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
criteria tokeniser to a more shell-like one. Apparently the old tokeniser
(accidentally?) allowed "Match criteria=argument" as well as the "Match
criteria argument" syntax that we tested for.
People were using this syntax so this adds back support for
"Match criteria=argument"
bz3739 ok dtucker
OpenBSD-Commit-ID: d1eebedb8c902002b75b75debfe1eeea1801f58a
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
A single forgotton login that times out should be below the penalty
threshold.
ok deraadt/claudio
OpenBSD-Commit-ID: cee1f7d17597c97bff8e5092af5d136fdb08f81d
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
ok markus
NB. if you run a sshd that accepts connections from behind large NAT
blocks, proxies or anything else that aggregates many possible users
behind few IP addresses, then this change may cause legitimate traffic
to be denied.
Please read the PerSourcePenalties, PerSourcePenaltyExemptList and
PerSourceNetBlockSize options in sshd_config(5) for how to tune your
sshd(8) for your specific circumstances.
OpenBSD-Commit-ID: 24a0e5c23d37e5a63e16d2c6da3920a51078f6ce
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
to the active configuration. This fixes the config parser from erroneously
rejecting cases like:
AuthenticationMethods password
Match User ivy
AuthenticationMethods any
bz3657 ok markus@
OpenBSD-Commit-ID: 7f196cba634c2a3dba115f3fac3c4635a2199491
fixed limit of subsystems. Saves a few kb of memory in the server and makes
it more like the other options.
OpenBSD-Commit-ID: e683dfca6bdcbc3cc339bb6c6517c0c4736a547f
This may change behaviour of exotic configurations, but the most common
subsystem configuration (sftp-server) is unlikely to be affected.
OpenBSD-Commit-ID: 8ffa296aeca981de5b0945242ce75aa6dee479bf
fatal error to being a debug message to match behaviour with just about all
other directives.
OpenBSD-Commit-ID: fc90ed2cc0c18d4eb8e33d2c5e98d25f282588ce
sshd_config.
Previously this directive would accept certificate algorithm names, but
these were unusable in practice as OpenSSH does not support CA chains.
part of bz3577; ok dtucker@
OpenBSD-Commit-ID: a992d410c8a78ec982701bc3f91043dbdb359912
INT_MAX. Fixes sign compare warnings systems with 32-bit time_t due to type
promotion. OK djm@
OpenBSD-Commit-ID: 48081e9ad35705c5f1705711704a4c2ff94e87b7
We've previously removed a lot of the really old compatibility code,
and with it went the need to include compat.h in most of the files that
have it.
OpenBSD-Commit-ID: 5af8baa194be00a3092d17598e88a5b29f7ea2b4
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
sshd_config and sshd_config; previously if the same name was reused then the
last would win (which is the opposite to how the config is supposed to work).
While there, make the ssh_config parsing more like sshd_config.
bz3438, ok dtucker
OpenBSD-Commit-ID: 797909c1e0262c0d00e09280459d7ab00f18273b
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
Historicallly, hpdelim accepted ":" or "/" as a port delimiter between
hosts (or addresses) and ports. These days most of the uses for "/"
are no longer accepted, so there are several places where it checks the
delimiter to disallow it. Make hpdelim accept only ":" and use hpdelim2
in the other cases. ok djm@
OpenBSD-Commit-ID: 7e6420bd1be87590b6840973f5ad5305804e3102
sChallengeResponseAuthentication from the enum. Noticed by
christos@zoulas.com. OK dtucker@
OpenBSD-Commit-ID: b533283a4dd6d04a867da411a4c7a8fbc90e34ff
favour of KbdInteractiveAuthentication. The former is what was in SSHv1, the
latter is what is in SSHv2 (RFC4256) and they were treated as somewhat but
not entirely equivalent. We retain the old name as deprecated alias so
config files continue to work and a reference in the man page for people
looking for it.
Prompted by bz#3303 which pointed out the discrepancy between the two
when used with Match. Man page help & ok jmc@, with & ok djm@
OpenBSD-Commit-ID: 2c1bff8e5c9852cfcdab1f3ea94dfef5a22f3b7e
similar to the previous commit, this switches sshd_config parsing to
the newer tokeniser. Config parsing will be a little stricter wrt
quote correctness and directives appearing without arguments.
feedback and ok markus@
tested in snaps for the last five or so days - thanks Theo and those who
caught bugs
OpenBSD-Commit-ID: 9c4305631d20c2d194661504ce11e1f68b20d93e
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
pubkeyacceptedalgorithms after their current names so that the config-dump
mode finds and uses the current names. Spotted by Phil Pennock.
OpenBSD-Commit-ID: 5dd10e93cccfaff3aaaa09060c917adff04a9b15
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
