From df972e294d857cd86da15b92ef179948e04de97a Mon Sep 17 00:00:00 2001
From: akwizgran <akwizgran@users.sourceforge.net>
Date: Thu, 11 Aug 2011 17:15:36 +0100
Subject: [PATCH] Support for decrypting shared secrets and deriving
authentication and encryption keys from them (untested).
---
.../sf/briar/api/crypto/CryptoComponent.java | 6 +
.../sf/briar/api/crypto/SecretStorageKey.java | 18 +++
.../sf/briar/crypto/CryptoComponentImpl.java | 135 +++++++++++++-----
3 files changed, 126 insertions(+), 33 deletions(-)
create mode 100644 api/net/sf/briar/api/crypto/SecretStorageKey.java
diff --git a/api/net/sf/briar/api/crypto/CryptoComponent.java b/api/net/sf/briar/api/crypto/CryptoComponent.java
index 5cc912dc9c..7684c549b1 100644
--- a/api/net/sf/briar/api/crypto/CryptoComponent.java
+++ b/api/net/sf/briar/api/crypto/CryptoComponent.java
@@ -10,6 +10,12 @@ import javax.crypto.SecretKey;
public interface CryptoComponent {
+ SecretKey deriveMacKey(byte[] secret, boolean alice);
+
+ SecretKey derivePacketKey(byte[] secret, boolean alice);
+
+ SecretKey deriveTagKey(byte[] secret, boolean alice);
+
KeyPair generateKeyPair();
SecretKey generateSecretKey();
diff --git a/api/net/sf/briar/api/crypto/SecretStorageKey.java b/api/net/sf/briar/api/crypto/SecretStorageKey.java
new file mode 100644
index 0000000000..12fbffa940
--- /dev/null
+++ b/api/net/sf/briar/api/crypto/SecretStorageKey.java
@@ -0,0 +1,18 @@
+package net.sf.briar.api.crypto;
+
+import static java.lang.annotation.ElementType.PARAMETER;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+import com.google.inject.BindingAnnotation;
+
+/**
+ * Annotation for injecting the key that is used for encrypting and decrypting
+ * secrets stored in the database.
+ */
+@BindingAnnotation
+@Target({ PARAMETER })
+@Retention(RUNTIME)
+public @interface SecretStorageKey {}
diff --git a/components/net/sf/briar/crypto/CryptoComponentImpl.java b/components/net/sf/briar/crypto/CryptoComponentImpl.java
index 7e4d875250..c02a668a89 100644
--- a/components/net/sf/briar/crypto/CryptoComponentImpl.java
+++ b/components/net/sf/briar/crypto/CryptoComponentImpl.java
@@ -1,5 +1,8 @@
package net.sf.briar.crypto;
+import java.io.UnsupportedEncodingException;
+import java.security.InvalidAlgorithmParameterException;
+import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.MessageDigest;
@@ -7,50 +10,116 @@ import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.Security;
import java.security.Signature;
+import java.util.Arrays;
+import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
+import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.Mac;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
+import javax.crypto.spec.IvParameterSpec;
+import javax.crypto.spec.SecretKeySpec;
import net.sf.briar.api.crypto.CryptoComponent;
import net.sf.briar.api.crypto.KeyParser;
+import net.sf.briar.api.crypto.SecretStorageKey;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
+import com.google.inject.Inject;
+
class CryptoComponentImpl implements CryptoComponent {
private static final String PROVIDER = "BC";
private static final String DIGEST_ALGO = "SHA-256";
private static final String KEY_PAIR_ALGO = "ECDSA";
- private static final int KEY_PAIR_KEYSIZE = 256; // Bits
+ private static final int KEY_PAIR_BITS = 256;
+ private static final String SECRET_STORAGE_ALGO = "AES/CTR/NoPadding";
private static final String MAC_ALGO = "HMacSHA256";
private static final String PACKET_CIPHER_ALGO = "AES/CTR/NoPadding";
private static final String SECRET_KEY_ALGO = "AES";
- private static final int SECRET_KEY_KEYSIZE = 256; // Bits
+ private static final int SECRET_KEY_BITS = 256;
private static final String SIGNATURE_ALGO = "ECDSA";
private static final String TAG_CIPHER_ALGO = "AES/ECB/NoPadding";
+ private final SecretKey secretStorageKey;
private final KeyParser keyParser;
private final KeyPairGenerator keyPairGenerator;
private final KeyGenerator keyGenerator;
- CryptoComponentImpl() {
+ @Inject
+ CryptoComponentImpl(@SecretStorageKey SecretKey secretStorageKey) {
Security.addProvider(new BouncyCastleProvider());
+ this.secretStorageKey = secretStorageKey;
try {
keyParser = new KeyParserImpl(KEY_PAIR_ALGO, PROVIDER);
keyPairGenerator = KeyPairGenerator.getInstance(KEY_PAIR_ALGO,
PROVIDER);
- keyPairGenerator.initialize(KEY_PAIR_KEYSIZE);
+ keyPairGenerator.initialize(KEY_PAIR_BITS);
keyGenerator = KeyGenerator.getInstance(SECRET_KEY_ALGO,
PROVIDER);
- keyGenerator.init(SECRET_KEY_KEYSIZE);
- } catch(NoSuchAlgorithmException impossible) {
- throw new RuntimeException(impossible);
- } catch(NoSuchProviderException impossible) {
- throw new RuntimeException(impossible);
+ keyGenerator.init(SECRET_KEY_BITS);
+ } catch(NoSuchAlgorithmException e) {
+ throw new RuntimeException(e);
+ } catch(NoSuchProviderException e) {
+ throw new RuntimeException(e);
+ }
+ }
+
+ public SecretKey deriveMacKey(byte[] secret, boolean alice) {
+ if(alice) return deriveKey("MACA", secret);
+ else return deriveKey("MACB", secret);
+ }
+
+ private SecretKey deriveKey(String name, byte[] secret) {
+ MessageDigest digest = getMessageDigest();
+ try {
+ digest.update(name.getBytes("UTF-8"));
+ } catch(UnsupportedEncodingException e) {
+ throw new RuntimeException(e);
}
+ byte[] decrypted = decryptSharedSecret(secret);
+ digest.update(decrypted);
+ Arrays.fill(decrypted, (byte) 0);
+ return new SecretKeySpec(digest.digest(), SECRET_KEY_ALGO);
+ }
+
+ private byte[] decryptSharedSecret(byte[] secret) {
+ // The first 16 bytes of the stored secret are the IV
+ if(secret.length <= 16) throw new IllegalArgumentException();
+ IvParameterSpec iv = new IvParameterSpec(secret, 0, 16);
+ try {
+ // Decrypt and return the remainder of the stored secret
+ Cipher c = Cipher.getInstance(SECRET_STORAGE_ALGO, PROVIDER);
+ c.init(Cipher.DECRYPT_MODE, secretStorageKey, iv);
+ return c.doFinal(secret, 16, secret.length - 16);
+ } catch(BadPaddingException e) {
+ throw new RuntimeException(e);
+ } catch(IllegalBlockSizeException e) {
+ throw new RuntimeException(e);
+ } catch(InvalidAlgorithmParameterException e) {
+ throw new RuntimeException(e);
+ } catch(InvalidKeyException e) {
+ throw new RuntimeException(e);
+ } catch(NoSuchAlgorithmException e) {
+ throw new RuntimeException(e);
+ } catch(NoSuchPaddingException e) {
+ throw new RuntimeException(e);
+ } catch(NoSuchProviderException e) {
+ throw new RuntimeException(e);
+ }
+ }
+
+ public SecretKey derivePacketKey(byte[] secret, boolean alice) {
+ if(alice) return deriveKey("PKTA", secret);
+ else return deriveKey("PKTB", secret);
+ }
+
+ public SecretKey deriveTagKey(byte[] secret, boolean alice) {
+ if(alice) return deriveKey("TAGA", secret);
+ else return deriveKey("TAGB", secret);
}
public KeyPair generateKeyPair() {
@@ -68,54 +137,54 @@ class CryptoComponentImpl implements CryptoComponent {
public Mac getMac() {
try {
return Mac.getInstance(MAC_ALGO, PROVIDER);
- } catch(NoSuchAlgorithmException impossible) {
- throw new RuntimeException(impossible);
- } catch(NoSuchProviderException impossible) {
- throw new RuntimeException(impossible);
+ } catch(NoSuchAlgorithmException e) {
+ throw new RuntimeException(e);
+ } catch(NoSuchProviderException e) {
+ throw new RuntimeException(e);
}
}
public MessageDigest getMessageDigest() {
try {
return MessageDigest.getInstance(DIGEST_ALGO, PROVIDER);
- } catch(NoSuchAlgorithmException impossible) {
- throw new RuntimeException(impossible);
- } catch(NoSuchProviderException impossible) {
- throw new RuntimeException(impossible);
+ } catch(NoSuchAlgorithmException e) {
+ throw new RuntimeException(e);
+ } catch(NoSuchProviderException e) {
+ throw new RuntimeException(e);
}
}
public Cipher getPacketCipher() {
try {
return Cipher.getInstance(PACKET_CIPHER_ALGO, PROVIDER);
- } catch(NoSuchAlgorithmException impossible) {
- throw new RuntimeException(impossible);
- } catch(NoSuchPaddingException impossible) {
- throw new RuntimeException(impossible);
- } catch(NoSuchProviderException impossible) {
- throw new RuntimeException(impossible);
+ } catch(NoSuchAlgorithmException e) {
+ throw new RuntimeException(e);
+ } catch(NoSuchPaddingException e) {
+ throw new RuntimeException(e);
+ } catch(NoSuchProviderException e) {
+ throw new RuntimeException(e);
}
}
public Signature getSignature() {
try {
return Signature.getInstance(SIGNATURE_ALGO, PROVIDER);
- } catch(NoSuchAlgorithmException impossible) {
- throw new RuntimeException(impossible);
- } catch(NoSuchProviderException impossible) {
- throw new RuntimeException(impossible);
+ } catch(NoSuchAlgorithmException e) {
+ throw new RuntimeException(e);
+ } catch(NoSuchProviderException e) {
+ throw new RuntimeException(e);
}
}
public Cipher getTagCipher() {
try {
return Cipher.getInstance(TAG_CIPHER_ALGO, PROVIDER);
- } catch(NoSuchAlgorithmException impossible) {
- throw new RuntimeException(impossible);
- } catch(NoSuchPaddingException impossible) {
- throw new RuntimeException(impossible);
- } catch(NoSuchProviderException impossible) {
- throw new RuntimeException(impossible);
+ } catch(NoSuchAlgorithmException e) {
+ throw new RuntimeException(e);
+ } catch(NoSuchPaddingException e) {
+ throw new RuntimeException(e);
+ } catch(NoSuchProviderException e) {
+ throw new RuntimeException(e);
}
}
}
--
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