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>
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 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>
Added support for parsing the "new" openssh private key format.
(ed25519 keys only in this format for now)
Signing and verifying functions now work with ed25519 keys.
ed25519 can now be accepted by the server to authenticate a client.
ed25519 can now be accepted by a client as a server host key.
Related documentation used:
https://www.ietf.org/archive/id/draft-bjh21-ssh-ed25519-02.txt
Change-Id: I84385f24d666fea08de21f980f78623f7bff8007
Reviewed-on: https://go-review.googlesource.com/22512
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
Currently using go-fuzz with code using golang.org/x/crypto/ssh fails
because it passes CertTimeInfinity to an interface{} and automatically
tries to use an int, which overflows and results in a compile error.
This change adds a no-op type conversion inside the function which
makes things compile with go-fuzz.
Change-Id: Iade0c0df7e20cbac4928480fad3e44c831e1e00a
Reviewed-on: https://go-review.googlesource.com/11285
Reviewed-by: Adam Langley <agl@golang.org>
Attention - BREAKING change for the certificates generated with
the previous versions of crypto/ssh! Need to regenerate
certificates with a version of crypto/ssh library including
this fix.
[PROTOCOL.cerkeys] requires two length fields for non-empty
values of critical options (or extensions - but those are
currently always empty) - see
https://bugzilla.mindrot.org/show_bug.cgi?id=2389.
Add SSH-conform handling of such composite values in marshalTuples
and parseTuples and related test (TestParseCertWithOptions) parsing
a certificate created with ssh-keygen which includes critical options.
Fixes#10569
Change-Id: Iecbfca67a66668880635141c72bc5fc370a9c112
Reviewed-on: https://go-review.googlesource.com/9375
Reviewed-by: Adam Langley <agl@golang.org>
Run-TryBot: Adam Langley <agl@golang.org>
The change to add the PublicKey interface accidentally caused certificate handling to expect an extra copy of the private key algorithm name in the binary representation. This change adapts a suitable parsing API and adds a test to ensure that cert handling isn't easily broken in the future.
R=agl, hanwen, jmpittman
CC=golang-dev
https://golang.org/cl/13272055
Simplify MarshalAuthorizedKey by using the algoName func.
Make the algoName func be very specific about supported key types in openssh certs.
Generalize some of the commentary that previously mentioned specific key types.
R=agl, dave
CC=golang-dev
https://golang.org/cl/6938067
Export key and certificate algorithm names.
Switch from string literals over to using the constants for any key/cert algorithm references.
Make URL references visible in the godoc web display.
Standardize url reference names with surrounding [].
R=dave, agl, jonathan.mark.pittman
CC=golang-dev
https://golang.org/cl/6944047
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
Adam Eijdenberg
Peter Moody
Han-Wen Nienhuys
Martin Garton
Taru Karttunen
Dmitry Savintsev
Adam Langley
Jonathan Pittman
JP Sugarbroad