1-- This script may be used with the auth-filter.
  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-- This file should contain a series of lines in the form of:
 15--	username1:hash1
 16--	username2:hash2
 17--	username3:hash3
 18--	...
 19-- Hashes can be generated using something like `mkpasswd -m sha-512 -R 300000`.
 20-- This file should not be world-readable.
 21local users_filename = "/etc/cgit-auth/users"
 22
 23-- This file should contain a series of lines in the form of:
 24-- 	groupname1:username1,username2,username3,...
 25--	...
 26local groups_filename = "/etc/cgit-auth/groups"
 27
 28-- This file should contain a series of lines in the form of:
 29-- 	reponame1:groupname1,groupname2,groupname3,...
 30--	...
 31local repos_filename = "/etc/cgit-auth/repos"
 32
 33-- Set this to a path this script can write to for storing a persistent
 34-- cookie secret, which should not be world-readable.
 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-- Looks up a hash for a given user.
 44function lookup_hash(user)
 45	local line
 46	for line in io.lines(users_filename) do
 47		local u, h = string.match(line, "(.-):(.+)")
 48		if u:lower() == user:lower() then
 49			return h
 50		end
 51	end
 52	return nil
 53end
 54
 55-- Looks up users for a given repo.
 56function lookup_users(repo)
 57	local users = nil
 58	local groups = nil
 59	local line, group, user
 60	for line in io.lines(repos_filename) do
 61		local r, g = string.match(line, "(.-):(.+)")
 62		if r == repo then
 63			groups = { }
 64			for group in string.gmatch(g, "([^,]+)") do
 65				groups[group:lower()] = true
 66			end
 67			break
 68		end
 69	end
 70	if groups == nil then
 71		return nil
 72	end
 73	for line in io.lines(groups_filename) do
 74		local g, u = string.match(line, "(.-):(.+)")
 75		if groups[g:lower()] then
 76			if users == nil then
 77				users = { }
 78			end
 79			for user in string.gmatch(u, "([^,]+)") do
 80				users[user:lower()] = true
 81			end
 82		end
 83	end
 84	return users
 85end
 86
 87
 88-- Sets HTTP cookie headers based on post and sets up redirection.
 89function authenticate_post()
 90	local hash = lookup_hash(post["username"])
 91	local redirect = validate_value("redirect", post["redirect"])
 92
 93	if redirect == nil then
 94		not_found()
 95		return 0
 96	end
 97
 98	redirect_to(redirect)
 99
100	if hash == nil or hash ~= unistd.crypt(post["password"], hash) then
101		set_cookie("cgitauth", "")
102	else
103		-- One week expiration time
104		local username = secure_value("username", post["username"], os.time() + 604800)
105		set_cookie("cgitauth", username)
106	end
107
108	html("\n")
109	return 0
110end
111
112
113-- Returns 1 if the cookie is valid and 0 if it is not.
114function authenticate_cookie()
115	accepted_users = lookup_users(cgit["repo"])
116	if accepted_users == nil then
117		-- We return as valid if the repo is not protected.
118		return 1
119	end
120
121	local username = validate_value("username", get_cookie(http["cookie"], "cgitauth"))
122	if username == nil or not accepted_users[username:lower()] then
123		return 0
124	else
125		return 1
126	end
127end
128
129-- Prints the html for the login form.
130function body()
131	html("<h2>Authentication Required</h2>")
132	html("<form method='post' action='")
133	html_attr(cgit["login"])
134	html("'>")
135	html("<input type='hidden' name='redirect' value='")
136	html_attr(secure_value("redirect", cgit["url"], 0))
137	html("' />")
138	html("<table>")
139	html("<tr><td><label for='username'>Username:</label></td><td><input id='username' name='username' autofocus /></td></tr>")
140	html("<tr><td><label for='password'>Password:</label></td><td><input id='password' name='password' type='password' /></td></tr>")
141	html("<tr><td colspan='2'><input value='Login' type='submit' /></td></tr>")
142	html("</table></form>")
143
144	return 0
145end
146
147
148
149--
150--
151-- Wrapper around filter API, exposing the http table, the cgit table, and the post table to the above functions.
152--
153--
154
155local actions = {}
156actions["authenticate-post"] = authenticate_post
157actions["authenticate-cookie"] = authenticate_cookie
158actions["body"] = body
159
160function filter_open(...)
161	action = actions[select(1, ...)]
162
163	http = {}
164	http["cookie"] = select(2, ...)
165	http["method"] = select(3, ...)
166	http["query"] = select(4, ...)
167	http["referer"] = select(5, ...)
168	http["path"] = select(6, ...)
169	http["host"] = select(7, ...)
170	http["https"] = select(8, ...)
171
172	cgit = {}
173	cgit["repo"] = select(9, ...)
174	cgit["page"] = select(10, ...)
175	cgit["url"] = select(11, ...)
176	cgit["login"] = select(12, ...)
177
178end
179
180function filter_close()
181	return action()
182end
183
184function filter_write(str)
185	post = parse_qs(str)
186end
187
188
189--
190--
191-- Utility functions based on keplerproject/wsapi.
192--
193--
194
195function url_decode(str)
196	if not str then
197		return ""
198	end
199	str = string.gsub(str, "+", " ")
200	str = string.gsub(str, "%%(%x%x)", function(h) return string.char(tonumber(h, 16)) end)
201	str = string.gsub(str, "\r\n", "\n")
202	return str
203end
204
205function url_encode(str)
206	if not str then
207		return ""
208	end
209	str = string.gsub(str, "\n", "\r\n")
210	str = string.gsub(str, "([^%w ])", function(c) return string.format("%%%02X", string.byte(c)) end)
211	str = string.gsub(str, " ", "+")
212	return str
213end
214
215function parse_qs(qs)
216	local tab = {}
217	for key, val in string.gmatch(qs, "([^&=]+)=([^&=]*)&?") do
218		tab[url_decode(key)] = url_decode(val)
219	end
220	return tab
221end
222
223function get_cookie(cookies, name)
224	cookies = string.gsub(";" .. cookies .. ";", "%s*;%s*", ";")
225	return url_decode(string.match(cookies, ";" .. name .. "=(.-);"))
226end
227
228function tohex(b)
229	local x = ""
230	for i = 1, #b do
231		x = x .. string.format("%.2x", string.byte(b, i))
232	end
233	return x
234end
235
236--
237--
238-- Cookie construction and validation helpers.
239--
240--
241
242local secret = nil
243
244-- Loads a secret from a file, creates a secret, or returns one from memory.
245function get_secret()
246	if secret ~= nil then
247		return secret
248	end
249	local secret_file = io.open(secret_filename, "r")
250	if secret_file == nil then
251		local old_umask = sysstat.umask(63)
252		local temporary_filename = secret_filename .. ".tmp." .. tohex(rand.bytes(16))
253		local temporary_file = io.open(temporary_filename, "w")
254		if temporary_file == nil then
255			os.exit(177)
256		end
257		temporary_file:write(tohex(rand.bytes(32)))
258		temporary_file:close()
259		unistd.link(temporary_filename, secret_filename) -- Intentionally fails in the case that another process is doing the same.
260		unistd.unlink(temporary_filename)
261		sysstat.umask(old_umask)
262		secret_file = io.open(secret_filename, "r")
263	end
264	if secret_file == nil then
265		os.exit(177)
266	end
267	secret = secret_file:read()
268	secret_file:close()
269	if secret:len() ~= 64 then
270		os.exit(177)
271	end
272	return secret
273end
274
275-- Returns value of cookie if cookie is valid. Otherwise returns nil.
276function validate_value(expected_field, cookie)
277	local i = 0
278	local value = ""
279	local field = ""
280	local expiration = 0
281	local salt = ""
282	local chmac = ""
283
284	if cookie == nil or cookie:len() < 3 or cookie:sub(1, 1) == "|" then
285		return nil
286	end
287
288	for component in string.gmatch(cookie, "[^|]+") do
289		if i == 0 then
290			field = component
291		elseif i == 1 then
292			value = component
293		elseif i == 2 then
294			expiration = tonumber(component)
295			if expiration == nil then
296				expiration = -1
297			end
298		elseif i == 3 then
299			salt = component
300		elseif i == 4 then
301			chmac = component
302		else
303			break
304		end
305		i = i + 1
306	end
307
308	if chmac == nil or chmac:len() == 0 then
309		return nil
310	end
311
312	-- Lua hashes strings, so these comparisons are time invariant.
313	if chmac ~= tohex(hmac.new(get_secret(), "sha256"):final(field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt)) then
314		return nil
315	end
316
317	if expiration == -1 or (expiration ~= 0 and expiration <= os.time()) then
318		return nil
319	end
320
321	if url_decode(field) ~= expected_field then
322		return nil
323	end
324
325	return url_decode(value)
326end
327
328function secure_value(field, value, expiration)
329	if value == nil or value:len() <= 0 then
330		return ""
331	end
332
333	local authstr = ""
334	local salt = tohex(rand.bytes(16))
335	value = url_encode(value)
336	field = url_encode(field)
337	authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt
338	authstr = authstr .. "|" .. tohex(hmac.new(get_secret(), "sha256"):final(authstr))
339	return authstr
340end
341
342function set_cookie(cookie, value)
343	html("Set-Cookie: " .. cookie .. "=" .. value .. "; HttpOnly")
344	if http["https"] == "yes" or http["https"] == "on" or http["https"] == "1" then
345		html("; secure")
346	end
347	html("\n")
348end
349
350function redirect_to(url)
351	html("Status: 302 Redirect\n")
352	html("Cache-Control: no-cache, no-store\n")
353	html("Location: " .. url .. "\n")
354end
355
356function not_found()
357	html("Status: 404 Not Found\n")
358	html("Cache-Control: no-cache, no-store\n\n")
359end