diff options
Diffstat (limited to '')
5 files changed, 196 insertions, 0 deletions
diff --git a/src/main/java/org/whispersystems/libaxolotl/kdf/DerivedMessageSecrets.java b/src/main/java/org/whispersystems/libaxolotl/kdf/DerivedMessageSecrets.java new file mode 100644 index 00000000..b3f54fb8 --- /dev/null +++ b/src/main/java/org/whispersystems/libaxolotl/kdf/DerivedMessageSecrets.java @@ -0,0 +1,61 @@ +/** + * Copyright (C) 2014 Open Whisper Systems + * + * 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.whispersystems.libaxolotl.kdf; + +import org.whispersystems.libaxolotl.util.ByteUtil; + +import java.text.ParseException; + +import javax.crypto.spec.IvParameterSpec; +import javax.crypto.spec.SecretKeySpec; + +public class DerivedMessageSecrets { + + public static final int SIZE = 80; + private static final int CIPHER_KEY_LENGTH = 32; + private static final int MAC_KEY_LENGTH = 32; + private static final int IV_LENGTH = 16; + + private final SecretKeySpec cipherKey; + private final SecretKeySpec macKey; + private final IvParameterSpec iv; + + public DerivedMessageSecrets(byte[] okm) { + try { + byte[][] keys = ByteUtil.split(okm, CIPHER_KEY_LENGTH, MAC_KEY_LENGTH, IV_LENGTH); + + this.cipherKey = new SecretKeySpec(keys[0], "AES"); + this.macKey = new SecretKeySpec(keys[1], "HmacSHA256"); + this.iv = new IvParameterSpec(keys[2]); + } catch (ParseException e) { + throw new AssertionError(e); + } + } + + public SecretKeySpec getCipherKey() { + return cipherKey; + } + + public SecretKeySpec getMacKey() { + return macKey; + } + + public IvParameterSpec getIv() { + return iv; + } +} diff --git a/src/main/java/org/whispersystems/libaxolotl/kdf/DerivedRootSecrets.java b/src/main/java/org/whispersystems/libaxolotl/kdf/DerivedRootSecrets.java new file mode 100644 index 00000000..82cc541d --- /dev/null +++ b/src/main/java/org/whispersystems/libaxolotl/kdf/DerivedRootSecrets.java @@ -0,0 +1,26 @@ +package org.whispersystems.libaxolotl.kdf; + +import org.whispersystems.libaxolotl.util.ByteUtil; + +public class DerivedRootSecrets { + + public static final int SIZE = 64; + + private final byte[] rootKey; + private final byte[] chainKey; + + public DerivedRootSecrets(byte[] okm) { + byte[][] keys = ByteUtil.split(okm, 32, 32); + this.rootKey = keys[0]; + this.chainKey = keys[1]; + } + + public byte[] getRootKey() { + return rootKey; + } + + public byte[] getChainKey() { + return chainKey; + } + +} diff --git a/src/main/java/org/whispersystems/libaxolotl/kdf/HKDF.java b/src/main/java/org/whispersystems/libaxolotl/kdf/HKDF.java new file mode 100644 index 00000000..d190822d --- /dev/null +++ b/src/main/java/org/whispersystems/libaxolotl/kdf/HKDF.java @@ -0,0 +1,93 @@ +/** + * Copyright (C) 2013 Open Whisper Systems + * + * 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.whispersystems.libaxolotl.kdf; + +import java.io.ByteArrayOutputStream; +import java.security.InvalidKeyException; +import java.security.NoSuchAlgorithmException; + +import javax.crypto.Mac; +import javax.crypto.spec.SecretKeySpec; + +public abstract class HKDF { + + private static final int HASH_OUTPUT_SIZE = 32; + + public static HKDF createFor(int messageVersion) { + switch (messageVersion) { + case 2: return new HKDFv2(); + case 3: return new HKDFv3(); + default: throw new AssertionError("Unknown version: " + messageVersion); + } + } + + public byte[] deriveSecrets(byte[] inputKeyMaterial, byte[] info, int outputLength) { + byte[] salt = new byte[HASH_OUTPUT_SIZE]; + return deriveSecrets(inputKeyMaterial, salt, info, outputLength); + } + + public byte[] deriveSecrets(byte[] inputKeyMaterial, byte[] salt, byte[] info, int outputLength) { + byte[] prk = extract(salt, inputKeyMaterial); + return expand(prk, info, outputLength); + } + + private byte[] extract(byte[] salt, byte[] inputKeyMaterial) { + try { + Mac mac = Mac.getInstance("HmacSHA256"); + mac.init(new SecretKeySpec(salt, "HmacSHA256")); + return mac.doFinal(inputKeyMaterial); + } catch (NoSuchAlgorithmException | InvalidKeyException e) { + throw new AssertionError(e); + } + } + + private byte[] expand(byte[] prk, byte[] info, int outputSize) { + try { + int iterations = (int) Math.ceil((double) outputSize / (double) HASH_OUTPUT_SIZE); + byte[] mixin = new byte[0]; + ByteArrayOutputStream results = new ByteArrayOutputStream(); + int remainingBytes = outputSize; + + for (int i= getIterationStartOffset();i<iterations + getIterationStartOffset();i++) { + Mac mac = Mac.getInstance("HmacSHA256"); + mac.init(new SecretKeySpec(prk, "HmacSHA256")); + + mac.update(mixin); + if (info != null) { + mac.update(info); + } + mac.update((byte)i); + + byte[] stepResult = mac.doFinal(); + int stepSize = Math.min(remainingBytes, stepResult.length); + + results.write(stepResult, 0, stepSize); + + mixin = stepResult; + remainingBytes -= stepSize; + } + + return results.toByteArray(); + } catch (NoSuchAlgorithmException | InvalidKeyException e) { + throw new AssertionError(e); + } + } + + protected abstract int getIterationStartOffset(); + +} diff --git a/src/main/java/org/whispersystems/libaxolotl/kdf/HKDFv2.java b/src/main/java/org/whispersystems/libaxolotl/kdf/HKDFv2.java new file mode 100644 index 00000000..86e4bf5f --- /dev/null +++ b/src/main/java/org/whispersystems/libaxolotl/kdf/HKDFv2.java @@ -0,0 +1,8 @@ +package org.whispersystems.libaxolotl.kdf; + +public class HKDFv2 extends HKDF { + @Override + protected int getIterationStartOffset() { + return 0; + } +} diff --git a/src/main/java/org/whispersystems/libaxolotl/kdf/HKDFv3.java b/src/main/java/org/whispersystems/libaxolotl/kdf/HKDFv3.java new file mode 100644 index 00000000..a1934c90 --- /dev/null +++ b/src/main/java/org/whispersystems/libaxolotl/kdf/HKDFv3.java @@ -0,0 +1,8 @@ +package org.whispersystems.libaxolotl.kdf; + +public class HKDFv3 extends HKDF { + @Override + protected int getIterationStartOffset() { + return 1; + } +} |