src: add cve reverts and associated tests

Signed-off-by: Michael Dawson <mdawson@devrus.com>
Co-authored-by: Akshay K <iit.akshay@gmail.com>
Backport-PR-URL: nodejs-private/node-private#304
PR-URL: nodejs-private/node-private#300
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

Author: 2 people

lib/tls.js

@@ -60,6 +60,7 @@ const net = require('net');
 const { getOptionValue } = require('internal/options');
 const { getRootCertificates, getSSLCiphers } = internalBinding('crypto');
 const { Buffer } = require('buffer');
+const { URL } = require('internal/url');  // Only used for Security Revert
 const { canonicalizeIP } = internalBinding('cares_wrap');
 const _tls_common = require('_tls_common');
 const _tls_wrap = require('_tls_wrap');
@@ -274,6 +275,7 @@ exports.checkServerIdentity = function checkServerIdentity(hostname, cert) {
   const subject = cert.subject;
   const altNames = cert.subjectaltname;
   const dnsNames = [];
+  const uriNames = [];
   const ips = [];
 
   hostname = '' + hostname;
@@ -285,6 +287,12 @@ exports.checkServerIdentity = function checkServerIdentity(hostname, cert) {
     ArrayPrototypeForEach(splitAltNames, (name) => {
       if (StringPrototypeStartsWith(name, 'DNS:')) {
         ArrayPrototypePush(dnsNames, StringPrototypeSlice(name, 4));
+      } else if (process.REVERT_CVE_2021_44531 &&
+                 StringPrototypeStartsWith(name, 'URI:')) {
+        const uri = new URL(StringPrototypeSlice(name, 4));
+
+        // TODO(bnoordhuis) Also use scheme.
+        ArrayPrototypePush(uriNames, uri.hostname);
       } else if (StringPrototypeStartsWith(name, 'IP Address:')) {
         ArrayPrototypePush(ips, canonicalizeIP(StringPrototypeSlice(name, 11)));
       }
@@ -294,19 +302,27 @@ exports.checkServerIdentity = function checkServerIdentity(hostname, cert) {
   let valid = false;
   let reason = 'Unknown reason';
 
+  const hasAltNames =
+    dnsNames.length > 0 || ips.length > 0 || uriNames.length > 0;
+
   hostname = unfqdn(hostname);  // Remove trailing dot for error messages.
 
   if (net.isIP(hostname)) {
     valid = ArrayPrototypeIncludes(ips, canonicalizeIP(hostname));
     if (!valid)
       reason = `IP: ${hostname} is not in the cert's list: ` +
                ArrayPrototypeJoin(ips, ', ');
-  } else if (dnsNames.length > 0 || subject?.CN) {
+    // TODO(bnoordhuis) Also check URI SANs that are IP addresses.
+  } else if ((process.REVERT_CVE_2021_44531 && (hasAltNames || subject)) ||
+             (dnsNames.length > 0 || subject?.CN)) {
     const hostParts = splitHost(hostname);
     const wildcard = (pattern) => check(hostParts, pattern, true);
 
-    if (dnsNames.length > 0) {
-      valid = ArrayPrototypeSome(dnsNames, wildcard);
+    if ((process.REVERT_CVE_2021_44531 && hasAltNames) ||
+        (dnsNames.length > 0)) {
+      const noWildcard = (pattern) => check(hostParts, pattern, false);
+      valid = ArrayPrototypeSome(dnsNames, wildcard) ||
+              ArrayPrototypeSome(uriNames, noWildcard);
       if (!valid)
         reason =
           `Host: ${hostname}. is not in the cert's altnames: ${altNames}`;

src/crypto/crypto_common.cc

@@ -6,6 +6,7 @@
 #include "crypto/crypto_common.h"
 #include "node.h"
 #include "node_internals.h"
+#include "node_revert.h"
 #include "node_url.h"
 #include "string_bytes.h"
 #include "memory_tracker-inl.h"
@@ -620,6 +621,44 @@ MaybeLocal<Value> GetValidFrom(
   return ToV8Value(env, bio);
 }
 
+// deprecated, only used for security revert
+bool SafeX509ExtPrint(const BIOPointer& out, X509_EXTENSION* ext) {
+  const X509V3_EXT_METHOD* method = X509V3_EXT_get(ext);
+
+  if (method != X509V3_EXT_get_nid(NID_subject_alt_name))
+    return false;
+
+  GENERAL_NAMES* names = static_cast<GENERAL_NAMES*>(X509V3_EXT_d2i(ext));
+  if (names == nullptr)
+    return false;
+
+  for (int i = 0; i < sk_GENERAL_NAME_num(names); i++) {
+    GENERAL_NAME* gen = sk_GENERAL_NAME_value(names, i);
+
+    if (i != 0)
+      BIO_write(out.get(), ", ", 2);
+
+    if (gen->type == GEN_DNS) {
+      ASN1_IA5STRING* name = gen->d.dNSName;
+
+      BIO_write(out.get(), "DNS:", 4);
+      BIO_write(out.get(), name->data, name->length);
+    } else {
+      STACK_OF(CONF_VALUE)* nval = i2v_GENERAL_NAME(
+          const_cast<X509V3_EXT_METHOD*>(method), gen, nullptr);
+      if (nval == nullptr) {
+        sk_GENERAL_NAME_pop_free(names, GENERAL_NAME_free);
+        return false;
+      }
+      X509V3_EXT_val_prn(out.get(), nval, 0, 0);
+      sk_CONF_VALUE_pop_free(nval, X509V3_conf_free);
+    }
+  }
+  sk_GENERAL_NAME_pop_free(names, GENERAL_NAME_free);
+
+  return true;
+}
+
 static inline bool IsSafeAltName(const char* name, size_t length, bool utf8) {
   for (size_t i = 0; i < length; i++) {
     char c = name[i];
@@ -844,6 +883,10 @@ bool SafeX509SubjectAltNamePrint(const BIOPointer& out, X509_EXTENSION* ext) {
   const X509V3_EXT_METHOD* method = X509V3_EXT_get(ext);
   CHECK(method == X509V3_EXT_get_nid(NID_subject_alt_name));
 
+  if (IsReverted(SECURITY_REVERT_CVE_2021_44532)) {
+    return  SafeX509ExtPrint(out, ext);
+  }
+
   GENERAL_NAMES* names = static_cast<GENERAL_NAMES*>(X509V3_EXT_d2i(ext));
   if (names == nullptr)
     return false;
@@ -869,6 +912,10 @@ bool SafeX509InfoAccessPrint(const BIOPointer& out, X509_EXTENSION* ext) {
   const X509V3_EXT_METHOD* method = X509V3_EXT_get(ext);
   CHECK(method == X509V3_EXT_get_nid(NID_info_access));
 
+  if (IsReverted(SECURITY_REVERT_CVE_2021_44532)) {
+    return (X509V3_EXT_print(out.get(), ext, 0, 0) == 1);
+  }
+
   AUTHORITY_INFO_ACCESS* descs =
       static_cast<AUTHORITY_INFO_ACCESS*>(X509V3_EXT_d2i(ext));
   if (descs == nullptr)

src/node_revert.h

@@ -16,6 +16,8 @@
 namespace node {
 
 #define SECURITY_REVERSIONS(XX)                                            \
+  XX(CVE_2021_44531, "CVE-2021-44531", "Cert Verif Bypass via URI SAN")    \
+  XX(CVE_2021_44532, "CVE-2021-44532", "Cert Verif Bypass via Str Inject") \
 //  XX(CVE_2016_PEND, "CVE-2016-PEND", "Vulnerability Title")
 
 enum reversion {

test/parallel/test-revert-CVE-2021-44531.js

@@ -0,0 +1,50 @@
+// Flags: --security-revert=CVE-2021-44531
+'use strict';
+const common = require('../common');
+
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+
+const assert = require('assert');
+const util = require('util');
+
+const tls = require('tls');
+
+const tests = [
+  // Likewise for "URI:" Subject Alternative Names.
+  // See also https://github.com/nodejs/node/issues/8108.
+  {
+    host: '8.8.8.8',
+    cert: { subject: { CN: '8.8.8.8' }, subjectaltname: 'URI:http://8.8.8.8/' },
+    error: 'IP: 8.8.8.8 is not in the cert\'s list: '
+  },
+  // Empty Subject w/URI name
+  {
+    host: 'a.b.a.com', cert: {
+      subjectaltname: 'URI:http://a.b.a.com/',
+    }
+  },
+  // URI names
+  {
+    host: 'a.b.a.com', cert: {
+      subjectaltname: 'URI:http://a.b.a.com/',
+      subject: {}
+    }
+  },
+  {
+    host: 'a.b.a.com', cert: {
+      subjectaltname: 'URI:http://*.b.a.com/',
+      subject: {}
+    },
+    error: 'Host: a.b.a.com. is not in the cert\'s altnames: ' +
+           'URI:http://*.b.a.com/'
+  },
+];
+
+tests.forEach(function(test, i) {
+  const err = tls.checkServerIdentity(test.host, test.cert);
+  assert.strictEqual(err && err.reason,
+                     test.error,
+                     `Test# ${i} failed: ${util.inspect(test)} \n` +
+                     `${test.error} != ${(err && err.reason)}`);
+});

test/parallel/test-tls-0-dns-altname-revert-CVE-2021-44532.js

@@ -0,0 +1,54 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+// Flags: --security-revert=CVE-2021-44532
+'use strict';
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+
+// Check getPeerCertificate can properly handle '\0' for fix CVE-2009-2408.
+
+const assert = require('assert');
+const tls = require('tls');
+const fixtures = require('../common/fixtures');
+
+const server = tls.createServer({
+  key: fixtures.readSync(['0-dns', '0-dns-key.pem']),
+  cert: fixtures.readSync(['0-dns', '0-dns-cert.pem'])
+}, common.mustCall((c) => {
+  c.once('data', common.mustCall(() => {
+    c.destroy();
+    server.close();
+  }));
+})).listen(0, common.mustCall(() => {
+  const c = tls.connect(server.address().port, {
+    rejectUnauthorized: false
+  }, common.mustCall(() => {
+    const cert = c.getPeerCertificate();
+    assert.strictEqual(cert.subjectaltname,
+                       'DNS:good.example.org\0.evil.example.com, ' +
+                           'DNS:just-another.example.com, ' +
+                           'IP Address:8.8.8.8, ' +
+                           'IP Address:8.8.4.4, ' +
+                           'DNS:last.example.com');
+    c.write('ok');
+  }));
+}));

test/parallel/test-x509-escaping-revert-CVE-2021-44532.js

@@ -0,0 +1,343 @@
+// Flags: --security-revert=CVE-2021-44532
+'use strict';
+
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+
+const assert = require('assert');
+const { X509Certificate } = require('crypto');
+const tls = require('tls');
+const fixtures = require('../common/fixtures');
+
+const { hasOpenSSL3 } = common;
+
+// Test escaping rules for subject alternative names.
+{
+  const expectedSANs = [
+    'DNS:good.example.com, DNS:evil.example.com',
+    // URIs should not require escaping.
+    'URI:http://example.com/',
+    'URI:http://example.com/?a=b&c=d',
+    // Unless they contain commas.
+    'URI:http://example.com/a,b',
+    // Percent encoding should not require escaping.
+    'URI:http://example.com/a%2Cb',
+    // Malicious attempts should be escaped.
+    'URI:http://example.com/a, DNS:good.example.com',
+    // Non-ASCII characters in DNS names should be treated as Latin-1.
+    'DNS:ex�mple.com',
+    // It should not be possible to cause unescaping without escaping.
+    'DNS:"evil.example.com"',
+    // IPv4 addresses should be represented as usual.
+    'IP Address:8.8.8.8',
+    'IP Address:8.8.4.4',
+    // For backward-compatibility, include invalid IP address lengths.
+    hasOpenSSL3 ? 'IP Address:<invalid length=5>' : 'IP Address:<invalid>',
+    hasOpenSSL3 ? 'IP Address:<invalid length=6>' : 'IP Address:<invalid>',
+    // IPv6 addresses are represented as OpenSSL does.
+    'IP Address:A0B:C0D:E0F:0:0:0:7A7B:7C7D',
+    // Regular email addresses don't require escaping.
+    'email:foo@example.com',
+    // ... but should be escaped if they contain commas.
+    'email:foo@example.com, DNS:good.example.com',
+    'DirName:/C=DE/L=Hannover',
+    // TODO(tniessen): support UTF8 in DirName
+    'DirName:/C=DE/L=M\\xC3\\xBCnchen',
+    'DirName:/C=DE/L=Berlin, DNS:good.example.com',
+    'DirName:/C=DE/L=Berlin, DNS:good.example.com\\x00' +
+      'evil.example.com',
+    'DirName:/C=DE/L=Berlin, DNS:good.example.com\\\\x00' +
+      'evil.example.com',
+    // These next two tests might be surprising. OpenSSL applies its own rules
+    // first, which introduce backslashes, which activate node's escaping.
+    // Unfortunately, there are also differences between OpenSSL 1.1.1 and 3.0.
+    'DirName:/C=DE/L=Berlin\\x0D\\x0A',
+    hasOpenSSL3 ?
+      'DirName:/C=DE/L=Berlin\\/CN=good.example.com' :
+      'DirName:/C=DE/L=Berlin/CN=good.example.com',
+    // TODO(tniessen): even OIDs that are well-known (such as the following,
+    // which is sha256WithRSAEncryption) should be represented numerically only.
+    'Registered ID:sha256WithRSAEncryption',
+    // This is an OID that will likely never be assigned to anything, thus
+    // OpenSSL hould not know it.
+    'Registered ID:1.3.9999.12.34',
+    hasOpenSSL3 ?
+      'othername: XmppAddr::abc123' :
+      'othername:<unsupported>',
+    hasOpenSSL3 ?
+      'othername: XmppAddr::abc123, DNS:good.example.com' :
+      'othername:<unsupported>',
+    hasOpenSSL3 ?
+      null :
+      'othername:<unsupported>',
+    // This is unsupported because the OID is not recognized.
+    hasOpenSSL3 ?
+      'othername: 1.3.9999.12.34::abc123' :
+      'othername:<unsupported>',
+    hasOpenSSL3 ? 'othername: SRVName::abc123' : 'othername:<unsupported>',
+    // This is unsupported because it is an SRVName with a UTF8String value,
+    // which is not allowed for SRVName.
+    hasOpenSSL3 ?
+      null : 'othername:<unsupported>',
+    hasOpenSSL3 ?
+      null :
+      'othername:<unsupported>',
+  ];
+
+  const serverKey = fixtures.readSync('x509-escaping/server-key.pem', 'utf8');
+
+  for (let i = 0; i < expectedSANs.length; i++) {
+    const pem = fixtures.readSync(`x509-escaping/alt-${i}-cert.pem`, 'utf8');
+
+    // Test the subjectAltName property of the X509Certificate API.
+    const cert = new X509Certificate(pem);
+    assert.strictEqual(cert.subjectAltName, expectedSANs[i]);
+
+    // Test that the certificate obtained by checkServerIdentity has the correct
+    // subjectaltname property.
+    const server = tls.createServer({
+      key: serverKey,
+      cert: pem,
+    }, common.mustCall((conn) => {
+      conn.destroy();
+      server.close();
+    })).listen(common.mustCall(() => {
+      const { port } = server.address();
+      tls.connect(port, {
+        ca: pem,
+        servername: 'example.com',
+        checkServerIdentity: (hostname, peerCert) => {
+          assert.strictEqual(hostname, 'example.com');
+          assert.strictEqual(peerCert.subjectaltname, expectedSANs[i]);
+        },
+      }, common.mustCall());
+    }));
+  }
+}
+
+// Test escaping rules for authority info access.
+{
+  const expectedInfoAccess = [
+    {
+      text: 'OCSP - URI:http://good.example.com/\n' +
+            'OCSP - URI:http://evil.example.com/',
+      legacy: {
+        'OCSP - URI': [
+          'http://good.example.com/',
+          'http://evil.example.com/',
+        ],
+      },
+    },
+    {
+      text: 'CA Issuers - URI:http://ca.example.com/\n' +
+            'OCSP - URI:http://evil.example.com\n' +
+            'OCSP - DNS:good.example.com\n' +
+            'OCSP - URI:http://ca.nodejs.org/ca.cert',
+      legacy: {
+        'CA Issuers - URI': [
+          'http://ca.example.com/',
+        ],
+        'OCSP - DNS': [
+          'good.example.com',
+        ],
+        'OCSP - URI': [
+          'http://evil.example.com',
+          'http://ca.nodejs.org/ca.cert',
+        ],
+      },
+    },
+    {
+      text: '1.3.9999.12.34 - URI:http://ca.example.com/',
+      legacy: {
+        '1.3.9999.12.34 - URI': [
+          'http://ca.example.com/',
+        ],
+      },
+    },
+    hasOpenSSL3 ? {
+      text: 'OCSP - othername: XmppAddr::good.example.com\n' +
+            'OCSP - othername: 1.3.9999.12.34::abc123\n' +
+            'OCSP - othername: SRVName::abc123',
+      legacy: {
+        'OCSP - othername': [
+          ' XmppAddr::good.example.com',
+          ' 1.3.9999.12.34::abc123',
+          ' SRVName::abc123',
+        ],
+      },
+    } : {
+      text: 'OCSP - othername:<unsupported>\n' +
+            'OCSP - othername:<unsupported>\n' +
+            'OCSP - othername:<unsupported>',
+      legacy: {
+        'OCSP - othername': [
+          '<unsupported>',
+          '<unsupported>',
+          '<unsupported>',
+        ],
+      },
+    },
+    hasOpenSSL3 ? {
+      text: null,
+      legacy: null,
+    } : {
+      text: 'OCSP - othername:<unsupported>',
+      legacy: {
+        'OCSP - othername': [
+          '<unsupported>',
+        ]
+      },
+    },
+  ];
+
+  const serverKey = fixtures.readSync('x509-escaping/server-key.pem', 'utf8');
+
+  for (let i = 0; i < expectedInfoAccess.length; i++) {
+    const pem = fixtures.readSync(`x509-escaping/info-${i}-cert.pem`, 'utf8');
+    const expected = expectedInfoAccess[i];
+
+    // Test the subjectAltName property of the X509Certificate API.
+    const cert = new X509Certificate(pem);
+    assert.strictEqual(cert.infoAccess, expected.text ?
+      `${expected.text}${hasOpenSSL3 ? '' : '\n'}` :
+      expected.text);
+
+    // Test that the certificate obtained by checkServerIdentity has the correct
+    // subjectaltname property.
+    const server = tls.createServer({
+      key: serverKey,
+      cert: pem,
+    }, common.mustCall((conn) => {
+      conn.destroy();
+      server.close();
+    })).listen(common.mustCall(() => {
+      const { port } = server.address();
+      tls.connect(port, {
+        ca: pem,
+        servername: 'example.com',
+        checkServerIdentity: (hostname, peerCert) => {
+          assert.strictEqual(hostname, 'example.com');
+          assert.deepStrictEqual(peerCert.infoAccess,
+                                 expected.legacy ?
+                                   Object.assign(Object.create(null),
+                                                 expected.legacy) :
+                                   expected.legacy);
+        },
+      }, common.mustCall());
+    }));
+  }
+}
+
+// The internal parsing logic must match the JSON specification exactly.
+{
+  // This list is partially based on V8's own JSON tests.
+  const invalidJSON = [
+    '"\\a invalid escape"',
+    '"\\v invalid escape"',
+    '"\\\' invalid escape"',
+    '"\\x42 invalid escape"',
+    '"\\u202 invalid escape"',
+    '"\\012 invalid escape"',
+    '"Unterminated string',
+    '"Unterminated string\\"',
+    '"Unterminated string\\\\\\"',
+    '"\u0000 control character"',
+    '"\u001e control character"',
+    '"\u001f control character"',
+  ];
+
+  for (const invalidStringLiteral of invalidJSON) {
+    // Usually, checkServerIdentity returns an error upon verification failure.
+    // In this case, however, it should throw an error since this is not a
+    // verification error. Node.js itself will never produce invalid JSON string
+    // literals, so this can only happen when users construct invalid subject
+    // alternative name strings (that do not follow escaping rules).
+    assert.throws(() => {
+      tls.checkServerIdentity('example.com', {
+        subjectaltname: `DNS:${invalidStringLiteral}`,
+      });
+    }, {
+      code: 'ERR_TLS_CERT_ALTNAME_FORMAT',
+      message: 'Invalid subject alternative name string'
+    });
+  }
+}
+
+// While node does not produce commas within SAN entries, it should parse them
+// correctly (i.e., not simply split at commas).
+{
+  // Regardless of the quotes, splitting this SAN string at commas would
+  // cause checkServerIdentity to see 'DNS:b.example.com' and thus to accept
+  // the certificate for b.example.com.
+  const san = 'DNS:"a.example.com, DNS:b.example.com, DNS:c.example.com"';
+
+  // This is what node used to do, and which is not correct!
+  const hostname = 'b.example.com';
+  assert.strictEqual(san.split(', ')[1], `DNS:${hostname}`);
+
+  // The new implementation should parse the string correctly.
+  const err = tls.checkServerIdentity(hostname, { subjectaltname: san });
+  assert(err);
+  assert.strictEqual(err.code, 'ERR_TLS_CERT_ALTNAME_INVALID');
+  assert.strictEqual(err.message, 'Hostname/IP does not match certificate\'s ' +
+                                  'altnames: Host: b.example.com. is not in ' +
+                                  'the cert\'s altnames: DNS:"a.example.com, ' +
+                                  'DNS:b.example.com, DNS:c.example.com"');
+}
+
+// The subject MUST be ignored if a dNSName subject alternative name exists.
+{
+  const key = fixtures.readKey('incorrect_san_correct_subject-key.pem');
+  const cert = fixtures.readKey('incorrect_san_correct_subject-cert.pem');
+
+  // The hostname is the CN, but not a SAN entry.
+  const servername = 'good.example.com';
+  const certX509 = new X509Certificate(cert);
+  assert.strictEqual(certX509.subject, `CN=${servername}`);
+  assert.strictEqual(certX509.subjectAltName, 'DNS:evil.example.com');
+
+  // Try connecting to a server that uses the self-signed certificate.
+  const server = tls.createServer({ key, cert }, common.mustNotCall());
+  server.listen(common.mustCall(() => {
+    const { port } = server.address();
+    const socket = tls.connect(port, {
+      ca: cert,
+      servername,
+    }, common.mustNotCall());
+    socket.on('error', common.mustCall((err) => {
+      assert.strictEqual(err.code, 'ERR_TLS_CERT_ALTNAME_INVALID');
+      assert.strictEqual(err.message, 'Hostname/IP does not match ' +
+                                      "certificate's altnames: Host: " +
+                                      "good.example.com. is not in the cert's" +
+                                      ' altnames: DNS:evil.example.com');
+    }));
+  })).unref();
+}
+
+// The subject MUST NOT be ignored if no dNSName subject alternative name
+// exists, even if other subject alternative names exist.
+{
+  const key = fixtures.readKey('irrelevant_san_correct_subject-key.pem');
+  const cert = fixtures.readKey('irrelevant_san_correct_subject-cert.pem');
+
+  // The hostname is the CN, but there is no dNSName SAN entry.
+  const servername = 'good.example.com';
+  const certX509 = new X509Certificate(cert);
+  assert.strictEqual(certX509.subject, `CN=${servername}`);
+  assert.strictEqual(certX509.subjectAltName, 'IP Address:1.2.3.4');
+
+  // Connect to a server that uses the self-signed certificate.
+  const server = tls.createServer({ key, cert }, common.mustCall((socket) => {
+    socket.destroy();
+    server.close();
+  })).listen(common.mustCall(() => {
+    const { port } = server.address();
+    tls.connect(port, {
+      ca: cert,
+      servername,
+    }, common.mustCall(() => {
+      // Do nothing, the server will close the connection.
+    }));
+  }));
+}