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Description of problem:
Please see upstream bug report at https://bugzilla.mindrot.org/show_bug.cgi?id=2167 .
I attached a fix in that report. Please backport to RHEL/Fedora's openssh
package when the fix is committed, for this bug actually blocked an unattended
ssh session (execution of batched job) of an enterprise server.
Version-Release number of selected component (if applicable):
Any.
How reproducible:
100% reproducible when fork() in privsep_postauth() fails.
Steps to Reproduce:
1. Build as usual like "rpmbuild -bb openssh.spec".
2. Go to the build directory and replace fork() in privsep_postauth() in sshd.c
with -1 and rebuild using "make".
3. Run ./sshd and try to connect as an unprivileged user.
Actual results:
Connection cannot be closed when fork() fails.
Expected results:
Connection should be closed immediately when fork() fails.
Created attachment 822474[details]
fix cleanup in openssh-5.3p1-audit.patch
Please apply this patch on your openssh-5.3p1-audit.patch from src.rpm and check if it help you.
Hello. Thank you for the patch.
The patch fixes fork() failure case in privsep_postauth() but does not fix
fork() failure case in privsep_preauth(), for pmonitor->m_pid == 0 in the
latter function.
I don't know whether it is safe to change privsep_preauth() from
pid = fork();
if (pid == -1) {
fatal("fork of unprivileged child failed");
} else if (pid != 0) {
to
pmonitor->m_pid = fork();
if (pmonitor->m_pid == -1) {
fatal("fork of unprivileged child failed");
} else if (pmonitor->m_pid != 0) {
like privsep_postauth() does. But at least changing privsep_preauth() like
pid = fork();
if (pid == -1) {
+ pmonitor->m_pid = -1
fatal("fork of unprivileged child failed");
} else if (pid != 0) {
can fix fork() failure case in privsep_preauth().
Regards.
Thanks for testing. You are right about privsep_preauth(). I personally would use:
@@ -633,7 +683,7 @@ privsep_preauth(Authctxt *authctxt)
/* Store a pointer to the kex for later rekeying */
pmonitor->m_pkex = &xxx_kex;
- pid = fork();
+ pmonitor->m_pid = pid = fork();
if (pid == -1) {
fatal("fork of unprivileged child failed");
} else if (pid != 0) {
but it's only a cosmetic change. The fix will be included in the update.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
http://rhn.redhat.com/errata/RHSA-2014-1552.html