nuageinit: use single-quote shell escaping for hostname in rc.conf.d

The hostname value was written inside double quotes in
/etc/rc.conf.d/hostname. POSIX shell performs command substitution
inside double quotes, so a hostname containing $() or backticks would
be executed when the file is sourced (e.g., by rc(8)).

Switch to using the existing shell_escape() helper, which wraps values
in single quotes. In POSIX shell, single-quoted strings are completely
literal — no expansion or substitution of any kind is performed.

While the hostname is already validated to contain only
[a-zA-Z0-9.-], this change provides defense-in-depth so the output
format is safe regardless of future validation changes.

Reported by:	Yazdan Soltani <yazdan.soltani@gmail.com>

libexec/nuageinit/nuage.lua

@@ -187,7 +187,7 @@ local function sethostname(hostname)
 		warnmsg("Impossible to open " .. hostnamepath .. ":" .. err)
 		return
 	end
-	f:write('hostname="' .. hostname:gsub('"', '\\"') .. '"\n')
+	f:write("hostname=" .. shell_escape(hostname) .. "\n")
 	f:close()
 end
 

libexec/nuageinit/tests/nuage.sh

@@ -33,7 +33,7 @@ sethostname_body()
 	if [ ! -f etc/rc.conf.d/hostname ]; then
 		atf_fail "hostname not written"
 	fi
-	atf_check -o inline:"hostname=\"myhostname\"\n" cat etc/rc.conf.d/hostname
+	atf_check -o inline:"hostname='myhostname'\n" cat etc/rc.conf.d/hostname
 }
 
 addsshkey_body()

libexec/nuageinit/tests/nuageinit.sh

@@ -80,13 +80,13 @@ nocloud_body()
 	atf_check -s exit:1 -e match:"nuageinit: error parsing nocloud.*" /usr/libexec/nuageinit "${PWD}"/media/nuageinit/ nocloud
 	printf "instance-id: iid-local01\nlocal-hostname: cloudimg\n" > "${PWD}"/media/nuageinit/meta-data
 	atf_check -s exit:0 /usr/libexec/nuageinit "${PWD}"/media/nuageinit nocloud
-	atf_check -o inline:"hostname=\"cloudimg\"\n" cat etc/rc.conf.d/hostname
+	atf_check -o inline:"hostname='cloudimg'\n" cat etc/rc.conf.d/hostname
 	cat > media/nuageinit/meta-data << EOF
 instance-id: iid-local01
 hostname: myhost
 EOF
 	atf_check -s exit:0 /usr/libexec/nuageinit "${PWD}"/media/nuageinit nocloud
-	atf_check -o inline:"hostname=\"myhost\"\n" cat etc/rc.conf.d/hostname
+	atf_check -o inline:"hostname='myhost'\n" cat etc/rc.conf.d/hostname
 }
 
 nocloud_userdata_script_body()
@@ -250,7 +250,7 @@ config2_body()
 }
 EOF
 	atf_check /usr/libexec/nuageinit "${PWD}"/media/nuageinit config-2
-	atf_check -o inline:"hostname=\"cloudimg\"\n" cat etc/rc.conf.d/hostname
+	atf_check -o inline:"hostname='cloudimg'\n" cat etc/rc.conf.d/hostname
 }
 
 config2_pubkeys_head()
@@ -1307,7 +1307,7 @@ echo "multipart script executed"
 --==BOUNDARY==--
 EOF
 	atf_check -o empty /usr/libexec/nuageinit "${PWD}"/media/nuageinit config-2
-	atf_check -o inline:"hostname=\"multipart-host\"\n" cat etc/rc.conf.d/hostname
+	atf_check -o inline:"hostname='multipart-host'\n" cat etc/rc.conf.d/hostname
 	atf_check -o inline:"#!/bin/sh\necho \"multipart script executed\"\n" cat var/cache/nuageinit/multipart_script
 	test -x var/cache/nuageinit/multipart_script || atf_fail "multipart_script not executable"
 	true
@@ -1376,13 +1376,13 @@ fqdn: host.domain.tld
 hostname: host
 EOF
 	atf_check -o empty /usr/libexec/nuageinit "${PWD}"/media/nuageinit config-2
-	atf_check -o inline:"hostname=\"host.domain.tld\"\n" cat ${PWD}/etc/rc.conf.d/hostname
+	atf_check -o inline:"hostname='host.domain.tld'\n" cat ${PWD}/etc/rc.conf.d/hostname
 	cat > media/nuageinit/user_data <<EOF
 #cloud-config
 hostname: host
 EOF
 	atf_check -o empty /usr/libexec/nuageinit "${PWD}"/media/nuageinit config-2
-	atf_check -o inline:"hostname=\"host\"\n" cat ${PWD}/etc/rc.conf.d/hostname
+	atf_check -o inline:"hostname='host'\n" cat ${PWD}/etc/rc.conf.d/hostname
 }
 
 config2_userdata_encode_base64_body()

libexec/nuageinit/tests/sethostname.lua

@@ -20,7 +20,7 @@ local function check_hostname(expected)
 	end
 	local content = f:read("*a")
 	f:close()
-	local expected_content = 'hostname="' .. expected:gsub('"', '\\"') .. '"\n'
+	local expected_content = "hostname=" .. n.shell_escape(expected) .. "\n"
 	if content ~= expected_content then
 		n.err("hostname mismatch: got '" .. content ..
 		    "', expected '" .. expected_content .. "'")