This splits the user authentication code from the sshd-session
binary into a separate sshd-auth binary. This will be executed by
sshd-session to complete the user authentication phase of the
protocol only.
Splitting this code into a separate binary ensures that the crucial
pre-authentication attack surface has an entirely disjoint address
space from the code used for the rest of the connection. It also
yields a small runtime memory saving as the authentication code will
be unloaded after thhe authentication phase completes.
Joint work with markus@ feedback deraadt@
Tested in snaps since last week
OpenBSD-Commit-ID: 9c3b2087ae08626ec31b4177b023db600e986d9c
options.
This allows writing Match conditions that trigger for invalid username.
E.g.
PerSourcePenalties refuseconnection:90s
Match invalid-user
RefuseConnection yes
Will effectively penalise bots try to guess passwords for bogus accounts,
at the cost of implicitly revealing which accounts are invalid.
feedback markus@
OpenBSD-Commit-ID: 93d3a46ca04bbd9d84a94d1e1d9d3a21073fbb07
PerSourcePenalties
This allows penalising connection sources that have had connections
dropped by the RefuseConnection option. ok markus@
OpenBSD-Commit-ID: 3c8443c427470bb3eac1880aa075cb4864463cb6
If set, this will terminate the connection at the first authentication
request (this is the earliest we can evaluate sshd_config Match blocks)
ok markus@
OpenBSD-Commit-ID: 43cc2533984074c44d0d2f92eb93f661e7a0b09c
Allows selecting which PAM service name to use when UsePAM is
enabled. Defaults to "sshd" unless overridden at compile time
by defining SSHD_PAM_SERVICE.
bz2102, ok dtucker@
used one shared table and overflow policy for IPv4 and IPv6 addresses, now it
will use separate tables and optionally different overflow policies.
This prevents misbehaviour from IPv6 addresses (which are vastly easier
to obtain many of) from affecting IPv4 connections and may allow for
stricter overflow policies.
ok deraadt@
OpenBSD-Commit-ID: 12637ed0aa4d5f1f3e702da42ea967cbd8bfdfd9
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
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
client connections that have no open channels for some length of time. This
complements the recently-added ChannelTimeout option that terminates inactive
channels after a timeout.
ok markus@
OpenBSD-Commit-ID: ca983be74c0350364c11f8ba3bd692f6f24f5da9
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
beneath this limit will be ignored for user and host-based authentication.
Feedback deraadt@ ok markus@
OpenBSD-Commit-ID: 187931dfc19d51873df5930a04f2d972adf1f7f1
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
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
HostbasedAcceptedKeyTypes (sshd) to HostbasedAcceptedAlgorithms, which more
accurately reflects its effect. This matches a previous change to
PubkeyAcceptedAlgorithms. The previous names are retained as aliases. ok
djm@
OpenBSD-Commit-ID: 49451c382adc6e69d3fa0e0663eeef2daa4b199e
PubkeyAcceptedAlgorithms. While the two were originally equivalent, this
actually specifies the signature algorithms that are accepted. Some key
types (eg RSA) can be used by multiple algorithms (eg ssh-rsa, rsa-sha2-512)
so the old name is becoming increasingly misleading. The old name is
retained as an alias. Prompted by bz#3253, help & ok djm@, man page help jmc@
OpenBSD-Commit-ID: 0346b2f73f54c43d4e001089759d149bfe402ca5
options which provide more fine grained MaxStartups limits. Man page help
jmc@, feedback & ok djm@
OpenBSD-Commit-ID: e2f68664e3d02c0895b35aa751c48a2af622047b
This adds a "verify-required" authorized_keys flag and a corresponding
sshd_config option that tells sshd to require that FIDO keys verify the
user identity before completing the signing/authentication attempt.
Whether or not user verification was performed is already baked into the
signature made on the FIDO token, so this is just plumbing that flag
through and adding ways to require it.
feedback and ok markus@
OpenBSD-Commit-ID: 3a2313aae153e043d57763d766bb6d55c4e276e6
rhosts/shosts, "no" allow rhosts/shosts or (new) "shosts-only" to allow
.shosts files but not .rhosts. ok dtucker@
OpenBSD-Commit-ID: d08d6930ed06377a80cf53923c1955e9589342e9
of files. This has sensible semantics wrt Match blocks and accepts glob(3)
patterns to specify the included files. Based on patch by Jakub Jelen in
bz2468; feedback and ok markus@
OpenBSD-Commit-ID: 36ed0e845b872e33f03355b936a4fff02d5794ff
keys.
Previously we didn't do this because we didn't want to expose
the attack surface presented by USB and FIDO protocol handling,
but now that this is insulated behind ssh-sk-helper there is
less risk.
ok markus@
OpenBSD-Commit-ID: 77b068dd133b8d87e0f010987bd5131e640ee64c
This directive has a single valid option "no-touch-required" that
causes sshd to skip checking whether user presence was tested before
a security key signature was made (usually by the user touching the
key).
ok markus@
OpenBSD-Commit-ID: 46e434a49802d4ed82bc0aa38cb985c198c407de
-C does not match, which allows it to work when sshd_config contains a Match
directive with or without -C. bz#2858, ok djm@
OpenBSD-Commit-ID: 1a701f0a33e3bc96753cfda2fe0b0378520b82eb
loading the default hostkeys. Hostkeys explicitly specified in the
configuration or on the command-line are still reported as errors, and
failure to load at least one host key remains a fatal error.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Based on patch from Dag-Erling Smørgrav via
https://github.com/openssh/openssh-portable/pull/103
ok markus@
OpenBSD-Commit-ID: ffc2e35a75d1008effaf05a5e27425041c27b684
control over which signature algorithms a CA may use when signing
certificates. In particular, this allows a sshd to ban certificates signed
with RSA/SHA1.
ok markus@
OpenBSD-Commit-ID: b05c86ef8b52b913ed48d54a9b9c1a7714d96bac
pattern-list of whitelisted environment variable names in addition to yes|no.
bz#1800, feedback and ok markus@
OpenBSD-Commit-ID: 77dc2b468e0bf04b53f333434ba257008a1fdf24
administrator to explicitly specify environment variables set in sessions
started by sshd. These override the default environment and any variables set
by user configuration (PermitUserEnvironment, etc), but not the SSH_*
variables set by sshd itself.
ok markus@
OpenBSD-Commit-ID: b6a96c0001ccd7dd211df6cae9e961c20fd718c0
addresses may be listened on when the client requests remote forwarding (ssh
-R).
This is the converse of the existing PermitOpen directive and this
includes some refactoring to share much of its implementation.
feedback and ok markus@
OpenBSD-Commit-ID: 15a931238c61a3f2ac74ea18a98c933e358e277f
establishes a minimum time for each failed authentication attempt (5ms) and
adds a per-user constant derived from a host secret (0-4ms). Based on work
by joona.kannisto at tut.fi, ok markus@ djm@.
OpenBSD-Commit-ID: b7845b355bb7381703339c8fb0e57e81a20ae5ca
add a "rdomain" criteria for the sshd_config Match
keyword to allow conditional configuration that depends on which rdomain(4) a
connection was recevied on. ok markus@
Upstream-ID: 27d8fd5a3f1bae18c9c6e533afdf99bff887a4fb
add sshd_config RDomain keyword to place sshd and the
subsequent user session (including the shell and any TCP/IP forwardings) into
the specified rdomain(4)
ok markus@
Upstream-ID: be2358e86346b5cacf20d90f59f980b87d1af0f5
Add optional rdomain qualifier to sshd_config's
ListenAddress option to allow listening on a different rdomain(4), e.g.
ListenAddress 0.0.0.0 rdomain 4
Upstream-ID: 24b6622c376feeed9e9be8b9605e593695ac9091
refactor channels.c
Move static state to a "struct ssh_channels" that is allocated at
runtime and tracked as a member of struct ssh.
Explicitly pass "struct ssh" to all channels functions.
Replace use of the legacy packet APIs in channels.c.
Rework sshd_config PermitOpen handling: previously the configuration
parser would call directly into the channels layer. After the refactor
this is not possible, as the channels structures are allocated at
connection time and aren't available when the configuration is parsed.
The server config parser now tracks PermitOpen itself and explicitly
configures the channels code later.
ok markus@
Upstream-ID: 11828f161656b965cc306576422613614bea2d8f
refactor authentication logging
optionally record successful auth methods and public credentials
used in a file accessible to user sessions
feedback and ok markus@
Upstream-ID: 090b93036967015717b9a54fd0467875ae9d32fb
Add a sshd_config DisableForwaring option that disables
X11, agent, TCP, tunnel and Unix domain socket forwarding, as well as
anything else we might implement in the future.
This, like the 'restrict' authorized_keys flag, is intended to be a
simple and future-proof way of restricting an account. Suggested as
a complement to 'restrict' by Jann Horn; ok markus@
Upstream-ID: 203803f66e533a474086b38a59ceb4cf2410fcf7
remove UseLogin option and support for having /bin/login
manage login sessions; ok deraadt markus dtucker
Upstream-ID: bea7213fbf158efab7e602d9d844fba4837d2712
