2 -- Copyright (C) 2010 Matthew Wild
3 -- Copyright (C) 2010 Paul Aurich
5 -- This project is MIT/X11 licensed. Please see the
6 -- COPYING file in the source package for more information.
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.
14 -- [TLS-CERTS] - http://tools.ietf.org/html/rfc6125
15 -- [XMPP-CORE] - http://tools.ietf.org/html/rfc6120
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
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("x509");
24 local pairs, ipairs = pairs, ipairs;
25 local s_format = string.format;
26 local t_insert = table.insert;
27 local t_concat = table.concat;
31 local oid_commonname = "2.5.4.3"; -- [LDAP] 2.3
32 local oid_subjectaltname = "2.5.29.17"; -- [PKIX] 4.2.1.6
33 local oid_xmppaddr = "1.3.6.1.5.5.7.8.5"; -- [XMPP-CORE]
34 local oid_dnssrv = "1.3.6.1.5.5.7.8.7"; -- [SRV-ID]
36 -- Compare a hostname (possibly international) with asserted names
37 -- extracted from a certificate.
38 -- This function follows the rules laid out in
39 -- sections 6.4.1 and 6.4.2 of [TLS-CERTS]
41 -- A wildcard ("*") all by itself is allowed only as the left-most label
42 local function compare_dnsname(host, asserted_names)
43 -- TODO: Sufficient normalization? Review relevant specs.
44 local norm_host = idna_to_ascii(host)
45 if norm_host == nil then
46 log("info", "Host %s failed IDNA ToASCII operation", host)
50 norm_host = norm_host:lower()
52 local host_chopped = norm_host:gsub("^[^.]+%.", "") -- everything after the first label
54 for i=1,#asserted_names do
55 local name = asserted_names[i]
56 if norm_host == name:lower() then
57 log("debug", "Cert dNSName %s matched hostname", name);
61 -- Allow the left most label to be a "*"
62 if name:match("^%*%.") then
63 local rest_name = name:gsub("^[^.]+%.", "")
64 if host_chopped == rest_name:lower() then
65 log("debug", "Cert dNSName %s matched hostname", name);
74 -- Compare an XMPP domain name with the asserted id-on-xmppAddr
75 -- identities extracted from a certificate. Both are UTF8 strings.
77 -- Per [XMPP-CORE], matches against asserted identities don't include
78 -- wildcards, so we just do a normalize on both and then a string comparison
80 -- TODO: Support for full JIDs?
81 local function compare_xmppaddr(host, asserted_names)
82 local norm_host = nameprep(host)
84 for i=1,#asserted_names do
85 local name = asserted_names[i]
87 -- We only want to match against bare domains right now, not
88 -- those crazy full-er JIDs.
89 if name:match("[@/]") then
90 log("debug", "Ignoring xmppAddr %s because it's not a bare domain", name)
92 local norm_name = nameprep(name)
93 if norm_name == nil then
94 log("info", "Ignoring xmppAddr %s, failed nameprep!", name)
96 if norm_host == norm_name then
97 log("debug", "Cert xmppAddr %s matched hostname", name)
107 -- Compare a host + service against the asserted id-on-dnsSRV (SRV-ID)
108 -- identities extracted from a certificate.
110 -- Per [SRV-ID], the asserted identities will be encoded in ASCII via ToASCII.
111 -- Comparison is done case-insensitively, and a wildcard ("*") all by itself
112 -- is allowed only as the left-most non-service label.
113 local function compare_srvname(host, service, asserted_names)
114 local norm_host = idna_to_ascii(host)
115 if norm_host == nil then
116 log("info", "Host %s failed IDNA ToASCII operation", host);
120 -- Service names start with a "_"
121 if service:match("^_") == nil then service = "_"..service end
123 norm_host = norm_host:lower();
124 local host_chopped = norm_host:gsub("^[^.]+%.", "") -- everything after the first label
126 for i=1,#asserted_names do
127 local asserted_service, name = asserted_names[i]:match("^(_[^.]+)%.(.*)");
128 if service == asserted_service then
129 if norm_host == name:lower() then
130 log("debug", "Cert SRVName %s matched hostname", name);
134 -- Allow the left most label to be a "*"
135 if name:match("^%*%.") then
136 local rest_name = name:gsub("^[^.]+%.", "")
137 if host_chopped == rest_name:lower() then
138 log("debug", "Cert SRVName %s matched hostname", name)
142 if norm_host == name:lower() then
143 log("debug", "Cert SRVName %s matched hostname", name);
152 function verify_identity(host, service, cert)
153 local ext = cert:extensions()
154 if ext[oid_subjectaltname] then
155 local sans = ext[oid_subjectaltname];
157 -- Per [TLS-CERTS] 6.3, 6.4.4, "a client MUST NOT seek a match for a
158 -- reference identifier if the presented identifiers include a DNS-ID
159 -- SRV-ID, URI-ID, or any application-specific identifier types"
160 local had_supported_altnames = false
162 if sans[oid_xmppaddr] then
163 had_supported_altnames = true
164 if service == "_xmpp-client" or service == "_xmpp-server" then
165 if compare_xmppaddr(host, sans[oid_xmppaddr]) then return true end
169 if sans[oid_dnssrv] then
170 had_supported_altnames = true
171 -- Only check srvNames if the caller specified a service
172 if service and compare_srvname(host, service, sans[oid_dnssrv]) then return true end
175 if sans["dNSName"] then
176 had_supported_altnames = true
177 if compare_dnsname(host, sans["dNSName"]) then return true end
180 -- We don't need URIs, but [TLS-CERTS] is clear.
181 if sans["uniformResourceIdentifier"] then
182 had_supported_altnames = true
185 if had_supported_altnames then return false end
188 -- Extract a common name from the certificate, and check it as if it were
189 -- a dNSName subjectAltName (wildcards may apply for, and receive,
192 -- Per [TLS-CERTS] 1.8, a CN-ID is the Common Name from a cert subject
193 -- which has one and only one Common Name
194 local subject = cert:subject()
197 local dn = subject[i]
198 if dn["oid"] == oid_commonname then
200 log("info", "Certificate has multiple common names")
209 -- Per [TLS-CERTS] 6.4.4, follow the comparison rules for dNSName SANs.
210 return compare_dnsname(host, { cn })
213 -- If all else fails, well, why should we be any different?