Make ControlSocketsGroupWritable work with User.

Original message from bug3393:

check_private_dir() to ensure that ControlSocketsGroupWritable is
safe to use. Unfortunately, check_private_dir() only checks against
the currently running user… which can be root until privileges are
dropped to the user and group configured by the User config option.

The attached patch fixes the issue by adding a new effective_user
argument to check_private_dir() and updating the callers. It might
not be the best way to fix the issue, but it did in my tests.

(Code by lunar; changelog by nickm)

1 files changed, 4 insertions, 2 deletions

diff --git a/src/or/config.c b/src/or/config.c
index 44cecf353..8ab23a3b8 100644
--- a/src/or/config.c
+++ b/src/or/config.c
@@ -1025,7 +1025,8 @@ options_act_reversible(or_options_t *old_options, char **msg)
 
   /* Ensure data directory is private; create if possible. */
   if (check_private_dir(options->DataDirectory,
-                        running_tor ? CPD_CREATE : CPD_CHECK)<0) {
+                        running_tor ? CPD_CREATE : CPD_CHECK,
+                        options->User)<0) {
     tor_asprintf(msg,
               "Couldn't access/create private data directory \"%s\"",
               options->DataDirectory);
@@ -1038,7 +1039,8 @@ options_act_reversible(or_options_t *old_options, char **msg)
     char *fn = tor_malloc(len);
     tor_snprintf(fn, len, "%s"PATH_SEPARATOR"cached-status",
                  options->DataDirectory);
-    if (check_private_dir(fn, running_tor ? CPD_CREATE : CPD_CHECK) < 0) {
+    if (check_private_dir(fn, running_tor ? CPD_CREATE : CPD_CHECK,
+                          options->User) < 0) {
       tor_asprintf(msg,
                 "Couldn't access/create private data directory \"%s\"", fn);
       tor_free(fn);