Keep XDG_RUNTIME_DIR and WAYLAND_DISPLAY as default

[Unkown000X]

@Duncaen

Keep XDG_RUNTIME_DIR and WAYLAND_DISPLAY as default, just like DISPLAY variable. These are required to open a program that requests a root permission in Wayland.

[ericonr]

XDG_RUNTIME_DIR

This could cause an application running as root to read/write files in a user controlled directory, I don't think that would be ideal. It could considerably change a threat model, and it could also just bother the user because now some file in their runtime dir isn't readable by them. I feel like this should be opt-in.

[Unkown000X]

@Duncaen @ericonr I see. Is there a safe way to do this? I know sudo does this. For example, if it were something like this:

WAYLAND_DISPLAY="${XDG_RUNTIME_DIR}/${WAYLAND_DISPLAY}"

[Unkown000X]

@ericonr

This way env.c can be reorganized. XDG_RUNTIME_DIR is not there. If WAYLAND_DISPLAY or XDG_RUNTIME_DIR is not there, the variable is not set. If XDG_RUNTIME_DIR is not there, WAYLAND_DISPLAY is not written as a full path and therefore it will not work. What do you think? I think this is safe

From b861d070092ee71ac4208f79b699cf7dadd5c154 Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Mon, 3 May 2021 15:42:19 +0200
Subject: [PATCH] Copy WAYLAND_DISPLAY with secure path

This allows to run Wayland clients under doas with proper full path
for WAYLAND_DISPLAY.
---
 doas.1 | 4 +++-
 env.c  | 12 +++++++++++-
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/doas.1 b/doas.1
index a91705e..bd1f543 100644
--- a/doas.1
+++ b/doas.1
@@ -58,8 +58,10 @@ is set to the name of the user executing
 .Nm .
 The variables
 .Ev DISPLAY
-and
+,
 .Ev TERM
+and
+.Ev WAYLAND_DISPLAY
 are inherited from the current environment.
 This behavior may be modified by the config file.
 The working directory is not changed.
diff --git a/env.c b/env.c
index e2286fc..a5b8d7c 100644
--- a/env.c
+++ b/env.c
@@ -91,7 +91,7 @@ createenv(const struct rule *rule, const struct passwd *mypw,
     const struct passwd *targpw)
 {
 	static const char *copyset[] = {
-		"DISPLAY", "TERM",
+		"DISPLAY", "TERM", "WAYLAND_DISPLAY",
 		NULL
 	};
 	struct env *env;
@@ -178,8 +178,18 @@ fillenv(struct env *env, const char **envlist)
 		} else {
 			if (strcmp(name, "PATH") == 0)
 				val = formerpath;
-			else
+			else if (strcmp(name, "WAYLAND_DISPLAY") == 0) {
+				char wayland_buf[256];
+				const char *xdg = getenv("XDG_RUNTIME_DIR");
+				const char *wayland = getenv("WAYLAND_DISPLAY");
+				if (xdg && wayland) {
+					snprintf(wayland_buf, sizeof(wayland_buf), "%s/%s", xdg, wayland);
+					val = wayland_buf;
+				} else {
+					val = getenv(name);
+				}
+			} else
 				val = getenv(name);
 		}
 		/* at last, we have something to insert */
 		if (val) {
-- 
2.39.3
-- 
2.39.3