util/x509.lua

   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/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
  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("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;
  28
  29 module "x509"
  30
  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]
  35
  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]
  40 --
  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)
  47                 return false
  48         end
  49
  50         norm_host = norm_host:lower()
  51
  52         local host_chopped = norm_host:gsub("^[^.]+%.", "") -- everything after the first label
  53
  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);
  58                         return true
  59                 end
  60
  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);
  66                                 return true
  67                         end
  68                 end
  69         end
  70
  71         return false
  72 end
  73
  74 -- Compare an XMPP domain name with the asserted id-on-xmppAddr
  75 -- identities extracted from a certificate.  Both are UTF8 strings.
  76 --
  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
  79 --
  80 -- TODO: Support for full JIDs?
  81 local function compare_xmppaddr(host, asserted_names)
  82         local norm_host = nameprep(host)
  83
  84         for i=1,#asserted_names do
  85                 local name = asserted_names[i]
  86
  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)
  91                 else
  92                         local norm_name = nameprep(name)
  93                         if norm_name == nil then
  94                                 log("info", "Ignoring xmppAddr %s, failed nameprep!", name)
  95                         else
  96                                 if norm_host == norm_name then
  97                                         log("debug", "Cert xmppAddr %s matched hostname", name)
  98                                         return true
  99                                 end
 100                         end
 101                 end
 102         end
 103
 104         return false
 105 end
 106
 107 -- Compare a host + service against the asserted id-on-dnsSRV (SRV-ID)
 108 -- identities extracted from a certificate.
 109 --
 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);
 117                 return false
 118         end
 119
 120         -- Service names start with a "_"
 121         if service:match("^_") == nil then service = "_"..service end
 122
 123         norm_host = norm_host:lower();
 124         local host_chopped = norm_host:gsub("^[^.]+%.", "") -- everything after the first label
 125
 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);
 131                                 return true;
 132                         end
 133
 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)
 139                                         return true
 140                                 end
 141                         end
 142                         if norm_host == name:lower() then
 143                                 log("debug", "Cert SRVName %s matched hostname", name);
 144                                 return true
 145                         end
 146                 end
 147         end
 148
 149         return false
 150 end
 151
 152 function verify_identity(host, service, cert)
 153         local ext = cert:extensions()
 154         if ext[oid_subjectaltname] then
 155                 local sans = ext[oid_subjectaltname];
 156
 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
 161
 162                 if sans[oid_xmppaddr] then
 163                         had_supported_altnames = true
 164                         if compare_xmppaddr(host, sans[oid_xmppaddr]) then return true end
 165                 end
 166
 167                 if sans[oid_dnssrv] then
 168                         had_supported_altnames = true
 169                         -- Only check srvNames if the caller specified a service
 170                         if service and compare_srvname(host, service, sans[oid_dnssrv]) then return true end
 171                 end
 172
 173                 if sans["dNSName"] then
 174                         had_supported_altnames = true
 175                         if compare_dnsname(host, sans["dNSName"]) then return true end
 176                 end
 177
 178                 -- We don't need URIs, but [TLS-CERTS] is clear.
 179                 if sans["uniformResourceIdentifier"] then
 180                         had_supported_altnames = true
 181                 end
 182
 183                 if had_supported_altnames then return false end
 184         end
 185
 186         -- Extract a common name from the certificate, and check it as if it were
 187         -- a dNSName subjectAltName (wildcards may apply for, and receive,
 188         -- cat treats)
 189         --
 190         -- Per [TLS-CERTS] 1.8, a CN-ID is the Common Name from a cert subject
 191         -- which has one and only one Common Name
 192         local subject = cert:subject()
 193         local cn = nil
 194         for i=1,#subject do
 195                 local dn = subject[i]
 196                 if dn["oid"] == oid_commonname then
 197                         if cn then
 198                                 log("info", "Certificate has multiple common names")
 199                                 return false
 200                         end
 201
 202                         cn = dn["value"];
 203                 end
 204         end
 205
 206         if cn then
 207                 -- Per [TLS-CERTS] 6.4.4, follow the comparison rules for dNSName SANs.
 208                 return compare_dnsname(host, { cn })
 209         end
 210
 211         -- If all else fails, well, why should we be any different?
 212         return false
 213 end
 214
 215 -- TODO Rename? Split out subroutines?
 216 -- Also, this is probably openssl specific, what TODO about that?
 217 function genx509san(hosts, config, certhosts, raw) -- recive config through that or some better way?
 218         local function utf8string(s)
 219                 -- This is how we tell openssl not to encode UTF-8 strings as Latin1
 220                 return s_format("FORMAT:UTF8,UTF8:%s", s);
 221         end
 222
 223         local function ia5string(s)
 224                 return s_format("IA5STRING:%s", s);
 225         end
 226
 227         local function dnsname(t, host)
 228                 t_insert(t.DNS, idna_to_ascii(host));
 229         end
 230
 231         local function srvname(t, host, service)
 232                 t_insert(t.otherName, s_format("%s;%s", oid_dnssrv, ia5string("_" .. service .."." .. idna_to_ascii(host))));
 233         end
 234
 235         local function xmppAddr(t, host)
 236                 t_insert(t.otherName, s_format("%s;%s", oid_xmppaddr, utf8string(host)));
 237         end
 238
 239         -----------------------------
 240
 241         local san = {
 242                 DNS = {};
 243                 otherName = {};
 244         };
 245
 246         local sslsanconf = { };
 247
 248         for i = 1,#certhosts do
 249                 local certhost = certhosts[i];
 250                 for name, host in pairs(hosts) do
 251                         if name == certhost or name:sub(-1-#certhost) == "."..certhost then
 252                                 dnsname(san, name);
 253                                 --print(name .. "#component_module: " .. (config.get(name, "core", "component_module") or "nil"));
 254                                 if config.get(name, "core", "component_module") == nil then
 255                                         srvname(san, name, "xmpp-client");
 256                                 end
 257                                 --print(name .. "#anonymous_login: " .. tostring(config.get(name, "core", "anonymous_login")));
 258                                 if not (config.get(name, "core", "anonymous_login") or
 259                                                 config.get(name, "core", "authentication") == "anonymous") then
 260                                         srvname(san, name, "xmpp-server");
 261                                 end
 262                                 xmppAddr(san, name);
 263                         end
 264                 end
 265         end
 266
 267         for t, n in pairs(san) do
 268                 for i = 1,#n do
 269                         t_insert(sslsanconf, s_format("%s.%d = %s", t, i -1, n[i]));
 270                 end
 271         end
 272
 273         return raw and sslsanconf or t_concat(sslsanconf, "\n");
 274 end
 275
 276 function baseconf()
 277         return {
 278                 req = {
 279                         distinguished_name = "distinguished_name",
 280                         req_extensions = "v3_extensions",
 281                         x509_extensions = "v3_extensions",
 282                         prompt = "no",
 283                 },
 284                 distinguished_name = {
 285                         commonName = "example.com",
 286                         countryName = "GB",
 287                         localityName = "The Internet",
 288                         organizationName = "Your Organisation",
 289                         organizationalUnitName = "XMPP Department",
 290                         emailAddress = "xmpp@example.com",
 291                 },
 292                 v3_extensions = {
 293                         basicConstraints = "CA:FALSE",
 294                         keyUsage = "digitalSignature,keyEncipherment",
 295                         extendedKeyUsage = "serverAuth,clientAuth",
 296                         subjectAltName = "@subject_alternative_name",
 297                 },
 298                 subject_alternative_name = { },
 299         }
 300 end
 301
 302 function serialize_conf(conf)
 303         local s = "";
 304         for k, t in pairs(conf) do
 305                 s = s .. ("[%s]\n"):format(k);
 306                 if t[1] then
 307                         for i, v in ipairs(t) do
 308                                 s = s .. ("%s\n"):format(v);
 309                         end
 310                 else
 311                         for k, v in pairs(t) do
 312                                 s = s .. ("%s = %s\n"):format(k, v);
 313                         end
 314                 end
 315                 s = s .. "\n";
 316         end
 317         return s;
 318 end
 319
 320 return _M;