Merge pull request #648 from OrfeasLitos/get-keys-from-multisig

Implement and test KeyRing.fromMultisigScript(script, i)

lib/primitives/keyring.js

@@ -251,6 +251,37 @@ class KeyRing {
     return new this().fromScript(key, script, compress);
   }
 
+  /**
+   * Get ith public key from multisig script.
+   * @private
+   * @param {Script} script
+   * @param {Number} i
+   * @returns {KeyRing}
+   */
+
+  fromMultisigScript(script, i) {
+    assert(script instanceof Script, 'Non-script passed.');
+    assert(script.isMultisig(), 'Script must be multisig');
+
+    const n = script.getSmall(-2);
+    assert(i >= 1 && i <= n, 'Requested `i`th key, `n` available');
+
+    this.fromKey(script.code[i].toData());
+
+    return this;
+  }
+
+  /**
+   * Instantiate keyring from ith key in multisig script.
+   * @param {Script} script
+   * @param {Number} i
+   * @returns {KeyRing}
+   */
+
+  static fromMultisigScript(script, i) {
+    return new this().fromMultisigScript(script, i);
+  }
+
   /**
    * Calculate WIF serialization size.
    * @returns {Number}

test/keyring-test.js

@@ -5,6 +5,7 @@
 
 const assert = require('./util/assert');
 const KeyRing = require('../lib/primitives/keyring');
+const Script = require('../lib/script/script');
 
 const uncompressed = KeyRing.fromSecret(
   '5KYZdUEo39z3FPrtuX2QbbwGnNP5zTd7yyr2SC1j299sBCnWjss', 'main');
@@ -49,4 +50,17 @@ describe('KeyRing', function() {
       'L4rK1yDtCWekvXuE6oXD9jCYfFNV2cWRpVuPLBcCU2z8TrisoyY1',
       compressed.toSecret('main'));
   });
+
+  it('should get keys from multisig', () => {
+    const script = Script.fromMultisig(1, 2, [
+      compressed.getPublicKey(),
+      uncompressed.getPublicKey()]);
+
+    assert.strictEqual(
+      compressed.getPublicKey(),
+      KeyRing.fromMultisigScript(script, 1).getPublicKey());
+    assert.strictEqual(
+      uncompressed.getPublicKey(),
+      KeyRing.fromMultisigScript(script, 2).getPublicKey());
+  });
 });