Check permissions on the directory holding a control socket

2 files changed, 48 insertions, 0 deletions

diff --git a/changes/bug2792_checkdir b/changes/bug2792_checkdir
new file mode 100644
index 0000000000..10de1deb2d
--- /dev/null
+++ b/changes/bug2792_checkdir
@@ -0,0 +1,8 @@
+  o Minor features:
+    - Tor now refuses to create a ControlSocket in a directory that is
+      world-readable (or group-readable if ControlSocketsGroupWritable
+      is 0).  This is necessary because some operating systems do not
+      check the permissions on an AF_UNIX socket when programs try to
+      connect to it.  Checking permissions on the directory holding
+      the socket, however, seems to work everywhere.
+
diff --git a/src/or/connection.c b/src/or/connection.c
index ab265df1af..b7d6fe408d 100644
--- a/src/or/connection.c
+++ b/src/or/connection.c
@@ -853,6 +853,43 @@ warn_too_many_conns(void)
   }
 }
 
+#ifdef HAVE_SYS_UN_H
+/** Check whether we should be willing to open an AF_UNIX socket in
+ * <b>path</b>.  Return 0 if we should go ahead and -1 if we shouldn't. */
+static int
+check_location_for_unix_socket(or_options_t *options, const char *path)
+{
+  int r = -1;
+  char *p = tor_strdup(path);
+  cpd_check_t flags = CPD_CHECK_MODE_ONLY;
+  if (get_parent_directory(p)<0)
+    goto done;
+
+  if (options->ControlSocketsGroupWritable)
+    flags |= CPD_GROUP_OK;
+
+  if (check_private_dir(p, flags) < 0) {
+    char *escpath, *escdir;
+    escpath = esc_for_log(path);
+    escdir = esc_for_log(p);
+    log_warn(LD_GENERAL, "Before Tor can create a control socket in %s, the "
+             "directory %s needs to exist, and to be accessible only by the "
+             "user%s account that is running Tor.  (On some Unix systems, "
+             "anybody who can list a socket can conect to it, so Tor is "
+             "being careful.)", escpath, escdir,
+             options->ControlSocketsGroupWritable ? " and group" : "");
+    tor_free(escpath);
+    tor_free(escdir);
+    goto done;
+  }
+
+  r = 0;
+ done:
+  tor_free(p);
+  return r;
+}
+#endif
+
 /** Bind a new non-blocking socket listening to the socket described
  * by <b>listensockaddr</b>.
  *
@@ -947,6 +984,9 @@ connection_create_listener(const struct sockaddr *listensockaddr,
      * and listeners at the same time */
     tor_assert(type == CONN_TYPE_CONTROL_LISTENER);
 
+    if (check_location_for_unix_socket(get_options(), address) < 0)
+      goto err;
+
     log_notice(LD_NET, "Opening %s on %s",
                conn_type_to_string(type), address);