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tor/src/or/hs_descriptor.c

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