[tor-dev] permission denied when running snowflake-client with debian-tor user

[iry]

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Dear Tor developers,

I met a problem when trying to use the snowflake-client binary
extracted from TBB 8.0a8 with the system Tor.

Specifically, it seems snowflake-client cannot be run by debian-tor
user, regardless of the permissions it is given.

I am posting the full steps below. A better formatted version of it
can be found here:
http://forums.whonix.org/t/replacing-meek-snowflake/5190/18

> Here is the original permission and ownership of snowflake-client:
> 
> user at host:~$ ls -l snowflake-client -rwx------ 1 user user 14160744
> Jun  4 06:17 snowflake-client
> 
> It can be executed by user user:
> 
> user at host:~$ sudo -u user ./snowflake-client 2018/06/04 06:18:21
> 
> 
> --- Starting Snowflake Client --- 2018/06/04 06:18:21 No HTTP
> signaling detected. Using manual copy-paste signaling. 2018/06/04
> 06:18:21 Waiting for a "signal" pipe... ^C
> 
> We now change the permission to let it executable by user
> debian-tor:
> 
> user at host:~$ sudo chmod 777 snowflake-client
> 
> 
> user at host:~$ sudo -u debian-tor ./snowflake-client 2018/06/04
> 06:18:43
> 
> Noticed the permission denied:
> 
> --- Starting Snowflake Client --- 2018/06/04 06:18:43 No HTTP
> signaling detected. Using manual copy-paste signaling. 2018/06/04
> 06:18:43 Waiting for a "signal" pipe... 2018/06/04 06:18:43 open
> signal: permission denied
> 
> We now change its ownership to debian-tor:debian-tor:
> 
> user at host:~$ sudo chown debian-tor:debian-tor snowflake-client 
> user at host:~$ ls -l snowflake-client -rwxrwxrwx 1 debian-tor
> debian-tor 14160744 Jun  4 06:17 snowflake-client
> 
> Still, permission denied:
> 
> user at host:~$ sudo -u debian-tor ./snowflake-client 2018/06/04
> 06:19:15
> 
> 
> --- Starting Snowflake Client --- 2018/06/04 06:19:15 No HTTP
> signaling detected. Using manual copy-paste signaling. 2018/06/04
> 06:19:15 Waiting for a "signal" pipe... 2018/06/04 06:19:15 open
> signal: permission denied
> 
> However, when executing it by user, it works fine:
> 
> user at host:~$ sudo -u user ./snowflake-client 2018/06/04 06:19:22
> 
> 
> --- Starting Snowflake Client --- 2018/06/04 06:19:22 No HTTP
> signaling detected. Using manual copy-paste signaling. 2018/06/04
> 06:19:22 Waiting for a "signal" pipe... ^C

I didn't find any special requirement for the user who runs
snowflake-client from the documentation, so it would be extremely
helpful and appreciated if you could share some insights on this
problem. :)

Best Regards,
iry
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