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Diffstat (limited to 'src/or/hs_descriptor.h')
| -rw-r--r-- | src/or/hs_descriptor.h | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/src/or/hs_descriptor.h b/src/or/hs_descriptor.h new file mode 100644 index 0000000000..98dbb22555 --- /dev/null +++ b/src/or/hs_descriptor.h @@ -0,0 +1,169 @@ +/* Copyright (c) 2016, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file hs_descriptor.h + * \brief Header file for hs_descriptor.c + **/ + +#ifndef TOR_HS_DESCRIPTOR_H +#define TOR_HS_DESCRIPTOR_H + +#include <stdint.h> + +#include "address.h" +#include "container.h" +#include "crypto.h" +#include "crypto_ed25519.h" +#include "torcert.h" + +/* The earliest descriptor format version we support. */ +#define HS_DESC_SUPPORTED_FORMAT_VERSION_MIN 3 +/* The latest descriptor format version we support. */ +#define HS_DESC_SUPPORTED_FORMAT_VERSION_MAX 3 + +/* Lifetime of certificate in the descriptor. This defines the lifetime of the + * descriptor signing key and the cross certification cert of that key. */ +#define HS_DESC_CERT_LIFETIME (24 * 60 * 60) +/* Length of the salt needed for the encrypted section of a descriptor. */ +#define HS_DESC_ENCRYPTED_SALT_LEN 16 +/* Length of the secret input needed for the KDF construction which derives + * the encryption key for the encrypted data section of the descriptor. This + * adds up to 68 bytes being the blinded key, hashed subcredential and + * revision counter. */ +#define HS_DESC_ENCRYPTED_SECRET_INPUT_LEN \ + ED25519_PUBKEY_LEN + DIGEST256_LEN + sizeof(uint64_t) +/* Length of the KDF output value which is the length of the secret key, + * the secret IV and MAC key length which is the length of H() output. */ +#define HS_DESC_ENCRYPTED_KDF_OUTPUT_LEN \ + CIPHER_KEY_LEN + CIPHER_IV_LEN + DIGEST256_LEN +/* We need to pad the plaintext version of the encrypted data section before + * encryption and it has to be a multiple of this value. */ +#define HS_DESC_PLAINTEXT_PADDING_MULTIPLE 128 +/* XXX: Let's make sure this makes sense as an upper limit for the padded + * plaintext section. Then we should enforce it as now only an assert will be + * triggered if we are above it. */ +/* Once padded, this is the maximum length in bytes for the plaintext. */ +#define HS_DESC_PADDED_PLAINTEXT_MAX_LEN 8192 + +/* Type of encryption key in the descriptor. */ +typedef enum { + HS_DESC_KEY_TYPE_LEGACY = 1, + HS_DESC_KEY_TYPE_CURVE25519 = 2, +} hs_desc_key_type_t; + +/* Link specifier object that contains information on how to extend to the + * relay that is the address, port and handshake type. */ +typedef struct hs_desc_link_specifier_t { + /* Indicate the type of link specifier. See trunnel ed25519_cert + * specification. */ + uint8_t type; + + /* It's either an address/port or a legacy identity fingerprint. */ + union { + /* IP address and port of the relay use to extend. */ + tor_addr_port_t ap; + /* Legacy identity. A 20-byte SHA1 identity fingerprint. */ + uint8_t legacy_id[DIGEST_LEN]; + } u; +} hs_desc_link_specifier_t; + +/* Introduction point information located in a descriptor. */ +typedef struct hs_desc_intro_point_t { + /* Link specifier(s) which details how to extend to the relay. This list + * contains hs_desc_link_specifier_t object. It MUST have at least one. */ + smartlist_t *link_specifiers; + + /* Authentication key used to establish the introduction point circuit and + * cross-certifies the blinded public key for the replica thus signed by + * the blinded key and in turn signs it. */ + tor_cert_t *auth_key_cert; + + /* Encryption key type so we know which one to use in the union below. */ + hs_desc_key_type_t enc_key_type; + + /* Keys are mutually exclusive thus the union. */ + union { + /* Encryption key used to encrypt request to hidden service. */ + curve25519_keypair_t curve25519; + + /* Backward compat: RSA 1024 encryption key for legacy purposes. + * Mutually exclusive with enc_key. */ + crypto_pk_t *legacy; + } enc_key; +} hs_desc_intro_point_t; + +/* The encrypted data section of a descriptor. Obviously the data in this is + * in plaintext but encrypted once encoded. */ +typedef struct hs_desc_encrypted_data_t { + /* Bitfield of CREATE2 cell supported formats. The only currently supported + * format is ntor. */ + unsigned int create2_ntor : 1; + + /* A list of authentication types that a client must at least support one + * in order to contact the service. Contains NULL terminated strings. */ + smartlist_t *auth_types; + + /* A list of intro points. Contains hs_desc_intro_point_t objects. */ + smartlist_t *intro_points; +} hs_desc_encrypted_data_t; + +/* Plaintext data that is unencrypted information of the descriptor. */ +typedef struct hs_desc_plaintext_data_t { + /* Version of the descriptor format. Spec specifies this field as a + * positive integer. */ + uint32_t version; + + /* The lifetime of the descriptor in seconds. */ + uint32_t lifetime_sec; + + /* Certificate with the short-term ed22519 descriptor signing key for the + * replica which is signed by the blinded public key for that replica. */ + tor_cert_t *signing_key_cert; + + /* Signing keypair which is used to sign the descriptor. Same public key + * as in the signing key certificate. */ + ed25519_keypair_t signing_kp; + + /* Blinded keypair used for this descriptor derived from the master + * identity key and generated for a specific replica number. */ + ed25519_keypair_t blinded_kp; + + /* Revision counter is incremented at each upload, regardless of whether + * the descriptor has changed. This avoids leaking whether the descriptor + * has changed. Spec specifies this as a 8 bytes positive integer. */ + uint64_t revision_counter; +} hs_desc_plaintext_data_t; + +/* Service descriptor in its decoded form. */ +typedef struct hs_descriptor_t { + /* Contains the plaintext part of the descriptor. */ + hs_desc_plaintext_data_t plaintext_data; + + /* The following contains what's in the encrypted part of the descriptor. + * It's only encrypted in the encoded version of the descriptor thus the + * data contained in that object is in plaintext. */ + hs_desc_encrypted_data_t encrypted_data; + + /* Subcredentials of a service, used by the client and service to decrypt + * the encrypted data. */ + uint8_t subcredential[DIGEST256_LEN]; +} hs_descriptor_t; + +/* Return true iff the given descriptor format version is supported. */ +static inline int +hs_desc_is_supported_version(uint32_t version) +{ + if (version < HS_DESC_SUPPORTED_FORMAT_VERSION_MIN || + version > HS_DESC_SUPPORTED_FORMAT_VERSION_MAX) { + return 0; + } + return 1; +} + +/* Public API. */ + +int hs_desc_encode_descriptor(const hs_descriptor_t *desc, + char **encoded_out); + +#endif /* TOR_HS_DESCRIPTOR_H */ |