diff options
Diffstat (limited to 'src/feature/hs/hs_cell.c')
| -rw-r--r-- | src/feature/hs/hs_cell.c | 138 |
1 files changed, 97 insertions, 41 deletions
diff --git a/src/feature/hs/hs_cell.c b/src/feature/hs/hs_cell.c index 52bd663200..fc9f4a2654 100644 --- a/src/feature/hs/hs_cell.c +++ b/src/feature/hs/hs_cell.c @@ -13,6 +13,7 @@ #include "feature/hs_common/replaycache.h" #include "feature/hs/hs_cell.h" +#include "feature/hs/hs_ob.h" #include "core/crypto/hs_ntor.h" #include "core/or/origin_circuit_st.h" @@ -67,14 +68,17 @@ compute_introduce_mac(const uint8_t *encoded_cell, size_t encoded_cell_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. */ +/** + * From a set of keys, a list of subcredentials, and the ENCRYPTED section of + * an INTRODUCE2 cell, return an array of newly allocated intro cell keys + * structures. 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, + size_t n_subcredentials, + const hs_subcredential_t *subcredentials, const uint8_t *encrypted_section, curve25519_public_key_t *client_pk) { @@ -82,17 +86,19 @@ get_introduce2_key_material(const ed25519_public_key_t *auth_key, tor_assert(auth_key); tor_assert(enc_key); - tor_assert(subcredential); + tor_assert(n_subcredentials > 0); + tor_assert(subcredentials); tor_assert(encrypted_section); tor_assert(client_pk); - keys = tor_malloc_zero(sizeof(*keys)); + keys = tor_calloc(n_subcredentials, sizeof(hs_ntor_intro_cell_keys_t)); /* 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) { + if (hs_ntor_service_get_introduce1_keys_multi(auth_key, enc_key, client_pk, + n_subcredentials, + subcredentials, 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); @@ -747,6 +753,74 @@ hs_cell_parse_intro_established(const uint8_t *payload, size_t payload_len) return ret; } +/** For the encrypted INTRO2 cell in <b>encrypted_section</b>, use the crypto + * material in <b>data</b> to compute the right ntor keys. Also validate the + * INTRO2 MAC to ensure that the keys are the right ones. + * + * Return NULL on failure to either produce the key material or on MAC + * validation. Else return a newly allocated intro keys object. */ +static hs_ntor_intro_cell_keys_t * +get_introduce2_keys_and_verify_mac(hs_cell_introduce2_data_t *data, + const uint8_t *encrypted_section, + size_t encrypted_section_len) +{ + hs_ntor_intro_cell_keys_t *intro_keys = NULL; + hs_ntor_intro_cell_keys_t *intro_keys_result = NULL; + + /* 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->n_subcredentials, + data->subcredentials, + encrypted_section, + &data->client_pk); + if (intro_keys == NULL) { + log_info(LD_REND, "Invalid INTRODUCE2 encrypted data. Unable to " + "compute key material"); + return NULL; + } + + /* Make sure we are not about to underflow. */ + if (BUG(encrypted_section_len < DIGEST256_LEN)) { + return NULL; + } + + /* Validate MAC from the cell and our computed key material. The MAC field + * in the cell is at the end of the encrypted section. */ + intro_keys_result = tor_malloc_zero(sizeof(*intro_keys_result)); + for (unsigned i = 0; i < data->n_subcredentials; ++i) { + 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[i].mac_key, + sizeof(intro_keys[i].mac_key), + mac, sizeof(mac)); + /* Time-invariant conditional copy: if the MAC is what we expected, then + * set intro_keys_result to intro_keys[i]. Otherwise, don't: but don't + * leak which one it was! */ + bool equal = tor_memeq(mac, encrypted_section + mac_offset, sizeof(mac)); + memcpy_if_true_timei(equal, intro_keys_result, &intro_keys[i], + sizeof(*intro_keys_result)); + } + + /* We no longer need intro_keys. */ + memwipe(intro_keys, 0, + sizeof(hs_ntor_intro_cell_keys_t) * data->n_subcredentials); + tor_free(intro_keys); + + if (safe_mem_is_zero(intro_keys_result, sizeof(*intro_keys_result))) { + log_info(LD_REND, "Invalid MAC validation for INTRODUCE2 cell"); + tor_free(intro_keys_result); /* sets intro_keys_result to NULL */ + } + + return intro_keys_result; +} + /** Parse 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 @@ -795,47 +869,29 @@ hs_cell_parse_introduce2(hs_cell_introduce2_data_t *data, /* Check our replay cache for this introduction point. */ if (replaycache_add_test_and_elapsed(data->replay_cache, encrypted_section, encrypted_section_len, &elapsed)) { - log_warn(LD_REND, "Possible replay detected! An INTRODUCE2 cell with the" + log_warn(LD_REND, "Possible replay detected! An INTRODUCE2 cell with the " "same ENCRYPTED section was seen %ld seconds ago. " "Dropping cell.", (long int) elapsed); 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, - &data->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, + /* First bytes of the ENCRYPTED section are the client public key (they are + * guaranteed to exist because of the length check above). We are gonna use + * the client public key to compute the ntor keys and decrypt the payload: + */ + memcpy(&data->client_pk.public_key, encrypted_section, + CURVE25519_PUBKEY_LEN); + + /* Get the right INTRODUCE2 ntor keys and verify the cell MAC */ + intro_keys = get_introduce2_keys_and_verify_mac(data, encrypted_section, + encrypted_section_len); + if (!intro_keys) { + log_warn(LD_REND, "Could not get valid INTRO2 keys 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 = |