New Passphrase class for safer passphrase handling in memory

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/util/Passphrase.java

@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2015 Dominik Schürmann <dominik@dominikschuermann.de>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.sufficientlysecure.keychain.util;
+
+import android.os.Parcel;
+import android.os.Parcelable;
+import android.text.Editable;
+import android.widget.EditText;
+
+import org.sufficientlysecure.keychain.Constants;
+
+import java.util.Arrays;
+
+public class Passphrase implements Parcelable {
+    private char[] mPassphrase;
+
+    /**
+     * According to http://stackoverflow.com/a/15844273 EditText is not using String internally
+     * but char[]. Thus, we can get the char[] directly from it.
+     */
+    public Passphrase(Editable editable) {
+        int pl = editable.length();
+        mPassphrase = new char[pl];
+        editable.getChars(0, pl, mPassphrase, 0);
+        // TODO: clean up internal char[] of EditText after getting the passphrase?
+//        editText.getText().replace()
+        System.gc();
+    }
+
+    public Passphrase(EditText editText) {
+        this(editText.getText());
+    }
+
+    public Passphrase(String passphrase) {
+        mPassphrase = passphrase.toCharArray();
+    }
+
+    public Passphrase() {
+        setEmpty();
+    }
+
+    public char[] getCharArray() {
+        return mPassphrase;
+    }
+
+    public boolean isEmpty() {
+        return (mPassphrase.length == 0);
+    }
+
+    public void setEmpty() {
+        removeFromMemory();
+        mPassphrase = new char[0];
+    }
+
+    public void removeFromMemory() {
+        if (mPassphrase != null) {
+            Arrays.fill(mPassphrase, ' ');
+            System.gc();
+        }
+    }
+
+    @Override
+    public String toString() {
+        if (Constants.DEBUG) {
+            return "Passphrase{" +
+                    "mPassphrase=" + Arrays.toString(mPassphrase) +
+                    '}';
+        } else {
+            return "Passphrase: hidden";
+        }
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+
+        Passphrase that = (Passphrase) o;
+        if (!Arrays.equals(mPassphrase, that.mPassphrase)) {
+            return false;
+        }
+
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        return mPassphrase != null ? Arrays.hashCode(mPassphrase) : 0;
+    }
+
+    private Passphrase(Parcel source) {
+        mPassphrase = source.createCharArray();
+    }
+
+    public void writeToParcel(Parcel dest, int flags) {
+        dest.writeCharArray(mPassphrase);
+    }
+
+    public static final Creator<Passphrase> CREATOR = new Creator<Passphrase>() {
+        public Passphrase createFromParcel(final Parcel source) {
+            return new Passphrase(source);
+        }
+
+        public Passphrase[] newArray(final int size) {
+            return new Passphrase[size];
+        }
+    };
+
+    public int describeContents() {
+        return 0;
+    }
+}