[gentoo-dev] [PATCH] fcaps.eclass: leave permissions alone by default

[Mike Gilbert <floppym@gentoo.org>]

Instead of clobbering the entire file mode, just toggle the suid bit if
needed. In most cases this will result in a world-readable file.

Introduce the FCAPS_DENY_WORLD_READ setting for users who insist on
having their suid binaries unreadable.

Skip calling chown/chmod if the owner/mode is empty. This may be used by
ebuild authors in certain use cases.

Bug: https://bugs.gentoo.org/938164
Signed-off-by: Mike Gilbert <floppym@gentoo.org>
---
 eclass/fcaps.eclass | 35 ++++++++++++++++++++++++++---------
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/eclass/fcaps.eclass b/eclass/fcaps.eclass
index 477e1e954ab8..5cb781a7a75d 100644
--- a/eclass/fcaps.eclass
+++ b/eclass/fcaps.eclass
@@ -1,4 +1,4 @@
-# Copyright 1999-2023 Gentoo Authors
+# Copyright 1999-2024 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 # @ECLASS: fcaps.eclass
@@ -66,6 +66,12 @@ esac
 #
 # Note: If you override pkg_postinst, you must call fcaps_pkg_postinst yourself.
 
+# @ECLASS_VARIABLE: FCAPS_DENY_WORLD_READ
+# @USER_VARIABLE
+# @DEFAULT_UNSET
+# @DESCRIPTION:
+# When set, deny read access on files updated by the fcaps function.
+
 # @FUNCTION: fcaps
 # @USAGE: [-o <owner>] [-g <group>] [-m <mode>] [-M <caps mode>] <capabilities> <file[s]>
 # @DESCRIPTION:
@@ -96,8 +102,13 @@ fcaps() {
 	# Process the user options first.
 	local owner='0'
 	local group='0'
-	local mode='4711'
-	local caps_mode='711'
+	local mode=u+s
+	local caps_mode=
+
+	if [[ -n ${FCAPS_DENY_WORLD_READ} ]]; then
+		mode=u+s,go-r
+		caps_mode=go-r
+	fi
 
 	while [[ $# -gt 0 ]] ; do
 		case $1 in
@@ -137,9 +148,10 @@ fcaps() {
 			# fs doesn't support it, but abort on all others.
 			debug-print "${FUNCNAME}: setting caps '${caps}' on '${file}'"
 
-			# If everything goes well, we don't want the file to be readable
-			# by people.
-			chmod ${caps_mode} "${file}" || die
+			# Remove the read bits if requested.
+			if [[ -n ${caps_mode} ]]; then
+				chmod ${caps_mode} "${file}" || die
+			fi
 
 			if ! out=$(LC_ALL=C setcap "${caps}" "${file}" 2>&1) ; then
 				case ${out} in
@@ -170,9 +182,14 @@ fcaps() {
 		fi
 
 		# If we're still here, setcaps failed.
-		debug-print "${FUNCNAME}: setting owner/mode on '${file}'"
-		chown "${owner}:${group}" "${file}" || die
-		chmod ${mode} "${file}" || die
+		if [[ -n ${owner} || -n ${group} ]]; then
+			debug-print "${FUNCNAME}: setting owner on '${file}'"
+			chown "${owner}:${group}" "${file}" || die
+		fi
+		if [[ -n ${mode} ]]; then
+			debug-print "${FUNCNAME}: setting mode on '${file}'"
+			chmod ${mode} "${file}" || die
+		fi
 	done
 }
 
-- 
2.47.0