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Fix transport encoding of nistp521 signatures (#623)

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SignatureECDSA.encode() does not correctly handle signatures longer
than 128 bytes, which affects signatures using the nistp521 curve.

This commits fixes the issue by replacing the ad-hoc ASN.1 DER
parsing with a use of ASN1InputStream.
This commit is contained in:
Fabian Henneke
2020-07-28 11:56:17 +02:00
committed by GitHub
parent 64f448d438
commit 4b1619d54f
1 changed files with 9 additions and 13 deletions
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22
src/main/java/net/schmizz/sshj/signature/SignatureECDSA.java
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@@ -15,6 +15,7 @@
*/
package net.schmizz.sshj.signature;
import com.hierynomus.asn1.encodingrules.der.DERDecoder;
import com.hierynomus.asn1.encodingrules.der.DEREncoder;
import com.hierynomus.asn1.types.ASN1Object;
import com.hierynomus.asn1.types.constructed.ASN1Sequence;
@@ -23,6 +24,7 @@ import net.schmizz.sshj.common.Buffer;
import net.schmizz.sshj.common.KeyType;
import net.schmizz.sshj.common.SSHRuntimeException;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.math.BigInteger;
@@ -87,22 +89,16 @@ public class SignatureECDSA extends AbstractSignature {
@Override
public byte[] encode(byte[] sig) {
int rIndex = 3;
int rLen = sig[rIndex++] & 0xff;
byte[] r = new byte[rLen];
System.arraycopy(sig, rIndex, r, 0, r.length);
ByteArrayInputStream bais = new ByteArrayInputStream(sig);
com.hierynomus.asn1.ASN1InputStream asn1InputStream = new com.hierynomus.asn1.ASN1InputStream(new DERDecoder(), bais);
int sIndex = rIndex + rLen + 1;
int sLen = sig[sIndex++] & 0xff;
byte[] s = new byte[sLen];
System.arraycopy(sig, sIndex, s, 0, s.length);
System.arraycopy(sig, 4, r, 0, rLen);
System.arraycopy(sig, 6 + rLen, s, 0, sLen);
ASN1Sequence sequence = asn1InputStream.readObject();
ASN1Integer r = (ASN1Integer) sequence.get(0);
ASN1Integer s = (ASN1Integer) sequence.get(1);
Buffer.PlainBuffer buf = new Buffer.PlainBuffer();
buf.putMPInt(new BigInteger(r));
buf.putMPInt(new BigInteger(s));
buf.putMPInt(r.getValue());
buf.putMPInt(s.getValue());
return buf.getCompactData();
}