tor/src/feature/hs/hs_service.h

/* Copyright (c) 2016-2020, The Tor Project, Inc. */
/* See LICENSE for licensing information */

/**
 * \file hs_service.h
 * \brief Header file containing service data for the HS subsytem.
 **/

#ifndef TOR_HS_SERVICE_H
#define TOR_HS_SERVICE_H

#include "lib/crypt_ops/crypto_curve25519.h"
#include "lib/crypt_ops/crypto_ed25519.h"
#include "feature/hs_common/replaycache.h"

#include "feature/hs/hs_common.h"
#include "feature/hs/hs_descriptor.h"
#include "feature/hs/hs_ident.h"
#include "feature/hs/hs_intropoint.h"

/* Trunnel */
#include "trunnel/hs/cell_establish_intro.h"

#include "ext/ht.h"

/** When loading and configuring a service, this is the default version it will
 * be configured for as it is possible that no HiddenServiceVersion is
 * present. */
#define HS_SERVICE_DEFAULT_VERSION HS_VERSION_THREE

/** As described in the specification, service publishes their next descriptor
 * at a random time between those two values (in seconds). */
#define HS_SERVICE_NEXT_UPLOAD_TIME_MIN (60 * 60)
/** Maximum interval for uploading next descriptor (in seconds). */
#define HS_SERVICE_NEXT_UPLOAD_TIME_MAX (120 * 60)

/** Service side introduction point. */
typedef struct hs_service_intro_point_t {
  /** Top level intropoint "shared" data between client/service. */
  hs_intropoint_t base;

  /** Onion key of the introduction point used to extend to it for the ntor
   * handshake. */
  curve25519_public_key_t onion_key;

  /** Authentication keypair used to create the authentication certificate
   * which is published in the descriptor. */
  ed25519_keypair_t auth_key_kp;

  /** Encryption keypair for the "ntor" type. */
  curve25519_keypair_t enc_key_kp;

  /** Legacy key if that intro point doesn't support v3. This should be used if
   * the base object legacy flag is set. */
  crypto_pk_t *legacy_key;
  /** Legacy key SHA1 public key digest. This should be used only if the base
   * object legacy flag is set. */
  uint8_t legacy_key_digest[DIGEST_LEN];

  /** Amount of INTRODUCE2 cell accepted from this intro point. */
  uint64_t introduce2_count;

  /** Maximum number of INTRODUCE2 cell this intro point should accept. */
  uint64_t introduce2_max;

  /** The time at which this intro point should expire and stop being used. */
  time_t time_to_expire;

  /** The amount of circuit creation we've made to this intro point. This is
   * incremented every time we do a circuit relaunch on this intro point which
   * is triggered when the circuit dies but the node is still in the
   * consensus. After MAX_INTRO_POINT_CIRCUIT_RETRIES, we give up on it. */
  uint32_t circuit_retries;

  /** Replay cache recording the encrypted part of an INTRODUCE2 cell that the
   * circuit associated with this intro point has received. This is used to
   * prevent replay attacks. */
  replaycache_t *replay_cache;

  /** Support the INTRO2 DoS defense. If set, the DoS extension described by
   * proposal 305 is sent. */
  unsigned int support_intro2_dos_defense : 1;
} hs_service_intro_point_t;

/** Object handling introduction points of a service. */
typedef struct hs_service_intropoints_t {
  /** The time at which we've started our retry period to build circuits. We
   * don't want to stress circuit creation so we can only retry for a certain
   * time and then after we stop and wait. */
  time_t retry_period_started;

  /** Number of circuit we've launched during a single retry period. */
  unsigned int num_circuits_launched;

  /** Contains the current hs_service_intro_point_t objects indexed by
   * authentication public key. */
  digest256map_t *map;

  /** Contains node's identity key digest that were introduction point for this
   * descriptor but were retried to many times. We keep those so we avoid
   * re-picking them over and over for a circuit retry period.
   * XXX: Once we have #22173, change this to only use ed25519 identity. */
  digestmap_t *failed_id;
} hs_service_intropoints_t;

/** Representation of a service descriptor.
 *
 * Some elements of the descriptor are mutable whereas others are immutable:
 *
 * Immutable elements are initialized once when the descriptor is built (when
 * service descriptors gets rotated). This means that these elements are
 * initialized once and then they don't change for the lifetime of the
 * descriptor. See build_service_descriptor().
 *
 * Mutable elements are initialized when we build the descriptor but they are
 * also altered during the lifetime of the descriptor. They could be
 * _refreshed_ everytime we upload the descriptor (which happens multiple times
 * over the lifetime of the descriptor), or through periodic events. We do this
 * for elements like the descriptor revision counter and various
 * certificates. See refresh_service_descriptor() and
 * update_service_descriptor_intro_points().
 */
typedef struct hs_service_descriptor_t {
  /** Immutable: Client authorization ephemeral keypair. */
  curve25519_keypair_t auth_ephemeral_kp;

  /** Immutable: Descriptor cookie used to encrypt the descriptor, when the
   * client authorization is enabled */
  uint8_t descriptor_cookie[HS_DESC_DESCRIPTOR_COOKIE_LEN];

  /** Immutable: Descriptor signing keypair. */
  ed25519_keypair_t signing_kp;

  /** Immutable: Blinded keypair derived from the master identity public
   * key. */
  ed25519_keypair_t blinded_kp;

  /** Immutable: The time period number this descriptor has been created
   * for. */
  uint64_t time_period_num;

  /** Immutable: The OPE cipher for encrypting revision counters for this
   *  descriptor.  Tied to the descriptor blinded key. */
  struct crypto_ope_t *ope_cipher;

  /** Mutable: Decoded descriptor. This object is used for encoding when the
   * service publishes the descriptor. */
  hs_descriptor_t *desc;

  /** Mutable: When is the next time when we should upload the descriptor. */
  time_t next_upload_time;

  /** Mutable: Introduction points assign to this descriptor which contains
   * hs_service_intropoints_t object indexed by authentication key (the RSA key
   * if the node is legacy). */
  hs_service_intropoints_t intro_points;

  /** Mutable: True iff we have missing intro points for this descriptor
   * because we couldn't pick any nodes. */
  unsigned int missing_intro_points : 1;

  /** Mutable: List of the responsible HSDirs (their b64ed identity digest)
   *  last time we uploaded this descriptor. If the set of responsible HSDirs
   *  is different from this list, this means we received new dirinfo and we
   *  need to reupload our descriptor. */
  smartlist_t *previous_hsdirs;
} hs_service_descriptor_t;

/** Service key material. */
typedef struct hs_service_keys_t {
  /** Master identify public key. */
  ed25519_public_key_t identity_pk;
  /** Master identity private key. */
  ed25519_secret_key_t identity_sk;
  /** True iff the key is kept offline which means the identity_sk MUST not be
   * used in that case. */
  unsigned int is_identify_key_offline : 1;
} hs_service_keys_t;

/** Service side configuration of client authorization. */
typedef struct hs_service_authorized_client_t {
  /** The client auth public key used to encrypt the descriptor cookie. */
  curve25519_public_key_t client_pk;
} hs_service_authorized_client_t;

/** Which protocol to use for exporting HS client circuit ID. */
typedef enum {
  /** Don't expose the circuit id. */
  HS_CIRCUIT_ID_PROTOCOL_NONE,

  /** Use the HAProxy proxy protocol. */
  HS_CIRCUIT_ID_PROTOCOL_HAPROXY
} hs_circuit_id_protocol_t;

/** Service configuration. The following are set from the torrc options either
 * set by the configuration file or by the control port. Nothing else should
 * change those values. */
typedef struct hs_service_config_t {
  /** Protocol version of the service. Specified by HiddenServiceVersion
   * option. */
  uint32_t version;

  /** Have we explicitly set HiddenServiceVersion? */
  unsigned int hs_version_explicitly_set : 1;

  /** List of rend_service_port_config_t */
  smartlist_t *ports;

  /** Path on the filesystem where the service persistent data is stored. NULL
   * if the service is ephemeral. Specified by HiddenServiceDir option. */
  char *directory_path;

  /** The maximum number of simultaneous streams per rendezvous circuit that
   * are allowed to be created. No limit if 0. Specified by
   * HiddenServiceMaxStreams option. */
  uint64_t max_streams_per_rdv_circuit;

  /** If true, we close circuits that exceed the max_streams_per_rdv_circuit
   * limit. Specified by HiddenServiceMaxStreamsCloseCircuit option. */
  unsigned int max_streams_close_circuit : 1;

  /** How many introduction points this service has. Specified by
   * HiddenServiceNumIntroductionPoints option. */
  unsigned int num_intro_points;

  /** True iff the client auth is enabled. */
  unsigned int is_client_auth_enabled : 1;

  /** List of hs_service_authorized_client_t's of clients that may access this
   * service. Specified by HiddenServiceAuthorizeClient option. */
  smartlist_t *clients;

  /** True iff we allow request made on unknown ports. Specified by
   * HiddenServiceAllowUnknownPorts option. */
  unsigned int allow_unknown_ports : 1;

  /** If true, this service is a Single Onion Service. Specified by
   * HiddenServiceSingleHopMode and HiddenServiceNonAnonymousMode options. */
  unsigned int is_single_onion : 1;

  /** If true, allow group read permissions on the directory_path. Specified by
   * HiddenServiceDirGroupReadable option. */
  unsigned int dir_group_readable : 1;

  /** Is this service ephemeral? */
  unsigned int is_ephemeral : 1;

  /** Does this service export the circuit ID of its clients? */
  hs_circuit_id_protocol_t circuit_id_protocol;

  /** DoS defenses. For the ESTABLISH_INTRO cell extension. */
  unsigned int has_dos_defense_enabled : 1;
  uint32_t intro_dos_rate_per_sec;
  uint32_t intro_dos_burst_per_sec;

  /** If set, contains the Onion Balance master ed25519 public key (taken from
   * an .onion addresses) that this tor instance serves as backend. */
  smartlist_t *ob_master_pubkeys;
} hs_service_config_t;

/** Service state. */
typedef struct hs_service_state_t {
  /** The time at which we've started our retry period to build circuits. We
   * don't want to stress circuit creation so we can only retry for a certain
   * time and then after we stop and wait. */
  time_t intro_circ_retry_started_time;

  /** Number of circuit we've launched during a single retry period. This
   * should never go over MAX_INTRO_CIRCS_PER_PERIOD. */
  unsigned int num_intro_circ_launched;

  /** Replay cache tracking the REND_COOKIE found in INTRODUCE2 cell to detect
   * repeats. Clients may send INTRODUCE1 cells for the same rendezvous point
   * through two or more different introduction points; when they do, this
   * keeps us from launching multiple simultaneous attempts to connect to the
   * same rend point. */
  replaycache_t *replay_cache_rend_cookie;

  /** When is the next time we should rotate our descriptors. This is has to be
   * done at the start time of the next SRV protocol run. */
  time_t next_rotation_time;

  /* If this is an onionbalance instance, this is an array of subcredentials
   * that should be used when decrypting an INTRO2 cell. If this is not an
   * onionbalance instance, this is NULL.
   * See [ONIONBALANCE] section in rend-spec-v3.txt for more details . */
  hs_subcredential_t *ob_subcreds;
  /* Number of OB subcredentials */
  size_t n_ob_subcreds;
} hs_service_state_t;

/** Representation of a service running on this tor instance. */
typedef struct hs_service_t {
  /** Onion address base32 encoded and NUL terminated. We keep it for logging
   * purposes so we don't have to build it everytime. */
  char onion_address[HS_SERVICE_ADDR_LEN_BASE32 + 1];

  /** Hashtable node: use to look up the service by its master public identity
   * key in the service global map. */
  HT_ENTRY(hs_service_t) hs_service_node;

  /** Service state which contains various flags and counters. */
  hs_service_state_t state;

  /** Key material of the service. */
  hs_service_keys_t keys;

  /** Configuration of the service. */
  hs_service_config_t config;

  /** Current descriptor. */
  hs_service_descriptor_t *desc_current;
  /** Next descriptor. */
  hs_service_descriptor_t *desc_next;
} hs_service_t;

/** For the service global hash map, we define a specific type for it which
 * will make it safe to use and specific to some controlled parameters such as
 * the hashing function and how to compare services. */
typedef HT_HEAD(hs_service_ht, hs_service_t) hs_service_ht;

/* API */

/* Global initializer and cleanup function. */
void hs_service_init(void);
void hs_service_free_all(void);

/* Service new/free functions. */
hs_service_t *hs_service_new(const or_options_t *options);
void hs_service_free_(hs_service_t *service);
/**
 * @copydoc hs_service_free_
 *
 * Additionally, set the pointer <b>s</b> to NULL.
 **/
#define hs_service_free(s) FREE_AND_NULL(hs_service_t, hs_service_free_, (s))

MOCK_DECL(unsigned int, hs_service_get_num_services,(void));
void hs_service_stage_services(const smartlist_t *service_list);
int hs_service_load_all_keys(void);
int hs_service_get_version_from_key(const hs_service_t *service);
void hs_service_lists_fnames_for_sandbox(smartlist_t *file_list,
                                         smartlist_t *dir_list);
int hs_service_set_conn_addr_port(const origin_circuit_t *circ,
                                  edge_connection_t *conn);

void hs_service_map_has_changed(void);
void hs_service_dir_info_changed(void);
void hs_service_run_scheduled_events(time_t now);
void hs_service_circuit_has_opened(origin_circuit_t *circ);
int hs_service_receive_intro_established(origin_circuit_t *circ,
                                         const uint8_t *payload,
                                         size_t payload_len);
int hs_service_receive_introduce2(origin_circuit_t *circ,
                                  const uint8_t *payload,
                                  size_t payload_len);

char *hs_service_lookup_current_desc(const ed25519_public_key_t *pk);

hs_service_add_ephemeral_status_t
hs_service_add_ephemeral(ed25519_secret_key_t *sk, smartlist_t *ports,
                         int max_streams_per_rdv_circuit,
                         int max_streams_close_circuit, char **address_out);
int hs_service_del_ephemeral(const char *address);

/* Used outside of the HS subsystem by the control port command HSPOST. */
void hs_service_upload_desc_to_dir(const char *encoded_desc,
                                   const uint8_t version,
                                   const ed25519_public_key_t *identity_pk,
                                   const ed25519_public_key_t *blinded_pk,
                                   const routerstatus_t *hsdir_rs);

hs_circuit_id_protocol_t
hs_service_exports_circuit_id(const ed25519_public_key_t *pk);

#ifdef HS_SERVICE_PRIVATE

#ifdef TOR_UNIT_TESTS
/* Useful getters for unit tests. */
STATIC unsigned int get_hs_service_map_size(void);
STATIC int get_hs_service_staging_list_size(void);
STATIC hs_service_ht *get_hs_service_map(void);
STATIC hs_service_t *get_first_service(void);
STATIC hs_service_intro_point_t *service_intro_point_find_by_ident(
                                         const hs_service_t *service,
                                         const hs_ident_circuit_t *ident);

MOCK_DECL(STATIC unsigned int, count_desc_circuit_established,
          (const hs_service_descriptor_t *desc));
#endif /* defined(TOR_UNIT_TESTS) */

/* Service accessors. */
STATIC hs_service_t *find_service(hs_service_ht *map,
                                  const ed25519_public_key_t *pk);
STATIC void remove_service(hs_service_ht *map, hs_service_t *service);
STATIC int register_service(hs_service_ht *map, hs_service_t *service);
/* Service introduction point functions. */
STATIC hs_service_intro_point_t *service_intro_point_new(const node_t *node);
STATIC void service_intro_point_free_(hs_service_intro_point_t *ip);
#define service_intro_point_free(ip)                            \
  FREE_AND_NULL(hs_service_intro_point_t,             \
                          service_intro_point_free_, (ip))
STATIC void service_intro_point_add(digest256map_t *map,
                                    hs_service_intro_point_t *ip);
STATIC void service_intro_point_remove(const hs_service_t *service,
                                       const hs_service_intro_point_t *ip);
STATIC hs_service_intro_point_t *service_intro_point_find(
                                 const hs_service_t *service,
                                 const ed25519_public_key_t *auth_key);
/* Service descriptor functions. */
STATIC hs_service_descriptor_t *service_descriptor_new(void);
STATIC hs_service_descriptor_t *service_desc_find_by_intro(
                                         const hs_service_t *service,
                                         const hs_service_intro_point_t *ip);
/* Helper functions. */
STATIC int client_filename_is_valid(const char *filename);
STATIC hs_service_authorized_client_t *
parse_authorized_client(const char *client_key_str);
STATIC void get_objects_from_ident(const hs_ident_circuit_t *ident,
                                   hs_service_t **service,
                                   hs_service_intro_point_t **ip,
                                   hs_service_descriptor_t **desc);
STATIC const node_t *
get_node_from_intro_point(const hs_service_intro_point_t *ip);
STATIC int can_service_launch_intro_circuit(hs_service_t *service,
                                            time_t now);
STATIC int intro_point_should_expire(const hs_service_intro_point_t *ip,
                                     time_t now);
STATIC void run_housekeeping_event(time_t now);
STATIC void rotate_all_descriptors(time_t now);
STATIC void build_all_descriptors(time_t now);
STATIC void update_all_descriptors_intro_points(time_t now);
STATIC void run_upload_descriptor_event(time_t now);

STATIC void service_descriptor_free_(hs_service_descriptor_t *desc);
#define service_descriptor_free(d) \
  FREE_AND_NULL(hs_service_descriptor_t, \
                           service_descriptor_free_, (d))

STATIC void
service_authorized_client_free_(hs_service_authorized_client_t *client);
#define service_authorized_client_free(c) \
  FREE_AND_NULL(hs_service_authorized_client_t, \
                           service_authorized_client_free_, (c))

STATIC int
write_address_to_file(const hs_service_t *service, const char *fname_);

STATIC void upload_descriptor_to_all(const hs_service_t *service,
                                     hs_service_descriptor_t *desc);

STATIC void service_desc_schedule_upload(hs_service_descriptor_t *desc,
                                         time_t now,
                                         int descriptor_changed);

STATIC int service_desc_hsdirs_changed(const hs_service_t *service,
                                const hs_service_descriptor_t *desc);

STATIC int service_authorized_client_config_equal(
                                         const hs_service_config_t *config1,
                                         const hs_service_config_t *config2);

STATIC void service_clear_config(hs_service_config_t *config);

#endif /* defined(HS_SERVICE_PRIVATE) */

#endif /* !defined(TOR_HS_SERVICE_H) */