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-- 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
183
184--
185--
186-- Cookie construction and validation helpers.
187--
188--
189
190local secret = nil
191
192-- Loads a secret from a file, creates a secret, or returns one from memory.
193function get_secret()
194	if secret ~= nil then
195		return secret
196	end
197	local secret_file = io.open(secret_filename, "r")
198	if secret_file == nil then
199		local old_umask = sysstat.umask(63)
200		local temporary_filename = secret_filename .. ".tmp." .. crypto.hex(crypto.rand.bytes(16))
201		local temporary_file = io.open(temporary_filename, "w")
202		if temporary_file == nil then
203			os.exit(177)
204		end
205		temporary_file:write(crypto.hex(crypto.rand.bytes(32)))
206		temporary_file:close()
207		unistd.link(temporary_filename, secret_filename) -- Intentionally fails in the case that another process is doing the same.
208		unistd.unlink(temporary_filename)
209		sysstat.umask(old_umask)
210		secret_file = io.open(secret_filename, "r")
211	end
212	if secret_file == nil then
213		os.exit(177)
214	end
215	secret = secret_file:read()
216	secret_file:close()
217	if secret:len() ~= 64 then
218		os.exit(177)
219	end
220	return secret
221end
222
223-- Returns value of cookie if cookie is valid. Otherwise returns nil.
224function validate_value(expected_field, cookie)
225	local i = 0
226	local value = ""
227	local field = ""
228	local expiration = 0
229	local salt = ""
230	local hmac = ""
231
232	if cookie == nil or cookie:len() < 3 or cookie:sub(1, 1) == "|" then
233		return nil
234	end
235
236	for component in string.gmatch(cookie, "[^|]+") do
237		if i == 0 then
238			field = component
239		elseif i == 1 then
240			value = component
241		elseif i == 2 then
242			expiration = tonumber(component)
243			if expiration == nil then
244				expiration = -1
245			end
246		elseif i == 3 then
247			salt = component
248		elseif i == 4 then
249			hmac = component
250		else
251			break
252		end
253		i = i + 1
254	end
255
256	if hmac == nil or hmac:len() == 0 then
257		return nil
258	end
259
260	-- Lua hashes strings, so these comparisons are time invariant.
261	if hmac ~= crypto.hmac.digest("sha256", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, get_secret()) then
262		return nil
263	end
264
265	if expiration == -1 or (expiration ~= 0 and expiration <= os.time()) then
266		return nil
267	end
268
269	if url_decode(field) ~= expected_field then
270		return nil
271	end
272
273	return url_decode(value)
274end
275
276function secure_value(field, value, expiration)
277	if value == nil or value:len() <= 0 then
278		return ""
279	end
280
281	local authstr = ""
282	local salt = crypto.hex(crypto.rand.bytes(16))
283	value = url_encode(value)
284	field = url_encode(field)
285	authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt
286	authstr = authstr .. "|" .. crypto.hmac.digest("sha256", authstr, get_secret())
287	return authstr
288end
289
290function set_cookie(cookie, value)
291	html("Set-Cookie: " .. cookie .. "=" .. value .. "; HttpOnly")
292	if http["https"] == "yes" or http["https"] == "on" or http["https"] == "1" then
293		html("; secure")
294	end
295	html("\n")
296end
297
298function redirect_to(url)
299	html("Status: 302 Redirect\n")
300	html("Cache-Control: no-cache, no-store\n")
301	html("Location: " .. url .. "\n")
302end
303
304function not_found()
305	html("Status: 404 Not Found\n")
306	html("Cache-Control: no-cache, no-store\n\n")
307end