Add curve25519-sha256@libssh.org exchange method

2 files changed, 74 insertions, 0 deletions

diff --git a/sshlib/src/main/java/com/trilead/ssh2/crypto/dh/Curve25519Exchange.java b/sshlib/src/main/java/com/trilead/ssh2/crypto/dh/Curve25519Exchange.java
new file mode 100644
index 0000000..d28393b
--- /dev/null
+++ b/sshlib/src/main/java/com/trilead/ssh2/crypto/dh/Curve25519Exchange.java
@@ -0,0 +1,71 @@
+package com.trilead.ssh2.crypto.dh;
+
+import djb.Curve25519;
+
+import java.io.IOException;
+import java.math.BigInteger;
+import java.security.SecureRandom;
+
+/**
+ * Created by Kenny Root on 1/23/16.
+ */
+public class Curve25519Exchange extends GenericDhExchange {
+	public static final String NAME = "curve25519-sha256@libssh.org";
+
+	private final byte[] clientPublic = new byte[Curve25519.KEY_SIZE];
+	private final byte[] clientPrivate = new byte[Curve25519.KEY_SIZE];
+	private final byte[] serverPublic = new byte[Curve25519.KEY_SIZE];
+
+	public Curve25519Exchange() {
+		super();
+	}
+
+	/*
+	 * Used to test known vectors.
+	 */
+	public Curve25519Exchange(byte[] secret) {
+		if (secret.length != Curve25519.KEY_SIZE) {
+			throw new AssertionError("secret must be key size");
+		}
+		System.arraycopy(secret, 0, clientPrivate, 0, secret.length);
+		Curve25519.keygen(clientPublic, null, clientPrivate);
+	}
+
+	@Override
+	public void init(String name) throws IOException {
+		if (!NAME.equals(name)) {
+			throw new IOException("Invalid name " + name);
+		}
+
+		SecureRandom sr = new SecureRandom();
+		sr.nextBytes(clientPrivate);
+		Curve25519.keygen(clientPublic, null, clientPrivate);
+	}
+
+	@Override
+	public byte[] getE() {
+		return clientPublic.clone();
+	}
+
+	@Override
+	protected byte[] getServerE() {
+		return serverPublic.clone();
+	}
+
+	@Override
+	public void setF(byte[] f) throws IOException {
+		if (f.length != serverPublic.length) {
+			throw new IOException("Server sent invalid key length " + f.length + " (expected " +
+					serverPublic.length + ")");
+		}
+		System.arraycopy(f, 0, serverPublic, 0, f.length);
+		byte[] sharedSecretBytes = new byte[Curve25519.KEY_SIZE];
+		Curve25519.curve(sharedSecretBytes, clientPrivate, serverPublic);
+		sharedSecret = new BigInteger(1, sharedSecretBytes);
+	}
+
+	@Override
+	public String getHashAlgo() {
+		return "SHA-256";
+	}
+}
diff --git a/sshlib/src/main/java/com/trilead/ssh2/crypto/dh/GenericDhExchange.java b/sshlib/src/main/java/com/trilead/ssh2/crypto/dh/GenericDhExchange.java
index 039ff75..1ad2554 100644
--- a/sshlib/src/main/java/com/trilead/ssh2/crypto/dh/GenericDhExchange.java
+++ b/sshlib/src/main/java/com/trilead/ssh2/crypto/dh/GenericDhExchange.java
@@ -28,6 +28,9 @@ public abstract class GenericDhExchange
 	}
 
 	public static GenericDhExchange getInstance(String algo) {
+		if (algo.startsWith("curve25519-sha256@libssh.org")) {
+			return new Curve25519Exchange();
+		}
 		if (algo.startsWith("ecdh-sha2-")) {
 			return new EcDhExchange();
 		} else {