aboutsummaryrefslogtreecommitdiffstats
path: root/util/x509.lua
blob: ae250a559fe890d5b35f0f649695944e5a282037 (plain)
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
-- Prosody IM
-- Copyright (C) 2010 Matthew Wild
-- Copyright (C) 2010 Paul Aurich
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--

-- TODO: I feel a fair amount of this logic should be integrated into Luasec,
-- so that everyone isn't re-inventing the wheel.  Dependencies on
-- IDN libraries complicate that.


-- [TLS-CERTS] - https://www.rfc-editor.org/rfc/rfc6125.html
-- [XMPP-CORE] - https://www.rfc-editor.org/rfc/rfc6120.html
-- [SRV-ID]    - https://www.rfc-editor.org/rfc/rfc4985.html
-- [IDNA]      - https://www.rfc-editor.org/rfc/rfc5890.html
-- [LDAP]      - https://www.rfc-editor.org/rfc/rfc4519.html
-- [PKIX]      - https://www.rfc-editor.org/rfc/rfc5280.html

local nameprep = require "util.encodings".stringprep.nameprep;
local idna_to_ascii = require "util.encodings".idna.to_ascii;
local idna_to_unicode = require "util.encodings".idna.to_unicode;
local base64 = require "util.encodings".base64;
local log = require "util.logger".init("x509");
local mt = require "util.multitable";
local s_format = string.format;
local ipairs = ipairs;

local _ENV = nil;
-- luacheck: std none

local oid_commonname = "2.5.4.3"; -- [LDAP] 2.3
local oid_subjectaltname = "2.5.29.17"; -- [PKIX] 4.2.1.6
local oid_xmppaddr = "1.3.6.1.5.5.7.8.5"; -- [XMPP-CORE]
local oid_dnssrv   = "1.3.6.1.5.5.7.8.7"; -- [SRV-ID]

-- Compare a hostname (possibly international) with asserted names
-- extracted from a certificate.
-- This function follows the rules laid out in
-- sections 6.4.1 and 6.4.2 of [TLS-CERTS]
--
-- A wildcard ("*") all by itself is allowed only as the left-most label
local function compare_dnsname(host, asserted_names)
	-- TODO: Sufficient normalization?  Review relevant specs.
	local norm_host = idna_to_ascii(host)
	if norm_host == nil then
		log("info", "Host %s failed IDNA ToASCII operation", host)
		return false
	end

	norm_host = norm_host:lower()

	local host_chopped = norm_host:gsub("^[^.]+%.", "") -- everything after the first label

	for i=1,#asserted_names do
		local name = asserted_names[i]
		if norm_host == name:lower() then
			log("debug", "Cert dNSName %s matched hostname", name);
			return true
		end

		-- Allow the left most label to be a "*"
		if name:match("^%*%.") then
			local rest_name = name:gsub("^[^.]+%.", "")
			if host_chopped == rest_name:lower() then
				log("debug", "Cert dNSName %s matched hostname", name);
				return true
			end
		end
	end

	return false
end

-- Compare an XMPP domain name with the asserted id-on-xmppAddr
-- identities extracted from a certificate.  Both are UTF8 strings.
--
-- Per [XMPP-CORE], matches against asserted identities don't include
-- wildcards, so we just do a normalize on both and then a string comparison
--
-- TODO: Support for full JIDs?
local function compare_xmppaddr(host, asserted_names)
	local norm_host = nameprep(host)

	for i=1,#asserted_names do
		local name = asserted_names[i]

		-- We only want to match against bare domains right now, not
		-- those crazy full-er JIDs.
		if name:match("[@/]") then
			log("debug", "Ignoring xmppAddr %s because it's not a bare domain", name)
		else
			local norm_name = nameprep(name)
			if norm_name == nil then
				log("info", "Ignoring xmppAddr %s, failed nameprep!", name)
			else
				if norm_host == norm_name then
					log("debug", "Cert xmppAddr %s matched hostname", name)
					return true
				end
			end
		end
	end

	return false
end

-- Compare a host + service against the asserted id-on-dnsSRV (SRV-ID)
-- identities extracted from a certificate.
--
-- Per [SRV-ID], the asserted identities will be encoded in ASCII via ToASCII.
-- Comparison is done case-insensitively, and a wildcard ("*") all by itself
-- is allowed only as the left-most non-service label.
local function compare_srvname(host, service, asserted_names)
	local norm_host = idna_to_ascii(host)
	if norm_host == nil then
		log("info", "Host %s failed IDNA ToASCII operation", host);
		return false
	end

	-- Service names start with a "_"
	if service:match("^_") == nil then service = "_"..service end

	norm_host = norm_host:lower();
	local host_chopped = norm_host:gsub("^[^.]+%.", "") -- everything after the first label

	for i=1,#asserted_names do
		local asserted_service, name = asserted_names[i]:match("^(_[^.]+)%.(.*)");
		if service == asserted_service then
			if norm_host == name:lower() then
				log("debug", "Cert SRVName %s matched hostname", name);
				return true;
			end

			-- Allow the left most label to be a "*"
			if name:match("^%*%.") then
				local rest_name = name:gsub("^[^.]+%.", "")
				if host_chopped == rest_name:lower() then
					log("debug", "Cert SRVName %s matched hostname", name)
					return true
				end
			end
			if norm_host == name:lower() then
				log("debug", "Cert SRVName %s matched hostname", name);
				return true
			end
		end
	end

	return false
end

local function verify_identity(host, service, cert)
	if cert.setencode then
		cert:setencode("utf8");
	end
	local ext = cert:extensions()
	if ext[oid_subjectaltname] then
		local sans = ext[oid_subjectaltname];

		-- Per [TLS-CERTS] 6.3, 6.4.4, "a client MUST NOT seek a match for a
		-- reference identifier if the presented identifiers include a DNS-ID
		-- SRV-ID, URI-ID, or any application-specific identifier types"
		local had_supported_altnames = false

		if sans[oid_xmppaddr] then
			had_supported_altnames = true
			if service == "_xmpp-client" or service == "_xmpp-server" then
				if compare_xmppaddr(host, sans[oid_xmppaddr]) then return true end
			end
		end

		if sans[oid_dnssrv] then
			had_supported_altnames = true
			-- Only check srvNames if the caller specified a service
			if service and compare_srvname(host, service, sans[oid_dnssrv]) then return true end
		end

		if sans["dNSName"] then
			had_supported_altnames = true
			if compare_dnsname(host, sans["dNSName"]) then return true end
		end

		-- We don't need URIs, but [TLS-CERTS] is clear.
		if sans["uniformResourceIdentifier"] then
			had_supported_altnames = true
		end

		if had_supported_altnames then return false end
	end

	-- Extract a common name from the certificate, and check it as if it were
	-- a dNSName subjectAltName (wildcards may apply for, and receive,
	-- cat treats)
	--
	-- Per [TLS-CERTS] 1.8, a CN-ID is the Common Name from a cert subject
	-- which has one and only one Common Name
	local subject = cert:subject()
	local cn = nil
	for i=1,#subject do
		local dn = subject[i]
		if dn["oid"] == oid_commonname then
			if cn then
				log("info", "Certificate has multiple common names")
				return false
			end

			cn = dn["value"];
		end
	end

	if cn then
		-- Per [TLS-CERTS] 6.4.4, follow the comparison rules for dNSName SANs.
		return compare_dnsname(host, { cn })
	end

	-- If all else fails, well, why should we be any different?
	return false
end

-- TODO Support other SANs
local function get_identities(cert) --> map of names to sets of services
	if cert.setencode then
		cert:setencode("utf8");
	end

	local names = mt.new();

	local ext = cert:extensions();
	local sans = ext[oid_subjectaltname];
	if sans then
		if sans["dNSName"] then -- Valid for any service
			for _, name in ipairs(sans["dNSName"]) do
				local is_wildcard = name:sub(1, 2) == "*.";
				if is_wildcard then name = name:sub(3); end
				name = idna_to_unicode(nameprep(name));
				if name then
					if is_wildcard then name = "*." .. name; end
					names:set(name, "*", true);
				end
			end
		end
		if sans[oid_xmppaddr] then
			for _, name in ipairs(sans[oid_xmppaddr]) do
				name = nameprep(name);
				if name then
					names:set(name, "xmpp-client", true);
					names:set(name, "xmpp-server", true);
				end
			end
		end
		if sans[oid_dnssrv] then
			for _, srvname in ipairs(sans[oid_dnssrv]) do
				local srv, name = srvname:match("^_([^.]+)%.(.*)");
				if srv then
					name = nameprep(name);
					if name then
						names:set(name, srv, true);
					end
				end
			end
		end
	end

	local subject = cert:subject();
	for i = 1, #subject do
		local dn = subject[i];
		if dn.oid == oid_commonname then
			local name = nameprep(dn.value);
			if name and idna_to_ascii(name) then
				names:set(name, "*", true);
			end
		end
	end
	return names.data;
end

local pat = "%-%-%-%-%-BEGIN ([A-Z ]+)%-%-%-%-%-\r?\n([0-9A-Za-z+/=\r\n]*)\r?\n%-%-%-%-%-END %1%-%-%-%-%-";

local function pem2der(pem)
	local typ, data = pem:match(pat);
	if typ and data then
		return base64.decode(data), typ;
	end
end

local wrap = ('.'):rep(64);
local envelope = "-----BEGIN %s-----\n%s\n-----END %s-----\n"

local function der2pem(data, typ)
	typ = typ and typ:upper() or "CERTIFICATE";
	data = base64.encode(data);
	return s_format(envelope, typ, data:gsub(wrap, '%0\n', (#data-1)/64), typ);
end

return {
	verify_identity = verify_identity;
	get_identities = get_identities;
	pem2der = pem2der;
	der2pem = der2pem;
};