This change breaks existing behavior.
Before, a missing ClientConfig.HostKeyCallback would cause host key
checking to be disabled. In this configuration, establishing a
connection to any host just works, so today, most SSH client code in
the wild does not perform any host key checks.
This makes it easy to perform a MITM attack:
* SSH installations that use keyboard-interactive or password
authentication can be attacked with MITM, thereby stealing
passwords.
* Clients that use public-key authentication with agent forwarding are
also vulnerable: the MITM server could allow the login to succeed, and
then immediately ask the agent to authenticate the login to the real
server.
* Clients that use public-key authentication without agent forwarding
are harder to attack unnoticedly: an attacker cannot authenticate the
login to the real server, so it cannot in general present a convincing
server to the victim.
Now, a missing HostKeyCallback will cause the handshake to fail. This
change also provides InsecureIgnoreHostKey() and FixedHostKey(key) as
ready made host checkers.
A simplistic parser for OpenSSH's known_hosts file is given as an
example. This change does not provide a full-fledged parser, as it
has complexity (wildcards, revocation, hashed addresses) that will
need further consideration.
When introduced, the host checking feature maintained backward
compatibility at the expense of security. We have decided this is not
the right tradeoff for the SSH library.
Fixesgolang/go#19767
Change-Id: I45fc7ba9bd1ea29c31ec23f115cdbab99913e814
Reviewed-on: https://go-review.googlesource.com/38701
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
According to RFC 4254 section 6.10, SSH server implementations may
omit the exit-status and exit-signal messages. If this happens, we
now return &ExitMissingError{}, so clients can handle this case
specifically.
This came up in the discussion of issue #16194.
Change-Id: Iae5e916b18aa5bd8e95618e9fcfcab8b19e147d9
Reviewed-on: https://go-review.googlesource.com/24727
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
I ran go vet over all of go.crypto and removed lots of panic("unreachable") that are no longer needed.
R=golang-dev, r, dgryski
CC=golang-dev
https://golang.org/cl/10113043
Followup CL for 9711043. The order that CombinedOutput returns data captured from stdout/stderr is not specified, so we have to test both variants.
Thanks to fullung for the bug report.
R=fullung, kr
CC=golang-dev
https://golang.org/cl/9921044
When running the ssh tests several times (e.g. with -cpu 1,2), the
second run would fail because testing globals had been altered. This
change avoids altering the globals since the default worked anyway.
Fixesgolang/go#4715.
R=golang-dev, minux.ma
CC=golang-dev
https://golang.org/cl/7903045
The check for a sensible packet length was removed a while ago
when the window size and channel packet size checks were moved
into channel.go. While the RFC suggests that any packet of size
less than uint32 -1 is valid, most implmentations limit the size
to a smaller value. OpenSSH chose 256kb, so that sounds like a
sensible default.
R=agl, huin, kardianos
CC=golang-dev
https://golang.org/cl/6490098
Fixesgolang/go#3810.
Fixes chanWriter Write after close behaviour bug.
Fixes serverChan writePacket after close bug.
Addresses final comments by agl on 6405064, plus various cleanups.
R=agl, kardianos, gustav.paul, fullung
CC=golang-dev
https://golang.org/cl/6479056
Fixesgolang/go#3989.
Tested for several hours on an 8 core ec2 instance with
random GOMAXPROC values.
Also, rolls server_test.go into session_test using the
existing dial() framework.
R=fullung, agl, kardianos
CC=golang-dev
https://golang.org/cl/6475063
Use a handler that does not attempt to send a status message
as the failing test closes the connection abruptly.
Also, check the err response on all shell.ReadLine operations.
R=agl, minux.ma, kardianos
CC=golang-dev
https://golang.org/cl/6487043
Fixesgolang/go#3810.
This change introduces an atomic boolean to guard the close
of the clientChan. Previously the client code was quite
lax with the ordering of the close messages and could allow
window adjustment or EOF messages to leak after Close had
been signaled.
Consolidating the changes to the serverChan will be handled
in a following CL.
R=agl, kardianos, gustav.paul
CC=golang-dev
https://golang.org/cl/6405064
This proposal moves the check for max packet into
channel.writePacket. Callers should be aware they cannot
pass a buffer larger than max packet. This is only a
concern to chanWriter.Write and appropriate guards are
already in place.
There was some max packet handling in transport.go but it was
incorrect. This has been removed.
This proposal also cleans up session_test.go.
R=gustav.paul, agl, fullung, huin
CC=golang-dev
https://golang.org/cl/6460075
RFC 4254 s5.2 is clear that a client must never send a data
packet larger than the value of maximum packet supplied by the
remote side during channel setup. The client was not honoring
this value, in fact it wasn't even recording it.
Thanks to Albert Strasheim for the bug report.
R=agl, fullung
CC=golang-dev
https://golang.org/cl/6448128
The RFC doesn't prohibit zero sized window adjustments and
there is evidence of well known clients using them in the
wild.
R=agl, kardianos, gustav.paul
CC=golang-dev
https://golang.org/cl/6209082
When shutting down the test, we sometimes see EOF on the server's side
of the connection and sometimes ECONNRESET. In the latter case, based
on timing, it was possible that the server loop would hit Errorf during
shutdown and cause the test to fail.
R=dave
CC=golang-dev
https://golang.org/cl/6125047
This change prevents bad servers from crashing a client by sending an
invalid channel ID. It also makes the client disconnect in more cases
of invalid messages from a server and cleans up the client channels
in the event of a disconnect.
R=dave
CC=golang-dev
https://golang.org/cl/6099050
This removes the sole "exp/foo" import in the Go subrepos.
A separate CL will remove exp/terminal from the standard Go repository.
R=golang-dev, dave, r
CC=golang-dev
https://golang.org/cl/5966045
Manual edits to README.
Moved from main Go repository, deleted Makefiles, ran gofix -r go1rename.
Tested with: go test code.google.com/p/go.crypto/...
R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5564059
Han-Wen Nienhuys
Andrew Gerrand
Adam Langley
Jonathan Pittman
Dave Cheney
Keith Rarick
Eric Milliken
David Symonds
Daniel Theophanes
Russ Cox