From e52882da4ca99bd9c4f63890224327632f8bda42 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tobias=20Nie=C3=9Fen?= <tniessen@tnie.de>
Date: Tue, 7 Dec 2021 00:21:28 +0000
Subject: [PATCH] crypto,tls: implement safe x509 GeneralName format

This change introduces JSON-compatible escaping rules for strings that
include X.509 GeneralName components (see RFC 5280). This non-standard
format avoids ambiguities and prevents injection attacks that could
previously lead to X.509 certificates being accepted even though they
were not valid for the target hostname.

These changes affect the format of subject alternative names and the
format of authority information access. The checkServerIdentity function
has been modified to safely handle the new format, eliminating the
possibility of injecting subject alternative names into the verification
logic.

Because each subject alternative name is only encoded as a JSON string
literal if necessary for security purposes, this change will only be
visible in rare cases.

This addresses CVE-2021-44532.

Co-authored-by: Akshay K <iit.akshay@gmail.com>
CVE-ID: CVE-2021-44532
Backport-PR-URL: https://github.com/nodejs-private/node-private/pull/304
PR-URL: https://github.com/nodejs-private/node-private/pull/300
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
---
 doc/api/crypto.md                             |  39 +-
 doc/api/errors.md                             |   9 +
 lib/_tls_common.js                            |   9 +
 lib/internal/errors.js                        |   2 +
 lib/tls.js                                    |  48 +-
 src/crypto/crypto_common.cc                   | 319 ++++++++++-
 src/crypto/crypto_common.h                    |  25 +-
 src/crypto/crypto_x509.cc                     |   4 +-
 test/fixtures/keys/Makefile                   |  14 +
 .../incorrect_san_correct_subject-cert.pem    |  11 +
 .../incorrect_san_correct_subject-key.pem     |   5 +
 test/fixtures/x509-escaping/.gitignore        |   2 +
 test/fixtures/x509-escaping/alt-0-cert.pem    |  29 +
 test/fixtures/x509-escaping/alt-1-cert.pem    |  28 +
 test/fixtures/x509-escaping/alt-10-cert.pem   |  28 +
 test/fixtures/x509-escaping/alt-11-cert.pem   |  28 +
 test/fixtures/x509-escaping/alt-12-cert.pem   |  28 +
 test/fixtures/x509-escaping/alt-13-cert.pem   |  28 +
 test/fixtures/x509-escaping/alt-14-cert.pem   |  29 +
 test/fixtures/x509-escaping/alt-15-cert.pem   |  29 +
 test/fixtures/x509-escaping/alt-16-cert.pem   |  29 +
 test/fixtures/x509-escaping/alt-17-cert.pem   |  29 +
 test/fixtures/x509-escaping/alt-18-cert.pem   |  29 +
 test/fixtures/x509-escaping/alt-19-cert.pem   |  29 +
 test/fixtures/x509-escaping/alt-2-cert.pem    |  28 +
 test/fixtures/x509-escaping/alt-20-cert.pem   |  29 +
 test/fixtures/x509-escaping/alt-21-cert.pem   |  29 +
 test/fixtures/x509-escaping/alt-22-cert.pem   |  28 +
 test/fixtures/x509-escaping/alt-23-cert.pem   |  28 +
 test/fixtures/x509-escaping/alt-24-cert.pem   |  28 +
 test/fixtures/x509-escaping/alt-25-cert.pem   |  29 +
 test/fixtures/x509-escaping/alt-26-cert.pem   |  29 +
 test/fixtures/x509-escaping/alt-27-cert.pem   |  28 +
 test/fixtures/x509-escaping/alt-28-cert.pem   |  28 +
 test/fixtures/x509-escaping/alt-29-cert.pem   |  28 +
 test/fixtures/x509-escaping/alt-3-cert.pem    |  28 +
 test/fixtures/x509-escaping/alt-30-cert.pem   |  28 +
 test/fixtures/x509-escaping/alt-4-cert.pem    |  28 +
 test/fixtures/x509-escaping/alt-5-cert.pem    |  29 +
 test/fixtures/x509-escaping/alt-6-cert.pem    |  28 +
 test/fixtures/x509-escaping/alt-7-cert.pem    |  28 +
 test/fixtures/x509-escaping/alt-8-cert.pem    |  28 +
 test/fixtures/x509-escaping/alt-9-cert.pem    |  28 +
 test/fixtures/x509-escaping/create-certs.js   | 502 ++++++++++++++++++
 .../x509-escaping/google/intermediate.pem     |  11 +
 test/fixtures/x509-escaping/google/key.pem    |   5 +
 test/fixtures/x509-escaping/google/leaf0.pem  |  10 +
 test/fixtures/x509-escaping/google/leaf1.pem  |  10 +
 test/fixtures/x509-escaping/google/leaf2.pem  |  10 +
 test/fixtures/x509-escaping/google/leaf3.pem  |  10 +
 test/fixtures/x509-escaping/google/leaf4.pem  |  10 +
 test/fixtures/x509-escaping/google/root.pem   |   9 +
 test/fixtures/x509-escaping/info-0-cert.pem   |  30 ++
 test/fixtures/x509-escaping/info-1-cert.pem   |  31 ++
 test/fixtures/x509-escaping/info-2-cert.pem   |  29 +
 test/fixtures/x509-escaping/info-3-cert.pem   |  30 ++
 test/fixtures/x509-escaping/info-4-cert.pem   |  29 +
 test/fixtures/x509-escaping/package.json      |  12 +
 test/fixtures/x509-escaping/server-key.pem    |  52 ++
 test/parallel/test-tls-0-dns-altname.js       |   2 +-
 test/parallel/test-x509-escaping.js           | 338 ++++++++++++
 61 files changed, 2455 insertions(+), 42 deletions(-)
 create mode 100644 test/fixtures/keys/incorrect_san_correct_subject-cert.pem
 create mode 100644 test/fixtures/keys/incorrect_san_correct_subject-key.pem
 create mode 100644 test/fixtures/x509-escaping/.gitignore
 create mode 100644 test/fixtures/x509-escaping/alt-0-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-1-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-10-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-11-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-12-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-13-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-14-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-15-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-16-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-17-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-18-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-19-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-2-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-20-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-21-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-22-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-23-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-24-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-25-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-26-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-27-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-28-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-29-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-3-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-30-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-4-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-5-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-6-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-7-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-8-cert.pem
 create mode 100644 test/fixtures/x509-escaping/alt-9-cert.pem
 create mode 100644 test/fixtures/x509-escaping/create-certs.js
 create mode 100644 test/fixtures/x509-escaping/google/intermediate.pem
 create mode 100644 test/fixtures/x509-escaping/google/key.pem
 create mode 100644 test/fixtures/x509-escaping/google/leaf0.pem
 create mode 100644 test/fixtures/x509-escaping/google/leaf1.pem
 create mode 100644 test/fixtures/x509-escaping/google/leaf2.pem
 create mode 100644 test/fixtures/x509-escaping/google/leaf3.pem
 create mode 100644 test/fixtures/x509-escaping/google/leaf4.pem
 create mode 100644 test/fixtures/x509-escaping/google/root.pem
 create mode 100644 test/fixtures/x509-escaping/info-0-cert.pem
 create mode 100644 test/fixtures/x509-escaping/info-1-cert.pem
 create mode 100644 test/fixtures/x509-escaping/info-2-cert.pem
 create mode 100644 test/fixtures/x509-escaping/info-3-cert.pem
 create mode 100644 test/fixtures/x509-escaping/info-4-cert.pem
 create mode 100644 test/fixtures/x509-escaping/package.json
 create mode 100644 test/fixtures/x509-escaping/server-key.pem
 create mode 100644 test/parallel/test-x509-escaping.js

diff --git a/doc/api/crypto.md b/doc/api/crypto.md
index 669eb4373d65d2..b4a48988966273 100644
--- a/doc/api/crypto.md
+++ b/doc/api/crypto.md
@@ -2565,11 +2565,27 @@ The SHA-256 fingerprint of this certificate.
 
 <!-- YAML
 added: v15.6.0
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs-private/node-private/pull/300
+    description: Parts of this string may be encoded as JSON string literals
+                 in response to CVE-2021-44532.
 -->
 
 * Type: {string}
 
-The information access content of this certificate.
+A textual representation of the certificate's authority information access
+extension.
+
+This is a line feed separated list of access descriptions. Each line begins with
+the access method and the kind of the access location, followed by a colon and
+the value associated with the access location.
+
+After the prefix denoting the access method and the kind of the access location,
+the remainder of each line might be enclosed in quotes to indicate that the
+value is a JSON string literal. For backward compatibility, Node.js only uses
+JSON string literals within this property when necessary to avoid ambiguity.
+Third-party code should be prepared to handle both possible entry formats.
 
 ### `x509.issuer`
 
@@ -2646,12 +2662,32 @@ The complete subject of this certificate.
 
 <!-- YAML
 added: v15.6.0
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs-private/node-private/pull/300
+    description: Parts of this string may be encoded as JSON string literals
+                 in response to CVE-2021-44532.
 -->
 
 * Type: {string}
 
 The subject alternative name specified for this certificate.
 
+This is a comma-separated list of subject alternative names. Each entry begins
+with a string identifying the kind of the subject alternative name followed by
+a colon and the value associated with the entry.
+
+Earlier versions of Node.js incorrectly assumed that it is safe to split this
+property at the two-character sequence `', '` (see [CVE-2021-44532][]). However,
+both malicious and legitimate certificates can contain subject alternative names
+that include this sequence when represented as a string.
+
+After the prefix denoting the type of the entry, the remainder of each entry
+might be enclosed in quotes to indicate that the value is a JSON string literal.
+For backward compatibility, Node.js only uses JSON string literals within this
+property when necessary to avoid ambiguity. Third-party code should be prepared
+to handle both possible entry formats.
+
 ### `x509.toJSON()`
 
 <!-- YAML
@@ -5838,6 +5874,7 @@ See the [list of SSL OP Flags][] for details.
 
 [AEAD algorithms]: https://en.wikipedia.org/wiki/Authenticated_encryption
 [CCM mode]: #ccm-mode
+[CVE-2021-44532]: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-44532
 [Caveats]: #support-for-weak-or-compromised-algorithms
 [Crypto constants]: #crypto-constants
 [HTML 5.2]: https://www.w3.org/TR/html52/changes.html#features-removed
diff --git a/doc/api/errors.md b/doc/api/errors.md
index c667d5e6ec30dd..2369e6eda72082 100644
--- a/doc/api/errors.md
+++ b/doc/api/errors.md
@@ -2505,6 +2505,15 @@ An unspecified or non-specific system error has occurred within the Node.js
 process. The error object will have an `err.info` object property with
 additional details.
 
+<a id="ERR_TLS_CERT_ALTNAME_FORMAT"></a>
+
+### `ERR_TLS_CERT_ALTNAME_FORMAT`
+
+This error is thrown by `checkServerIdentity` if a user-supplied
+`subjectaltname` property violates encoding rules. Certificate objects produced
+by Node.js itself always comply with encoding rules and will never cause
+this error.
+
 <a id="ERR_TLS_CERT_ALTNAME_INVALID"></a>
 
 ### `ERR_TLS_CERT_ALTNAME_INVALID`
diff --git a/lib/_tls_common.js b/lib/_tls_common.js
index 21b22a42507c5b..cb3f08bf28793e 100644
--- a/lib/_tls_common.js
+++ b/lib/_tls_common.js
@@ -25,6 +25,7 @@ const tls = require('tls');
 
 const {
   ArrayPrototypePush,
+  JSONParse,
   ObjectCreate,
   StringPrototypeReplace,
 } = primordials;
@@ -137,6 +138,14 @@ function translatePeerCertificate(c) {
     // XXX: More key validation?
     StringPrototypeReplace(info, /([^\n:]*):([^\n]*)(?:\n|$)/g,
                            (all, key, val) => {
+                             if (val.charCodeAt(0) === 0x22) {
+                               // The translatePeerCertificate function is only
+                               // used on internally created legacy certificate
+                               // objects, and any value that contains a quote
+                               // will always be a valid JSON string literal,
+                               // so this should never throw.
+                               val = JSONParse(val);
+                             }
                              if (key in c.infoAccess)
                                ArrayPrototypePush(c.infoAccess[key], val);
                              else
diff --git a/lib/internal/errors.js b/lib/internal/errors.js
index 07b7181a588f30..c510bd321512a0 100644
--- a/lib/internal/errors.js
+++ b/lib/internal/errors.js
@@ -1516,6 +1516,8 @@ E('ERR_STREAM_WRAP', 'Stream has StringDecoder set or is in objectMode', Error);
 E('ERR_STREAM_WRITE_AFTER_END', 'write after end', Error);
 E('ERR_SYNTHETIC', 'JavaScript Callstack', Error);
 E('ERR_SYSTEM_ERROR', 'A system error occurred', SystemError);
+E('ERR_TLS_CERT_ALTNAME_FORMAT', 'Invalid subject alternative name string',
+  SyntaxError);
 E('ERR_TLS_CERT_ALTNAME_INVALID', function(reason, host, cert) {
   this.reason = reason;
   this.host = host;
diff --git a/lib/tls.js b/lib/tls.js
index 683736460b1ef7..eaba340d572090 100644
--- a/lib/tls.js
+++ b/lib/tls.js
@@ -30,20 +30,25 @@ const {
   ArrayPrototypePush,
   ArrayPrototypeReduce,
   ArrayPrototypeSome,
+  JSONParse,
   ObjectDefineProperty,
   ObjectFreeze,
+  RegExpPrototypeExec,
   RegExpPrototypeTest,
   StringFromCharCode,
   StringPrototypeCharCodeAt,
   StringPrototypeEndsWith,
   StringPrototypeIncludes,
+  StringPrototypeIndexOf,
   StringPrototypeReplace,
   StringPrototypeSlice,
   StringPrototypeSplit,
   StringPrototypeStartsWith,
+  StringPrototypeSubstring,
 } = primordials;
 
 const {
+  ERR_TLS_CERT_ALTNAME_FORMAT,
   ERR_TLS_CERT_ALTNAME_INVALID,
   ERR_OUT_OF_RANGE
 } = require('internal/errors').codes;
@@ -227,6 +232,45 @@ function check(hostParts, pattern, wildcards) {
   return true;
 }
 
+// This pattern is used to determine the length of escaped sequences within
+// the subject alt names string. It allows any valid JSON string literal.
+// This MUST match the JSON specification (ECMA-404 / RFC8259) exactly.
+const jsonStringPattern =
+  // eslint-disable-next-line no-control-regex
+  /^"(?:[^"\\\u0000-\u001f]|\\(?:["\\/bfnrt]|u[0-9a-fA-F]{4}))*"/;
+
+function splitEscapedAltNames(altNames) {
+  const result = [];
+  let currentToken = '';
+  let offset = 0;
+  while (offset !== altNames.length) {
+    const nextSep = StringPrototypeIndexOf(altNames, ', ', offset);
+    const nextQuote = StringPrototypeIndexOf(altNames, '"', offset);
+    if (nextQuote !== -1 && (nextSep === -1 || nextQuote < nextSep)) {
+      // There is a quote character and there is no separator before the quote.
+      currentToken += StringPrototypeSubstring(altNames, offset, nextQuote);
+      const match = RegExpPrototypeExec(
+        jsonStringPattern, StringPrototypeSubstring(altNames, nextQuote));
+      if (!match) {
+        throw new ERR_TLS_CERT_ALTNAME_FORMAT();
+      }
+      currentToken += JSONParse(match[0]);
+      offset = nextQuote + match[0].length;
+    } else if (nextSep !== -1) {
+      // There is a separator and no quote before it.
+      currentToken += StringPrototypeSubstring(altNames, offset, nextSep);
+      ArrayPrototypePush(result, currentToken);
+      currentToken = '';
+      offset = nextSep + 2;
+    } else {
+      currentToken += StringPrototypeSubstring(altNames, offset);
+      offset = altNames.length;
+    }
+  }
+  ArrayPrototypePush(result, currentToken);
+  return result;
+}
+
 exports.checkServerIdentity = function checkServerIdentity(hostname, cert) {
   const subject = cert.subject;
   const altNames = cert.subjectaltname;
@@ -237,7 +281,9 @@ exports.checkServerIdentity = function checkServerIdentity(hostname, cert) {
   hostname = '' + hostname;
 
   if (altNames) {
-    const splitAltNames = StringPrototypeSplit(altNames, ', ');
+    const splitAltNames = StringPrototypeIncludes(altNames, '"') ?
+      splitEscapedAltNames(altNames) :
+      StringPrototypeSplit(altNames, ', ');
     ArrayPrototypeForEach(splitAltNames, (name) => {
       if (StringPrototypeStartsWith(name, 'DNS:')) {
         ArrayPrototypePush(dnsNames, StringPrototypeSlice(name, 4));
diff --git a/src/crypto/crypto_common.cc b/src/crypto/crypto_common.cc
index c7b0691108a1a4..b8e705bf76ec66 100644
--- a/src/crypto/crypto_common.cc
+++ b/src/crypto/crypto_common.cc
@@ -619,39 +619,320 @@ MaybeLocal<Value> GetValidFrom(
   return ToV8Value(env, bio);
 }
 
-bool SafeX509ExtPrint(const BIOPointer& out, X509_EXTENSION* ext) {
-  const X509V3_EXT_METHOD* method = X509V3_EXT_get(ext);
+static inline bool IsSafeAltName(const char* name, size_t length, bool utf8) {
+  for (size_t i = 0; i < length; i++) {
+    char c = name[i];
+    switch (c) {
+    case '"':
+    case '\\':
+      // These mess with encoding rules.
+      // Fall through.
+    case ',':
+      // Commas make it impossible to split the list of subject alternative
+      // names unambiguously, which is why we have to escape.
+      // Fall through.
+    case '\'':
+      // Single quotes are unlikely to appear in any legitimate values, but they
+      // could be used to make a value look like it was escaped (i.e., enclosed
+      // in single/double quotes).
+      return false;
+    default:
+      if (utf8) {
+        // In UTF8 strings, we require escaping for any ASCII control character,
+        // but NOT for non-ASCII characters. Note that all bytes of any code
+        // point that consists of more than a single byte have their MSB set.
+        if (static_cast<unsigned char>(c) < ' ' || c == '\x7f') {
+          return false;
+        }
+      } else {
+        // Check if the char is a control character or non-ASCII character. Note
+        // that char may or may not be a signed type. Regardless, non-ASCII
+        // values will always be outside of this range.
+        if (c < ' ' || c > '~') {
+          return false;
+        }
+      }
+    }
+  }
+  return true;
+}
 
-  if (method != X509V3_EXT_get_nid(NID_subject_alt_name))
-    return false;
+static inline void PrintAltName(const BIOPointer& out, const char* name,
+                                size_t length, bool utf8,
+                                const char* safe_prefix) {
+  if (IsSafeAltName(name, length, utf8)) {
+    // For backward-compatibility, append "safe" names without any
+    // modifications.
+    if (safe_prefix != nullptr) {
+      BIO_printf(out.get(), "%s:", safe_prefix);
+    }
+    BIO_write(out.get(), name, length);
+  } else {
+    // If a name is not "safe", we cannot embed it without special
+    // encoding. This does not usually happen, but we don't want to hide
+    // it from the user either. We use JSON compatible escaping here.
+    BIO_write(out.get(), "\"", 1);
+    if (safe_prefix != nullptr) {
+      BIO_printf(out.get(), "%s:", safe_prefix);
+    }
+    for (size_t j = 0; j < length; j++) {
+      char c = static_cast<char>(name[j]);
+      if (c == '\\') {
+        BIO_write(out.get(), "\\\\", 2);
+      } else if (c == '"') {
+        BIO_write(out.get(), "\\\"", 2);
+      } else if ((c >= ' ' && c != ',' && c <= '~') || (utf8 && (c & 0x80))) {
+        // Note that the above condition explicitly excludes commas, which means
+        // that those are encoded as Unicode escape sequences in the "else"
+        // block. That is not strictly necessary, and Node.js itself would parse
+        // it correctly either way. We only do this to account for third-party
+        // code that might be splitting the string at commas (as Node.js itself
+        // used to do).
+        BIO_write(out.get(), &c, 1);
+      } else {
+        // Control character or non-ASCII character. We treat everything as
+        // Latin-1, which corresponds to the first 255 Unicode code points.
+        const char hex[] = "0123456789abcdef";
+        char u[] = { '\\', 'u', '0', '0', hex[(c & 0xf0) >> 4], hex[c & 0x0f] };
+        BIO_write(out.get(), u, sizeof(u));
+      }
+    }
+    BIO_write(out.get(), "\"", 1);
+  }
+}
+
+static inline void PrintLatin1AltName(const BIOPointer& out,
+                                      const ASN1_IA5STRING* name,
+                                      const char* safe_prefix = nullptr) {
+  PrintAltName(out, reinterpret_cast<const char*>(name->data), name->length,
+               false, safe_prefix);
+}
+
+static inline void PrintUtf8AltName(const BIOPointer& out,
+                                    const ASN1_UTF8STRING* name,
+                                    const char* safe_prefix = nullptr) {
+  PrintAltName(out, reinterpret_cast<const char*>(name->data), name->length,
+               true, safe_prefix);
+}
+
+// This function currently emulates the behavior of i2v_GENERAL_NAME in a safer
+// and less ambiguous way.
+// TODO(tniessen): gradually improve the format in the next major version(s)
+static bool PrintGeneralName(const BIOPointer& out, const GENERAL_NAME* gen) {
+  if (gen->type == GEN_DNS) {
+    ASN1_IA5STRING* name = gen->d.dNSName;
+    BIO_write(out.get(), "DNS:", 4);
+    // Note that the preferred name syntax (see RFCs 5280 and 1034) with
+    // wildcards is a subset of what we consider "safe", so spec-compliant DNS
+    // names will never need to be escaped.
+    PrintLatin1AltName(out, name);
+  } else if (gen->type == GEN_EMAIL) {
+    ASN1_IA5STRING* name = gen->d.rfc822Name;
+    BIO_write(out.get(), "email:", 6);
+    PrintLatin1AltName(out, name);
+  } else if (gen->type == GEN_URI) {
+    ASN1_IA5STRING* name = gen->d.uniformResourceIdentifier;
+    BIO_write(out.get(), "URI:", 4);
+    // The set of "safe" names was designed to include just about any URI,
+    // with a few exceptions, most notably URIs that contains commas (see
+    // RFC 2396). In other words, most legitimate URIs will not require
+    // escaping.
+    PrintLatin1AltName(out, name);
+  } else if (gen->type == GEN_DIRNAME) {
+    // For backward compatibility, use X509_NAME_oneline to print the
+    // X509_NAME object. The format is non standard and should be avoided
+    // elsewhere, but conveniently, the function produces ASCII and the output
+    // is unlikely to contains commas or other characters that would require
+    // escaping. With that in mind, note that it SHOULD NOT produce ASCII
+    // output since an RFC5280 AttributeValue may be a UTF8String.
+    // TODO(tniessen): switch to RFC2253 rules in a major release
+    BIO_printf(out.get(), "DirName:");
+    char oline[256];
+    if (X509_NAME_oneline(gen->d.dirn, oline, sizeof(oline)) != nullptr) {
+      PrintAltName(out, oline, strlen(oline), false, nullptr);
+    } else {
+      return false;
+    }
+  } else if (gen->type == GEN_IPADD) {
+    BIO_printf(out.get(), "IP Address:");
+    const ASN1_OCTET_STRING* ip = gen->d.ip;
+    const unsigned char* b = ip->data;
+    if (ip->length == 4) {
+      BIO_printf(out.get(), "%d.%d.%d.%d", b[0], b[1], b[2], b[3]);
+    } else if (ip->length == 16) {
+      for (unsigned int j = 0; j < 8; j++) {
+        uint16_t pair = (b[2 * j] << 8) | b[2 * j + 1];
+        BIO_printf(out.get(), (j == 0) ? "%X" : ":%X", pair);
+      }
+    } else {
+#if OPENSSL_VERSION_MAJOR >= 3
+      BIO_printf(out.get(), "<invalid length=%d>", ip->length);
+#else
+      BIO_printf(out.get(), "<invalid>");
+#endif
+    }
+  } else if (gen->type == GEN_RID) {
+    // TODO(tniessen): unlike OpenSSL's default implementation, never print the
+    // OID as text and instead always print its numeric representation, which is
+    // backward compatible in practice and more future proof (see OBJ_obj2txt).
+    char oline[256];
+    i2t_ASN1_OBJECT(oline, sizeof(oline), gen->d.rid);
+    BIO_printf(out.get(), "Registered ID:%s", oline);
+  } else if (gen->type == GEN_OTHERNAME) {
+    // TODO(tniessen): the format that is used here is based on OpenSSL's
+    // implementation of i2v_GENERAL_NAME (as of OpenSSL 3.0.1), mostly for
+    // backward compatibility. It is somewhat awkward, especially when passed to
+    // translatePeerCertificate, and should be changed in the future, probably
+    // to the format used by GENERAL_NAME_print (in a major release).
+    bool unicode = true;
+    const char* prefix = nullptr;
+    // OpenSSL 1.1.1 does not support othername in i2v_GENERAL_NAME and may not
+    // define these NIDs.
+#if OPENSSL_VERSION_MAJOR >= 3
+    int nid = OBJ_obj2nid(gen->d.otherName->type_id);
+    switch (nid) {
+      case NID_id_on_SmtpUTF8Mailbox:
+        prefix = " SmtpUTF8Mailbox:";
+        break;
+      case NID_XmppAddr:
+        prefix = " XmppAddr:";
+        break;
+      case NID_SRVName:
+        prefix = " SRVName:";
+        unicode = false;
+        break;
+      case NID_ms_upn:
+        prefix = " UPN:";
+        break;
+      case NID_NAIRealm:
+        prefix = " NAIRealm:";
+        break;
+    }
+#endif  // OPENSSL_VERSION_MAJOR >= 3
+    int val_type = gen->d.otherName->value->type;
+    if (prefix == nullptr ||
+        (unicode && val_type != V_ASN1_UTF8STRING) ||
+        (!unicode && val_type != V_ASN1_IA5STRING)) {
+      BIO_printf(out.get(), "othername:<unsupported>");
+    } else {
+      BIO_printf(out.get(), "othername:");
+      if (unicode) {
+        PrintUtf8AltName(out, gen->d.otherName->value->value.utf8string,
+                         prefix);
+      } else {
+        PrintLatin1AltName(out, gen->d.otherName->value->value.ia5string,
+                           prefix);
+      }
+    }
+  } else if (gen->type == GEN_X400) {
+    // TODO(tniessen): this is what OpenSSL does, implement properly instead
+    BIO_printf(out.get(), "X400Name:<unsupported>");
+  } else if (gen->type == GEN_EDIPARTY) {
+    // TODO(tniessen): this is what OpenSSL does, implement properly instead
+    BIO_printf(out.get(), "EdiPartyName:<unsupported>");
+  } else {
+    // This is safe because X509V3_EXT_d2i would have returned nullptr in this
+    // case already.
+    UNREACHABLE();
+  }
+
+  return true;
+}
+
+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));
 
   GENERAL_NAMES* names = static_cast<GENERAL_NAMES*>(X509V3_EXT_d2i(ext));
   if (names == nullptr)
     return false;
 
+  bool ok = true;
+
   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)
-        return false;
-      X509V3_EXT_val_prn(out.get(), nval, 0, 0);
-      sk_CONF_VALUE_pop_free(nval, X509V3_conf_free);
+    if (!(ok = PrintGeneralName(out, gen))) {
+      break;
     }
   }
   sk_GENERAL_NAME_pop_free(names, GENERAL_NAME_free);
 
-  return true;
+  return ok;
+}
+
+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));
+
+  AUTHORITY_INFO_ACCESS* descs =
+      static_cast<AUTHORITY_INFO_ACCESS*>(X509V3_EXT_d2i(ext));
+  if (descs == nullptr)
+    return false;
+
+  bool ok = true;
+
+  for (int i = 0; i < sk_ACCESS_DESCRIPTION_num(descs); i++) {
+    ACCESS_DESCRIPTION* desc = sk_ACCESS_DESCRIPTION_value(descs, i);
+
+    if (i != 0)
+      BIO_write(out.get(), "\n", 1);
+
+    char objtmp[80];
+    i2t_ASN1_OBJECT(objtmp, sizeof(objtmp), desc->method);
+    BIO_printf(out.get(), "%s - ", objtmp);
+    if (!(ok = PrintGeneralName(out, desc->location))) {
+      break;
+    }
+  }
+  sk_ACCESS_DESCRIPTION_pop_free(descs, ACCESS_DESCRIPTION_free);
+
+#if OPENSSL_VERSION_MAJOR < 3
+  BIO_write(out.get(), "\n", 1);
+#endif
+
+  return ok;
+}
+
+v8::MaybeLocal<v8::Value> GetSubjectAltNameString(
+    Environment* env,
+    const BIOPointer& bio,
+    X509* cert) {
+  int index = X509_get_ext_by_NID(cert, NID_subject_alt_name, -1);
+  if (index < 0)
+    return Undefined(env->isolate());
+
+  X509_EXTENSION* ext = X509_get_ext(cert, index);
+  CHECK_NOT_NULL(ext);
+
+  if (!SafeX509SubjectAltNamePrint(bio, ext)) {
+    USE(BIO_reset(bio.get()));
+    return v8::Null(env->isolate());
+  }
+
+  return ToV8Value(env, bio);
+}
+
+v8::MaybeLocal<v8::Value> GetInfoAccessString(
+    Environment* env,
+    const BIOPointer& bio,
+    X509* cert) {
+  int index = X509_get_ext_by_NID(cert, NID_info_access, -1);
+  if (index < 0)
+    return Undefined(env->isolate());
+
+  X509_EXTENSION* ext = X509_get_ext(cert, index);
+  CHECK_NOT_NULL(ext);
+
+  if (!SafeX509InfoAccessPrint(bio, ext)) {
+    USE(BIO_reset(bio.get()));
+    return v8::Null(env->isolate());
+  }
+
+  return ToV8Value(env, bio);
 }
 
 MaybeLocal<Value> GetIssuerString(
@@ -931,11 +1212,11 @@ MaybeLocal<Object> X509ToObject(Environment* env, X509* cert) {
       !Set<Value>(context,
                   info,
                   env->subjectaltname_string(),
-                  GetInfoString<NID_subject_alt_name>(env, bio, cert)) ||
+                  GetSubjectAltNameString(env, bio, cert)) ||
       !Set<Value>(context,
                   info,
                   env->infoaccess_string(),
-                  GetInfoString<NID_info_access>(env, bio, cert))) {
+                  GetInfoAccessString(env, bio, cert))) {
     return MaybeLocal<Object>();
   }
 
diff --git a/src/crypto/crypto_common.h b/src/crypto/crypto_common.h
index 2c578b7be435cb..b916c4c7eb6126 100644
--- a/src/crypto/crypto_common.h
+++ b/src/crypto/crypto_common.h
@@ -140,7 +140,7 @@ v8::MaybeLocal<v8::Value> GetSerialNumber(Environment* env, X509* cert);
 v8::MaybeLocal<v8::Object> GetRawDERCertificate(Environment* env, X509* cert);
 
 v8::Local<v8::Value> ToV8Value(Environment* env, const BIOPointer& bio);
-bool SafeX509ExtPrint(const BIOPointer& out, X509_EXTENSION* ext);
+bool SafeX509SubjectAltNamePrint(const BIOPointer& out, X509_EXTENSION* ext);
 
 v8::MaybeLocal<v8::Value> GetSubject(
     Environment* env,
@@ -152,26 +152,15 @@ v8::MaybeLocal<v8::Value> GetIssuerString(
     const BIOPointer& bio,
     X509* cert);
 
-template <int nid>
-v8::MaybeLocal<v8::Value> GetInfoString(
+v8::MaybeLocal<v8::Value> GetSubjectAltNameString(
     Environment* env,
     const BIOPointer& bio,
-    X509* cert) {
-  int index = X509_get_ext_by_NID(cert, nid, -1);
-  if (index < 0)
-    return Undefined(env->isolate());
-
-  X509_EXTENSION* ext = X509_get_ext(cert, index);
-  CHECK_NOT_NULL(ext);
-
-  if (!SafeX509ExtPrint(bio, ext) &&
-      X509V3_EXT_print(bio.get(), ext, 0, 0) != 1) {
-    USE(BIO_reset(bio.get()));
-    return v8::Null(env->isolate());
-  }
+    X509* cert);
 
-  return ToV8Value(env, bio);
-}
+v8::MaybeLocal<v8::Value> GetInfoAccessString(
+    Environment* env,
+    const BIOPointer& bio,
+    X509* cert);
 
 }  // namespace crypto
 }  // namespace node
diff --git a/src/crypto/crypto_x509.cc b/src/crypto/crypto_x509.cc
index cb34003c4dded8..3cfa842664b21a 100644
--- a/src/crypto/crypto_x509.cc
+++ b/src/crypto/crypto_x509.cc
@@ -216,7 +216,7 @@ void X509Certificate::SubjectAltName(const FunctionCallbackInfo<Value>& args) {
   ASSIGN_OR_RETURN_UNWRAP(&cert, args.Holder());
   BIOPointer bio(BIO_new(BIO_s_mem()));
   Local<Value> ret;
-  if (GetInfoString<NID_subject_alt_name>(env, bio, cert->get()).ToLocal(&ret))
+  if (GetSubjectAltNameString(env, bio, cert->get()).ToLocal(&ret))
     args.GetReturnValue().Set(ret);
 }
 
@@ -226,7 +226,7 @@ void X509Certificate::InfoAccess(const FunctionCallbackInfo<Value>& args) {
   ASSIGN_OR_RETURN_UNWRAP(&cert, args.Holder());
   BIOPointer bio(BIO_new(BIO_s_mem()));
   Local<Value> ret;
-  if (GetInfoString<NID_info_access>(env, bio, cert->get()).ToLocal(&ret))
+  if (GetInfoAccessString(env, bio, cert->get()).ToLocal(&ret))
     args.GetReturnValue().Set(ret);
 }
 
diff --git a/test/fixtures/keys/Makefile b/test/fixtures/keys/Makefile
index a825cace1bf7bb..e5dab9e046dd17 100644
--- a/test/fixtures/keys/Makefile
+++ b/test/fixtures/keys/Makefile
@@ -85,6 +85,8 @@ all: \
   ec_p521_public.pem \
   ec_secp256k1_private.pem \
   ec_secp256k1_public.pem \
+  incorrect_san_correct_subject-cert.pem \
+  incorrect_san_correct_subject-key.pem \
 
 #
 # Create Certificate Authority: ca1
@@ -781,6 +783,18 @@ ec_secp256k1_private.pem:
 ec_secp256k1_public.pem: ec_secp256k1_private.pem
 	openssl ec -in ec_secp256k1_private.pem -pubout -out ec_secp256k1_public.pem
 
+incorrect_san_correct_subject-cert.pem: incorrect_san_correct_subject-key.pem
+	openssl req -x509 \
+	            -key incorrect_san_correct_subject-key.pem \
+	            -out incorrect_san_correct_subject-cert.pem \
+	            -sha256 \
+	            -days 3650 \
+	            -subj "/CN=good.example.com" \
+	            -addext "subjectAltName = DNS:evil.example.com"
+
+incorrect_san_correct_subject-key.pem:
+	openssl ecparam -name prime256v1 -genkey -noout -out incorrect_san_correct_subject-key.pem
+
 clean:
 	rm -f *.pfx *.pem *.srl ca2-database.txt ca2-serial fake-startcom-root-serial *.print *.old fake-startcom-root-issued-certs/*.pem
 	@> fake-startcom-root-database.txt
diff --git a/test/fixtures/keys/incorrect_san_correct_subject-cert.pem b/test/fixtures/keys/incorrect_san_correct_subject-cert.pem
new file mode 100644
index 00000000000000..787d9f113511d6
--- /dev/null
+++ b/test/fixtures/keys/incorrect_san_correct_subject-cert.pem
@@ -0,0 +1,11 @@
+-----BEGIN CERTIFICATE-----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=
+-----END CERTIFICATE-----
diff --git a/test/fixtures/keys/incorrect_san_correct_subject-key.pem b/test/fixtures/keys/incorrect_san_correct_subject-key.pem
new file mode 100644
index 00000000000000..f7f51253a8f7ed
--- /dev/null
+++ b/test/fixtures/keys/incorrect_san_correct_subject-key.pem
@@ -0,0 +1,5 @@
+-----BEGIN EC PRIVATE KEY-----
+MHcCAQEEIOOVRgLS3H2T2fUhj4ASCFq60ySwO6yvSK6rvZHldAHuoAoGCCqGSM49
+AwEHoUQDQgAEkPwimubjGbi2LLJzTpuwz3cNyOQ6GtEKcn93Eu2hmrXyt7bmPKhu
+5yeThrZdVji/4DdL0UTdPygP4kSco2n88w==
+-----END EC PRIVATE KEY-----
diff --git a/test/fixtures/x509-escaping/.gitignore b/test/fixtures/x509-escaping/.gitignore
new file mode 100644
index 00000000000000..504afef81fbadc
--- /dev/null
+++ b/test/fixtures/x509-escaping/.gitignore
@@ -0,0 +1,2 @@
+node_modules/
+package-lock.json
diff --git a/test/fixtures/x509-escaping/alt-0-cert.pem b/test/fixtures/x509-escaping/alt-0-cert.pem
new file mode 100644
index 00000000000000..30e6fa6c3fa83a
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-0-cert.pem
@@ -0,0 +1,29 @@
+-----BEGIN CERTIFICATE-----
+MIIE5jCCAs6gAwIBAgIBATANBgkqhkiG9w0BAQsFADAbMRkwFwYDVQQDExBldmls
+LmV4YW1wbGUuY29tMB4XDTIxMTIyMDE0NTczNVoXDTMxMTIxODE0NTczNVowGzEZ
+MBcGA1UEAxMQZXZpbC5leGFtcGxlLmNvbTCCAiIwDQYJKoZIhvcNAQEBBQADggIP
+ADCCAgoCggIBALERZ3TS70T1P+SjpZwIqOFnu2Od9XKWcDszQQc7C92K+APjp4Bv
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+DnVXZ3paRJTcps6d/Ylb5Ald/Ow056JgD0Cd9jn16+vgYR4bxVl0a5Qbf24MIhaY
+BRPx6WFdepWr410GpzpVQ0sMluoKYzH8RynjwQc7pfm5ebTFWJkhU80jOqKJGFW3
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+UoyzTvwN2i/uPqJxi/9FkdV60OWvMMMeMslbDHIBbN0Z2SG0wY93oH2LhO0X89Tc
+nedukufld8QEW7iMn7D7la+TlrrSAXURHL84sEz97yyujawQEimnW03XAlUFk61M
+iLhVUOHANFBSLBvZ3VF7sZDv6ZzPkP/TWrFbpL7DQgqunAlSNHealrQ5T3wp8pUm
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+i3TgLxhp7XNS/bh/f2tDx+7ZgdtHUlkNhl1MycIVQRGK3BaZBEd+sDxS52kwym5I
+CWLXGLutU3OeaNgqyvZuMvy//2oER3PysizyjwNoFlUbIz3zMnXvBeEjeGtEHsCJ
+EBtX+xBWwMhUKE2QcMLxQaZNJCZFVFw8fDeEgFjTdEBcLsZ1PngT3jgXSHEWA+YL
+C3rQhFMjyjy2h8u1sjySFrTlbZPm8gC3q/+LaXxhf5i5xiZOOcVfeYiWFUa5gQal
+FaWj2SlQFaN2nidPaQO62vRIYn0Y/qbtUQAPkq4VVeycgxiuZaVVWCdct8UCYb9F
+b9QSMpK4r99MKy+s41RiJodDJy0XraOxy7hUDjyObL2fuuPUK6mQAFGwWtajv3qq
+vrRMvBEXdOPVmbETyzIosUHvOXT+v8WoCbC14mqMZTWVywRg7bD/NTHJDRIBrqvi
+O6Zqbod3EImVnQ==
+-----END CERTIFICATE-----
diff --git a/test/fixtures/x509-escaping/alt-1-cert.pem b/test/fixtures/x509-escaping/alt-1-cert.pem
new file mode 100644
index 00000000000000..63883c2bbf7f91
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-1-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
+MIIE0zCCArugAwIBAgIBATANBgkqhkiG9w0BAQsFADAbMRkwFwYDVQQDExBldmls
+LmV4YW1wbGUuY29tMB4XDTIxMTIyMDE0NTczNVoXDTMxMTIxODE0NTczNVowGzEZ
+MBcGA1UEAxMQZXZpbC5leGFtcGxlLmNvbTCCAiIwDQYJKoZIhvcNAQEBBQADggIP
+ADCCAgoCggIBALERZ3TS70T1P+SjpZwIqOFnu2Od9XKWcDszQQc7C92K+APjp4Bv
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+-----END CERTIFICATE-----
diff --git a/test/fixtures/x509-escaping/alt-10-cert.pem b/test/fixtures/x509-escaping/alt-10-cert.pem
new file mode 100644
index 00000000000000..14bec45d284e26
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-10-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-11-cert.pem b/test/fixtures/x509-escaping/alt-11-cert.pem
new file mode 100644
index 00000000000000..694cb7e9d8d879
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-11-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-12-cert.pem b/test/fixtures/x509-escaping/alt-12-cert.pem
new file mode 100644
index 00000000000000..7e48ebdf052c94
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-12-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-13-cert.pem b/test/fixtures/x509-escaping/alt-13-cert.pem
new file mode 100644
index 00000000000000..574ad1ca8f3cf9
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-13-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-14-cert.pem b/test/fixtures/x509-escaping/alt-14-cert.pem
new file mode 100644
index 00000000000000..0265b5992c1dbc
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-14-cert.pem
@@ -0,0 +1,29 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-15-cert.pem b/test/fixtures/x509-escaping/alt-15-cert.pem
new file mode 100644
index 00000000000000..70a98fb90bb96f
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-15-cert.pem
@@ -0,0 +1,29 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-16-cert.pem b/test/fixtures/x509-escaping/alt-16-cert.pem
new file mode 100644
index 00000000000000..64f852ceebb476
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-16-cert.pem
@@ -0,0 +1,29 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-17-cert.pem b/test/fixtures/x509-escaping/alt-17-cert.pem
new file mode 100644
index 00000000000000..f09f41b91841d5
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-17-cert.pem
@@ -0,0 +1,29 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-18-cert.pem b/test/fixtures/x509-escaping/alt-18-cert.pem
new file mode 100644
index 00000000000000..341ac0b7cec24d
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-18-cert.pem
@@ -0,0 +1,29 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-19-cert.pem b/test/fixtures/x509-escaping/alt-19-cert.pem
new file mode 100644
index 00000000000000..f16318420442e2
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-19-cert.pem
@@ -0,0 +1,29 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-2-cert.pem b/test/fixtures/x509-escaping/alt-2-cert.pem
new file mode 100644
index 00000000000000..6ae58f56360276
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-2-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-20-cert.pem b/test/fixtures/x509-escaping/alt-20-cert.pem
new file mode 100644
index 00000000000000..eca176f2df0c28
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-20-cert.pem
@@ -0,0 +1,29 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-21-cert.pem b/test/fixtures/x509-escaping/alt-21-cert.pem
new file mode 100644
index 00000000000000..16d5e7265bc3f5
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-21-cert.pem
@@ -0,0 +1,29 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-22-cert.pem b/test/fixtures/x509-escaping/alt-22-cert.pem
new file mode 100644
index 00000000000000..5f89b00dfdce1f
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-22-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-23-cert.pem b/test/fixtures/x509-escaping/alt-23-cert.pem
new file mode 100644
index 00000000000000..5cd6795cded659
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-23-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-24-cert.pem b/test/fixtures/x509-escaping/alt-24-cert.pem
new file mode 100644
index 00000000000000..2a858dd39a2db9
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-24-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-25-cert.pem b/test/fixtures/x509-escaping/alt-25-cert.pem
new file mode 100644
index 00000000000000..695b8ebba88ceb
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-25-cert.pem
@@ -0,0 +1,29 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-26-cert.pem b/test/fixtures/x509-escaping/alt-26-cert.pem
new file mode 100644
index 00000000000000..1204d95a8a5793
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-26-cert.pem
@@ -0,0 +1,29 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-27-cert.pem b/test/fixtures/x509-escaping/alt-27-cert.pem
new file mode 100644
index 00000000000000..268abdd300914f
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-27-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-28-cert.pem b/test/fixtures/x509-escaping/alt-28-cert.pem
new file mode 100644
index 00000000000000..147fba3aff2fae
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-28-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-29-cert.pem b/test/fixtures/x509-escaping/alt-29-cert.pem
new file mode 100644
index 00000000000000..434bda3e8e7988
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-29-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-3-cert.pem b/test/fixtures/x509-escaping/alt-3-cert.pem
new file mode 100644
index 00000000000000..59185b64a4dc5d
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-3-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-30-cert.pem b/test/fixtures/x509-escaping/alt-30-cert.pem
new file mode 100644
index 00000000000000..1b67d1f7823ad1
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-30-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-4-cert.pem b/test/fixtures/x509-escaping/alt-4-cert.pem
new file mode 100644
index 00000000000000..086af8e02e2c19
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-4-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-5-cert.pem b/test/fixtures/x509-escaping/alt-5-cert.pem
new file mode 100644
index 00000000000000..04a918008c67b8
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-5-cert.pem
@@ -0,0 +1,29 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-6-cert.pem b/test/fixtures/x509-escaping/alt-6-cert.pem
new file mode 100644
index 00000000000000..664351995793fb
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-6-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-7-cert.pem b/test/fixtures/x509-escaping/alt-7-cert.pem
new file mode 100644
index 00000000000000..6c0f287a1be1f7
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-7-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/alt-8-cert.pem b/test/fixtures/x509-escaping/alt-8-cert.pem
new file mode 100644
index 00000000000000..201b520f8bf976
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-8-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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+-----END CERTIFICATE-----
diff --git a/test/fixtures/x509-escaping/alt-9-cert.pem b/test/fixtures/x509-escaping/alt-9-cert.pem
new file mode 100644
index 00000000000000..660e65b8ed7ebd
--- /dev/null
+++ b/test/fixtures/x509-escaping/alt-9-cert.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----
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+aRjqayh3TDU8NwuFlLd6aH95hovjMBBatWFB9bN/itnMVoj9rmfSjvlpSRO6/EMN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+-----END CERTIFICATE-----
diff --git a/test/fixtures/x509-escaping/create-certs.js b/test/fixtures/x509-escaping/create-certs.js
new file mode 100644
index 00000000000000..b84547e1d0aef9
--- /dev/null
+++ b/test/fixtures/x509-escaping/create-certs.js
@@ -0,0 +1,502 @@
+'use strict';
+
+const asn1 = require('asn1.js');
+const crypto = require('crypto');
+const { writeFileSync } = require('fs');
+const rfc5280 = require('asn1.js-rfc5280');
+const BN = asn1.bignum;
+
+const oid = {
+  commonName: [2, 5, 4, 3],
+  countryName: [2, 5, 4, 6],
+  localityName: [2, 5, 4, 7],
+  rsaEncryption: [1, 2, 840, 113549, 1, 1, 1],
+  sha256WithRSAEncryption: [1, 2, 840, 113549, 1, 1, 11],
+  xmppAddr: [1, 3, 6, 1, 5, 5, 7, 8, 5],
+  srvName: [1, 3, 6, 1, 5, 5, 7, 8, 7],
+  ocsp: [1, 3, 6, 1, 5, 5, 7, 48, 1],
+  caIssuers: [1, 3, 6, 1, 5, 5, 7, 48, 2],
+  privateUnrecognized: [1, 3, 9999, 12, 34]
+};
+
+const digest = 'SHA256';
+
+const { privateKey, publicKey } = crypto.generateKeyPairSync('rsa', {
+  modulusLength: 4096,
+  publicKeyEncoding: {
+    type: 'pkcs1',
+    format: 'der'
+  }
+});
+
+writeFileSync('server-key.pem', privateKey.export({
+  type: 'pkcs8',
+  format: 'pem'
+}));
+
+const now = Date.now();
+const days = 3650;
+
+function utilType(name, fn) {
+  return asn1.define(name, function() {
+    this[fn]();
+  });
+}
+
+const Null_ = utilType('Null_', 'null_');
+const null_ = Null_.encode('der');
+
+const IA5String = utilType('IA5String', 'ia5str');
+const PrintableString = utilType('PrintableString', 'printstr');
+const UTF8String = utilType('UTF8String', 'utf8str');
+
+const subjectCommonName = PrintableString.encode('evil.example.com', 'der');
+
+const sans = [
+  { type: 'dNSName', value: 'good.example.com, DNS:evil.example.com' },
+  { type: 'uniformResourceIdentifier', value: 'http://example.com/' },
+  { type: 'uniformResourceIdentifier', value: 'http://example.com/?a=b&c=d' },
+  { type: 'uniformResourceIdentifier', value: 'http://example.com/a,b' },
+  { type: 'uniformResourceIdentifier', value: 'http://example.com/a%2Cb' },
+  {
+    type: 'uniformResourceIdentifier',
+    value: 'http://example.com/a, DNS:good.example.com'
+  },
+  { type: 'dNSName', value: Buffer.from('exämple.com', 'latin1') },
+  { type: 'dNSName', value: '"evil.example.com"' },
+  { type: 'iPAddress', value: Buffer.from('08080808', 'hex') },
+  { type: 'iPAddress', value: Buffer.from('08080404', 'hex') },
+  { type: 'iPAddress', value: Buffer.from('0008080404', 'hex') },
+  { type: 'iPAddress', value: Buffer.from('000102030405', 'hex') },
+  {
+    type: 'iPAddress',
+    value: Buffer.from('0a0b0c0d0e0f0000000000007a7b7c7d', 'hex')
+  },
+  { type: 'rfc822Name', value: 'foo@example.com' },
+  { type: 'rfc822Name', value: 'foo@example.com, DNS:good.example.com' },
+  {
+    type: 'directoryName',
+    value: {
+      type: 'rdnSequence',
+      value: [
+        [
+          {
+            type: oid.countryName,
+            value: PrintableString.encode('DE', 'der')
+          }
+        ],
+        [
+          {
+            type: oid.localityName,
+            value: UTF8String.encode('Hannover', 'der')
+          }
+        ]
+      ]
+    }
+  },
+  {
+    type: 'directoryName',
+    value: {
+      type: 'rdnSequence',
+      value: [
+        [
+          {
+            type: oid.countryName,
+            value: PrintableString.encode('DE', 'der')
+          }
+        ],
+        [
+          {
+            type: oid.localityName,
+            value: UTF8String.encode('München', 'der')
+          }
+        ]
+      ]
+    }
+  },
+  {
+    type: 'directoryName',
+    value: {
+      type: 'rdnSequence',
+      value: [
+        [
+          {
+            type: oid.countryName,
+            value: PrintableString.encode('DE', 'der')
+          }
+        ],
+        [
+          {
+            type: oid.localityName,
+            value: UTF8String.encode('Berlin, DNS:good.example.com', 'der')
+          }
+        ]
+      ]
+    }
+  },
+  {
+    type: 'directoryName',
+    value: {
+      type: 'rdnSequence',
+      value: [
+        [
+          {
+            type: oid.countryName,
+            value: PrintableString.encode('DE', 'der')
+          }
+        ],
+        [
+          {
+            type: oid.localityName,
+            value: UTF8String.encode('Berlin, DNS:good.example.com\0evil.example.com', 'der')
+          }
+        ]
+      ]
+    }
+  },
+  {
+    type: 'directoryName',
+    value: {
+      type: 'rdnSequence',
+      value: [
+        [
+          {
+            type: oid.countryName,
+            value: PrintableString.encode('DE', 'der')
+          }
+        ],
+        [
+          {
+            type: oid.localityName,
+            value: UTF8String.encode(
+              'Berlin, DNS:good.example.com\\\0evil.example.com', 'der')
+          }
+        ]
+      ]
+    }
+  },
+  {
+    type: 'directoryName',
+    value: {
+      type: 'rdnSequence',
+      value: [
+        [
+          {
+            type: oid.countryName,
+            value: PrintableString.encode('DE', 'der')
+          }
+        ],
+        [
+          {
+            type: oid.localityName,
+            value: UTF8String.encode('Berlin\r\n', 'der')
+          }
+        ]
+      ]
+    }
+  },
+  {
+    type: 'directoryName',
+    value: {
+      type: 'rdnSequence',
+      value: [
+        [
+          {
+            type: oid.countryName,
+            value: PrintableString.encode('DE', 'der')
+          }
+        ],
+        [
+          {
+            type: oid.localityName,
+            value: UTF8String.encode('Berlin/CN=good.example.com', 'der')
+          }
+        ]
+      ]
+    }
+  },
+  {
+    type: 'registeredID',
+    value: oid.sha256WithRSAEncryption
+  },
+  {
+    type: 'registeredID',
+    value: oid.privateUnrecognized
+  },
+  {
+    type: 'otherName',
+    value: {
+      'type-id': oid.xmppAddr,
+      value: UTF8String.encode('abc123', 'der')
+    }
+  },
+  {
+    type: 'otherName',
+    value: {
+      'type-id': oid.xmppAddr,
+      value: UTF8String.encode('abc123, DNS:good.example.com', 'der')
+    }
+  },
+  {
+    type: 'otherName',
+    value: {
+      'type-id': oid.xmppAddr,
+      value: UTF8String.encode('good.example.com\0abc123', 'der')
+    }
+  },
+  {
+    type: 'otherName',
+    value: {
+      'type-id': oid.privateUnrecognized,
+      value: UTF8String.encode('abc123', 'der')
+    }
+  },
+  {
+    type: 'otherName',
+    value: {
+      'type-id': oid.srvName,
+      value: IA5String.encode('abc123', 'der')
+    }
+  },
+  {
+    type: 'otherName',
+    value: {
+      'type-id': oid.srvName,
+      value: UTF8String.encode('abc123', 'der')
+    }
+  },
+  {
+    type: 'otherName',
+    value: {
+      'type-id': oid.srvName,
+      value: IA5String.encode('abc\0def', 'der')
+    }
+  }
+];
+
+for (let i = 0; i < sans.length; i++) {
+  const san = sans[i];
+
+  const tbs = {
+    version: 'v3',
+    serialNumber: new BN('01', 16),
+    signature: {
+      algorithm: oid.sha256WithRSAEncryption,
+      parameters: null_
+    },
+    issuer: {
+      type: 'rdnSequence',
+      value: [
+        [
+          { type: oid.commonName, value: subjectCommonName }
+        ]
+      ]
+    },
+    validity: {
+      notBefore: { type: 'utcTime', value: now },
+      notAfter: { type: 'utcTime', value: now + days * 86400000 }
+    },
+    subject: {
+      type: 'rdnSequence',
+      value: [
+        [
+          { type: oid.commonName, value: subjectCommonName }
+        ]
+      ]
+    },
+    subjectPublicKeyInfo: {
+      algorithm: {
+        algorithm: oid.rsaEncryption,
+        parameters: null_
+      },
+      subjectPublicKey: {
+        unused: 0,
+        data: publicKey
+      }
+    },
+    extensions: [
+      {
+        extnID: 'subjectAlternativeName',
+        critical: false,
+        extnValue: [san]
+      }
+    ]
+  };
+
+  // Self-sign the certificate.
+  const tbsDer = rfc5280.TBSCertificate.encode(tbs, 'der');
+  const signature = crypto.createSign(digest).update(tbsDer).sign(privateKey);
+
+  // Construct the signed certificate.
+  const cert = {
+    tbsCertificate: tbs,
+    signatureAlgorithm: {
+      algorithm: oid.sha256WithRSAEncryption,
+      parameters: null_
+    },
+    signature: {
+      unused: 0,
+      data: signature
+    }
+  };
+
+  // Store the signed certificate.
+  const pem = rfc5280.Certificate.encode(cert, 'pem', {
+    label: 'CERTIFICATE'
+  });
+  writeFileSync(`./alt-${i}-cert.pem`, `${pem}\n`);
+}
+
+const infoAccessExtensions = [
+  [
+    {
+      accessMethod: oid.ocsp,
+      accessLocation: {
+        type: 'uniformResourceIdentifier',
+        value: 'http://good.example.com/\nOCSP - URI:http://evil.example.com/',
+      },
+    },
+  ],
+  [
+    {
+      accessMethod: oid.caIssuers,
+      accessLocation: {
+        type: 'uniformResourceIdentifier',
+        value: 'http://ca.example.com/\nOCSP - URI:http://evil.example.com',
+      },
+    },
+    {
+      accessMethod: oid.ocsp,
+      accessLocation: {
+        type: 'dNSName',
+        value: 'good.example.com\nOCSP - URI:http://ca.nodejs.org/ca.cert',
+      },
+    },
+  ],
+  [
+    {
+      accessMethod: oid.privateUnrecognized,
+      accessLocation: {
+        type: 'uniformResourceIdentifier',
+        value: 'http://ca.example.com/',
+      },
+    },
+  ],
+  [
+    {
+      accessMethod: oid.ocsp,
+      accessLocation: {
+        type: 'otherName',
+        value: {
+          'type-id': oid.xmppAddr,
+          value: UTF8String.encode('good.example.com', 'der'),
+        },
+      },
+    },
+    {
+      accessMethod: oid.ocsp,
+      accessLocation: {
+        type: 'otherName',
+        value: {
+          'type-id': oid.privateUnrecognized,
+          value: UTF8String.encode('abc123', 'der')
+        },
+      },
+    },
+    {
+      accessMethod: oid.ocsp,
+      accessLocation: {
+        type: 'otherName',
+        value: {
+          'type-id': oid.srvName,
+          value: IA5String.encode('abc123', 'der')
+        }
+      }
+    },
+  ],
+  [
+    {
+      accessMethod: oid.ocsp,
+      accessLocation: {
+        type: 'otherName',
+        value: {
+          'type-id': oid.xmppAddr,
+          value: UTF8String.encode('good.example.com\0abc123', 'der'),
+        },
+      },
+    },
+  ],
+];
+
+for (let i = 0; i < infoAccessExtensions.length; i++) {
+  const infoAccess = infoAccessExtensions[i];
+
+  const tbs = {
+    version: 'v3',
+    serialNumber: new BN('01', 16),
+    signature: {
+      algorithm: oid.sha256WithRSAEncryption,
+      parameters: null_
+    },
+    issuer: {
+      type: 'rdnSequence',
+      value: [
+        [
+          { type: oid.commonName, value: subjectCommonName }
+        ]
+      ]
+    },
+    validity: {
+      notBefore: { type: 'utcTime', value: now },
+      notAfter: { type: 'utcTime', value: now + days * 86400000 }
+    },
+    subject: {
+      type: 'rdnSequence',
+      value: [
+        [
+          { type: oid.commonName, value: subjectCommonName }
+        ]
+      ]
+    },
+    subjectPublicKeyInfo: {
+      algorithm: {
+        algorithm: oid.rsaEncryption,
+        parameters: null_
+      },
+      subjectPublicKey: {
+        unused: 0,
+        data: publicKey
+      }
+    },
+    extensions: [
+      {
+        extnID: 'authorityInformationAccess',
+        critical: false,
+        extnValue: infoAccess
+      }
+    ]
+  };
+
+  // Self-sign the certificate.
+  const tbsDer = rfc5280.TBSCertificate.encode(tbs, 'der');
+  const signature = crypto.createSign(digest).update(tbsDer).sign(privateKey);
+
+  // Construct the signed certificate.
+  const cert = {
+    tbsCertificate: tbs,
+    signatureAlgorithm: {
+      algorithm: oid.sha256WithRSAEncryption,
+      parameters: null_
+    },
+    signature: {
+      unused: 0,
+      data: signature
+    }
+  };
+
+  // Store the signed certificate.
+  const pem = rfc5280.Certificate.encode(cert, 'pem', {
+    label: 'CERTIFICATE'
+  });
+  writeFileSync(`./info-${i}-cert.pem`, `${pem}\n`);
+}
diff --git a/test/fixtures/x509-escaping/google/intermediate.pem b/test/fixtures/x509-escaping/google/intermediate.pem
new file mode 100644
index 00000000000000..9d2aeb32c4e5e5
--- /dev/null
+++ b/test/fixtures/x509-escaping/google/intermediate.pem
@@ -0,0 +1,11 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/test/fixtures/x509-escaping/google/key.pem b/test/fixtures/x509-escaping/google/key.pem
new file mode 100644
index 00000000000000..102a9d8816cd63
--- /dev/null
+++ b/test/fixtures/x509-escaping/google/key.pem
@@ -0,0 +1,5 @@
+-----BEGIN PRIVATE KEY-----
+MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQgaNbpDxJET5xVHxd/
+ig5x2u2KUIe0jaCVWqarpIN/582hRANCAAR7DaOQvpvA47q2XxjMqxJVf/FvZm2f
+tiFRXNJMe/fhSlDh2CybdkFIw2mE5g4ShW5UBJe+sohqy5V9WRkYtM/B
+-----END PRIVATE KEY-----
diff --git a/test/fixtures/x509-escaping/google/leaf0.pem b/test/fixtures/x509-escaping/google/leaf0.pem
new file mode 100644
index 00000000000000..ce19dc96994ac0
--- /dev/null
+++ b/test/fixtures/x509-escaping/google/leaf0.pem
@@ -0,0 +1,10 @@
+-----BEGIN CERTIFICATE-----
+MIIBajCCARCgAwIBAgIBAzAKBggqhkjOPQQDAjAXMRUwEwYDVQQDEwxJbnRlcm1l
+ZGlhdGUwIBcNMDAwMTAxMDAwMDAwWhgPMjA5OTAxMDEwMDAwMDBaMA8xDTALBgNV
+BAMTBExlYWYwWTATBgcqhkjOPQIBBggqhkjOPQMBBwNCAAR7DaOQvpvA47q2XxjM
+qxJVf/FvZm2ftiFRXNJMe/fhSlDh2CybdkFIw2mE5g4ShW5UBJe+sohqy5V9WRkY
+tM/Bo1MwUTAMBgNVHRMBAf8EAjAAMB8GA1UdIwQYMBaAFCUZxhtiiFordL5cZ6oJ
+OLgssd4tMCAGA1UdEQQZMBeCFWJsYWguYXR0YWNrZXIuZXhhbXBsZTAKBggqhkjO
+PQQDAgNIADBFAiEA4NgHDxVrBjNW+So4MrRZMwDknvjRaBsB4j2IwVRKl4sCIDpg
+Bhm4ZdHwlUYrALkXa3dFBy8kXBkVumY7UJpbB2mO
+-----END CERTIFICATE-----
diff --git a/test/fixtures/x509-escaping/google/leaf1.pem b/test/fixtures/x509-escaping/google/leaf1.pem
new file mode 100644
index 00000000000000..0b45056656cab1
--- /dev/null
+++ b/test/fixtures/x509-escaping/google/leaf1.pem
@@ -0,0 +1,10 @@
+-----BEGIN CERTIFICATE-----
+MIIBdTCCARygAwIBAgIBBDAKBggqhkjOPQQDAjAXMRUwEwYDVQQDEwxJbnRlcm1l
+ZGlhdGUwIBcNMDAwMTAxMDAwMDAwWhgPMjA5OTAxMDEwMDAwMDBaMA8xDTALBgNV
+BAMTBExlYWYwWTATBgcqhkjOPQIBBggqhkjOPQMBBwNCAAR7DaOQvpvA47q2XxjM
+qxJVf/FvZm2ftiFRXNJMe/fhSlDh2CybdkFIw2mE5g4ShW5UBJe+sohqy5V9WRkY
+tM/Bo18wXTAMBgNVHRMBAf8EAjAAMB8GA1UdIwQYMBaAFCUZxhtiiFordL5cZ6oJ
+OLgssd4tMCwGA1UdEQQlMCOCCm5vZGVqcy5vcmeCFWJsYWguYXR0YWNrZXIuZXhh
+bXBsZTAKBggqhkjOPQQDAgNHADBEAiAOFFOCfA6c/iZWxbDn5QMjNdtZbtJPBcRv
+uEgSqWrGTAIgK5RK0xGK8UZb2aM2VjGNTYozlcwKaLgQukA+UnKrrJg=
+-----END CERTIFICATE-----
diff --git a/test/fixtures/x509-escaping/google/leaf2.pem b/test/fixtures/x509-escaping/google/leaf2.pem
new file mode 100644
index 00000000000000..9cf03fae7d2ae6
--- /dev/null
+++ b/test/fixtures/x509-escaping/google/leaf2.pem
@@ -0,0 +1,10 @@
+-----BEGIN CERTIFICATE-----
+MIIBejCCASCgAwIBAgIBBTAKBggqhkjOPQQDAjAXMRUwEwYDVQQDEwxJbnRlcm1l
+ZGlhdGUwIBcNMDAwMTAxMDAwMDAwWhgPMjA5OTAxMDEwMDAwMDBaMA8xDTALBgNV
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diff --git a/test/fixtures/x509-escaping/google/leaf3.pem b/test/fixtures/x509-escaping/google/leaf3.pem
new file mode 100644
index 00000000000000..55a64fdc898929
--- /dev/null
+++ b/test/fixtures/x509-escaping/google/leaf3.pem
@@ -0,0 +1,10 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/google/leaf4.pem b/test/fixtures/x509-escaping/google/leaf4.pem
new file mode 100644
index 00000000000000..668a659f45b540
--- /dev/null
+++ b/test/fixtures/x509-escaping/google/leaf4.pem
@@ -0,0 +1,10 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/google/root.pem b/test/fixtures/x509-escaping/google/root.pem
new file mode 100644
index 00000000000000..68eb00ae862fbb
--- /dev/null
+++ b/test/fixtures/x509-escaping/google/root.pem
@@ -0,0 +1,9 @@
+-----BEGIN CERTIFICATE-----
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new file mode 100644
index 00000000000000..6872b9870a6cab
--- /dev/null
+++ b/test/fixtures/x509-escaping/info-0-cert.pem
@@ -0,0 +1,30 @@
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diff --git a/test/fixtures/x509-escaping/info-1-cert.pem b/test/fixtures/x509-escaping/info-1-cert.pem
new file mode 100644
index 00000000000000..05247873d85981
--- /dev/null
+++ b/test/fixtures/x509-escaping/info-1-cert.pem
@@ -0,0 +1,31 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/info-2-cert.pem b/test/fixtures/x509-escaping/info-2-cert.pem
new file mode 100644
index 00000000000000..06212d4e12a5da
--- /dev/null
+++ b/test/fixtures/x509-escaping/info-2-cert.pem
@@ -0,0 +1,29 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/info-3-cert.pem b/test/fixtures/x509-escaping/info-3-cert.pem
new file mode 100644
index 00000000000000..1825949bd38193
--- /dev/null
+++ b/test/fixtures/x509-escaping/info-3-cert.pem
@@ -0,0 +1,30 @@
+-----BEGIN CERTIFICATE-----
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diff --git a/test/fixtures/x509-escaping/info-4-cert.pem b/test/fixtures/x509-escaping/info-4-cert.pem
new file mode 100644
index 00000000000000..8f1e69afec7510
--- /dev/null
+++ b/test/fixtures/x509-escaping/info-4-cert.pem
@@ -0,0 +1,29 @@
+-----BEGIN CERTIFICATE-----
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+DnVXZ3paRJTcps6d/Ylb5Ald/Ow056JgD0Cd9jn16+vgYR4bxVl0a5Qbf24MIhaY
+BRPx6WFdepWr410GpzpVQ0sMluoKYzH8RynjwQc7pfm5ebTFWJkhU80jOqKJGFW3
+icV/A9BmtOBqrb60Pv/MPXIQPg7UWGUOXm3AfY3v6gbToewSW5B0s+uPsh52md4Z
+UoyzTvwN2i/uPqJxi/9FkdV60OWvMMMeMslbDHIBbN0Z2SG0wY93oH2LhO0X89Tc
+nedukufld8QEW7iMn7D7la+TlrrSAXURHL84sEz97yyujawQEimnW03XAlUFk61M
+iLhVUOHANFBSLBvZ3VF7sZDv6ZzPkP/TWrFbpL7DQgqunAlSNHealrQ5T3wp8pUm
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+JERGpI/OE+vzfOtgj/Z46/+wn7jF0LBCin7Jn5Zw1a1TNsiHKAjqW/P4vJxxUW++
+FtYwJhI7XJehwNNFra9rSC5M4TkpaqAZnbPvWZWxWVJIEYFgNjnt+b/VOpRpv5bJ
+7BOlVvP+56KF+vlmCnzVBmlHcr45sZUZ3mw3Sb6dcF0V0VaNQKw/F5EteQyafIIl
+dvCwwV4OwLwPliPAvwYfVEI41Dv3mF4fN7k=
+-----END CERTIFICATE-----
diff --git a/test/fixtures/x509-escaping/package.json b/test/fixtures/x509-escaping/package.json
new file mode 100644
index 00000000000000..37d9f2a9385c46
--- /dev/null
+++ b/test/fixtures/x509-escaping/package.json
@@ -0,0 +1,12 @@
+{
+  "name": "x509-escaping",
+  "version": "1.0.0",
+  "description": "create certificates for x509-escaping test",
+  "main": "createCert.js",
+  "license": "SEE LICENSE IN ../../../LICENSE",
+  "private": true,
+  "dependencies": {
+    "asn1.js": "^5.4.1",
+    "asn1.js-rfc5280": "^3.0.0"
+  }
+}
diff --git a/test/fixtures/x509-escaping/server-key.pem b/test/fixtures/x509-escaping/server-key.pem
new file mode 100644
index 00000000000000..db1d2652d0b76d
--- /dev/null
+++ b/test/fixtures/x509-escaping/server-key.pem
@@ -0,0 +1,52 @@
+-----BEGIN PRIVATE KEY-----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+SonVx3MSJWm/Vrh5i4b/L/+9u7uumIjWYFK6pKdLerTfbXO7ZsNR9KDIOBLDnUcf
++6K2vcclZN7aga1S7wTsrX+k9C/OQuj8ONMWQHCxryp5RAmgtArTBrJZq8el1lcG
+518Vo4QuOqsqTdAhqiImoPKe4NNCs1iTS9BdCqNYiF8sbmeJAoIBAQDUuL5ebQ68
+6vqTKYD47ZtCzeqziN3Y/0a1BsyZh0/snNmK5WIr4T0vX0Y/XG0EpkZdpW3odMBv
+CemKs6Zm+pfOUGu20PTJcdSOXRbFiVYSeQnfa0l3iXZvY9Ottz/IU/mWPuU3hc18
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+bC6TjAHlvnN6n1LjaLwULUs9Rb2fkNUOqsgR+T8YlqbclJbzC7gW53M/68c9eOQ1
+Y01JnzsB3S2vAoIBAQDT8DP2djtzIg6GiNPRvfj9cWifMQWqqV8nNTU9Cnxn4MzO
+sVcuX+VQBXgblj13D5SC1Ed5ELDplMJYM5iBabPbYX2GtGq6qG83XHOSD0SEdXWw
+mN/SLUPPUwcGC+8yaPh8LO6jFY3cKmft9+T31Hnf35LPdfWyTZc0YexNlUkt5Kdg
+XvGkKn5j9RAZcwXrEXMDnhZLEZZ2qBj0C2El71hyBS0ysBnRyWNwR1dcSgx1sJ8H
+ZCH6NYvLtoqxU4Zm6684eHf9lA7uTL1JHC0kWzUwLqGtbTWp1h5FpL790NVTUkS/
+Lf7bnnTpZqt8vAtTVc0IxBPOvFLKlzALd+cg69XxAoIBAQCv6Sbkh2NMrzUQRZ42
+PKfMkuSoG2L6dABQ65J+0/swPHVZ+1830kf6yNsawqAU3DwMbSV6ujH4oUXUQcQ2
+HL01DCRHRn1nqQ6RvEF8kZnwJNAZRmu2wqKCcxc17Ph9/ZPEv7ZmN+w6MN0LDy4Z
+EdRFcyq7AD1SmeG5ugMu4ilSpU1K96ZuvrnZezeI0dDgKNgDotlwTN9/oM95EfSf
+NNJy7ma4iDPnj8S0o1pELnBQEkizIOtsqTpsFgDKUpyKp3golh3jbZvixAuwUHOx
+PdHZca/mB1KhjONPhEDPl8HZIznYQzn+Z3cNqoM58lMF/di834ogN7zguYHMhDUT
+0YhZAoIBAHlYhuni+gyrn4tyZgep68VXW7wQxSvgSj8cpZAuT/w0UKAU53J5QTWZ
+aGHeICXvgvpalUL+2dGwASlOvPa52ekcOPd2+qKWyss0zA4ksI7mNE2vjFUcOr+S
+n9QSNvu3E8dYAjzSIsizcQbPTlk6A/TmytNJ4x67ZVGCmKXw1ZzzSrxSbAIdY254
+TxSGchrfcy0ofXIL2HXq16FRmesORTJFkkyQaldzn4y7S6HJ/vGppImTfeac1MwG
+jLYljIkIbt+nB1c8HeNvARmBa6M2pxB9f72oRMVqFdUUc5AxXuWP9v6xk227EuCq
+TBORAafu9WxKVwUsHa1rE1uGgNEfRJ8=
+-----END PRIVATE KEY-----
diff --git a/test/parallel/test-tls-0-dns-altname.js b/test/parallel/test-tls-0-dns-altname.js
index 4bc87e44cb60c1..e5cb8e3d487af1 100644
--- a/test/parallel/test-tls-0-dns-altname.js
+++ b/test/parallel/test-tls-0-dns-altname.js
@@ -44,7 +44,7 @@ const server = tls.createServer({
   }, common.mustCall(() => {
     const cert = c.getPeerCertificate();
     assert.strictEqual(cert.subjectaltname,
-                       'DNS:good.example.org\0.evil.example.com, ' +
+                       'DNS:"good.example.org\\u0000.evil.example.com", ' +
                            'DNS:just-another.example.com, ' +
                            'IP Address:8.8.8.8, ' +
                            'IP Address:8.8.4.4, ' +
diff --git a/test/parallel/test-x509-escaping.js b/test/parallel/test-x509-escaping.js
new file mode 100644
index 00000000000000..5904e01e43f481
--- /dev/null
+++ b/test/parallel/test-x509-escaping.js
@@ -0,0 +1,338 @@
+'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 that all certificate chains provided by the reporter are rejected.
+{
+  const rootPEM = fixtures.readSync('x509-escaping/google/root.pem');
+  const intermPEM = fixtures.readSync('x509-escaping/google/intermediate.pem');
+  const keyPEM = fixtures.readSync('x509-escaping/google/key.pem');
+
+  const numLeaves = 5;
+
+  for (let i = 0; i < numLeaves; i++) {
+    // TODO(tniessen): this test case requires proper handling of URI SANs,
+    // which node currently does not implement.
+    if (i === 3) continue;
+
+    const name = `x509-escaping/google/leaf${i}.pem`;
+    const leafPEM = fixtures.readSync(name, 'utf8');
+
+    const server = tls.createServer({
+      key: keyPEM,
+      cert: leafPEM + intermPEM,
+    }, common.mustNotCall()).listen(common.mustCall(() => {
+      const { port } = server.address();
+      const socket = tls.connect(port, {
+        ca: rootPEM,
+        servername: 'nodejs.org',
+      }, common.mustNotCall());
+      socket.on('error', common.mustCall());
+    })).unref();
+  }
+}
+
+// Test escaping rules for subject alternative names.
+{
+  const expectedSANs = [
+    'DNS:"good.example.com\\u002c 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\\u002cb"',
+    // Percent encoding should not require escaping.
+    'URI:http://example.com/a%2Cb',
+    // Malicious attempts should be escaped.
+    'URI:"http://example.com/a\\u002c DNS:good.example.com"',
+    // Non-ASCII characters in DNS names should be treated as Latin-1.
+    'DNS:"ex\\u00e4mple.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\\u002c 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\\u002c DNS:good.example.com"',
+    'DirName:"/C=DE/L=Berlin\\u002c DNS:good.example.com\\\\x00' +
+      'evil.example.com"',
+    'DirName:"/C=DE/L=Berlin\\u002c 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 should not know it.
+    'Registered ID:1.3.9999.12.34',
+    hasOpenSSL3 ?
+      'othername: XmppAddr::abc123' :
+      'othername:<unsupported>',
+    hasOpenSSL3 ?
+      'othername:" XmppAddr::abc123\\u002c DNS:good.example.com"' :
+      'othername:<unsupported>',
+    hasOpenSSL3 ?
+      'othername:" XmppAddr::good.example.com\\u0000abc123"' :
+      'othername:<unsupported>',
+    // This is unsupported because the OID is not recognized.
+    '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.
+    'othername:<unsupported>',
+    hasOpenSSL3 ?
+      'othername:" SRVName::abc\\u0000def"' :
+      '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/\\u000a' +
+            'OCSP - URI:http://evil.example.com/"',
+      legacy: {
+        'OCSP - URI': [
+          'http://good.example.com/\nOCSP - URI:http://evil.example.com/',
+        ],
+      },
+    },
+    {
+      text: 'CA Issuers - URI:"http://ca.example.com/\\u000a' +
+            'OCSP - URI:http://evil.example.com"\n' +
+            'OCSP - DNS:"good.example.com\\u000a' +
+            'OCSP - URI:http://ca.nodejs.org/ca.cert"',
+      legacy: {
+        'CA Issuers - URI': [
+          'http://ca.example.com/\nOCSP - URI:http://evil.example.com',
+        ],
+        'OCSP - DNS': [
+          'good.example.com\nOCSP - URI: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:<unsupported>\n' +
+            'OCSP - othername: SRVName::abc123',
+      legacy: {
+        'OCSP - othername': [
+          ' XmppAddr::good.example.com',
+          '<unsupported>',
+          ' SRVName::abc123',
+        ],
+      },
+    } : {
+      text: 'OCSP - othername:<unsupported>\n' +
+            'OCSP - othername:<unsupported>\n' +
+            'OCSP - othername:<unsupported>',
+      legacy: {
+        'OCSP - othername': [
+          '<unsupported>',
+          '<unsupported>',
+          '<unsupported>',
+        ],
+      },
+    },
+    hasOpenSSL3 ? {
+      text: 'OCSP - othername:" XmppAddr::good.example.com\\u0000abc123"',
+      legacy: {
+        'OCSP - othername': [
+          ' XmppAddr::good.example.com\0abc123',
+        ],
+      },
+    } : {
+      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}${hasOpenSSL3 ? '' : '\n'}`);
+
+    // Test that the certificate obtained by checkServerIdentity has the correct
+    // subjectaltname property.
+    const server = tls.createServer({
+      key: serverKey,
+      cert: pem,
+    }, common.mustCall((conn) => {
+      conn.destroy();
+      server.close();
+    })).listen(common.mustCall(() => {
+      const { port } = server.address();
+      tls.connect(port, {
+        ca: pem,
+        servername: 'example.com',
+        checkServerIdentity: (hostname, peerCert) => {
+          assert.strictEqual(hostname, 'example.com');
+          assert.deepStrictEqual(peerCert.infoAccess,
+                                 Object.assign(Object.create(null),
+                                               expected.legacy));
+        },
+      }, common.mustCall());
+    }));
+  }
+}
+
+// The internal parsing logic must match the JSON specification exactly.
+{
+  // This list is partially based on V8's own JSON tests.
+  const invalidJSON = [
+    '"\\a invalid escape"',
+    '"\\v invalid escape"',
+    '"\\\' invalid escape"',
+    '"\\x42 invalid escape"',
+    '"\\u202 invalid escape"',
+    '"\\012 invalid escape"',
+    '"Unterminated string',
+    '"Unterminated string\\"',
+    '"Unterminated string\\\\\\"',
+    '"\u0000 control character"',
+    '"\u001e control character"',
+    '"\u001f control character"',
+  ];
+
+  for (const invalidStringLiteral of invalidJSON) {
+    // Usually, checkServerIdentity returns an error upon verification failure.
+    // In this case, however, it should throw an error since this is not a
+    // verification error. Node.js itself will never produce invalid JSON string
+    // literals, so this can only happen when users construct invalid subject
+    // alternative name strings (that do not follow escaping rules).
+    assert.throws(() => {
+      tls.checkServerIdentity('example.com', {
+        subjectaltname: `DNS:${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();
+}