commit 91b5d0789ff5606cf97346590567857bfd78f9ad Author: David Goulet dgoulet@ev0ke.net Date: Tue Mar 8 15:51:53 2016 -0500

prop224: Descriptor encoding implementation

Add hs_descriptor.{c|h} with the needed ABI to represent a descriptor and needed component.

Signed-off-by: David Goulet dgoulet@torproject.org Signed-off-by: George Kadianakis desnacked@riseup.net --- src/or/hs_descriptor.c | 768 +++++++++++++++++++++++++++++++++++++++++++++++++ src/or/hs_descriptor.h | 169 +++++++++++ src/or/include.am | 2 + src/or/torcert.h | 2 + 4 files changed, 941 insertions(+)

diff --git a/src/or/hs_descriptor.c b/src/or/hs_descriptor.c new file mode 100644 index 0000000..a349297 --- /dev/null +++ b/src/or/hs_descriptor.c @@ -0,0 +1,768 @@ +/* Copyright (c) 2016, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file hs_descriptor.c + * \brief Handle hidden service descriptor encoding/decoding. + **/ + +#include "hs_descriptor.h" + +#include "or.h" +#include "ed25519_cert.h" /* Trunnel interface. */ + +/* Constant string value used for the descriptor format. */ +static const char *str_hs_desc = "hs-descriptor"; +static const char *str_desc_cert = "descriptor-signing-key-cert"; +static const char *str_rev_counter = "revision-counter"; +static const char *str_encrypted = "encrypted"; +static const char *str_signature = "signature"; +static const char *str_lifetime = "descriptor-lifetime"; +/* Constant string value for the encrypted part of the descriptor. */ +static const char *str_create2_formats = "create2-formats"; +static const char *str_auth_required = "authentication-required"; +static const char *str_intro_point = "introduction-point"; +static const char *str_ip_auth_key = "auth-key"; +static const char *str_ip_enc_key = "enc-key"; +static const char *str_ip_enc_key_cert = "enc-key-certification"; +/* Constant string value for the construction to encrypt the encrypted data + * section. */ +static const char *str_enc_hsdir_data = "hsdir-encrypted-data"; + +/* Encode the ed25519 certificate <b>cert</b> and put the newly allocated + * string in <b>cert_str_out</b>. Return 0 on success else a negative value. */ +static int +encode_cert(const tor_cert_t *cert, char **cert_str_out) +{ + int ret = -1; + char *ed_cert_b64 = NULL; + size_t ed_cert_b64_len; + + tor_assert(cert); + tor_assert(cert_str_out); + + /* Get the encoded size and add the NUL byte. */ + ed_cert_b64_len = base64_encode_size(cert->encoded_len, + BASE64_ENCODE_MULTILINE) + 1; + ed_cert_b64 = tor_malloc_zero(ed_cert_b64_len); + + /* Base64 encode the encoded certificate. */ + if (base64_encode(ed_cert_b64, ed_cert_b64_len, + (const char *) cert->encoded, cert->encoded_len, + BASE64_ENCODE_MULTILINE) < 0) { + log_err(LD_BUG, "Couldn't base64-encode descriptor signing key cert!"); + goto err; + } + + /* Put everything together in a NUL terminated string. */ + tor_asprintf(cert_str_out, + "-----BEGIN ED25519 CERT-----\n" + "%s" + "-----END ED25519 CERT-----", + ed_cert_b64); + /* Success! */ + ret = 0; + +err: + tor_free(ed_cert_b64); + return ret; +} + +/* Encode the given link specifier objects into a newly allocated string. + * This can't fail so caller can always assume a valid string being + * returned. */ +static char * +encode_link_specifiers(const smartlist_t *specs) +{ + char *encoded_b64 = NULL; + link_specifier_list_t *lslist = link_specifier_list_new(); + + tor_assert(specs); + /* No link specifiers is a code flow error, can't happen. */ + tor_assert(smartlist_len(specs) > 0); + tor_assert(smartlist_len(specs) <= UINT8_MAX); + + link_specifier_list_set_n_spec(lslist, smartlist_len(specs)); + + SMARTLIST_FOREACH_BEGIN(specs, const hs_desc_link_specifier_t *, + spec) { + link_specifier_t *ls = link_specifier_new(); + link_specifier_set_ls_type(ls, spec->type); + + switch (spec->type) { + case LS_IPV4: + link_specifier_set_un_ipv4_addr(ls, + tor_addr_to_ipv4h(&spec->u.ap.addr)); + link_specifier_set_un_ipv4_port(ls, spec->u.ap.port); + /* Four bytes IPv4 and two bytes port. */ + link_specifier_set_ls_len(ls, sizeof(spec->u.ap.addr.addr.in_addr) + + sizeof(spec->u.ap.port)); + break; + case LS_IPV6: + { + size_t addr_len = link_specifier_getlen_un_ipv6_addr(ls); + const uint8_t *in6_addr = tor_addr_to_in6_addr8(&spec->u.ap.addr); + uint8_t *ipv6_array = link_specifier_getarray_un_ipv6_addr(ls); + memcpy(ipv6_array, in6_addr, addr_len); + link_specifier_set_un_ipv6_port(ls, spec->u.ap.port); + /* Sixteen bytes IPv6 and two bytes port. */ + link_specifier_set_ls_len(ls, addr_len + sizeof(spec->u.ap.port)); + break; + } + case LS_LEGACY_ID: + { + size_t legacy_id_len = link_specifier_getlen_un_legacy_id(ls); + uint8_t *legacy_id_array = link_specifier_getarray_un_legacy_id(ls); + memcpy(legacy_id_array, spec->u.legacy_id, legacy_id_len); + link_specifier_set_ls_len(ls, legacy_id_len); + break; + } + default: + tor_assert(0); + } + + 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 encryption key and return a newly allocated + * string with it. On failure, return NULL. */ +static char * +encode_enc_key(const ed25519_keypair_t *sig_key, + const hs_desc_intro_point_t *ip) +{ + char *encoded = NULL; + time_t now = time(NULL); + + tor_assert(sig_key); + tor_assert(ip); + + switch (ip->enc_key_type) { + case HS_DESC_KEY_TYPE_LEGACY: + { + char *key_str, b64_cert[256]; + ssize_t cert_len; + size_t key_str_len; + uint8_t *cert_data; + + /* Create cross certification cert. */ + cert_len = tor_make_rsa_ed25519_crosscert(&sig_key->pubkey, + ip->enc_key.legacy, + now + HS_DESC_CERT_LIFETIME, + &cert_data); + if (cert_len < 0) { + log_warn(LD_REND, "Unable to create legacy crosscert."); + goto err; + } + /* Encode cross cert. */ + if (base64_encode(b64_cert, sizeof(b64_cert), (const char *) cert_data, + cert_len, BASE64_ENCODE_MULTILINE) < 0) { + log_warn(LD_REND, "Unable to encode legacy crosscert."); + goto err; + } + /* Convert the encryption key to a string. */ + if (crypto_pk_write_public_key_to_string(ip->enc_key.legacy, &key_str, + &key_str_len) < 0) { + log_warn(LD_REND, "Unable to encode legacy encryption key."); + goto err; + } + tor_asprintf(&encoded, + "%s legacy\n%s" /* Newline is added by the call above. */ + "%s\n" + "-----BEGIN CROSSCERT-----\n" + "%s" + "-----END CROSSCERT-----", + str_ip_enc_key, key_str, + str_ip_enc_key_cert, b64_cert); + tor_free(key_str); + break; + } + case HS_DESC_KEY_TYPE_CURVE25519: + { + int signbit; + char *encoded_cert, key_fp_b64[CURVE25519_BASE64_PADDED_LEN + 1]; + ed25519_keypair_t curve_kp; + + if (ed25519_keypair_from_curve25519_keypair(&curve_kp, &signbit, + &ip->enc_key.curve25519)) { + goto err; + } + tor_cert_t *cross_cert = tor_cert_create(&curve_kp, CERT_TYPE_HS_IP_ENC, + &sig_key->pubkey, now, + HS_DESC_CERT_LIFETIME, + CERT_FLAG_INCLUDE_SIGNING_KEY); + memwipe(&curve_kp, 0, sizeof(curve_kp)); + if (!cross_cert) { + goto err; + } + if (encode_cert(cross_cert, &encoded_cert)) { + goto err; + } + if (curve25519_public_to_base64(key_fp_b64, + &ip->enc_key.curve25519.pubkey) < 0) { + tor_free(encoded_cert); + goto err; + } + tor_asprintf(&encoded, + "%s ntor %s\n" + "%s\n%s", + str_ip_enc_key, key_fp_b64, + str_ip_enc_key_cert, encoded_cert); + tor_free(encoded_cert); + break; + } + default: + tor_assert(0); + } + + err: + 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_keypair_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); + } + + /* Authentication key encoding. */ + { + char *encoded_cert; + if (encode_cert(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(sig_key, ip); + if (encoded_enc_key == NULL) { + goto err; + } + smartlist_add_asprintf(lines, "%s", encoded_enc_key); + tor_free(encoded_enc_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; +} + +/* Using a given decriptor object, build the secret input needed for the + * KDF and put it in the dst pointer which is an already allocated buffer + * of size dstlen. */ +static void +build_secret_input(const hs_descriptor_t *desc, uint8_t *dst, size_t dstlen) +{ + size_t offset = 0; + + tor_assert(desc); + tor_assert(dst); + tor_assert(HS_DESC_ENCRYPTED_SECRET_INPUT_LEN <= dstlen); + + /* XXX use the destination length as the memcpy length */ + /* Copy blinded public key. */ + memcpy(dst, desc->plaintext_data.blinded_kp.pubkey.pubkey, + sizeof(desc->plaintext_data.blinded_kp.pubkey.pubkey)); + offset += sizeof(desc->plaintext_data.blinded_kp.pubkey.pubkey); + /* Copy subcredential. */ + memcpy(dst + offset, desc->subcredential, sizeof(desc->subcredential)); + offset += sizeof(desc->subcredential); + /* Copy revision counter value. */ + set_uint64(dst + offset, tor_ntohll(desc->plaintext_data.revision_counter)); + offset += sizeof(uint64_t); + tor_assert(HS_DESC_ENCRYPTED_SECRET_INPUT_LEN == offset); +} + +/* Do the KDF construction and put the resulting data in key_out which is of + * key_out_len length. It uses SHAKE-256 as specified in the spec. */ +static void +build_kdf_key(const hs_descriptor_t *desc, + const uint8_t *salt, size_t salt_len, + uint8_t *key_out, size_t key_out_len) +{ + uint8_t secret_input[HS_DESC_ENCRYPTED_SECRET_INPUT_LEN]; + crypto_xof_t *xof; + + tor_assert(desc); + tor_assert(salt); + tor_assert(key_out); + + /* Build the secret input for the KDF computation. */ + build_secret_input(desc, secret_input, sizeof(secret_input)); + + xof = crypto_xof_new(); + /* Feed our KDF. [SHAKE it like a polaroid picture --Yawning]. */ + crypto_xof_add_bytes(xof, secret_input, sizeof(secret_input)); + crypto_xof_add_bytes(xof, salt, salt_len); + crypto_xof_add_bytes(xof, (const uint8_t *) str_enc_hsdir_data, + strlen(str_enc_hsdir_data)); + /* Eat from our KDF. */ + crypto_xof_squeeze_bytes(xof, key_out, key_out_len); + crypto_xof_free(xof); + memwipe(secret_input, 0, sizeof(secret_input)); +} + +/* Using the given descriptor and salt, run it through our KDF function and + * then extract a secret key in key_out, the IV in iv_out and MAC in mac_out. + * This function can't fail. */ +static void +build_secret_key_iv_mac(const hs_descriptor_t *desc, + const uint8_t *salt, size_t salt_len, + uint8_t *key_out, size_t key_len, + uint8_t *iv_out, size_t iv_len, + uint8_t *mac_out, size_t mac_len) +{ + size_t offset = 0; + uint8_t kdf_key[HS_DESC_ENCRYPTED_KDF_OUTPUT_LEN]; + + tor_assert(desc); + tor_assert(salt); + tor_assert(key_out); + tor_assert(iv_out); + tor_assert(mac_out); + + build_kdf_key(desc, salt, salt_len, kdf_key, sizeof(kdf_key)); + /* 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)); +} + +/* Using a key, salt and encrypted payload, build a MAC and put it in mac_out. + * The length of the mac key and salt must be fixed and if not, you can't rely + * on the result to be a valid MAC. 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; + + 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_key, mac_key_len); + 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); +} + +/* 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; + + /* Make sure we won't overflow. */ + tor_assert(plaintext_len <= + (SIZE_T_CEILING - HS_DESC_PLAINTEXT_PADDING_MULTIPLE)); + + /* Get the extra length we need to add. For example, if srclen is 234 bytes, + * this will expand to (2 * 128) == 256 thus an extra 22 bytes. */ + plaintext_padded_len = CEIL_DIV(plaintext_len, + HS_DESC_PLAINTEXT_PADDING_MULTIPLE) * + HS_DESC_PLAINTEXT_PADDING_MULTIPLE; + /* Can never be extra careful. Make sure we are _really_ padded. */ + tor_assert(!(plaintext_padded_len % HS_DESC_PLAINTEXT_PADDING_MULTIPLE)); + 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) +{ + 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); + + /* This creates a cipher for AES128. It can't fail. */ + cipher = crypto_cipher_new_with_iv((const char *) key, (const char *) iv); + /* This can't fail. */ + encrypted_len = build_plaintext_padding(plaintext, plaintext_len, + &padded_plaintext); + /* Extra precautions that we have a valie padding length. */ + tor_assert(encrypted_len <= HS_DESC_PADDED_PLAINTEXT_MAX_LEN); + tor_assert(!(encrypted_len % HS_DESC_PLAINTEXT_PADDING_MULTIPLE)); + /* 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 plaintext buffer and using the descriptor to get the + * keys. Set encrypted_out with the encrypted data and return the length of + * it. */ +static size_t +encrypt_descriptor_data(const hs_descriptor_t *desc, const char *plaintext, + char **encrypted_out) +{ + 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[CIPHER_KEY_LEN], secret_iv[CIPHER_IV_LEN]; + uint8_t mac_key[DIGEST256_LEN], mac[DIGEST256_LEN]; + + tor_assert(desc); + tor_assert(plaintext); + tor_assert(encrypted_out); + + /* Get our salt. The returned bytes are already hashed. */ + crypto_strongest_rand(salt, sizeof(salt)); + + /* KDF construction resulting in a key from which the secret key, IV and MAC + * key are extracted which is what we need for the encryption. */ + build_secret_key_iv_mac(desc, salt, sizeof(salt), + secret_key, sizeof(secret_key), + secret_iv, sizeof(secret_iv), + mac_key, sizeof(mac_key)); + + /* Build the encrypted part that is do the actual encryption. */ + encrypted_len = build_encrypted(secret_key, secret_iv, plaintext, + strlen(plaintext), &encrypted); + 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; +} + +/* Take care of encoding the encrypted data section and then encrypting it + * with the descriptor's key. 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_encrypted_data(const hs_descriptor_t *desc, + char **encrypted_blob_out) +{ + int ret = -1; + char *encoded_str, *encrypted_blob; + smartlist_t *lines = smartlist_new(); + + tor_assert(desc); + tor_assert(encrypted_blob_out); + + /* 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.auth_types && + smartlist_len(desc->encrypted_data.auth_types)) { + /* Put the authentication-required line. */ + char *buf = smartlist_join_strings(desc->encrypted_data.auth_types, " ", + 0, NULL); + smartlist_add_asprintf(lines, "%s %s\n", str_auth_required, buf); + tor_free(buf); + } + } + + /* 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_kp, + 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); + + /* Encrypt the section into an encrypted blob that we'll base64 encode + * before returning it. */ + { + char *enc_b64; + ssize_t enc_b64_len, ret_len, enc_len; + + enc_len = encrypt_descriptor_data(desc, encoded_str, &encrypted_blob); + tor_free(encoded_str); + /* 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); + *encrypted_blob_out = enc_b64; + } + /* Success! */ + ret = 0; + + err: + SMARTLIST_FOREACH(lines, char *, l, tor_free(l)); + smartlist_free(lines); + 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, char **encoded_out) +{ + int ret = -1; + char *encoded_str = NULL; + size_t encoded_len; + smartlist_t *lines = smartlist_new(); + + tor_assert(desc); + tor_assert(encoded_out); + tor_assert(desc->plaintext_data.version == 3); + + /* 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_HS_DESC_SIGN) { + 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 (encode_cert(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 encrypted data section. */ + { + char *enc_b64_blob; + if (encode_encrypted_data(desc, &enc_b64_blob) < 0) { + goto err; + } + smartlist_add_asprintf(lines, + "%s\n" + "-----BEGIN MESSAGE-----\n" + "%s" + "-----END MESSAGE-----", + str_encrypted, 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. */ + { + /* XXX: Add signature prefix. */ + ed25519_signature_t sig; + char ed_sig_b64[ED25519_SIG_BASE64_LEN + 1]; + if (ed25519_sign(&sig, (const uint8_t *) encoded_str, encoded_len, + &desc->plaintext_data.signing_kp) < 0) { + log_warn(LD_BUG, "Can't sign encoded HS descriptor!"); + tor_free(encoded_str); + goto err; + } + if (ed25519_signature_to_base64(ed_sig_b64, &sig) < 0) { + log_warn(LD_BUG, "Can't base64 encode descriptor signature!"); + tor_free(encoded_str); + goto err; + } + /* Create the signature line. */ + smartlist_add_asprintf(lines, "%s %s", str_signature, ed_sig_b64); + } + /* Free previous string that we used so compute the signature. */ + tor_free(encoded_str); + encoded_str = smartlist_join_strings(lines, "\n", 1, NULL); + *encoded_out = encoded_str; + + /* XXX: Decode the generated descriptor as an extra validation. */ + + /* XXX: Trigger a control port event. */ + + /* Success! */ + ret = 0; + + err: + SMARTLIST_FOREACH(lines, char *, l, tor_free(l)); + smartlist_free(lines); + return ret; +} + +/* Table of encode function version specific. The function 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, + char **encoded_out) = +{ + /* v0 */ NULL, /* v1 */ NULL, /* v2 */ NULL, + desc_encode_v3, +}; + +/* Encode the given descriptor desc. 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 untouched. */ +int +hs_desc_encode_descriptor(const hs_descriptor_t *desc, char **encoded_out) +{ + int ret = -1; + + tor_assert(desc); + tor_assert(encoded_out); + + /* Make sure we support the version of the descriptor format. */ + if (!hs_desc_is_supported_version(desc->plaintext_data.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) >= desc->plaintext_data.version); + tor_assert(encode_handlers[desc->plaintext_data.version]); + + ret = encode_handlers[desc->plaintext_data.version](desc, encoded_out); + if (ret < 0) { + goto err; + } + + err: + return ret; +} diff --git a/src/or/hs_descriptor.h b/src/or/hs_descriptor.h new file mode 100644 index 0000000..98dbb22 --- /dev/null +++ b/src/or/hs_descriptor.h @@ -0,0 +1,169 @@ +/* Copyright (c) 2016, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file hs_descriptor.h + * \brief Header file for hs_descriptor.c + **/ + +#ifndef TOR_HS_DESCRIPTOR_H +#define TOR_HS_DESCRIPTOR_H + +#include <stdint.h> + +#include "address.h" +#include "container.h" +#include "crypto.h" +#include "crypto_ed25519.h" +#include "torcert.h" + +/* The earliest descriptor format version we support. */ +#define HS_DESC_SUPPORTED_FORMAT_VERSION_MIN 3 +/* The latest descriptor format version we support. */ +#define HS_DESC_SUPPORTED_FORMAT_VERSION_MAX 3 + +/* Lifetime of certificate in the descriptor. This defines the lifetime of the + * descriptor signing key and the cross certification cert of that key. */ +#define HS_DESC_CERT_LIFETIME (24 * 60 * 60) +/* Length of the salt needed for the encrypted section of a descriptor. */ +#define HS_DESC_ENCRYPTED_SALT_LEN 16 +/* Length of the secret input needed for the KDF construction which derives + * the encryption key for the encrypted data section of the descriptor. This + * adds up to 68 bytes being the blinded key, hashed subcredential and + * revision counter. */ +#define HS_DESC_ENCRYPTED_SECRET_INPUT_LEN \ + ED25519_PUBKEY_LEN + DIGEST256_LEN + sizeof(uint64_t) +/* Length of the KDF output value which is the length of the secret key, + * the secret IV and MAC key length which is the length of H() output. */ +#define HS_DESC_ENCRYPTED_KDF_OUTPUT_LEN \ + CIPHER_KEY_LEN + CIPHER_IV_LEN + DIGEST256_LEN +/* We need to pad the plaintext version of the encrypted data section before + * encryption and it has to be a multiple of this value. */ +#define HS_DESC_PLAINTEXT_PADDING_MULTIPLE 128 +/* XXX: Let's make sure this makes sense as an upper limit for the padded + * plaintext section. Then we should enforce it as now only an assert will be + * triggered if we are above it. */ +/* Once padded, this is the maximum length in bytes for the plaintext. */ +#define HS_DESC_PADDED_PLAINTEXT_MAX_LEN 8192 + +/* Type of encryption key in the descriptor. */ +typedef enum { + HS_DESC_KEY_TYPE_LEGACY = 1, + HS_DESC_KEY_TYPE_CURVE25519 = 2, +} hs_desc_key_type_t; + +/* Link specifier object that contains information on how to extend to the + * relay that is the address, port and handshake type. */ +typedef struct hs_desc_link_specifier_t { + /* Indicate the type of link specifier. See trunnel ed25519_cert + * specification. */ + uint8_t type; + + /* It's either an address/port or a legacy identity fingerprint. */ + union { + /* IP address and port of the relay use to extend. */ + tor_addr_port_t ap; + /* Legacy identity. A 20-byte SHA1 identity fingerprint. */ + uint8_t legacy_id[DIGEST_LEN]; + } u; +} hs_desc_link_specifier_t; + +/* Introduction point information located in a descriptor. */ +typedef struct hs_desc_intro_point_t { + /* Link specifier(s) which details how to extend to the relay. This list + * contains hs_desc_link_specifier_t object. It MUST have at least one. */ + smartlist_t *link_specifiers; + + /* Authentication key used to establish the introduction point circuit and + * cross-certifies the blinded public key for the replica thus signed by + * the blinded key and in turn signs it. */ + tor_cert_t *auth_key_cert; + + /* Encryption key type so we know which one to use in the union below. */ + hs_desc_key_type_t enc_key_type; + + /* Keys are mutually exclusive thus the union. */ + union { + /* Encryption key used to encrypt request to hidden service. */ + curve25519_keypair_t curve25519; + + /* Backward compat: RSA 1024 encryption key for legacy purposes. + * Mutually exclusive with enc_key. */ + crypto_pk_t *legacy; + } enc_key; +} hs_desc_intro_point_t; + +/* The encrypted data section of a descriptor. Obviously the data in this is + * in plaintext but encrypted once encoded. */ +typedef struct hs_desc_encrypted_data_t { + /* Bitfield of CREATE2 cell supported formats. The only currently supported + * format is ntor. */ + unsigned int create2_ntor : 1; + + /* A list of authentication types that a client must at least support one + * in order to contact the service. Contains NULL terminated strings. */ + smartlist_t *auth_types; + + /* A list of intro points. Contains hs_desc_intro_point_t objects. */ + smartlist_t *intro_points; +} hs_desc_encrypted_data_t; + +/* Plaintext data that is unencrypted information of the descriptor. */ +typedef struct hs_desc_plaintext_data_t { + /* Version of the descriptor format. Spec specifies this field as a + * positive integer. */ + uint32_t version; + + /* The lifetime of the descriptor in seconds. */ + uint32_t lifetime_sec; + + /* Certificate with the short-term ed22519 descriptor signing key for the + * replica which is signed by the blinded public key for that replica. */ + tor_cert_t *signing_key_cert; + + /* Signing keypair which is used to sign the descriptor. Same public key + * as in the signing key certificate. */ + ed25519_keypair_t signing_kp; + + /* Blinded keypair used for this descriptor derived from the master + * identity key and generated for a specific replica number. */ + ed25519_keypair_t blinded_kp; + + /* Revision counter is incremented at each upload, regardless of whether + * the descriptor has changed. This avoids leaking whether the descriptor + * has changed. Spec specifies this as a 8 bytes positive integer. */ + uint64_t revision_counter; +} hs_desc_plaintext_data_t; + +/* Service descriptor in its decoded form. */ +typedef struct hs_descriptor_t { + /* Contains the plaintext part of the descriptor. */ + hs_desc_plaintext_data_t plaintext_data; + + /* The following contains what's in the encrypted part of the descriptor. + * It's only encrypted in the encoded version of the descriptor thus the + * data contained in that object is in plaintext. */ + hs_desc_encrypted_data_t encrypted_data; + + /* Subcredentials of a service, used by the client and service to decrypt + * the encrypted data. */ + uint8_t subcredential[DIGEST256_LEN]; +} hs_descriptor_t; + +/* Return true iff the given descriptor format version is supported. */ +static inline int +hs_desc_is_supported_version(uint32_t version) +{ + if (version < HS_DESC_SUPPORTED_FORMAT_VERSION_MIN || + version > HS_DESC_SUPPORTED_FORMAT_VERSION_MAX) { + return 0; + } + return 1; +} + +/* Public API. */ + +int hs_desc_encode_descriptor(const hs_descriptor_t *desc, + char **encoded_out); + +#endif /* TOR_HS_DESCRIPTOR_H */ diff --git a/src/or/include.am b/src/or/include.am index 3ae45cb..e28bda4 100644 --- a/src/or/include.am +++ b/src/or/include.am @@ -49,6 +49,7 @@ LIBTOR_A_SOURCES = \ src/or/ext_orport.c \ src/or/hibernate.c \ src/or/hs_common.c \ + src/or/hs_descriptor.c \ src/or/keypin.c \ src/or/main.c \ src/or/microdesc.c \ @@ -159,6 +160,7 @@ ORHEADERS = \ src/or/entrynodes.h \ src/or/hibernate.h \ src/or/hs_common.h \ + src/or/hs_descriptor.h \ src/or/keypin.h \ src/or/main.h \ src/or/microdesc.h \ diff --git a/src/or/torcert.h b/src/or/torcert.h index 4665e67..29bc0fc 100644 --- a/src/or/torcert.h +++ b/src/or/torcert.h @@ -11,6 +11,8 @@ #define CERT_TYPE_ID_SIGNING 0x04 #define CERT_TYPE_SIGNING_LINK 0x05 #define CERT_TYPE_SIGNING_AUTH 0x06 +#define CERT_TYPE_HS_DESC_SIGN 0x08 +#define CERT_TYPE_HS_IP_AUTH 0x09 #define CERT_TYPE_ONION_ID 0x0A #define CERT_TYPE_HS_IP_ENC 0x0B