nuageinit: Add wrappers for chmod and chown

In the wrappers, check for errors and abort if one is raised.  At some
point it may be useful to have a mechanism to ignore errors, but I'm not
sure yet how that should look.

For chmod, let the mode be specified as an octal number, otherwise it's
hard to understand what's happening.  Note that this must be specified
as a string, otherwise tonumber() will raise an error.

Reviewed by:	bapt
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D51159

libexec/nuageinit/nuage.lua

@@ -56,6 +56,21 @@ local function errmsg(str, prepend)
 	os.exit(1)
 end
 
+local function chmod(path, mode)
+	local mode = tonumber(mode, 8)
+	local _, err, msg = sys_stat.chmod(path, mode)
+	if err then
+		errmsg("chmod(" .. path .. ", " .. mode .. ") failed: " .. msg)
+	end
+end
+
+local function chown(path, owner, group)
+	local _, err, msg = unistd.chown(path, owner, group)
+	if err then
+		errmsg("chown(" .. path .. ", " .. owner .. ", " .. group .. ") failed: " .. msg)
+	end
+end
+
 local function dirname(oldpath)
 	if not oldpath then
 		return nil
@@ -252,12 +267,12 @@ local function addsshkey(homedir, key)
 	f:write(key .. "\n")
 	f:close()
 	if chownak then
-		sys_stat.chmod(ak_path, 384)
-		unistd.chown(ak_path, dirattrs.uid, dirattrs.gid)
+		chmod(ak_path, "0600")
+		chown(ak_path, dirattrs.uid, dirattrs.gid)
 	end
 	if chowndotssh then
-		sys_stat.chmod(dotssh_path, 448)
-		unistd.chown(dotssh_path, dirattrs.uid, dirattrs.gid)
+		chmod(dotssh_path, "0700")
+		chown(dotssh_path, dirattrs.uid, dirattrs.gid)
 	end
 end
 
@@ -296,10 +311,10 @@ local function addsudo(pwd)
 	end
 	f:close()
 	if chmodsudoers then
-		sys_stat.chmod(sudoers, 416)
+		chmod(sudoers, "0640")
 	end
 	if chmodsudoersd then
-		sys_stat.chmod(sudoers, 480)
+		chmod(sudoers, "0740")
 	end
 end
 
@@ -521,16 +536,14 @@ local function addfile(file, defer)
 	end
 	f:close()
 	if file.permissions then
-		-- convert from octal to decimal
-		local perm = tonumber(file.permissions, 8)
-		sys_stat.chmod(filepath, perm)
+		chmod(filepath, file.permissions)
 	end
 	if file.owner then
 		local owner, group = string.match(file.owner, "([^:]+):([^:]+)")
 		if not owner then
 			owner = file.owner
 		end
-		unistd.chown(filepath, owner, group)
+		chown(filepath, owner, group)
 	end
 	return true
 end
@@ -538,6 +551,8 @@ end
 local n = {
 	warn = warnmsg,
 	err = errmsg,
+	chmod = chmod,
+	chown = chown,
 	dirname = dirname,
 	mkdir_p = mkdir_p,
 	sethostname = sethostname,