nuageinit: Ignore non-existent groups

In cloud-init, when a group specified in the 'users.{index}.groups' parameter
does not exist, it is ignored, but the user is created anyway. In the case of
nuageinit, it exits with an exception, since pw(8) expects each group to exist.

Reviewed by:		bapt@
Approved by:		bapt@
Differential Revision:	https://reviews.freebsd.org/D52718

libexec/nuageinit/nuage.lua

@@ -139,6 +139,58 @@ local function splitlist(list)
 	return ret
 end
 
+local function splitlines(s)
+	local ret = {}
+
+	for line in string.gmatch(s, "[^\n]+") do
+		ret[#ret + 1] = line
+	end
+
+	return ret
+end
+
+local function getgroups()
+	local ret = {}
+
+	local root = os.getenv("NUAGE_FAKE_ROOTDIR")
+	local cmd = "pw "
+	if root then
+		cmd = cmd .. "-R " .. root .. " "
+	end
+
+	local f = io.popen(cmd .. "groupshow -a 2> /dev/null | cut -d: -f1")
+	local groups = f:read("*a")
+	f:close()
+
+	return splitlines(groups)
+end
+
+local function checkgroup(group)
+	local groups = getgroups()
+
+	for _, group2chk in ipairs(groups) do
+		if group == group2chk then
+			return true
+		end
+	end
+
+	return false
+end
+
+local function purge_group(groups)
+	local ret = {}
+
+	for _, group in ipairs(groups) do
+		if checkgroup(group) then
+			ret[#ret + 1] = group
+		else
+			warnmsg("ignoring non-existent group '" .. group .. "'")
+		end
+	end
+
+	return ret
+end
+
 local function adduser(pwd)
 	if (type(pwd) ~= "table") then
 		warnmsg("Argument should be a table")
@@ -164,7 +216,14 @@ local function adduser(pwd)
 	local extraargs = ""
 	if pwd.groups then
 		local list = splitlist(pwd.groups)
-		extraargs = " -G " .. table.concat(list, ",")
+		-- pw complains if the group does not exist, so if the user
+		-- specifies one that cannot be found, nuageinit will generate
+		-- an exception and exit, unlike cloud-init, which only issues
+		-- a warning but creates the user anyway.
+		list = purge_group(list)
+		if #list > 0 then
+			extraargs = " -G " .. table.concat(list, ",")
+		end
 	end
 	-- pw will automatically create a group named after the username
 	-- do not add a -g option in this case