commit cff1fd63f16e83e4620afc9a8219f44e8b88b592 Author: David Goulet dgoulet@torproject.org Date: Tue Jun 28 16:27:01 2016 -0400

prop224: Descriptor decoding implementation

Closes #18571

Signed-off-by: David Goulet dgoulet@torproject.org Signed-off-by: George Kadianakis desnacked@riseup.net --- src/or/hs_descriptor.c | 1191 +++++++++++++++++++++++++++++++++++++++++++++++- src/or/hs_descriptor.h | 41 ++ src/or/parsecommon.h | 14 + 3 files changed, 1225 insertions(+), 21 deletions(-)

diff --git a/src/or/hs_descriptor.c b/src/or/hs_descriptor.c index a349297..bc7d51f 100644 --- a/src/or/hs_descriptor.c +++ b/src/or/hs_descriptor.c @@ -10,24 +10,125 @@

#include "or.h" #include "ed25519_cert.h" /* Trunnel interface. */ +#include "parsecommon.h" +#include "rendcache.h"

/* 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"; +#define str_hs_desc "hs-descriptor" +#define str_desc_cert "descriptor-signing-key-cert" +#define str_rev_counter "revision-counter" +#define str_encrypted "encrypted" +#define str_signature "signature" +#define 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"; +#define str_create2_formats "create2-formats" +#define str_auth_required "authentication-required" +#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-certification" +#define str_intro_point_start "\n" str_intro_point " " /* Constant string value for the construction to encrypt the encrypted data * section. */ -static const char *str_enc_hsdir_data = "hsdir-encrypted-data"; +#define str_enc_hsdir_data "hsdir-encrypted-data" +/* Prefix required to compute/verify HS desc signatures */ +#define str_desc_sig_prefix "Tor onion service descriptor sig v3" + +/* Authentication supported types. */ +static const struct { + hs_desc_auth_type_t type; + const char *identifier; +} auth_types[] = { + { HS_DESC_AUTH_PASSWORD, "password" }, + { 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_encrypted, R3_ENCRYPTED, NO_ARGS, NEED_OBJ), + T1_END(str_signature, R3_SIGNATURE, EQ(1), NO_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_auth_required, R3_AUTHENTICATION_REQUIRED, 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, ARGS, OBJ_OK), + T1_END(str_ip_enc_key_cert, R3_INTRO_ENC_KEY_CERTIFICATION, + NO_ARGS, NEED_OBJ), + 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); + if (ip->enc_key_type == HS_DESC_KEY_TYPE_LEGACY) { + crypto_pk_free(ip->enc_key.legacy); + } + 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->encrypted_blob) { + tor_free(desc->encrypted_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->auth_types) { + SMARTLIST_FOREACH(desc->auth_types, char *, a, tor_free(a)); + smartlist_free(desc->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)); +} + +/* === ENCODING === */

/* 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. */ @@ -689,11 +790,12 @@ desc_encode_v3(const hs_descriptor_t *desc, char **encoded_out)

/* 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) { + if (ed25519_sign_prefixed(&sig, + (const uint8_t *) encoded_str, encoded_len, + str_desc_sig_prefix, + &desc->plaintext_data.signing_kp) < 0) { log_warn(LD_BUG, "Can't sign encoded HS descriptor!"); tor_free(encoded_str); goto err; @@ -711,19 +813,1028 @@ desc_encode_v3(const hs_descriptor_t *desc, char **encoded_out) 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: +err: SMARTLIST_FOREACH(lines, char *, l, tor_free(l)); smartlist_free(lines); return ret; }

+/* === DECODING === */ + +/* XXX: Stub until this function is upstream. */ +static int +rsa_ed25519_crosscert_check(const uint8_t *crosscert, + const size_t crosscert_len, + const crypto_pk_t *rsa_id_key, + const ed25519_public_key_t *master_key) +{ + (void) crosscert; + (void) crosscert_len; + (void) rsa_id_key; + (void) master_key; + return 0; +} + +/* 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->auth_types = smartlist_new(); + smartlist_split_string(desc->auth_types, list, " ", 0, 0); + + /* Validate the types that we at least know about one. */ + SMARTLIST_FOREACH_BEGIN(desc->auth_types, const char *, auth) { + for (int idx = 0; auth_types[idx].identifier; idx++) { + if (!strncmp(auth, auth_types[idx].identifier, + strlen(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, time(NULL)) < 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) +{ + /* Check for the minimum length possible. */ + if (len < HS_DESC_ENCRYPTED_MIN_LEN) { + log_warn(LD_REND, "Length of descriptor's encrypted data is too small. " + "Got %lu but minimum value is %d", + len, HS_DESC_ENCRYPTED_MIN_LEN); + goto err; + } + + /* Encrypted data has the salt and MAC concatenated to it so remove those + * from the validation calculation. */ + len -= HS_DESC_ENCRYPTED_SALT_LEN + DIGEST256_LEN; + + /* Check that it's aligned on the block size of the crypto algorithm. */ + if (len % HS_DESC_PLAINTEXT_PADDING_MULTIPLE) { + log_warn(LD_REND, "Length of descriptor's encrypted data is invalid. " + "Got %lu which is not a multiple of %d.", + len, HS_DESC_PLAINTEXT_PADDING_MULTIPLE); + goto err; + } + + /* XXX: Check maximum size. Will strongly depends on the maximum intro point + * allowed we decide on and probably if they will all have to use the legacy + * key which is bigger than the ed25519 key. */ + + return 1; + err: + return 0; +} + +/* Decrypt the encrypted section of the descriptor using the given descriptor + * object desc. A newly allocated NUL terminated string is put in + * decrypted_out. Return the length of decrypted_out on success else 0 is + * returned and decrypted_out is set to NULL. */ +static size_t +desc_decrypt_data_v3(const hs_descriptor_t *desc, char **decrypted_out) +{ + uint8_t *decrypted = NULL; + uint8_t secret_key[CIPHER_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(desc->plaintext_data.encrypted_blob); + + /* Construction is as follow: SALT | ENCRYPTED_DATA | MAC */ + if (!encrypted_data_length_is_valid( + desc->plaintext_data.encrypted_blob_size)) { + goto err; + } + + /* Start of the blob thus the salt. */ + salt = desc->plaintext_data.encrypted_blob; + /* Next is the encrypted data. */ + encrypted = desc->plaintext_data.encrypted_blob + + HS_DESC_ENCRYPTED_SALT_LEN; + encrypted_len = desc->plaintext_data.encrypted_blob_size - + (HS_DESC_ENCRYPTED_SALT_LEN + DIGEST256_LEN); + + /* At the very end is the MAC. Make sure it's of the right size. */ + { + desc_mac = encrypted + encrypted_len; + size_t desc_mac_size = desc->plaintext_data.encrypted_blob_size - + (desc_mac - desc->plaintext_data.encrypted_blob); + if (desc_mac_size != DIGEST256_LEN) { + log_warn(LD_REND, "Service descriptor MAC length of encrypted data " + "is invalid (%lu, expected %u)", + desc_mac_size, DIGEST256_LEN); + goto err; + } + } + + /* 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)); + + /* 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((const char *) secret_key, + (const char *) secret_iv); + /* 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 NULL 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; +} + +/* 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; + tor_cert_t *cross_cert = 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_HS_IP_AUTH, + "introduction point auth-key") < 0) { + goto err; + } + + /* Exactly one "enc-key" ... */ + tok = find_by_keyword(tokens, R3_INTRO_ENC_KEY); + if (!strcmp(tok->args[0], "ntor")) { + /* "enc-key" SP "ntor" SP key NL */ + if (tok->n_args != 2 || tok->object_body) { + log_warn(LD_REND, "Introduction point ntor encryption key is invalid"); + goto err; + } + + if (curve25519_public_from_base64(&ip->enc_key.curve25519.pubkey, + tok->args[1]) < 0) { + log_warn(LD_REND, "Introduction point ntor encryption key is invalid"); + goto err; + } + ip->enc_key_type = HS_DESC_KEY_TYPE_CURVE25519; + } else if (!strcmp(tok->args[0], "legacy")) { + /* "enc-key" SP "legacy" NL key NL */ + if (!tok->key) { + log_warn(LD_REND, "Introduction point legacy encryption key is " + "invalid"); + goto err; + } + ip->enc_key.legacy = crypto_pk_dup_key(tok->key); + ip->enc_key_type = HS_DESC_KEY_TYPE_LEGACY; + } else { + /* Unknown key type so we can't use that introduction point. */ + log_warn(LD_REND, "Introduction point encryption key is unrecognized."); + goto err; + } + + /* "enc-key-certification" NL certificate NL */ + tok = find_by_keyword(tokens, R3_INTRO_ENC_KEY_CERTIFICATION); + tor_assert(tok->object_body); + /* Do the cross certification. */ + switch (ip->enc_key_type) { + case HS_DESC_KEY_TYPE_CURVE25519: + { + 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(&cross_cert, tok->object_body, + tok->object_size, CERT_TYPE_HS_IP_ENC, + "introduction point enc-key-certification") < 0) { + goto err; + } + break; + } + case HS_DESC_KEY_TYPE_LEGACY: + if (strcmp(tok->object_type, "CROSSCERT")) { + log_warn(LD_REND, "Introduction point legacy encryption key " + "cross-certification has an unknown format."); + goto err; + } + if (rsa_ed25519_crosscert_check((const uint8_t *) tok->object_body, + tok->object_size, ip->enc_key.legacy, + &desc->plaintext_data.signing_key_cert->signing_key)) { + log_warn(LD_REND, "Unable to cross certify the introduction point " + "legacy encryption key."); + goto err; + } + break; + default: + tor_assert(0); + break; + } + /* It is successfully cross certified. Flag the object. */ + ip->cross_certified = 1; + goto done; + + err: + desc_intro_point_free(ip); + ip = NULL; + + done: + tor_cert_free(cross_cert); + SMARTLIST_FOREACH(tokens, directory_token_t *, t, token_clear(t)); + smartlist_free(tokens); + 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: + if (chunked_desc) { + SMARTLIST_FOREACH(chunked_desc, char *, a, tor_free(a)); + smartlist_free(chunked_desc); + } + if (intro_points) { + 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_keypair_t *signing_kp, + 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_kp); + 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, 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 (BUG(!sig_start)) { + 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_kp->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_HS_DESC_SIGN, + "service descriptor signing key") < 0) { + goto err; + } + + /* Copy the public keys into signing_kp and blinded_kp */ + memcpy(&desc->signing_kp.pubkey, &desc->signing_key_cert->signed_key, + sizeof(ed25519_public_key_t)); + memcpy(&desc->blinded_kp.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_ENCRYPTED); + 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->encrypted_blob = tor_memdup(tok->object_body, tok->object_size); + desc->encrypted_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_kp, + 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 encrypted data that is located in the plaintext section in + * the descriptor as a blob of bytes. The following functions will use the + * keys found in the same section. */ + message_len = desc_decrypt_data_v3(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_AUTHENTICATION_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; + } + } + /* 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.encrypted_blob); + /* Let's make sure we have a supported version as well. By correctly parsing + * the plaintext, this should not fail. */ + if (BUG(!hs_desc_is_supported_version(version))) { + 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); + + encoded_len = strlen(encoded); + if (encoded_len >= HS_DESC_MAX_LEN) { + log_warn(LD_REND, "Service descriptor is too big (%lu bytes)", + 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 function are indexed by the * version number so v3 callback is at index 3 in the array. */ static int @@ -740,7 +1851,7 @@ static int * string. * * Return 0 on success and encoded_out is a valid pointer. On error, -1 is - * returned and encoded_out is untouched. */ + * returned and encoded_out is set to NULL. */ int hs_desc_encode_descriptor(const hs_descriptor_t *desc, char **encoded_out) { @@ -763,6 +1874,44 @@ hs_desc_encode_descriptor(const hs_descriptor_t *desc, char **encoded_out) goto err; }

- 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); +} diff --git a/src/or/hs_descriptor.h b/src/or/hs_descriptor.h index 98dbb22..7ee6861 100644 --- a/src/or/hs_descriptor.h +++ b/src/or/hs_descriptor.h @@ -22,6 +22,9 @@ /* The latest descriptor format version we support. */ #define HS_DESC_SUPPORTED_FORMAT_VERSION_MAX 3

+/* Maximum lifetime of a descriptor in seconds. The value is set at 12 hours + * which is 720 minutes or 43200 seconds. */ +#define HS_DESC_MAX_LIFETIME (12 * 60 * 60) /* 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) @@ -45,6 +48,22 @@ * 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 +/* Minimum length in bytes of the encrypted portion of the descriptor. */ +#define HS_DESC_ENCRYPTED_MIN_LEN \ + HS_DESC_ENCRYPTED_SALT_LEN + \ + HS_DESC_PLAINTEXT_PADDING_MULTIPLE + DIGEST256_LEN +/* Maximum length in bytes of a full hidden service descriptor. */ +#define HS_DESC_MAX_LEN 32768 // XXX justify +/* The minimum amount of fields a descriptor should contain. The parsing of + * the fields are version specific so the only required field, as a generic + * view of a descriptor, is 1 that is the version field. */ +#define HS_DESC_PLAINTEXT_MIN_FIELDS 1 + +/* Type of authentication in the descriptor. */ +typedef enum { + HS_DESC_AUTH_PASSWORD = 1, + HS_DESC_AUTH_ED25519 = 2, +} hs_desc_auth_type_t;

/* Type of encryption key in the descriptor. */ typedef enum { @@ -91,6 +110,10 @@ typedef struct hs_desc_intro_point_t { * Mutually exclusive with enc_key. */ crypto_pk_t *legacy; } enc_key; + + /* True iff the introduction point has passed the cross certification. Upon + * decoding an intro point, this must be true. */ + unsigned int cross_certified : 1; } hs_desc_intro_point_t;

/* The encrypted data section of a descriptor. Obviously the data in this is @@ -133,6 +156,12 @@ typedef struct hs_desc_plaintext_data_t { * 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; + + /* Decoding only: The base64-decoded encrypted blob from the descriptor */ + uint8_t *encrypted_blob; + + /* Decoding only: Size of the encrypted_blob */ + size_t encrypted_blob_size; } hs_desc_plaintext_data_t;

/* Service descriptor in its decoded form. */ @@ -163,7 +192,19 @@ hs_desc_is_supported_version(uint32_t version)

/* Public API. */

+void hs_descriptor_free(hs_descriptor_t *desc); +void hs_desc_plaintext_data_free(hs_desc_plaintext_data_t *desc); +void hs_desc_encrypted_data_free(hs_desc_encrypted_data_t *desc); + int hs_desc_encode_descriptor(const hs_descriptor_t *desc, char **encoded_out);

+int hs_desc_decode_descriptor(const char *encoded, + const uint8_t *subcredential, + hs_descriptor_t **desc_out); +int hs_desc_decode_plaintext(const char *encoded, + hs_desc_plaintext_data_t *plaintext); +int hs_desc_decode_encrypted(const hs_descriptor_t *desc, + hs_desc_encrypted_data_t *desc_out); + #endif /* TOR_HS_DESCRIPTOR_H */ diff --git a/src/or/parsecommon.h b/src/or/parsecommon.h index 3bb89ce..f87e62d 100644 --- a/src/or/parsecommon.h +++ b/src/or/parsecommon.h @@ -145,6 +145,20 @@ typedef enum { R_INTRODUCTION_POINTS, R_SIGNATURE,

+ R_HS_DESCRIPTOR, /* From version 3, this MUST be generic to all future + descriptor versions thus making it R_. */ + R3_DESC_LIFETIME, + R3_DESC_SIGNING_CERT, + R3_REVISION_COUNTER, + R3_ENCRYPTED, + R3_SIGNATURE, + R3_CREATE2_FORMATS, + R3_AUTHENTICATION_REQUIRED, + R3_INTRODUCTION_POINT, + R3_INTRO_AUTH_KEY, + R3_INTRO_ENC_KEY, + R3_INTRO_ENC_KEY_CERTIFICATION, + R_IPO_IDENTIFIER, R_IPO_IP_ADDRESS, R_IPO_ONION_PORT,