DataDirectoryGroupReadable and CacheDirectoryGroupReadable conflicts forcing sandboxed Tor to crash

== Problem 1

By default DataDirectory and CacheDirectory is the same. On Debian it is /var/lib/tor. If you set DataDirectoryGroupReadable 1 in torrc (and forget about CacheDirectoryGroupReadable) and then restart Tor, you expect granting permissions to this directory. However, Tor will not do that, but change drwx--S--- permission to drwx------ for this directory (which is itself not logical---removing permissions instead of granting them). Tor will also issue a warning:

[warn] Fixing permissions on directory /var/lib/tor

Later this warning will be repeated at each startup of Tor. I think that this warning should be improved, e.g.:

[warn or err] DataDirectoryGroupReadable and CacheDirectoryGroupReadable links to the same directory. You have to set both of them to 1 of both of them to 0.

Maybe you have another suggestion (e.g., if any of these options is 1, another is 1 too). man torrc doesn't tell anything about this conflict. It should be addressed in man page too.

== Problem 2

The situation is worse when your torrc has Sandbox enabled:

DataDirectoryGroupReadable 1
CacheDirectoryGroupReadable 1
Sandbox 1

In this case Tor successfully starts, but if you issue SIGNAL RELOAD command (e.g., using tor-prompt), Tor immediately crashes with the log:

============================================================ T= XXXXXXXXXX
(Sandbox) Caught a bad syscall attempt (syscall chmod)
/usr/bin/tor(+0x1a4d66)[0x556326474d66]
/lib/x86_64-linux-gnu/libc.so.6(chmod+0x7)[0x7f63c91b4807]
/lib/x86_64-linux-gnu/libc.so.6(chmod+0x7)[0x7f63c91b4807]
/usr/bin/tor(+0xfafed)[0x5563263cafed]
/usr/bin/tor(set_options+0x2ed)[0x5563263d42dd]
/usr/bin/tor(options_init_from_string+0x4c7)[0x5563263d6d97]
/usr/bin/tor(options_init_from_torrc+0x471)[0x5563263d72f1]
/usr/bin/tor(+0x55531)[0x556326325531]
/usr/lib/x86_64-linux-gnu/libevent-2.0.so.5(event_base_loop+0xe35)[0x7f63ca776a15]
/usr/bin/tor(do_main_loop+0x25f)[0x556326325e3f]
/usr/bin/tor(tor_run_main+0x1165)[0x556326328315]
/usr/bin/tor(tor_main+0x3a)[0x55632632032a]
/usr/bin/tor(main+0x19)[0x556326320099]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf5)[0x7f63c90fab45]
/usr/bin/tor(+0x500e9)[0x5563263200e9]

Should Sandbox be in conflict with these option? If yes, this should be documented in man page, and Tor has to complain an error during startup.

== Problem 3

Suppose, you disable Sandbox, but keep the options DataDirectoryGroupReadable and CacheDirectoryGroupReadable in place. During start Tor sets directory permissions to drwxr-x--- allowing debian-tor group to list files.

If you later grant read access to any file in this directory, Tor will remove this access soon. E.g., state file loses its group read permission at each Tor's startup. Other files may lose it less frequently. We are trapped in the situation where DataDirectoryGroupReadable and CacheDirectoryGroupReadable are useless: what's the goal to be able to read directory's content, bit be unable to read any file inside it?

Earlier it was in less conflict with different tools which control Tor, because it was recommended to run each tool on behalf of debian-tor user. Now it is recommended to run it from another user who is a member of debian-tor group (see discussion in [[https://trac.torproject.org/projects/tor/ticket/25890|#25890]]), but "group approach" also fails...

Trac:
Username: wagon