diff options
Diffstat (limited to 'src/feature/hs/hs_cell.c')
| -rw-r--r-- | src/feature/hs/hs_cell.c | 329 |
1 files changed, 258 insertions, 71 deletions
diff --git a/src/feature/hs/hs_cell.c b/src/feature/hs/hs_cell.c index 613ffe7260..8bdaa4922a 100644 --- a/src/feature/hs/hs_cell.c +++ b/src/feature/hs/hs_cell.c @@ -1,4 +1,4 @@ -/* Copyright (c) 2017-2019, The Tor Project, Inc. */ +/* Copyright (c) 2017-2020, The Tor Project, Inc. */ /* See LICENSE for licensing information */ /** @@ -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" @@ -24,7 +25,7 @@ #include "trunnel/hs/cell_introduce1.h" #include "trunnel/hs/cell_rendezvous.h" -/* Compute the MAC of an INTRODUCE cell in mac_out. The encoded_cell param is +/** 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 @@ -55,7 +56,7 @@ compute_introduce_mac(const uint8_t *encoded_cell, size_t encoded_cell_len, /* 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 + /* Second, put the CLIENT_PK + ENCRYPTED_DATA but omit the MAC field (which * is junk at this point). */ memcpy(mac_msg + offset, encrypted, (encrypted_len - DIGEST256_LEN)); offset += (encrypted_len - DIGEST256_LEN); @@ -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); @@ -101,7 +107,7 @@ get_introduce2_key_material(const ed25519_public_key_t *auth_key, return keys; } -/* Using the given encryption key, decrypt the encrypted_section of length +/** 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. */ @@ -136,7 +142,7 @@ decrypt_introduce2(const uint8_t *enc_key, const uint8_t *encrypted_section, return decrypted; } -/* Given a pointer to the decrypted data of the ENCRYPTED section of an +/** 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. */ @@ -188,7 +194,7 @@ parse_introduce2_encrypted(const uint8_t *decrypted_data, return NULL; } -/* Build a legacy ESTABLISH_INTRO cell with the given circuit nonce and RSA +/** 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 * of the size of RELAY_PAYLOAD_SIZE. Return the encoded cell length on * success else a negative value and cell_out is untouched. */ @@ -210,7 +216,7 @@ build_legacy_establish_intro(const char *circ_nonce, crypto_pk_t *enc_key, return cell_len; } -/* Parse an INTRODUCE2 cell from payload of size payload_len for the given +/** Parse an INTRODUCE2 cell from payload of size payload_len for the given * service and circuit which are used only for logging purposes. The resulting * parsed cell is put in cell_ptr_out. * @@ -249,7 +255,7 @@ parse_introduce2_cell(const hs_service_t *service, return -1; } -/* Set the onion public key onion_pk in cell, the encrypted section of an +/** Set the onion public key onion_pk in cell, the encrypted section of an * INTRODUCE1 cell. */ static void introduce1_set_encrypted_onion_key(trn_cell_introduce_encrypted_t *cell, @@ -266,7 +272,7 @@ introduce1_set_encrypted_onion_key(trn_cell_introduce_encrypted_t *cell, trn_cell_introduce_encrypted_getlen_onion_key(cell)); } -/* Set the link specifiers in lspecs in cell, the encrypted section of an +/** Set the link specifiers in lspecs in cell, the encrypted section of an * INTRODUCE1 cell. */ static void introduce1_set_encrypted_link_spec(trn_cell_introduce_encrypted_t *cell, @@ -286,8 +292,8 @@ introduce1_set_encrypted_link_spec(trn_cell_introduce_encrypted_t *cell, trn_cell_introduce_encrypted_add_nspecs(cell, ls)); } -/* Set padding in the enc_cell only if needed that is the total length of both - * sections are below the mininum required for an INTRODUCE1 cell. */ +/** Set padding in the enc_cell only if needed that is the total length of both + * sections are below the minimum required for an INTRODUCE1 cell. */ static void introduce1_set_encrypted_padding(const trn_cell_introduce1_t *cell, trn_cell_introduce_encrypted_t *enc_cell) @@ -306,7 +312,7 @@ introduce1_set_encrypted_padding(const trn_cell_introduce1_t *cell, } } -/* Encrypt the ENCRYPTED payload and encode it in the cell using the enc_cell +/** Encrypt the ENCRYPTED payload and encode it in the cell using the enc_cell * and the INTRODUCE1 data. * * This can't fail but it is very important that the caller sets every field @@ -394,7 +400,7 @@ introduce1_encrypt_and_encode(trn_cell_introduce1_t *cell, tor_free(encrypted); } -/* Using the INTRODUCE1 data, setup the ENCRYPTED section in cell. This means +/** Using the INTRODUCE1 data, setup the ENCRYPTED section in cell. This means * set it, encrypt it and encode it. */ static void introduce1_set_encrypted(trn_cell_introduce1_t *cell, @@ -435,7 +441,7 @@ introduce1_set_encrypted(trn_cell_introduce1_t *cell, trn_cell_introduce_encrypted_free(enc_cell); } -/* Set the authentication key in the INTRODUCE1 cell from the given data. */ +/** Set the authentication key in the INTRODUCE1 cell from the given data. */ static void introduce1_set_auth_key(trn_cell_introduce1_t *cell, const hs_cell_introduce1_data_t *data) @@ -451,7 +457,7 @@ introduce1_set_auth_key(trn_cell_introduce1_t *cell, data->auth_pk->pubkey, trn_cell_introduce1_getlen_auth_key(cell)); } -/* Set the legacy ID field in the INTRODUCE1 cell from the given data. */ +/** Set the legacy ID field in the INTRODUCE1 cell from the given data. */ static void introduce1_set_legacy_id(trn_cell_introduce1_t *cell, const hs_cell_introduce1_data_t *data) @@ -473,26 +479,150 @@ introduce1_set_legacy_id(trn_cell_introduce1_t *cell, } } +/** Build and add to the given DoS cell extension the given parameter type and + * value. */ +static void +build_establish_intro_dos_param(trn_cell_extension_dos_t *dos_ext, + uint8_t param_type, uint64_t param_value) +{ + trn_cell_extension_dos_param_t *dos_param = + trn_cell_extension_dos_param_new(); + + /* Extra safety. We should never send an unknown parameter type. */ + tor_assert(param_type == TRUNNEL_DOS_PARAM_TYPE_INTRO2_RATE_PER_SEC || + param_type == TRUNNEL_DOS_PARAM_TYPE_INTRO2_BURST_PER_SEC); + + trn_cell_extension_dos_param_set_type(dos_param, param_type); + trn_cell_extension_dos_param_set_value(dos_param, param_value); + trn_cell_extension_dos_add_params(dos_ext, dos_param); + + /* Not freeing the trunnel object because it is now owned by dos_ext. */ +} + +/** Build the DoS defense cell extension and put it in the given extensions + * object. Return 0 on success, -1 on failure. (Right now, failure is only + * possible if there is a bug.) */ +static int +build_establish_intro_dos_extension(const hs_service_config_t *service_config, + trn_cell_extension_t *extensions) +{ + ssize_t ret; + size_t dos_ext_encoded_len; + uint8_t *field_array; + trn_cell_extension_field_t *field = NULL; + trn_cell_extension_dos_t *dos_ext = NULL; + + tor_assert(service_config); + tor_assert(extensions); + + /* We are creating a cell extension field of the type DoS. */ + field = trn_cell_extension_field_new(); + trn_cell_extension_field_set_field_type(field, + TRUNNEL_CELL_EXTENSION_TYPE_DOS); + + /* Build DoS extension field. We will put in two parameters. */ + dos_ext = trn_cell_extension_dos_new(); + trn_cell_extension_dos_set_n_params(dos_ext, 2); + + /* Build DoS parameter INTRO2 rate per second. */ + build_establish_intro_dos_param(dos_ext, + TRUNNEL_DOS_PARAM_TYPE_INTRO2_RATE_PER_SEC, + service_config->intro_dos_rate_per_sec); + /* Build DoS parameter INTRO2 burst per second. */ + build_establish_intro_dos_param(dos_ext, + TRUNNEL_DOS_PARAM_TYPE_INTRO2_BURST_PER_SEC, + service_config->intro_dos_burst_per_sec); + + /* Set the field with the encoded DoS extension. */ + ret = trn_cell_extension_dos_encoded_len(dos_ext); + if (BUG(ret <= 0)) { + goto err; + } + dos_ext_encoded_len = ret; + /* Set length field and the field array size length. */ + trn_cell_extension_field_set_field_len(field, dos_ext_encoded_len); + trn_cell_extension_field_setlen_field(field, dos_ext_encoded_len); + /* Encode the DoS extension into the cell extension field. */ + field_array = trn_cell_extension_field_getarray_field(field); + ret = trn_cell_extension_dos_encode(field_array, + trn_cell_extension_field_getlen_field(field), dos_ext); + if (BUG(ret <= 0)) { + goto err; + } + tor_assert(ret == (ssize_t) dos_ext_encoded_len); + + /* Finally, encode field into the cell extension. */ + trn_cell_extension_add_fields(extensions, field); + + /* We've just add an extension field to the cell extensions so increment the + * total number. */ + trn_cell_extension_set_num(extensions, + trn_cell_extension_get_num(extensions) + 1); + + /* Cleanup. DoS extension has been encoded at this point. */ + trn_cell_extension_dos_free(dos_ext); + + return 0; + + err: + trn_cell_extension_field_free(field); + trn_cell_extension_dos_free(dos_ext); + return -1; +} + /* ========== */ /* Public API */ /* ========== */ -/* Build an ESTABLISH_INTRO cell with the given circuit nonce and intro point +/** Allocate and build all the ESTABLISH_INTRO cell extension. The given + * extensions pointer is always set to a valid cell extension object. */ +STATIC trn_cell_extension_t * +build_establish_intro_extensions(const hs_service_config_t *service_config, + const hs_service_intro_point_t *ip) +{ + int ret; + trn_cell_extension_t *extensions; + + tor_assert(service_config); + tor_assert(ip); + + extensions = trn_cell_extension_new(); + trn_cell_extension_set_num(extensions, 0); + + /* If the defense has been enabled service side (by the operator with a + * torrc option) and the intro point does support it. */ + if (service_config->has_dos_defense_enabled && + ip->support_intro2_dos_defense) { + /* This function takes care to increment the number of extensions. */ + ret = build_establish_intro_dos_extension(service_config, extensions); + if (ret < 0) { + /* Return no extensions on error. */ + goto end; + } + } + + end: + return extensions; +} + +/** Build an ESTABLISH_INTRO cell with the given circuit nonce and intro point * object. The encoded cell is put in cell_out that MUST at least be of the * size of RELAY_PAYLOAD_SIZE. Return the encoded cell length on success else * a negative value and cell_out is untouched. This function also supports * legacy cell creation. */ ssize_t hs_cell_build_establish_intro(const char *circ_nonce, + const hs_service_config_t *service_config, const hs_service_intro_point_t *ip, uint8_t *cell_out) { ssize_t cell_len = -1; uint16_t sig_len = ED25519_SIG_LEN; - trn_cell_extension_t *ext; trn_cell_establish_intro_t *cell = NULL; + trn_cell_extension_t *extensions; tor_assert(circ_nonce); + tor_assert(service_config); tor_assert(ip); /* Quickly handle the legacy IP. */ @@ -505,11 +635,12 @@ hs_cell_build_establish_intro(const char *circ_nonce, goto done; } + /* Build the extensions, if any. */ + extensions = build_establish_intro_extensions(service_config, ip); + /* Set extension data. None used here. */ - ext = trn_cell_extension_new(); - trn_cell_extension_set_num(ext, 0); cell = trn_cell_establish_intro_new(); - trn_cell_establish_intro_set_extensions(cell, ext); + trn_cell_establish_intro_set_extensions(cell, extensions); /* Set signature size. Array is then allocated in the cell. We need to do * this early so we can use trunnel API to get the signature length. */ trn_cell_establish_intro_set_sig_len(cell, sig_len); @@ -600,7 +731,7 @@ hs_cell_build_establish_intro(const char *circ_nonce, return cell_len; } -/* Parse the INTRO_ESTABLISHED cell in the payload of size payload_len. If we +/** Parse the INTRO_ESTABLISHED cell in the payload of size payload_len. If we * are successful at parsing it, return the length of the parsed cell else a * negative value on error. */ ssize_t @@ -622,7 +753,75 @@ hs_cell_parse_intro_established(const uint8_t *payload, size_t payload_len) return ret; } -/* Parse the INTRODUCE2 cell using data which contains everything we need to +/** 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 * service and circ are only used for logging purposes. */ @@ -670,47 +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 = @@ -758,7 +939,14 @@ hs_cell_parse_introduce2(hs_cell_introduce2_data_t *data, 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)); + if (BUG(!lspec)) { + goto done; + } + link_specifier_t *lspec_dup = link_specifier_dup(lspec); + if (BUG(!lspec_dup)) { + goto done; + } + smartlist_add(data->link_specifiers, lspec_dup); } /* Success. */ @@ -776,7 +964,7 @@ hs_cell_parse_introduce2(hs_cell_introduce2_data_t *data, return ret; } -/* Build a RENDEZVOUS1 cell with the given rendezvous cookie and handshake +/** Build a RENDEZVOUS1 cell with the given rendezvous cookie and handshake * info. The encoded cell is put in cell_out and the length of the data is * returned. This can't fail. */ ssize_t @@ -810,7 +998,7 @@ hs_cell_build_rendezvous1(const uint8_t *rendezvous_cookie, return cell_len; } -/* Build an INTRODUCE1 cell from the given data. The encoded cell is put in +/** Build an INTRODUCE1 cell from the given data. The encoded cell is put in * cell_out which must be of at least size RELAY_PAYLOAD_SIZE. On success, the * encoded length is returned else a negative value and the content of * cell_out should be ignored. */ @@ -851,7 +1039,7 @@ hs_cell_build_introduce1(const hs_cell_introduce1_data_t *data, return cell_len; } -/* Build an ESTABLISH_RENDEZVOUS cell from the given rendezvous_cookie. The +/** Build an ESTABLISH_RENDEZVOUS cell from the given rendezvous_cookie. The * encoded cell is put in cell_out which must be of at least * RELAY_PAYLOAD_SIZE. On success, the encoded length is returned and the * caller should clear up the content of the cell. @@ -868,7 +1056,7 @@ hs_cell_build_establish_rendezvous(const uint8_t *rendezvous_cookie, return HS_REND_COOKIE_LEN; } -/* Handle an INTRODUCE_ACK cell encoded in payload of length payload_len. +/** Handle an INTRODUCE_ACK cell encoded in payload of length payload_len. * Return the status code on success else a negative value if the cell as not * decodable. */ int @@ -903,7 +1091,7 @@ hs_cell_parse_introduce_ack(const uint8_t *payload, size_t payload_len) return ret; } -/* Handle a RENDEZVOUS2 cell encoded in payload of length payload_len. On +/** Handle a RENDEZVOUS2 cell encoded in payload of length payload_len. On * success, handshake_info contains the data in the HANDSHAKE_INFO field, and * 0 is returned. On error, a negative value is returned. */ int @@ -935,7 +1123,7 @@ hs_cell_parse_rendezvous2(const uint8_t *payload, size_t payload_len, return ret; } -/* Clear the given INTRODUCE1 data structure data. */ +/** Clear the given INTRODUCE1 data structure data. */ void hs_cell_introduce1_data_clear(hs_cell_introduce1_data_t *data) { @@ -949,4 +1137,3 @@ hs_cell_introduce1_data_clear(hs_cell_introduce1_data_t *data) /* The data object has no ownership of any members. */ memwipe(data, 0, sizeof(hs_cell_introduce1_data_t)); } - |