[tor-commits] [tor/release-0.4.3] hs-v3: Improve accessor semantic of client cached object
asn at torproject.org
asn at torproject.org
Thu May 28 09:56:18 UTC 2020
commit 1810771799dd0b434ac2b5926297d64e383582e1
Author: David Goulet <dgoulet at torproject.org>
Date: Tue Mar 10 10:58:51 2020 -0400
hs-v3: Improve accessor semantic of client cached object
Add an inline helper function that indicates if the cached object contains a
decrypted descriptor or not.
The descriptor object is NULL if tor is unable to decrypt it (lacking client
authorization) and some actions need to be done only when we have a decrypted
object.
This improves code semantic.
Fixes #33458
Signed-off-by: David Goulet <dgoulet at torproject.org>
---
src/feature/hs/hs_cache.c | 64 ++++++++++++++++++++++++++++++++++++++---------
src/test/test_hs_client.c | 46 ++++++++++++++++++++++++++++++++++
2 files changed, 98 insertions(+), 12 deletions(-)
diff --git a/src/feature/hs/hs_cache.c b/src/feature/hs/hs_cache.c
index 9cf408ca3..44cd2505f 100644
--- a/src/feature/hs/hs_cache.c
+++ b/src/feature/hs/hs_cache.c
@@ -27,6 +27,21 @@
static int cached_client_descriptor_has_expired(time_t now,
const hs_cache_client_descriptor_t *cached_desc);
+/** Helper function: Return true iff the cache entry has a decrypted
+ * descriptor.
+ *
+ * A NULL desc object in the entry means that we were not able to decrypt the
+ * descriptor because we are likely lacking client authorization. It is still
+ * a valid entry but some operations can't be done without the decrypted
+ * descriptor thus this function MUST be used to safe guard access to the
+ * decrypted desc object. */
+static inline bool
+entry_has_decrypted_descriptor(const hs_cache_client_descriptor_t *entry)
+{
+ tor_assert(entry);
+ return (entry->desc != NULL);
+}
+
/********************** Directory HS cache ******************/
/** Directory descriptor cache. Map indexed by blinded key. */
@@ -341,8 +356,23 @@ static digest256map_t *hs_cache_client_intro_state;
static size_t
cache_get_client_entry_size(const hs_cache_client_descriptor_t *entry)
{
- return sizeof(*entry) +
- strlen(entry->encoded_desc) + hs_desc_obj_size(entry->desc);
+ size_t size = 0;
+
+ if (entry == NULL) {
+ goto end;
+ }
+ size += sizeof(*entry);
+
+ if (entry->encoded_desc) {
+ size += strlen(entry->encoded_desc);
+ }
+
+ if (entry_has_decrypted_descriptor(entry)) {
+ size += hs_desc_obj_size(entry->desc);
+ }
+
+ end:
+ return size;
}
/** Remove a given descriptor from our cache. */
@@ -659,14 +689,20 @@ cache_store_as_client(hs_cache_client_descriptor_t *client_desc)
* client authorization. */
cache_entry = lookup_v3_desc_as_client(client_desc->key.pubkey);
if (cache_entry != NULL) {
- /* Signalling an undecrypted descriptor. We'll always replace the one we
- * have with the new one just fetched. */
- if (cache_entry->desc == NULL) {
+ /* If the current or the new cache entry don't have a decrypted descriptor
+ * (missing client authorization), we always replace the current one with
+ * the new one. Reason is that we can't inspect the revision counter
+ * within the plaintext data so we blindly replace. */
+ if (!entry_has_decrypted_descriptor(cache_entry) ||
+ !entry_has_decrypted_descriptor(client_desc)) {
remove_v3_desc_as_client(cache_entry);
cache_client_desc_free(cache_entry);
goto store;
}
+ /* From this point on, we know that the decrypted descriptor is in the
+ * current entry and new object thus safe to access. */
+
/* If we have an entry in our cache that has a revision counter greater
* than the one we just fetched, discard the one we fetched. */
if (cache_entry->desc->plaintext_data.revision_counter >
@@ -740,11 +776,15 @@ cache_clean_v3_as_client(time_t now)
MAP_DEL_CURRENT(key);
entry_size = cache_get_client_entry_size(entry);
bytes_removed += entry_size;
+
/* We just removed an old descriptor. We need to close all intro circuits
- * so we don't have leftovers that can be selected while lacking a
- * descriptor. We leave the rendezvous circuits opened because they could
- * be in use. */
- hs_client_close_intro_circuits_from_desc(entry->desc);
+ * if the descriptor is decrypted so we don't have leftovers that can be
+ * selected while lacking a descriptor. Circuits are selected by intro
+ * authentication key thus we need the descriptor. We leave the rendezvous
+ * circuits opened because they could be in use. */
+ if (entry_has_decrypted_descriptor(entry)) {
+ hs_client_close_intro_circuits_from_desc(entry->desc);
+ }
/* Entry is not in the cache anymore, destroy it. */
cache_client_desc_free(entry);
/* Update our OOM. We didn't use the remove() function because we are in
@@ -793,7 +833,7 @@ hs_cache_lookup_as_client(const ed25519_public_key_t *key)
tor_assert(key);
cached_desc = lookup_v3_desc_as_client(key->pubkey);
- if (cached_desc && cached_desc->desc) {
+ if (cached_desc && entry_has_decrypted_descriptor(cached_desc)) {
return cached_desc->desc;
}
@@ -866,7 +906,7 @@ hs_cache_remove_as_client(const ed25519_public_key_t *key)
/* If we have a decrypted/decoded descriptor, attempt to close its
* introduction circuit(s). We shouldn't have circuit(s) without a
* descriptor else it will lead to a failure. */
- if (cached_desc->desc) {
+ if (entry_has_decrypted_descriptor(cached_desc)) {
hs_client_close_intro_circuits_from_desc(cached_desc->desc);
}
/* Remove and free. */
@@ -995,7 +1035,7 @@ hs_cache_client_new_auth_parse(const ed25519_public_key_t *service_pk)
}
cached_desc = lookup_v3_desc_as_client(service_pk->pubkey);
- if (cached_desc == NULL || cached_desc->desc != NULL) {
+ if (cached_desc == NULL || entry_has_decrypted_descriptor(cached_desc)) {
/* No entry for that service or the descriptor is already decoded. */
goto end;
}
diff --git a/src/test/test_hs_client.c b/src/test/test_hs_client.c
index 5f7fe9c40..bff71d264 100644
--- a/src/test/test_hs_client.c
+++ b/src/test/test_hs_client.c
@@ -965,6 +965,7 @@ test_close_intro_circuits_new_desc(void *arg)
(void) arg;
hs_init();
+ rend_cache_init();
/* This is needed because of the client cache expiration timestamp is based
* on having a consensus. See cached_client_descriptor_has_expired(). */
@@ -989,6 +990,51 @@ test_close_intro_circuits_new_desc(void *arg)
circ->purpose = CIRCUIT_PURPOSE_C_INTRODUCING;
ocirc = TO_ORIGIN_CIRCUIT(circ);
+ /* Build a descriptor _without_ client authorization and thus not
+ * decryptable. Make sure the close circuit code path is not triggered. */
+ {
+ char *desc_encoded = NULL;
+ uint8_t descriptor_cookie[HS_DESC_DESCRIPTOR_COOKIE_LEN];
+ curve25519_keypair_t client_kp;
+ hs_descriptor_t *desc = NULL;
+
+ tt_int_op(0, OP_EQ, curve25519_keypair_generate(&client_kp, 0));
+ crypto_rand((char *) descriptor_cookie, sizeof(descriptor_cookie));
+
+ desc = hs_helper_build_hs_desc_with_client_auth(descriptor_cookie,
+ &client_kp.pubkey,
+ &service_kp);
+ tt_assert(desc);
+ ret = hs_desc_encode_descriptor(desc, &service_kp, descriptor_cookie,
+ &desc_encoded);
+ tt_int_op(ret, OP_EQ, 0);
+ /* Associate descriptor intro key with the dummy circuit. */
+ const hs_desc_intro_point_t *ip =
+ smartlist_get(desc->encrypted_data.intro_points, 0);
+ tt_assert(ip);
+ ocirc->hs_ident = hs_ident_circuit_new(&service_kp.pubkey);
+ ed25519_pubkey_copy(ô->hs_ident->intro_auth_pk,
+ &ip->auth_key_cert->signed_key);
+ hs_descriptor_free(desc);
+ tt_assert(desc_encoded);
+ /* Put it in the cache. Should not be decrypted since the client
+ * authorization creds were not added to the global map. */
+ ret = hs_cache_store_as_client(desc_encoded, &service_kp.pubkey);
+ tor_free(desc_encoded);
+ tt_int_op(ret, OP_EQ, HS_DESC_DECODE_NEED_CLIENT_AUTH);
+
+ /* Clean cache with a future timestamp. It will trigger the clean up and
+ * attempt to close the circuit but only if the descriptor is decryptable.
+ * Cache object should be removed and circuit untouched. */
+ hs_cache_clean_as_client(mock_ns.valid_after + (60 * 60 * 24));
+ tt_assert(!hs_cache_lookup_as_client(&service_kp.pubkey));
+
+ /* Make sure the circuit still there. */
+ tt_assert(circuit_get_next_intro_circ(NULL, true));
+ /* Get rid of the ident, it will be replaced in the next tests. */
+ hs_ident_circuit_free(ocirc->hs_ident);
+ }
+
/* Build the first descriptor and cache it. */
{
char *encoded;
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