tor

commit adcb094cb639ab8a3a36f3dc0bf1bb4e7fcdbd2b
parent 065ebd10c2baee20f2963ac7116701d9593027a8
Author: David Goulet <dgoulet@torproject.org>
Date:   Wed,  6 Oct 2021 15:45:13 -0400

Merge branch 'tor-gitlab/mr/392' into maint-0.4.5

Diffstat:
A
changes/bug40375
 | 
5
+++++
M
src/feature/control/control_getinfo.c
 | 
32
+++++++++++++++-----------------
M
src/feature/dirclient/dirclient.c
 | 
21
+++++++++++++--------

3 files changed, 33 insertions(+), 25 deletions(-)
diff --git a/changes/bug40375 b/changes/bug40375
@@ -0,0 +1,5 @@
+  o Minor bugfixes (consensus handling):
+    - Avoid a set of bugs that could be caused by inconsistently preferring
+      an out-of-date consensus stored in a stale directory cache over
+      a more recent one stored on disk as the latest consensus.
+      Fixes bug 40375; bugfix on 0.3.1.1-alpha.
diff --git a/src/feature/control/control_getinfo.c b/src/feature/control/control_getinfo.c
@@ -353,26 +353,24 @@ getinfo_helper_current_consensus(consensus_flavor_t flavor,
     *errmsg = "Internal error: unrecognized flavor name.";
     return -1;
   }
-  if (we_want_to_fetch_flavor(get_options(), flavor)) {
-    /** Check from the cache */
-    const cached_dir_t *consensus = dirserv_get_consensus(flavor_name);
-    if (consensus) {
-      *answer = tor_strdup(consensus->dir);
-    }
+  tor_mmap_t *mapped = networkstatus_map_cached_consensus(flavor_name);
+  if (mapped) {
+    *answer = tor_memdup_nulterm(mapped->data, mapped->size);
+    tor_munmap_file(mapped);
   }
-  if (!*answer) { /* try loading it from disk */
-
-    tor_mmap_t *mapped = networkstatus_map_cached_consensus(flavor_name);
-    if (mapped) {
-      *answer = tor_memdup_nulterm(mapped->data, mapped->size);
-      tor_munmap_file(mapped);
-    }
-    if (!*answer) { /* generate an error */
-      *errmsg = "Could not open cached consensus. "
-        "Make sure FetchUselessDescriptors is set to 1.";
-      return -1;
+  if (!*answer) { /* Maybe it's in the cache? */
+    if (we_want_to_fetch_flavor(get_options(), flavor)) {
+      const cached_dir_t *consensus = dirserv_get_consensus(flavor_name);
+      if (consensus) {
+        *answer = tor_strdup(consensus->dir);
+      }
     }
   }
+  if (!*answer) { /* generate an error */
+    *errmsg = "Could not open cached consensus. "
+      "Make sure FetchUselessDescriptors is set to 1.";
+    return -1;
+  }
   return 0;
 }
 
diff --git a/src/feature/dirclient/dirclient.c b/src/feature/dirclient/dirclient.c
@@ -2280,18 +2280,23 @@ handle_response_fetch_consensus(dir_connection_t *conn,
 
   if (looks_like_a_consensus_diff(body, body_len)) {
     /* First find our previous consensus. Maybe it's in ram, maybe not. */
-    cached_dir_t *cd = dirserv_get_consensus(flavname);
+    cached_dir_t *cd = NULL;
     const char *consensus_body = NULL;
     size_t consensus_body_len;
     tor_mmap_t *mapped_consensus = NULL;
-    if (cd) {
-      consensus_body = cd->dir;
-      consensus_body_len = cd->dir_len;
+
+    /* We prefer the mmap'd version over the cached_dir_t version,
+     * since that matches the logic we used when we picked a consensus
+     * back in dir_consensus_request_set_additional_headers. */
+    mapped_consensus = networkstatus_map_cached_consensus(flavname);
+    if (mapped_consensus) {
+      consensus_body = mapped_consensus->data;
+      consensus_body_len = mapped_consensus->size;
     } else {
-      mapped_consensus = networkstatus_map_cached_consensus(flavname);
-      if (mapped_consensus) {
-        consensus_body = mapped_consensus->data;
-        consensus_body_len = mapped_consensus->size;
+      cd = dirserv_get_consensus(flavname);
+      if (cd) {
+        consensus_body = cd->dir;
+        consensus_body_len = cd->dir_len;
       }
     }
     if (!consensus_body) {