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selinux: log raw contexts as untrusted strings

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These strings may come from untrusted sources (e.g. file xattrs) so they
need to be properly escaped.

Reproducer:
    # setenforce 0
    # touch /tmp/test
    # setfattr -n security.selinux -v 'kuřecí řízek' /tmp/test
    # runcon system_u:system_r:sshd_t:s0 cat /tmp/test
    (look at the generated AVCs)

Actual result:
    type=AVC [...] trawcon=kuřecí řízek

Expected result:
    type=AVC [...] trawcon=6B75C5996563C3AD20C599C3AD7A656B

Fixes: fede148324 ("selinux: log invalid contexts in AVCs")
Cc: stable@vger.kernel.org # v5.1+
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Ondrej Mosnacek 2019-06-11 10:07:19 +02:00 committed by Paul Moore
parent 05174c95b8
commit aff7ed4851
1 changed files with 8 additions and 2 deletions
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10
security/selinux/avc.c
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@ -739,14 +739,20 @@ static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
rc = security_sid_to_context_inval(sad->state, sad->ssid, &scontext,
&scontext_len);
if (!rc && scontext) {
audit_log_format(ab, " srawcon=%s", scontext);
if (scontext_len && scontext[scontext_len - 1] == '\0')
scontext_len--;
audit_log_format(ab, " srawcon=");
audit_log_n_untrustedstring(ab, scontext, scontext_len);
kfree(scontext);
}
rc = security_sid_to_context_inval(sad->state, sad->tsid, &scontext,
&scontext_len);
if (!rc && scontext) {
audit_log_format(ab, " trawcon=%s", scontext);
if (scontext_len && scontext[scontext_len - 1] == '\0')
scontext_len--;
audit_log_format(ab, " trawcon=");
audit_log_n_untrustedstring(ab, scontext, scontext_len);
kfree(scontext);
}
}