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From e8e09061f8168f6f105f56fca10b6cd61b9f587a Mon Sep 17 00:00:00 2001
From: Colin Watson <cjwatson@debian.org>
Date: Sun, 9 Feb 2014 16:10:18 +0000
Subject: Various Debian-specific configuration changes
ssh: Enable ForwardX11Trusted, returning to earlier semantics which cause
fewer problems with existing setups (http://bugs.debian.org/237021).
ssh: Set 'SendEnv LANG LC_*' by default (http://bugs.debian.org/264024).
ssh: Enable HashKnownHosts by default to try to limit the spread of ssh
worms.
ssh: Enable GSSAPIAuthentication by default.
sshd: Enable PAM, disable ChallengeResponseAuthentication, and disable
PrintMotd.
sshd: Enable X11Forwarding.
sshd: Set 'AcceptEnv LANG LC_*' by default.
sshd: Change sftp subsystem path to /usr/lib/openssh/sftp-server.
Document all of this.
Author: Russ Allbery <rra@debian.org>
Forwarded: not-needed
Last-Update: 2017-10-04
Patch-Name: debian-config.patch
---
readconf.c | 2 +-
ssh.1 | 21 +++++++++++++++++++++
ssh_config | 6 +++++-
ssh_config.5 | 19 ++++++++++++++++++-
sshd_config | 16 ++++++++++------
sshd_config.5 | 22 ++++++++++++++++++++++
6 files changed, 77 insertions(+), 9 deletions(-)
diff --git a/readconf.c b/readconf.c
index 50349e238..efcf2d628 100644
--- a/readconf.c
+++ b/readconf.c
@@ -1916,7 +1916,7 @@ fill_default_options(Options * options)
if (options->forward_x11 == -1)
options->forward_x11 = 0;
if (options->forward_x11_trusted == -1)
- options->forward_x11_trusted = 0;
+ options->forward_x11_trusted = 1;
if (options->forward_x11_timeout == -1)
options->forward_x11_timeout = 1200;
/*
diff --git a/ssh.1 b/ssh.1
index f8fc26d2a..8a03db952 100644
--- a/ssh.1
+++ b/ssh.1
@@ -768,6 +768,16 @@ directive in
.Xr ssh_config 5
for more information.
.Pp
+(Debian-specific: X11 forwarding is not subjected to X11 SECURITY extension
+restrictions by default, because too many programs currently crash in this
+mode.
+Set the
+.Cm ForwardX11Trusted
+option to
+.Dq no
+to restore the upstream behaviour.
+This may change in future depending on client-side improvements.)
+.Pp
.It Fl x
Disables X11 forwarding.
.Pp
@@ -776,6 +786,17 @@ Enables trusted X11 forwarding.
Trusted X11 forwardings are not subjected to the X11 SECURITY extension
controls.
.Pp
+(Debian-specific: This option does nothing in the default configuration: it
+is equivalent to
+.Dq Cm ForwardX11Trusted No yes ,
+which is the default as described above.
+Set the
+.Cm ForwardX11Trusted
+option to
+.Dq no
+to restore the upstream behaviour.
+This may change in future depending on client-side improvements.)
+.Pp
.It Fl y
Send log information using the
.Xr syslog 3
diff --git a/ssh_config b/ssh_config
index bcb9f153d..1b676fb2c 100644
--- a/ssh_config
+++ b/ssh_config
@@ -17,9 +17,10 @@
# list of available options, their meanings and defaults, please see the
# ssh_config(5) man page.
-# Host *
+Host *
# ForwardAgent no
# ForwardX11 no
+# ForwardX11Trusted yes
# PasswordAuthentication yes
# HostbasedAuthentication no
# GSSAPIAuthentication no
@@ -46,3 +47,6 @@
# VisualHostKey no
# ProxyCommand ssh -q -W %h:%p gateway.example.com
# RekeyLimit 1G 1h
+ SendEnv LANG LC_*
+ HashKnownHosts yes
+ GSSAPIAuthentication yes
diff --git a/ssh_config.5 b/ssh_config.5
index ca0528842..ed6e5d026 100644
--- a/ssh_config.5
+++ b/ssh_config.5
@@ -71,6 +71,22 @@ Since the first obtained value for each parameter is used, more
host-specific declarations should be given near the beginning of the
file, and general defaults at the end.
.Pp
+Note that the Debian
+.Ic openssh-client
+package sets several options as standard in
+.Pa /etc/ssh/ssh_config
+which are not the default in
+.Xr ssh 1 :
+.Pp
+.Bl -bullet -offset indent -compact
+.It
+.Cm SendEnv No LANG LC_*
+.It
+.Cm HashKnownHosts No yes
+.It
+.Cm GSSAPIAuthentication No yes
+.El
+.Pp
The file contains keyword-argument pairs, one per line.
Lines starting with
.Ql #
@@ -690,11 +706,12 @@ elapsed.
.It Cm ForwardX11Trusted
If this option is set to
.Cm yes ,
+(the Debian-specific default),
remote X11 clients will have full access to the original X11 display.
.Pp
If this option is set to
.Cm no
-(the default),
+(the upstream default),
remote X11 clients will be considered untrusted and prevented
from stealing or tampering with data belonging to trusted X11
clients.
diff --git a/sshd_config b/sshd_config
index 86263d713..de9cc9fe2 100644
--- a/sshd_config
+++ b/sshd_config
@@ -57,8 +57,9 @@ AuthorizedKeysFile .ssh/authorized_keys
#PasswordAuthentication yes
#PermitEmptyPasswords no
-# Change to no to disable s/key passwords
-#ChallengeResponseAuthentication yes
+# Change to yes to enable challenge-response passwords (beware issues with
+# some PAM modules and threads)
+ChallengeResponseAuthentication no
# Kerberos options
#KerberosAuthentication no
@@ -81,16 +82,16 @@ AuthorizedKeysFile .ssh/authorized_keys
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
-#UsePAM no
+UsePAM yes
#AllowAgentForwarding yes
#AllowTcpForwarding yes
#GatewayPorts no
-#X11Forwarding no
+X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes
#PermitTTY yes
-#PrintMotd yes
+PrintMotd no
#PrintLastLog yes
#TCPKeepAlive yes
#UseLogin no
@@ -108,8 +109,11 @@ AuthorizedKeysFile .ssh/authorized_keys
# no default banner path
#Banner none
+# Allow client to pass locale environment variables
+AcceptEnv LANG LC_*
+
# override default of no subsystems
-Subsystem sftp /usr/libexec/sftp-server
+Subsystem sftp /usr/lib/openssh/sftp-server
# Example of overriding settings on a per-user basis
#Match User anoncvs
diff --git a/sshd_config.5 b/sshd_config.5
index 44b918463..4c7ee4254 100644
--- a/sshd_config.5
+++ b/sshd_config.5
@@ -56,6 +56,28 @@ Arguments may optionally be enclosed in double quotes
.Pq \&"
in order to represent arguments containing spaces.
.Pp
+Note that the Debian
+.Ic openssh-server
+package sets several options as standard in
+.Pa /etc/ssh/sshd_config
+which are not the default in
+.Xr sshd 8 :
+.Pp
+.Bl -bullet -offset indent -compact
+.It
+.Cm ChallengeResponseAuthentication No no
+.It
+.Cm X11Forwarding No yes
+.It
+.Cm PrintMotd No no
+.It
+.Cm AcceptEnv No LANG LC_*
+.It
+.Cm Subsystem No sftp /usr/lib/openssh/sftp-server
+.It
+.Cm UsePAM No yes
+.El
+.Pp
The possible
keywords and their meanings are as follows (note that
keywords are case-insensitive and arguments are case-sensitive):
|
