commit f1498e75ddf8e493edecf940616703c36fa17de8 Author: George Kadianakis <desnacked@riseup.net> Date: Tue Dec 10 13:54:47 2019 +0200 hs-v3: Extract INTRO2 key computation to its own function. Part of #32709 Signed-off-by: David Goulet <dgoulet@torproject.org> --- src/feature/hs/hs_cell.c | 92 ++++++++++++++++++++++++++++++++---------------- 1 file changed, 61 insertions(+), 31 deletions(-) diff --git a/src/feature/hs/hs_cell.c b/src/feature/hs/hs_cell.c index 52bd66320..d59ea9edb 100644 --- a/src/feature/hs/hs_cell.c +++ b/src/feature/hs/hs_cell.c @@ -747,6 +747,61 @@ 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 + * valication. Else 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; + + /* 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"); + goto err; + } + + /* 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"); + goto err; + } + } + + goto done; + + err: + if (intro_keys) { + memwipe(intro_keys, 0, sizeof(hs_ntor_intro_cell_keys_t)); + tor_free(intro_keys); + } + + done: + return intro_keys; +} + /** 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 @@ -801,41 +856,16 @@ hs_cell_parse_introduce2(hs_cell_introduce2_data_t *data, 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, + /* 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_info(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 =