1-- This script may be used with the auth-filter. Be sure to configure it as you wish.
  2--
  3-- Requirements:
  4-- 	luaossl
  5-- 	<http://25thandclement.com/~william/projects/luaossl.html>
  6-- 	luaposix
  7-- 	<https://github.com/luaposix/luaposix>
  8--
  9local sysstat = require("posix.sys.stat")
 10local unistd = require("posix.unistd")
 11local rand = require("openssl.rand")
 12local hmac = require("openssl.hmac")
 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-- A list of users and hashes, generated with `mkpasswd -m sha-512 -R 300000`.
 27local users = {
 28	jason		= "$6$rounds=300000$YYJct3n/o.ruYK$HhpSeuCuW1fJkpvMZOZzVizeLsBKcGA/aF2UPuV5v60JyH2MVSG6P511UMTj2F3H75.IT2HIlnvXzNb60FcZH1",
 29	laurent		= "$6$rounds=300000$dP0KNHwYb3JKigT$pN/LG7rWxQ4HniFtx5wKyJXBJUKP7R01zTNZ0qSK/aivw8ywGAOdfYiIQFqFhZFtVGvr11/7an.nesvm8iJUi.",
 30	bob		= "$6$rounds=300000$jCLCCt6LUpTz$PI1vvd1yaVYcCzqH8QAJFcJ60b6W/6sjcOsU7mAkNo7IE8FRGW1vkjF8I/T5jt/auv5ODLb1L4S2s.CAyZyUC"
 31}
 32
 33-- Set this to a path this script can write to for storing a persistent
 34-- cookie secret, which should be guarded.
 35local secret_filename = "/var/cache/cgit/auth-secret"
 36
 37--
 38--
 39-- Authentication functions follow below. Swap these out if you want different authentication semantics.
 40--
 41--
 42
 43-- Sets HTTP cookie headers based on post and sets up redirection.
 44function authenticate_post()
 45	local hash = users[post["username"]]
 46	local redirect = validate_value("redirect", post["redirect"])
 47
 48	if redirect == nil then
 49		not_found()
 50		return 0
 51	end
 52
 53	redirect_to(redirect)
 54
 55	if hash == nil or hash ~= unistd.crypt(post["password"], hash) then
 56		set_cookie("cgitauth", "")
 57	else
 58		-- One week expiration time
 59		local username = secure_value("username", post["username"], os.time() + 604800)
 60		set_cookie("cgitauth", username)
 61	end
 62
 63	html("\n")
 64	return 0
 65end
 66
 67
 68-- Returns 1 if the cookie is valid and 0 if it is not.
 69function authenticate_cookie()
 70	accepted_users = protected_repos[cgit["repo"]]
 71	if accepted_users == nil then
 72		-- We return as valid if the repo is not protected.
 73		return 1
 74	end
 75
 76	local username = validate_value("username", get_cookie(http["cookie"], "cgitauth"))
 77	if username == nil or not accepted_users[username:lower()] then
 78		return 0
 79	else
 80		return 1
 81	end
 82end
 83
 84-- Prints the html for the login form.
 85function body()
 86	html("<h2>Authentication Required</h2>")
 87	html("<form method='post' action='")
 88	html_attr(cgit["login"])
 89	html("'>")
 90	html("<input type='hidden' name='redirect' value='")
 91	html_attr(secure_value("redirect", cgit["url"], 0))
 92	html("' />")
 93	html("<table>")
 94	html("<tr><td><label for='username'>Username:</label></td><td><input id='username' name='username' autofocus /></td></tr>")
 95	html("<tr><td><label for='password'>Password:</label></td><td><input id='password' name='password' type='password' /></td></tr>")
 96	html("<tr><td colspan='2'><input value='Login' type='submit' /></td></tr>")
 97	html("</table></form>")
 98
 99	return 0
100end
101
102
103
104--
105--
106-- Wrapper around filter API, exposing the http table, the cgit table, and the post table to the above functions.
107--
108--
109
110local actions = {}
111actions["authenticate-post"] = authenticate_post
112actions["authenticate-cookie"] = authenticate_cookie
113actions["body"] = body
114
115function filter_open(...)
116	action = actions[select(1, ...)]
117
118	http = {}
119	http["cookie"] = select(2, ...)
120	http["method"] = select(3, ...)
121	http["query"] = select(4, ...)
122	http["referer"] = select(5, ...)
123	http["path"] = select(6, ...)
124	http["host"] = select(7, ...)
125	http["https"] = select(8, ...)
126
127	cgit = {}
128	cgit["repo"] = select(9, ...)
129	cgit["page"] = select(10, ...)
130	cgit["url"] = select(11, ...)
131	cgit["login"] = select(12, ...)
132
133end
134
135function filter_close()
136	return action()
137end
138
139function filter_write(str)
140	post = parse_qs(str)
141end
142
143
144--
145--
146-- Utility functions based on keplerproject/wsapi.
147--
148--
149
150function url_decode(str)
151	if not str then
152		return ""
153	end
154	str = string.gsub(str, "+", " ")
155	str = string.gsub(str, "%%(%x%x)", function(h) return string.char(tonumber(h, 16)) end)
156	str = string.gsub(str, "\r\n", "\n")
157	return str
158end
159
160function url_encode(str)
161	if not str then
162		return ""
163	end
164	str = string.gsub(str, "\n", "\r\n")
165	str = string.gsub(str, "([^%w ])", function(c) return string.format("%%%02X", string.byte(c)) end)
166	str = string.gsub(str, " ", "+")
167	return str
168end
169
170function parse_qs(qs)
171	local tab = {}
172	for key, val in string.gmatch(qs, "([^&=]+)=([^&=]*)&?") do
173		tab[url_decode(key)] = url_decode(val)
174	end
175	return tab
176end
177
178function get_cookie(cookies, name)
179	cookies = string.gsub(";" .. cookies .. ";", "%s*;%s*", ";")
180	return url_decode(string.match(cookies, ";" .. name .. "=(.-);"))
181end
182
183function tohex(b)
184	local x = ""
185	for i = 1, #b do
186		x = x .. string.format("%.2x", string.byte(b, i))
187	end
188	return x
189end
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." .. tohex(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(tohex(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 chmac = ""
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			chmac = component
257		else
258			break
259		end
260		i = i + 1
261	end
262
263	if chmac == nil or chmac:len() == 0 then
264		return nil
265	end
266
267	-- Lua hashes strings, so these comparisons are time invariant.
268	if chmac ~= tohex(hmac.new(get_secret(), "sha256"):final(field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt)) 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 = tohex(rand.bytes(16))
290	value = url_encode(value)
291	field = url_encode(field)
292	authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt
293	authstr = authstr .. "|" .. tohex(hmac.new(get_secret(), "sha256"):final(authstr))
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