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support bip 137 for message signing, but handle electrum approach as well when verifying

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This commit is contained in:
Craig Raw 2020-09-03 19:27:18 +02:00
parent ee49ddd94b
commit 10ebfe463d
1 changed files with 36 additions and 7 deletions
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43
src/main/java/com/sparrowwallet/drongo/crypto/ECKey.java
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@ -1,6 +1,7 @@
package com.sparrowwallet.drongo.crypto;
import com.sparrowwallet.drongo.Utils;
import com.sparrowwallet.drongo.protocol.ScriptType;
import com.sparrowwallet.drongo.protocol.Sha256Hash;
import com.sparrowwallet.drongo.protocol.SignatureDecodeException;
import com.sparrowwallet.drongo.protocol.VarInt;
@ -716,12 +717,12 @@ public class ECKey implements EncryptableItem {
* @throws IllegalStateException if this ECKey does not have the private part.
* @throws KeyCrypterException if this ECKey is encrypted and no AESKey is provided or it does not decrypt the ECKey.
*/
public String signMessage(String message, Key aesKey) throws KeyCrypterException {
public String signMessage(String message, ScriptType scriptType, Key aesKey) throws KeyCrypterException {
byte[] data = formatMessageForSigning(message);
Sha256Hash hash = Sha256Hash.twiceOf(data);
ECDSASignature sig = sign(hash, aesKey);
byte recId = findRecoveryId(hash, sig);
int headerByte = recId + 27 + (isCompressed() ? 4 : 0);
int headerByte = recId + getSigningTypeConstant(scriptType);
byte[] sigData = new byte[65]; // 1 header + 32 bytes for R + 32 bytes for S
sigData[0] = (byte) headerByte;
System.arraycopy(Utils.bigIntegerToBytes(sig.r, 32), 0, sigData, 1, 32);
@ -729,6 +730,25 @@ public class ECKey implements EncryptableItem {
return new String(Base64.getEncoder().encode(sigData), StandardCharsets.UTF_8);
}
/**
* Although no standard has yet been decided on, we follow Trezor's approach for now as documented in
* https://github.com/bitcoin/bips/blob/master/bip-0137.mediawiki
*
* @param scriptType The script type of the address used to sign
* @return A constant used to alter the header of the signature in order to distinguish between different script types
*/
private int getSigningTypeConstant(ScriptType scriptType) {
if(scriptType == ScriptType.P2PKH) {
return 27 + (isCompressed() ? 4 : 0);
} else if(scriptType == ScriptType.P2SH_P2WPKH) {
return 35;
} else if(scriptType == ScriptType.P2WPKH) {
return 39;
}
throw new IllegalArgumentException("Script type of " + scriptType + " is not supported for message signing");
}
/**
* Given an arbitrary piece of text and a Bitcoin-format message signature encoded in base64, returns an ECKey
* containing the public key that was used to sign it. This can then be compared to the expected public key to
@ -738,9 +758,10 @@ public class ECKey implements EncryptableItem {
*
* @param message Some piece of human readable text.
* @param signatureBase64 The Bitcoin-format message signature in base64
* @param electrumFormat Whether to generate a key following Electrum's approach of regarding P2SH-P2WSH as the same as P2PKH uncompressed
* @throws SignatureException If the public key could not be recovered or if there was a signature format error.
*/
public static ECKey signedMessageToKey(String message, String signatureBase64) throws SignatureException {
public static ECKey signedMessageToKey(String message, String signatureBase64, boolean electrumFormat) throws SignatureException {
byte[] signatureEncoded;
try {
signatureEncoded = Base64.getDecoder().decode(signatureBase64);
@ -755,7 +776,7 @@ public class ECKey implements EncryptableItem {
int header = signatureEncoded[0] & 0xFF;
// The header byte: 0x1B = first key with even y, 0x1C = first key with odd y,
// 0x1D = second key with even y, 0x1E = second key with odd y
if(header < 27 || header > 34) {
if(header < 27 || header > 42) {
throw new SignatureException("Header byte out of range: " + header);
}
BigInteger r = new BigInteger(1, Arrays.copyOfRange(signatureEncoded, 1, 33));
@ -766,7 +787,15 @@ public class ECKey implements EncryptableItem {
// JSON-SPIRIT hands back. Assume UTF-8 for now.
Sha256Hash messageHash = Sha256Hash.twiceOf(messageBytes);
boolean compressed = false;
if(header >= 31) {
if(header >= 39) { // this is a bech32 signature
header -= 12;
compressed = true;
}
else if(header >= 35 && !electrumFormat) { // this is a segwit p2sh signature
compressed = true;
header -= 8;
}
else if(header >= 31) { // this is a compressed key signature
compressed = true;
header -= 4;
}
@ -779,11 +808,11 @@ public class ECKey implements EncryptableItem {
}
/**
* Convenience wrapper around {@link ECKey#signedMessageToKey(String, String)}. If the key derived from the
* Convenience wrapper around {@link ECKey#signedMessageToKey(String, String, boolean)}. If the key derived from the
* signature is not the same as this one, throws a SignatureException.
*/
public void verifyMessage(String message, String signatureBase64) throws SignatureException {
ECKey key = ECKey.signedMessageToKey(message, signatureBase64);
ECKey key = ECKey.signedMessageToKey(message, signatureBase64, false);
if(!key.pub.equals(pub)) {
throw new SignatureException("Signature did not match for message");
}