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neow3j: Java/Kotlin/Android Development Toolkit for the Neo Blockchain
package io.neow3j.script;
import io.neow3j.constants.NeoConstants;
import io.neow3j.crypto.ECKeyPair.ECPublicKey;
import io.neow3j.serialization.BinaryReader;
import io.neow3j.serialization.BinaryWriter;
import io.neow3j.serialization.IOUtils;
import io.neow3j.serialization.NeoSerializable;
import io.neow3j.serialization.exceptions.DeserializationException;
import io.neow3j.transaction.exceptions.ScriptFormatException;
import io.neow3j.types.Hash160;
import io.neow3j.utils.ArrayUtils;
import io.neow3j.utils.Numeric;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import static io.neow3j.constants.NeoConstants.MAX_PUBLIC_KEYS_PER_MULTISIG_ACCOUNT;
/**
* A verification script is part of a witness and is simply a sequence of neo-vm instructions.
* The verification script is the part of a witness that describes what has to be verified such
* that the witness is valid. E.g., for a regular signature witness the verification script is
* made up of a check-signature call and it expects a signature as input.
*/
public class VerificationScript extends NeoSerializable {
private byte[] script;
/**
* Creates an empty verification script.
*/
public VerificationScript() {
script = new byte[0];
}
/**
* Creates a verification script from the given byte array.
*
* @param script The script.
*/
public VerificationScript(byte[] script) {
this.script = script;
}
/**
* Creates a verification script for the given public key. The resulting verification
* script contains a signature check with the given public key as the expected signer.
*
* @param publicKey Key to create the script for.
*/
public VerificationScript(ECPublicKey publicKey) {
this.script = ScriptBuilder.buildVerificationScript(publicKey.getEncoded(true));
}
/**
* Creates a multi-sig verification script for the given keys and signing threshold.
* The resulting verification script contains a multi-signature check with the given public
* keys as the expected signer.
*
* @param publicKeys The public keys to create the script for.
* @param signingThreshold The minimum number of public keys needed to sign transactions from
* the given public keys.
*/
public VerificationScript(List publicKeys, int signingThreshold) {
if (signingThreshold < 1 || signingThreshold > publicKeys.size()) {
throw new IllegalArgumentException("Signing threshold must be at least 1 and not " +
"higher than the number of public keys.");
}
if (publicKeys.size() > MAX_PUBLIC_KEYS_PER_MULTISIG_ACCOUNT) {
throw new IllegalArgumentException("At max " + MAX_PUBLIC_KEYS_PER_MULTISIG_ACCOUNT +
" public keys can take part in a multi-sig account");
}
this.script = ScriptBuilder.buildVerificationScript(publicKeys, signingThreshold);
}
/**
* Gets this verification script as a byte array.
*
* @return the script as a byte array.
*/
public byte[] getScript() {
return script;
}
/**
* Serializes this script to a byte array. This is only meant to be used in transaction
* serialization because it adds the size of the script as a prefix. Use {@link
* VerificationScript#getScript()} instead to get this scripts byte array.
*
* @return the serialized script for usage in a transaction array.
*/
@Override
public byte[] toArray() {
// Only overridden for documentation.
return super.toArray();
}
/**
* Gets the script hash of this verification script.
*
* @return the script hash.
*/
public Hash160 getScriptHash() {
if (this.script.length == 0) {
return null;
} else {
return Hash160.fromScript(this.script);
}
}
@Override
public int getSize() {
return IOUtils.getVarSize(this.script.length) + this.script.length;
}
/**
* Extracts the number of signatures required for signing this verification script.
*
* @return The signing threshold.
* @throws ScriptFormatException if this verification script is not an ordinary address script
* or multi-address script.
*/
public int getSigningThreshold() {
if (isSingleSigScript()) {
return 1;
} else if (isMultiSigScript()) {
try {
return new BinaryReader(script).readPushInteger();
} catch (DeserializationException e) {
throw new RuntimeException(e);
}
}
throw new ScriptFormatException("The signing threshold cannot be determined because this "
+ "script does not apply to the format of a signature verification script.");
}
/**
* Gets the number of accounts taking part in this verification script.
*
* @return The number of accounts.
* @throws ScriptFormatException if this verification script is not an ordinary address script
* or multi-address script.
*/
public int getNrOfAccounts() {
return getPublicKeys().size();
}
/**
* Checks if this verification script is from single signature account.
*
* @return true if this script is from a single signature account. False, otherwise.
*/
public boolean isSingleSigScript() {
if (script.length != 40) {
return false;
}
String interopService = Numeric.toHexStringNoPrefix(ArrayUtils.getLastNBytes(script, 4));
return script[0] == OpCode.PUSHDATA1.getCode()
&& script[1] == 33 // 33 bytes of public key
&& script[35] == OpCode.SYSCALL.getCode()
&& interopService.equals(
InteropService.SYSTEM_CRYPTO_CHECKSIG.getHash());
}
/**
* Checks if this verification script is from a multi signature account.
*
* @return true if this script is from a multi signature account. False, otherwise.
*/
public boolean isMultiSigScript() {
if (script.length < 42) {
return false;
}
try {
BinaryReader reader = new BinaryReader(this.script);
int n = reader.readPushInteger(); // Signing Threshold (n of m)
if (n < 1 || n > NeoConstants.MAX_PUBLIC_KEYS_PER_MULTISIG_ACCOUNT) {
return false;
}
int m = 0; // Number of participating keys
while (reader.readByte() == OpCode.PUSHDATA1.getCode()) {
// Position at PUSHDATA1 + (1 byte data size + 33 bytes + 1 byte to make sure
// script does not end after the key.
if (script.length <= reader.getPosition() + 35) {
return false;
}
// Byte after PUSHDATA1 must have value 33 for 33 bytes of public key data.
if (reader.readByte() != 33) {
return false;
}
reader.readEncodedECPoint();
m++;
// Mark the current position to be able to reset the last readBytes() which is not a
// PUSHDATA1 anymore.
reader.mark(0);
}
if (n > m || m > MAX_PUBLIC_KEYS_PER_MULTISIG_ACCOUNT) {
return false;
}
reader.reset(); // Reset the last performed readBytes() from the while loop.
int alsoM = reader.readPushInteger();
if (m != alsoM) {
return false;
}
if (reader.readByte() != OpCode.SYSCALL.getCode()) {
return false;
}
byte[] interopServiceCode = new byte[4];
reader.read(interopServiceCode, 0, 4);
if (!Numeric.toHexStringNoPrefix(interopServiceCode)
.equals(InteropService.SYSTEM_CRYPTO_CHECKMULTISIG.getHash())) {
return false;
}
} catch (DeserializationException | IOException e) {
return false;
}
return true;
}
/**
* Gets the public keys that are encoded in this verification script. If this script is from a
* single signature account the resulting list will only contain one key.
*
* @return the list of public keys encoded in this script.
*/
public List getPublicKeys() {
BinaryReader reader = new BinaryReader(this.script);
List keys = new ArrayList<>();
try {
if (isSingleSigScript()) {
reader.readByte(); // OpCode.PUSHDATA1;
reader.readByte(); // size byte
keys.add(new ECPublicKey(reader.readECPoint()));
return keys;
} else if (isMultiSigScript()) {
reader.readPushInteger(); // Signing Threshold (n of m)
while (reader.readByte() == OpCode.PUSHDATA1.getCode()) {
reader.readByte(); // size byte
keys.add(new ECPublicKey(reader.readECPoint()));
}
return keys;
}
} catch (IOException | DeserializationException e) {
// Shouldn't happen because the underlying stream is a ByteArrayInputStream.
throw new RuntimeException(e);
}
throw new ScriptFormatException("The verification script is in an incorrect format. No "
+ "public keys can be read from it.");
}
@Override
public void deserialize(BinaryReader reader) throws DeserializationException {
try {
script = reader.readVarBytes();
} catch (IOException e) {
throw new DeserializationException(e);
}
}
@Override
public void serialize(BinaryWriter writer) throws IOException {
writer.writeVarBytes(script);
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (!(o instanceof VerificationScript)) {
return false;
}
VerificationScript that = (VerificationScript) o;
return Arrays.equals(getScript(), that.getScript());
}
@Override
public int hashCode() {
return Objects.hash(getScript());
}
@Override
public String toString() {
return "VerificationScript{" +
"script=" + Numeric.toHexStringNoPrefix(script) + '}';
}
}
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