Bug#1068044: openssh-client: graphical prompting does not work on wayland systems without xwayland

Package: openssh-client
Version: 1:9.7p1-2+b1
Severity: normal
Tags: patch
Forwarded: https://github.com/openssh/openssh-portable/pull/479
X-Debbugs-Cc: Daniel Kahn Gillmor <[email protected]>

When using a wayland graphical environment without xwayland, at least
two different parts of OpenSSH decline to prompt the user graphically,
even if ssh-askpass-gnome is installed.  (and ssh-askpass-gnome works
cleanly on wayland without xwayland).

The two places that i've noticed that don't prompt are:

- when a key has been added to ssh-agent with `-c` the confirmation
  prompt for use doesn't show.

- when a multiplexed ssh session with `ControlMaster=ask` or
  `ControlMaster=autoask` is configured and another ssh session wants to
  connect over it.


In both locations, ssh-askpass isn't used because the environment
variable DISPLAY isn't set.  I would guess that early adopters of
wayland who have declined to run XWayland have all just shrugged and
worked around this by manually setting SSH_ASKPASS_REQUIRE=force, or to
spuriously setting DISPLAY or something like that as a workaround.

But the tools should really be friendlier to this environment.

I think the attached patch, which i've also offered upstream, should
enable this use case.

       --dkg


-- System Information:
Debian Release: trixie/sid
  APT prefers testing-debug
  APT policy: (500, 'testing-debug'), (500, 'testing'), (500, 'stable'), (500, 'oldstable'), (200, 'unstable-debug'), (200, 'unstable'), (1, 'experimental-debug'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 6.6.15-amd64 (SMP w/4 CPU threads; PREEMPT)
Kernel taint flags: TAINT_FIRMWARE_WORKAROUND
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages openssh-client depends on:
ii  adduser           3.137
ii  libc6             2.37-15
ii  libedit2          3.1-20230828-1
ii  libfido2-1        1.14.0-1
ii  libgssapi-krb5-2  1.20.1-5+b1
ii  libselinux1       3.5-2
ii  libssl3t64        3.1.5-1.1
ii  passwd            1:4.13+dfsg1-4
ii  zlib1g            1:1.3.dfsg-3+b1

Versions of packages openssh-client recommends:
ii  xauth  1:1.1.2-1

Versions of packages openssh-client suggests:
pn  keychain                         <none>
pn  libpam-ssh                       <none>
ii  monkeysphere                     0.44-1
ii  ssh-askpass-gnome [ssh-askpass]  1:9.6p1-4

-- no debconf information

From bb3412c842c8c3dc98c1e0643905229ed3fa7a6c Mon Sep 17 00:00:00 2001
From: Daniel Kahn Gillmor <[email protected]>
Date: Thu, 28 Mar 2024 16:22:41 -0400
Subject: [PATCH] Allow ssh-askpass on Wayland by checking for $WAYLAND_DISPLAY

Currently, no part of ssh (including the agent!) will even consider
running ssh-askpass unless $DISPLAY is set.  But some systems run a
graphical environment (e.g. Wayland) where some versions of
ssh-askpass (e.g. ssh-askpass-gnome) will still work just fine.

So expand this baseline check to to permit invoking ssh-askpass if the
sentinel wayland environment variable is present as well.
---
 readpass.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/readpass.c b/readpass.c
index b52f3d6b1..5e5cad29c 100644
--- a/readpass.c
+++ b/readpass.c
@@ -127,8 +127,9 @@ read_passphrase(const char *prompt, int flags)
 	const char *askpass_hint = NULL;
 	const char *s;
 
-	if ((s = getenv("DISPLAY")) != NULL)
-		allow_askpass = *s != '\0';
+	if ((((s = getenv("DISPLAY")) != NULL) && (*s != '\0')) ||
+            (((s = getenv("WAYLAND_DISPLAY")) != NULL) && (*s != '\0')))
+		allow_askpass = 1;
 	if ((s = getenv(SSH_ASKPASS_REQUIRE_ENV)) != NULL) {
 		if (strcasecmp(s, "force") == 0) {
 			use_askpass = 1;
@@ -262,6 +263,7 @@ notify_start(int force_askpass, const char *fmt, ...)
 		goto out;
 	}
 	if (getenv("DISPLAY") == NULL &&
+            getenv("WAYLAND_DISPLAY") == NULL &&
 	    ((s = getenv(SSH_ASKPASS_REQUIRE_ENV)) == NULL ||
 	    strcmp(s, "force") != 0)) {
 		debug3_f("cannot notify: no display");
-- 
2.43.0

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