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Re: [tor-bugs] #28861 [Core Tor/Torsocks]: torsocks: Unsupported syscall number 217
#28861: torsocks: Unsupported syscall number 217
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Reporter: ilf | Owner: dgoulet
Type: defect | Status: assigned
Priority: Medium | Milestone:
Component: Core Tor/Torsocks | Version: Tor: 0.3.4.9
Severity: Normal | Resolution:
Keywords: torsocks, syscall, 217 | Actual Points:
Parent ID: | Points:
Reviewer: | Sponsor:
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Comment (by onirony):
I'm working on a seccomp based torsocks that should eliminate issues of
this sort. Syscalls in torsocks are explicitly whitelisted and
getdents/getdents64 are not on the whitelist. getdents seems very harmless
to me and I think it should be whitelisted.
@ilf, in the meantime here is a patched torsocks that can run getdents and
getdents64 (the syscall it's rejecting in your error message):
https://github.com/seisvelas/torsocks/tree/getdent_fix
The getdents code I used to test my patch is just the example from the
Linux man page and can be found here: http://man7.org/linux/man-
pages/man2/getdents.2.html#EXAMPLE
When I compiled that getdents example code and attempted to run it through
standard torsocks this happened:
{{{
hc01@HC01:~$ /usr/bin/torsocks ./a.out
[Dec 19 16:31:02] WARNING torsocks[16567]: [syscall] Unsupported syscall
number 78.
Denying the call (in tsocks_syscall() at syscall.c:465)
getdents: Function not implemented
}}}
Then, using my patched torsocks:
{{{
hc01@HC01:~$ torsocks ./a.out
--------------- nread=1008 ---------------
i-node# file type d_reclen d_off d_name
23068679 directory 32 22651653883364612 .cache
23069803 directory 32 72324196525406672 .compiz
...
}}}
When I modified the code to use getdents64, I received the same error from
torsocks. With my patch it ran properly. I'm going to bother David Goulet
and set this ticket to 'needs review' to see if my patch is safe and can
be accepted!
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/28861#comment:1>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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