diff --git a/crypto/x509/x509_test.cc b/crypto/x509/x509_test.cc
index 0e64018..d897ff5 100644
--- a/crypto/x509/x509_test.cc
+++ b/crypto/x509/x509_test.cc
@@ -1105,6 +1105,8 @@
   return stack;
 }
 
+static const time_t kReferenceTime = 1474934400 /* Sep 27th, 2016 */;
+
 static int Verify(X509 *leaf, const std::vector<X509 *> &roots,
                   const std::vector<X509 *> &intermediates,
                   const std::vector<X509_CRL *> &crls, unsigned long flags,
@@ -1147,7 +1149,7 @@
   if (param == nullptr) {
     return X509_V_ERR_UNSPECIFIED;
   }
-  X509_VERIFY_PARAM_set_time(param, 1474934400 /* Sep 27th, 2016 */);
+  X509_VERIFY_PARAM_set_time(param, kReferenceTime);
   X509_VERIFY_PARAM_set_depth(param, 16);
   if (configure_callback) {
     configure_callback(param);
@@ -1490,6 +1492,194 @@
                               {many_constraints.get()}, {}));
 }
 
+static bssl::UniquePtr<GENERAL_NAME> MakeGeneralName(int type,
+                                                     const std::string &value) {
+  if (type != GEN_EMAIL && type != GEN_DNS && type != GEN_URI) {
+    // This function only supports the IA5String types.
+    return nullptr;
+  }
+  bssl::UniquePtr<ASN1_IA5STRING> str(ASN1_IA5STRING_new());
+  bssl::UniquePtr<GENERAL_NAME> name(GENERAL_NAME_new());
+  if (!str || !name ||
+      !ASN1_STRING_set(str.get(), value.data(), value.size())) {
+    return nullptr;
+  }
+
+  name->type = type;
+  name->d.ia5 = str.release();
+  return name;
+}
+
+static bssl::UniquePtr<X509> MakeTestCert(const char *issuer,
+                                          const char *subject, EVP_PKEY *key) {
+  bssl::UniquePtr<X509> cert(X509_new());
+  if (!cert ||  //
+      !X509_set_version(cert.get(), X509_VERSION_3) ||
+      !X509_NAME_add_entry_by_txt(
+          X509_get_issuer_name(cert.get()), "CN", MBSTRING_UTF8,
+          reinterpret_cast<const uint8_t *>(issuer), -1, -1, 0) ||
+      !X509_NAME_add_entry_by_txt(
+          X509_get_subject_name(cert.get()), "CN", MBSTRING_UTF8,
+          reinterpret_cast<const uint8_t *>(subject), -1, -1, 0) ||
+      !X509_set_pubkey(cert.get(), key) ||
+      !ASN1_TIME_adj(X509_getm_notBefore(cert.get()), kReferenceTime, -1, 0) ||
+      !ASN1_TIME_adj(X509_getm_notAfter(cert.get()), kReferenceTime, 1, 0)) {
+    return nullptr;
+  }
+  return cert;
+}
+
+TEST(X509Test, NameConstraints) {
+  bssl::UniquePtr<EVP_PKEY> key = PrivateKeyFromPEM(kP256Key);
+  ASSERT_TRUE(key);
+
+  const struct {
+    int type;
+    std::string name;
+    std::string constraint;
+    int result;
+  } kTests[] = {
+      // Empty string matches everything.
+      {GEN_DNS, "foo.example.com", "", X509_V_OK},
+      // Name constraints match the entire subtree.
+      {GEN_DNS, "foo.example.com", "example.com", X509_V_OK},
+      {GEN_DNS, "foo.example.com", "EXAMPLE.COM", X509_V_OK},
+      {GEN_DNS, "foo.example.com", "xample.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_DNS, "foo.example.com", "unrelated.much.longer.name.example",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      // A leading dot means at least one component must be added.
+      {GEN_DNS, "foo.example.com", ".example.com", X509_V_OK},
+      {GEN_DNS, "foo.example.com", "foo.example.com", X509_V_OK},
+      {GEN_DNS, "foo.example.com", ".foo.example.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_DNS, "foo.example.com", ".xample.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_DNS, "foo.example.com", ".unrelated.much.longer.name.example",
+       X509_V_ERR_PERMITTED_VIOLATION},
+
+      // Names must be emails.
+      {GEN_EMAIL, "not-an-email.example", "not-an-email.example",
+       X509_V_ERR_UNSUPPORTED_NAME_SYNTAX},
+      // A leading dot matches all local names and all subdomains
+      {GEN_EMAIL, "foo@bar.example.com", ".example.com", X509_V_OK},
+      {GEN_EMAIL, "foo@bar.example.com", ".EXAMPLE.COM", X509_V_OK},
+      {GEN_EMAIL, "foo@bar.example.com", ".bar.example.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      // Without a leading dot, the host must match exactly.
+      {GEN_EMAIL, "foo@example.com", "example.com", X509_V_OK},
+      {GEN_EMAIL, "foo@example.com", "EXAMPLE.COM", X509_V_OK},
+      {GEN_EMAIL, "foo@bar.example.com", "example.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      // If the constraint specifies a mailbox, it specifies the whole thing.
+      // The halves are compared insensitively.
+      {GEN_EMAIL, "foo@example.com", "foo@example.com", X509_V_OK},
+      {GEN_EMAIL, "foo@example.com", "foo@EXAMPLE.COM", X509_V_OK},
+      {GEN_EMAIL, "foo@example.com", "FOO@example.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_EMAIL, "foo@example.com", "bar@example.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      // OpenSSL ignores a stray leading @.
+      {GEN_EMAIL, "foo@example.com", "@example.com", X509_V_OK},
+      {GEN_EMAIL, "foo@example.com", "@EXAMPLE.COM", X509_V_OK},
+      {GEN_EMAIL, "foo@bar.example.com", "@example.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+
+      // Basic syntax check.
+      {GEN_URI, "not-a-url", "not-a-url", X509_V_ERR_UNSUPPORTED_NAME_SYNTAX},
+      {GEN_URI, "foo:not-a-url", "not-a-url",
+       X509_V_ERR_UNSUPPORTED_NAME_SYNTAX},
+      {GEN_URI, "foo:/not-a-url", "not-a-url",
+       X509_V_ERR_UNSUPPORTED_NAME_SYNTAX},
+      {GEN_URI, "foo:///not-a-url", "not-a-url",
+       X509_V_ERR_UNSUPPORTED_NAME_SYNTAX},
+      {GEN_URI, "foo://:not-a-url", "not-a-url",
+       X509_V_ERR_UNSUPPORTED_NAME_SYNTAX},
+      {GEN_URI, "foo://", "not-a-url", X509_V_ERR_UNSUPPORTED_NAME_SYNTAX},
+      // Hosts are an exact match.
+      {GEN_URI, "foo://example.com", "example.com", X509_V_OK},
+      {GEN_URI, "foo://example.com:443", "example.com", X509_V_OK},
+      {GEN_URI, "foo://example.com/whatever", "example.com", X509_V_OK},
+      {GEN_URI, "foo://bar.example.com", "example.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://bar.example.com:443", "example.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://bar.example.com/whatever", "example.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://bar.example.com", "xample.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://bar.example.com:443", "xample.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://bar.example.com/whatever", "xample.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://example.com", "some-other-name.example",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://example.com:443", "some-other-name.example",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://example.com/whatever", "some-other-name.example",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      // A leading dot allows components to be added.
+      {GEN_URI, "foo://example.com", ".example.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://example.com:443", ".example.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://example.com/whatever", ".example.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://bar.example.com", ".example.com", X509_V_OK},
+      {GEN_URI, "foo://bar.example.com:443", ".example.com", X509_V_OK},
+      {GEN_URI, "foo://bar.example.com/whatever", ".example.com", X509_V_OK},
+      {GEN_URI, "foo://example.com", ".some-other-name.example",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://example.com:443", ".some-other-name.example",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://example.com/whatever", ".some-other-name.example",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://example.com", ".xample.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://example.com:443", ".xample.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+      {GEN_URI, "foo://example.com/whatever", ".xample.com",
+       X509_V_ERR_PERMITTED_VIOLATION},
+  };
+  for (const auto &t : kTests) {
+    SCOPED_TRACE(t.type);
+    SCOPED_TRACE(t.name);
+    SCOPED_TRACE(t.constraint);
+
+    bssl::UniquePtr<GENERAL_NAME> name = MakeGeneralName(t.type, t.name);
+    ASSERT_TRUE(name);
+    bssl::UniquePtr<GENERAL_NAMES> names(GENERAL_NAMES_new());
+    ASSERT_TRUE(names);
+    ASSERT_TRUE(bssl::PushToStack(names.get(), std::move(name)));
+
+    bssl::UniquePtr<NAME_CONSTRAINTS> nc(NAME_CONSTRAINTS_new());
+    ASSERT_TRUE(nc);
+    nc->permittedSubtrees = sk_GENERAL_SUBTREE_new_null();
+    ASSERT_TRUE(nc->permittedSubtrees);
+    bssl::UniquePtr<GENERAL_SUBTREE> subtree(GENERAL_SUBTREE_new());
+    ASSERT_TRUE(subtree);
+    GENERAL_NAME_free(subtree->base);
+    subtree->base = MakeGeneralName(t.type, t.constraint).release();
+    ASSERT_TRUE(subtree->base);
+    ASSERT_TRUE(bssl::PushToStack(nc->permittedSubtrees, std::move(subtree)));
+
+    bssl::UniquePtr<X509> root = MakeTestCert("Root", "Root", key.get());
+    ASSERT_TRUE(root);
+    ASSERT_TRUE(X509_add1_ext_i2d(root.get(), NID_name_constraints, nc.get(),
+                                  /*crit=*/1, /*flags=*/0));
+    ASSERT_TRUE(X509_sign(root.get(), key.get(), EVP_sha256()));
+
+    bssl::UniquePtr<X509> leaf = MakeTestCert("Root", "Leaf", key.get());
+    ASSERT_TRUE(leaf);
+    ASSERT_TRUE(X509_add1_ext_i2d(leaf.get(), NID_subject_alt_name, names.get(),
+                                  /*crit=*/0, /*flags=*/0));
+    ASSERT_TRUE(X509_sign(leaf.get(), key.get(), EVP_sha256()));
+
+    int ret = Verify(leaf.get(), {root.get()}, {}, {}, 0);
+    EXPECT_EQ(t.result, ret) << X509_verify_cert_error_string(ret);
+  }
+}
+
 TEST(X509Test, TestPSS) {
   bssl::UniquePtr<X509> cert(CertFromPEM(kExamplePSSCert));
   ASSERT_TRUE(cert);
diff --git a/include/openssl/x509v3.h b/include/openssl/x509v3.h
index 84fa108..46239d9 100644
--- a/include/openssl/x509v3.h
+++ b/include/openssl/x509v3.h
@@ -902,6 +902,7 @@
 BORINGSSL_MAKE_DELETER(BASIC_CONSTRAINTS, BASIC_CONSTRAINTS_free)
 BORINGSSL_MAKE_DELETER(DIST_POINT, DIST_POINT_free)
 BORINGSSL_MAKE_DELETER(GENERAL_NAME, GENERAL_NAME_free)
+BORINGSSL_MAKE_DELETER(GENERAL_SUBTREE, GENERAL_SUBTREE_free)
 BORINGSSL_MAKE_DELETER(NAME_CONSTRAINTS, NAME_CONSTRAINTS_free)
 BORINGSSL_MAKE_DELETER(POLICY_MAPPING, POLICY_MAPPING_free)
 BORINGSSL_MAKE_DELETER(POLICYINFO, POLICYINFO_free)