--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/util/certverification.lua Sun Nov 21 21:10:43 2010 -0800
@@ -0,0 +1,211 @@
+-- Prosody IM
+-- Copyright (C) 2010 Matthew Wild
+-- Copyright (C) 2010 Paul Aurich
+--
+-- This project is MIT/X11 licensed. Please see the
+-- COPYING file in the source package for more information.
+--
+
+-- TODO: I feel a fair amount of this logic should be integrated into Luasec,
+-- so that everyone isn't re-inventing the wheel. Dependencies on
+-- IDN libraries complicate that.
+
+
+-- [TLS-CERTS] - http://tools.ietf.org/html/draft-saintandre-tls-server-id-check-10
+-- [XMPP-CORE] - http://tools.ietf.org/html/draft-ietf-xmpp-3920bis-18
+-- [SRV-ID] - http://tools.ietf.org/html/rfc4985
+-- [IDNA] - http://tools.ietf.org/html/rfc5890
+-- [LDAP] - http://tools.ietf.org/html/rfc4519
+-- [PKIX] - http://tools.ietf.org/html/rfc5280
+
+local nameprep = require "util.encodings".stringprep.nameprep;
+local idna_to_ascii = require "util.encodings".idna.to_ascii;
+local log = require "util.logger".init("certverification");
+
+module "certverification"
+
+local oid_commonname = "2.5.4.3"; -- [LDAP] 2.3
+local oid_subjectaltname = "2.5.29.17"; -- [PKIX] 4.2.1.6
+local oid_xmppaddr = "1.3.6.1.5.5.7.8.5"; -- [XMPP-CORE]
+local oid_dnssrv = "1.3.6.1.5.5.7.8.7"; -- [SRV-ID]
+
+-- Compare a hostname (possibly international) with asserted names
+-- extracted from a certificate.
+-- This function follows the rules laid out in
+-- sections 4.4.1 and 4.4.2 of [TLS-CERTS]
+--
+-- A wildcard ("*") all by itself is allowed only as the left-most label
+local function compare_dnsname(host, asserted_names)
+ -- TODO: Sufficient normalization? Review relevant specs.
+ local norm_host = idna_to_ascii(host)
+ if norm_host == nil then
+ log("info", "Host %s failed IDNA ToASCII operation", host)
+ return false
+ end
+
+ norm_host = norm_host:lower()
+
+ local host_chopped = norm_host:gsub("^[^.]+%.", "") -- everything after the first label
+
+ for i=1,#asserted_names do
+ local name = asserted_names[i]
+ if norm_host == name:lower() then
+ log("debug", "Cert dNSName %s matched hostname", name);
+ return true
+ end
+
+ -- Allow the left most label to be a "*"
+ if name:match("^%*%.") then
+ local rest_name = name:gsub("^[^.]+%.", "")
+ if host_chopped == rest_name:lower() then
+ log("debug", "Cert dNSName %s matched hostname", name);
+ return true
+ end
+ end
+ end
+
+ return false
+end
+
+-- Compare an XMPP domain name with the asserted id-on-xmppAddr
+-- identities extracted from a certificate. Both are UTF8 strings.
+--
+-- Per [XMPP-CORE], matches against asserted identities don't include
+-- wildcards, so we just do a normalize on both and then a string comparison
+--
+-- TODO: Support for full JIDs?
+local function compare_xmppaddr(host, asserted_names)
+ local norm_host = nameprep(host)
+
+ for i=1,#asserted_names do
+ local name = asserted_names[i]
+
+ -- We only want to match against bare domains right now, not
+ -- those crazy full-er JIDs.
+ if name:match("[@/]") then
+ log("debug", "Ignoring xmppAddr %s because it's not a bare domain", name)
+ else
+ local norm_name = nameprep(name)
+ if norm_name == nil then
+ log("info", "Ignoring xmppAddr %s, failed nameprep!", name)
+ else
+ if norm_host == norm_name then
+ log("debug", "Cert xmppAddr %s matched hostname", name)
+ return true
+ end
+ end
+ end
+ end
+
+ return false
+end
+
+-- Compare a host + service against the asserted id-on-dnsSRV (SRV-ID)
+-- identities extracted from a certificate.
+--
+-- Per [SRV-ID], the asserted identities will be encoded in ASCII via ToASCII.
+-- Comparison is done case-insensitively, and a wildcard ("*") all by itself
+-- is allowed only as the left-most non-service label.
+local function compare_srvname(host, service, asserted_names)
+ local norm_host = idna_to_ascii(host)
+ if norm_host == nil then
+ log("info", "Host %s failed IDNA ToASCII operation", host);
+ return false
+ end
+
+ -- Service names start with a "_"
+ if service:match("^_") == nil then service = "_"..service end
+
+ norm_host = norm_host:lower();
+ local host_chopped = norm_host:gsub("^[^.]+%.", "") -- everything after the first label
+
+ for i=1,#asserted_names do
+ local asserted_service, name = asserted_names[i]:match("^(_[^.]+)%.(.*)");
+ if service == asserted_service then
+ if norm_host == name:lower() then
+ log("debug", "Cert SRVName %s matched hostname", name);
+ return true;
+ end
+
+ -- Allow the left most label to be a "*"
+ if name:match("^%*%.") then
+ local rest_name = name:gsub("^[^.]+%.", "")
+ if host_chopped == rest_name:lower() then
+ log("debug", "Cert SRVName %s matched hostname", name)
+ return true
+ end
+ end
+ if norm_host == name:lower() then
+ log("debug", "Cert SRVName %s matched hostname", name);
+ return true
+ end
+ end
+ end
+
+ return false
+end
+
+function verify_identity(host, service, cert)
+ local ext = cert:extensions()
+ if ext[oid_subjectaltname] then
+ local sans = ext[oid_subjectaltname];
+
+ -- Per [TLS-CERTS] 4.3, 4.4.4, "a client MUST NOT seek a match for a
+ -- reference identifier if the presented identifiers include a DNS-ID
+ -- SRV-ID, URI-ID, or any application-specific identifier types"
+ local had_supported_altnames = false
+
+ if sans[oid_xmppaddr] then
+ had_supported_altnames = true
+ if compare_xmppaddr(host, sans[oid_xmppaddr]) then return true end
+ end
+
+ if sans[oid_dnssrv] then
+ had_supported_altnames = true
+ -- Only check srvNames if the caller specified a service
+ if service and compare_srvname(host, service, sans[oid_dnssrv]) then return true end
+ end
+
+ if sans["dNSName"] then
+ had_supported_altnames = true
+ if compare_dnsname(host, sans["dNSName"]) then return true end
+ end
+
+ -- We don't need URIs, but [TLS-CERTS] is clear.
+ if sans["uniformResourceIdentifier"] then
+ had_supported_altnames = true
+ end
+
+ if had_supported_altnames then return false end
+ end
+
+ -- Extract a common name from the certificate, and check it as if it were
+ -- a dNSName subjectAltName (wildcards may apply for, and receive,
+ -- cat treats)
+ --
+ -- Per [TLS-CERTS] 1.5, a CN-ID is the Common Name from a cert subject
+ -- which has one and only one Common Name
+ local subject = cert:subject()
+ local cn = nil
+ for i=1,#subject do
+ local dn = subject[i]
+ if dn["oid"] == oid_commonname then
+ if cn then
+ log("info", "Certificate has multiple common names")
+ return false
+ end
+
+ cn = dn["value"];
+ end
+ end
+
+ if cn then
+ -- Per [TLS-CERTS] 4.4.4, follow the comparison rules for dNSName SANs.
+ return compare_dnsname(host, { cn })
+ end
+
+ -- If all else fails, well, why should we be any different?
+ return false
+end
+
+return _M;