problematic client behaviours, controlled by two new sshd_config(5) options:
PerSourcePenalties and PerSourcePenaltyExemptList.
When PerSourcePenalties are enabled, sshd(8) will monitor the exit
status of its child pre-auth session processes. Through the exit
status, it can observe situations where the session did not
authenticate as expected. These conditions include when the client
repeatedly attempted authentication unsucessfully (possibly indicating
an attack against one or more accounts, e.g. password guessing), or
when client behaviour caused sshd to crash (possibly indicating
attempts to exploit sshd).
When such a condition is observed, sshd will record a penalty of some
duration (e.g. 30 seconds) against the client's address. If this time
is above a minimum threshold specified by the PerSourcePenalties, then
connections from the client address will be refused (along with any
others in the same PerSourceNetBlockSize CIDR range).
Repeated offenses by the same client address will accrue greater
penalties, up to a configurable maximum. A PerSourcePenaltyExemptList
option allows certain address ranges to be exempt from all penalties.
We hope these options will make it significantly more difficult for
attackers to find accounts with weak/guessable passwords or exploit
bugs in sshd(8) itself.
PerSourcePenalties is off by default, but we expect to enable it
automatically in the near future.
much feedback markus@ and others, ok markus@
OpenBSD-Commit-ID: 89ded70eccb2b4926ef0366a4d58a693de366cca
separate sshd-session process - reserve them early and fatal if we can't
dup2(2) them later. The pre-split fallback to re-reading the configuration
files is not possible, so sshd-session absolutely requires the fd the
configuration is passed over to be in order.
ok deraadt@
OpenBSD-Commit-ID: 308a98ef3c8a6665ebf92c7c9a0fc9600ccd7065
binaries. This step splits sshd into a listener and a session binary. More
splits are planned.
After this changes, the listener binary will validate the configuration,
load the hostkeys, listen on port 22 and manage MaxStartups only. All
session handling will be performed by a new sshd-session binary that the
listener fork+execs.
This reduces the listener process to the minimum necessary and sets us
up for future work on the sshd-session binary.
feedback/ok markus@ deraadt@
NB. if you're updating via source, please restart sshd after installing,
otherwise you run the risk of locking yourself out.
OpenBSD-Commit-ID: 43c04a1ab96cdbdeb53d2df0125a6d42c5f19934
This adds another transport protocol extension to allow a sshd to send
SSH2_MSG_EXT_INFO during user authentication, after the server has
learned the username that is being logged in to.
This lets sshd to update the acceptable signature algoritms for public
key authentication, and allows these to be varied via sshd_config(5)
"Match" directives, which are evaluated after the server learns the
username being authenticated.
Full details in the PROTOCOL file
OpenBSD-Commit-ID: 1de7da7f2b6c32a46043d75fcd49b0cbb7db7779
This adds kex_proposal_populate_entries (and corresponding free) which
populates the KEX proposal array with dynamically allocated strings.
This replaces the previous mix of static and dynamic that has been the
source of previous leaks and bugs. Remove unused compat functions.
With & ok djm@.
OpenBSD-Commit-ID: f2f99da4aae2233cb18bf9c749320c5e040a9c7b
effective configuration without attempting to load private keys and perform
other checks. This allows usage of the option before keys have been
generated.
bz3460 feedback/ok dtucker@
OpenBSD-Commit-ID: 774504f629023fc25a559ab1d95401adb3a7fb29
This adds a sshd_config ChannelTimeouts directive that allows channels that
have not seen traffic in a configurable interval to be automatically closed.
Different timeouts may be applied to session, X11, agent and TCP forwarding
channels.
Note: this only affects channels over an opened SSH connection and not
the connection itself. Most clients close the connection when their channels
go away, with a notable exception being ssh(1) in multiplexing mode.
ok markus dtucker
OpenBSD-Commit-ID: ae8bba3ed9d9f95ff2e2dc8dcadfa36b48e6c0b8
started with one or more signals masked (sigprocmask(2) is not cleared
on fork/exec) and this could interfere with various things, e.g. the
login grace timer.
Execution environments that fail to clear the signal mask before running
sshd are clearly broken, but apparently they do exist.
Reported by Sreedhar Balasubramanian; ok dtucker@
OpenBSD-Commit-ID: 77078c0b1c53c780269fc0c416f121d05e3010ae
userspace: remove vestigial '?' cases from top-level getopt(3) loops
getopt(3) returns '?' when it encounters a flag not present in the in
the optstring or if a flag is missing its option argument. We can
handle this case with the "default" failure case with no loss of
legibility. Hence, remove all the redundant "case '?':" lines.
Prompted by dlg@. With help from dlg@ and millert@.
Link: https://marc.info/?l=openbsd-tech&m=167011979726449&w=2
ok naddy@ millert@ dlg@
OpenBSD-Commit-ID: b2f89346538ce4f5b33ab8011a23e0626a67e66e
This was added for the benefit of platforms using ssh-rand-helper to
prevent a delay on each connection as sshd reseeded itself.
ssh-random-helper is long gone, and since the re-exec happens before the
chroot the re-execed sshd can reseed itself normally. ok djm@
seed_rng will initialize OpenSSL, and some engine providers (eg Intel's
QAT) will open descriptors for their own use. bz#3483, patch from
joel.d.schuetze at intel.com, ok djm@
beneath this limit will be ignored for user and host-based authentication.
Feedback deraadt@ ok markus@
OpenBSD-Commit-ID: 187931dfc19d51873df5930a04f2d972adf1f7f1
and list_hostkey_types() that are passed to compat_pkalg_proposal(). Part of
github PR#324 from ZoltanFridrich, ok djm@
This is a roll-forward of the previous rollback now that the required
changes in compat.c have been done.
OpenBSD-Commit-ID: c7cd93730b3b9f53cdad3ae32462922834ef73eb
compat_pkalg_proposal and friends always allocate their returned strings.
Reported by Qualys.
OpenBSD-Commit-ID: 1c7a88a0d5033f42f88ab9bec58ef1cf72c81ad0
and list_hostkey_types() that are passed to compat_pkalg_proposal(). Part of
github PR#324 from ZoltanFridrich, ok djm@
OpenBSD-Commit-ID: b2f6e5f60f2bba293b831654328a8a0035ef4a1b
re-exec path - we're never going to use the result and if the operation fails
then it can prevent connections from being accepted. Reported by Aaron
Poffenberger; with / ok dtucker@
OpenBSD-Commit-ID: 44c53a43909a328e2f5ab26070fdef3594eded60
call, and terminate sshd if ppoll() returns errno==EINVAL
avoids spin in ppoll when MaxStartups > RLIMIT_NOFILE, reported by
Daniel Micay
feedback/ok deraadt
OpenBSD-Commit-ID: dbab1c24993ac977ec24d83283b8b7528f7c2c15
On some (most? all?) SysV based systems with STREAMS based ptys,
sshd could acquire a controlling terminal during pty setup when
it pushed the "ptem" module, due to what is probably a bug in
the STREAMS driver that's old enough to vote. Because it was the
privileged sshd's controlling terminal, it was not available for
the user's session, which ended up without one. This is known to
affect at least Solaris <=10, derivatives such as OpenIndiana and
several other SysV systems. See bz#245 for the backstory.
In the we past worked around that by not calling setsid in the
privileged sshd child, which meant it was not a session or process
group leader. This solved controlling terminal problem because sshd
was not eligble to acquire one, but had other side effects such as
not cleaning up helper subprocesses in the SIGALRM handler since it
was not PG leader. Recent cleanups in the signal handler uncovered
this, resulting in the LoginGraceTime timer not cleaning up privsep
unprivileged processes.
This change moves the workaround into the STREAMS pty allocation code,
by allocating a sacrificial pty to act as sshd's controlling terminal
before allocating user ptys, so those are still available for users'
sessions.
On the down side:
- this will waste a pty per ssh connection on affected platforms.
On the up side:
- it makes the process group behaviour consistent between platforms.
- it puts the workaround nearest the code that actually causes the
problem and competely out of the mainline code.
- the workaround is only activated if you use the STREAMS code. If,
say, Solaris 11 has the bug but also a working openpty() it doesn't
matter that we defined SSHD_ACQUIRES_CTTY.
- the workaround is only activated when the fist pty is allocated,
ie in the post-auth privsep monitor. This means there's no risk
of fd leaks to the unprivileged processes, and there's no effect on
sessions that do not allocate a pty.
Based on analysis and work by djm@, ok djm@
SIGALRM handler. It's no longer needed since the child will get terminated by
the SIGTERM to the process group that cleans up any auth helpers, it
simplifies the signal handler and removes the risk of a race when updating
the PID. Based on analysis by HerrSpace in github PR#289, ok djm@
OpenBSD-Commit-ID: 2be1ffa28b4051ad9e33bb4371e2ec8a31d6d663
which interferes with the new poll()-based listen loop; spotted and debugged
by anton@+deraadt@
OpenBSD-Commit-ID: f7ab8ab124f615a2e0c45fee14c38d2f2abbabbd
returns -1, eg if it was interrupted by a signal. This should prevent
the hang discovered by sthen@ wherein sshd receives a SIGHUP while it has
an unauthenticated child and goes on to a blocking read on a notify_pipe.
feedback deraadt@, ok djm@
OpenBSD-Commit-ID: 0243c1c5544fca0974dae92cd4079543a3fceaa0
keys. Allows use of certificates with private keys held in a ssh-agent.
Reported by Miles Zhou in bz3524; ok dtucker@
OpenBSD-Commit-ID: 25f5bf70003126d19162862d9eb380bf34bac22a
pselect() and mask signals while checking signal flags, umasking for pselect
and restoring afterwards. Also restore signals before sighup_restart so they
don't remain blocked after restart.
This prevents a race where a SIGTERM or SIGHUP can arrive between
checking the flag and calling select (eg if sshd is processing a
new connection) resulting in sshd not shutting down until the next
time it receives a new connection. bz#2158, with & ok djm@
OpenBSD-Commit-ID: bf85bf880fd78e00d7478657644fcda97b9a936f
location of the "moduli" file containing the groups for DH-GEX. This will
allow us to run tests against arbitrary moduli files without having to
install them. ok djm@
OpenBSD-Commit-ID: 8df99d60b14ecaaa28f3469d01fc7f56bff49f66
works on OpenBSD it can cause problems on other platforms. From kircherlike
at outlook.com via bz#3259, ok djm@
OpenBSD-Commit-ID: 3e241d7ac1ee77e3de3651780b5dc47b283a7668
djm@openbsd.org
Damien Miller
Darren Tucker
guenther@openbsd.org
dtucker@openbsd.org
millert@openbsd.org
cheloha@openbsd.org
deraadt@openbsd.org