Date: Tue, 13 Jun 2017 12:32:10 +0000 From: Fiedler Roman <Roman.Fiedler@....ac.at> To: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com> Subject: Re: Vixie/ISC Cron group crontab to root escalation > From: Jakub Wilk [mailto:jwilk@...lk.net] > > * Fiedler Roman <Roman.Fiedler@....ac.at>, 2017-06-13, 07:45: > >>>Thanks, perhaps a comment in the code can't hurt... > >>>Or even O_NODEV which does not exist, or O_PATH (linux only).. > >> > >>As there is a O_DIRECTORY it would be more orthogonal to have > O_REGULAR (open > >>only a regular file). But that becomes more and more icky as we're > running > >>out of 32 bits of O_*) > > > >Why not stop that at all and have an O_POLICY, > > With help of O_PATH, you can implement almost any sanity check in > userspace. > No need to reinvent this particular wheel. Well, partially: what O_PATH can do, you could also do before O_PATH using repeated single-level open(NO_FOLLOW)/fstat-checks. So you had to do all the verification by yourself. fts  does that the same in a secure manner. But often implementation was too complex using syscalls or not easy to do using the library, so not many programmers did it. The resulting programs were more prone to be vulnerable. With O_PATH/fts und own fstat calls, you can also do all the things mentioned above, but again, I fear, not many will use them, there for convenience syscalls/libraries should help out. So decision could be a) do nothing, b) blow up libc or c) blow up syscall interface. Specific libraries or programming best practices might not be easy enough to be applied. LG Roman  https://www.freebsd.org/cgi/man.cgi?query=fts&sektion=3 Download attachment "smime.p7s" of type "application/pkcs7-signature" (4814 bytes)
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