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/*
* Copyright (C) 2015 Dominik Schürmann <dominik@dominikschuermann.de>
* Copyright (C) 2016 Vincent Breitmoser <look@my.amazin.horse>
*
* 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.bouncycastle.bcpg.S2K;
import org.sufficientlysecure.keychain.Constants;
import org.sufficientlysecure.keychain.pgp.ComparableS2K;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map.Entry;
/**
* This class wraps a char[] array that is overwritten before the object is freed, to avoid
* keeping passphrases in memory as much as possible.
*
* In addition to the raw passphrases, this class can cache the session key output of an applied
* S2K algorithm for a given set of S2K parameters. Since S2K operations are very expensive, this
* mechanism should be used to cache session keys whenever possible.
*
* See also:
* <p/>
* http://docs.oracle.com/javase/6/docs/technotes/guides/security/crypto/CryptoSpec.html#PBEEx
* https://github.com/c-a-m/passfault/blob/master/core/src/main/java/org/owasp/passfault/SecureString.java
* http://stackoverflow.com/q/8881291
* http://stackoverflow.com/a/15844273
*/
public class Passphrase implements Parcelable {
private char[] mPassphrase;
private HashMap<ComparableS2K, byte[]> mCachedSessionKeys;
/**
* 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()
}
public Passphrase(EditText editText) {
this(editText.getText());
}
public Passphrase(char[] passphrase) {
mPassphrase = passphrase;
}
public Passphrase(String passphrase) {
mPassphrase = passphrase.toCharArray();
}
/**
* Creates a passphrase object with an empty ("") passphrase
*/
public Passphrase() {
setEmpty();
}
public char[] getCharArray() {
return mPassphrase;
}
public void setEmpty() {
removeFromMemory();
mPassphrase = new char[0];
}
public boolean isEmpty() {
return (length() == 0);
}
public int length() {
return mPassphrase.length;
}
/** @return A cached session key, or null if none exists for the given parameters. */
public byte[] getCachedSessionKeyForParameters(int keyEncryptionAlgorithm, S2K s2k) {
if (mCachedSessionKeys == null) {
return null;
}
return mCachedSessionKeys.get(new ComparableS2K(keyEncryptionAlgorithm, s2k));
}
/** Adds a session key for a set of s2k parameters to this Passphrase object's
* cache. The caller should make sure that the supplied session key is the result
* of an S2K operation applied to exactly the passphrase stored by this object
* with the given parameters.
*/
public void addCachedSessionKeyForParameters(int keyEncryptionAlgorithm, S2K s2k, byte[] sessionKey) {
if (mCachedSessionKeys == null) {
mCachedSessionKeys = new HashMap<>();
}
mCachedSessionKeys.put(new ComparableS2K(keyEncryptionAlgorithm, s2k), sessionKey);
}
/**
* Manually clear the underlying array holding the characters
*/
public void removeFromMemory() {
if (mPassphrase != null) {
Arrays.fill(mPassphrase, ' ');
}
if (mCachedSessionKeys == null) {
return;
}
for (byte[] cachedSessionKey : mCachedSessionKeys.values()) {
Arrays.fill(cachedSessionKey, (byte) 0);
}
}
@Override
public void finalize() throws Throwable {
removeFromMemory();
super.finalize();
}
@Override
public String toString() {
if (Constants.DEBUG) {
return "Passphrase{" +
"mPassphrase=" + Arrays.toString(mPassphrase) +
'}';
} else {
return "Passphrase: hidden";
}
}
/**
* Creates a new String from the char[]. This is considered unsafe!
*/
public String toStringUnsafe() {
return new String(mPassphrase);
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
Passphrase that = (Passphrase) o;
return Arrays.equals(mPassphrase, that.mPassphrase);
}
@Override
public int hashCode() {
return mPassphrase != null ? Arrays.hashCode(mPassphrase) : 0;
}
private Passphrase(Parcel source) {
mPassphrase = source.createCharArray();
int size = source.readInt();
if (size == 0) {
return;
}
mCachedSessionKeys = new HashMap<>(size);
for (int i = 0; i < size; i++) {
ComparableS2K cachedS2K = source.readParcelable(getClass().getClassLoader());
byte[] cachedSessionKey = source.createByteArray();
mCachedSessionKeys.put(cachedS2K, cachedSessionKey);
}
}
public void writeToParcel(Parcel dest, int flags) {
dest.writeCharArray(mPassphrase);
if (mCachedSessionKeys == null || mCachedSessionKeys.isEmpty()) {
dest.writeInt(0);
return;
}
dest.writeInt(mCachedSessionKeys.size());
for (Entry<ComparableS2K,byte[]> entry : mCachedSessionKeys.entrySet()) {
dest.writeParcelable(entry.getKey(), 0);
dest.writeByteArray(entry.getValue());
}
}
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;
}
}
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