Cherry pick fix for CVE-2021-0341 onto 4.9.x (#6741)

* Use generated certificates in unit tests (#6346)

* Use generated certificates in unit tests
* Strict to ascii lowercase implementation

Co-authored-by: Jesse Wilson <jwilson@squareup.com>

* More restrictive behaviour of OkHostnameVerifier (#6353)

* Test quirks of HostnameVerifier.
* Restrict successful results to ascii input.

Co-authored-by: Jesse Wilson <jwilson@squareup.com>

okhttp/src/main/kotlin/okhttp3/internal/tls/OkHostnameVerifier.kt

@@ -16,14 +16,15 @@
  */
 package okhttp3.internal.tls
 
+import okhttp3.internal.canParseAsIpAddress
+import okhttp3.internal.toCanonicalHost
+import okio.utf8Size
 import java.security.cert.CertificateParsingException
 import java.security.cert.X509Certificate
 import java.util.Locale
 import javax.net.ssl.HostnameVerifier
 import javax.net.ssl.SSLException
 import javax.net.ssl.SSLSession
-import okhttp3.internal.canParseAsIpAddress
-import okhttp3.internal.toCanonicalHost
 
 /**
  * A HostnameVerifier consistent with [RFC 2818][rfc_2818].
@@ -36,11 +37,16 @@ object OkHostnameVerifier : HostnameVerifier {
   private const val ALT_IPA_NAME = 7
 
   override fun verify(host: String, session: SSLSession): Boolean {
-    return try {
-      verify(host, session.peerCertificates[0] as X509Certificate)
-    } catch (_: SSLException) {
+    return if (!host.isAscii()) {
       false
+    } else {
+      try {
+        verify(host, session.peerCertificates[0] as X509Certificate)
+      } catch (_: SSLException) {
+        false
+      }
     }
+
   }
 
   fun verify(host: String, certificate: X509Certificate): Boolean {
@@ -61,12 +67,27 @@ object OkHostnameVerifier : HostnameVerifier {
 
   /** Returns true if [certificate] matches [hostname]. */
   private fun verifyHostname(hostname: String, certificate: X509Certificate): Boolean {
-    val hostname = hostname.toLowerCase(Locale.US)
+    val hostname = hostname.asciiToLowercase()
     return getSubjectAltNames(certificate, ALT_DNS_NAME).any {
       verifyHostname(hostname, it)
     }
   }
 
+  /**
+   * This is like [toLowerCase] except that it does nothing if this contains any non-ASCII
+   * characters. We want to avoid lower casing special chars like U+212A (Kelvin symbol) because
+   * they can return ASCII characters that match real hostnames.
+   */
+  private fun String.asciiToLowercase(): String {
+    return when {
+      isAscii() -> toLowerCase(Locale.US) // This is an ASCII string.
+      else -> this
+    }
+  }
+
+  /** Returns true if the [String] is ASCII encoded (0-127). */
+  private fun String.isAscii() = length == utf8Size().toInt()
+
   /**
    * Returns true if [hostname] matches the domain name [pattern].
    *
@@ -108,7 +129,7 @@ object OkHostnameVerifier : HostnameVerifier {
     }
     // Hostname and pattern are now absolute domain names.
 
-    pattern = pattern.toLowerCase(Locale.US)
+    pattern = pattern.asciiToLowercase()
     // Hostname and pattern are now in lower case -- domain names are case-insensitive.
 
     if ("*" !in pattern) {

okhttp/src/test/java/okhttp3/HttpUrlTest.java

@@ -1773,6 +1773,17 @@ public void unparseableTopPrivateDomain() {
     assertInvalid("http://../", "Invalid URL host: \"..\"");
   }
 
+  @Test
+  public void hostnameTelephone() throws Exception {
+    // https://www.gosecure.net/blog/2020/10/27/weakness-in-java-tls-host-verification/
+
+    // Map the single character telephone symbol (℡) to the string "tel".
+    assertThat(parse("http://\u2121").host()).isEqualTo("tel");
+
+    // Map the Kelvin symbol (K) to the string "k".
+    assertThat(parse("http://\u212A").host()).isEqualTo("k");
+  }
+
   private void assertInvalid(String string, String exceptionMessage) {
     if (useGet) {
       try {

okhttp/src/test/java/okhttp3/internal/tls/HostnameVerifierTest.java

@@ -19,13 +19,17 @@
 
 import java.io.ByteArrayInputStream;
 import java.security.cert.CertificateFactory;
+import java.security.cert.CertificateParsingException;
 import java.security.cert.X509Certificate;
+import java.util.stream.Stream;
 import javax.net.ssl.HostnameVerifier;
 import javax.net.ssl.SSLSession;
 import javax.security.auth.x500.X500Principal;
 import okhttp3.FakeSSLSession;
+import okhttp3.OkHttpClient;
 import okhttp3.internal.Util;
-import org.junit.Ignore;
+import okhttp3.tls.HeldCertificate;
+import okhttp3.tls.internal.TlsUtil;
 import org.junit.Test;
 
 import static java.nio.charset.StandardCharsets.UTF_8;
@@ -36,9 +40,9 @@
  * from the Apache HTTP Client test suite.
  */
 public final class HostnameVerifierTest {
-  private HostnameVerifier verifier = OkHostnameVerifier.INSTANCE;
+  private OkHostnameVerifier verifier = OkHostnameVerifier.INSTANCE;
 
-  @Test public void verify() throws Exception {
+  @Test public void verify() {
     FakeSSLSession session = new FakeSSLSession();
     assertThat(verifier.verify("localhost", session)).isFalse();
   }
@@ -148,7 +152,7 @@ public final class HostnameVerifierTest {
    * are parsed. Android fails to parse these, which means we fall back to the CN. The RI does parse
    * them, so the CN is unused.
    */
-  @Test @Ignore public void verifyNonAsciiSubjectAlt() throws Exception {
+  @Test public void verifyNonAsciiSubjectAlt() throws Exception {
     // CN=foo.com, subjectAlt=bar.com, subjectAlt=花子.co.jp
     // (hanako.co.jp in kanji)
     SSLSession session = session(""
@@ -178,16 +182,20 @@ public final class HostnameVerifierTest {
         + "sWIKHYrmhCIRshUNohGXv50m2o+1w9oWmQ6Dkq7lCjfXfUB4wIbggJjpyEtbNqBt\n"
         + "j4MC2x5rfsLKKqToKmNE7pFEgqwe8//Aar1b+Qj+\n"
         + "-----END CERTIFICATE-----\n");
-    assertThat(verifier.verify("foo.com", session)).isTrue();
+
+    X509Certificate peerCertificate = ((X509Certificate) session.getPeerCertificates()[0]);
+    assertThat(certificateSANs(peerCertificate)).containsExactly("bar.com", "������.co.jp");
+
+    assertThat(verifier.verify("foo.com", session)).isFalse();
     assertThat(verifier.verify("a.foo.com", session)).isFalse();
     // these checks test alternative subjects. The test data contains an
     // alternative subject starting with a japanese kanji character. This is
     // not supported by Android because the underlying implementation from
     // harmony follows the definition from rfc 1034 page 10 for alternative
     // subject names. This causes the code to drop all alternative subjects.
-    // assertTrue(verifier.verify("bar.com", session));
-    // assertFalse(verifier.verify("a.bar.com", session));
-    // assertFalse(verifier.verify("a.\u82b1\u5b50.co.jp", session));
+    assertThat(verifier.verify("bar.com", session)).isTrue();
+    assertThat(verifier.verify("a.bar.com", session)).isFalse();
+    assertThat(verifier.verify("a.\u82b1\u5b50.co.jp", session)).isFalse();
   }
 
   @Test public void verifySubjectAltOnly() throws Exception {
@@ -329,11 +337,11 @@ public final class HostnameVerifierTest {
   }
 
   /**
-   * Ignored due to incompatibilities between Android and Java on how non-ASCII subject alt names
-   * are parsed. Android fails to parse these, which means we fall back to the CN. The RI does parse
-   * them, so the CN is unused.
+   * Previously ignored due to incompatibilities between Android and Java on how non-ASCII subject
+   * alt names are parsed. Android fails to parse these, which means we fall back to the CN.
+   * The RI does parse them, so the CN is unused.
    */
-  @Test @Ignore public void testWilcardNonAsciiSubjectAlt() throws Exception {
+  @Test public void testWilcardNonAsciiSubjectAlt() throws Exception {
     // CN=*.foo.com, subjectAlt=*.bar.com, subjectAlt=*.花子.co.jp
     // (*.hanako.co.jp in kanji)
     SSLSession session = session(""
@@ -363,20 +371,24 @@ public final class HostnameVerifierTest {
         + "qFr0AIZKBlg6NZZFf/0dP9zcKhzSriW27bY0XfzA6GSiRDXrDjgXq6baRT6YwgIg\n"
         + "pgJsDbJtZfHnV1nd3M6zOtQPm1TIQpNmMMMd/DPrGcUQerD3\n"
         + "-----END CERTIFICATE-----\n");
+
+    X509Certificate peerCertificate = ((X509Certificate) session.getPeerCertificates()[0]);
+    assertThat(certificateSANs(peerCertificate)).containsExactly("*.bar.com", "*.������.co.jp");
+
     // try the foo.com variations
-    assertThat(verifier.verify("foo.com", session)).isTrue();
-    assertThat(verifier.verify("www.foo.com", session)).isTrue();
-    assertThat(verifier.verify("\u82b1\u5b50.foo.com", session)).isTrue();
+    assertThat(verifier.verify("foo.com", session)).isFalse();
+    assertThat(verifier.verify("www.foo.com", session)).isFalse();
+    assertThat(verifier.verify("\u82b1\u5b50.foo.com", session)).isFalse();
     assertThat(verifier.verify("a.b.foo.com", session)).isFalse();
     // these checks test alternative subjects. The test data contains an
     // alternative subject starting with a japanese kanji character. This is
     // not supported by Android because the underlying implementation from
     // harmony follows the definition from rfc 1034 page 10 for alternative
     // subject names. This causes the code to drop all alternative subjects.
-    // assertFalse(verifier.verify("bar.com", session));
-    // assertTrue(verifier.verify("www.bar.com", session));
-    // assertTrue(verifier.verify("\u82b1\u5b50.bar.com", session));
-    // assertTrue(verifier.verify("a.b.bar.com", session));
+    assertThat(verifier.verify("bar.com", session)).isFalse();
+    assertThat(verifier.verify("www.bar.com", session)).isTrue();
+    assertThat(verifier.verify("\u82b1\u5b50.bar.com", session)).isFalse();
+    assertThat(verifier.verify("a.b.bar.com", session)).isFalse();
   }
 
   @Test public void subjectAltUsesLocalDomainAndIp() throws Exception {
@@ -554,6 +566,143 @@ public final class HostnameVerifierTest {
     assertThat(verifier.verify("0:0:0:0:0:FFFF:C0A8:0101", session)).isTrue();
   }
 
+  @Test public void generatedCertificate() throws Exception {
+    HeldCertificate heldCertificate = new HeldCertificate.Builder()
+        .commonName("Foo Corp")
+        .addSubjectAlternativeName("foo.com")
+        .build();
+
+    SSLSession session = session(heldCertificate.certificatePem());
+    assertThat(verifier.verify("foo.com", session)).isTrue();
+    assertThat(verifier.verify("bar.com", session)).isFalse();
+  }
+
+  @Test public void specialKInHostname() throws Exception {
+    // https://github.com/apache/httpcomponents-client/commit/303e435d7949652ea77a6c50df1c548682476b6e
+    // https://www.gosecure.net/blog/2020/10/27/weakness-in-java-tls-host-verification/
+
+    HeldCertificate heldCertificate = new HeldCertificate.Builder()
+        .commonName("Foo Corp")
+        .addSubjectAlternativeName("k.com")
+        .addSubjectAlternativeName("tel.com")
+        .build();
+
+    SSLSession session = session(heldCertificate.certificatePem());
+    assertThat(verifier.verify("foo.com", session)).isFalse();
+    assertThat(verifier.verify("bar.com", session)).isFalse();
+    assertThat(verifier.verify("k.com", session)).isTrue();
+    assertThat(verifier.verify("K.com", session)).isTrue();
+
+    assertThat(verifier.verify("\u2121.com", session)).isFalse();
+    assertThat(verifier.verify("℡.com", session)).isFalse();
+
+    // These should ideally be false, but we know that hostname is usually already checked by us
+    assertThat(verifier.verify("\u212A.com", session)).isFalse();
+    // Kelvin character below
+    assertThat(verifier.verify("K.com", session)).isFalse();
+  }
+
+  @Test public void specialKInCert() throws Exception {
+    // https://github.com/apache/httpcomponents-client/commit/303e435d7949652ea77a6c50df1c548682476b6e
+    // https://www.gosecure.net/blog/2020/10/27/weakness-in-java-tls-host-verification/
+
+    HeldCertificate heldCertificate = new HeldCertificate.Builder()
+        .commonName("Foo Corp")
+        .addSubjectAlternativeName("\u2121.com")
+        .addSubjectAlternativeName("\u212A.com")
+        .build();
+
+    SSLSession session = session(heldCertificate.certificatePem());
+    assertThat(verifier.verify("foo.com", session)).isFalse();
+    assertThat(verifier.verify("bar.com", session)).isFalse();
+    assertThat(verifier.verify("k.com", session)).isFalse();
+    assertThat(verifier.verify("K.com", session)).isFalse();
+
+    assertThat(verifier.verify("tel.com", session)).isFalse();
+    assertThat(verifier.verify("k.com", session)).isFalse();
+  }
+
+  @Test public void specialKInExternalCert() throws Exception {
+    // $ cat ./cert.cnf
+    // [req]
+    // distinguished_name=distinguished_name
+    // req_extensions=req_extensions
+    // x509_extensions=x509_extensions
+    // [distinguished_name]
+    // [req_extensions]
+    // [x509_extensions]
+    // subjectAltName=DNS:℡.com,DNS:K.com
+    //
+    // $ openssl req -x509 -nodes -days 36500 -subj '/CN=foo.com' -config ./cert.cnf \
+    //     -newkey rsa:512 -out cert.pem
+    SSLSession session = session(""
+        + "-----BEGIN CERTIFICATE-----\n"
+        + "MIIBSDCB86ADAgECAhRLR4TGgXBegg0np90FZ1KPeWpDtjANBgkqhkiG9w0BAQsF\n"
+        + "ADASMRAwDgYDVQQDDAdmb28uY29tMCAXDTIwMTAyOTA2NTkwNVoYDzIxMjAxMDA1\n"
+        + "MDY1OTA1WjASMRAwDgYDVQQDDAdmb28uY29tMFwwDQYJKoZIhvcNAQEBBQADSwAw\n"
+        + "SAJBALQcTVW9aW++ClIV9/9iSzijsPvQGEu/FQOjIycSrSIheZyZmR8bluSNBq0C\n"
+        + "9fpalRKZb0S2tlCTi5WoX8d3K30CAwEAAaMfMB0wGwYDVR0RBBQwEoIH4oShLmNv\n"
+        + "bYIH4oSqLmNvbTANBgkqhkiG9w0BAQsFAANBAA1+/eDvSUGv78iEjNW+1w3OPAwt\n"
+        + "Ij1qLQ/YI8OogZPMk7YY46/ydWWp7UpD47zy/vKmm4pOc8Glc8MoDD6UADs=\n"
+        + "-----END CERTIFICATE-----\n");
+
+    X509Certificate peerCertificate = ((X509Certificate) session.getPeerCertificates()[0]);
+    assertThat(certificateSANs(peerCertificate)).containsExactly("���.com", "���.com");
+
+    assertThat(verifier.verify("tel.com", session)).isFalse();
+    assertThat(verifier.verify("k.com", session)).isFalse();
+
+    assertThat(verifier.verify("foo.com", session)).isFalse();
+    assertThat(verifier.verify("bar.com", session)).isFalse();
+    assertThat(verifier.verify("k.com", session)).isFalse();
+    assertThat(verifier.verify("K.com", session)).isFalse();
+  }
+
+  private Stream<String> certificateSANs(X509Certificate peerCertificate)
+      throws CertificateParsingException {
+    return peerCertificate.getSubjectAlternativeNames().stream().map(c -> (String) c.get(1));
+  }
+
+  @Test public void replacementCharacter() throws Exception {
+    // $ cat ./cert.cnf
+    // [req]
+    // distinguished_name=distinguished_name
+    // req_extensions=req_extensions
+    // x509_extensions=x509_extensions
+    // [distinguished_name]
+    // [req_extensions]
+    // [x509_extensions]
+    // subjectAltName=DNS:℡.com,DNS:K.com
+    //
+    // $ openssl req -x509 -nodes -days 36500 -subj '/CN=foo.com' -config ./cert.cnf \
+    //     -newkey rsa:512 -out cert.pem
+    SSLSession session = session(""
+        + "-----BEGIN CERTIFICATE-----\n"
+        + "MIIBSDCB86ADAgECAhRLR4TGgXBegg0np90FZ1KPeWpDtjANBgkqhkiG9w0BAQsF\n"
+        + "ADASMRAwDgYDVQQDDAdmb28uY29tMCAXDTIwMTAyOTA2NTkwNVoYDzIxMjAxMDA1\n"
+        + "MDY1OTA1WjASMRAwDgYDVQQDDAdmb28uY29tMFwwDQYJKoZIhvcNAQEBBQADSwAw\n"
+        + "SAJBALQcTVW9aW++ClIV9/9iSzijsPvQGEu/FQOjIycSrSIheZyZmR8bluSNBq0C\n"
+        + "9fpalRKZb0S2tlCTi5WoX8d3K30CAwEAAaMfMB0wGwYDVR0RBBQwEoIH4oShLmNv\n"
+        + "bYIH4oSqLmNvbTANBgkqhkiG9w0BAQsFAANBAA1+/eDvSUGv78iEjNW+1w3OPAwt\n"
+        + "Ij1qLQ/YI8OogZPMk7YY46/ydWWp7UpD47zy/vKmm4pOc8Glc8MoDD6UADs=\n"
+        + "-----END CERTIFICATE-----\n");
+
+    // Replacement characters are deliberate, from certificate loading.
+    assertThat(verifier.verify("���.com", session)).isFalse();
+    assertThat(verifier.verify("℡.com", session)).isFalse();
+  }
+
+  @Test
+  public void thatCatchesErrorsWithBadSession() {
+    HostnameVerifier localVerifier = new OkHttpClient().hostnameVerifier();
+
+    // Since this is public API, okhttp3.internal.tls.OkHostnameVerifier.verify is also
+    assertThat(verifier).isInstanceOf(OkHostnameVerifier.class);
+
+    SSLSession session = TlsUtil.localhost().sslContext().createSSLEngine().getSession();
+    assertThat(localVerifier.verify("\uD83D\uDCA9.com", session)).isFalse();
+  }
+
   @Test public void verifyAsIpAddress() {
     // IPv4
     assertThat(Util.canParseAsIpAddress("127.0.0.1")).isTrue();