about summary refs log tree commit diff
path: root/www/git.causal.agency/cgit/filters/gentoo-ldap-authentication.lua
blob: 673c88d1021cd19074a748fc2763bc5a3bd79480 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
-- This script may be used with the auth-filter. Be sure to configure it as you wish.
--
-- Requirements:
-- 	luaossl
-- 	<http://25thandclement.com/~william/projects/luaossl.html>
-- 	lualdap >= 1.2
-- 	<https://git.zx2c4.com/lualdap/about/>
-- 	luaposix
-- 	<https://github.com/luaposix/luaposix>
--
local sysstat = require("posix.sys.stat")
local unistd = require("posix.unistd")
local lualdap = require("lualdap")
local rand = require("openssl.rand")
local hmac = require("openssl.hmac")

--
--
-- Configure these variables for your settings.
--
--

-- A list of password protected repositories, with which gentooAccess
-- group is allowed to access each one.
local protected_repos = {
	glouglou = "infra",
	portage = "dev"
}

-- Set this to a path this script can write to for storing a persistent
-- cookie secret, which should be guarded.
local secret_filename = "/var/cache/cgit/auth-secret"


--
--
-- Authentication functions follow below. Swap these out if you want different authentication semantics.
--
--

-- Sets HTTP cookie headers based on post and sets up redirection.
function authenticate_post()
	local redirect = validate_value("redirect", post["redirect"])

	if redirect == nil then
		not_found()
		return 0
	end

	redirect_to(redirect)
	
	local groups = gentoo_ldap_user_groups(post["username"], post["password"])
	if groups == nil then
		set_cookie("cgitauth", "")
	else
		-- One week expiration time
		set_cookie("cgitauth", secure_value("gentoogroups", table.concat(groups, ","), os.time() + 604800))
	end

	html("\n")
	return 0
end


-- Returns 1 if the cookie is valid and 0 if it is not.
function authenticate_cookie()
	local required_group = protected_repos[cgit["repo"]]
	if required_group == nil then
		-- We return as valid if the repo is not protected.
		return 1
	end
	
	local user_groups = validate_value("gentoogroups", get_cookie(http["cookie"], "cgitauth"))
	if user_groups == nil or user_groups == "" then
		return 0
	end
	for group in string.gmatch(user_groups, "[^,]+") do
		if group == required_group then
			return 1
		end
	end
	return 0
end

-- Prints the html for the login form.
function body()
	html("<h2>Gentoo LDAP Authentication Required</h2>")
	html("<form method='post' action='")
	html_attr(cgit["login"])
	html("'>")
	html("<input type='hidden' name='redirect' value='")
	html_attr(secure_value("redirect", cgit["url"], 0))
	html("' />")
	html("<table>")
	html("<tr><td><label for='username'>Username:</label></td><td><input id='username' name='username' autofocus /></td></tr>")
	html("<tr><td><label for='password'>Password:</label></td><td><input id='password' name='password' type='password' /></td></tr>")
	html("<tr><td colspan='2'><input value='Login' type='submit' /></td></tr>")
	html("</table></form>")

	return 0
end

--
--
-- Gentoo LDAP support.
--
--

function gentoo_ldap_user_groups(username, password)
	-- Ensure the user is alphanumeric
	if username == nil or username:match("%W") then
		return nil
	end

	local who = "uid=" .. username .. ",ou=devs,dc=gentoo,dc=org"

	local ldap, err = lualdap.open_simple {
		uri = "ldap://ldap1.gentoo.org",
		who = who,
		password = password,
		starttls = true,
		certfile = "/var/www/uwsgi/cgit/gentoo-ldap/star.gentoo.org.crt",
		keyfile = "/var/www/uwsgi/cgit/gentoo-ldap/star.gentoo.org.key",
		cacertfile = "/var/www/uwsgi/cgit/gentoo-ldap/ca.pem"
	}
	if ldap == nil then
		return nil
	end

	local group_suffix = ".group"
	local group_suffix_len = group_suffix:len()
	local groups = {}
	for dn, attribs in ldap:search { base = who, scope = "subtree" } do
		local access = attribs["gentooAccess"]
		if dn == who and access ~= nil then
			for i, v in ipairs(access) do
				local vlen = v:len()
				if vlen > group_suffix_len and v:sub(-group_suffix_len) == group_suffix then
					table.insert(groups, v:sub(1, vlen - group_suffix_len))
				end
			end
		end
	end

	ldap:close()

	return groups
end

--
--
-- Wrapper around filter API, exposing the http table, the cgit table, and the post table to the above functions.
--
--

local actions = {}
actions["authenticate-post"] = authenticate_post
actions["authenticate-cookie"] = authenticate_cookie
actions["body"] = body

function filter_open(...)
	action = actions[select(1, ...)]

	http = {}
	http["cookie"] = select(2, ...)
	http["method"] = select(3, ...)
	http["query"] = select(4, ...)
	http["referer"] = select(5, ...)
	http["path"] = select(6, ...)
	http["host"] = select(7, ...)
	http["https"] = select(8, ...)

	cgit = {}
	cgit["repo"] = select(9, ...)
	cgit["page"] = select(10, ...)
	cgit["url"] = select(11, ...)
	cgit["login"] = select(12, ...)

end

function filter_close()
	return action()
end

function filter_write(str)
	post = parse_qs(str)
end


--
--
-- Utility functions based on keplerproject/wsapi.
--
--

function url_decode(str)
	if not str then
		return ""
	end
	str = string.gsub(str, "+", " ")
	str = string.gsub(str, "%%(%x%x)", function(h) return string.char(tonumber(h, 16)) end)
	str = string.gsub(str, "\r\n", "\n")
	return str
end

function url_encode(str)
	if not str then
		return ""
	end
	str = string.gsub(str, "\n", "\r\n")
	str = string.gsub(str, "([^%w ])", function(c) return string.format("%%%02X", string.byte(c)) end)
	str = string.gsub(str, " ", "+")
	return str
end

function parse_qs(qs)
	local tab = {}
	for key, val in string.gmatch(qs, "([^&=]+)=([^&=]*)&?") do
		tab[url_decode(key)] = url_decode(val)
	end
	return tab
end

function get_cookie(cookies, name)
	cookies = string.gsub(";" .. cookies .. ";", "%s*;%s*", ";")
	return string.match(cookies, ";" .. name .. "=(.-);")
end

function tohex(b)
	local x = ""
	for i = 1, #b do
		x = x .. string.format("%.2x", string.byte(b, i))
	end
	return x
end

--
--
-- Cookie construction and validation helpers.
--
--

local secret = nil

-- Loads a secret from a file, creates a secret, or returns one from memory.
function get_secret()
	if secret ~= nil then
		return secret
	end
	local secret_file = io.open(secret_filename, "r")
	if secret_file == nil then
		local old_umask = sysstat.umask(63)
		local temporary_filename = secret_filename .. ".tmp." .. tohex(rand.bytes(16))
		local temporary_file = io.open(temporary_filename, "w")
		if temporary_file == nil then
			os.exit(177)
		end
		temporary_file:write(tohex(rand.bytes(32)))
		temporary_file:close()
		unistd.link(temporary_filename, secret_filename) -- Intentionally fails in the case that another process is doing the same.
		unistd.unlink(temporary_filename)
		sysstat.umask(old_umask)
		secret_file = io.open(secret_filename, "r")
	end
	if secret_file == nil then
		os.exit(177)
	end
	secret = secret_file:read()
	secret_file:close()
	if secret:len() ~= 64 then
		os.exit(177)
	end
	return secret
end

-- Returns value of cookie if cookie is valid. Otherwise returns nil.
function validate_value(expected_field, cookie)
	local i = 0
	local value = ""
	local field = ""
	local expiration = 0
	local salt = ""
	local chmac = ""

	if cookie == nil or cookie:len() < 3 or cookie:sub(1, 1) == "|" then
		return nil
	end

	for component in string.gmatch(cookie, "[^|]+") do
		if i == 0 then
			field = component
		elseif i == 1 then
			value = component
		elseif i == 2 then
			expiration = tonumber(component)
			if expiration == nil then
				expiration = -1
			end
		elseif i == 3 then
			salt = component
		elseif i == 4 then
			chmac = component
		else
			break
		end
		i = i + 1
	end

	if chmac == nil or chmac:len() == 0 then
		return nil
	end

	-- Lua hashes strings, so these comparisons are time invariant.
	if chmac ~= tohex(hmac.new(get_secret(), "sha256"):final(field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt)) then
		return nil
	end

	if expiration == -1 or (expiration ~= 0 and expiration <= os.time()) then
		return nil
	end

	if url_decode(field) ~= expected_field then
		return nil
	end

	return url_decode(value)
end

function secure_value(field, value, expiration)
	if value == nil or value:len() <= 0 then
		return ""
	end

	local authstr = ""
	local salt = tohex(rand.bytes(16))
	value = url_encode(value)
	field = url_encode(field)
	authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt
	authstr = authstr .. "|" .. tohex(hmac.new(get_secret(), "sha256"):final(authstr))
	return authstr
end

function set_cookie(cookie, value)
	html("Set-Cookie: " .. cookie .. "=" .. value .. "; HttpOnly")
	if http["https"] == "yes" or http["https"] == "on" or http["https"] == "1" then
		html("; secure")
	end
	html("\n")
end

function redirect_to(url)
	html("Status: 302 Redirect\n")
	html("Cache-Control: no-cache, no-store\n")
	html("Location: " .. url .. "\n")
end

function not_found()
	html("Status: 404 Not Found\n")
	html("Cache-Control: no-cache, no-store\n\n")
end