1-- This script may be used with the auth-filter. Be sure to configure it as you wish.
  2--
  3-- Requirements:
  4-- 	luacrypto >= 0.3
  5-- 	<http://mkottman.github.io/luacrypto/>
  6-- 	luaposix
  7-- 	<https://github.com/luaposix/luaposix>
  8--
  9local sysstat = require("posix.sys.stat")
 10local unistd = require("posix.unistd")
 11local crypto = require("crypto")
 12
 13
 14--
 15--
 16-- Configure these variables for your settings.
 17--
 18--
 19
 20-- A list of password protected repositories along with the users who can access them.
 21local protected_repos = {
 22	glouglou	= { laurent = true, jason = true },
 23	qt		= { jason = true, bob = true }
 24}
 25
 26-- Please note that, in production, you'll want to replace this simple lookup
 27-- table with either a table of salted and hashed passwords (using something
 28-- smart like scrypt), or replace this table lookup with an external support,
 29-- such as consulting your system's pam / shadow system, or an external
 30-- database, or an external validating web service. For testing, or for
 31-- extremely low-security usage, you may be able, however, to get away with
 32-- compromising on hardcoding the passwords in cleartext, as we have done here.
 33local users = {
 34	jason		= "secretpassword",
 35	laurent		= "s3cr3t",
 36	bob		= "ilikelua"
 37}
 38
 39-- Set this to a path this script can write to for storing a persistent
 40-- cookie secret, which should be guarded.
 41local secret_filename = "/var/cache/cgit/auth-secret"
 42
 43--
 44--
 45-- Authentication functions follow below. Swap these out if you want different authentication semantics.
 46--
 47--
 48
 49-- Sets HTTP cookie headers based on post and sets up redirection.
 50function authenticate_post()
 51	local password = users[post["username"]]
 52	local redirect = validate_value("redirect", post["redirect"])
 53
 54	if redirect == nil then
 55		not_found()
 56		return 0
 57	end
 58
 59	redirect_to(redirect)
 60
 61	-- Lua hashes strings, so these comparisons are time invariant.
 62	if password == nil or password ~= post["password"] then
 63		set_cookie("cgitauth", "")
 64	else
 65		-- One week expiration time
 66		local username = secure_value("username", post["username"], os.time() + 604800)
 67		set_cookie("cgitauth", username)
 68	end
 69
 70	html("\n")
 71	return 0
 72end
 73
 74
 75-- Returns 1 if the cookie is valid and 0 if it is not.
 76function authenticate_cookie()
 77	accepted_users = protected_repos[cgit["repo"]]
 78	if accepted_users == nil then
 79		-- We return as valid if the repo is not protected.
 80		return 1
 81	end
 82
 83	local username = validate_value("username", get_cookie(http["cookie"], "cgitauth"))
 84	if username == nil or not accepted_users[username:lower()] then
 85		return 0
 86	else
 87		return 1
 88	end
 89end
 90
 91-- Prints the html for the login form.
 92function body()
 93	html("<h2>Authentication Required</h2>")
 94	html("<form method='post' action='")
 95	html_attr(cgit["login"])
 96	html("'>")
 97	html("<input type='hidden' name='redirect' value='")
 98	html_attr(secure_value("redirect", cgit["url"], 0))
 99	html("' />")
100	html("<table>")
101	html("<tr><td><label for='username'>Username:</label></td><td><input id='username' name='username' autofocus /></td></tr>")
102	html("<tr><td><label for='password'>Password:</label></td><td><input id='password' name='password' type='password' /></td></tr>")
103	html("<tr><td colspan='2'><input value='Login' type='submit' /></td></tr>")
104	html("</table></form>")
105
106	return 0
107end
108
109
110
111--
112--
113-- Wrapper around filter API, exposing the http table, the cgit table, and the post table to the above functions.
114--
115--
116
117local actions = {}
118actions["authenticate-post"] = authenticate_post
119actions["authenticate-cookie"] = authenticate_cookie
120actions["body"] = body
121
122function filter_open(...)
123	action = actions[select(1, ...)]
124
125	http = {}
126	http["cookie"] = select(2, ...)
127	http["method"] = select(3, ...)
128	http["query"] = select(4, ...)
129	http["referer"] = select(5, ...)
130	http["path"] = select(6, ...)
131	http["host"] = select(7, ...)
132	http["https"] = select(8, ...)
133
134	cgit = {}
135	cgit["repo"] = select(9, ...)
136	cgit["page"] = select(10, ...)
137	cgit["url"] = select(11, ...)
138	cgit["login"] = select(12, ...)
139
140end
141
142function filter_close()
143	return action()
144end
145
146function filter_write(str)
147	post = parse_qs(str)
148end
149
150
151--
152--
153-- Utility functions based on keplerproject/wsapi.
154--
155--
156
157function url_decode(str)
158	if not str then
159		return ""
160	end
161	str = string.gsub(str, "+", " ")
162	str = string.gsub(str, "%%(%x%x)", function(h) return string.char(tonumber(h, 16)) end)
163	str = string.gsub(str, "\r\n", "\n")
164	return str
165end
166
167function url_encode(str)
168	if not str then
169		return ""
170	end
171	str = string.gsub(str, "\n", "\r\n")
172	str = string.gsub(str, "([^%w ])", function(c) return string.format("%%%02X", string.byte(c)) end)
173	str = string.gsub(str, " ", "+")
174	return str
175end
176
177function parse_qs(qs)
178	local tab = {}
179	for key, val in string.gmatch(qs, "([^&=]+)=([^&=]*)&?") do
180		tab[url_decode(key)] = url_decode(val)
181	end
182	return tab
183end
184
185function get_cookie(cookies, name)
186	cookies = string.gsub(";" .. cookies .. ";", "%s*;%s*", ";")
187	return url_decode(string.match(cookies, ";" .. name .. "=(.-);"))
188end
189
190
191--
192--
193-- Cookie construction and validation helpers.
194--
195--
196
197local secret = nil
198
199-- Loads a secret from a file, creates a secret, or returns one from memory.
200function get_secret()
201	if secret ~= nil then
202		return secret
203	end
204	local secret_file = io.open(secret_filename, "r")
205	if secret_file == nil then
206		local old_umask = sysstat.umask(63)
207		local temporary_filename = secret_filename .. ".tmp." .. crypto.hex(crypto.rand.bytes(16))
208		local temporary_file = io.open(temporary_filename, "w")
209		if temporary_file == nil then
210			os.exit(177)
211		end
212		temporary_file:write(crypto.hex(crypto.rand.bytes(32)))
213		temporary_file:close()
214		unistd.link(temporary_filename, secret_filename) -- Intentionally fails in the case that another process is doing the same.
215		unistd.unlink(temporary_filename)
216		sysstat.umask(old_umask)
217		secret_file = io.open(secret_filename, "r")
218	end
219	if secret_file == nil then
220		os.exit(177)
221	end
222	secret = secret_file:read()
223	secret_file:close()
224	if secret:len() ~= 64 then
225		os.exit(177)
226	end
227	return secret
228end
229
230-- Returns value of cookie if cookie is valid. Otherwise returns nil.
231function validate_value(expected_field, cookie)
232	local i = 0
233	local value = ""
234	local field = ""
235	local expiration = 0
236	local salt = ""
237	local hmac = ""
238
239	if cookie == nil or cookie:len() < 3 or cookie:sub(1, 1) == "|" then
240		return nil
241	end
242
243	for component in string.gmatch(cookie, "[^|]+") do
244		if i == 0 then
245			field = component
246		elseif i == 1 then
247			value = component
248		elseif i == 2 then
249			expiration = tonumber(component)
250			if expiration == nil then
251				expiration = -1
252			end
253		elseif i == 3 then
254			salt = component
255		elseif i == 4 then
256			hmac = component
257		else
258			break
259		end
260		i = i + 1
261	end
262
263	if hmac == nil or hmac:len() == 0 then
264		return nil
265	end
266
267	-- Lua hashes strings, so these comparisons are time invariant.
268	if hmac ~= crypto.hmac.digest("sha256", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, get_secret()) then
269		return nil
270	end
271
272	if expiration == -1 or (expiration ~= 0 and expiration <= os.time()) then
273		return nil
274	end
275
276	if url_decode(field) ~= expected_field then
277		return nil
278	end
279
280	return url_decode(value)
281end
282
283function secure_value(field, value, expiration)
284	if value == nil or value:len() <= 0 then
285		return ""
286	end
287
288	local authstr = ""
289	local salt = crypto.hex(crypto.rand.bytes(16))
290	value = url_encode(value)
291	field = url_encode(field)
292	authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt
293	authstr = authstr .. "|" .. crypto.hmac.digest("sha256", authstr, get_secret())
294	return authstr
295end
296
297function set_cookie(cookie, value)
298	html("Set-Cookie: " .. cookie .. "=" .. value .. "; HttpOnly")
299	if http["https"] == "yes" or http["https"] == "on" or http["https"] == "1" then
300		html("; secure")
301	end
302	html("\n")
303end
304
305function redirect_to(url)
306	html("Status: 302 Redirect\n")
307	html("Cache-Control: no-cache, no-store\n")
308	html("Location: " .. url .. "\n")
309end
310
311function not_found()
312	html("Status: 404 Not Found\n")
313	html("Cache-Control: no-cache, no-store\n\n")
314end