nuageinit: implement write_files

write_files is a list of files that should be created at the first boot

each file content can be either plain text or encoded in base64 (note
that cloudinit specify that gzip is supported, but we do not support it
yet.)

All other specifier from cloudinit should work:
by default all files will juste overwrite exesiting files except if
"append" is set to true, permissions, ownership can be specified.
The files are create before packages are being installed and user
created.

if "defer" is set to true then the file is being created after packages
installation and package manupulation.

This feature is requested for KDE's CI.

libexec/nuageinit/nuage.lua

@@ -7,6 +7,39 @@ local unistd = require("posix.unistd")
 local sys_stat = require("posix.sys.stat")
 local lfs = require("lfs")
 
+local function decode_base64(input)
+	local b = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
+	input = string.gsub(input, '[^'..b..'=]', '')
+
+	local result = {}
+	local bits = ''
+
+	-- convert all characters in bits
+	for i = 1, #input do
+		local x = input:sub(i, i)
+		if x == '=' then
+			break
+		end
+		local f = b:find(x) - 1
+		for j = 6, 1, -1 do
+			bits = bits .. (f % 2^j - f % 2^(j-1) > 0 and '1' or '0')
+		end
+	end
+
+	for i = 1, #bits, 8 do
+		local byte = bits:sub(i, i + 7)
+		if #byte == 8 then
+			local c = 0
+			for j = 1, 8 do
+				c = c + (byte:sub(j, j) == '1' and 2^(8 - j) or 0)
+			end
+			table.insert(result, string.char(c))
+		end
+	end
+
+	return table.concat(result)
+end
+
 local function warnmsg(str, prepend)
 	if not str then
 		return
@@ -441,6 +474,58 @@ local function upgrade_packages()
 	return run_pkg_cmd("upgrade")
 end
 
+local function addfile(file, defer)
+	if type(file) ~= "table" then
+		return false, "Invalid object"
+	end
+	if defer and not file.defer then
+		return true
+	end
+	if not defer and file.defer then
+		return true
+	end
+	if not file.path then
+		return false, "No path provided for the file to write"
+	end
+	local content = nil
+	if file.content then
+		if file.encoding then
+			if file.encoding == "b64" or file.encoding == "base64" then
+				content = decode_base64(file.content)
+			else
+				return false, "Unsupported encoding: " .. file.encoding
+			end
+		else
+			content = file.content
+		end
+	end
+	local mode = "w"
+	if file.append then
+		mode = "a"
+	end
+
+	local root = os.getenv("NUAGE_FAKE_ROOTDIR")
+	if not root then
+		root = ""
+	end
+	local filepath = root .. file.path
+	local f = assert(io.open(filepath, mode))
+	if content then
+		f:write(content)
+	end
+	f:close()
+	if file.permissions then
+		-- convert from octal to decimal
+		local perm = tonumber(file.permissions, 8)
+		sys_stat.chmod(file.path, perm)
+	end
+	if file.owner then
+		local owner, group = string.match(file.owner, "([^:]+):([^:]+)")
+		unistd.chown(file.path, owner, group)
+	end
+	return true
+end
+
 local n = {
 	warn = warnmsg,
 	err = errmsg,
@@ -456,7 +541,8 @@ local n = {
 	install_package = install_package,
 	update_packages = update_packages,
 	upgrade_packages = upgrade_packages,
-	addsudo = addsudo
+	addsudo = addsudo,
+	addfile = addfile
 }
 
 return n