diff options
Diffstat (limited to 'src/feature/hs/hs_descriptor.c')
| -rw-r--r-- | src/feature/hs/hs_descriptor.c | 101 |
1 files changed, 68 insertions, 33 deletions
diff --git a/src/feature/hs/hs_descriptor.c b/src/feature/hs/hs_descriptor.c index 8515314b38..1b2008c804 100644 --- a/src/feature/hs/hs_descriptor.c +++ b/src/feature/hs/hs_descriptor.c @@ -1400,6 +1400,50 @@ encrypted_data_length_is_valid(size_t len) return 0; } +/* Build the KEYS component for the authorized client computation. The format + * of the construction is: + * + * SECRET_SEED = x25519(sk, pk) + * KEYS = KDF(subcredential | SECRET_SEED, 40) + * + * Set the <b>keys_out</b> argument to point to the buffer containing the KEYS, + * and return the buffer's length. The caller should wipe and free its content + * once done with it. This function can't fail. */ +static size_t +build_descriptor_cookie_keys(const uint8_t *subcredential, + size_t subcredential_len, + const curve25519_secret_key_t *sk, + const curve25519_public_key_t *pk, + uint8_t **keys_out) +{ + uint8_t secret_seed[CURVE25519_OUTPUT_LEN]; + uint8_t *keystream; + size_t keystream_len = HS_DESC_CLIENT_ID_LEN + HS_DESC_COOKIE_KEY_LEN; + crypto_xof_t *xof; + + tor_assert(subcredential); + tor_assert(sk); + tor_assert(pk); + tor_assert(keys_out); + + keystream = tor_malloc_zero(keystream_len); + + /* Calculate x25519(sk, pk) to get the secret seed. */ + curve25519_handshake(secret_seed, sk, pk); + + /* Calculate KEYS = KDF(subcredential | SECRET_SEED, 40) */ + xof = crypto_xof_new(); + crypto_xof_add_bytes(xof, subcredential, subcredential_len); + crypto_xof_add_bytes(xof, secret_seed, sizeof(secret_seed)); + crypto_xof_squeeze_bytes(xof, keystream, keystream_len); + crypto_xof_free(xof); + + memwipe(secret_seed, 0, sizeof(secret_seed)); + + *keys_out = keystream; + return keystream_len; +} + /* Decrypt the descriptor cookie given the descriptor, the auth client, * and the client secret key. On sucess, return 0 and a newly allocated * descriptor cookie descriptor_cookie_out. On error or if the client id @@ -1412,12 +1456,11 @@ decrypt_descriptor_cookie(const hs_descriptor_t *desc, uint8_t **descriptor_cookie_out) { int ret = -1; - uint8_t secret_seed[CURVE25519_OUTPUT_LEN]; - uint8_t keystream[HS_DESC_CLIENT_ID_LEN + HS_DESC_COOKIE_KEY_LEN]; - uint8_t *cookie_key = NULL; + uint8_t *keystream = NULL; + size_t keystream_length = 0; uint8_t *descriptor_cookie = NULL; + const uint8_t *cookie_key = NULL; crypto_cipher_t *cipher = NULL; - crypto_xof_t *xof = NULL; tor_assert(desc); tor_assert(client); @@ -1429,16 +1472,13 @@ decrypt_descriptor_cookie(const hs_descriptor_t *desc, sizeof(*client_auth_sk))); tor_assert(!tor_mem_is_zero((char *) desc->subcredential, DIGEST256_LEN)); - /* Calculate x25519(client_x, hs_Y) */ - curve25519_handshake(secret_seed, client_auth_sk, - &desc->superencrypted_data.auth_ephemeral_pubkey); - - /* Calculate KEYS = KDF(subcredential | SECRET_SEED, 40) */ - xof = crypto_xof_new(); - crypto_xof_add_bytes(xof, desc->subcredential, DIGEST256_LEN); - crypto_xof_add_bytes(xof, secret_seed, sizeof(secret_seed)); - crypto_xof_squeeze_bytes(xof, keystream, sizeof(keystream)); - crypto_xof_free(xof); + /* Get the KEYS component to derive the CLIENT-ID and COOKIE-KEY. */ + keystream_length = + build_descriptor_cookie_keys(desc->subcredential, DIGEST256_LEN, + client_auth_sk, + &desc->superencrypted_data.auth_ephemeral_pubkey, + &keystream); + tor_assert(keystream_length > 0); /* If the client id of auth client is not the same as the calculcated * client id, it means that this auth client is invaild according to the @@ -1464,8 +1504,8 @@ decrypt_descriptor_cookie(const hs_descriptor_t *desc, if (cipher) { crypto_cipher_free(cipher); } - memwipe(secret_seed, 0, sizeof(secret_seed)); - memwipe(keystream, 0, sizeof(keystream)); + memwipe(keystream, 0, keystream_length); + tor_free(keystream); return ret; } @@ -2878,11 +2918,10 @@ hs_desc_build_authorized_client(const uint8_t *subcredential, const uint8_t *descriptor_cookie, hs_desc_authorized_client_t *client_out) { - uint8_t secret_seed[CURVE25519_OUTPUT_LEN]; - uint8_t keystream[HS_DESC_CLIENT_ID_LEN + HS_DESC_COOKIE_KEY_LEN]; - uint8_t *cookie_key; + uint8_t *keystream = NULL; + size_t keystream_length = 0; + const uint8_t *cookie_key; crypto_cipher_t *cipher; - crypto_xof_t *xof; tor_assert(client_auth_pk); tor_assert(auth_ephemeral_sk); @@ -2898,18 +2937,14 @@ hs_desc_build_authorized_client(const uint8_t *subcredential, tor_assert(!tor_mem_is_zero((char *) subcredential, DIGEST256_LEN)); - /* Calculate x25519(hs_y, client_X) */ - curve25519_handshake(secret_seed, - auth_ephemeral_sk, - client_auth_pk); - - /* Calculate KEYS = KDF(subcredential | SECRET_SEED, 40) */ - xof = crypto_xof_new(); - crypto_xof_add_bytes(xof, subcredential, DIGEST256_LEN); - crypto_xof_add_bytes(xof, secret_seed, sizeof(secret_seed)); - crypto_xof_squeeze_bytes(xof, keystream, sizeof(keystream)); - crypto_xof_free(xof); + /* Get the KEYS part so we can derive the CLIENT-ID and COOKIE-KEY. */ + keystream_length = + build_descriptor_cookie_keys(subcredential, DIGEST256_LEN, + auth_ephemeral_sk, client_auth_pk, + &keystream); + tor_assert(keystream_length > 0); + /* Extract the CLIENT-ID and COOKIE-KEY from the KEYS. */ memcpy(client_out->client_id, keystream, HS_DESC_CLIENT_ID_LEN); cookie_key = keystream + HS_DESC_CLIENT_ID_LEN; @@ -2924,8 +2959,8 @@ hs_desc_build_authorized_client(const uint8_t *subcredential, (const char *) descriptor_cookie, HS_DESC_DESCRIPTOR_COOKIE_LEN); - memwipe(secret_seed, 0, sizeof(secret_seed)); - memwipe(keystream, 0, sizeof(keystream)); + memwipe(keystream, 0, keystream_length); + tor_free(keystream); crypto_cipher_free(cipher); } |