diff options
Diffstat (limited to 'util')
| -rw-r--r-- | util/certverification.lua | 211 |
1 files changed, 211 insertions, 0 deletions
diff --git a/util/certverification.lua b/util/certverification.lua new file mode 100644 index 00000000..d323f4b4 --- /dev/null +++ b/util/certverification.lua @@ -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; |