[tor-bugs] #29819 [Core Tor/Tor]: Seccomp: sandbox crash on rt_sigaction with libseccomp 0.2.4

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#29819: Seccomp: sandbox crash on rt_sigaction with libseccomp 0.2.4
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 Reporter:  toralf                 |          Owner:  nickm
     Type:  defect                 |         Status:  assigned
 Priority:  Medium                 |      Milestone:  Tor: 0.4.0.x-final
Component:  Core Tor/Tor           |        Version:  Tor: unspecified
 Severity:  Normal                 |     Resolution:
 Keywords:  crash, linux, sandbox  |  Actual Points:
Parent ID:                         |         Points:  0.2
 Reviewer:                         |        Sponsor:
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Comment (by pege):

 Looks like Tor used libseccomp in a way it was never intended to be used.
 See
 [https://github.com/seccomp/libseccomp/issues/148#issuecomment-482796234
 this comment] and the
 [https://github.com/seccomp/libseccomp/issues/148#issuecomment-483057151
 response here].

 Nickm, I think you know the Sandbox better than I do. Where do we go from
 here? I'd say we just return EPERM whenever we want to deny access. I'd
 expect this to be least likely to introduce any regressions. If we just
 fail with SIGSYS, this is likely to break on one system or another. On
 Fedora, at least OpenSSL attemps to open file that's not allowed, namely,
 `/etc/crypto-policies/back-ends/openssl.config`. We can always decide to
 switch to SYSSIG later on, after thorough testing but I think first we
 should make sure no more installations break because of a libseccomp
 v2.4.0 upgrade.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29819#comment:19>
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