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