package ch.ethz.ssh2.signature;
import java.io.IOException;
import java.math.BigInteger;
import ch.ethz.ssh2.crypto.SimpleDERReader;
import ch.ethz.ssh2.crypto.digest.SHA1;
import ch.ethz.ssh2.log.Logger;
import ch.ethz.ssh2.packets.TypesReader;
import ch.ethz.ssh2.packets.TypesWriter;
/**
* RSASHA1Verify.
*
* @author Christian Plattner, plattner@inf.ethz.ch
* @version $Id: RSASHA1Verify.java,v 1.4 2005/12/07 10:25:49 cplattne Exp $
*/
public class RSASHA1Verify
{
private static final Logger log = Logger.getLogger(RSASHA1Verify.class);
public static RSAPublicKey decodeSSHRSAPublicKey(byte[] key) throws IOException
{
TypesReader tr = new TypesReader(key);
String key_format = tr.readString();
if (key_format.equals("ssh-rsa") == false)
throw new IllegalArgumentException("This is not a ssh-rsa public key");
BigInteger e = tr.readMPINT();
BigInteger n = tr.readMPINT();
if (tr.remain() != 0)
throw new IOException("Padding in RSA public key!");
return new RSAPublicKey(e, n);
}
public static byte[] encodeSSHRSAPublicKey(RSAPublicKey pk) throws IOException
{
TypesWriter tw = new TypesWriter();
tw.writeString("ssh-rsa");
tw.writeMPInt(pk.getE());
tw.writeMPInt(pk.getN());
return tw.getBytes();
}
public static RSASignature decodeSSHRSASignature(byte[] sig) throws IOException
{
TypesReader tr = new TypesReader(sig);
String sig_format = tr.readString();
if (sig_format.equals("ssh-rsa") == false)
throw new IOException("Peer sent wrong signature format");
/* S is NOT an MPINT. "The value for 'rsa_signature_blob' is encoded as a string
* containing s (which is an integer, without lengths or padding, unsigned and in
* network byte order)." See also below.
*/
byte[] s = tr.readByteString();
if (s.length == 0)
throw new IOException("Error in RSA signature, S is empty.");
if (log.isEnabled())
{
log.log(80, "Decoding ssh-rsa signature string (length: " + s.length + ")");
}
if (tr.remain() != 0)
throw new IOException("Padding in RSA signature!");
return new RSASignature(new BigInteger(1, s));
}
public static byte[] encodeSSHRSASignature(RSASignature sig) throws IOException
{
TypesWriter tw = new TypesWriter();
tw.writeString("ssh-rsa");
/* S is NOT an MPINT. "The value for 'rsa_signature_blob' is encoded as a string
* containing s (which is an integer, without lengths or padding, unsigned and in
* network byte order)."
*/
byte[] s = sig.getS().toByteArray();
/* Remove first zero sign byte, if present */
if ((s.length > 1) && (s[0] == 0x00))
tw.writeString(s, 1, s.length - 1);
else
tw.writeString(s, 0, s.length);
return tw.getBytes();
}
public static RSASignature generateSignature(byte[] message, RSAPrivateKey pk) throws IOException
{
SHA1 md = new SHA1();
md.update(message);
byte[] sha_message = new byte[md.getDigestLength()];
md.digest(sha_message);
byte[] der_header = new byte[] { 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00,
0x04, 0x14 };
int rsa_block_len = (pk.getN().bitLength() + 7) / 8;
int num_pad = rsa_block_len - (2 + der_header.length + sha_message.length) - 1;
if (num_pad < 8)
throw new IOException("Cannot sign with RSA, message too long");
byte[] sig = new byte[der_header.length + sha_message.length + 2 + num_pad];
sig[0] = 0x01;
for (int i = 0; i < num_pad; i++)
{
sig[i + 1] = (byte) 0xff;
}
sig[num_pad + 1] = 0x00;
System.arraycopy(der_header, 0, sig, 2 + num_pad, der_header.length);
System.arraycopy(sha_message, 0, sig, 2 + num_pad + der_header.length, sha_message.length);
BigInteger m = new BigInteger(1, sig);
BigInteger s = m.modPow(pk.getD(), pk.getN());
return new RSASignature(s);
}
public static boolean verifySignature(byte[] message, RSASignature ds, RSAPublicKey dpk) throws IOException
{
SHA1 md = new SHA1();
md.update(message);
byte[] sha_message = new byte[md.getDigestLength()];
md.digest(sha_message);
BigInteger n = dpk.getN();
BigInteger e = dpk.getE();
BigInteger s = ds.getS();
if (n.compareTo(s) <= 0)
{
log.log(20, "ssh-rsa signature: n.compareTo(s) <= 0");
return false;
}
int rsa_block_len = (n.bitLength() + 7) / 8;
/* And now the show begins */
if (rsa_block_len < 1)
{
log.log(20, "ssh-rsa signature: rsa_block_len < 1");
return false;
}
byte[] v = s.modPow(e, n).toByteArray();
int startpos = 0;
if ((v.length > 0) && (v[0] == 0x00))
startpos++;
if ((v.length - startpos) != (rsa_block_len - 1))
{
log.log(20, "ssh-rsa signature: (v.length - startpos) != (rsa_block_len - 1)");
return false;
}
if (v[startpos] != 0x01)
{
log.log(20, "ssh-rsa signature: v[startpos] != 0x01");
return false;
}
int pos = startpos + 1;
while (true)
{
if (pos >= v.length)
{
log.log(20, "ssh-rsa signature: pos >= v.length");
return false;
}
if (v[pos] == 0x00)
break;
if (v[pos] != (byte) 0xff)
{
log.log(20, "ssh-rsa signature: v[pos] != (byte) 0xff");
return false;
}
pos++;
}
int num_pad = pos - (startpos + 1);
if (num_pad < 8)
{
log.log(20, "ssh-rsa signature: num_pad < 8");
return false;
}
pos++;
if (pos >= v.length)
{
log.log(20, "ssh-rsa signature: pos >= v.length");
return false;
}
SimpleDERReader dr = new SimpleDERReader(v, pos, v.length - pos);
byte[] seq = dr.readSequenceAsByteArray();
if (dr.available() != 0)
{
log.log(20, "ssh-rsa signature: dr.available() != 0");
return false;
}
dr.resetInput(seq);
/* Read digestAlgorithm */
byte digestAlgorithm[] = dr.readSequenceAsByteArray();
/* Inspired by RFC 3347, however, ignoring the comment regarding old BER based implementations */
if ((digestAlgorithm.length < 8) || (digestAlgorithm.length > 9))
{
log.log(20, "ssh-rsa signature: (digestAlgorithm.length < 8) || (digestAlgorithm.length > 9)");
return false;
}
byte[] digestAlgorithm_sha1 = new byte[] { 0x06, 0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00 };
for (int i = 0; i < digestAlgorithm.length; i++)
{
if (digestAlgorithm[i] != digestAlgorithm_sha1[i])
{
log.log(20, "ssh-rsa signature: digestAlgorithm[i] != digestAlgorithm_sha1[i]");
return false;
}
}
byte[] digest = dr.readOctetString();
if (dr.available() != 0)
{
log.log(20, "ssh-rsa signature: dr.available() != 0 (II)");
return false;
}
if (digest.length != sha_message.length)
{
log.log(20, "ssh-rsa signature: digest.length != sha_message.length");
return false;
}
for (int i = 0; i < sha_message.length; i++)
{
if (sha_message[i] != digest[i])
{
log.log(20, "ssh-rsa signature: sha_message[i] != digest[i]");
return false;
}
}
return true;
}
}