From 906c0766df2fec4bd32c316fd1b0d46fded5fc84 Mon Sep 17 00:00:00 2001
From: Scott Anderson <scott@anderso.nz>
Date: Tue, 28 Apr 2020 20:44:05 +1200
Subject: [PATCH] Remove libcap support

This is simply a false sense of security, and is worse than just using
setuid. CAP_SYS_ADMIN is an extremely serious capability that is
effectively as powerful as root.

It also required users to be in the input group, which allows any
process to keylog the entire system.
---
 .builds/alpine.yml           |  1 -
 .builds/archlinux.yml        |  1 -
 .builds/freebsd.yml          |  2 +-
 README.md                    |  1 -
 backend/session/direct-ipc.c | 18 ------------------
 backend/session/meson.build  | 20 --------------------
 meson.build                  |  2 --
 meson_options.txt            |  1 -
 8 files changed, 1 insertion(+), 45 deletions(-)

diff --git a/.builds/alpine.yml b/.builds/alpine.yml
index 6ec7fe99..13221d25 100644
--- a/.builds/alpine.yml
+++ b/.builds/alpine.yml
@@ -2,7 +2,6 @@ image: alpine/edge
 packages:
   - eudev-dev
   - ffmpeg-dev
-  - libcap-dev
   - libinput-dev
   - libxkbcommon-dev
   - mesa-dev
diff --git a/.builds/archlinux.yml b/.builds/archlinux.yml
index 11f0baaf..b3b1a3c0 100644
--- a/.builds/archlinux.yml
+++ b/.builds/archlinux.yml
@@ -2,7 +2,6 @@ image: archlinux
 packages:
   - clang
   - ffmpeg
-  - libcap
   - libinput
   - libxkbcommon
   - mesa
diff --git a/.builds/freebsd.yml b/.builds/freebsd.yml
index 1934d8c7..a0dfc442 100644
--- a/.builds/freebsd.yml
+++ b/.builds/freebsd.yml
@@ -23,5 +23,5 @@ sources:
 tasks:
 - wlroots: |
     cd wlroots
-    meson build -Dauto_features=enabled -Dlogind=disabled -Dlibcap=disabled
+    meson build -Dauto_features=enabled -Dlogind=disabled
     ninja -C build
diff --git a/README.md b/README.md
index f1929a66..bb534d82 100644
--- a/README.md
+++ b/README.md
@@ -55,7 +55,6 @@ Install dependencies:
 * pixman
 * systemd (optional, for logind support)
 * elogind (optional, for logind support on systems without systemd)
-* libcap (optional, for capability support)
 
 If you choose to enable X11 support:
 
diff --git a/backend/session/direct-ipc.c b/backend/session/direct-ipc.c
index 42ca00e1..94f34a88 100644
--- a/backend/session/direct-ipc.c
+++ b/backend/session/direct-ipc.c
@@ -24,23 +24,6 @@
 
 enum { DRM_MAJOR = 226 };
 
-#if WLR_HAS_LIBCAP
-#include <sys/capability.h>
-
-static bool have_permissions(void) {
-	cap_t cap = cap_get_proc();
-	cap_flag_value_t val;
-
-	if (!cap || cap_get_flag(cap, CAP_SYS_ADMIN, CAP_PERMITTED, &val) || val != CAP_SET) {
-		wlr_log(WLR_ERROR, "Do not have CAP_SYS_ADMIN; cannot become DRM master");
-		cap_free(cap);
-		return false;
-	}
-
-	cap_free(cap);
-	return true;
-}
-#else
 static bool have_permissions(void) {
 #ifdef __linux__
 	if (geteuid() != 0) {
@@ -50,7 +33,6 @@ static bool have_permissions(void) {
 #endif
 	return true;
 }
-#endif
 
 static void send_msg(int sock, int fd, void *buf, size_t buf_len) {
 	char control[CMSG_SPACE(sizeof(fd))] = {0};
diff --git a/backend/session/meson.build b/backend/session/meson.build
index 65e4595d..81ff6d85 100644
--- a/backend/session/meson.build
+++ b/backend/session/meson.build
@@ -62,23 +62,3 @@ if logind_found
 	wlr_files += files('logind.c')
 	wlr_deps += logind
 endif
-
-# libcap
-
-msg = []
-if get_option('libcap').enabled()
-	msg += 'Install "libcap" or pass "-Dlibcap=disabled".'
-endif
-if not get_option('libcap').disabled()
-	msg += 'Required for POSIX capability support (Not needed if using logind).'
-endif
-
-libcap = dependency('libcap',
-	required: get_option('libcap'),
-	not_found_message: '\n'.join(msg),
-)
-if libcap.found()
-	conf_data.set10('WLR_HAS_LIBCAP', true)
-	wlr_deps += libcap
-endif
-
diff --git a/meson.build b/meson.build
index 8958ad16..1a160208 100644
--- a/meson.build
+++ b/meson.build
@@ -80,7 +80,6 @@ else
 endif
 
 conf_data = configuration_data()
-conf_data.set10('WLR_HAS_LIBCAP', false)
 conf_data.set10('WLR_HAS_SYSTEMD', false)
 conf_data.set10('WLR_HAS_ELOGIND', false)
 conf_data.set10('WLR_HAS_X11_BACKEND', false)
@@ -170,7 +169,6 @@ wlroots = declare_dependency(
 meson.override_dependency('wlroots', wlroots)
 
 summary({
-	'libcap': conf_data.get('WLR_HAS_LIBCAP', 0),
 	'systemd': conf_data.get('WLR_HAS_SYSTEMD', 0),
 	'elogind': conf_data.get('WLR_HAS_ELOGIND', 0),
 	'xwayland': conf_data.get('WLR_HAS_XWAYLAND', 0),
diff --git a/meson_options.txt b/meson_options.txt
index ae6f5c0b..894113e7 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -1,4 +1,3 @@
-option('libcap', type: 'feature', value: 'auto', description: 'Enable support for rootless session via capabilities (cap_sys_admin)')
 option('logind', type: 'feature', value: 'auto', description: 'Enable support for rootless session via logind')
 option('logind-provider', type: 'combo', choices: ['auto', 'systemd', 'elogind'], value: 'auto', description: 'Provider of logind support library')
 option('xcb-errors', type: 'feature', value: 'auto', description: 'Use xcb-errors util library')