SSH host certificates are expected to contain hostnames only,
not "host:port" format.
This change allows Go clients to connect to OpenSSH servers that
use host certificates.
Note, this change will break any clients that use ssh.NewClientConn()
with an `addr` that is not in `host:port` format (they will see a
"missing port in address" error).
Fixes bug 20273.
Change-Id: I5a306c6b7b419a737e1f0f9c5ca8c585e21a45a4
Reviewed-on: https://go-review.googlesource.com/43475
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Dialing the 0.0.0.0 address (as returned by net.Addr().String() for a
net.Listen("tcp", ":1") address) is not yet guaranteed to work. It's
currently OS-dependent.
For some reason it works on Go 1.8+, but it hasn't yet been defined to
work reliably.
Fix the tests for now (since we need to support older Go releases),
even if this might work in the future.
Updates golang/go#18806
Change-Id: I2f0476b1d4f2673ab64ffedfa733f2d92fceb6ff
Reviewed-on: https://go-review.googlesource.com/42496
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
This is a breaking change.
This adds a new hostkey callback which takes the hostname field
restrictions into account when validating host certificates.
Prior to this, a known_hosts file with the following entry
@cert-authority *.example.com ssh-rsa <example.com public key>
would, when passed to knownhosts.New() generate an ssh.HostKeyCallback
that would accept all host certificates signed by the example.com public
key, no matter what host the client was connecting to.
After this change, that known_hosts entry can only be used to validate
host certificates presented when connecting to hosts under *.example.com
This also renames IsAuthority to IsUserAuthority to make its intended
purpose more clear.
Change-Id: I7188a53fdd40a8c0bc21983105317b3498f567bb
Reviewed-on: https://go-review.googlesource.com/41751
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Consider the following code:
var p *int
a := []int{0, 1, 2, 3}
for _, i := range a {
if i == 1 {
p = &i
}
}
fmt.Println(*p) // Prints 3
This prints 3 because the variable i is the exact same variable across
all iterations of the loop. When the address is taken for some specific
iteration, the user's intent is to capture the value of i at that
given loop, but instead the value of i in the last loop is what remains.
A bug this sort occurs in the check logic since the address of the
knownKey is taken, but is changed upon subsequent iterations of the
loop (which happens when there are multiple lines).
Change-Id: Ic626778cdcde3968dcff4fa5e7206274957dcb04
Reviewed-on: https://go-review.googlesource.com/40937
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Fixes a nil pointer dereference that slipped through buildbots because
it was introduced by the last two commits.
Change-Id: Ib269e910956cd8b3b46e217b03fde1b61572260a
Reviewed-on: https://go-review.googlesource.com/40530
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
The normal handshake kicks off with a waitSession(), which guarantees
that we never attempt to send data before the first kex is completed,
but ensuring readPacketsLeft > 0 and writePacketsLeft > 0 helps
understand that thresholds can never cause spurious rekeying at the
start of a connection.
Change-Id: If5bcafcda0c7d16fd21f22c664101ac5f5b487d7
Reviewed-on: https://go-review.googlesource.com/38696
Reviewed-by: Adam Langley <agl@golang.org>
Run-TryBot: Adam Langley <agl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This change breaks backwards compatibility.
MaxAuthTries specifies the maximum number of authentication attempts
permitted per connection. If set to a negative number, the server will
allow unlimited authentication attempts. MaxAuthTries defaults to 6 if
not specified, which is a backwards incompatible change. On exceeding
maximum authentication attempts, the server will send a disconnect
message to the client.
This configuration property mirrors a similar property in sshd_config
and prevents bad actors from continuously trying authentication.
Change-Id: Ic77d2c29ee2fd2ae5c764becf7df91d29d03131b
Reviewed-on: https://go-review.googlesource.com/35230
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Previously, the public key authentication for clients would send an
enquiry to the remote for every key specified before attempting to
authenticate with the server.
Now, we immediately try to authenticate once a valid key is found.
This results in exchanging fewer packets if the valid key is near the
top of the list. If all keys fail, then the number of packets exchanged
by the client and server is unaffected.
For OpenSSH daemon, an enquiry into the validity of a key without
authentication is still recorded as an authentication attempt, so any
clients with more than MaxAuthTries public keys would not be able to
authenticate using the previous implementation. This change will allow
clients to succeed authentication if the successful key is at the start
of the list of keys.
Change-Id: I8ea42caf40c0864752218c3f6934e86b12f5b81a
Reviewed-on: https://go-review.googlesource.com/38890
Reviewed-by: Adam Langley <agl@golang.org>
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 previous attempt would fail in the following scenario:
* select picks "first" kex from requestKex
* read loop receives a remote kex, posts on requestKex (which is now
empty) [*] for sending out a response, and sends pendingKex on startKex.
* select picks pendingKex from startKex, and proceeds to run the key
exchange.
* the posting on requestKex in [*] now triggers a second key exchange.
Fixes#18861.
Change-Id: I443e82f1d04c7f17d1485fdb87072b9feec26aa8
Reviewed-on: https://go-review.googlesource.com/36055
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
The ssh tests currently require 127.0.0.1 to work which isn't
necessarily available everywhere. To fix the source-address tests,
support comma-separated source-address values per the PROTOCOL.certkeys
file:
Comma-separated list of source addresses
from which this certificate is accepted
for authentication. Addresses are
specified in CIDR format (nn.nn.nn.nn/nn
or hhhh::hhhh/nn).
If this option is not present then
certificates may be presented from any
source address.
Change-Id: I87536ff81ffa005c073da103021ebc0dfb12b620
Reviewed-on: https://go-review.googlesource.com/36110
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Run-TryBot: Heschi Kreinick <heschi@google.com>
Since encryption messes up the packets, the wrongly retained packets
look like noise and cause application protocol errors or panics in the
SSH library.
This normally triggers very rarely: the mandatory key exchange doesn't
have parallel writes, so this failure condition would be setup on the
first key exchange, take effect only after the second key exchange.
Fortunately, the tests against openssh exercise this. This change adds
also adds a unittest.
Fixes#18850.
Change-Id: I656c8b94bfb265831daa118f4d614a2f0c65d2af
Reviewed-on: https://go-review.googlesource.com/36056
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
1) Always force a key exchange if we exchange 2^31 packets. In the past
this might not happen if RekeyThreshold was set to a very large
interval.
2) Follow recommendations from RFC 4344 for block ciphers. For AES, we
can encrypt 2^(blocksize/4) blocks under the same keys.
On modern hardware, the previous default of 1Gb could force a key
exchange within ~10 seconds. Since the key exchange takes 3 roundtrips
(send kex init, send DH init, send NEW_KEYS), this is relatively
expensive on high-latency links.
Change-Id: I1297124a307c541b7bf22d814d136ec0c6d8ed97
Reviewed-on: https://go-review.googlesource.com/35410
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>
The initial kex is started from both sides simultaneously, and before,
we could consume the the incoming kex request before we consumed from
our internal channel. This would result in initiating a key exchange
just after completing the initial one, which is not only an extra
delay, but also an error when using OpenSSH (OpenSSH does not support
key exchanges during user authentication).
Change-Id: Ia7e0748ea2bca80ae97d187bcf2931ab6422276b
Reviewed-on: https://go-review.googlesource.com/35851
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>
Use channels and a dedicated write loop for managing the rekeying
process. This lets us collect packets to be written while a key
exchange is in progress.
Previously, the read loop ran the key exchange, and writers would
block if a key exchange was going on. If a reader wrote back a packet
while processing a read packet, it could block, stopping the read
loop, thus causing a deadlock. Such coupled read/writes are inherent
with handling requests that want a response (eg. keepalive,
opening/closing channels etc.). The buffered channels (most channels
have capacity 16) papered over these problems, but under load SSH
connections would occasionally deadlock.
Fixes#18439.
Change-Id: I7c14ff4991fa3100a5d36025125d0cf1119c471d
Reviewed-on: https://go-review.googlesource.com/35012
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
A net.IP may be represented by both by a 4 as well as a 16 byte long
byte slice. Because of this, it is not safe to compare IP addresses
using bytes.Equal as the same IP address using a different internal
representation will produce mismatches.
Change-Id: I0d228771cf363ccfb9532f8bc2a2fc8eff61f6e9
Reviewed-on: https://go-review.googlesource.com/34450
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
911fafb28f made MakeRaw match C's behaviour. This included clearing the
OPOST flag, which means that one now needs to write \r\n for a newline,
otherwise the cursor doesn't move back to the beginning and the terminal
prints a staircase.
(Dear god, we're still emulating line printers.)
This change causes the terminal package to do the required
transformation.
Fixesgolang/go#17364.
Change-Id: Ida15d3cf701a21eaa59161ab61b3ed4dee2ded46
Reviewed-on: https://go-review.googlesource.com/33902
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Spencer Tung
Yasuhiro Matsumoto
Dave Cheney
Han-Wen Nienhuys
Adam Eijdenberg
Catalin Nicutar
Brad Fitzpatrick
Peter Moody
Rick Sayre
Joe Tsai
James Myers
Akihiro Suda
Paul Querna
MiLk
Heschi Kreinick
Adam Langley
Alex Brainman
Peter Morjan
Mikio Hara
Péter Szilágyi
Ryuzo Yamamoto
Dmitry Savintsev