text: /* Copyright (c) 2016-2020, 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 "core/or/or.h"
  #include "app/config/config.h"
  #include "trunnel/ed25519_cert.h" /* Trunnel interface. */
  #include "feature/hs/hs_descriptor.h"
  #include "core/or/circuitbuild.h"
  #include "lib/crypt_ops/crypto_rand.h"
  #include "lib/crypt_ops/crypto_util.h"
  #include "feature/dirparse/parsecommon.h"
  #include "feature/rend/rendcache.h"
  #include "feature/hs/hs_cache.h"
  #include "feature/hs/hs_config.h"
  #include "feature/nodelist/torcert.h" /* tor_cert_encode_ed22519() */
  #include "lib/memarea/memarea.h"
  #include "lib/crypt_ops/crypto_format.h"
  
  #include "core/or/extend_info_st.h"
  
  /* 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
  };
  
  /** 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 secret data and a given decriptor object, build the secret
   * input needed for the KDF.
   *
   * secret_input = SECRET_DATA | subcredential | INT_8(revision_counter)
   *
   * Then, set the newly allocated buffer in secret_input_out and return the
   * length of the buffer. */
  static size_t
  build_secret_input(const hs_descriptor_t *desc,
                     const uint8_t *secret_data,
                     size_t secret_data_len,
                     uint8_t **secret_input_out)
  {
    size_t offset = 0;
    size_t secret_input_len = secret_data_len + DIGEST256_LEN + sizeof(uint64_t);
    uint8_t *secret_input = NULL;
  
    tor_assert(desc);
    tor_assert(secret_data);
    tor_assert(secret_input_out);
  
    secret_input = tor_malloc_zero(secret_input_len);
  
    /* Copy the secret data. */
    memcpy(secret_input, secret_data, secret_data_len);
    offset += secret_data_len;
    /* Copy subcredential. */
    memcpy(secret_input + offset, desc->subcredential, DIGEST256_LEN);
    offset += DIGEST256_LEN;
    /* Copy revision counter value. */
    set_uint64(secret_input + offset,
               tor_htonll(desc->plaintext_data.revision_counter));
    offset += sizeof(uint64_t);
    tor_assert(secret_input_len == offset);
  
    *secret_input_out = secret_input;
  
    return secret_input_len;
  }
  
  /** 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 *secret_data,
                size_t secret_data_len,
                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 = NULL;
    size_t secret_input_len;
    crypto_xof_t *xof;
  
    tor_assert(desc);
    tor_assert(secret_data);
    tor_assert(salt);
    tor_assert(key_out);
  
    /* Build the secret input for the KDF computation. */
    secret_input_len = build_secret_input(desc, secret_data,
                                          secret_data_len, &secret_input);
  
    xof = crypto_xof_new();
    /* Feed our KDF. [SHAKE it like a polaroid picture --Yawning]. */
    crypto_xof_add_bytes(xof, secret_input, secret_input_len);
    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, secret_input_len);
  
    tor_free(secret_input);
  }
  
  /** Using the given descriptor, secret data, 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 *secret_data,
                          size_t secret_data_len,
                          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(secret_data);
    tor_assert(salt);
    tor_assert(key_out);
    tor_assert(iv_out);
    tor_assert(mac_out);
  
    build_kdf_key(desc, secret_data, secret_data_len,
                  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 link_specifier_t *,
                            spec) {
      link_specifier_t *ls = link_specifier_dup(spec);
      tor_assert(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. */
    curve25519_public_to_base64(key_b64, &ip->enc_key);
    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. Can not fail. */
  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. */
    curve25519_public_to_base64(key_b64, &ip->onion_key);
    tor_asprintf(&encoded, "%s ntor %s", str_ip_onion_key, key_b64);
  
    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> and
   * <b>secret_data</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 uint8_t *secret_data,
                          size_t secret_data_len,
                          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(secret_data);
    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, secret_data, secret_data_len,
                            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 client-auth entry. It's the
   * responsibility of the caller to free the returned string. This function
   * will never fail. */
  static char *
  get_auth_client_str(const hs_desc_authorized_client_t *client)
  {
    int ret;
    char *auth_client_str = NULL;
    /* We are gonna fill these arrays with base64 data. They are all double
     * the size of their binary representation to fit the base64 overhead. */
    char client_id_b64[HS_DESC_CLIENT_ID_LEN * 2];
    char iv_b64[CIPHER_IV_LEN * 2];
    char encrypted_cookie_b64[HS_DESC_ENCRYPED_COOKIE_LEN * 2];
  
  #define ASSERT_AND_BASE64(field) STMT_BEGIN                        \
    tor_assert(!fast_mem_is_zero((char *) client->field,              \
                                sizeof(client->field)));             \
    ret = base64_encode_nopad(field##_b64, sizeof(field##_b64),      \
                              client->field, sizeof(client->field)); \
    tor_assert(ret > 0);                                             \
    STMT_END
  
    ASSERT_AND_BASE64(client_id);
    ASSERT_AND_BASE64(iv);
    ASSERT_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 ASSERT_AND_BASE64
  
    return auth_client_str;
  }
  
  /** 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_all_auth_client_lines(const hs_descriptor_t *desc)
  {
    smartlist_t *auth_client_lines = smartlist_new();
    char *auth_client_lines_str = NULL;
  
    tor_assert(desc);
    tor_assert(desc->superencrypted_data.clients);
    tor_assert(smartlist_len(desc->superencrypted_data.clients) != 0);
    tor_assert(smartlist_len(desc->superencrypted_data.clients)
                                   % HS_DESC_AUTH_CLIENT_MULTIPLE == 0);
  
    /* Make a line for each client */
    SMARTLIST_FOREACH_BEGIN(desc->superencrypted_data.clients,
                            const hs_desc_authorized_client_t *, client) {
      char *auth_client_str = NULL;
  
      auth_client_str = get_auth_client_str(client);
  
      smartlist_add(auth_client_lines, auth_client_str);
    } SMARTLIST_FOREACH_END(client);
  
    /* 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 occurred. 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. It's the responsibility of the caller to free the returned
   * string. Can not fail. */
  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();
  
    /* Specify auth type */
    smartlist_add_asprintf(lines, "%s %s\n", str_desc_auth_type, "x25519");
  
    {  /* Print ephemeral x25519 key */
      char ephemeral_key_base64[CURVE25519_BASE64_PADDED_LEN + 1];
      const curve25519_public_key_t *ephemeral_pubkey;
  
      ephemeral_pubkey = &desc->superencrypted_data.auth_ephemeral_pubkey;
      tor_assert(!fast_mem_is_zero((char *) ephemeral_pubkey->public_key,
                                  CURVE25519_PUBKEY_LEN));
  
      curve25519_public_to_base64(ephemeral_key_base64, ephemeral_pubkey);
      smartlist_add_asprintf(lines, "%s %s\n",
                             str_desc_auth_key, ephemeral_key_base64);
  
      memwipe(ephemeral_key_base64, 0, sizeof(ephemeral_key_base64));
    }
  
    {  /* Create auth-client lines. */
      char *auth_client_lines = get_all_auth_client_lines(desc);
      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);
  
    /* We need to memwipe all lines because it contains the ephemeral key */
    SMARTLIST_FOREACH(lines, char *, a, memwipe(a, 0, strlen(a)));
    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>secret_data</b> is also proved 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 uint8_t *secret_data,
                               size_t secret_data_len,
                               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, secret_data, secret_data_len,
                                      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 the secret data which is used to encrypt/decrypt the descriptor.
   *
   * SECRET_DATA = blinded-public-key
   * SECRET_DATA = blinded-public-key | descriptor_cookie
   *
   * The descriptor_cookie is optional but if it exists, it must be at least
   * HS_DESC_DESCRIPTOR_COOKIE_LEN bytes long.
   *
   * A newly allocated secret data is put in secret_data_out. Return the
   * length of the secret data. This function cannot fail. */
  static size_t
  build_secret_data(const ed25519_public_key_t *blinded_pubkey,
                    const uint8_t *descriptor_cookie,
                    uint8_t **secret_data_out)
  {
    size_t secret_data_len;
    uint8_t *secret_data;
  
    tor_assert(blinded_pubkey);
    tor_assert(secret_data_out);
  
    if (descriptor_cookie) {
      /* If the descriptor cookie is present, we need both the blinded
       * pubkey and the descriptor cookie as a secret data. */
      secret_data_len = ED25519_PUBKEY_LEN + HS_DESC_DESCRIPTOR_COOKIE_LEN;
      secret_data = tor_malloc(secret_data_len);
  
      memcpy(secret_data,
             blinded_pubkey->pubkey,
             ED25519_PUBKEY_LEN);
      memcpy(secret_data + ED25519_PUBKEY_LEN,
             descriptor_cookie,
             HS_DESC_DESCRIPTOR_COOKIE_LEN);
    } else {
      /* If the descriptor cookie is not present, we need only the blinded
       * pubkey as a secret data. */
      secret_data_len = ED25519_PUBKEY_LEN;
      secret_data = tor_malloc(secret_data_len);
      memcpy(secret_data,
             blinded_pubkey->pubkey,
             ED25519_PUBKEY_LEN);
    }
  
    *secret_data_out = secret_data;
    return secret_data_len;
  }
  
  /** 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,
                             const uint8_t *descriptor_cookie,
                             char **encrypted_blob_out)
  {
    int ret = -1;
    uint8_t *secret_data = NULL;
    size_t secret_data_len = 0;
    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;
    }
  
    secret_data_len = build_secret_data(&desc->plaintext_data.blinded_pubkey,
                                        descriptor_cookie,
                                        &secret_data);
  
    /* Encrypt and b64 the inner layer */
    layer2_b64_ciphertext =
      encrypt_desc_data_and_base64(desc, secret_data, secret_data_len,
                                   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,
                                   desc->plaintext_data.blinded_pubkey.pubkey,
                                   ED25519_PUBKEY_LEN,
                                   layer1_str, 1);
    if (!layer1_b64_ciphertext) {
      goto err;
    }
  
    /* Success! */
    ret = 0;
  
   err:
    memwipe(secret_data, 0, secret_data_len);
    tor_free(secret_data);
    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,
                 const uint8_t *descriptor_cookie,
                 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, descriptor_cookie,
                                     &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;
      }
      ed25519_signature_to_base64(ed_sig_b64, &sig);
      /* 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 the token tok for an auth client, decode it as
   * hs_desc_authorized_client_t. tok->args MUST contain at least 3 elements
   * Return 0 on success else -1 on failure. */
  static int
  decode_auth_client(const directory_token_t *tok,
                     hs_desc_authorized_client_t *client)
  {
    int ret = -1;
  
    tor_assert(tok);
    tor_assert(tok->n_args >= 3);
    tor_assert(client);
  
    if (base64_decode((char *) client->client_id, sizeof(client->client_id),
                      tok->args[0], strlen(tok->args[0])) !=
        sizeof(client->client_id)) {
      goto done;
    }
    if (base64_decode((char *) client->iv, sizeof(client->iv),
                      tok->args[1], strlen(tok->args[1])) !=
        sizeof(client->iv)) {
      goto done;
    }
    if (base64_decode((char *) client->encrypted_cookie,
                      sizeof(client->encrypted_cookie),
                      tok->args[2], strlen(tok->args[2])) !=
        sizeof(client->encrypted_cookie)) {
      goto done;
    }
  
    /* Success. */
    ret = 0;
   done:
    return ret;
  }
  
  /** 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++) {
      link_specifier_t *ls = link_specifier_list_get_spec(specs, i);
      if (BUG(!ls)) {
        goto err;
      }
      link_specifier_t *ls_dup = link_specifier_dup(ls);
      if (BUG(!ls_dup)) {
        goto err;
      }
      smartlist_add(results, ls_dup);
    }
  
    goto done;
   err:
    if (results) {
      SMARTLIST_FOREACH(results, link_specifier_t *, s,
                        link_specifier_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) {
      if (cert->cert_expired) {
        char expiration_str[ISO_TIME_LEN+1];
        format_iso_time(expiration_str, cert->valid_until);
        log_fn(LOG_PROTOCOL_WARN, LD_REND, "Invalid signature for %s: %s (%s)",
               log_obj_type, tor_cert_describe_signature_status(cert),
               expiration_str);
      } else {
        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;
  }
  
  /** Build the KEYS component for the authorized client computation. The format
   * of the construction is:
   *
   *    SECRET_SEED = x25519(sk, pk)
   *    KEYS = KDF(subcredential | SECRET_SEED, 40)
   *
   * Set the <b>keys_out</b> argument to point to the buffer containing the KEYS,
   * and return the buffer's length. The caller should wipe and free its content
   * once done with it. This function can't fail. */
  static size_t
  build_descriptor_cookie_keys(const uint8_t *subcredential,
                               size_t subcredential_len,
                               const curve25519_secret_key_t *sk,
                               const curve25519_public_key_t *pk,
                               uint8_t **keys_out)
  {
    uint8_t secret_seed[CURVE25519_OUTPUT_LEN];
    uint8_t *keystream;
    size_t keystream_len = HS_DESC_CLIENT_ID_LEN + HS_DESC_COOKIE_KEY_LEN;
    crypto_xof_t *xof;
  
    tor_assert(subcredential);
    tor_assert(sk);
    tor_assert(pk);
    tor_assert(keys_out);
  
    keystream = tor_malloc_zero(keystream_len);
  
    /* Calculate x25519(sk, pk) to get the secret seed. */
    curve25519_handshake(secret_seed, sk, pk);
  
    /* Calculate KEYS = KDF(subcredential | SECRET_SEED, 40) */
    xof = crypto_xof_new();
    crypto_xof_add_bytes(xof, subcredential, subcredential_len);
    crypto_xof_add_bytes(xof, secret_seed, sizeof(secret_seed));
    crypto_xof_squeeze_bytes(xof, keystream, keystream_len);
    crypto_xof_free(xof);
  
    memwipe(secret_seed, 0, sizeof(secret_seed));
  
    *keys_out = keystream;
    return keystream_len;
  }
  
  /** Decrypt the descriptor cookie given the descriptor, the auth client,
   * and the client secret key. On sucess, return 0 and a newly allocated
   * descriptor cookie descriptor_cookie_out. On error or if the client id
   * is invalid, return -1 and descriptor_cookie_out is set to
   * NULL. */
  static int
  decrypt_descriptor_cookie(const hs_descriptor_t *desc,
                            const hs_desc_authorized_client_t *client,
                            const curve25519_secret_key_t *client_auth_sk,
                            uint8_t **descriptor_cookie_out)
  {
    int ret = -1;
    uint8_t *keystream = NULL;
    size_t keystream_length = 0;
    uint8_t *descriptor_cookie = NULL;
    const uint8_t *cookie_key = NULL;
    crypto_cipher_t *cipher = NULL;
  
    tor_assert(desc);
    tor_assert(client);
    tor_assert(client_auth_sk);
    tor_assert(!fast_mem_is_zero(
          (char *) &desc->superencrypted_data.auth_ephemeral_pubkey,
          sizeof(desc->superencrypted_data.auth_ephemeral_pubkey)));
    tor_assert(!fast_mem_is_zero((char *) desc->subcredential, DIGEST256_LEN));
  
    /* Catch potential code-flow cases of an unitialized private key sneaking
     * into this function. */
    if (BUG(fast_mem_is_zero((char *)client_auth_sk, sizeof(*client_auth_sk)))) {
      goto done;
    }
  
    /* Get the KEYS component to derive the CLIENT-ID and COOKIE-KEY. */
    keystream_length =
      build_descriptor_cookie_keys(desc->subcredential, DIGEST256_LEN,
                               client_auth_sk,
                               &desc->superencrypted_data.auth_ephemeral_pubkey,
                               &keystream);
    tor_assert(keystream_length > 0);
  
    /* If the client id of auth client is not the same as the calculcated
     * client id, it means that this auth client is invaild according to the
     * client secret key client_auth_sk. */
    if (tor_memneq(client->client_id, keystream, HS_DESC_CLIENT_ID_LEN)) {
      goto done;
    }
    cookie_key = keystream + HS_DESC_CLIENT_ID_LEN;
  
    /* This creates a cipher for AES. It can't fail. */
    cipher = crypto_cipher_new_with_iv_and_bits(cookie_key, client->iv,
                                                HS_DESC_COOKIE_KEY_BIT_SIZE);
    descriptor_cookie = tor_malloc_zero(HS_DESC_DESCRIPTOR_COOKIE_LEN);
    /* This can't fail. */
    crypto_cipher_decrypt(cipher, (char *) descriptor_cookie,
                          (const char *) client->encrypted_cookie,
                          sizeof(client->encrypted_cookie));
  
    /* Success. */
    ret = 0;
   done:
    *descriptor_cookie_out = descriptor_cookie;
    if (cipher) {
      crypto_cipher_free(cipher);
    }
    memwipe(keystream, 0, keystream_length);
    tor_free(keystream);
    return ret;
  }
  
  /** Decrypt an encrypted descriptor layer at <b>encrypted_blob</b> of size
   *  <b>encrypted_blob_size</b>. The descriptor cookie is optional. Use
   *  the descriptor object <b>desc</b> and <b>descriptor_cookie</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 *descriptor_cookie,
                      bool 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 *secret_data = NULL;
    size_t secret_data_len = 0;
    uint8_t mac_key[DIGEST256_LEN], our_mac[DIGEST256_LEN];
    const uint8_t *salt, *encrypted, *desc_mac;
    size_t encrypted_len, result_len = 0;
    const uint8_t *encrypted_blob = (is_superencrypted_layer)
      ? desc->plaintext_data.superencrypted_blob
      : desc->superencrypted_data.encrypted_blob;
    size_t encrypted_blob_size = (is_superencrypted_layer)
      ? desc->plaintext_data.superencrypted_blob_size
      : desc->superencrypted_data.encrypted_blob_size;
  
    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;
  
    /* Build secret data to be used in the decryption. */
    secret_data_len = build_secret_data(&desc->plaintext_data.blinded_pubkey,
                                        descriptor_cookie,
                                        &secret_data);
  
    /* 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, secret_data, secret_data_len,
                            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_info(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_data, 0, secret_data_len);
    memwipe(secret_key, 0, sizeof(secret_key));
    memwipe(secret_iv, 0, sizeof(secret_iv));
    tor_free(secret_data);
    return result_len;
  }
  
  /** Decrypt the superencrypted 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 superencrypted 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_superencrypted(const hs_descriptor_t *desc, char **decrypted_out)
  {
    size_t superencrypted_len = 0;
    char *superencrypted_plaintext = NULL;
  
    tor_assert(desc);
    tor_assert(decrypted_out);
  
    superencrypted_len = decrypt_desc_layer(desc,
                                            NULL,
                                            true, &superencrypted_plaintext);
  
    if (!superencrypted_len) {
      log_warn(LD_REND, "Decrypting superencrypted desc failed.");
      goto done;
    }
    tor_assert(superencrypted_plaintext);
  
   done:
    /* In case of error, superencrypted_plaintext is already NULL, so the
     * following line makes sense. */
    *decrypted_out = superencrypted_plaintext;
    /* This makes sense too, because, in case of error, this is zero. */
    return superencrypted_len;
  }
  
  /** Decrypt 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 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_encrypted(const hs_descriptor_t *desc,
                         const curve25519_secret_key_t *client_auth_sk,
                         char **decrypted_out)
  {
    size_t encrypted_len = 0;
    char *encrypted_plaintext = NULL;
    uint8_t *descriptor_cookie = NULL;
  
    tor_assert(desc);
    tor_assert(desc->superencrypted_data.clients);
    tor_assert(decrypted_out);
  
    /* If the client secret key is provided, try to find a valid descriptor
     * cookie. Otherwise, leave it NULL. */
    if (client_auth_sk) {
      SMARTLIST_FOREACH_BEGIN(desc->superencrypted_data.clients,
                              hs_desc_authorized_client_t *, client) {
        /* If we can decrypt the descriptor cookie successfully, we will use that
         * descriptor cookie and break from the loop. */
        if (!decrypt_descriptor_cookie(desc, client, client_auth_sk,
                                       &descriptor_cookie)) {
          break;
        }
      } SMARTLIST_FOREACH_END(client);
    }
  
    encrypted_len = decrypt_desc_layer(desc,
                                       descriptor_cookie,
                                       false, &encrypted_plaintext);
  
    if (!encrypted_len) {
      goto err;
    }
    tor_assert(encrypted_plaintext);
  
   err:
    /* In case of error, encrypted_plaintext is already NULL, so the
     * following line makes sense. */
    *decrypted_out = encrypted_plaintext;
    if (descriptor_cookie) {
      memwipe(descriptor_cookie, 0, HS_DESC_DESCRIPTOR_COOKIE_LEN);
    }
    tor_free(descriptor_cookie);
    /* This makes sense too, because, in case of error, this is zero. */
    return encrypted_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 accommodate 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 hs_desc_decode_status_t
  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 superencrypted 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, "Desc superencrypted data section is invalid");
      goto err;
    }
    /* Make sure the length of the superencrypted blob is valid. */
    if (!encrypted_data_length_is_valid(tok->object_size)) {
      goto err;
    }
  
    /* Copy the superencrypted 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 HS_DESC_DECODE_OK;
   err:
    return HS_DESC_DECODE_PLAINTEXT_ERROR;
  }
  
  /** Decode the version 3 superencrypted section of the given descriptor desc.
   * The desc_superencrypted_out will be populated with the decoded data. */
  static hs_desc_decode_status_t
  desc_decode_superencrypted_v3(const hs_descriptor_t *desc,
                                hs_desc_superencrypted_data_t *
                                desc_superencrypted_out)
  {
    int ret = HS_DESC_DECODE_SUPERENC_ERROR;
    char *message = NULL;
    size_t message_len;
    memarea_t *area = NULL;
    directory_token_t *tok;
    smartlist_t *tokens = NULL;
    /* Rename the parameter because it is too long. */
    hs_desc_superencrypted_data_t *superencrypted = desc_superencrypted_out;
  
    tor_assert(desc);
    tor_assert(desc_superencrypted_out);
  
    /* Decrypt the superencrypted data that is located in the plaintext section
     * in the descriptor as a blob of bytes. */
    message_len = desc_decrypt_superencrypted(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_superencrypted_v3_token_table, 0) < 0) {
      log_warn(LD_REND, "Superencrypted service descriptor is not parseable.");
      goto err;
    }
  
    /* Verify desc auth type */
    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");
      goto err;
    }
  
    /* Extract desc auth ephemeral key */
    tok = find_by_keyword(tokens, R3_DESC_AUTH_KEY);
    tor_assert(tok->n_args >= 1);
    if (curve25519_public_from_base64(&superencrypted->auth_ephemeral_pubkey,
                                      tok->args[0]) < 0) {
      log_warn(LD_DIR, "Bogus desc auth ephemeral key in HS desc");
      goto err;
    }
  
    /* Extract desc auth client items */
    if (!superencrypted->clients) {
      superencrypted->clients = smartlist_new();
    }
    SMARTLIST_FOREACH_BEGIN(tokens, const directory_token_t *, token) {
      if (token->tp == R3_DESC_AUTH_CLIENT) {
        tor_assert(token->n_args >= 3);
  
        hs_desc_authorized_client_t *client =
          tor_malloc_zero(sizeof(hs_desc_authorized_client_t));
  
        if (decode_auth_client(token, client) < 0) {
          log_warn(LD_REND, "Descriptor client authorization section can't "
                            "be decoded.");
          tor_free(client);
          goto err;
        }
        smartlist_add(superencrypted->clients, client);
      }
    } SMARTLIST_FOREACH_END(token);
  
    /* Extract the encrypted data section. */
    tok = find_by_keyword(tokens, R3_ENCRYPTED);
    tor_assert(tok->object_body);
    if (strcmp(tok->object_type, "MESSAGE") != 0) {
      log_warn(LD_REND, "Desc 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. */
    tor_assert(tok->object_size <= INT_MAX);
    superencrypted->encrypted_blob = tor_memdup(tok->object_body,
                                                tok->object_size);
    superencrypted->encrypted_blob_size = tok->object_size;
  
    ret = HS_DESC_DECODE_OK;
    goto done;
  
   err:
    tor_assert(ret < HS_DESC_DECODE_OK);
    hs_desc_superencrypted_data_free_contents(desc_superencrypted_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 ret;
  }
  
  /** Decode the version 3 encrypted section of the given descriptor desc. The
   * desc_encrypted_out will be populated with the decoded data. */
  static hs_desc_decode_status_t
  desc_decode_encrypted_v3(const hs_descriptor_t *desc,
                           const curve25519_secret_key_t *client_auth_sk,
                           hs_desc_encrypted_data_t *desc_encrypted_out)
  {
    int ret = HS_DESC_DECODE_ENCRYPTED_ERROR;
    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 encrypted data that is located in the superencrypted section
     * in the descriptor as a blob of bytes. */
    message_len = desc_decrypt_encrypted(desc, client_auth_sk, &message);
    if (!message_len) {
      /* Two possible situation here. Either we have a client authorization
       * configured that didn't work or we do not have any configured for this
       * onion address so likely the descriptor is for authorized client only,
       * we are not. */
      if (client_auth_sk) {
        /* At warning level so the client can notice that its client
         * authorization is failing. */
        log_warn(LD_REND, "Client authorization for requested onion address "
                          "is invalid. Can't decrypt the descriptor.");
        ret = HS_DESC_DECODE_BAD_CLIENT_AUTH;
      } else {
        /* Inform at notice level that the onion address requested can't be
         * reached without client authorization most likely. */
        log_notice(LD_REND, "Fail to decrypt descriptor for requested onion "
                          "address. It is likely requiring client "
                          "authorization.");
        ret = HS_DESC_DECODE_NEED_CLIENT_AUTH;
      }
      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. */
  
    ret = HS_DESC_DECODE_OK;
    goto done;
  
   err:
    tor_assert(ret < HS_DESC_DECODE_OK);
    hs_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 ret;
  }
  
  /** 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 hs_desc_decode_status_t
    (*decode_encrypted_handlers[])(
        const hs_descriptor_t *desc,
        const curve25519_secret_key_t *client_auth_sk,
        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. */
  hs_desc_decode_status_t
  hs_desc_decode_encrypted(const hs_descriptor_t *desc,
                           const curve25519_secret_key_t *client_auth_sk,
                           hs_desc_encrypted_data_t *desc_encrypted)
  {
    int ret = HS_DESC_DECODE_ENCRYPTED_ERROR;
    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 superencrypted parsing should never succeed in the first place
     * without an encrypted section. */
    tor_assert(desc->superencrypted_data.encrypted_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))) {
      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, client_auth_sk,
                                             desc_encrypted);
    if (ret < 0) {
      goto err;
    }
  
   err:
    return ret;
  }
  
  /** Table of superencrypted decode function version specific. The function are
   * indexed by the version number so v3 callback is at index 3 in the array. */
  static hs_desc_decode_status_t
    (*decode_superencrypted_handlers[])(
        const hs_descriptor_t *desc,
        hs_desc_superencrypted_data_t *desc_superencrypted) =
  {
    /* v0 */ NULL, /* v1 */ NULL, /* v2 */ NULL,
    desc_decode_superencrypted_v3,
  };
  
  /** Decode the superencrypted data section of the given descriptor and store
   * the data in the given superencrypted data object. */
  hs_desc_decode_status_t
  hs_desc_decode_superencrypted(const hs_descriptor_t *desc,
                                hs_desc_superencrypted_data_t *
                                desc_superencrypted)
  {
    int ret = HS_DESC_DECODE_SUPERENC_ERROR;
    uint32_t version;
  
    tor_assert(desc);
    /* Ease our life a bit. */
    version = desc->plaintext_data.version;
    tor_assert(desc_superencrypted);
    /* Calling this function without an superencrypted blob to parse is
     * a code flow error. The plaintext parsing should never succeed in
     * the first place without an superencrypted 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))) {
      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_superencrypted_handlers) >= version);
    tor_assert(decode_superencrypted_handlers[version]);
  
    /* Run the version specific plaintext decoder. */
    ret = decode_superencrypted_handlers[version](desc, desc_superencrypted);
    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 hs_desc_decode_status_t
    (*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. */
  hs_desc_decode_status_t
  hs_desc_decode_plaintext(const char *encoded,
                           hs_desc_plaintext_data_t *plaintext)
  {
    int ok = 0, ret = HS_DESC_DECODE_PLAINTEXT_ERROR;
    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 != HS_DESC_DECODE_OK) {
      goto err;
    }
    /* Success. Descriptor has been populated with the data. */
    ret = HS_DESC_DECODE_OK;
  
   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.  Client secret key is used to decrypt the "encrypted"
   * section 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. */
  hs_desc_decode_status_t
  hs_desc_decode_descriptor(const char *encoded,
                            const uint8_t *subcredential,
                            const curve25519_secret_key_t *client_auth_sk,
                            hs_descriptor_t **desc_out)
  {
    hs_desc_decode_status_t ret = HS_DESC_DECODE_GENERIC_ERROR;
    hs_descriptor_t *desc;
  
    tor_assert(encoded);
  
    desc = tor_malloc_zero(sizeof(hs_descriptor_t));
  
    /* Subcredentials are not optional. */
    if (BUG(!subcredential ||
            fast_mem_is_zero((char*)subcredential, DIGEST256_LEN))) {
      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 != HS_DESC_DECODE_OK) {
      goto err;
    }
  
    ret = hs_desc_decode_superencrypted(desc, &desc->superencrypted_data);
    if (ret != HS_DESC_DECODE_OK) {
      goto err;
    }
  
    ret = hs_desc_decode_encrypted(desc, client_auth_sk, &desc->encrypted_data);
    if (ret != HS_DESC_DECODE_OK) {
      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,
        const uint8_t *descriptor_cookie,
        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 and encrypting with the given descriptor cookie.
   *
   * If the client authorization is enabled, descriptor_cookie must be the same
   * as the one used to build hs_desc_authorized_client_t in the descriptor.
   * Otherwise, it must be NULL.  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,
                             const uint8_t *descriptor_cookie,
                             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,
                                   descriptor_cookie, encoded_out);
    if (ret < 0) {
      goto err;
    }
  
    /* Try to decode what we just encoded. Symmetry is nice!, but it is
     * symmetric only if the client auth is disabled. That is, the descriptor
     * cookie will be NULL. */
    if (!descriptor_cookie) {
      ret = hs_desc_decode_descriptor(*encoded_out, desc->subcredential,
                                      NULL, NULL);
      if (BUG(ret != HS_DESC_DECODE_OK)) {
        ret = -1;
        goto err;
      }
    }
  
    return 0;
  
   err:
    *encoded_out = NULL;
    return ret;
  }
  
  /** Free the content of the plaintext section of a descriptor. */
  void
  hs_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 superencrypted section of a descriptor. */
  void
  hs_desc_superencrypted_data_free_contents(hs_desc_superencrypted_data_t *desc)
  {
    if (!desc) {
      return;
    }
  
    if (desc->encrypted_blob) {
      tor_free(desc->encrypted_blob);
    }
    if (desc->clients) {
      SMARTLIST_FOREACH(desc->clients, hs_desc_authorized_client_t *, client,
                        hs_desc_authorized_client_free(client));
      smartlist_free(desc->clients);
    }
  
    memwipe(desc, 0, sizeof(*desc));
  }
  
  /** Free the content of the encrypted section of a descriptor. */
  void
  hs_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));
  }
  
  /** Free the descriptor plaintext data object. */
  void
  hs_desc_plaintext_data_free_(hs_desc_plaintext_data_t *desc)
  {
    hs_desc_plaintext_data_free_contents(desc);
    tor_free(desc);
  }
  
  /** Free the descriptor plaintext data object. */
  void
  hs_desc_superencrypted_data_free_(hs_desc_superencrypted_data_t *desc)
  {
    hs_desc_superencrypted_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)
  {
    hs_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;
    }
  
    hs_desc_plaintext_data_free_contents(&desc->plaintext_data);
    hs_desc_superencrypted_data_free_contents(&desc->superencrypted_data);
    hs_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)
  {
    if (data == NULL) {
      return 0;
    }
    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, link_specifier_t *,
                        ls, 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);
  }
  
  /** Allocate and build a new fake client info for the descriptor. Return a
   * newly allocated object. This can't fail. */
  hs_desc_authorized_client_t *
  hs_desc_build_fake_authorized_client(void)
  {
    hs_desc_authorized_client_t *client_auth =
      tor_malloc_zero(sizeof(*client_auth));
  
    crypto_rand((char *) client_auth->client_id,
                sizeof(client_auth->client_id));
    crypto_rand((char *) client_auth->iv,
                sizeof(client_auth->iv));
    crypto_rand((char *) client_auth->encrypted_cookie,
                sizeof(client_auth->encrypted_cookie));
  
    return client_auth;
  }
  
  /** Using the service's subcredential, client public key, auth ephemeral secret
   * key, and descriptor cookie, build the auth client so we can then encode the
   * descriptor for publication. client_out must be already allocated. */
  void
  hs_desc_build_authorized_client(const uint8_t *subcredential,
                                  const curve25519_public_key_t *client_auth_pk,
                                  const curve25519_secret_key_t *
                                  auth_ephemeral_sk,
                                  const uint8_t *descriptor_cookie,
                                  hs_desc_authorized_client_t *client_out)
  {
    uint8_t *keystream = NULL;
    size_t keystream_length = 0;
    const uint8_t *cookie_key;
    crypto_cipher_t *cipher;
  
    tor_assert(client_auth_pk);
    tor_assert(auth_ephemeral_sk);
    tor_assert(descriptor_cookie);
    tor_assert(client_out);
    tor_assert(subcredential);
    tor_assert(!fast_mem_is_zero((char *) auth_ephemeral_sk,
                                sizeof(*auth_ephemeral_sk)));
    tor_assert(!fast_mem_is_zero((char *) client_auth_pk,
                                sizeof(*client_auth_pk)));
    tor_assert(!fast_mem_is_zero((char *) descriptor_cookie,
                                HS_DESC_DESCRIPTOR_COOKIE_LEN));
    tor_assert(!fast_mem_is_zero((char *) subcredential,
                                DIGEST256_LEN));
  
    /* Get the KEYS part so we can derive the CLIENT-ID and COOKIE-KEY. */
    keystream_length =
      build_descriptor_cookie_keys(subcredential, DIGEST256_LEN,
                                   auth_ephemeral_sk, client_auth_pk,
                                   &keystream);
    tor_assert(keystream_length > 0);
  
    /* Extract the CLIENT-ID and COOKIE-KEY from the KEYS. */
    memcpy(client_out->client_id, keystream, HS_DESC_CLIENT_ID_LEN);
    cookie_key = keystream + HS_DESC_CLIENT_ID_LEN;
  
    /* Random IV */
    crypto_strongest_rand(client_out->iv, sizeof(client_out->iv));
  
    /* This creates a cipher for AES. It can't fail. */
    cipher = crypto_cipher_new_with_iv_and_bits(cookie_key, client_out->iv,
                                                HS_DESC_COOKIE_KEY_BIT_SIZE);
    /* This can't fail. */
    crypto_cipher_encrypt(cipher, (char *) client_out->encrypted_cookie,
                          (const char *) descriptor_cookie,
                          HS_DESC_DESCRIPTOR_COOKIE_LEN);
  
    memwipe(keystream, 0, keystream_length);
    tor_free(keystream);
  
    crypto_cipher_free(cipher);
  }
  
  /** Free an authoriezd client object. */
  void
  hs_desc_authorized_client_free_(hs_desc_authorized_client_t *client)
  {
    tor_free(client);
  }
  
  /** 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);
    }
  }
  