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-- 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;
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