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>
The RequestPty function takes the size arguments in the order height,
then width, instead of the more common width, then height. 80 is a very
common width for a terminal, so when the example reads RequestPty(...,
80, 40, ...), it's easy to assume that the order is width-height.
Switching the order should make it more obvious what is going on.
Change-Id: I1d6266b1c0dcde5ee6e31a6d26d2dcaf14fec58a
Reviewed-on: https://go-review.googlesource.com/18290
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
After discussion around an example SFTP implementation:
https://github.com/pkg/sftp/pull/54
it has been suggested that errors should be handled using
log.Fatal rather than panic, and that the actual underlying error
should also be logged. In the existing SSH examples there
are several different styles of error handling using both panic
and log.Fatalf.
This patch uses log.Fatal consistently for all of these cases.
Change-Id: I2cebfae1821530dc3c5bbc46d451fe026bed582f
Reviewed-on: https://go-review.googlesource.com/16736
Reviewed-by: Russ Cox <rsc@golang.org>
Fixesgolang/go#9747
Move the example tests to an external test package so that they
must explicitly reference the ssh package. The side effect is the
examples now become easier to copy and paste.
Change-Id: Ibbddea42bc5a41d11ffdef5144d9884ef3ef603f
Reviewed-on: https://go-review.googlesource.com/3710
Reviewed-by: Andrew Gerrand <adg@golang.org>
Add support for server (remote) forwarded tcpip channels.
See RFC4254 Section 7.1
R=gustav.paul, jeff, agl, lieqiewang
CC=golang-dev
https://golang.org/cl/6038047
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
Bryan C. Mills
Nicola Murino
cui fliter
Emmanuel T Odeke
Han-Wen Nienhuys
Henrik Hodne
Emmanuel Odeke
Mike Houston
Scott Bell
Dave Cheney
Andrew Gerrand
Adam Langley
Willem van der Schyff
David Symonds
Fazlul Shahriar