diff options
Diffstat (limited to 'src/feature/hs/hs_ob.c')
| -rw-r--r-- | src/feature/hs/hs_ob.c | 408 |
1 files changed, 408 insertions, 0 deletions
diff --git a/src/feature/hs/hs_ob.c b/src/feature/hs/hs_ob.c new file mode 100644 index 0000000000..c18a789013 --- /dev/null +++ b/src/feature/hs/hs_ob.c @@ -0,0 +1,408 @@ +/* Copyright (c) 2017-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file hs_ob.c + * \brief Implement Onion Balance specific code. + **/ + +#define HS_OB_PRIVATE + +#include "feature/hs/hs_service.h" + +#include "feature/nodelist/networkstatus.h" +#include "feature/nodelist/networkstatus_st.h" + +#include "lib/confmgt/confmgt.h" +#include "lib/encoding/confline.h" + +#include "hs_ob.h" + +/* Options config magic number. */ +#define OB_OPTIONS_MAGIC 0x631DE7EA + +/* Helper macros. */ +#define VAR(varname, conftype, member, initvalue) \ + CONFIG_VAR_ETYPE(ob_options_t, varname, conftype, member, 0, initvalue) +#define V(member,conftype,initvalue) \ + VAR(#member, conftype, member, initvalue) + +/* Dummy instance of ob_options_t, used for type-checking its members with + * CONF_CHECK_VAR_TYPE. */ +DUMMY_TYPECHECK_INSTANCE(ob_options_t); + +/* Array of variables for the config file options. */ +static const config_var_t config_vars[] = { + V(MasterOnionAddress, LINELIST, NULL), + + END_OF_CONFIG_VARS +}; + +/* "Extra" variable in the state that receives lines we can't parse. This + * lets us preserve options from versions of Tor newer than us. */ +static const struct_member_t config_extra_vars = { + .name = "__extra", + .type = CONFIG_TYPE_LINELIST, + .offset = offsetof(ob_options_t, ExtraLines), +}; + +/* Configuration format of ob_options_t. */ +static const config_format_t config_format = { + .size = sizeof(ob_options_t), + .magic = { + "ob_options_t", + OB_OPTIONS_MAGIC, + offsetof(ob_options_t, magic_), + }, + .vars = config_vars, + .extra = &config_extra_vars, +}; + +/* Global configuration manager for the config file. */ +static config_mgr_t *config_options_mgr = NULL; + +/* Return the configuration manager for the config file. */ +static const config_mgr_t * +get_config_options_mgr(void) +{ + if (PREDICT_UNLIKELY(config_options_mgr == NULL)) { + config_options_mgr = config_mgr_new(&config_format); + config_mgr_freeze(config_options_mgr); + } + return config_options_mgr; +} + +#define ob_option_free(val) \ + FREE_AND_NULL(ob_options_t, ob_option_free_, (val)) + +/** Helper: Free a config options object. */ +static void +ob_option_free_(ob_options_t *opts) +{ + if (opts == NULL) { + return; + } + config_free(get_config_options_mgr(), opts); +} + +/** Return an allocated config options object. */ +static ob_options_t * +ob_option_new(void) +{ + ob_options_t *opts = config_new(get_config_options_mgr()); + config_init(get_config_options_mgr(), opts); + return opts; +} + +/** Helper function: From the configuration line value which is an onion + * address with the ".onion" extension, find the public key and put it in + * pkey_out. + * + * On success, true is returned. Else, false and pkey is untouched. */ +static bool +get_onion_public_key(const char *value, ed25519_public_key_t *pkey_out) +{ + char address[HS_SERVICE_ADDR_LEN_BASE32 + 1]; + + tor_assert(value); + tor_assert(pkey_out); + + if (strcmpend(value, ".onion")) { + /* Not a .onion extension, bad format. */ + return false; + } + + /* Length validation. The -1 is because sizeof() counts the NUL byte. */ + if (strlen(value) > + (HS_SERVICE_ADDR_LEN_BASE32 + sizeof(".onion") - 1)) { + /* Too long, bad format. */ + return false; + } + + /* We don't want the .onion so we add 2 because size - 1 is copied with + * strlcpy() in order to accomodate the NUL byte and sizeof() counts the NUL + * byte so we need to remove them from the equation. */ + strlcpy(address, value, strlen(value) - sizeof(".onion") + 2); + + if (hs_parse_address_no_log(address, pkey_out, NULL, NULL, NULL) < 0) { + return false; + } + + /* Success. */ + return true; +} + +/** Parse the given ob options in opts and set the service config object + * accordingly. + * + * Return 1 on success else 0. */ +static int +ob_option_parse(hs_service_config_t *config, const ob_options_t *opts) +{ + int ret = 0; + config_line_t *line; + + tor_assert(config); + tor_assert(opts); + + for (line = opts->MasterOnionAddress; line; line = line->next) { + /* Allocate config list if need be. */ + if (!config->ob_master_pubkeys) { + config->ob_master_pubkeys = smartlist_new(); + } + ed25519_public_key_t *pubkey = tor_malloc_zero(sizeof(*pubkey)); + + if (!get_onion_public_key(line->value, pubkey)) { + log_warn(LD_REND, "OnionBalance: MasterOnionAddress %s is invalid", + line->value); + tor_free(pubkey); + goto end; + } + smartlist_add(config->ob_master_pubkeys, pubkey); + log_info(LD_REND, "OnionBalance: MasterOnionAddress %s registered", + line->value); + } + /* Success. */ + ret = 1; + + end: + /* No keys added, we free the list since no list means no onion balance + * support for this tor instance. */ + if (smartlist_len(config->ob_master_pubkeys) == 0) { + smartlist_free(config->ob_master_pubkeys); + } + return ret; +} + +/** For the given master public key and time period, compute the subcredential + * and put them into subcredential. The subcredential parameter needs to be at + * least DIGEST256_LEN in size. */ +static void +build_subcredential(const ed25519_public_key_t *pkey, uint64_t tp, + hs_subcredential_t *subcredential) +{ + ed25519_public_key_t blinded_pubkey; + + tor_assert(pkey); + tor_assert(subcredential); + + hs_build_blinded_pubkey(pkey, NULL, 0, tp, &blinded_pubkey); + hs_get_subcredential(pkey, &blinded_pubkey, subcredential); +} + +/* + * Public API. + */ + +/** Return true iff the given service is configured as an onion balance + * instance. To satisfy that condition, there must at least be one master + * ed25519 public key configured. */ +bool +hs_ob_service_is_instance(const hs_service_t *service) +{ + if (BUG(service == NULL)) { + return false; + } + + /* No list, we are not an instance. */ + if (!service->config.ob_master_pubkeys) { + return false; + } + + return smartlist_len(service->config.ob_master_pubkeys) > 0; +} + +/** Read and parse the config file at fname on disk. The service config object + * is populated with the options if any. + * + * Return 1 on success else 0. This is to follow the "ok" convention in + * hs_config.c. */ +int +hs_ob_parse_config_file(hs_service_config_t *config) +{ + static const char *fname = "ob_config"; + int ret = 0; + char *content = NULL, *errmsg = NULL, *config_file_path = NULL; + ob_options_t *options = NULL; + config_line_t *lines = NULL; + + tor_assert(config); + + /* Read file from disk. */ + config_file_path = hs_path_from_filename(config->directory_path, fname); + content = read_file_to_str(config_file_path, 0, NULL); + if (!content) { + log_warn(LD_FS, "OnionBalance: Unable to read config file %s", + escaped(config_file_path)); + goto end; + } + + /* Parse lines. */ + if (config_get_lines(content, &lines, 0) < 0) { + goto end; + } + + options = ob_option_new(); + config_assign(get_config_options_mgr(), options, lines, 0, &errmsg); + if (errmsg) { + log_warn(LD_REND, "OnionBalance: Unable to parse config file: %s", + errmsg); + tor_free(errmsg); + goto end; + } + + /* Parse the options and set the service config object with the details. */ + ret = ob_option_parse(config, options); + + end: + config_free_lines(lines); + ob_option_free(options); + tor_free(content); + tor_free(config_file_path); + return ret; +} + +/** Compute all possible subcredentials for every onion master key in the given + * service config object. subcredentials_out is allocated and set as an + * continous array containing all possible values. + * + * On success, return the number of subcredential put in the array which will + * correspond to an arry of size: n * DIGEST256_LEN where DIGEST256_LEN is the + * length of a single subcredential. + * + * If the given configuration object has no OB master keys configured, 0 is + * returned and subcredentials_out is set to NULL. + * + * Otherwise, this can't fail. */ +STATIC size_t +compute_subcredentials(const hs_service_t *service, + hs_subcredential_t **subcredentials_out) +{ + unsigned int num_pkeys, idx = 0; + hs_subcredential_t *subcreds = NULL; + const int steps[3] = {0, -1, 1}; + const unsigned int num_steps = ARRAY_LENGTH(steps); + const uint64_t tp = hs_get_time_period_num(0); + + tor_assert(service); + tor_assert(subcredentials_out); + /* Our caller has checked these too */ + tor_assert(service->desc_current); + tor_assert(service->desc_next); + + /* Make sure we are an OB instance, or bail out. */ + num_pkeys = smartlist_len(service->config.ob_master_pubkeys); + if (!num_pkeys) { + *subcredentials_out = NULL; + return 0; + } + + /* Time to build all the subcredentials for each time period: two for each + * instance descriptor plus three for the onionbalance frontend service: the + * previous one (-1), the current one (0) and the next one (1) for each + * configured key in order to accomodate client and service consensus skew. + * + * If the client consensus after_time is at 23:00 but the service one is at + * 01:00, the client will be using the previous time period where the + * service will think it is the client next time period. Thus why we have + * to try them all. + * + * The normal use case works because the service gets the descriptor object + * that corresponds to the intro point's request, and because each + * descriptor corresponds to a specific subcredential, we get the right + * subcredential out of it, and use that to do the decryption. + * + * As a slight optimization, statistically, the current time period (0) will + * be the one to work first so we'll put them first in the array to maximize + * our chance of success. */ + + /* We use a flat array, not a smartlist_t, in order to minimize memory + * allocation. + * + * Size of array is: length of a single subcredential multiplied by the + * number of time period we need to compute and finally multiplied by the + * total number of keys we are about to process. In other words, for each + * key, we allocate 3 subcredential slots. Then in the end we also add two + * subcredentials for this instance's active descriptors. */ + subcreds = + tor_calloc((num_steps * num_pkeys) + 2, sizeof(hs_subcredential_t)); + + /* For each master pubkey we add 3 subcredentials: */ + for (unsigned int i = 0; i < num_steps; i++) { + SMARTLIST_FOREACH_BEGIN(service->config.ob_master_pubkeys, + const ed25519_public_key_t *, pkey) { + build_subcredential(pkey, tp + steps[i], &subcreds[idx]); + idx++; + } SMARTLIST_FOREACH_END(pkey); + } + + /* And then in the end we add the two subcredentials of the current active + * instance descriptors */ + memcpy(&subcreds[idx++], &service->desc_current->desc->subcredential, + sizeof(hs_subcredential_t)); + memcpy(&subcreds[idx++], &service->desc_next->desc->subcredential, + sizeof(hs_subcredential_t)); + + log_info(LD_REND, "Refreshing %u onionbalance keys (TP #%d).", + idx, (int)tp); + + *subcredentials_out = subcreds; + return idx; +} + +/** + * If we are an Onionbalance instance, refresh our keys. + * + * If we are not an Onionbalance instance or we are not ready to do so, this + * is a NOP. + * + * This function is called everytime we build a new descriptor. That's because + * we want our Onionbalance keys to always use up-to-date subcredentials both + * for the instance (ourselves) and for the onionbalance frontend. + */ +void +hs_ob_refresh_keys(hs_service_t *service) +{ + hs_subcredential_t *ob_subcreds = NULL; + size_t num_subcreds; + + tor_assert(service); + + /* Don't do any of this if we are not configured as an OB instance */ + if (!hs_ob_service_is_instance(service)) { + return; + } + + /* We need both service descriptors created to make onionbalance keys. + * + * That's because we fetch our own (the instance's) subcredentials from our + * own descriptors which should always include the latest subcredentials that + * clients would use. + * + * This function is called with each descriptor build, so we will be + * eventually be called when both descriptors are created. */ + if (!service->desc_current || !service->desc_next) { + return; + } + + /* Get a new set of subcreds */ + num_subcreds = compute_subcredentials(service, &ob_subcreds); + if (BUG(!num_subcreds)) { + return; + } + + /* Delete old subcredentials if any */ + if (service->ob_subcreds) { + tor_free(service->ob_subcreds); + } + + service->ob_subcreds = ob_subcreds; + service->n_ob_subcreds = num_subcreds; +} + +/** Free any memory allocated by the onionblance subsystem. */ +void +hs_ob_free_all(void) +{ + config_mgr_free(config_options_mgr); +} |