prosody
26571a99f6e6
util/x509.lua

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util/x509.lua @ 3733:26571a99f6e6

core.s2smanager, mod_console, mod_saslauth, util.certverification: rename util.certverification to util.x509
author Kim Alvefur <zash@zash.se>
date Sun, 12 Dec 2010 02:03:32 +0100
parent 3651:util/certverification.lua@337391d34b70
child 3735:40b54c46a14c
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3732:bf449ecf2144 3733:26571a99f6e6
1 -- Prosody IM
2 -- Copyright (C) 2010 Matthew Wild
3 -- Copyright (C) 2010 Paul Aurich
4 --
5 -- This project is MIT/X11 licensed. Please see the
6 -- COPYING file in the source package for more information.
7 --
8
9 -- TODO: I feel a fair amount of this logic should be integrated into Luasec,
10 -- so that everyone isn't re-inventing the wheel. Dependencies on
11 -- IDN libraries complicate that.
12
13
14 -- [TLS-CERTS] - http://tools.ietf.org/html/draft-saintandre-tls-server-id-check-10
15 -- [XMPP-CORE] - http://tools.ietf.org/html/draft-ietf-xmpp-3920bis-18
16 -- [SRV-ID] - http://tools.ietf.org/html/rfc4985
17 -- [IDNA] - http://tools.ietf.org/html/rfc5890
18 -- [LDAP] - http://tools.ietf.org/html/rfc4519
19 -- [PKIX] - http://tools.ietf.org/html/rfc5280
20
21 local nameprep = require "util.encodings".stringprep.nameprep;
22 local idna_to_ascii = require "util.encodings".idna.to_ascii;
23 local log = require "util.logger".init("certverification");
24
25 module "certverification"
26
27 local oid_commonname = "2.5.4.3"; -- [LDAP] 2.3
28 local oid_subjectaltname = "2.5.29.17"; -- [PKIX] 4.2.1.6
29 local oid_xmppaddr = "1.3.6.1.5.5.7.8.5"; -- [XMPP-CORE]
30 local oid_dnssrv = "1.3.6.1.5.5.7.8.7"; -- [SRV-ID]
31
32 -- Compare a hostname (possibly international) with asserted names
33 -- extracted from a certificate.
34 -- This function follows the rules laid out in
35 -- sections 4.4.1 and 4.4.2 of [TLS-CERTS]
36 --
37 -- A wildcard ("*") all by itself is allowed only as the left-most label
38 local function compare_dnsname(host, asserted_names)
39 -- TODO: Sufficient normalization? Review relevant specs.
40 local norm_host = idna_to_ascii(host)
41 if norm_host == nil then
42 log("info", "Host %s failed IDNA ToASCII operation", host)
43 return false
44 end
45
46 norm_host = norm_host:lower()
47
48 local host_chopped = norm_host:gsub("^[^.]+%.", "") -- everything after the first label
49
50 for i=1,#asserted_names do
51 local name = asserted_names[i]
52 if norm_host == name:lower() then
53 log("debug", "Cert dNSName %s matched hostname", name);
54 return true
55 end
56
57 -- Allow the left most label to be a "*"
58 if name:match("^%*%.") then
59 local rest_name = name:gsub("^[^.]+%.", "")
60 if host_chopped == rest_name:lower() then
61 log("debug", "Cert dNSName %s matched hostname", name);
62 return true
63 end
64 end
65 end
66
67 return false
68 end
69
70 -- Compare an XMPP domain name with the asserted id-on-xmppAddr
71 -- identities extracted from a certificate. Both are UTF8 strings.
72 --
73 -- Per [XMPP-CORE], matches against asserted identities don't include
74 -- wildcards, so we just do a normalize on both and then a string comparison
75 --
76 -- TODO: Support for full JIDs?
77 local function compare_xmppaddr(host, asserted_names)
78 local norm_host = nameprep(host)
79
80 for i=1,#asserted_names do
81 local name = asserted_names[i]
82
83 -- We only want to match against bare domains right now, not
84 -- those crazy full-er JIDs.
85 if name:match("[@/]") then
86 log("debug", "Ignoring xmppAddr %s because it's not a bare domain", name)
87 else
88 local norm_name = nameprep(name)
89 if norm_name == nil then
90 log("info", "Ignoring xmppAddr %s, failed nameprep!", name)
91 else
92 if norm_host == norm_name then
93 log("debug", "Cert xmppAddr %s matched hostname", name)
94 return true
95 end
96 end
97 end
98 end
99
100 return false
101 end
102
103 -- Compare a host + service against the asserted id-on-dnsSRV (SRV-ID)
104 -- identities extracted from a certificate.
105 --
106 -- Per [SRV-ID], the asserted identities will be encoded in ASCII via ToASCII.
107 -- Comparison is done case-insensitively, and a wildcard ("*") all by itself
108 -- is allowed only as the left-most non-service label.
109 local function compare_srvname(host, service, asserted_names)
110 local norm_host = idna_to_ascii(host)
111 if norm_host == nil then
112 log("info", "Host %s failed IDNA ToASCII operation", host);
113 return false
114 end
115
116 -- Service names start with a "_"
117 if service:match("^_") == nil then service = "_"..service end
118
119 norm_host = norm_host:lower();
120 local host_chopped = norm_host:gsub("^[^.]+%.", "") -- everything after the first label
121
122 for i=1,#asserted_names do
123 local asserted_service, name = asserted_names[i]:match("^(_[^.]+)%.(.*)");
124 if service == asserted_service then
125 if norm_host == name:lower() then
126 log("debug", "Cert SRVName %s matched hostname", name);
127 return true;
128 end
129
130 -- Allow the left most label to be a "*"
131 if name:match("^%*%.") then
132 local rest_name = name:gsub("^[^.]+%.", "")
133 if host_chopped == rest_name:lower() then
134 log("debug", "Cert SRVName %s matched hostname", name)
135 return true
136 end
137 end
138 if norm_host == name:lower() then
139 log("debug", "Cert SRVName %s matched hostname", name);
140 return true
141 end
142 end
143 end
144
145 return false
146 end
147
148 function verify_identity(host, service, cert)
149 local ext = cert:extensions()
150 if ext[oid_subjectaltname] then
151 local sans = ext[oid_subjectaltname];
152
153 -- Per [TLS-CERTS] 4.3, 4.4.4, "a client MUST NOT seek a match for a
154 -- reference identifier if the presented identifiers include a DNS-ID
155 -- SRV-ID, URI-ID, or any application-specific identifier types"
156 local had_supported_altnames = false
157
158 if sans[oid_xmppaddr] then
159 had_supported_altnames = true
160 if compare_xmppaddr(host, sans[oid_xmppaddr]) then return true end
161 end
162
163 if sans[oid_dnssrv] then
164 had_supported_altnames = true
165 -- Only check srvNames if the caller specified a service
166 if service and compare_srvname(host, service, sans[oid_dnssrv]) then return true end
167 end
168
169 if sans["dNSName"] then
170 had_supported_altnames = true
171 if compare_dnsname(host, sans["dNSName"]) then return true end
172 end
173
174 -- We don't need URIs, but [TLS-CERTS] is clear.
175 if sans["uniformResourceIdentifier"] then
176 had_supported_altnames = true
177 end
178
179 if had_supported_altnames then return false end
180 end
181
182 -- Extract a common name from the certificate, and check it as if it were
183 -- a dNSName subjectAltName (wildcards may apply for, and receive,
184 -- cat treats)
185 --
186 -- Per [TLS-CERTS] 1.5, a CN-ID is the Common Name from a cert subject
187 -- which has one and only one Common Name
188 local subject = cert:subject()
189 local cn = nil
190 for i=1,#subject do
191 local dn = subject[i]
192 if dn["oid"] == oid_commonname then
193 if cn then
194 log("info", "Certificate has multiple common names")
195 return false
196 end
197
198 cn = dn["value"];
199 end
200 end
201
202 if cn then
203 -- Per [TLS-CERTS] 4.4.4, follow the comparison rules for dNSName SANs.
204 return compare_dnsname(host, { cn })
205 end
206
207 -- If all else fails, well, why should we be any different?
208 return false
209 end
210
211 return _M;