verify: pick up responders

Fix: indutny#18
lukeadickinson · Apr 3, 2017 · 6ed19f0 · 6ed19f0
1 parent 0e1af74
commit 6ed19f0
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Showing 3 changed files with 82 additions and 27 deletions.
diff --git a/lib/ocsp/utils.js b/lib/ocsp/utils.js
@@ -8,6 +8,7 @@ var asn1 = require('asn1.js');
 var rfc2560 = require('asn1.js-rfc2560');
 
 exports['id-ad-caIssuers'] = [ 1, 3, 6, 1, 5, 5, 7, 48, 2 ];
+exports['id-kp-OCSPSigning'] = [ 1, 3, 6, 1, 5, 5, 7, 3, 9 ];
 
 exports.getResponse = function getResponse(uri, req, cb) {
   uri = url.parse(uri);
@@ -74,17 +75,40 @@ exports.parseResponse = function parseResponse(raw) {
   var bytes = response.responseBytes.response;
 
   var tbs = { start: body.start, end: body.end };
+  var certsTbs = [];
   var basic = rfc2560.BasicOCSPResponse.decode(bytes, 'der', {
     track: function(key, start, end, type) {
-      if (type !== 'tagged' || key !== 'tbsResponseData')
+      if (type !== 'tagged')
         return;
 
-      tbs.start = body.start + start;
-      tbs.end = body.start + end;
+      if (key === 'tbsResponseData') {
+        tbs.start = body.start + start;
+        tbs.end = body.start + end;
+      } else if (key === 'certs/tbsCertificate') {
+        certsTbs.push({ start: body.start + start, end: body.start + end });
+      }
     }
   });
 
-  return { start: tbs.start, end: tbs.end, value: basic };
+  var OCSPSigning = exports['id-kp-OCSPSigning'].join('.');
+  var certs = (basic.certs || []).filter(function(cert) {
+    return cert.tbsCertificate.extensions.some(function(ext) {
+      if (ext.extnID !== 'extendedKeyUsage')
+        return false;
+
+      return ext.extnValue.some(function(value) {
+        return value.join('.') === OCSPSigning;
+      });
+    });
+  });
+
+  return {
+    start: tbs.start,
+    end: tbs.end,
+    value: basic,
+    certs: certs,
+    certsTbs: certsTbs
+  };
 };
 
 exports.digest = {

diff --git a/lib/ocsp/verify.js b/lib/ocsp/verify.js
@@ -4,6 +4,35 @@ var ocsp = require('../ocsp');
 var rfc5280 = require('asn1.js-rfc5280');
 var crypto = require('crypto');
 
+// TODO(indutny): verify issuer, etc...
+function findResponder(issuer, certs, raws) {
+  var issuerKey = issuer.tbsCertificate.subjectPublicKeyInfo;
+  issuerKey = ocsp.utils.toPEM(
+      rfc5280.SubjectPublicKeyInfo.encode(issuerKey, 'der'), 'PUBLIC KEY');
+
+  for (var i = 0; i < certs.length; i++) {
+    var cert = certs[i];
+    var signAlg = ocsp.utils.sign[cert.signatureAlgorithm.algorithm.join('.')];
+    if (!signAlg) {
+      throw new Error('Unknown signature algorithm ' +
+                      cert.signatureAlgorithm.algorithm);
+    }
+
+    var verify = crypto.createVerify(signAlg);
+
+    verify.update(raws[i]);
+    if (!verify.verify(issuerKey, cert.signature.data))
+      throw new Error('Invalid signature');
+
+    var certKey = cert.tbsCertificate.subjectPublicKeyInfo;
+    certKey = ocsp.utils.toPEM(
+        rfc5280.SubjectPublicKeyInfo.encode(certKey, 'der'), 'PUBLIC KEY');
+    return certKey;
+  }
+
+  return issuerKey;
+}
+
 module.exports = function verify(options, cb) {
   var req = options.request;
   var issuer;
@@ -26,27 +55,29 @@ module.exports = function verify(options, cb) {
   }
 
   var rawTBS = options.response.slice(res.start, res.end);
+  var certs = res.certs;
+  var raws = res.certsTbs.map(function(tbs) {
+    return options.response.slice(tbs.start, tbs.end);
+  });
   res = res.value;
 
   // Verify signature using CAs Public Key
-  // TODO(indutny): support other responders
   var signAlg = ocsp.utils.sign[res.signatureAlgorithm.algorithm.join('.')];
   if (!signAlg) {
     done(new Error('Unknown signature algorithm ' +
                    res.signatureAlgorithm.algorithm));
     return;
   }
 
+  var responderKey = findResponder(issuer, certs, raws);
+
   var verify = crypto.createVerify(signAlg);
   var tbs = res.tbsResponseData;
 
-  var issuerKey = issuer.tbsCertificate.subjectPublicKeyInfo;
-  issuerKey = ocsp.utils.toPEM(
-      rfc5280.SubjectPublicKeyInfo.encode(issuerKey, 'der'), 'PUBLIC KEY');
   var signature = res.signature.data;
 
   verify.update(rawTBS);
-  if (!verify.verify(issuerKey, signature))
+  if (!verify.verify(responderKey, signature))
     return done(new Error('Invalid signature'));
 
   if (tbs.responses.length < 1)

diff --git a/test/agent-test.js b/test/agent-test.js
@@ -10,25 +10,25 @@ describe('OCSP Agent', function() {
     a = new ocsp.Agent();
   });
 
-  it('should connect and validate google.com', function(cb) {
-    var req = https.get({
-      host: 'www.google.com',
-      port: 443,
-      agent: a
-    }, function(res) {
-      res.resume();
-      cb();
-    });
-  });
+  var websites = [
+    'www.google.com',
+    'google.com',
+    'helloworld.letsencrypt.org',
+    'yahoo.com',
+    'nytimes.com',
+    'microsoft.com'
+  ];
 
-  it('should connect and validate letsencrypt.org', function(cb) {
-    var req = https.get({
-      host: 'helloworld.letsencrypt.org',
-      port: 443,
-      agent: a
-    }, function(res) {
-      res.resume();
-      cb();
+  websites.forEach(function(host) {
+    it('should connect and validate ' + host, function(cb) {
+      var req = https.get({
+        host: host,
+        port: 443,
+        agent: a
+      }, function(res) {
+        res.resume();
+        cb();
+      });
     });
   });
 });