upstream commit

remember which public keys have been used for
 authentication and refuse to accept previously-used keys.

This allows AuthenticationMethods=publickey,publickey to require
that users authenticate using two _different_ pubkeys.

ok markus@

1 files changed, 14 insertions, 2 deletions

diff --git a/sshd_config.5 b/sshd_config.5
index 938ba2f1a..d2ab28136 100644
--- a/sshd_config.5
+++ b/sshd_config.5
@@ -33,8 +33,8 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.\" $OpenBSD: sshd_config.5,v 1.184 2014/12/21 23:35:14 jmc Exp $
-.Dd $Mdocdate: December 21 2014 $
+.\" $OpenBSD: sshd_config.5,v 1.185 2014/12/22 07:51:30 djm Exp $
+.Dd $Mdocdate: December 22 2014 $
 .Dt SSHD_CONFIG 5
 .Os
 .Sh NAME
@@ -210,6 +210,18 @@ would restrict keyboard interactive authentication to the
 .Dq bsdauth
 device.
 .Pp
+If the
+.Dq publickey
+method is listed more than one,
+.Xr sshd 8
+verifies that keys that have been used successfully are not reused for
+subsequent authentications.
+For example, an
+.Cm AuthenticationMethods
+of
+.Dq publickey,publickey
+will require successful authentication using two different public keys.
+.Pp
 This option is only available for SSH protocol 2 and will yield a fatal
 error if enabled if protocol 1 is also enabled.
 Note that each authentication method listed should also be explicitly enabled