P2TSH: adding additional script verification tests that verify correct

witness program and parity bit.

Credit to:  https://github.com/billymcbip

Author: jbride

src/script/interpreter.cpp

@@ -2406,6 +2406,11 @@ static bool VerifyWitnessProgram(const CScriptWitness& witness, int witversion,
                 return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_MISMATCH);
             }
             execdata.m_tapleaf_hash_init = true;
+            // Check for P2TSH-specific parity requirement (must be 0xc1 for Tapscript)
+            if ((control[0] & TAPROOT_LEAF_MASK) == TAPROOT_LEAF_TAPSCRIPT &&
+                control[0] != P2TSH_LEAF_TAPSCRIPT) {
+                return set_error(serror, SCRIPT_ERR_P2TSH_WRONG_PARITY_BIT);
+            }
             if (control[0] == P2TSH_LEAF_TAPSCRIPT) {
                 // Tapscript (leaf version 0xc1 since parity is always 1)
                 exec_script = CScript(script.begin(), script.end());

src/script/script_error.cpp

@@ -123,6 +123,8 @@ std::string ScriptErrorString(const ScriptError serror)
             return "Signature is found in scriptCode";
         case SCRIPT_ERR_P2TSH_WRONG_CONTROL_SIZE:
             return "Invalid P2TSH control block size";
+        case SCRIPT_ERR_P2TSH_WRONG_PARITY_BIT:
+            return "P2TSH leaf must use parity bit 1 (0xc1)";
         case SCRIPT_ERR_UNKNOWN_ERROR:
         case SCRIPT_ERR_ERROR_COUNT:
         default: break;

src/script/script_error.h

@@ -85,6 +85,7 @@ typedef enum ScriptError_t
 
     /* P2TSH */
     SCRIPT_ERR_P2TSH_WRONG_CONTROL_SIZE,
+    SCRIPT_ERR_P2TSH_WRONG_PARITY_BIT,
 
     /* Constant scriptCode */
     SCRIPT_ERR_OP_CODESEPARATOR,

src/test/data/script_tests.json

@@ -2668,6 +2668,87 @@
     "TAPSCRIPT Test that DROP operations do not execute inside of a false IF conditional"
 ],
 
+["P2TSH tests"],
+[
+    [
+        "aa",
+        "bb",
+        "87",
+        "c1",
+        0.00000001
+    ],
+    "",
+    "0x52 0x20 0x7e04991706edb31549f786fa7113bb857ceb26174f7d08e9efa91decf13324a0",
+    "P2SH,WITNESS,TAPROOT",
+    "OK",
+    "P2TSH: Simple negative OP_EQUAL test pre-activation"
+],
+[
+    [
+        "aa",
+        "bb",
+        "87",
+        "c1",
+        0.00000001
+    ],
+    "",
+    "0x52 0x20 0x7e04991706edb31549f786fa7113bb857ceb26174f7d08e9efa91decf13324a0",
+    "P2SH,WITNESS,TAPROOT,P2TSH",
+    "EVAL_FALSE",
+    "P2TSH: Simple negative OP_EQUAL test post-activation"
+],
+[
+    [
+        "aa",
+        "aa",
+        "87",
+        "c1",
+        0.00000001
+    ],
+    "",
+    "0x52 0x20 0x7e04991706edb31549f786fa7113bb857ceb26174f7d08e9efa91decf13324a0",
+    "P2SH,WITNESS,TAPROOT,P2TSH",
+    "OK",
+    "P2TSH: Simple positive OP_EQUAL test post-activation"
+],
+[
+    [
+        "aa",
+        0.00000001
+    ],
+    "",
+    "0x52 0x20 0x7e04991706edb31549f786fa7113bb857ceb26174f7d08e9efa91decf13324a0",
+    "P2SH,WITNESS,TAPROOT,P2TSH",
+    "WITNESS_PROGRAM_MISMATCH",
+    "P2TSH: Key path spending not supported"
+],
+[
+    [
+        "aa",
+        "aa",
+        0.00000001
+    ],
+    "",
+    "0x52 0x20 0x7e04991706edb31549f786fa7113bb857ceb26174f7d08e9efa91decf13324a0",
+    "P2SH,WITNESS,TAPROOT,P2TSH",
+    "WITNESS_PROGRAM_MISMATCH",
+    "P2TSH: Witness program mismatch"
+],
+[
+    [
+        "aa",
+        "aa",
+        "87",
+        "c0",
+        0.00000001
+    ],
+    "",
+    "0x52 0x20 0x7e04991706edb31549f786fa7113bb857ceb26174f7d08e9efa91decf13324a0",
+    "P2SH,WITNESS,TAPROOT,P2TSH",
+    "P2TSH_WRONG_PARITY_BIT",
+    "P2TSH: Wrong parity bit"
+],
+
 ["NULLFAIL should cover all signatures and signatures only"],
 ["0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0", "0x01 0x14 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0x01 0x14 CHECKMULTISIG NOT", "DERSIG", "OK", "BIP66 and NULLFAIL-compliant"],
 ["0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0", "0x01 0x14 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0x01 0x14 CHECKMULTISIG NOT", "DERSIG,NULLFAIL", "OK", "BIP66 and NULLFAIL-compliant"],

src/test/script_tests.cpp

@@ -93,6 +93,8 @@ static ScriptErrorDesc script_errors[]={
     {SCRIPT_ERR_WITNESS_PUBKEYTYPE, "WITNESS_PUBKEYTYPE"},
     {SCRIPT_ERR_OP_CODESEPARATOR, "OP_CODESEPARATOR"},
     {SCRIPT_ERR_SIG_FINDANDDELETE, "SIG_FINDANDDELETE"},
+    {SCRIPT_ERR_P2TSH_WRONG_CONTROL_SIZE, "P2TSH_WRONG_CONTROL_SIZE"},
+    {SCRIPT_ERR_P2TSH_WRONG_PARITY_BIT, "P2TSH_WRONG_PARITY_BIT"},
 };
 
 static std::string FormatScriptError(ScriptError_t err)