Refactoring

app/src/main/java/eu/faircode/email/ConnectionHelper.java

@@ -29,6 +29,7 @@ import android.net.NetworkInfo;
 import android.os.Build;
 import android.provider.Settings;
 import android.telephony.TelephonyManager;
+import android.text.TextUtils;
 
 import androidx.annotation.Nullable;
 import androidx.preference.PreferenceManager;
@@ -36,8 +37,14 @@ import androidx.preference.PreferenceManager;
 import com.sun.mail.iap.ConnectionException;
 import com.sun.mail.util.FolderClosedIOException;
 
+import org.bouncycastle.asn1.x509.GeneralName;
+
 import java.io.IOException;
+import java.security.cert.CertificateParsingException;
+import java.security.cert.X509Certificate;
+import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
@@ -455,4 +462,47 @@ public class ConnectionHelper {
         return Settings.Global.getInt(context.getContentResolver(),
                 Settings.Global.AIRPLANE_MODE_ON, 0) != 0;
     }
+
+    static List<String> getDnsNames(X509Certificate certificate) throws CertificateParsingException {
+        List<String> result = new ArrayList<>();
+
+        Collection<List<?>> altNames = certificate.getSubjectAlternativeNames();
+        if (altNames == null)
+            return result;
+
+        for (List altName : altNames)
+            if (altName.get(0).equals(GeneralName.dNSName))
+                result.add((String) altName.get(1));
+
+        return result;
+    }
+
+     static boolean matches(String server, List<String> names) {
+        for (String name : names)
+            if (matches(server, name)) {
+                Log.i("Trusted server=" + server + " name=" + name);
+                return true;
+            }
+        return false;
+    }
+
+    private static boolean matches(String server, String name) {
+        if (name.startsWith("*.")) {
+            // Wildcard certificate
+            String domain = name.substring(2);
+            if (TextUtils.isEmpty(domain))
+                return false;
+
+            int dot = server.indexOf(".");
+            if (dot < 0)
+                return false;
+
+            String cdomain = server.substring(dot + 1);
+            if (TextUtils.isEmpty(cdomain))
+                return false;
+
+            return domain.equalsIgnoreCase(cdomain);
+        } else
+            return server.equalsIgnoreCase(name);
+    }
 }

app/src/main/java/eu/faircode/email/EmailService.java

@@ -38,7 +38,6 @@ import com.sun.mail.util.SocketConnectException;
 
 import org.bouncycastle.asn1.DEROctetString;
 import org.bouncycastle.asn1.x509.Extension;
-import org.bouncycastle.asn1.x509.GeneralName;
 import org.bouncycastle.asn1.x509.SubjectKeyIdentifier;
 
 import java.io.ByteArrayOutputStream;
@@ -60,11 +59,9 @@ import java.security.Principal;
 import java.security.PrivateKey;
 import java.security.cert.CertificateEncodingException;
 import java.security.cert.CertificateException;
-import java.security.cert.CertificateParsingException;
 import java.security.cert.X509Certificate;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collection;
 import java.util.Collections;
 import java.util.Enumeration;
 import java.util.HashMap;
@@ -835,12 +832,9 @@ public class EmailService implements AutoCloseable {
                             }
 
                             // Check host name
-                            List<String> names = getDnsNames(certificate);
+                            List<String> names = ConnectionHelper.getDnsNames(certificate);
-                            for (String name : names)
+                            if (ConnectionHelper.matches(server, names))
-                                if (matches(server, name)) {
+                                return;
-                                    Log.i("Trusted server=" + server + " name=" + name);
-                                    return;
-                                }
 
                             String error = server + " not in certificate: " + TextUtils.join(",", names);
                             Log.i(error);
@@ -970,40 +964,6 @@ public class EmailService implements AutoCloseable {
             return factory.getSupportedCipherSuites();
         }
 
-        private static boolean matches(String server, String name) {
-            if (name.startsWith("*.")) {
-                // Wildcard certificate
-                String domain = name.substring(2);
-                if (TextUtils.isEmpty(domain))
-                    return false;
-
-                int dot = server.indexOf(".");
-                if (dot < 0)
-                    return false;
-
-                String cdomain = server.substring(dot + 1);
-                if (TextUtils.isEmpty(cdomain))
-                    return false;
-
-                return domain.equalsIgnoreCase(cdomain);
-            } else
-                return server.equalsIgnoreCase(name);
-        }
-
-        private static List<String> getDnsNames(X509Certificate certificate) throws CertificateParsingException {
-            List<String> result = new ArrayList<>();
-
-            Collection<List<?>> altNames = certificate.getSubjectAlternativeNames();
-            if (altNames == null)
-                return result;
-
-            for (List altName : altNames)
-                if (altName.get(0).equals(GeneralName.dNSName))
-                    result.add((String) altName.get(1));
-
-            return result;
-        }
-
         private static boolean matches(X509Certificate certificate, @NonNull String trustedFingerprint) {
             // Get certificate fingerprint
             try {