Software / code / prosody
Annotate
util/x509.lua @ 12181:783056b4e448 0.11 0.11.12
util.xml: Do not allow doctypes, comments or processing instructions
Yes. This is as bad as it sounds. CVE pending.
In Prosody itself, this only affects mod_websocket, which uses util.xml
to parse the <open/> frame, thus allowing unauthenticated remote DoS
using Billion Laughs. However, third-party modules using util.xml may
also be affected by this.
This commit installs handlers which disallow the use of doctype
declarations and processing instructions without any escape hatch. It,
by default, also introduces such a handler for comments, however, there
is a way to enable comments nontheless.
This is because util.xml is used to parse human-facing data, where
comments are generally a desirable feature, and also because comments
are generally harmless.
| author | Jonas Schäfer <jonas@wielicki.name> |
|---|---|
| date | Mon, 10 Jan 2022 18:23:54 +0100 |
| parent | 8555:4f0f5b49bb03 |
| child | 9907:54e36a8677bc |
| rev | line source |
|---|---|
| 3651 | 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 | |
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14 -- [TLS-CERTS] - http://tools.ietf.org/html/rfc6125 |
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15 -- [XMPP-CORE] - http://tools.ietf.org/html/rfc6120 |
| 3651 | 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; | |
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23 local base64 = require "util.encodings".base64; |
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24 local log = require "util.logger".init("x509"); |
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25 local s_format = string.format; |
| 3651 | 26 |
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27 local _ENV = nil; |
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28 -- luacheck: std none |
| 3651 | 29 |
| 30 local oid_commonname = "2.5.4.3"; -- [LDAP] 2.3 | |
| 31 local oid_subjectaltname = "2.5.29.17"; -- [PKIX] 4.2.1.6 | |
| 32 local oid_xmppaddr = "1.3.6.1.5.5.7.8.5"; -- [XMPP-CORE] | |
| 33 local oid_dnssrv = "1.3.6.1.5.5.7.8.7"; -- [SRV-ID] | |
| 34 | |
| 35 -- Compare a hostname (possibly international) with asserted names | |
| 36 -- extracted from a certificate. | |
| 37 -- This function follows the rules laid out in | |
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38 -- sections 6.4.1 and 6.4.2 of [TLS-CERTS] |
| 3651 | 39 -- |
| 40 -- A wildcard ("*") all by itself is allowed only as the left-most label | |
| 41 local function compare_dnsname(host, asserted_names) | |
| 42 -- TODO: Sufficient normalization? Review relevant specs. | |
| 43 local norm_host = idna_to_ascii(host) | |
| 44 if norm_host == nil then | |
| 45 log("info", "Host %s failed IDNA ToASCII operation", host) | |
| 46 return false | |
| 47 end | |
| 48 | |
| 49 norm_host = norm_host:lower() | |
| 50 | |
| 51 local host_chopped = norm_host:gsub("^[^.]+%.", "") -- everything after the first label | |
| 52 | |
| 53 for i=1,#asserted_names do | |
| 54 local name = asserted_names[i] | |
| 55 if norm_host == name:lower() then | |
| 56 log("debug", "Cert dNSName %s matched hostname", name); | |
| 57 return true | |
| 58 end | |
| 59 | |
| 60 -- Allow the left most label to be a "*" | |
| 61 if name:match("^%*%.") then | |
| 62 local rest_name = name:gsub("^[^.]+%.", "") | |
| 63 if host_chopped == rest_name:lower() then | |
| 64 log("debug", "Cert dNSName %s matched hostname", name); | |
| 65 return true | |
| 66 end | |
| 67 end | |
| 68 end | |
| 69 | |
| 70 return false | |
| 71 end | |
| 72 | |
| 73 -- Compare an XMPP domain name with the asserted id-on-xmppAddr | |
| 74 -- identities extracted from a certificate. Both are UTF8 strings. | |
| 75 -- | |
| 76 -- Per [XMPP-CORE], matches against asserted identities don't include | |
| 77 -- wildcards, so we just do a normalize on both and then a string comparison | |
| 78 -- | |
| 79 -- TODO: Support for full JIDs? | |
| 80 local function compare_xmppaddr(host, asserted_names) | |
| 81 local norm_host = nameprep(host) | |
| 82 | |
| 83 for i=1,#asserted_names do | |
| 84 local name = asserted_names[i] | |
| 85 | |
| 86 -- We only want to match against bare domains right now, not | |
| 87 -- those crazy full-er JIDs. | |
| 88 if name:match("[@/]") then | |
| 89 log("debug", "Ignoring xmppAddr %s because it's not a bare domain", name) | |
| 90 else | |
| 91 local norm_name = nameprep(name) | |
| 92 if norm_name == nil then | |
| 93 log("info", "Ignoring xmppAddr %s, failed nameprep!", name) | |
| 94 else | |
| 95 if norm_host == norm_name then | |
| 96 log("debug", "Cert xmppAddr %s matched hostname", name) | |
| 97 return true | |
| 98 end | |
| 99 end | |
| 100 end | |
| 101 end | |
| 102 | |
| 103 return false | |
| 104 end | |
| 105 | |
| 106 -- Compare a host + service against the asserted id-on-dnsSRV (SRV-ID) | |
| 107 -- identities extracted from a certificate. | |
| 108 -- | |
| 109 -- Per [SRV-ID], the asserted identities will be encoded in ASCII via ToASCII. | |
| 110 -- Comparison is done case-insensitively, and a wildcard ("*") all by itself | |
| 111 -- is allowed only as the left-most non-service label. | |
| 112 local function compare_srvname(host, service, asserted_names) | |
| 113 local norm_host = idna_to_ascii(host) | |
| 114 if norm_host == nil then | |
| 115 log("info", "Host %s failed IDNA ToASCII operation", host); | |
| 116 return false | |
| 117 end | |
| 118 | |
| 119 -- Service names start with a "_" | |
| 120 if service:match("^_") == nil then service = "_"..service end | |
| 121 | |
| 122 norm_host = norm_host:lower(); | |
| 123 local host_chopped = norm_host:gsub("^[^.]+%.", "") -- everything after the first label | |
| 124 | |
| 125 for i=1,#asserted_names do | |
| 126 local asserted_service, name = asserted_names[i]:match("^(_[^.]+)%.(.*)"); | |
| 127 if service == asserted_service then | |
| 128 if norm_host == name:lower() then | |
| 129 log("debug", "Cert SRVName %s matched hostname", name); | |
| 130 return true; | |
| 131 end | |
| 132 | |
| 133 -- Allow the left most label to be a "*" | |
| 134 if name:match("^%*%.") then | |
| 135 local rest_name = name:gsub("^[^.]+%.", "") | |
| 136 if host_chopped == rest_name:lower() then | |
| 137 log("debug", "Cert SRVName %s matched hostname", name) | |
| 138 return true | |
| 139 end | |
| 140 end | |
| 141 if norm_host == name:lower() then | |
| 142 log("debug", "Cert SRVName %s matched hostname", name); | |
| 143 return true | |
| 144 end | |
| 145 end | |
| 146 end | |
| 147 | |
| 148 return false | |
| 149 end | |
| 150 | |
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151 local function verify_identity(host, service, cert) |
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152 if cert.setencode then |
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153 cert:setencode("utf8"); |
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154 end |
| 3651 | 155 local ext = cert:extensions() |
| 156 if ext[oid_subjectaltname] then | |
| 157 local sans = ext[oid_subjectaltname]; | |
| 158 | |
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159 -- Per [TLS-CERTS] 6.3, 6.4.4, "a client MUST NOT seek a match for a |
| 3651 | 160 -- reference identifier if the presented identifiers include a DNS-ID |
| 161 -- SRV-ID, URI-ID, or any application-specific identifier types" | |
| 162 local had_supported_altnames = false | |
| 163 | |
| 164 if sans[oid_xmppaddr] then | |
| 165 had_supported_altnames = true | |
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166 if service == "_xmpp-client" or service == "_xmpp-server" then |
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167 if compare_xmppaddr(host, sans[oid_xmppaddr]) then return true end |
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168 end |
| 3651 | 169 end |
| 170 | |
| 171 if sans[oid_dnssrv] then | |
| 172 had_supported_altnames = true | |
| 173 -- Only check srvNames if the caller specified a service | |
| 174 if service and compare_srvname(host, service, sans[oid_dnssrv]) then return true end | |
| 175 end | |
| 176 | |
| 177 if sans["dNSName"] then | |
| 178 had_supported_altnames = true | |
| 179 if compare_dnsname(host, sans["dNSName"]) then return true end | |
| 180 end | |
| 181 | |
| 182 -- We don't need URIs, but [TLS-CERTS] is clear. | |
| 183 if sans["uniformResourceIdentifier"] then | |
| 184 had_supported_altnames = true | |
| 185 end | |
| 186 | |
| 187 if had_supported_altnames then return false end | |
| 188 end | |
| 189 | |
| 190 -- Extract a common name from the certificate, and check it as if it were | |
| 191 -- a dNSName subjectAltName (wildcards may apply for, and receive, | |
| 192 -- cat treats) | |
| 193 -- | |
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194 -- Per [TLS-CERTS] 1.8, a CN-ID is the Common Name from a cert subject |
| 3651 | 195 -- which has one and only one Common Name |
| 196 local subject = cert:subject() | |
| 197 local cn = nil | |
| 198 for i=1,#subject do | |
| 199 local dn = subject[i] | |
| 200 if dn["oid"] == oid_commonname then | |
| 201 if cn then | |
| 202 log("info", "Certificate has multiple common names") | |
| 203 return false | |
| 204 end | |
| 205 | |
| 206 cn = dn["value"]; | |
| 207 end | |
| 208 end | |
| 209 | |
| 210 if cn then | |
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211 -- Per [TLS-CERTS] 6.4.4, follow the comparison rules for dNSName SANs. |
| 3651 | 212 return compare_dnsname(host, { cn }) |
| 213 end | |
| 214 | |
| 215 -- If all else fails, well, why should we be any different? | |
| 216 return false | |
| 217 end | |
| 218 | |
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219 local pat = "%-%-%-%-%-BEGIN ([A-Z ]+)%-%-%-%-%-\r?\n".. |
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220 "([0-9A-Za-z+/=\r\n]*)\r?\n%-%-%-%-%-END %1%-%-%-%-%-"; |
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221 |
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222 local function pem2der(pem) |
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223 local typ, data = pem:match(pat); |
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224 if typ and data then |
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225 return base64.decode(data), typ; |
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226 end |
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227 end |
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228 |
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229 local wrap = ('.'):rep(64); |
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230 local envelope = "-----BEGIN %s-----\n%s\n-----END %s-----\n" |
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231 |
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232 local function der2pem(data, typ) |
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233 typ = typ and typ:upper() or "CERTIFICATE"; |
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234 data = base64.encode(data); |
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235 return s_format(envelope, typ, data:gsub(wrap, '%0\n', (#data-1)/64), typ); |
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236 end |
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237 |
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238 return { |
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239 verify_identity = verify_identity; |
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240 pem2der = pem2der; |
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241 der2pem = der2pem; |
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242 }; |
