diff options
Diffstat (limited to 'src/or/hs_descriptor.c')
| -rw-r--r-- | src/or/hs_descriptor.c | 2606 |
1 files changed, 2606 insertions, 0 deletions
diff --git a/src/or/hs_descriptor.c b/src/or/hs_descriptor.c new file mode 100644 index 0000000000..582ac9cb7c --- /dev/null +++ b/src/or/hs_descriptor.c @@ -0,0 +1,2606 @@ +/* Copyright (c) 2016-2017, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file hs_descriptor.c + * \brief Handle hidden service descriptor encoding/decoding. + * + * \details + * Here is a graphical depiction of an HS descriptor and its layers: + * + * +------------------------------------------------------+ + * |DESCRIPTOR HEADER: | + * | hs-descriptor 3 | + * | descriptor-lifetime 180 | + * | ... | + * | superencrypted | + * |+---------------------------------------------------+ | + * ||SUPERENCRYPTED LAYER (aka OUTER ENCRYPTED LAYER): | | + * || desc-auth-type x25519 | | + * || desc-auth-ephemeral-key | | + * || auth-client | | + * || auth-client | | + * || ... | | + * || encrypted | | + * ||+-------------------------------------------------+| | + * |||ENCRYPTED LAYER (aka INNER ENCRYPTED LAYER): || | + * ||| create2-formats || | + * ||| intro-auth-required || | + * ||| introduction-point || | + * ||| introduction-point || | + * ||| ... || | + * ||+-------------------------------------------------+| | + * |+---------------------------------------------------+ | + * +------------------------------------------------------+ + * + * The DESCRIPTOR HEADER section is completely unencrypted and contains generic + * descriptor metadata. + * + * The SUPERENCRYPTED LAYER section is the first layer of encryption, and it's + * encrypted using the blinded public key of the hidden service to protect + * against entities who don't know its onion address. The clients of the hidden + * service know its onion address and blinded public key, whereas third-parties + * (like HSDirs) don't know it (except if it's a public hidden service). + * + * The ENCRYPTED LAYER section is the second layer of encryption, and it's + * encrypted using the client authorization key material (if those exist). When + * client authorization is enabled, this second layer of encryption protects + * the descriptor content from unauthorized entities. If client authorization + * is disabled, this second layer of encryption does not provide any extra + * security but is still present. The plaintext of this layer contains all the + * information required to connect to the hidden service like its list of + * introduction points. + **/ + +/* For unit tests.*/ +#define HS_DESCRIPTOR_PRIVATE + +#include "or.h" +#include "ed25519_cert.h" /* Trunnel interface. */ +#include "hs_descriptor.h" +#include "circuitbuild.h" +#include "parsecommon.h" +#include "rendcache.h" +#include "hs_cache.h" +#include "hs_config.h" +#include "torcert.h" /* tor_cert_encode_ed22519() */ + +/* Constant string value used for the descriptor format. */ +#define str_hs_desc "hs-descriptor" +#define str_desc_cert "descriptor-signing-key-cert" +#define str_rev_counter "revision-counter" +#define str_superencrypted "superencrypted" +#define str_encrypted "encrypted" +#define str_signature "signature" +#define str_lifetime "descriptor-lifetime" +/* Constant string value for the encrypted part of the descriptor. */ +#define str_create2_formats "create2-formats" +#define str_intro_auth_required "intro-auth-required" +#define str_single_onion "single-onion-service" +#define str_intro_point "introduction-point" +#define str_ip_onion_key "onion-key" +#define str_ip_auth_key "auth-key" +#define str_ip_enc_key "enc-key" +#define str_ip_enc_key_cert "enc-key-cert" +#define str_ip_legacy_key "legacy-key" +#define str_ip_legacy_key_cert "legacy-key-cert" +#define str_intro_point_start "\n" str_intro_point " " +/* Constant string value for the construction to encrypt the encrypted data + * section. */ +#define str_enc_const_superencryption "hsdir-superencrypted-data" +#define str_enc_const_encryption "hsdir-encrypted-data" +/* Prefix required to compute/verify HS desc signatures */ +#define str_desc_sig_prefix "Tor onion service descriptor sig v3" +#define str_desc_auth_type "desc-auth-type" +#define str_desc_auth_key "desc-auth-ephemeral-key" +#define str_desc_auth_client "auth-client" +#define str_encrypted "encrypted" + +/* Authentication supported types. */ +static const struct { + hs_desc_auth_type_t type; + const char *identifier; +} intro_auth_types[] = { + { HS_DESC_AUTH_ED25519, "ed25519" }, + /* Indicate end of array. */ + { 0, NULL } +}; + +/* Descriptor ruleset. */ +static token_rule_t hs_desc_v3_token_table[] = { + T1_START(str_hs_desc, R_HS_DESCRIPTOR, EQ(1), NO_OBJ), + T1(str_lifetime, R3_DESC_LIFETIME, EQ(1), NO_OBJ), + T1(str_desc_cert, R3_DESC_SIGNING_CERT, NO_ARGS, NEED_OBJ), + T1(str_rev_counter, R3_REVISION_COUNTER, EQ(1), NO_OBJ), + T1(str_superencrypted, R3_SUPERENCRYPTED, NO_ARGS, NEED_OBJ), + T1_END(str_signature, R3_SIGNATURE, EQ(1), NO_OBJ), + END_OF_TABLE +}; + +/* Descriptor ruleset for the superencrypted section. */ +static token_rule_t hs_desc_superencrypted_v3_token_table[] = { + T1_START(str_desc_auth_type, R3_DESC_AUTH_TYPE, GE(1), NO_OBJ), + T1(str_desc_auth_key, R3_DESC_AUTH_KEY, GE(1), NO_OBJ), + T1N(str_desc_auth_client, R3_DESC_AUTH_CLIENT, GE(3), NO_OBJ), + T1(str_encrypted, R3_ENCRYPTED, NO_ARGS, NEED_OBJ), + END_OF_TABLE +}; + +/* Descriptor ruleset for the encrypted section. */ +static token_rule_t hs_desc_encrypted_v3_token_table[] = { + T1_START(str_create2_formats, R3_CREATE2_FORMATS, CONCAT_ARGS, NO_OBJ), + T01(str_intro_auth_required, R3_INTRO_AUTH_REQUIRED, ARGS, NO_OBJ), + T01(str_single_onion, R3_SINGLE_ONION_SERVICE, ARGS, NO_OBJ), + END_OF_TABLE +}; + +/* Descriptor ruleset for the introduction points section. */ +static token_rule_t hs_desc_intro_point_v3_token_table[] = { + T1_START(str_intro_point, R3_INTRODUCTION_POINT, EQ(1), NO_OBJ), + T1N(str_ip_onion_key, R3_INTRO_ONION_KEY, GE(2), OBJ_OK), + T1(str_ip_auth_key, R3_INTRO_AUTH_KEY, NO_ARGS, NEED_OBJ), + T1(str_ip_enc_key, R3_INTRO_ENC_KEY, GE(2), OBJ_OK), + T1(str_ip_enc_key_cert, R3_INTRO_ENC_KEY_CERT, ARGS, OBJ_OK), + T01(str_ip_legacy_key, R3_INTRO_LEGACY_KEY, ARGS, NEED_KEY_1024), + T01(str_ip_legacy_key_cert, R3_INTRO_LEGACY_KEY_CERT, ARGS, OBJ_OK), + END_OF_TABLE +}; + +/* Free the content of the plaintext section of a descriptor. */ +STATIC void +desc_plaintext_data_free_contents(hs_desc_plaintext_data_t *desc) +{ + if (!desc) { + return; + } + + if (desc->superencrypted_blob) { + tor_free(desc->superencrypted_blob); + } + tor_cert_free(desc->signing_key_cert); + + memwipe(desc, 0, sizeof(*desc)); +} + +/* Free the content of the encrypted section of a descriptor. */ +static void +desc_encrypted_data_free_contents(hs_desc_encrypted_data_t *desc) +{ + if (!desc) { + return; + } + + if (desc->intro_auth_types) { + SMARTLIST_FOREACH(desc->intro_auth_types, char *, a, tor_free(a)); + smartlist_free(desc->intro_auth_types); + } + if (desc->intro_points) { + SMARTLIST_FOREACH(desc->intro_points, hs_desc_intro_point_t *, ip, + hs_desc_intro_point_free(ip)); + smartlist_free(desc->intro_points); + } + memwipe(desc, 0, sizeof(*desc)); +} + +/* Using a key, salt and encrypted payload, build a MAC and put it in mac_out. + * We use SHA3-256 for the MAC computation. + * This function can't fail. */ +static void +build_mac(const uint8_t *mac_key, size_t mac_key_len, + const uint8_t *salt, size_t salt_len, + const uint8_t *encrypted, size_t encrypted_len, + uint8_t *mac_out, size_t mac_len) +{ + crypto_digest_t *digest; + + const uint64_t mac_len_netorder = tor_htonll(mac_key_len); + const uint64_t salt_len_netorder = tor_htonll(salt_len); + + tor_assert(mac_key); + tor_assert(salt); + tor_assert(encrypted); + tor_assert(mac_out); + + digest = crypto_digest256_new(DIGEST_SHA3_256); + /* As specified in section 2.5 of proposal 224, first add the mac key + * then add the salt first and then the encrypted section. */ + + crypto_digest_add_bytes(digest, (const char *) &mac_len_netorder, 8); + crypto_digest_add_bytes(digest, (const char *) mac_key, mac_key_len); + crypto_digest_add_bytes(digest, (const char *) &salt_len_netorder, 8); + crypto_digest_add_bytes(digest, (const char *) salt, salt_len); + crypto_digest_add_bytes(digest, (const char *) encrypted, encrypted_len); + crypto_digest_get_digest(digest, (char *) mac_out, mac_len); + crypto_digest_free(digest); +} + +/* Using a given decriptor object, build the secret input needed for the + * KDF and put it in the dst pointer which is an already allocated buffer + * of size dstlen. */ +static void +build_secret_input(const hs_descriptor_t *desc, uint8_t *dst, size_t dstlen) +{ + size_t offset = 0; + + tor_assert(desc); + tor_assert(dst); + tor_assert(HS_DESC_ENCRYPTED_SECRET_INPUT_LEN <= dstlen); + + /* XXX use the destination length as the memcpy length */ + /* Copy blinded public key. */ + memcpy(dst, desc->plaintext_data.blinded_pubkey.pubkey, + sizeof(desc->plaintext_data.blinded_pubkey.pubkey)); + offset += sizeof(desc->plaintext_data.blinded_pubkey.pubkey); + /* Copy subcredential. */ + memcpy(dst + offset, desc->subcredential, sizeof(desc->subcredential)); + offset += sizeof(desc->subcredential); + /* Copy revision counter value. */ + set_uint64(dst + offset, tor_htonll(desc->plaintext_data.revision_counter)); + offset += sizeof(uint64_t); + tor_assert(HS_DESC_ENCRYPTED_SECRET_INPUT_LEN == offset); +} + +/* Do the KDF construction and put the resulting data in key_out which is of + * key_out_len length. It uses SHAKE-256 as specified in the spec. */ +static void +build_kdf_key(const hs_descriptor_t *desc, + const uint8_t *salt, size_t salt_len, + uint8_t *key_out, size_t key_out_len, + int is_superencrypted_layer) +{ + uint8_t secret_input[HS_DESC_ENCRYPTED_SECRET_INPUT_LEN]; + crypto_xof_t *xof; + + tor_assert(desc); + tor_assert(salt); + tor_assert(key_out); + + /* Build the secret input for the KDF computation. */ + build_secret_input(desc, secret_input, sizeof(secret_input)); + + xof = crypto_xof_new(); + /* Feed our KDF. [SHAKE it like a polaroid picture --Yawning]. */ + crypto_xof_add_bytes(xof, secret_input, sizeof(secret_input)); + crypto_xof_add_bytes(xof, salt, salt_len); + + /* Feed in the right string constant based on the desc layer */ + if (is_superencrypted_layer) { + crypto_xof_add_bytes(xof, (const uint8_t *) str_enc_const_superencryption, + strlen(str_enc_const_superencryption)); + } else { + crypto_xof_add_bytes(xof, (const uint8_t *) str_enc_const_encryption, + strlen(str_enc_const_encryption)); + } + + /* Eat from our KDF. */ + crypto_xof_squeeze_bytes(xof, key_out, key_out_len); + crypto_xof_free(xof); + memwipe(secret_input, 0, sizeof(secret_input)); +} + +/* Using the given descriptor and salt, run it through our KDF function and + * then extract a secret key in key_out, the IV in iv_out and MAC in mac_out. + * This function can't fail. */ +static void +build_secret_key_iv_mac(const hs_descriptor_t *desc, + const uint8_t *salt, size_t salt_len, + uint8_t *key_out, size_t key_len, + uint8_t *iv_out, size_t iv_len, + uint8_t *mac_out, size_t mac_len, + int is_superencrypted_layer) +{ + size_t offset = 0; + uint8_t kdf_key[HS_DESC_ENCRYPTED_KDF_OUTPUT_LEN]; + + tor_assert(desc); + tor_assert(salt); + tor_assert(key_out); + tor_assert(iv_out); + tor_assert(mac_out); + + build_kdf_key(desc, salt, salt_len, kdf_key, sizeof(kdf_key), + is_superencrypted_layer); + /* Copy the bytes we need for both the secret key and IV. */ + memcpy(key_out, kdf_key, key_len); + offset += key_len; + memcpy(iv_out, kdf_key + offset, iv_len); + offset += iv_len; + memcpy(mac_out, kdf_key + offset, mac_len); + /* Extra precaution to make sure we are not out of bound. */ + tor_assert((offset + mac_len) == sizeof(kdf_key)); + memwipe(kdf_key, 0, sizeof(kdf_key)); +} + +/* === ENCODING === */ + +/* Encode the given link specifier objects into a newly allocated string. + * This can't fail so caller can always assume a valid string being + * returned. */ +STATIC char * +encode_link_specifiers(const smartlist_t *specs) +{ + char *encoded_b64 = NULL; + link_specifier_list_t *lslist = link_specifier_list_new(); + + tor_assert(specs); + /* No link specifiers is a code flow error, can't happen. */ + tor_assert(smartlist_len(specs) > 0); + tor_assert(smartlist_len(specs) <= UINT8_MAX); + + link_specifier_list_set_n_spec(lslist, smartlist_len(specs)); + + SMARTLIST_FOREACH_BEGIN(specs, const hs_desc_link_specifier_t *, + spec) { + link_specifier_t *ls = hs_desc_lspec_to_trunnel(spec); + if (ls) { + link_specifier_list_add_spec(lslist, ls); + } + } SMARTLIST_FOREACH_END(spec); + + { + uint8_t *encoded; + ssize_t encoded_len, encoded_b64_len, ret; + + encoded_len = link_specifier_list_encoded_len(lslist); + tor_assert(encoded_len > 0); + encoded = tor_malloc_zero(encoded_len); + ret = link_specifier_list_encode(encoded, encoded_len, lslist); + tor_assert(ret == encoded_len); + + /* Base64 encode our binary format. Add extra NUL byte for the base64 + * encoded value. */ + encoded_b64_len = base64_encode_size(encoded_len, 0) + 1; + encoded_b64 = tor_malloc_zero(encoded_b64_len); + ret = base64_encode(encoded_b64, encoded_b64_len, (const char *) encoded, + encoded_len, 0); + tor_assert(ret == (encoded_b64_len - 1)); + tor_free(encoded); + } + + link_specifier_list_free(lslist); + return encoded_b64; +} + +/* Encode an introduction point legacy key and certificate. Return a newly + * allocated string with it. On failure, return NULL. */ +static char * +encode_legacy_key(const hs_desc_intro_point_t *ip) +{ + char *key_str, b64_cert[256], *encoded = NULL; + size_t key_str_len; + + tor_assert(ip); + + /* Encode cross cert. */ + if (base64_encode(b64_cert, sizeof(b64_cert), + (const char *) ip->legacy.cert.encoded, + ip->legacy.cert.len, BASE64_ENCODE_MULTILINE) < 0) { + log_warn(LD_REND, "Unable to encode legacy crosscert."); + goto done; + } + /* Convert the encryption key to PEM format NUL terminated. */ + if (crypto_pk_write_public_key_to_string(ip->legacy.key, &key_str, + &key_str_len) < 0) { + log_warn(LD_REND, "Unable to encode legacy encryption key."); + goto done; + } + tor_asprintf(&encoded, + "%s \n%s" /* Newline is added by the call above. */ + "%s\n" + "-----BEGIN CROSSCERT-----\n" + "%s" + "-----END CROSSCERT-----", + str_ip_legacy_key, key_str, + str_ip_legacy_key_cert, b64_cert); + tor_free(key_str); + + done: + return encoded; +} + +/* Encode an introduction point encryption key and certificate. Return a newly + * allocated string with it. On failure, return NULL. */ +static char * +encode_enc_key(const hs_desc_intro_point_t *ip) +{ + char *encoded = NULL, *encoded_cert; + char key_b64[CURVE25519_BASE64_PADDED_LEN + 1]; + + tor_assert(ip); + + /* Base64 encode the encryption key for the "enc-key" field. */ + if (curve25519_public_to_base64(key_b64, &ip->enc_key) < 0) { + goto done; + } + if (tor_cert_encode_ed22519(ip->enc_key_cert, &encoded_cert) < 0) { + goto done; + } + tor_asprintf(&encoded, + "%s ntor %s\n" + "%s\n%s", + str_ip_enc_key, key_b64, + str_ip_enc_key_cert, encoded_cert); + tor_free(encoded_cert); + + done: + return encoded; +} + +/* Encode an introduction point onion key. Return a newly allocated string + * with it. On failure, return NULL. */ +static char * +encode_onion_key(const hs_desc_intro_point_t *ip) +{ + char *encoded = NULL; + char key_b64[CURVE25519_BASE64_PADDED_LEN + 1]; + + tor_assert(ip); + + /* Base64 encode the encryption key for the "onion-key" field. */ + if (curve25519_public_to_base64(key_b64, &ip->onion_key) < 0) { + goto done; + } + tor_asprintf(&encoded, "%s ntor %s", str_ip_onion_key, key_b64); + + done: + return encoded; +} + +/* Encode an introduction point object and return a newly allocated string + * with it. On failure, return NULL. */ +static char * +encode_intro_point(const ed25519_public_key_t *sig_key, + const hs_desc_intro_point_t *ip) +{ + char *encoded_ip = NULL; + smartlist_t *lines = smartlist_new(); + + tor_assert(ip); + tor_assert(sig_key); + + /* Encode link specifier. */ + { + char *ls_str = encode_link_specifiers(ip->link_specifiers); + smartlist_add_asprintf(lines, "%s %s", str_intro_point, ls_str); + tor_free(ls_str); + } + + /* Onion key encoding. */ + { + char *encoded_onion_key = encode_onion_key(ip); + if (encoded_onion_key == NULL) { + goto err; + } + smartlist_add_asprintf(lines, "%s", encoded_onion_key); + tor_free(encoded_onion_key); + } + + /* Authentication key encoding. */ + { + char *encoded_cert; + if (tor_cert_encode_ed22519(ip->auth_key_cert, &encoded_cert) < 0) { + goto err; + } + smartlist_add_asprintf(lines, "%s\n%s", str_ip_auth_key, encoded_cert); + tor_free(encoded_cert); + } + + /* Encryption key encoding. */ + { + char *encoded_enc_key = encode_enc_key(ip); + if (encoded_enc_key == NULL) { + goto err; + } + smartlist_add_asprintf(lines, "%s", encoded_enc_key); + tor_free(encoded_enc_key); + } + + /* Legacy key if any. */ + if (ip->legacy.key != NULL) { + /* Strong requirement else the IP creation was badly done. */ + tor_assert(ip->legacy.cert.encoded); + char *encoded_legacy_key = encode_legacy_key(ip); + if (encoded_legacy_key == NULL) { + goto err; + } + smartlist_add_asprintf(lines, "%s", encoded_legacy_key); + tor_free(encoded_legacy_key); + } + + /* Join them all in one blob of text. */ + encoded_ip = smartlist_join_strings(lines, "\n", 1, NULL); + + err: + SMARTLIST_FOREACH(lines, char *, l, tor_free(l)); + smartlist_free(lines); + return encoded_ip; +} + +/* Given a source length, return the new size including padding for the + * plaintext encryption. */ +static size_t +compute_padded_plaintext_length(size_t plaintext_len) +{ + size_t plaintext_padded_len; + const int padding_block_length = HS_DESC_SUPERENC_PLAINTEXT_PAD_MULTIPLE; + + /* Make sure we won't overflow. */ + tor_assert(plaintext_len <= (SIZE_T_CEILING - padding_block_length)); + + /* Get the extra length we need to add. For example, if srclen is 10200 + * bytes, this will expand to (2 * 10k) == 20k thus an extra 9800 bytes. */ + plaintext_padded_len = CEIL_DIV(plaintext_len, padding_block_length) * + padding_block_length; + /* Can never be extra careful. Make sure we are _really_ padded. */ + tor_assert(!(plaintext_padded_len % padding_block_length)); + return plaintext_padded_len; +} + +/* Given a buffer, pad it up to the encrypted section padding requirement. Set + * the newly allocated string in padded_out and return the length of the + * padded buffer. */ +STATIC size_t +build_plaintext_padding(const char *plaintext, size_t plaintext_len, + uint8_t **padded_out) +{ + size_t padded_len; + uint8_t *padded; + + tor_assert(plaintext); + tor_assert(padded_out); + + /* Allocate the final length including padding. */ + padded_len = compute_padded_plaintext_length(plaintext_len); + tor_assert(padded_len >= plaintext_len); + padded = tor_malloc_zero(padded_len); + + memcpy(padded, plaintext, plaintext_len); + *padded_out = padded; + return padded_len; +} + +/* Using a key, IV and plaintext data of length plaintext_len, create the + * encrypted section by encrypting it and setting encrypted_out with the + * data. Return size of the encrypted data buffer. */ +static size_t +build_encrypted(const uint8_t *key, const uint8_t *iv, const char *plaintext, + size_t plaintext_len, uint8_t **encrypted_out, + int is_superencrypted_layer) +{ + size_t encrypted_len; + uint8_t *padded_plaintext, *encrypted; + crypto_cipher_t *cipher; + + tor_assert(key); + tor_assert(iv); + tor_assert(plaintext); + tor_assert(encrypted_out); + + /* If we are encrypting the middle layer of the descriptor, we need to first + pad the plaintext */ + if (is_superencrypted_layer) { + encrypted_len = build_plaintext_padding(plaintext, plaintext_len, + &padded_plaintext); + /* Extra precautions that we have a valid padding length. */ + tor_assert(!(encrypted_len % HS_DESC_SUPERENC_PLAINTEXT_PAD_MULTIPLE)); + } else { /* No padding required for inner layers */ + padded_plaintext = tor_memdup(plaintext, plaintext_len); + encrypted_len = plaintext_len; + } + + /* This creates a cipher for AES. It can't fail. */ + cipher = crypto_cipher_new_with_iv_and_bits(key, iv, + HS_DESC_ENCRYPTED_BIT_SIZE); + /* We use a stream cipher so the encrypted length will be the same as the + * plaintext padded length. */ + encrypted = tor_malloc_zero(encrypted_len); + /* This can't fail. */ + crypto_cipher_encrypt(cipher, (char *) encrypted, + (const char *) padded_plaintext, encrypted_len); + *encrypted_out = encrypted; + /* Cleanup. */ + crypto_cipher_free(cipher); + tor_free(padded_plaintext); + return encrypted_len; +} + +/* Encrypt the given <b>plaintext</b> buffer using <b>desc</b> to get the + * keys. Set encrypted_out with the encrypted data and return the length of + * it. <b>is_superencrypted_layer</b> is set if this is the outer encrypted + * layer of the descriptor. */ +static size_t +encrypt_descriptor_data(const hs_descriptor_t *desc, const char *plaintext, + char **encrypted_out, int is_superencrypted_layer) +{ + char *final_blob; + size_t encrypted_len, final_blob_len, offset = 0; + uint8_t *encrypted; + uint8_t salt[HS_DESC_ENCRYPTED_SALT_LEN]; + uint8_t secret_key[HS_DESC_ENCRYPTED_KEY_LEN], secret_iv[CIPHER_IV_LEN]; + uint8_t mac_key[DIGEST256_LEN], mac[DIGEST256_LEN]; + + tor_assert(desc); + tor_assert(plaintext); + tor_assert(encrypted_out); + + /* Get our salt. The returned bytes are already hashed. */ + crypto_strongest_rand(salt, sizeof(salt)); + + /* KDF construction resulting in a key from which the secret key, IV and MAC + * key are extracted which is what we need for the encryption. */ + build_secret_key_iv_mac(desc, salt, sizeof(salt), + secret_key, sizeof(secret_key), + secret_iv, sizeof(secret_iv), + mac_key, sizeof(mac_key), + is_superencrypted_layer); + + /* Build the encrypted part that is do the actual encryption. */ + encrypted_len = build_encrypted(secret_key, secret_iv, plaintext, + strlen(plaintext), &encrypted, + is_superencrypted_layer); + memwipe(secret_key, 0, sizeof(secret_key)); + memwipe(secret_iv, 0, sizeof(secret_iv)); + /* This construction is specified in section 2.5 of proposal 224. */ + final_blob_len = sizeof(salt) + encrypted_len + DIGEST256_LEN; + final_blob = tor_malloc_zero(final_blob_len); + + /* Build the MAC. */ + build_mac(mac_key, sizeof(mac_key), salt, sizeof(salt), + encrypted, encrypted_len, mac, sizeof(mac)); + memwipe(mac_key, 0, sizeof(mac_key)); + + /* The salt is the first value. */ + memcpy(final_blob, salt, sizeof(salt)); + offset = sizeof(salt); + /* Second value is the encrypted data. */ + memcpy(final_blob + offset, encrypted, encrypted_len); + offset += encrypted_len; + /* Third value is the MAC. */ + memcpy(final_blob + offset, mac, sizeof(mac)); + offset += sizeof(mac); + /* Cleanup the buffers. */ + memwipe(salt, 0, sizeof(salt)); + memwipe(encrypted, 0, encrypted_len); + tor_free(encrypted); + /* Extra precaution. */ + tor_assert(offset == final_blob_len); + + *encrypted_out = final_blob; + return final_blob_len; +} + +/* Create and return a string containing a fake client-auth entry. It's the + * responsibility of the caller to free the returned string. This function will + * never fail. */ +static char * +get_fake_auth_client_str(void) +{ + char *auth_client_str = NULL; + /* We are gonna fill these arrays with fake base64 data. They are all double + * the size of their binary representation to fit the base64 overhead. */ + char client_id_b64[8*2]; + char iv_b64[16*2]; + char encrypted_cookie_b64[16*2]; + int retval; + + /* This is a macro to fill a field with random data and then base64 it. */ +#define FILL_WITH_FAKE_DATA_AND_BASE64(field) STMT_BEGIN \ + crypto_rand((char *)field, sizeof(field)); \ + retval = base64_encode_nopad(field##_b64, sizeof(field##_b64), \ + field, sizeof(field)); \ + tor_assert(retval > 0); \ + STMT_END + + { /* Get those fakes! */ + uint8_t client_id[8]; /* fake client-id */ + uint8_t iv[16]; /* fake IV (initialization vector) */ + uint8_t encrypted_cookie[16]; /* fake encrypted cookie */ + + FILL_WITH_FAKE_DATA_AND_BASE64(client_id); + FILL_WITH_FAKE_DATA_AND_BASE64(iv); + FILL_WITH_FAKE_DATA_AND_BASE64(encrypted_cookie); + } + + /* Build the final string */ + tor_asprintf(&auth_client_str, "%s %s %s %s", str_desc_auth_client, + client_id_b64, iv_b64, encrypted_cookie_b64); + +#undef FILL_WITH_FAKE_DATA_AND_BASE64 + + return auth_client_str; +} + +/** How many lines of "client-auth" we want in our descriptors; fake or not. */ +#define CLIENT_AUTH_ENTRIES_BLOCK_SIZE 16 + +/** Create the "client-auth" part of the descriptor and return a + * newly-allocated string with it. It's the responsibility of the caller to + * free the returned string. */ +static char * +get_fake_auth_client_lines(void) +{ + /* XXX: Client authorization is still not implemented, so all this function + does is make fake clients */ + int i = 0; + smartlist_t *auth_client_lines = smartlist_new(); + char *auth_client_lines_str = NULL; + + /* Make a line for each fake client */ + const int num_fake_clients = CLIENT_AUTH_ENTRIES_BLOCK_SIZE; + for (i = 0; i < num_fake_clients; i++) { + char *auth_client_str = get_fake_auth_client_str(); + tor_assert(auth_client_str); + smartlist_add(auth_client_lines, auth_client_str); + } + + /* Join all lines together to form final string */ + auth_client_lines_str = smartlist_join_strings(auth_client_lines, + "\n", 1, NULL); + /* Cleanup the mess */ + SMARTLIST_FOREACH(auth_client_lines, char *, a, tor_free(a)); + smartlist_free(auth_client_lines); + + return auth_client_lines_str; +} + +/* Create the inner layer of the descriptor (which includes the intro points, + * etc.). Return a newly-allocated string with the layer plaintext, or NULL if + * an error occured. It's the responsibility of the caller to free the returned + * string. */ +static char * +get_inner_encrypted_layer_plaintext(const hs_descriptor_t *desc) +{ + char *encoded_str = NULL; + smartlist_t *lines = smartlist_new(); + + /* Build the start of the section prior to the introduction points. */ + { + if (!desc->encrypted_data.create2_ntor) { + log_err(LD_BUG, "HS desc doesn't have recognized handshake type."); + goto err; + } + smartlist_add_asprintf(lines, "%s %d\n", str_create2_formats, + ONION_HANDSHAKE_TYPE_NTOR); + + if (desc->encrypted_data.intro_auth_types && + smartlist_len(desc->encrypted_data.intro_auth_types)) { + /* Put the authentication-required line. */ + char *buf = smartlist_join_strings(desc->encrypted_data.intro_auth_types, + " ", 0, NULL); + smartlist_add_asprintf(lines, "%s %s\n", str_intro_auth_required, buf); + tor_free(buf); + } + + if (desc->encrypted_data.single_onion_service) { + smartlist_add_asprintf(lines, "%s\n", str_single_onion); + } + } + + /* Build the introduction point(s) section. */ + SMARTLIST_FOREACH_BEGIN(desc->encrypted_data.intro_points, + const hs_desc_intro_point_t *, ip) { + char *encoded_ip = encode_intro_point(&desc->plaintext_data.signing_pubkey, + ip); + if (encoded_ip == NULL) { + log_err(LD_BUG, "HS desc intro point is malformed."); + goto err; + } + smartlist_add(lines, encoded_ip); + } SMARTLIST_FOREACH_END(ip); + + /* Build the entire encrypted data section into one encoded plaintext and + * then encrypt it. */ + encoded_str = smartlist_join_strings(lines, "", 0, NULL); + + err: + SMARTLIST_FOREACH(lines, char *, l, tor_free(l)); + smartlist_free(lines); + + return encoded_str; +} + +/* Create the middle layer of the descriptor, which includes the client auth + * data and the encrypted inner layer (provided as a base64 string at + * <b>layer2_b64_ciphertext</b>). Return a newly-allocated string with the + * layer plaintext, or NULL if an error occured. It's the responsibility of the + * caller to free the returned string. */ +static char * +get_outer_encrypted_layer_plaintext(const hs_descriptor_t *desc, + const char *layer2_b64_ciphertext) +{ + char *layer1_str = NULL; + smartlist_t *lines = smartlist_new(); + + /* XXX: Disclaimer: This function generates only _fake_ client auth + * data. Real client auth is not yet implemented, but client auth data MUST + * always be present in descriptors. In the future this function will be + * refactored to use real client auth data if they exist (#20700). */ + (void) *desc; + + /* Specify auth type */ + smartlist_add_asprintf(lines, "%s %s\n", str_desc_auth_type, "x25519"); + + { /* Create fake ephemeral x25519 key */ + char fake_key_base64[CURVE25519_BASE64_PADDED_LEN + 1]; + curve25519_keypair_t fake_x25519_keypair; + if (curve25519_keypair_generate(&fake_x25519_keypair, 0) < 0) { + goto done; + } + if (curve25519_public_to_base64(fake_key_base64, + &fake_x25519_keypair.pubkey) < 0) { + goto done; + } + smartlist_add_asprintf(lines, "%s %s\n", + str_desc_auth_key, fake_key_base64); + /* No need to memwipe any of these fake keys. They will go unused. */ + } + + { /* Create fake auth-client lines. */ + char *auth_client_lines = get_fake_auth_client_lines(); + tor_assert(auth_client_lines); + smartlist_add(lines, auth_client_lines); + } + + /* create encrypted section */ + { + smartlist_add_asprintf(lines, + "%s\n" + "-----BEGIN MESSAGE-----\n" + "%s" + "-----END MESSAGE-----", + str_encrypted, layer2_b64_ciphertext); + } + + layer1_str = smartlist_join_strings(lines, "", 0, NULL); + + done: + SMARTLIST_FOREACH(lines, char *, a, tor_free(a)); + smartlist_free(lines); + + return layer1_str; +} + +/* Encrypt <b>encoded_str</b> into an encrypted blob and then base64 it before + * returning it. <b>desc</b> is provided to derive the encryption + * keys. <b>is_superencrypted_layer</b> is set if <b>encoded_str</b> is the + * middle (superencrypted) layer of the descriptor. It's the responsibility of + * the caller to free the returned string. */ +static char * +encrypt_desc_data_and_base64(const hs_descriptor_t *desc, + const char *encoded_str, + int is_superencrypted_layer) +{ + char *enc_b64; + ssize_t enc_b64_len, ret_len, enc_len; + char *encrypted_blob = NULL; + + enc_len = encrypt_descriptor_data(desc, encoded_str, &encrypted_blob, + is_superencrypted_layer); + /* Get the encoded size plus a NUL terminating byte. */ + enc_b64_len = base64_encode_size(enc_len, BASE64_ENCODE_MULTILINE) + 1; + enc_b64 = tor_malloc_zero(enc_b64_len); + /* Base64 the encrypted blob before returning it. */ + ret_len = base64_encode(enc_b64, enc_b64_len, encrypted_blob, enc_len, + BASE64_ENCODE_MULTILINE); + /* Return length doesn't count the NUL byte. */ + tor_assert(ret_len == (enc_b64_len - 1)); + tor_free(encrypted_blob); + + return enc_b64; +} + +/* Generate and encode the superencrypted portion of <b>desc</b>. This also + * involves generating the encrypted portion of the descriptor, and performing + * the superencryption. A newly allocated NUL-terminated string pointer + * containing the encrypted encoded blob is put in encrypted_blob_out. Return 0 + * on success else a negative value. */ +static int +encode_superencrypted_data(const hs_descriptor_t *desc, + char **encrypted_blob_out) +{ + int ret = -1; + char *layer2_str = NULL; + char *layer2_b64_ciphertext = NULL; + char *layer1_str = NULL; + char *layer1_b64_ciphertext = NULL; + + tor_assert(desc); + tor_assert(encrypted_blob_out); + + /* Func logic: We first create the inner layer of the descriptor (layer2). + * We then encrypt it and use it to create the middle layer of the descriptor + * (layer1). Finally we superencrypt the middle layer and return it to our + * caller. */ + + /* Create inner descriptor layer */ + layer2_str = get_inner_encrypted_layer_plaintext(desc); + if (!layer2_str) { + goto err; + } + + /* Encrypt and b64 the inner layer */ + layer2_b64_ciphertext = encrypt_desc_data_and_base64(desc, layer2_str, 0); + if (!layer2_b64_ciphertext) { + goto err; + } + + /* Now create middle descriptor layer given the inner layer */ + layer1_str = get_outer_encrypted_layer_plaintext(desc,layer2_b64_ciphertext); + if (!layer1_str) { + goto err; + } + + /* Encrypt and base64 the middle layer */ + layer1_b64_ciphertext = encrypt_desc_data_and_base64(desc, layer1_str, 1); + if (!layer1_b64_ciphertext) { + goto err; + } + + /* Success! */ + ret = 0; + + err: + tor_free(layer1_str); + tor_free(layer2_str); + tor_free(layer2_b64_ciphertext); + + *encrypted_blob_out = layer1_b64_ciphertext; + return ret; +} + +/* Encode a v3 HS descriptor. Return 0 on success and set encoded_out to the + * newly allocated string of the encoded descriptor. On error, -1 is returned + * and encoded_out is untouched. */ +static int +desc_encode_v3(const hs_descriptor_t *desc, + const ed25519_keypair_t *signing_kp, char **encoded_out) +{ + int ret = -1; + char *encoded_str = NULL; + size_t encoded_len; + smartlist_t *lines = smartlist_new(); + + tor_assert(desc); + tor_assert(signing_kp); + tor_assert(encoded_out); + tor_assert(desc->plaintext_data.version == 3); + + if (BUG(desc->subcredential == NULL)) { + goto err; + } + + /* Build the non-encrypted values. */ + { + char *encoded_cert; + /* Encode certificate then create the first line of the descriptor. */ + if (desc->plaintext_data.signing_key_cert->cert_type + != CERT_TYPE_SIGNING_HS_DESC) { + log_err(LD_BUG, "HS descriptor signing key has an unexpected cert type " + "(%d)", (int) desc->plaintext_data.signing_key_cert->cert_type); + goto err; + } + if (tor_cert_encode_ed22519(desc->plaintext_data.signing_key_cert, + &encoded_cert) < 0) { + /* The function will print error logs. */ + goto err; + } + /* Create the hs descriptor line. */ + smartlist_add_asprintf(lines, "%s %" PRIu32, str_hs_desc, + desc->plaintext_data.version); + /* Add the descriptor lifetime line (in minutes). */ + smartlist_add_asprintf(lines, "%s %" PRIu32, str_lifetime, + desc->plaintext_data.lifetime_sec / 60); + /* Create the descriptor certificate line. */ + smartlist_add_asprintf(lines, "%s\n%s", str_desc_cert, encoded_cert); + tor_free(encoded_cert); + /* Create the revision counter line. */ + smartlist_add_asprintf(lines, "%s %" PRIu64, str_rev_counter, + desc->plaintext_data.revision_counter); + } + + /* Build the superencrypted data section. */ + { + char *enc_b64_blob=NULL; + if (encode_superencrypted_data(desc, &enc_b64_blob) < 0) { + goto err; + } + smartlist_add_asprintf(lines, + "%s\n" + "-----BEGIN MESSAGE-----\n" + "%s" + "-----END MESSAGE-----", + str_superencrypted, enc_b64_blob); + tor_free(enc_b64_blob); + } + + /* Join all lines in one string so we can generate a signature and append + * it to the descriptor. */ + encoded_str = smartlist_join_strings(lines, "\n", 1, &encoded_len); + + /* Sign all fields of the descriptor with our short term signing key. */ + { + ed25519_signature_t sig; + char ed_sig_b64[ED25519_SIG_BASE64_LEN + 1]; + if (ed25519_sign_prefixed(&sig, + (const uint8_t *) encoded_str, encoded_len, + str_desc_sig_prefix, signing_kp) < 0) { + log_warn(LD_BUG, "Can't sign encoded HS descriptor!"); + tor_free(encoded_str); + goto err; + } + if (ed25519_signature_to_base64(ed_sig_b64, &sig) < 0) { + log_warn(LD_BUG, "Can't base64 encode descriptor signature!"); + tor_free(encoded_str); + goto err; + } + /* Create the signature line. */ + smartlist_add_asprintf(lines, "%s %s", str_signature, ed_sig_b64); + } + /* Free previous string that we used so compute the signature. */ + tor_free(encoded_str); + encoded_str = smartlist_join_strings(lines, "\n", 1, NULL); + *encoded_out = encoded_str; + + if (strlen(encoded_str) >= hs_cache_get_max_descriptor_size()) { + log_warn(LD_GENERAL, "We just made an HS descriptor that's too big (%d)." + "Failing.", (int)strlen(encoded_str)); + tor_free(encoded_str); + goto err; + } + + /* XXX: Trigger a control port event. */ + + /* Success! */ + ret = 0; + + err: + SMARTLIST_FOREACH(lines, char *, l, tor_free(l)); + smartlist_free(lines); + return ret; +} + +/* === DECODING === */ + +/* Given an encoded string of the link specifiers, return a newly allocated + * list of decoded link specifiers. Return NULL on error. */ +STATIC smartlist_t * +decode_link_specifiers(const char *encoded) +{ + int decoded_len; + size_t encoded_len, i; + uint8_t *decoded; + smartlist_t *results = NULL; + link_specifier_list_t *specs = NULL; + + tor_assert(encoded); + + encoded_len = strlen(encoded); + decoded = tor_malloc(encoded_len); + decoded_len = base64_decode((char *) decoded, encoded_len, encoded, + encoded_len); + if (decoded_len < 0) { + goto err; + } + + if (link_specifier_list_parse(&specs, decoded, + (size_t) decoded_len) < decoded_len) { + goto err; + } + tor_assert(specs); + results = smartlist_new(); + + for (i = 0; i < link_specifier_list_getlen_spec(specs); i++) { + hs_desc_link_specifier_t *hs_spec; + link_specifier_t *ls = link_specifier_list_get_spec(specs, i); + tor_assert(ls); + + hs_spec = tor_malloc_zero(sizeof(*hs_spec)); + hs_spec->type = link_specifier_get_ls_type(ls); + switch (hs_spec->type) { + case LS_IPV4: + tor_addr_from_ipv4h(&hs_spec->u.ap.addr, + link_specifier_get_un_ipv4_addr(ls)); + hs_spec->u.ap.port = link_specifier_get_un_ipv4_port(ls); + break; + case LS_IPV6: + tor_addr_from_ipv6_bytes(&hs_spec->u.ap.addr, (const char *) + link_specifier_getarray_un_ipv6_addr(ls)); + hs_spec->u.ap.port = link_specifier_get_un_ipv6_port(ls); + break; + case LS_LEGACY_ID: + /* Both are known at compile time so let's make sure they are the same + * else we can copy memory out of bound. */ + tor_assert(link_specifier_getlen_un_legacy_id(ls) == + sizeof(hs_spec->u.legacy_id)); + memcpy(hs_spec->u.legacy_id, link_specifier_getarray_un_legacy_id(ls), + sizeof(hs_spec->u.legacy_id)); + break; + case LS_ED25519_ID: + /* Both are known at compile time so let's make sure they are the same + * else we can copy memory out of bound. */ + tor_assert(link_specifier_getlen_un_ed25519_id(ls) == + sizeof(hs_spec->u.ed25519_id)); + memcpy(hs_spec->u.ed25519_id, + link_specifier_getconstarray_un_ed25519_id(ls), + sizeof(hs_spec->u.ed25519_id)); + break; + default: + tor_free(hs_spec); + goto err; + } + + smartlist_add(results, hs_spec); + } + + goto done; + err: + if (results) { + SMARTLIST_FOREACH(results, hs_desc_link_specifier_t *, s, tor_free(s)); + smartlist_free(results); + results = NULL; + } + done: + link_specifier_list_free(specs); + tor_free(decoded); + return results; +} + +/* Given a list of authentication types, decode it and put it in the encrypted + * data section. Return 1 if we at least know one of the type or 0 if we know + * none of them. */ +static int +decode_auth_type(hs_desc_encrypted_data_t *desc, const char *list) +{ + int match = 0; + + tor_assert(desc); + tor_assert(list); + + desc->intro_auth_types = smartlist_new(); + smartlist_split_string(desc->intro_auth_types, list, " ", 0, 0); + + /* Validate the types that we at least know about one. */ + SMARTLIST_FOREACH_BEGIN(desc->intro_auth_types, const char *, auth) { + for (int idx = 0; intro_auth_types[idx].identifier; idx++) { + if (!strncmp(auth, intro_auth_types[idx].identifier, + strlen(intro_auth_types[idx].identifier))) { + match = 1; + break; + } + } + } SMARTLIST_FOREACH_END(auth); + + return match; +} + +/* Parse a space-delimited list of integers representing CREATE2 formats into + * the bitfield in hs_desc_encrypted_data_t. Ignore unrecognized values. */ +static void +decode_create2_list(hs_desc_encrypted_data_t *desc, const char *list) +{ + smartlist_t *tokens; + + tor_assert(desc); + tor_assert(list); + + tokens = smartlist_new(); + smartlist_split_string(tokens, list, " ", 0, 0); + + SMARTLIST_FOREACH_BEGIN(tokens, char *, s) { + int ok; + unsigned long type = tor_parse_ulong(s, 10, 1, UINT16_MAX, &ok, NULL); + if (!ok) { + log_warn(LD_REND, "Unparseable value %s in create2 list", escaped(s)); + continue; + } + switch (type) { + case ONION_HANDSHAKE_TYPE_NTOR: + desc->create2_ntor = 1; + break; + default: + /* We deliberately ignore unsupported handshake types */ + continue; + } + } SMARTLIST_FOREACH_END(s); + + SMARTLIST_FOREACH(tokens, char *, s, tor_free(s)); + smartlist_free(tokens); +} + +/* Given a certificate, validate the certificate for certain conditions which + * are if the given type matches the cert's one, if the signing key is + * included and if the that key was actually used to sign the certificate. + * + * Return 1 iff if all conditions pass or 0 if one of them fails. */ +STATIC int +cert_is_valid(tor_cert_t *cert, uint8_t type, const char *log_obj_type) +{ + tor_assert(log_obj_type); + + if (cert == NULL) { + log_warn(LD_REND, "Certificate for %s couldn't be parsed.", log_obj_type); + goto err; + } + if (cert->cert_type != type) { + log_warn(LD_REND, "Invalid cert type %02x for %s.", cert->cert_type, + log_obj_type); + goto err; + } + /* All certificate must have its signing key included. */ + if (!cert->signing_key_included) { + log_warn(LD_REND, "Signing key is NOT included for %s.", log_obj_type); + goto err; + } + /* The following will not only check if the signature matches but also the + * expiration date and overall validity. */ + if (tor_cert_checksig(cert, &cert->signing_key, approx_time()) < 0) { + log_warn(LD_REND, "Invalid signature for %s: %s", log_obj_type, + tor_cert_describe_signature_status(cert)); + goto err; + } + + return 1; + err: + return 0; +} + +/* Given some binary data, try to parse it to get a certificate object. If we + * have a valid cert, validate it using the given wanted type. On error, print + * a log using the err_msg has the certificate identifier adding semantic to + * the log and cert_out is set to NULL. On success, 0 is returned and cert_out + * points to a newly allocated certificate object. */ +static int +cert_parse_and_validate(tor_cert_t **cert_out, const char *data, + size_t data_len, unsigned int cert_type_wanted, + const char *err_msg) +{ + tor_cert_t *cert; + + tor_assert(cert_out); + tor_assert(data); + tor_assert(err_msg); + + /* Parse certificate. */ + cert = tor_cert_parse((const uint8_t *) data, data_len); + if (!cert) { + log_warn(LD_REND, "Certificate for %s couldn't be parsed.", err_msg); + goto err; + } + + /* Validate certificate. */ + if (!cert_is_valid(cert, cert_type_wanted, err_msg)) { + goto err; + } + + *cert_out = cert; + return 0; + + err: + tor_cert_free(cert); + *cert_out = NULL; + return -1; +} + +/* Return true iff the given length of the encrypted data of a descriptor + * passes validation. */ +STATIC int +encrypted_data_length_is_valid(size_t len) +{ + /* Make sure there is enough data for the salt and the mac. The equality is + there to ensure that there is at least one byte of encrypted data. */ + if (len <= HS_DESC_ENCRYPTED_SALT_LEN + DIGEST256_LEN) { + log_warn(LD_REND, "Length of descriptor's encrypted data is too small. " + "Got %lu but minimum value is %d", + (unsigned long)len, HS_DESC_ENCRYPTED_SALT_LEN + DIGEST256_LEN); + goto err; + } + + return 1; + err: + return 0; +} + +/** Decrypt an encrypted descriptor layer at <b>encrypted_blob</b> of size + * <b>encrypted_blob_size</b>. Use the descriptor object <b>desc</b> to + * generate the right decryption keys; set <b>decrypted_out</b> to the + * plaintext. If <b>is_superencrypted_layer</b> is set, this is the outter + * encrypted layer of the descriptor. + * + * On any error case, including an empty output, return 0 and set + * *<b>decrypted_out</b> to NULL. + */ +MOCK_IMPL(STATIC size_t, +decrypt_desc_layer,(const hs_descriptor_t *desc, + const uint8_t *encrypted_blob, + size_t encrypted_blob_size, + int is_superencrypted_layer, + char **decrypted_out)) +{ + uint8_t *decrypted = NULL; + uint8_t secret_key[HS_DESC_ENCRYPTED_KEY_LEN], secret_iv[CIPHER_IV_LEN]; + uint8_t mac_key[DIGEST256_LEN], our_mac[DIGEST256_LEN]; + const uint8_t *salt, *encrypted, *desc_mac; + size_t encrypted_len, result_len = 0; + + tor_assert(decrypted_out); + tor_assert(desc); + tor_assert(encrypted_blob); + + /* Construction is as follow: SALT | ENCRYPTED_DATA | MAC . + * Make sure we have enough space for all these things. */ + if (!encrypted_data_length_is_valid(encrypted_blob_size)) { + goto err; + } + + /* Start of the blob thus the salt. */ + salt = encrypted_blob; + + /* Next is the encrypted data. */ + encrypted = encrypted_blob + HS_DESC_ENCRYPTED_SALT_LEN; + encrypted_len = encrypted_blob_size - + (HS_DESC_ENCRYPTED_SALT_LEN + DIGEST256_LEN); + tor_assert(encrypted_len > 0); /* guaranteed by the check above */ + + /* And last comes the MAC. */ + desc_mac = encrypted_blob + encrypted_blob_size - DIGEST256_LEN; + + /* KDF construction resulting in a key from which the secret key, IV and MAC + * key are extracted which is what we need for the decryption. */ + build_secret_key_iv_mac(desc, salt, HS_DESC_ENCRYPTED_SALT_LEN, + secret_key, sizeof(secret_key), + secret_iv, sizeof(secret_iv), + mac_key, sizeof(mac_key), + is_superencrypted_layer); + + /* Build MAC. */ + build_mac(mac_key, sizeof(mac_key), salt, HS_DESC_ENCRYPTED_SALT_LEN, + encrypted, encrypted_len, our_mac, sizeof(our_mac)); + memwipe(mac_key, 0, sizeof(mac_key)); + /* Verify MAC; MAC is H(mac_key || salt || encrypted) + * + * This is a critical check that is making sure the computed MAC matches the + * one in the descriptor. */ + if (!tor_memeq(our_mac, desc_mac, sizeof(our_mac))) { + log_warn(LD_REND, "Encrypted service descriptor MAC check failed"); + goto err; + } + + { + /* Decrypt. Here we are assured that the encrypted length is valid for + * decryption. */ + crypto_cipher_t *cipher; + + cipher = crypto_cipher_new_with_iv_and_bits(secret_key, secret_iv, + HS_DESC_ENCRYPTED_BIT_SIZE); + /* Extra byte for the NUL terminated byte. */ + decrypted = tor_malloc_zero(encrypted_len + 1); + crypto_cipher_decrypt(cipher, (char *) decrypted, + (const char *) encrypted, encrypted_len); + crypto_cipher_free(cipher); + } + + { + /* Adjust length to remove NUL padding bytes */ + uint8_t *end = memchr(decrypted, 0, encrypted_len); + result_len = encrypted_len; + if (end) { + result_len = end - decrypted; + } + } + + if (result_len == 0) { + /* Treat this as an error, so that somebody will free the output. */ + goto err; + } + + /* Make sure to NUL terminate the string. */ + decrypted[encrypted_len] = '\0'; + *decrypted_out = (char *) decrypted; + goto done; + + err: + if (decrypted) { + tor_free(decrypted); + } + *decrypted_out = NULL; + result_len = 0; + + done: + memwipe(secret_key, 0, sizeof(secret_key)); + memwipe(secret_iv, 0, sizeof(secret_iv)); + return result_len; +} + +/* Basic validation that the superencrypted client auth portion of the + * descriptor is well-formed and recognized. Return True if so, otherwise + * return False. */ +static int +superencrypted_auth_data_is_valid(smartlist_t *tokens) +{ + /* XXX: This is just basic validation for now. When we implement client auth, + we can refactor this function so that it actually parses and saves the + data. */ + + { /* verify desc auth type */ + const directory_token_t *tok; + tok = find_by_keyword(tokens, R3_DESC_AUTH_TYPE); + tor_assert(tok->n_args >= 1); + if (strcmp(tok->args[0], "x25519")) { + log_warn(LD_DIR, "Unrecognized desc auth type"); + return 0; + } + } + + { /* verify desc auth key */ + const directory_token_t *tok; + curve25519_public_key_t k; + tok = find_by_keyword(tokens, R3_DESC_AUTH_KEY); + tor_assert(tok->n_args >= 1); + if (curve25519_public_from_base64(&k, tok->args[0]) < 0) { + log_warn(LD_DIR, "Bogus desc auth key in HS desc"); + return 0; + } + } + + /* verify desc auth client items */ + SMARTLIST_FOREACH_BEGIN(tokens, const directory_token_t *, tok) { + if (tok->tp == R3_DESC_AUTH_CLIENT) { + tor_assert(tok->n_args >= 3); + } + } SMARTLIST_FOREACH_END(tok); + + return 1; +} + +/* Parse <b>message</b>, the plaintext of the superencrypted portion of an HS + * descriptor. Set <b>encrypted_out</b> to the encrypted blob, and return its + * size */ +STATIC size_t +decode_superencrypted(const char *message, size_t message_len, + uint8_t **encrypted_out) +{ + int retval = 0; + memarea_t *area = NULL; + smartlist_t *tokens = NULL; + + area = memarea_new(); + tokens = smartlist_new(); + if (tokenize_string(area, message, message + message_len, tokens, + hs_desc_superencrypted_v3_token_table, 0) < 0) { + log_warn(LD_REND, "Superencrypted portion is not parseable"); + goto err; + } + + /* Do some rudimentary validation of the authentication data */ + if (!superencrypted_auth_data_is_valid(tokens)) { + log_warn(LD_REND, "Invalid auth data"); + goto err; + } + + /* Extract the encrypted data section. */ + { + const directory_token_t *tok; + tok = find_by_keyword(tokens, R3_ENCRYPTED); + tor_assert(tok->object_body); + if (strcmp(tok->object_type, "MESSAGE") != 0) { + log_warn(LD_REND, "Desc superencrypted data section is invalid"); + goto err; + } + /* Make sure the length of the encrypted blob is valid. */ + if (!encrypted_data_length_is_valid(tok->object_size)) { + goto err; + } + + /* Copy the encrypted blob to the descriptor object so we can handle it + * latter if needed. */ + tor_assert(tok->object_size <= INT_MAX); + *encrypted_out = tor_memdup(tok->object_body, tok->object_size); + retval = (int) tok->object_size; + } + + err: + SMARTLIST_FOREACH(tokens, directory_token_t *, t, token_clear(t)); + smartlist_free(tokens); + if (area) { + memarea_drop_all(area); + } + + return retval; +} + +/* Decrypt both the superencrypted and the encrypted section of the descriptor + * using the given descriptor object <b>desc</b>. A newly allocated NUL + * terminated string is put in decrypted_out which contains the inner encrypted + * layer of the descriptor. Return the length of decrypted_out on success else + * 0 is returned and decrypted_out is set to NULL. */ +static size_t +desc_decrypt_all(const hs_descriptor_t *desc, char **decrypted_out) +{ + size_t decrypted_len = 0; + size_t encrypted_len = 0; + size_t superencrypted_len = 0; + char *superencrypted_plaintext = NULL; + uint8_t *encrypted_blob = NULL; + + /** Function logic: This function takes us from the descriptor header to the + * inner encrypted layer, by decrypting and decoding the middle descriptor + * layer. In the end we return the contents of the inner encrypted layer to + * our caller. */ + + /* 1. Decrypt middle layer of descriptor */ + superencrypted_len = decrypt_desc_layer(desc, + desc->plaintext_data.superencrypted_blob, + desc->plaintext_data.superencrypted_blob_size, + 1, + &superencrypted_plaintext); + if (!superencrypted_len) { + log_warn(LD_REND, "Decrypting superencrypted desc failed."); + goto err; + } + tor_assert(superencrypted_plaintext); + + /* 2. Parse "superencrypted" */ + encrypted_len = decode_superencrypted(superencrypted_plaintext, + superencrypted_len, + &encrypted_blob); + if (!encrypted_len) { + log_warn(LD_REND, "Decrypting encrypted desc failed."); + goto err; + } + tor_assert(encrypted_blob); + + /* 3. Decrypt "encrypted" and set decrypted_out */ + char *decrypted_desc; + decrypted_len = decrypt_desc_layer(desc, + encrypted_blob, encrypted_len, + 0, &decrypted_desc); + if (!decrypted_len) { + log_warn(LD_REND, "Decrypting encrypted desc failed."); + goto err; + } + tor_assert(decrypted_desc); + + *decrypted_out = decrypted_desc; + + err: + tor_free(superencrypted_plaintext); + tor_free(encrypted_blob); + + return decrypted_len; +} + +/* Given the token tok for an intro point legacy key, the list of tokens, the + * introduction point ip being decoded and the descriptor desc from which it + * comes from, decode the legacy key and set the intro point object. Return 0 + * on success else -1 on failure. */ +static int +decode_intro_legacy_key(const directory_token_t *tok, + smartlist_t *tokens, + hs_desc_intro_point_t *ip, + const hs_descriptor_t *desc) +{ + tor_assert(tok); + tor_assert(tokens); + tor_assert(ip); + tor_assert(desc); + + if (!crypto_pk_public_exponent_ok(tok->key)) { + log_warn(LD_REND, "Introduction point legacy key is invalid"); + goto err; + } + ip->legacy.key = crypto_pk_dup_key(tok->key); + /* Extract the legacy cross certification cert which MUST be present if we + * have a legacy key. */ + tok = find_opt_by_keyword(tokens, R3_INTRO_LEGACY_KEY_CERT); + if (!tok) { + log_warn(LD_REND, "Introduction point legacy key cert is missing"); + goto err; + } + tor_assert(tok->object_body); + if (strcmp(tok->object_type, "CROSSCERT")) { + /* Info level because this might be an unknown field that we should + * ignore. */ + log_info(LD_REND, "Introduction point legacy encryption key " + "cross-certification has an unknown format."); + goto err; + } + /* Keep a copy of the certificate. */ + ip->legacy.cert.encoded = tor_memdup(tok->object_body, tok->object_size); + ip->legacy.cert.len = tok->object_size; + /* The check on the expiration date is for the entire lifetime of a + * certificate which is 24 hours. However, a descriptor has a maximum + * lifetime of 12 hours meaning we have a 12h difference between the two + * which ultimately accomodate the clock skewed client. */ + if (rsa_ed25519_crosscert_check(ip->legacy.cert.encoded, + ip->legacy.cert.len, ip->legacy.key, + &desc->plaintext_data.signing_pubkey, + approx_time() - HS_DESC_CERT_LIFETIME)) { + log_warn(LD_REND, "Unable to check cross-certification on the " + "introduction point legacy encryption key."); + ip->cross_certified = 0; + goto err; + } + + /* Success. */ + return 0; + err: + return -1; +} + +/* Dig into the descriptor <b>tokens</b> to find the onion key we should use + * for this intro point, and set it into <b>onion_key_out</b>. Return 0 if it + * was found and well-formed, otherwise return -1 in case of errors. */ +static int +set_intro_point_onion_key(curve25519_public_key_t *onion_key_out, + const smartlist_t *tokens) +{ + int retval = -1; + smartlist_t *onion_keys = NULL; + + tor_assert(onion_key_out); + + onion_keys = find_all_by_keyword(tokens, R3_INTRO_ONION_KEY); + if (!onion_keys) { + log_warn(LD_REND, "Descriptor did not contain intro onion keys"); + goto err; + } + + SMARTLIST_FOREACH_BEGIN(onion_keys, directory_token_t *, tok) { + /* This field is using GE(2) so for possible forward compatibility, we + * accept more fields but must be at least 2. */ + tor_assert(tok->n_args >= 2); + + /* Try to find an ntor key, it's the only recognized type right now */ + if (!strcmp(tok->args[0], "ntor")) { + if (curve25519_public_from_base64(onion_key_out, tok->args[1]) < 0) { + log_warn(LD_REND, "Introduction point ntor onion-key is invalid"); + goto err; + } + /* Got the onion key! Set the appropriate retval */ + retval = 0; + } + } SMARTLIST_FOREACH_END(tok); + + /* Log an error if we didn't find it :( */ + if (retval < 0) { + log_warn(LD_REND, "Descriptor did not contain ntor onion keys"); + } + + err: + smartlist_free(onion_keys); + return retval; +} + +/* Given the start of a section and the end of it, decode a single + * introduction point from that section. Return a newly allocated introduction + * point object containing the decoded data. Return NULL if the section can't + * be decoded. */ +STATIC hs_desc_intro_point_t * +decode_introduction_point(const hs_descriptor_t *desc, const char *start) +{ + hs_desc_intro_point_t *ip = NULL; + memarea_t *area = NULL; + smartlist_t *tokens = NULL; + const directory_token_t *tok; + + tor_assert(desc); + tor_assert(start); + + area = memarea_new(); + tokens = smartlist_new(); + if (tokenize_string(area, start, start + strlen(start), + tokens, hs_desc_intro_point_v3_token_table, 0) < 0) { + log_warn(LD_REND, "Introduction point is not parseable"); + goto err; + } + + /* Ok we seem to have a well formed section containing enough tokens to + * parse. Allocate our IP object and try to populate it. */ + ip = hs_desc_intro_point_new(); + + /* "introduction-point" SP link-specifiers NL */ + tok = find_by_keyword(tokens, R3_INTRODUCTION_POINT); + tor_assert(tok->n_args == 1); + /* Our constructor creates this list by default so free it. */ + smartlist_free(ip->link_specifiers); + ip->link_specifiers = decode_link_specifiers(tok->args[0]); + if (!ip->link_specifiers) { + log_warn(LD_REND, "Introduction point has invalid link specifiers"); + goto err; + } + + /* "onion-key" SP ntor SP key NL */ + if (set_intro_point_onion_key(&ip->onion_key, tokens) < 0) { + goto err; + } + + /* "auth-key" NL certificate NL */ + tok = find_by_keyword(tokens, R3_INTRO_AUTH_KEY); + tor_assert(tok->object_body); + if (strcmp(tok->object_type, "ED25519 CERT")) { + log_warn(LD_REND, "Unexpected object type for introduction auth key"); + goto err; + } + /* Parse cert and do some validation. */ + if (cert_parse_and_validate(&ip->auth_key_cert, tok->object_body, + tok->object_size, CERT_TYPE_AUTH_HS_IP_KEY, + "introduction point auth-key") < 0) { + goto err; + } + /* Validate authentication certificate with descriptor signing key. */ + if (tor_cert_checksig(ip->auth_key_cert, + &desc->plaintext_data.signing_pubkey, 0) < 0) { + log_warn(LD_REND, "Invalid authentication key signature: %s", + tor_cert_describe_signature_status(ip->auth_key_cert)); + goto err; + } + + /* Exactly one "enc-key" SP "ntor" SP key NL */ + tok = find_by_keyword(tokens, R3_INTRO_ENC_KEY); + if (!strcmp(tok->args[0], "ntor")) { + /* This field is using GE(2) so for possible forward compatibility, we + * accept more fields but must be at least 2. */ + tor_assert(tok->n_args >= 2); + + if (curve25519_public_from_base64(&ip->enc_key, tok->args[1]) < 0) { + log_warn(LD_REND, "Introduction point ntor enc-key is invalid"); + goto err; + } + } else { + /* Unknown key type so we can't use that introduction point. */ + log_warn(LD_REND, "Introduction point encryption key is unrecognized."); + goto err; + } + + /* Exactly once "enc-key-cert" NL certificate NL */ + tok = find_by_keyword(tokens, R3_INTRO_ENC_KEY_CERT); + tor_assert(tok->object_body); + /* Do the cross certification. */ + if (strcmp(tok->object_type, "ED25519 CERT")) { + log_warn(LD_REND, "Introduction point ntor encryption key " + "cross-certification has an unknown format."); + goto err; + } + if (cert_parse_and_validate(&ip->enc_key_cert, tok->object_body, + tok->object_size, CERT_TYPE_CROSS_HS_IP_KEYS, + "introduction point enc-key-cert") < 0) { + goto err; + } + if (tor_cert_checksig(ip->enc_key_cert, + &desc->plaintext_data.signing_pubkey, 0) < 0) { + log_warn(LD_REND, "Invalid encryption key signature: %s", + tor_cert_describe_signature_status(ip->enc_key_cert)); + goto err; + } + /* It is successfully cross certified. Flag the object. */ + ip->cross_certified = 1; + + /* Do we have a "legacy-key" SP key NL ?*/ + tok = find_opt_by_keyword(tokens, R3_INTRO_LEGACY_KEY); + if (tok) { + if (decode_intro_legacy_key(tok, tokens, ip, desc) < 0) { + goto err; + } + } + + /* Introduction point has been parsed successfully. */ + goto done; + + err: + hs_desc_intro_point_free(ip); + ip = NULL; + + done: + SMARTLIST_FOREACH(tokens, directory_token_t *, t, token_clear(t)); + smartlist_free(tokens); + if (area) { + memarea_drop_all(area); + } + + return ip; +} + +/* Given a descriptor string at <b>data</b>, decode all possible introduction + * points that we can find. Add the introduction point object to desc_enc as we + * find them. This function can't fail and it is possible that zero + * introduction points can be decoded. */ +static void +decode_intro_points(const hs_descriptor_t *desc, + hs_desc_encrypted_data_t *desc_enc, + const char *data) +{ + smartlist_t *chunked_desc = smartlist_new(); + smartlist_t *intro_points = smartlist_new(); + + tor_assert(desc); + tor_assert(desc_enc); + tor_assert(data); + tor_assert(desc_enc->intro_points); + + /* Take the desc string, and extract the intro point substrings out of it */ + { + /* Split the descriptor string using the intro point header as delimiter */ + smartlist_split_string(chunked_desc, data, str_intro_point_start, 0, 0); + + /* Check if there are actually any intro points included. The first chunk + * should be other descriptor fields (e.g. create2-formats), so it's not an + * intro point. */ + if (smartlist_len(chunked_desc) < 2) { + goto done; + } + } + + /* Take the intro point substrings, and prepare them for parsing */ + { + int i = 0; + /* Prepend the introduction-point header to all the chunks, since + smartlist_split_string() devoured it. */ + SMARTLIST_FOREACH_BEGIN(chunked_desc, char *, chunk) { + /* Ignore first chunk. It's other descriptor fields. */ + if (i++ == 0) { + continue; + } + + smartlist_add_asprintf(intro_points, "%s %s", str_intro_point, chunk); + } SMARTLIST_FOREACH_END(chunk); + } + + /* Parse the intro points! */ + SMARTLIST_FOREACH_BEGIN(intro_points, const char *, intro_point) { + hs_desc_intro_point_t *ip = decode_introduction_point(desc, intro_point); + if (!ip) { + /* Malformed introduction point section. We'll ignore this introduction + * point and continue parsing. New or unknown fields are possible for + * forward compatibility. */ + continue; + } + smartlist_add(desc_enc->intro_points, ip); + } SMARTLIST_FOREACH_END(intro_point); + + done: + SMARTLIST_FOREACH(chunked_desc, char *, a, tor_free(a)); + smartlist_free(chunked_desc); + SMARTLIST_FOREACH(intro_points, char *, a, tor_free(a)); + smartlist_free(intro_points); +} +/* Return 1 iff the given base64 encoded signature in b64_sig from the encoded + * descriptor in encoded_desc validates the descriptor content. */ +STATIC int +desc_sig_is_valid(const char *b64_sig, + const ed25519_public_key_t *signing_pubkey, + const char *encoded_desc, size_t encoded_len) +{ + int ret = 0; + ed25519_signature_t sig; + const char *sig_start; + + tor_assert(b64_sig); + tor_assert(signing_pubkey); + tor_assert(encoded_desc); + /* Verifying nothing won't end well :). */ + tor_assert(encoded_len > 0); + + /* Signature length check. */ + if (strlen(b64_sig) != ED25519_SIG_BASE64_LEN) { + log_warn(LD_REND, "Service descriptor has an invalid signature length." + "Exptected %d but got %lu", + ED25519_SIG_BASE64_LEN, (unsigned long) strlen(b64_sig)); + goto err; + } + + /* First, convert base64 blob to an ed25519 signature. */ + if (ed25519_signature_from_base64(&sig, b64_sig) != 0) { + log_warn(LD_REND, "Service descriptor does not contain a valid " + "signature"); + goto err; + } + + /* Find the start of signature. */ + sig_start = tor_memstr(encoded_desc, encoded_len, "\n" str_signature " "); + /* Getting here means the token parsing worked for the signature so if we + * can't find the start of the signature, we have a code flow issue. */ + if (!sig_start) { + log_warn(LD_GENERAL, "Malformed signature line. Rejecting."); + goto err; + } + /* Skip newline, it has to go in the signature check. */ + sig_start++; + + /* Validate signature with the full body of the descriptor. */ + if (ed25519_checksig_prefixed(&sig, + (const uint8_t *) encoded_desc, + sig_start - encoded_desc, + str_desc_sig_prefix, + signing_pubkey) != 0) { + log_warn(LD_REND, "Invalid signature on service descriptor"); + goto err; + } + /* Valid signature! All is good. */ + ret = 1; + + err: + return ret; +} + +/* Decode descriptor plaintext data for version 3. Given a list of tokens, an + * allocated plaintext object that will be populated and the encoded + * descriptor with its length. The last one is needed for signature + * verification. Unknown tokens are simply ignored so this won't error on + * unknowns but requires that all v3 token be present and valid. + * + * Return 0 on success else a negative value. */ +static int +desc_decode_plaintext_v3(smartlist_t *tokens, + hs_desc_plaintext_data_t *desc, + const char *encoded_desc, size_t encoded_len) +{ + int ok; + directory_token_t *tok; + + tor_assert(tokens); + tor_assert(desc); + /* Version higher could still use this function to decode most of the + * descriptor and then they decode the extra part. */ + tor_assert(desc->version >= 3); + + /* Descriptor lifetime parsing. */ + tok = find_by_keyword(tokens, R3_DESC_LIFETIME); + tor_assert(tok->n_args == 1); + desc->lifetime_sec = (uint32_t) tor_parse_ulong(tok->args[0], 10, 0, + UINT32_MAX, &ok, NULL); + if (!ok) { + log_warn(LD_REND, "Service descriptor lifetime value is invalid"); + goto err; + } + /* Put it from minute to second. */ + desc->lifetime_sec *= 60; + if (desc->lifetime_sec > HS_DESC_MAX_LIFETIME) { + log_warn(LD_REND, "Service descriptor lifetime is too big. " + "Got %" PRIu32 " but max is %d", + desc->lifetime_sec, HS_DESC_MAX_LIFETIME); + goto err; + } + + /* Descriptor signing certificate. */ + tok = find_by_keyword(tokens, R3_DESC_SIGNING_CERT); + tor_assert(tok->object_body); + /* Expecting a prop220 cert with the signing key extension, which contains + * the blinded public key. */ + if (strcmp(tok->object_type, "ED25519 CERT") != 0) { + log_warn(LD_REND, "Service descriptor signing cert wrong type (%s)", + escaped(tok->object_type)); + goto err; + } + if (cert_parse_and_validate(&desc->signing_key_cert, tok->object_body, + tok->object_size, CERT_TYPE_SIGNING_HS_DESC, + "service descriptor signing key") < 0) { + goto err; + } + + /* Copy the public keys into signing_pubkey and blinded_pubkey */ + memcpy(&desc->signing_pubkey, &desc->signing_key_cert->signed_key, + sizeof(ed25519_public_key_t)); + memcpy(&desc->blinded_pubkey, &desc->signing_key_cert->signing_key, + sizeof(ed25519_public_key_t)); + + /* Extract revision counter value. */ + tok = find_by_keyword(tokens, R3_REVISION_COUNTER); + tor_assert(tok->n_args == 1); + desc->revision_counter = tor_parse_uint64(tok->args[0], 10, 0, + UINT64_MAX, &ok, NULL); + if (!ok) { + log_warn(LD_REND, "Service descriptor revision-counter is invalid"); + goto err; + } + + /* Extract the encrypted data section. */ + tok = find_by_keyword(tokens, R3_SUPERENCRYPTED); + tor_assert(tok->object_body); + if (strcmp(tok->object_type, "MESSAGE") != 0) { + log_warn(LD_REND, "Service descriptor encrypted data section is invalid"); + goto err; + } + /* Make sure the length of the encrypted blob is valid. */ + if (!encrypted_data_length_is_valid(tok->object_size)) { + goto err; + } + + /* Copy the encrypted blob to the descriptor object so we can handle it + * latter if needed. */ + desc->superencrypted_blob = tor_memdup(tok->object_body, tok->object_size); + desc->superencrypted_blob_size = tok->object_size; + + /* Extract signature and verify it. */ + tok = find_by_keyword(tokens, R3_SIGNATURE); + tor_assert(tok->n_args == 1); + /* First arg here is the actual encoded signature. */ + if (!desc_sig_is_valid(tok->args[0], &desc->signing_pubkey, + encoded_desc, encoded_len)) { + goto err; + } + + return 0; + + err: + return -1; +} + +/* Decode the version 3 encrypted section of the given descriptor desc. The + * desc_encrypted_out will be populated with the decoded data. Return 0 on + * success else -1. */ +static int +desc_decode_encrypted_v3(const hs_descriptor_t *desc, + hs_desc_encrypted_data_t *desc_encrypted_out) +{ + int result = -1; + char *message = NULL; + size_t message_len; + memarea_t *area = NULL; + directory_token_t *tok; + smartlist_t *tokens = NULL; + + tor_assert(desc); + tor_assert(desc_encrypted_out); + + /* Decrypt the superencrypted data that is located in the plaintext section + * in the descriptor as a blob of bytes. */ + message_len = desc_decrypt_all(desc, &message); + if (!message_len) { + log_warn(LD_REND, "Service descriptor decryption failed."); + goto err; + } + tor_assert(message); + + area = memarea_new(); + tokens = smartlist_new(); + if (tokenize_string(area, message, message + message_len, + tokens, hs_desc_encrypted_v3_token_table, 0) < 0) { + log_warn(LD_REND, "Encrypted service descriptor is not parseable."); + goto err; + } + + /* CREATE2 supported cell format. It's mandatory. */ + tok = find_by_keyword(tokens, R3_CREATE2_FORMATS); + tor_assert(tok); + decode_create2_list(desc_encrypted_out, tok->args[0]); + /* Must support ntor according to the specification */ + if (!desc_encrypted_out->create2_ntor) { + log_warn(LD_REND, "Service create2-formats does not include ntor."); + goto err; + } + + /* Authentication type. It's optional but only once. */ + tok = find_opt_by_keyword(tokens, R3_INTRO_AUTH_REQUIRED); + if (tok) { + if (!decode_auth_type(desc_encrypted_out, tok->args[0])) { + log_warn(LD_REND, "Service descriptor authentication type has " + "invalid entry(ies)."); + goto err; + } + } + + /* Is this service a single onion service? */ + tok = find_opt_by_keyword(tokens, R3_SINGLE_ONION_SERVICE); + if (tok) { + desc_encrypted_out->single_onion_service = 1; + } + + /* Initialize the descriptor's introduction point list before we start + * decoding. Having 0 intro point is valid. Then decode them all. */ + desc_encrypted_out->intro_points = smartlist_new(); + decode_intro_points(desc, desc_encrypted_out, message); + + /* Validation of maximum introduction points allowed. */ + if (smartlist_len(desc_encrypted_out->intro_points) > + HS_CONFIG_V3_MAX_INTRO_POINTS) { + log_warn(LD_REND, "Service descriptor contains too many introduction " + "points. Maximum allowed is %d but we have %d", + HS_CONFIG_V3_MAX_INTRO_POINTS, + smartlist_len(desc_encrypted_out->intro_points)); + goto err; + } + + /* NOTE: Unknown fields are allowed because this function could be used to + * decode other descriptor version. */ + + result = 0; + goto done; + + err: + tor_assert(result < 0); + desc_encrypted_data_free_contents(desc_encrypted_out); + + done: + if (tokens) { + SMARTLIST_FOREACH(tokens, directory_token_t *, t, token_clear(t)); + smartlist_free(tokens); + } + if (area) { + memarea_drop_all(area); + } + if (message) { + tor_free(message); + } + return result; +} + +/* Table of encrypted decode function version specific. The function are + * indexed by the version number so v3 callback is at index 3 in the array. */ +static int + (*decode_encrypted_handlers[])( + const hs_descriptor_t *desc, + hs_desc_encrypted_data_t *desc_encrypted) = +{ + /* v0 */ NULL, /* v1 */ NULL, /* v2 */ NULL, + desc_decode_encrypted_v3, +}; + +/* Decode the encrypted data section of the given descriptor and store the + * data in the given encrypted data object. Return 0 on success else a + * negative value on error. */ +int +hs_desc_decode_encrypted(const hs_descriptor_t *desc, + hs_desc_encrypted_data_t *desc_encrypted) +{ + int ret; + uint32_t version; + + tor_assert(desc); + /* Ease our life a bit. */ + version = desc->plaintext_data.version; + tor_assert(desc_encrypted); + /* Calling this function without an encrypted blob to parse is a code flow + * error. The plaintext parsing should never succeed in the first place + * without an encrypted section. */ + tor_assert(desc->plaintext_data.superencrypted_blob); + /* Let's make sure we have a supported version as well. By correctly parsing + * the plaintext, this should not fail. */ + if (BUG(!hs_desc_is_supported_version(version))) { + ret = -1; + goto err; + } + /* Extra precaution. Having no handler for the supported version should + * never happened else we forgot to add it but we bumped the version. */ + tor_assert(ARRAY_LENGTH(decode_encrypted_handlers) >= version); + tor_assert(decode_encrypted_handlers[version]); + + /* Run the version specific plaintext decoder. */ + ret = decode_encrypted_handlers[version](desc, desc_encrypted); + if (ret < 0) { + goto err; + } + + err: + return ret; +} + +/* Table of plaintext decode function version specific. The function are + * indexed by the version number so v3 callback is at index 3 in the array. */ +static int + (*decode_plaintext_handlers[])( + smartlist_t *tokens, + hs_desc_plaintext_data_t *desc, + const char *encoded_desc, + size_t encoded_len) = +{ + /* v0 */ NULL, /* v1 */ NULL, /* v2 */ NULL, + desc_decode_plaintext_v3, +}; + +/* Fully decode the given descriptor plaintext and store the data in the + * plaintext data object. Returns 0 on success else a negative value. */ +int +hs_desc_decode_plaintext(const char *encoded, + hs_desc_plaintext_data_t *plaintext) +{ + int ok = 0, ret = -1; + memarea_t *area = NULL; + smartlist_t *tokens = NULL; + size_t encoded_len; + directory_token_t *tok; + + tor_assert(encoded); + tor_assert(plaintext); + + /* Check that descriptor is within size limits. */ + encoded_len = strlen(encoded); + if (encoded_len >= hs_cache_get_max_descriptor_size()) { + log_warn(LD_REND, "Service descriptor is too big (%lu bytes)", + (unsigned long) encoded_len); + goto err; + } + + area = memarea_new(); + tokens = smartlist_new(); + /* Tokenize the descriptor so we can start to parse it. */ + if (tokenize_string(area, encoded, encoded + encoded_len, tokens, + hs_desc_v3_token_table, 0) < 0) { + log_warn(LD_REND, "Service descriptor is not parseable"); + goto err; + } + + /* Get the version of the descriptor which is the first mandatory field of + * the descriptor. From there, we'll decode the right descriptor version. */ + tok = find_by_keyword(tokens, R_HS_DESCRIPTOR); + tor_assert(tok->n_args == 1); + plaintext->version = (uint32_t) tor_parse_ulong(tok->args[0], 10, 0, + UINT32_MAX, &ok, NULL); + if (!ok) { + log_warn(LD_REND, "Service descriptor has unparseable version %s", + escaped(tok->args[0])); + goto err; + } + if (!hs_desc_is_supported_version(plaintext->version)) { + log_warn(LD_REND, "Service descriptor has unsupported version %" PRIu32, + plaintext->version); + goto err; + } + /* Extra precaution. Having no handler for the supported version should + * never happened else we forgot to add it but we bumped the version. */ + tor_assert(ARRAY_LENGTH(decode_plaintext_handlers) >= plaintext->version); + tor_assert(decode_plaintext_handlers[plaintext->version]); + + /* Run the version specific plaintext decoder. */ + ret = decode_plaintext_handlers[plaintext->version](tokens, plaintext, + encoded, encoded_len); + if (ret < 0) { + goto err; + } + /* Success. Descriptor has been populated with the data. */ + ret = 0; + + err: + if (tokens) { + SMARTLIST_FOREACH(tokens, directory_token_t *, t, token_clear(t)); + smartlist_free(tokens); + } + if (area) { + memarea_drop_all(area); + } + return ret; +} + +/* Fully decode an encoded descriptor and set a newly allocated descriptor + * object in desc_out. Subcredentials are used if not NULL else it's ignored. + * + * Return 0 on success. A negative value is returned on error and desc_out is + * set to NULL. */ +int +hs_desc_decode_descriptor(const char *encoded, + const uint8_t *subcredential, + hs_descriptor_t **desc_out) +{ + int ret = -1; + hs_descriptor_t *desc; + + tor_assert(encoded); + + desc = tor_malloc_zero(sizeof(hs_descriptor_t)); + + /* Subcredentials are optional. */ + if (BUG(!subcredential)) { + log_warn(LD_GENERAL, "Tried to decrypt without subcred. Impossible!"); + goto err; + } + + memcpy(desc->subcredential, subcredential, sizeof(desc->subcredential)); + + ret = hs_desc_decode_plaintext(encoded, &desc->plaintext_data); + if (ret < 0) { + goto err; + } + + ret = hs_desc_decode_encrypted(desc, &desc->encrypted_data); + if (ret < 0) { + goto err; + } + + if (desc_out) { + *desc_out = desc; + } else { + hs_descriptor_free(desc); + } + return ret; + + err: + hs_descriptor_free(desc); + if (desc_out) { + *desc_out = NULL; + } + + tor_assert(ret < 0); + return ret; +} + +/* Table of encode function version specific. The functions are indexed by the + * version number so v3 callback is at index 3 in the array. */ +static int + (*encode_handlers[])( + const hs_descriptor_t *desc, + const ed25519_keypair_t *signing_kp, + char **encoded_out) = +{ + /* v0 */ NULL, /* v1 */ NULL, /* v2 */ NULL, + desc_encode_v3, +}; + +/* Encode the given descriptor desc including signing with the given key pair + * signing_kp. On success, encoded_out points to a newly allocated NUL + * terminated string that contains the encoded descriptor as a string. + * + * Return 0 on success and encoded_out is a valid pointer. On error, -1 is + * returned and encoded_out is set to NULL. */ +MOCK_IMPL(int, +hs_desc_encode_descriptor,(const hs_descriptor_t *desc, + const ed25519_keypair_t *signing_kp, + char **encoded_out)) +{ + int ret = -1; + uint32_t version; + + tor_assert(desc); + tor_assert(encoded_out); + + /* Make sure we support the version of the descriptor format. */ + version = desc->plaintext_data.version; + if (!hs_desc_is_supported_version(version)) { + goto err; + } + /* Extra precaution. Having no handler for the supported version should + * never happened else we forgot to add it but we bumped the version. */ + tor_assert(ARRAY_LENGTH(encode_handlers) >= version); + tor_assert(encode_handlers[version]); + + ret = encode_handlers[version](desc, signing_kp, encoded_out); + if (ret < 0) { + goto err; + } + + /* Try to decode what we just encoded. Symmetry is nice! */ + ret = hs_desc_decode_descriptor(*encoded_out, desc->subcredential, NULL); + if (BUG(ret < 0)) { + goto err; + } + + return 0; + + err: + *encoded_out = NULL; + return ret; +} + +/* Free the descriptor plaintext data object. */ +void +hs_desc_plaintext_data_free(hs_desc_plaintext_data_t *desc) +{ + desc_plaintext_data_free_contents(desc); + tor_free(desc); +} + +/* Free the descriptor encrypted data object. */ +void +hs_desc_encrypted_data_free(hs_desc_encrypted_data_t *desc) +{ + desc_encrypted_data_free_contents(desc); + tor_free(desc); +} + +/* Free the given descriptor object. */ +void +hs_descriptor_free(hs_descriptor_t *desc) +{ + if (!desc) { + return; + } + + desc_plaintext_data_free_contents(&desc->plaintext_data); + desc_encrypted_data_free_contents(&desc->encrypted_data); + tor_free(desc); +} + +/* Return the size in bytes of the given plaintext data object. A sizeof() is + * not enough because the object contains pointers and the encrypted blob. + * This is particularly useful for our OOM subsystem that tracks the HSDir + * cache size for instance. */ +size_t +hs_desc_plaintext_obj_size(const hs_desc_plaintext_data_t *data) +{ + tor_assert(data); + return (sizeof(*data) + sizeof(*data->signing_key_cert) + + data->superencrypted_blob_size); +} + +/* Return the size in bytes of the given encrypted data object. Used by OOM + * subsystem. */ +static size_t +hs_desc_encrypted_obj_size(const hs_desc_encrypted_data_t *data) +{ + tor_assert(data); + size_t intro_size = 0; + if (data->intro_auth_types) { + intro_size += + smartlist_len(data->intro_auth_types) * sizeof(intro_auth_types); + } + if (data->intro_points) { + /* XXX could follow pointers here and get more accurate size */ + intro_size += + smartlist_len(data->intro_points) * sizeof(hs_desc_intro_point_t); + } + + return sizeof(*data) + intro_size; +} + +/* Return the size in bytes of the given descriptor object. Used by OOM + * subsystem. */ + size_t +hs_desc_obj_size(const hs_descriptor_t *data) +{ + tor_assert(data); + return (hs_desc_plaintext_obj_size(&data->plaintext_data) + + hs_desc_encrypted_obj_size(&data->encrypted_data) + + sizeof(data->subcredential)); +} + +/* Return a newly allocated descriptor intro point. */ +hs_desc_intro_point_t * +hs_desc_intro_point_new(void) +{ + hs_desc_intro_point_t *ip = tor_malloc_zero(sizeof(*ip)); + ip->link_specifiers = smartlist_new(); + return ip; +} + +/* Free a descriptor intro point object. */ +void +hs_desc_intro_point_free(hs_desc_intro_point_t *ip) +{ + if (ip == NULL) { + return; + } + if (ip->link_specifiers) { + SMARTLIST_FOREACH(ip->link_specifiers, hs_desc_link_specifier_t *, + ls, hs_desc_link_specifier_free(ls)); + smartlist_free(ip->link_specifiers); + } + tor_cert_free(ip->auth_key_cert); + tor_cert_free(ip->enc_key_cert); + crypto_pk_free(ip->legacy.key); + tor_free(ip->legacy.cert.encoded); + tor_free(ip); +} + +/* Free the given descriptor link specifier. */ +void +hs_desc_link_specifier_free(hs_desc_link_specifier_t *ls) +{ + if (ls == NULL) { + return; + } + tor_free(ls); +} + +/* Return a newly allocated descriptor link specifier using the given extend + * info and requested type. Return NULL on error. */ +hs_desc_link_specifier_t * +hs_desc_link_specifier_new(const extend_info_t *info, uint8_t type) +{ + hs_desc_link_specifier_t *ls = NULL; + + tor_assert(info); + + ls = tor_malloc_zero(sizeof(*ls)); + ls->type = type; + switch (ls->type) { + case LS_IPV4: + if (info->addr.family != AF_INET) { + goto err; + } + tor_addr_copy(&ls->u.ap.addr, &info->addr); + ls->u.ap.port = info->port; + break; + case LS_IPV6: + if (info->addr.family != AF_INET6) { + goto err; + } + tor_addr_copy(&ls->u.ap.addr, &info->addr); + ls->u.ap.port = info->port; + break; + case LS_LEGACY_ID: + /* Bug out if the identity digest is not set */ + if (BUG(tor_mem_is_zero(info->identity_digest, + sizeof(info->identity_digest)))) { + goto err; + } + memcpy(ls->u.legacy_id, info->identity_digest, sizeof(ls->u.legacy_id)); + break; + case LS_ED25519_ID: + /* ed25519 keys are optional for intro points */ + if (ed25519_public_key_is_zero(&info->ed_identity)) { + goto err; + } + memcpy(ls->u.ed25519_id, info->ed_identity.pubkey, + sizeof(ls->u.ed25519_id)); + break; + default: + /* Unknown type is code flow error. */ + tor_assert(0); + } + + return ls; + err: + tor_free(ls); + return NULL; +} + +/* From the given descriptor, remove and free every introduction point. */ +void +hs_descriptor_clear_intro_points(hs_descriptor_t *desc) +{ + smartlist_t *ips; + + tor_assert(desc); + + ips = desc->encrypted_data.intro_points; + if (ips) { + SMARTLIST_FOREACH(ips, hs_desc_intro_point_t *, + ip, hs_desc_intro_point_free(ip)); + smartlist_clear(ips); + } +} + +/* From a descriptor link specifier object spec, returned a newly allocated + * link specifier object that is the encoded representation of spec. Return + * NULL on error. */ +link_specifier_t * +hs_desc_lspec_to_trunnel(const hs_desc_link_specifier_t *spec) +{ + tor_assert(spec); + + link_specifier_t *ls = link_specifier_new(); + link_specifier_set_ls_type(ls, spec->type); + + switch (spec->type) { + case LS_IPV4: + link_specifier_set_un_ipv4_addr(ls, + tor_addr_to_ipv4h(&spec->u.ap.addr)); + link_specifier_set_un_ipv4_port(ls, spec->u.ap.port); + /* Four bytes IPv4 and two bytes port. */ + link_specifier_set_ls_len(ls, sizeof(spec->u.ap.addr.addr.in_addr) + + sizeof(spec->u.ap.port)); + break; + case LS_IPV6: + { + size_t addr_len = link_specifier_getlen_un_ipv6_addr(ls); + const uint8_t *in6_addr = tor_addr_to_in6_addr8(&spec->u.ap.addr); + uint8_t *ipv6_array = link_specifier_getarray_un_ipv6_addr(ls); + memcpy(ipv6_array, in6_addr, addr_len); + link_specifier_set_un_ipv6_port(ls, spec->u.ap.port); + /* Sixteen bytes IPv6 and two bytes port. */ + link_specifier_set_ls_len(ls, addr_len + sizeof(spec->u.ap.port)); + break; + } + case LS_LEGACY_ID: + { + size_t legacy_id_len = link_specifier_getlen_un_legacy_id(ls); + uint8_t *legacy_id_array = link_specifier_getarray_un_legacy_id(ls); + memcpy(legacy_id_array, spec->u.legacy_id, legacy_id_len); + link_specifier_set_ls_len(ls, legacy_id_len); + break; + } + case LS_ED25519_ID: + { + size_t ed25519_id_len = link_specifier_getlen_un_ed25519_id(ls); + uint8_t *ed25519_id_array = link_specifier_getarray_un_ed25519_id(ls); + memcpy(ed25519_id_array, spec->u.ed25519_id, ed25519_id_len); + link_specifier_set_ls_len(ls, ed25519_id_len); + break; + } + default: + tor_assert_nonfatal_unreached(); + link_specifier_free(ls); + ls = NULL; + } + + return ls; +} + |