From c7fcfd5a2dfff5bf99ed00515173d2f8917f9c57 Mon Sep 17 00:00:00 2001
From: Natanael Copa <ncopa@alpinelinux.org>
Date: Thu, 13 Dec 2012 21:28:59 +0100
Subject: auth: add inital authentication modules and a test

---
 auth/shadow.lua | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 auth/shadow.lua

(limited to 'auth/shadow.lua')

diff --git a/auth/shadow.lua b/auth/shadow.lua
new file mode 100644
index 0000000..3a4a534
--- /dev/null
+++ b/auth/shadow.lua
@@ -0,0 +1,70 @@
+
+local posix = require('posix')
+local db = {}
+
+db.file = "/etc/shadow"
+db.fields = { 'name', 'passwd', 'lastchanged', 'minimum', 'maximum', 'warn', 'inactive', 'expire', 'dummy' }
+
+function db.splitent(line)
+	local ent = {}
+	local i = 1
+	for value in string.gmatch(line or "", "([^:]*):?") do
+		ent[db.fields[i]] = value
+		i = i + 1
+	end
+	return ent
+end
+
+function db.getent(username)
+	local f = io.open(db.file)
+	if f == nil then
+		return nil
+	end
+	for line in f:lines() do
+		local ent = db.splitent(line)
+		if ent.name == username then
+			f:close()
+			return ent
+		end
+	end
+	f:close()
+	return nil, db.file..": user '"..tostring(username).."' not found"
+end
+
+function db.verify_passwd(cleartext, pwhash)
+	--[[
+	from man crypt(3):
+
+	If  salt is a character string starting with the characters "$id$" fol-
+	lowed by a string terminated by "$":
+
+	      $id$salt$encrypted
+
+	then instead of using the DES machine,  id  identifies  the  encryption
+	method  used  and  this  then  determines  how the rest of the password
+	string is interpreted.  The following values of id are supported:
+
+	      ID  | Method
+	      ---------------------------------------------------------
+	      1   | MD5
+	      2a  | Blowfish (not in mainline glibc; added in some
+		  | Linux distributions)
+	      5   | SHA-256 (since glibc 2.7)
+	      6   | SHA-512 (since glibc 2.7)
+	]]--
+	local algo_salt, hash = string.match(pwhash, "^(%$%d%$[a-zA-Z0-9./]+%$)(.*)")
+	local userhash = posix.crypt(cleartext, algo_salt)
+	print("user hash:", userhash)
+	print("db hash:", pwhash)
+	return (pwhash == userhash)
+end
+
+function db.authenticate(username, cleartextpw)
+	local ent = db.getent(username)
+	if ent == nil then
+		return nil, tostring(username)..": no such user"
+	end
+	return db.verify_passwd(cleartextpw, ent.passwd)
+end
+
+return db
-- 
cgit v1.2.3