Seems the OpenSSH server running on windows fails keyboard-interactive
auth this way without sending any prompt to client. In such case the
golang ssh client should not retry keyboard-interactive auth when the
auth method is wrapped in a RetryableAuthMethod(). Rather the auth
method should be immediately marked as tried&failed and the client auth
process should move on to next available and acceptable auth method.
Fixesgolang/go#67855
Change-Id: I6c64ae58ff8325774e37af716601b112f8833d8f
GitHub-Last-Rev: 7fafc4d1c81284b31000d7d6ccadd934dda26d24
GitHub-Pull-Request: golang/crypto#297
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/590956
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Nicola Murino <nicola.murino@gmail.com>
Reviewed-by: Nicola Murino <nicola.murino@gmail.com>
After adding support for rsa-sha2-256/512 on the server side some edge
cases started to arise with old clients:
1) public key authentication with gpg-agent < 2.2.6 fails because we
receive ssh-rsa as signature format and rsa-sha2-256 or rsa-sha2-512
as algorithm.
This is a bug in gpg-agent fixed in this commit:
https://github.com/gpg/gnupg/commit/80b775bdbb852aa4a80292c9357e5b1876110c00
2) certificate authentication fails with OpenSSH 7.2-7.7 because we
receive ssh-rsa-cert-v01@openssh.com as algorithm and rsa-sha2-256
or rsa-sha2-512 as signature format.
This patch is based on CL 412854 and has been tested with every version
of OpenSSH from 7.1 to 7.9 and OpenSSH 9.3.
Fixesgolang/go#53391
Change-Id: Id71f596f73d84efb5c76d6d5388432cccad3e3b1
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/506835
Auto-Submit: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Run-TryBot: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Roland Shoemaker <roland@golang.org>
CL 220037 had implemented support for host authentication using
rsa-sha2-256/512, but not client public key authentication. OpenSSH
disabled the SHA-1 based ssh-rsa by default in version 8.8 (after
pre-announcing it in versions 8.2, 8.3, 8.4, 8.5, 8.6, and 8.7) although
some distributions re-enable it. GitHub will start rejecting ssh-rsa for
keys uploaded before November 2, 2021 on March 15, 2022.
https://github.blog/2021-09-01-improving-git-protocol-security-github/
The server side already worked, as long as the client selected one of
the SHA-2 algorithms, because the signature flowed freely to Verify.
There was however nothing verifying that the signature algorithm matched
the advertised one. The comment suggested the check was being performed,
but it got lost back in CL 86190043. Not a security issue because the
signature had to pass the callback's Verify method regardless, and both
values were checked to be acceptable.
Tested with OpenSSH 8.8 configured with "PubkeyAcceptedKeyTypes -ssh-rsa"
and no application-side changes.
The Signers returned by ssh/agent (when backed by an agent client)
didn't actually implement AlgorithmSigner but ParameterizedSigner, an
interface defined in an earlier version of CL 123955.
Updates golang/go#49269Fixesgolang/go#39885
For golang/go#49952
Change-Id: I13b41db8041f1112a70f106c55f077b904b12cb8
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/392394
Trust: Filippo Valsorda <filippo@golang.org>
Run-TryBot: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Add the diffie-hellman-group-exchange-sha256 defined in RFC 4419 to
the list of supported key exchange algorithms for ssh.
The server half is only a minimal implementation to satisfy the automated tests.
Fixesgolang/go#17230
Change-Id: I25880a564347fd9b4738dd2ed1e347cd5d2e21bb
GitHub-Last-Rev: 9f0b8d02c0c96e9baf00cdf1cf063ff834245443
GitHub-Pull-Request: golang/crypto#87
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/174257
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Previously, this would return the default error "no auth passed yet".
Not only is the new error more specific, it makes it easier to verify
the control flow of server authentication code.
Change-Id: I6c8de4e3f91da74274acbe9d87ec4f6158b4a94f
Reviewed-on: https://go-review.googlesource.com/c/142897
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
yet.
Since ServerAuthError returns all errors collected during the
userAuthLoop, it will always include the generic error "no auth passed
yet" (assuming the connection fails).
Change-Id: I5f6c67f3f0762b023618178d4028600d2b6c9253
Reviewed-on: https://go-review.googlesource.com/92737
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
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>
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>
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 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>
RSA and DSA keys if encrypted have the
phrase ENCRYPTED in their Proc-Type block
header according to RFC 1421 Section 4.6.1.1.
This CL checks for that phrase and errors out
if we encounter it, since we don't yet have
decryption of encrypted private keys.
Fixesgolang/go#6650
Change-Id: I5b157716a2f93557d289af5f62994234a2e7a0ed
Reviewed-on: https://go-review.googlesource.com/29676
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
The current behaviour of the crypto/ssh server implementation is to
remove the username from ConnMetadata if the connection is done without
authentication (NoClientAuth). This appears to be a bug.
This behaviour is different from other SSH server implementations like
for example Paramiko (Python) which keeps the username.
Additionally RFC4252 (https://www.ietf.org/rfc/rfc4252.txt) section
5 states the username has to be included in every USERAUTH message.
Change-Id: I27fa50db92eb535e90fe088453faa6f2a76ee31f
Reviewed-on: https://go-review.googlesource.com/27612
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This failure is tracked already. Remove it from the dashboard
while it's fixed so it doesn't hide more interesting failures.
Updates golang/go#15198
Change-Id: Ib48d1e37ac97914ac082b2602c812151147393e4
Reviewed-on: https://go-review.googlesource.com/24986
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Adds a new AuthMethod called "RetryableAuthMethod" which decorates any
other authmethod, allowing it to be retried up to maxTries before
aborting.
Fixes#16077
Change-Id: Ie310c24643e53dca4fa452750a69936674906484
Reviewed-on: https://go-review.googlesource.com/24156
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
The error message reported by the ssh client when it can't find a
"cipher" in common between the client and server was overly vague. This
adds more detailed error messages to findAgreedAlgorithms so that the
user can more easily identify which of the components can't reach
agreement.
Change-Id: I4d985e92fea964793213e5600b52b3141e712000
Reviewed-on: https://go-review.googlesource.com/13817
Reviewed-by: Adam Langley <agl@golang.org>
Fixesgolang/go#4285.
Adding a new cipher that is supported by the remote end, but not supported by our client causes that cipher to be considered a valid candidate. This fails later in setupKeys when there is no cipherModes configuration.
In summary, unsupported ciphers cannot be willed into existence by adding them to the client config. This change enforces this.
R=golang-dev, agl
CC=golang-dev
https://golang.org/cl/6780047
These are the cosmetic cleanups from the bits of code that I
rereviewed.
1) stringLength now takes a int; the length of the string. Too many
callers were allocating with stringLength([]byte(s)) and
stringLength only needs to call len().
2) agent.go now has sendAndReceive to remove logic that was
duplicated.
3) We now reject negative DH values
4) We now reject empty packets rather than crashing.
R=dave, jonathan.mark.pittman
CC=golang-dev
https://golang.org/cl/6061052
Also, add support for hmac-sha1.
At the suggestion of AGL hmac-md5, and hmac-md5-96
support was not included.
Fixesgolang/go#3095.
R=golang-dev, agl, huin
CC=golang-dev
https://golang.org/cl/5696065
Everywhere else in the code base, when we have an interface{} which is
a stand in for a public key, we use *foo.PublicKey rather than
foo.PublicKey. This change makes ssh reflect that.
R=dave, r
CC=golang-dev
https://golang.org/cl/5686067
Nicola Murino
cuishuang
samiponkanen
Ian Lance Taylor
Lucas Bremgartner
yanweizhi
Han-Wen Nienhuys
Brad Fitzpatrick
Spencer Tung
Peter Moody
James Myers
Heschi Kreinick
Emmanuel Odeke
Sven Blumenstein
Martin Hamrle
Jamie Beverly
Thomas Desrosiers
Adam Langley
Jonathan Pittman
Dave Cheney
Fazlul Shahriar
Daniel Theophanes