Fix non-ASCII passwords

src/main/java/net/schmizz/sshj/common/Buffer.java

@@ -453,11 +453,14 @@ public class Buffer<T extends Buffer<T>> {
     public T putSensitiveString(char[] str) {
         if (str == null)
             return putString("");
-        putUInt32(str.length);
-        ensureCapacity(str.length);
-        for (char c : str)
-            data[wpos++] = (byte) c;
-        Arrays.fill(str, ' ');
+        // RFC 4252, Section 8 says: passwords should be encoded as UTF-8.
+        // RFC 4256, Section 3.4 says: keyboard-interactive information responses should be encoded as UTF-8.
+        byte[] utf8 = ByteArrayUtils.encodeSensitiveStringToUtf8(str);
+        putUInt32(utf8.length);
+        ensureCapacity(utf8.length);
+        for (byte c : utf8)
+            data[wpos++] = c;
+        Arrays.fill(utf8, (byte) 0);
         return (T) this;
     }
 

src/main/java/net/schmizz/sshj/common/ByteArrayUtils.java

@@ -15,6 +15,12 @@
  */
 package net.schmizz.sshj.common;
 
+import java.nio.ByteBuffer;
+import java.nio.CharBuffer;
+import java.nio.charset.Charset;
+import java.nio.charset.CharsetEncoder;
+import java.util.Arrays;
+
 /** Utility functions for byte arrays. */
 public class ByteArrayUtils {
 
@@ -124,4 +130,26 @@ public class ByteArrayUtils {
         }
         throw new IllegalArgumentException("Digit '" + c + "' out of bounds [0-9a-fA-F]");
     }
+
+    /**
+     * Converts a char-array to UTF-8 byte-array and then blanks out source array and all intermediate arrays.
+     * <p/>
+     * This is useful when a plaintext password needs to be encoded as UTF-8.
+     *
+     * @param str A not-null string as a character array.
+     *
+     * @return UTF-8 bytes of the string
+     */
+    public static byte[] encodeSensitiveStringToUtf8(char[] str) {
+        CharsetEncoder charsetEncoder = Charset.forName("UTF-8").newEncoder();
+        ByteBuffer utf8Buffer = ByteBuffer.allocate((int) (str.length * charsetEncoder.maxBytesPerChar()));
+        assert utf8Buffer.hasArray();
+        charsetEncoder.encode(CharBuffer.wrap(str), utf8Buffer, true);
+        Arrays.fill(str, ' ');
+
+        byte[] utf8Bytes = new byte[utf8Buffer.position()];
+        System.arraycopy(utf8Buffer.array(), 0, utf8Bytes, 0, utf8Bytes.length);
+        Arrays.fill(utf8Buffer.array(), (byte) 0);
+        return utf8Bytes;
+    }
 }

src/test/java/com/hierynomus/sshj/userauth/method/AuthKeyboardInteractiveTest.java

@@ -0,0 +1,98 @@
+/*
+ * Copyright (C)2009 - SSHJ Contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.hierynomus.sshj.userauth.method;
+
+import com.hierynomus.sshj.test.SshFixture;
+import net.schmizz.sshj.SSHClient;
+import net.schmizz.sshj.userauth.method.AuthKeyboardInteractive;
+import net.schmizz.sshj.userauth.method.ChallengeResponseProvider;
+import net.schmizz.sshj.userauth.password.Resource;
+import org.apache.sshd.client.auth.keyboard.UserAuthKeyboardInteractiveFactory;
+import org.apache.sshd.common.NamedFactory;
+import org.apache.sshd.server.auth.UserAuth;
+import org.apache.sshd.server.auth.keyboard.UserAuthKeyboardInteractive;
+import org.apache.sshd.server.auth.password.PasswordAuthenticator;
+import org.apache.sshd.server.session.ServerSession;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+
+public class AuthKeyboardInteractiveTest {
+    @Rule
+    public SshFixture fixture = new SshFixture(false);
+
+    @Before
+    public void setKeyboardInteractiveAuthenticator() throws IOException {
+        fixture.getServer().setUserAuthFactories(Collections.<NamedFactory<UserAuth>>singletonList(new NamedFactory<UserAuth>() {
+            @Override
+            public String getName() {
+                return UserAuthKeyboardInteractiveFactory.NAME;
+            }
+
+            @Override
+            public UserAuth get() {
+                return new UserAuthKeyboardInteractive();
+            }
+
+            @Override
+            public UserAuth create() {
+                return get();
+            }
+        }));
+        fixture.getServer().setPasswordAuthenticator(new PasswordAuthenticator() {
+            @Override
+            public boolean authenticate(String username, String password, ServerSession session) {
+                return password.equals(username);
+            }
+        });
+        fixture.getServer().start();
+    }
+
+    @Test
+    public void shouldEncodePasswordsAsUtf8() throws IOException {
+        SSHClient sshClient = fixture.setupConnectedDefaultClient();
+        final String userAndPassword = "øæå";
+        sshClient.auth(userAndPassword, new AuthKeyboardInteractive(new ChallengeResponseProvider() {
+            @Override
+            public List<String> getSubmethods() {
+                return new ArrayList<String>();
+            }
+
+            @Override
+            public void init(Resource resource, String name, String instruction) {
+                // nothing
+            }
+
+            @Override
+            public char[] getResponse(String prompt, boolean echo) {
+                return userAndPassword.toCharArray();
+            }
+
+            @Override
+            public boolean shouldRetry() {
+                return false;
+            }
+        }));
+        assertThat("Should have been authenticated", sshClient.isAuthenticated());
+    }
+}

src/test/java/com/hierynomus/sshj/userauth/method/AuthPasswordTest.java

@@ -144,6 +144,14 @@ public class AuthPasswordTest {
         assertThat("Should have been authenticated", sshClient.isAuthenticated());
     }
 
+    @Test
+    public void shouldEncodePasswordsAsUtf8() throws IOException {
+        SSHClient sshClient = fixture.setupConnectedDefaultClient();
+        String userAndPassword = "øæå";
+        sshClient.authPassword(userAndPassword, userAndPassword);
+        assertThat("Should have been authenticated", sshClient.isAuthenticated());
+    }
+
     private static class StaticPasswordUpdateProvider implements PasswordUpdateProvider {
         private Stack<String> newPasswords = new Stack<String>();