[tor-commits] [tor/master] When OOM, free cached hidden service descriptors too.
nickm at torproject.org
nickm at torproject.org
Mon Jan 12 18:59:57 UTC 2015
commit 3033ba9f5ec8eb4dea3e6778f6d7546cacf7ae57
Author: Nick Mathewson <nickm at torproject.org>
Date: Sun Jan 4 20:05:29 2015 -0500
When OOM, free cached hidden service descriptors too.
---
changes/bug13806 | 8 ++++
src/or/main.c | 2 +-
src/or/or.h | 2 +
src/or/relay.c | 12 +++++
src/or/rendcommon.c | 121 ++++++++++++++++++++++++++++++++++++++++++---------
src/or/rendcommon.h | 4 +-
6 files changed, 126 insertions(+), 23 deletions(-)
diff --git a/changes/bug13806 b/changes/bug13806
new file mode 100644
index 0000000..0a6b268
--- /dev/null
+++ b/changes/bug13806
@@ -0,0 +1,8 @@
+ o Minor features (DOS resistance):
+ - Count the total number of bytes used storing hidden service descriptors
+ against the value of MaxMemInQueues. If we're low on memory, and more
+ than 20% of our memory is used holding hidden service descriptors, free
+ them until no more than 10% of our memory holds hidden service
+ descriptors. Free the least recently fetched descriptors first.
+ Resolves ticket 13806.
+
diff --git a/src/or/main.c b/src/or/main.c
index 58e3ad3..3ee9644 100644
--- a/src/or/main.c
+++ b/src/or/main.c
@@ -1437,7 +1437,7 @@ run_scheduled_events(time_t now)
if (time_to_clean_caches < now) {
rep_history_clean(now - options->RephistTrackTime);
rend_cache_clean(now);
- rend_cache_clean_v2_descs_as_dir(now);
+ rend_cache_clean_v2_descs_as_dir(now, 0);
microdesc_cache_rebuild(NULL, 0);
#define CLEAN_CACHES_INTERVAL (30*60)
time_to_clean_caches = now + CLEAN_CACHES_INTERVAL;
diff --git a/src/or/or.h b/src/or/or.h
index ee86697..d978719 100644
--- a/src/or/or.h
+++ b/src/or/or.h
@@ -4939,6 +4939,8 @@ typedef struct rend_service_descriptor_t {
typedef struct rend_cache_entry_t {
size_t len; /**< Length of <b>desc</b> */
time_t received; /**< When was the descriptor received? */
+ time_t last_served; /**< When did we last write this one to somebody?
+ * (HSDir only) */
char *desc; /**< Service descriptor */
rend_service_descriptor_t *parsed; /**< Parsed value of 'desc' */
} rend_cache_entry_t;
diff --git a/src/or/relay.c b/src/or/relay.c
index b95e584..50070b7 100644
--- a/src/or/relay.c
+++ b/src/or/relay.c
@@ -2441,7 +2441,19 @@ cell_queues_check_size(void)
size_t alloc = cell_queues_get_total_allocation();
alloc += buf_get_total_allocation();
alloc += tor_zlib_get_total_allocation();
+ const size_t rend_cache_total = rend_cache_get_total_allocation();
+ alloc += rend_cache_total;
if (alloc >= get_options()->MaxMemInQueues) {
+ /* If we're spending over 20% of the memory limit on hidden service
+ * descriptors, free them until we're down to 10%.
+ */
+ if (rend_cache_total > get_options()->MaxMemInQueues / 5) {
+ const size_t bytes_to_remove =
+ rend_cache_total - (get_options()->MaxMemInQueues / 10);
+ rend_cache_clean_v2_descs_as_dir(time(NULL), bytes_to_remove);
+ alloc -= rend_cache_total;
+ alloc += rend_cache_get_total_allocation();
+ }
circuits_handle_oom(alloc);
return 1;
}
diff --git a/src/or/rendcommon.c b/src/or/rendcommon.c
index e779ecf..d85e323 100644
--- a/src/or/rendcommon.c
+++ b/src/or/rendcommon.c
@@ -704,6 +704,9 @@ static strmap_t *rend_cache = NULL;
* directories. */
static digestmap_t *rend_cache_v2_dir = NULL;
+/** DOCDOC */
+static size_t rend_cache_total_allocation = 0;
+
/** Initializes the service descriptor cache.
*/
void
@@ -713,12 +716,64 @@ rend_cache_init(void)
rend_cache_v2_dir = digestmap_new();
}
+/** Return the approximate number of bytes needed to hold <b>e</b>. */
+static size_t
+rend_cache_entry_allocation(const rend_cache_entry_t *e)
+{
+ if (!e)
+ return 0;
+
+ /* This doesn't count intro_nodes or key size */
+ return sizeof(*e) + e->len + sizeof(*e->parsed);
+}
+
+/** DOCDOC */
+size_t
+rend_cache_get_total_allocation(void)
+{
+ return rend_cache_total_allocation;
+}
+
+/** Decrement the total bytes attributed to the rendezvous cache by n. */
+static void
+rend_cache_decrement_allocation(size_t n)
+{
+ static int have_underflowed = 0;
+
+ if (rend_cache_total_allocation >= n) {
+ rend_cache_total_allocation -= n;
+ } else {
+ rend_cache_total_allocation = 0;
+ if (! have_underflowed) {
+ have_underflowed = 1;
+ log_warn(LD_BUG, "Underflow in rend_cache_decrement_allocation");
+ }
+ }
+}
+
+/** Increase the total bytes attributed to the rendezvous cache by n. */
+static void
+rend_cache_increment_allocation(size_t n)
+{
+ static int have_overflowed = 0;
+ if (rend_cache_total_allocation <= SIZE_MAX - n) {
+ rend_cache_total_allocation += n;
+ } else {
+ rend_cache_total_allocation = SIZE_MAX;
+ if (! have_overflowed) {
+ have_overflowed = 1;
+ log_warn(LD_BUG, "Overflow in rend_cache_increment_allocation");
+ }
+ }
+}
+
/** Helper: free storage held by a single service descriptor cache entry. */
static void
rend_cache_entry_free(rend_cache_entry_t *e)
{
if (!e)
return;
+ rend_cache_decrement_allocation(rend_cache_entry_allocation(e));
rend_service_descriptor_free(e->parsed);
tor_free(e->desc);
tor_free(e);
@@ -740,6 +795,7 @@ rend_cache_free_all(void)
digestmap_free(rend_cache_v2_dir, rend_cache_entry_free_);
rend_cache = NULL;
rend_cache_v2_dir = NULL;
+ rend_cache_total_allocation = 0;
}
/** Removes all old entries from the service descriptor cache.
@@ -777,31 +833,46 @@ rend_cache_purge(void)
}
/** Remove all old v2 descriptors and those for which this hidden service
- * directory is not responsible for any more. */
+ * directory is not responsible for any more.
+ *
+ * If at all possible, remove at least <b>force_remove</b> bytes of data.
+ */
void
-rend_cache_clean_v2_descs_as_dir(time_t now)
+rend_cache_clean_v2_descs_as_dir(time_t now, size_t force_remove)
{
digestmap_iter_t *iter;
time_t cutoff = now - REND_CACHE_MAX_AGE - REND_CACHE_MAX_SKEW;
- for (iter = digestmap_iter_init(rend_cache_v2_dir);
- !digestmap_iter_done(iter); ) {
- const char *key;
- void *val;
- rend_cache_entry_t *ent;
- digestmap_iter_get(iter, &key, &val);
- ent = val;
- if (ent->parsed->timestamp < cutoff ||
- !hid_serv_responsible_for_desc_id(key)) {
- char key_base32[REND_DESC_ID_V2_LEN_BASE32 + 1];
- base32_encode(key_base32, sizeof(key_base32), key, DIGEST_LEN);
- log_info(LD_REND, "Removing descriptor with ID '%s' from cache",
- safe_str_client(key_base32));
- iter = digestmap_iter_next_rmv(rend_cache_v2_dir, iter);
- rend_cache_entry_free(ent);
- } else {
- iter = digestmap_iter_next(rend_cache_v2_dir, iter);
+ const int LAST_SERVED_CUTOFF_STEP = 1800;
+ time_t last_served_cutoff = cutoff;
+ size_t bytes_removed = 0;
+ do {
+ for (iter = digestmap_iter_init(rend_cache_v2_dir);
+ !digestmap_iter_done(iter); ) {
+ const char *key;
+ void *val;
+ rend_cache_entry_t *ent;
+ digestmap_iter_get(iter, &key, &val);
+ ent = val;
+ if (ent->parsed->timestamp < cutoff ||
+ ent->last_served < last_served_cutoff ||
+ !hid_serv_responsible_for_desc_id(key)) {
+ char key_base32[REND_DESC_ID_V2_LEN_BASE32 + 1];
+ base32_encode(key_base32, sizeof(key_base32), key, DIGEST_LEN);
+ log_info(LD_REND, "Removing descriptor with ID '%s' from cache",
+ safe_str_client(key_base32));
+ bytes_removed += rend_cache_entry_allocation(ent);
+ iter = digestmap_iter_next_rmv(rend_cache_v2_dir, iter);
+ rend_cache_entry_free(ent);
+ } else {
+ iter = digestmap_iter_next(rend_cache_v2_dir, iter);
+ }
}
- }
+
+ /* In case we didn't remove enough bytes, advance the cutoff a little. */
+ last_served_cutoff += LAST_SERVED_CUTOFF_STEP;
+ if (last_served_cutoff > now)
+ break;
+ } while (bytes_removed < force_remove);
}
/** Determines whether <b>a</b> is in the interval of <b>b</b> (excluded) and
@@ -903,6 +974,7 @@ rend_cache_lookup_v2_desc_as_dir(const char *desc_id, const char **desc)
e = digestmap_get(rend_cache_v2_dir, desc_id_digest);
if (e) {
*desc = e->desc;
+ e->last_served = approx_time();
return 1;
}
return 0;
@@ -993,7 +1065,13 @@ rend_cache_store_v2_desc_as_dir(const char *desc)
if (!e) {
e = tor_malloc_zero(sizeof(rend_cache_entry_t));
digestmap_set(rend_cache_v2_dir, desc_id, e);
+ /* Treat something just uploaded as having been served a little
+ * while ago, so that flooding with new descriptors doesn't help
+ * too much.
+ */
+ e->last_served = approx_time() - 3600;
} else {
+ rend_cache_decrement_allocation(rend_cache_entry_allocation(e));
rend_service_descriptor_free(e->parsed);
tor_free(e->desc);
}
@@ -1001,6 +1079,7 @@ rend_cache_store_v2_desc_as_dir(const char *desc)
e->parsed = parsed;
e->desc = tor_strndup(current_desc, encoded_size);
e->len = encoded_size;
+ rend_cache_increment_allocation(rend_cache_entry_allocation(e));
log_info(LD_REND, "Successfully stored service descriptor with desc ID "
"'%s' and len %d.",
safe_str(desc_id_base32), (int)encoded_size);
@@ -1189,6 +1268,7 @@ rend_cache_store_v2_desc_as_client(const char *desc,
e = tor_malloc_zero(sizeof(rend_cache_entry_t));
strmap_set_lc(rend_cache, key, e);
} else {
+ rend_cache_decrement_allocation(rend_cache_entry_allocation(e));
rend_service_descriptor_free(e->parsed);
tor_free(e->desc);
}
@@ -1197,6 +1277,7 @@ rend_cache_store_v2_desc_as_client(const char *desc,
e->desc = tor_malloc_zero(encoded_size + 1);
strlcpy(e->desc, desc, encoded_size + 1);
e->len = encoded_size;
+ rend_cache_increment_allocation(rend_cache_entry_allocation(e));
log_debug(LD_REND,"Successfully stored rend desc '%s', len %d.",
safe_str_client(service_id), (int)encoded_size);
return RCS_OKAY;
diff --git a/src/or/rendcommon.h b/src/or/rendcommon.h
index 186326a..1d02bb4 100644
--- a/src/or/rendcommon.h
+++ b/src/or/rendcommon.h
@@ -33,7 +33,7 @@ void rend_intro_point_free(rend_intro_point_t *intro);
void rend_cache_init(void);
void rend_cache_clean(time_t now);
-void rend_cache_clean_v2_descs_as_dir(time_t now);
+void rend_cache_clean_v2_descs_as_dir(time_t now, size_t min_to_remove);
void rend_cache_purge(void);
void rend_cache_free_all(void);
int rend_valid_service_id(const char *query);
@@ -51,7 +51,6 @@ rend_cache_store_status_t rend_cache_store_v2_desc_as_dir(const char *desc);
rend_cache_store_status_t rend_cache_store_v2_desc_as_client(const char *desc,
const char *desc_id_base32,
const rend_data_t *rend_query);
-
int rend_encode_v2_descriptors(smartlist_t *descs_out,
rend_service_descriptor_t *desc, time_t now,
uint8_t period, rend_auth_type_t auth_type,
@@ -64,6 +63,7 @@ int rend_id_is_in_interval(const char *a, const char *b, const char *c);
void rend_get_descriptor_id_bytes(char *descriptor_id_out,
const char *service_id,
const char *secret_id_part);
+size_t rend_cache_get_total_allocation(void);
#endif
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