Don't pass a NULL into a %s when logging client auth file load failure

Fortunately, in 0.3.5.1-alpha we improved logging for various
failure cases involved with onion service client auth.

Unfortunately, for this one, we freed the file right before logging
its name.

Fortunately, tor_free() sets its pointer to NULL, so we didn't have
a use-after-free bug.

Unfortunately, passing NULL to %s is not defined.

Fortunately, GCC 9.1.1 caught the issue!

Unfortunately, nobody has actually tried building Tor with GCC 9.1.1
before. Or if they had, they didn't report the warning.

Fixes bug 30475; bugfix on 0.3.5.1-alpha.

diff --git a/changes/bug30475 b/changes/bug30475
new file mode 100644 (file)
index 0000000..839597b
--- /dev/null
+++ b/changes/bug30475
@@ -0,0 +1,4 @@
+  o Minor bugfixes ():
+    - Avoid a GCC 9.1.1 warning (and possible crash depending on libc
+      implemenation) when failing to load a hidden service client authorization
+      file.  Fixes bug 30475; bugfix on 0.3.5.1-alpha.

diff --git a/src/feature/hs/hs_service.c b/src/feature/hs/hs_service.c
index 828ca1da45175d5d434745c4ecf672cd29abfb32..402929036405ffb51e3a9556d4bfe1da1b75756a 100644 (file)
--- a/src/feature/hs/hs_service.c
+++ b/src/feature/hs/hs_service.c
@@ -1259,16 +1259,16 @@ load_client_keys(hs_service_t *service)
     client_key_file_path = hs_path_from_filename(client_keys_dir_path,
                                                  filename);
     client_key_str = read_file_to_str(client_key_file_path, 0, NULL);
-    /* Free immediately after using it. */
-    tor_free(client_key_file_path);
 
     /* If we cannot read the file, continue with the next file. */
     if (!client_key_str)  {
       log_warn(LD_REND, "Client authorization file %s can't be read. "
                         "Corrupted or verify permission? Ignoring.",
                client_key_file_path);
+      tor_free(client_key_file_path);
       continue;
     }
+    tor_free(client_key_file_path);
 
     client = parse_authorized_client(client_key_str);
     /* Wipe and free immediately after using it. */