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Add sighash filter flags

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Mononaut 2023-12-13 10:56:33 +00:00
parent 173bc127cb
commit e12f43e741
No known key found for this signature in database
GPG Key ID: A3F058E41374C04E
1 changed files with 81 additions and 7 deletions
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86
backend/src/api/common.ts
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@ -140,6 +140,65 @@ export class Common {
return matches;
}
static setSchnorrSighashFlags(flags: bigint, witness: string[]): bigint {
// no witness items
if (!witness?.length) {
return flags;
}
const hasAnnex = witness.length > 1 && witness[witness.length - 1].startsWith('50');
if (witness?.length === (hasAnnex ? 2 : 1)) {
// keypath spend, signature is the only witness item
if (witness[0].length === 130) {
flags |= this.setSighashFlags(flags, witness[0]);
} else {
flags |= TransactionFlags.sighash_default;
}
} else {
// scriptpath spend, all items except for the script, control block and annex could be signatures
for (let i = 0; i < witness.length - (hasAnnex ? 3 : 2); i++) {
// handle probable signatures
if (witness[i].length === 130) {
flags |= this.setSighashFlags(flags, witness[i]);
} else if (witness[i].length === 128) {
flags |= TransactionFlags.sighash_default;
}
}
}
return flags;
}
static isDERSig(w: string): boolean {
// heuristic to detect probable DER signatures
return (w.length >= 18
&& w.startsWith('30') // minimum DER signature length is 8 bytes + sighash flag (see https://mempool.space/testnet/tx/c6c232a36395fa338da458b86ff1327395a9afc28c5d2daa4273e410089fd433)
&& ['01, 02, 03, 81, 82, 83'].includes(w.slice(-2)) // signature must end with a valid sighash flag
&& (w.length === parseInt(w.slice(2, 4), 16) + 6) // second byte encodes the combined length of the R and S components
);
}
static setSegwitSighashFlags(flags: bigint, witness: string[]): bigint {
for (const w of witness) {
if (this.isDERSig(w)) {
flags |= this.setSighashFlags(flags, w);
}
}
return flags;
}
static setLegacySighashFlags(flags: bigint, scriptsig_asm: string): bigint {
for (const item of scriptsig_asm.split(' ')) {
// skip op_codes
if (item.startsWith('OP_')) {
continue;
}
// check pushed data
if (this.isDERSig(item)) {
flags |= this.setSighashFlags(flags, item);
}
}
return flags;
}
static setSighashFlags(flags: bigint, signature: string): bigint {
switch(signature.slice(-2)) {
case '01': return flags | TransactionFlags.sighash_all;
@ -159,6 +218,7 @@ export class Common {
} else if (tx.version === 2) {
flags |= TransactionFlags.v2;
}
const reusedAddresses: { [address: string ]: number } = {};
const inValues = {};
const outValues = {};
let rbf = false;
@ -167,10 +227,7 @@ export class Common {
rbf = true;
}
switch (vin.prevout?.scriptpubkey_type) {
case 'p2pk': {
flags |= TransactionFlags.p2pk;
flags = this.setSighashFlags(flags, vin.scriptsig);
} break;
case 'p2pk': flags |= TransactionFlags.p2pk; break;
case 'multisig': flags |= TransactionFlags.p2ms; break;
case 'p2pkh': flags |= TransactionFlags.p2pkh; break;
case 'p2sh': flags |= TransactionFlags.p2sh; break;
@ -186,6 +243,19 @@ export class Common {
}
} break;
}
// sighash flags
if (vin.prevout?.scriptpubkey_type === 'v1_p2tr') {
flags |= this.setSchnorrSighashFlags(flags, vin.witness);
} else if (vin.witness) {
flags |= this.setSegwitSighashFlags(flags, vin.witness);
} else if (vin.scriptsig_asm) {
flags |= this.setLegacySighashFlags(flags, vin.scriptsig_asm);
}
if (vin.prevout?.scriptpubkey_address) {
reusedAddresses[vin.prevout?.scriptpubkey_address] = (reusedAddresses[vin.prevout?.scriptpubkey_address] || 0) + 1;
}
inValues[vin.prevout?.value || Math.random()] = (inValues[vin.prevout?.value || Math.random()] || 0) + 1;
}
if (rbf) {
@ -207,6 +277,9 @@ export class Common {
case 'v1_p2tr': flags |= TransactionFlags.p2tr; break;
case 'op_return': flags |= TransactionFlags.op_return; break;
}
if (vout.scriptpubkey_address) {
reusedAddresses[vout.scriptpubkey_address] = (reusedAddresses[vout.scriptpubkey_address] || 0) + 1;
}
outValues[vout.value || Math.random()] = (outValues[vout.value || Math.random()] || 0) + 1;
}
if (tx.ancestors?.length) {
@ -219,8 +292,9 @@ export class Common {
flags |= TransactionFlags.replacement;
}
// fast but bad heuristic to detect possible coinjoins
// (at least 5 inputs and 5 outputs, less than half of which are unique amounts)
if (tx.vin.length >= 5 && tx.vout.length >= 5 && (Object.keys(inValues).length + Object.keys(outValues).length) <= (tx.vin.length + tx.vout.length) / 2 ) {
// (at least 5 inputs and 5 outputs, less than half of which are unique amounts, with no address reuse)
const addressReuse = Object.values(reusedAddresses).reduce((acc, count) => Math.max(acc, count), 0) > 1;
if (!addressReuse && tx.vin.length >= 5 && tx.vout.length >= 5 && (Object.keys(inValues).length + Object.keys(outValues).length) <= (tx.vin.length + tx.vout.length) / 2 ) {
flags |= TransactionFlags.coinjoin;
}
// more than 5:1 input:output ratio