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Diffstat (limited to 'src/or/hs_cache.c')
| -rw-r--r-- | src/or/hs_cache.c | 398 |
1 files changed, 398 insertions, 0 deletions
diff --git a/src/or/hs_cache.c b/src/or/hs_cache.c new file mode 100644 index 0000000000..43cd8c3258 --- /dev/null +++ b/src/or/hs_cache.c @@ -0,0 +1,398 @@ +/* Copyright (c) 2016, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file hs_cache.c + * \brief Handle hidden service descriptor caches. + **/ + +/* For unit tests.*/ +#define HS_CACHE_PRIVATE + +#include "hs_cache.h" + +#include "or.h" +#include "config.h" +#include "hs_common.h" +#include "hs_descriptor.h" +#include "networkstatus.h" +#include "rendcache.h" + +/* Directory descriptor cache. Map indexed by blinded key. */ +static digest256map_t *hs_cache_v3_dir; + +/* Remove a given descriptor from our cache. */ +static void +remove_v3_desc_as_dir(const hs_cache_dir_descriptor_t *desc) +{ + tor_assert(desc); + digest256map_remove(hs_cache_v3_dir, desc->key); +} + +/* Store a given descriptor in our cache. */ +static void +store_v3_desc_as_dir(hs_cache_dir_descriptor_t *desc) +{ + tor_assert(desc); + digest256map_set(hs_cache_v3_dir, desc->key, desc); +} + +/* Query our cache and return the entry or NULL if not found. */ +static hs_cache_dir_descriptor_t * +lookup_v3_desc_as_dir(const uint8_t *key) +{ + tor_assert(key); + return digest256map_get(hs_cache_v3_dir, key); +} + +/* Free a directory descriptor object. */ +static void +cache_dir_desc_free(hs_cache_dir_descriptor_t *desc) +{ + if (desc == NULL) { + return; + } + hs_desc_plaintext_data_free(desc->plaintext_data); + tor_free(desc->encoded_desc); + tor_free(desc); +} + +/* Helper function: Use by the free all function using the digest256map + * interface to cache entries. */ +static void +cache_dir_desc_free_(void *ptr) +{ + hs_cache_dir_descriptor_t *desc = ptr; + cache_dir_desc_free(desc); +} + +/* Create a new directory cache descriptor object from a encoded descriptor. + * On success, return the heap-allocated cache object, otherwise return NULL if + * we can't decode the descriptor. */ +static hs_cache_dir_descriptor_t * +cache_dir_desc_new(const char *desc) +{ + hs_cache_dir_descriptor_t *dir_desc; + + tor_assert(desc); + + dir_desc = tor_malloc_zero(sizeof(hs_cache_dir_descriptor_t)); + dir_desc->plaintext_data = + tor_malloc_zero(sizeof(hs_desc_plaintext_data_t)); + dir_desc->encoded_desc = tor_strdup(desc); + + if (hs_desc_decode_plaintext(desc, dir_desc->plaintext_data) < 0) { + log_debug(LD_DIR, "Unable to decode descriptor. Rejecting."); + goto err; + } + + /* The blinded pubkey is the indexed key. */ + dir_desc->key = dir_desc->plaintext_data->blinded_pubkey.pubkey; + dir_desc->created_ts = time(NULL); + return dir_desc; + + err: + cache_dir_desc_free(dir_desc); + return NULL; +} + +/* Return the size of a cache entry in bytes. */ +static size_t +cache_get_entry_size(const hs_cache_dir_descriptor_t *entry) +{ + return (sizeof(*entry) + hs_desc_plaintext_obj_size(entry->plaintext_data) + + strlen(entry->encoded_desc)); +} + +/* Try to store a valid version 3 descriptor in the directory cache. Return 0 + * on success else a negative value is returned indicating that we have a + * newer version in our cache. On error, caller is responsible to free the + * given descriptor desc. */ +static int +cache_store_v3_as_dir(hs_cache_dir_descriptor_t *desc) +{ + hs_cache_dir_descriptor_t *cache_entry; + + tor_assert(desc); + + /* Verify if we have an entry in the cache for that key and if yes, check + * if we should replace it? */ + cache_entry = lookup_v3_desc_as_dir(desc->key); + if (cache_entry != NULL) { + /* Only replace descriptor if revision-counter is greater than the one + * in our cache */ + if (cache_entry->plaintext_data->revision_counter >= + desc->plaintext_data->revision_counter) { + log_info(LD_REND, "Descriptor revision counter in our cache is " + "greater or equal than the one we received. " + "Rejecting!"); + goto err; + } + /* We now know that the descriptor we just received is a new one so + * remove the entry we currently have from our cache so we can then + * store the new one. */ + remove_v3_desc_as_dir(cache_entry); + rend_cache_decrement_allocation(cache_get_entry_size(cache_entry)); + cache_dir_desc_free(cache_entry); + } + /* Store the descriptor we just got. We are sure here that either we + * don't have the entry or we have a newer descriptor and the old one + * has been removed from the cache. */ + store_v3_desc_as_dir(desc); + + /* Update our total cache size with this entry for the OOM. This uses the + * old HS protocol cache subsystem for which we are tied with. */ + rend_cache_increment_allocation(cache_get_entry_size(desc)); + + /* XXX: Update HS statistics. We should have specific stats for v3. */ + + return 0; + + err: + return -1; +} + +/* Using the query which is the base64 encoded blinded key of a version 3 + * descriptor, lookup in our directory cache the entry. If found, 1 is + * returned and desc_out is populated with a newly allocated string being the + * encoded descriptor. If not found, 0 is returned and desc_out is untouched. + * On error, a negative value is returned and desc_out is untouched. */ +static int +cache_lookup_v3_as_dir(const char *query, const char **desc_out) +{ + int found = 0; + ed25519_public_key_t blinded_key; + const hs_cache_dir_descriptor_t *entry; + + tor_assert(query); + + /* Decode blinded key using the given query value. */ + if (ed25519_public_from_base64(&blinded_key, query) < 0) { + log_info(LD_REND, "Unable to decode the v3 HSDir query %s.", + safe_str_client(query)); + goto err; + } + + entry = lookup_v3_desc_as_dir(blinded_key.pubkey); + if (entry != NULL) { + found = 1; + if (desc_out) { + *desc_out = entry->encoded_desc; + } + } + + return found; + + err: + return -1; +} + +/* Clean the v3 cache by removing any entry that has expired using the + * <b>global_cutoff</b> value. If <b>global_cutoff</b> is 0, the cleaning + * process will use the lifetime found in the plaintext data section. Return + * the number of bytes cleaned. */ +STATIC size_t +cache_clean_v3_as_dir(time_t now, time_t global_cutoff) +{ + size_t bytes_removed = 0; + + /* Code flow error if this ever happens. */ + tor_assert(global_cutoff >= 0); + + if (!hs_cache_v3_dir) { /* No cache to clean. Just return. */ + return 0; + } + + DIGEST256MAP_FOREACH_MODIFY(hs_cache_v3_dir, key, + hs_cache_dir_descriptor_t *, entry) { + size_t entry_size; + time_t cutoff = global_cutoff; + if (!cutoff) { + /* Cutoff is the lifetime of the entry found in the descriptor. */ + cutoff = now - entry->plaintext_data->lifetime_sec; + } + + /* If the entry has been created _after_ the cutoff, not expired so + * continue to the next entry in our v3 cache. */ + if (entry->created_ts > cutoff) { + continue; + } + /* Here, our entry has expired, remove and free. */ + MAP_DEL_CURRENT(key); + entry_size = cache_get_entry_size(entry); + bytes_removed += entry_size; + /* Entry is not in the cache anymore, destroy it. */ + cache_dir_desc_free(entry); + /* Update our cache entry allocation size for the OOM. */ + rend_cache_decrement_allocation(entry_size); + /* Logging. */ + { + char key_b64[BASE64_DIGEST256_LEN + 1]; + base64_encode(key_b64, sizeof(key_b64), (const char *) key, + DIGEST256_LEN, 0); + log_info(LD_REND, "Removing v3 descriptor '%s' from HSDir cache", + safe_str_client(key_b64)); + } + } DIGEST256MAP_FOREACH_END; + + return bytes_removed; +} + +/* Given an encoded descriptor, store it in the directory cache depending on + * which version it is. Return a negative value on error. On success, 0 is + * returned. */ +int +hs_cache_store_as_dir(const char *desc) +{ + hs_cache_dir_descriptor_t *dir_desc = NULL; + + tor_assert(desc); + + /* Create a new cache object. This can fail if the descriptor plaintext data + * is unparseable which in this case a log message will be triggered. */ + dir_desc = cache_dir_desc_new(desc); + if (dir_desc == NULL) { + goto err; + } + + /* Call the right function against the descriptor version. At this point, + * we are sure that the descriptor's version is supported else the + * decoding would have failed. */ + switch (dir_desc->plaintext_data->version) { + case HS_VERSION_THREE: + default: + if (cache_store_v3_as_dir(dir_desc) < 0) { + goto err; + } + break; + } + return 0; + + err: + cache_dir_desc_free(dir_desc); + return -1; +} + +/* Using the query, lookup in our directory cache the entry. If found, 1 is + * returned and desc_out is populated with a newly allocated string being + * the encoded descriptor. If not found, 0 is returned and desc_out is + * untouched. On error, a negative value is returned and desc_out is + * untouched. */ +int +hs_cache_lookup_as_dir(uint32_t version, const char *query, + const char **desc_out) +{ + int found; + + tor_assert(query); + /* This should never be called with an unsupported version. */ + tor_assert(hs_desc_is_supported_version(version)); + + switch (version) { + case HS_VERSION_THREE: + default: + found = cache_lookup_v3_as_dir(query, desc_out); + break; + } + + return found; +} + +/* Clean all directory caches using the current time now. */ +void +hs_cache_clean_as_dir(time_t now) +{ + time_t cutoff; + + /* Start with v2 cache cleaning. */ + cutoff = now - rend_cache_max_entry_lifetime(); + rend_cache_clean_v2_descs_as_dir(cutoff); + + /* Now, clean the v3 cache. Set the cutoff to 0 telling the cleanup function + * to compute the cutoff by itself using the lifetime value. */ + cache_clean_v3_as_dir(now, 0); +} + +/* Do a round of OOM cleanup on all directory caches. Return the amount of + * removed bytes. It is possible that the returned value is lower than + * min_remove_bytes if the caches get emptied out so the caller should be + * aware of this. */ +size_t +hs_cache_handle_oom(time_t now, size_t min_remove_bytes) +{ + time_t k; + size_t bytes_removed = 0; + + /* Our OOM handler called with 0 bytes to remove is a code flow error. */ + tor_assert(min_remove_bytes != 0); + + /* The algorithm is as follow. K is the oldest expected descriptor age. + * + * 1) Deallocate all entries from v2 cache that are older than K hours. + * 1.1) If the amount of remove bytes has been reached, stop. + * 2) Deallocate all entries from v3 cache that are older than K hours + * 2.1) If the amount of remove bytes has been reached, stop. + * 3) Set K = K - RendPostPeriod and repeat process until K is < 0. + * + * This ends up being O(Kn). + */ + + /* Set K to the oldest expected age in seconds which is the maximum + * lifetime of a cache entry. We'll use the v2 lifetime because it's much + * bigger than the v3 thus leading to cleaning older descriptors. */ + k = rend_cache_max_entry_lifetime(); + + do { + time_t cutoff; + + /* If K becomes negative, it means we've empty the caches so stop and + * return what we were able to cleanup. */ + if (k < 0) { + break; + } + /* Compute a cutoff value with K and the current time. */ + cutoff = now - k; + + /* Start by cleaning the v2 cache with that cutoff. */ + bytes_removed += rend_cache_clean_v2_descs_as_dir(cutoff); + + if (bytes_removed < min_remove_bytes) { + /* We haven't remove enough bytes so clean v3 cache. */ + bytes_removed += cache_clean_v3_as_dir(now, cutoff); + /* Decrement K by a post period to shorten the cutoff. */ + k -= get_options()->RendPostPeriod; + } + } while (bytes_removed < min_remove_bytes); + + return bytes_removed; +} + +/** + * Return the maximum size of an HS descriptor we are willing to accept as an + * HSDir. + */ +unsigned int +hs_cache_get_max_descriptor_size(void) +{ + return (unsigned) networkstatus_get_param(NULL, + "HSV3MaxDescriptorSize", + HS_DESC_MAX_LEN, 1, INT32_MAX); +} + +/* Initialize the hidden service cache subsystem. */ +void +hs_cache_init(void) +{ + /* Calling this twice is very wrong code flow. */ + tor_assert(!hs_cache_v3_dir); + hs_cache_v3_dir = digest256map_new(); +} + +/* Cleanup the hidden service cache subsystem. */ +void +hs_cache_free_all(void) +{ + digest256map_free(hs_cache_v3_dir, cache_dir_desc_free_); + hs_cache_v3_dir = NULL; +} + |