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-- 	lualdap >= 1.2
  7-- 	<https://git.zx2c4.com/lualdap/about/>
  8-- 	luaposix
  9-- 	<https://github.com/luaposix/luaposix>
 10--
 11local sysstat = require("posix.sys.stat")
 12local unistd = require("posix.unistd")
 13local crypto = require("crypto")
 14local lualdap = require("lualdap")
 15
 16
 17--
 18--
 19-- Configure these variables for your settings.
 20--
 21--
 22
 23-- A list of password protected repositories, with which gentooAccess
 24-- group is allowed to access each one.
 25local protected_repos = {
 26	glouglou = "infra",
 27	portage = "dev"
 28}
 29
 30-- Set this to a path this script can write to for storing a persistent
 31-- cookie secret, which should be guarded.
 32local secret_filename = "/var/cache/cgit/auth-secret"
 33
 34
 35--
 36--
 37-- Authentication functions follow below. Swap these out if you want different authentication semantics.
 38--
 39--
 40
 41-- Sets HTTP cookie headers based on post and sets up redirection.
 42function authenticate_post()
 43	local redirect = validate_value("redirect", post["redirect"])
 44
 45	if redirect == nil then
 46		not_found()
 47		return 0
 48	end
 49
 50	redirect_to(redirect)
 51	
 52	local groups = gentoo_ldap_user_groups(post["username"], post["password"])
 53	if groups == nil then
 54		set_cookie("cgitauth", "")
 55	else
 56		-- One week expiration time
 57		set_cookie("cgitauth", secure_value("gentoogroups", table.concat(groups, ","), os.time() + 604800))
 58	end
 59
 60	html("\n")
 61	return 0
 62end
 63
 64
 65-- Returns 1 if the cookie is valid and 0 if it is not.
 66function authenticate_cookie()
 67	local required_group = protected_repos[cgit["repo"]]
 68	if required_group == nil then
 69		-- We return as valid if the repo is not protected.
 70		return 1
 71	end
 72	
 73	local user_groups = validate_value("gentoogroups", get_cookie(http["cookie"], "cgitauth"))
 74	if user_groups == nil or user_groups == "" then
 75		return 0
 76	end
 77	for group in string.gmatch(user_groups, "[^,]+") do
 78		if group == required_group then
 79			return 1
 80		end
 81	end
 82	return 0
 83end
 84
 85-- Prints the html for the login form.
 86function body()
 87	html("<h2>Gentoo LDAP Authentication Required</h2>")
 88	html("<form method='post' action='")
 89	html_attr(cgit["login"])
 90	html("'>")
 91	html("<input type='hidden' name='redirect' value='")
 92	html_attr(secure_value("redirect", cgit["url"], 0))
 93	html("' />")
 94	html("<table>")
 95	html("<tr><td><label for='username'>Username:</label></td><td><input id='username' name='username' autofocus /></td></tr>")
 96	html("<tr><td><label for='password'>Password:</label></td><td><input id='password' name='password' type='password' /></td></tr>")
 97	html("<tr><td colspan='2'><input value='Login' type='submit' /></td></tr>")
 98	html("</table></form>")
 99
100	return 0
101end
102
103--
104--
105-- Gentoo LDAP support.
106--
107--
108
109function gentoo_ldap_user_groups(username, password)
110	-- Ensure the user is alphanumeric
111	if username == nil or username:match("%W") then
112		return nil
113	end
114
115	local who = "uid=" .. username .. ",ou=devs,dc=gentoo,dc=org"
116
117	local ldap, err = lualdap.open_simple {
118		uri = "ldap://ldap1.gentoo.org",
119		who = who,
120		password = password,
121		starttls = true,
122		certfile = "/var/www/uwsgi/cgit/gentoo-ldap/star.gentoo.org.crt",
123		keyfile = "/var/www/uwsgi/cgit/gentoo-ldap/star.gentoo.org.key",
124		cacertfile = "/var/www/uwsgi/cgit/gentoo-ldap/ca.pem"
125	}
126	if ldap == nil then
127		return nil
128	end
129
130	local group_suffix = ".group"
131	local group_suffix_len = group_suffix:len()
132	local groups = {}
133	for dn, attribs in ldap:search { base = who, scope = "subtree" } do
134		local access = attribs["gentooAccess"]
135		if dn == who and access ~= nil then
136			for i, v in ipairs(access) do
137				local vlen = v:len()
138				if vlen > group_suffix_len and v:sub(-group_suffix_len) == group_suffix then
139					table.insert(groups, v:sub(1, vlen - group_suffix_len))
140				end
141			end
142		end
143	end
144
145	ldap:close()
146
147	return groups
148end
149
150--
151--
152-- Wrapper around filter API, exposing the http table, the cgit table, and the post table to the above functions.
153--
154--
155
156local actions = {}
157actions["authenticate-post"] = authenticate_post
158actions["authenticate-cookie"] = authenticate_cookie
159actions["body"] = body
160
161function filter_open(...)
162	action = actions[select(1, ...)]
163
164	http = {}
165	http["cookie"] = select(2, ...)
166	http["method"] = select(3, ...)
167	http["query"] = select(4, ...)
168	http["referer"] = select(5, ...)
169	http["path"] = select(6, ...)
170	http["host"] = select(7, ...)
171	http["https"] = select(8, ...)
172
173	cgit = {}
174	cgit["repo"] = select(9, ...)
175	cgit["page"] = select(10, ...)
176	cgit["url"] = select(11, ...)
177	cgit["login"] = select(12, ...)
178
179end
180
181function filter_close()
182	return action()
183end
184
185function filter_write(str)
186	post = parse_qs(str)
187end
188
189
190--
191--
192-- Utility functions based on keplerproject/wsapi.
193--
194--
195
196function url_decode(str)
197	if not str then
198		return ""
199	end
200	str = string.gsub(str, "+", " ")
201	str = string.gsub(str, "%%(%x%x)", function(h) return string.char(tonumber(h, 16)) end)
202	str = string.gsub(str, "\r\n", "\n")
203	return str
204end
205
206function url_encode(str)
207	if not str then
208		return ""
209	end
210	str = string.gsub(str, "\n", "\r\n")
211	str = string.gsub(str, "([^%w ])", function(c) return string.format("%%%02X", string.byte(c)) end)
212	str = string.gsub(str, " ", "+")
213	return str
214end
215
216function parse_qs(qs)
217	local tab = {}
218	for key, val in string.gmatch(qs, "([^&=]+)=([^&=]*)&?") do
219		tab[url_decode(key)] = url_decode(val)
220	end
221	return tab
222end
223
224function get_cookie(cookies, name)
225	cookies = string.gsub(";" .. cookies .. ";", "%s*;%s*", ";")
226	return string.match(cookies, ";" .. name .. "=(.-);")
227end
228
229
230--
231--
232-- Cookie construction and validation helpers.
233--
234--
235
236local secret = nil
237
238-- Loads a secret from a file, creates a secret, or returns one from memory.
239function get_secret()
240	if secret ~= nil then
241		return secret
242	end
243	local secret_file = io.open(secret_filename, "r")
244	if secret_file == nil then
245		local old_umask = sysstat.umask(63)
246		local temporary_filename = secret_filename .. ".tmp." .. crypto.hex(crypto.rand.bytes(16))
247		local temporary_file = io.open(temporary_filename, "w")
248		if temporary_file == nil then
249			os.exit(177)
250		end
251		temporary_file:write(crypto.hex(crypto.rand.bytes(32)))
252		temporary_file:close()
253		unistd.link(temporary_filename, secret_filename) -- Intentionally fails in the case that another process is doing the same.
254		unistd.unlink(temporary_filename)
255		sysstat.umask(old_umask)
256		secret_file = io.open(secret_filename, "r")
257	end
258	if secret_file == nil then
259		os.exit(177)
260	end
261	secret = secret_file:read()
262	secret_file:close()
263	if secret:len() ~= 64 then
264		os.exit(177)
265	end
266	return secret
267end
268
269-- Returns value of cookie if cookie is valid. Otherwise returns nil.
270function validate_value(expected_field, cookie)
271	local i = 0
272	local value = ""
273	local field = ""
274	local expiration = 0
275	local salt = ""
276	local hmac = ""
277
278	if cookie == nil or cookie:len() < 3 or cookie:sub(1, 1) == "|" then
279		return nil
280	end
281
282	for component in string.gmatch(cookie, "[^|]+") do
283		if i == 0 then
284			field = component
285		elseif i == 1 then
286			value = component
287		elseif i == 2 then
288			expiration = tonumber(component)
289			if expiration == nil then
290				expiration = -1
291			end
292		elseif i == 3 then
293			salt = component
294		elseif i == 4 then
295			hmac = component
296		else
297			break
298		end
299		i = i + 1
300	end
301
302	if hmac == nil or hmac:len() == 0 then
303		return nil
304	end
305
306	-- Lua hashes strings, so these comparisons are time invariant.
307	if hmac ~= crypto.hmac.digest("sha256", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, get_secret()) then
308		return nil
309	end
310
311	if expiration == -1 or (expiration ~= 0 and expiration <= os.time()) then
312		return nil
313	end
314
315	if url_decode(field) ~= expected_field then
316		return nil
317	end
318
319	return url_decode(value)
320end
321
322function secure_value(field, value, expiration)
323	if value == nil or value:len() <= 0 then
324		return ""
325	end
326
327	local authstr = ""
328	local salt = crypto.hex(crypto.rand.bytes(16))
329	value = url_encode(value)
330	field = url_encode(field)
331	authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt
332	authstr = authstr .. "|" .. crypto.hmac.digest("sha256", authstr, get_secret())
333	return authstr
334end
335
336function set_cookie(cookie, value)
337	html("Set-Cookie: " .. cookie .. "=" .. value .. "; HttpOnly")
338	if http["https"] == "yes" or http["https"] == "on" or http["https"] == "1" then
339		html("; secure")
340	end
341	html("\n")
342end
343
344function redirect_to(url)
345	html("Status: 302 Redirect\n")
346	html("Cache-Control: no-cache, no-store\n")
347	html("Location: " .. url .. "\n")
348end
349
350function not_found()
351	html("Status: 404 Not Found\n")
352	html("Cache-Control: no-cache, no-store\n\n")
353end