* For a given service and a service intro point, launch a circuit to the * extend info ei. If the service is a single onion, a one-hop circuit will be * requested. Return 0 if the circuit was successfully launched and tagged @@ -468,6 +480,60 @@ hs_circ_handle_intro_established(const hs_service_t *service, return ret; }
+/* Handle an INTRODUCE2 unparsed payload of payload_len for the given circuit + * and service. This cell is associated with the intro point object ip and the + * subcredential. Return 0 on success else a negative value. */ +int +hs_circ_handle_introduce2(const hs_service_t *service, + const origin_circuit_t *circ, + hs_service_intro_point_t *ip, + const uint8_t *subcredential, + const uint8_t *payload, size_t payload_len) +{ + int ret = -1; + hs_cell_introduce2_data_t data; + + tor_assert(service); + tor_assert(circ); + tor_assert(ip); + tor_assert(subcredential); + tor_assert(payload); + + /* Populate the data structure with everything we need for the cell to be + * parsed, decrypted and key material computed correctly. */ + data.auth_pk = &ip->auth_key_kp.pubkey; + data.enc_kp = &ip->enc_key_kp; + data.subcredential = subcredential; + data.payload = payload; + data.payload_len = payload_len; + data.link_specifiers = smartlist_new(); + + if (hs_cell_parse_introduce2(&data, circ, service) < 0) { + goto done; + } + + /* At this point, we just confirmed that the full INTRODUCE2 cell is valid + * so increment our counter that we've seen one on this intro point. */ + ip->introduce2_count++; + + /* Launch rendezvous circuit with the onion key and rend cookie. */ + ret = hs_circ_launch_rendezvous_point(service, &data.onion_pk, + data.rendezvous_cookie); + if (ret < 0) { + goto done; + } + + /* Success. */ + ret = 0; + + done: + SMARTLIST_FOREACH(data.link_specifiers, link_specifier_t *, lspec, + link_specifier_free(lspec)); + smartlist_free(data.link_specifiers); + memwipe(&data, 0, sizeof(data)); + return ret; +} + /* Circuit <b>circ</b> just finished the rend ntor key exchange. Use the key * exchange output material at <b>ntor_key_seed</b> and setup <b>circ</b> to * serve as a rendezvous end-to-end circuit between the client and the diff --git a/src/or/hs_circuit.h b/src/or/hs_circuit.h index bc29781d8..1cada0b8a 100644 --- a/src/or/hs_circuit.h +++ b/src/or/hs_circuit.h @@ -23,6 +23,9 @@ int hs_circ_service_intro_has_opened(hs_service_t *service, int hs_circ_launch_intro_point(hs_service_t *service, const hs_service_intro_point_t *ip, extend_info_t *ei, time_t now); +int hs_circ_launch_rendezvous_point(const hs_service_t *service, + const curve25519_public_key_t *onion_key, + const uint8_t *rendezvous_cookie);
/* Cell API. */ void hs_circ_send_establish_intro(const hs_service_t *service, @@ -33,6 +36,11 @@ int hs_circ_handle_intro_established(const hs_service_t *service, origin_circuit_t *circ, const uint8_t *payload, size_t payload_len); +int hs_circ_handle_introduce2(const hs_service_t *service, + const origin_circuit_t *circ, + hs_service_intro_point_t *ip, + const uint8_t *subcredential, + const uint8_t *payload, size_t payload_len);
/* e2e circuit API. */
diff --git a/src/or/hs_service.c b/src/or/hs_service.c index 0b60a33ed..83b8b507f 100644 --- a/src/or/hs_service.c +++ b/src/or/hs_service.c @@ -34,8 +34,8 @@
/* Trunnel */ #include "ed25519_cert.h" -#include "hs/cell_establish_intro.h" #include "hs/cell_common.h" +#include "hs/cell_establish_intro.h"
/* Helper macro. Iterate over every service in the global map. The var is the * name of the service pointer. */ @@ -1845,10 +1845,85 @@ service_handle_intro_established(origin_circuit_t *circ, return -1; }
+/* Handle an INTRODUCE2 cell arriving on the given introduction circuit. + * Return 0 on success else a negative value. */ +static int +service_handle_introduce2(origin_circuit_t *circ, const uint8_t *payload, + size_t payload_len) +{ + hs_service_t *service = NULL; + hs_service_intro_point_t *ip = NULL; + hs_service_descriptor_t *desc = NULL; + + tor_assert(circ); + tor_assert(payload); + tor_assert(TO_CIRCUIT(circ)->purpose == CIRCUIT_PURPOSE_S_INTRO); + + /* We'll need every object associated with this circuit. */ + get_objects_from_ident(circ->hs_ident, &service, &ip, &desc); + + /* Get service object from the circuit identifier. */ + if (service == NULL) { + log_warn(LD_BUG, "Unknown service identity key %s when handling " + "an INTRODUCE2 cell on circuit %u", + safe_str_client(ed25519_fmt(&circ->hs_ident->identity_pk)), + TO_CIRCUIT(circ)->n_circ_id); + goto err; + } + if (ip == NULL) { + /* We don't recognize the key. */ + log_warn(LD_BUG, "Unknown introduction auth key when handling " + "an INTRODUCE2 cell on circuit %u for service %s", + TO_CIRCUIT(circ)->n_circ_id, + safe_str_client(service->onion_address)); + goto err; + } + /* If we have an IP object, we MUST have a descriptor object. */ + tor_assert(desc); + + /* XXX: Handle legacy IP connection. */ + + if (hs_circ_handle_introduce2(service, circ, ip, desc->desc->subcredential, + payload, payload_len) < 0) { + goto err; + } + + return 0; + err: + return -1; +} + /* ========== */ /* Public API */ /* ========== */
+/* Called when we get an INTRODUCE2 cell on the circ. Respond to the cell and + * launch a circuit to the rendezvous point. */ +int +hs_service_receive_introduce2(origin_circuit_t *circ, const uint8_t *payload, + size_t payload_len) +{ + int ret = -1; + + tor_assert(circ); + tor_assert(payload); + + /* Do some initial validation and logging before we parse the cell */ + if (TO_CIRCUIT(circ)->purpose != CIRCUIT_PURPOSE_S_INTRO) { + log_warn(LD_PROTOCOL, "Received an INTRODUCE2 cell on a " + "non introduction circuit of purpose %d", + TO_CIRCUIT(circ)->purpose); + goto done; + } + + ret = (circ->hs_ident) ? service_handle_introduce2(circ, payload, + payload_len) : + rend_service_receive_introduction(circ, payload, + payload_len); + done: + return ret; +} + /* Called when we get an INTRO_ESTABLISHED cell. Mark the circuit as an * established introduction point. Return 0 on success else a negative value * and the circuit is closed. */ diff --git a/src/or/hs_service.h b/src/or/hs_service.h index 3de96d64e..f12094a92 100644 --- a/src/or/hs_service.h +++ b/src/or/hs_service.h @@ -235,6 +235,9 @@ void hs_service_circuit_has_opened(origin_circuit_t *circ); int hs_service_receive_intro_established(origin_circuit_t *circ, const uint8_t *payload, size_t payload_len); +int hs_service_receive_introduce2(origin_circuit_t *circ, + const uint8_t *payload, + size_t payload_len);
/* These functions are only used by unit tests and we need to expose them else * hs_service.o ends up with no symbols in libor.a which makes clang throw a diff --git a/src/or/rendcommon.c b/src/or/rendcommon.c index 2cd66cb9c..8b555a316 100644 --- a/src/or/rendcommon.c +++ b/src/or/rendcommon.c @@ -777,7 +777,7 @@ rend_process_relay_cell(circuit_t *circ, const crypt_path_t *layer_hint, break; case RELAY_COMMAND_INTRODUCE2: if (origin_circ) - r = rend_service_receive_introduction(origin_circ,payload,length); + r = hs_service_receive_introduce2(origin_circ,payload,length); break; case RELAY_COMMAND_INTRODUCE_ACK: if (origin_circ)