test: cover invalid codesep positions for signature in taproot

test/functional/feature_taproot.py

@@ -431,7 +431,7 @@ DEFAULT_CONTEXT = {
     # The annex (only when mode=="taproot").
     "annex": None,
     # The codeseparator position (only when mode=="taproot").
-    "codeseppos": -1,
+    "codeseppos": 0xffffffff,
     # Which OP_CODESEPARATOR is the last executed one in the script (in legacy/P2SH/P2WSH).
     "codesepnum": -1,
     # The redeemscript to add to the scriptSig (if P2SH; None implies not P2SH).
@@ -779,6 +779,8 @@ def spenders_taproot_active():
         add_spender(spenders, "sighash/codesep_pk", tap=tap, leaf="codesep_pk", key=secs[1], codeseppos=0, **common, **SINGLE_SIG, **SIGHASH_BITFLIP, **ERR_SCHNORR_SIG)
         add_spender(spenders, "sighash/branched_codesep/left", tap=tap, leaf="branched_codesep", key=secs[0], codeseppos=3, **common, inputs=[getter("sign"), b'\x01'], **SIGHASH_BITFLIP, **ERR_SCHNORR_SIG)
         add_spender(spenders, "sighash/branched_codesep/right", tap=tap, leaf="branched_codesep", key=secs[1], codeseppos=6, **common, inputs=[getter("sign"), b''], **SIGHASH_BITFLIP, **ERR_SCHNORR_SIG)
+        add_spender(spenders, "sighash/codesep_pk_wrongpos1", tap=tap, leaf="codesep_pk", key=secs[1], codeseppos=0, **common, **SINGLE_SIG, failure={"codeseppos": 1}, **ERR_SCHNORR_SIG)
+        add_spender(spenders, "sighash/codesep_pk_wrongpos2", tap=tap, leaf="codesep_pk", key=secs[1], codeseppos=0, **common, **SINGLE_SIG, failure={"codeseppos": 0xfffffffe}, **ERR_SCHNORR_SIG)
 
     # Reusing the scripts above, test that various features affect the sighash.
     add_spender(spenders, "sighash/annex", tap=tap, leaf="pk_codesep", key=secs[1], hashtype=hashtype, standard=False, **SINGLE_SIG, annex=bytes([ANNEX_TAG]), failure={"sighash": override(default_sighash, annex=None)}, **ERR_SCHNORR_SIG)
@@ -1280,7 +1282,7 @@ def spenders_taproot_active():
         script = [pubs[1]]
         inputs = []
         opcount = 1
-        codeseppos = -1
+        codeseppos = 0xffffffff
         for pos, op in enumerate(ops):
             if op == -1:
                 codeseppos = opcount

test/functional/test_framework/script.py

@@ -847,7 +847,7 @@ def TaprootSignatureMsg(txTo, spent_utxos, hash_type, input_index=0, *, scriptpa
     if scriptpath:
         ss += TaggedHash("TapLeaf", bytes([leaf_ver]) + ser_string(leaf_script))
         ss += bytes([0])
-        ss += codeseparator_pos.to_bytes(4, "little", signed=True)
+        ss += codeseparator_pos.to_bytes(4, "little", signed=False)
     assert len(ss) == 175 - (in_type == SIGHASH_ANYONECANPAY) * 49 - (out_type != SIGHASH_ALL and out_type != SIGHASH_SINGLE) * 32 + (annex is not None) * 32 + scriptpath * 37
     return ss