Figure out what is missing during signing

When signing an input, figure out what was requested for but was unable
to be found and store it in a SignatureData.

Return this information in SignPSBTInput.

src/psbt.cpp

@@ -191,13 +191,12 @@ void PSBTOutput::Merge(const PSBTOutput& output)
  if (redeem_script.empty() && !output.redeem_script.empty()) redeem_script = output.redeem_script;
  if (witness_script.empty() && !output.witness_script.empty()) witness_script = output.witness_script;
 }
-
 bool PSBTInputSigned(PSBTInput& input)
 {
  return !input.final_script_sig.empty() || !input.final_script_witness.IsNull();
 }
 
-bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, int sighash)
+bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, int sighash, SignatureData* out_sigdata, bool use_dummy)
 {
  PSBTInput& input = psbt.inputs.at(index);
  const CMutableTransaction& tx = *psbt.tx;
@@ -237,9 +236,14 @@ bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction&
  return false;
  }
 
- MutableTransactionSignatureCreator creator(&tx, index, utxo.nValue, sighash);
  sigdata.witness = false;
- bool sig_complete = ProduceSignature(provider, creator, utxo.scriptPubKey, sigdata);
+ bool sig_complete;
+ if (use_dummy) {
+ sig_complete = ProduceSignature(provider, DUMMY_SIGNATURE_CREATOR, utxo.scriptPubKey, sigdata);
+ } else {
+ MutableTransactionSignatureCreator creator(&tx, index, utxo.nValue, sighash);
+ sig_complete = ProduceSignature(provider, creator, utxo.scriptPubKey, sigdata);
+ }
  // Verify that a witness signature was produced in case one was required.
  if (require_witness_sig && !sigdata.witness) return false;
  input.FromSignatureData(sigdata);
@@ -250,6 +254,14 @@ bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction&
  input.non_witness_utxo = nullptr;
  }
 
+ // Fill in the missing info
+ if (out_sigdata) {
+ out_sigdata->missing_pubkeys = sigdata.missing_pubkeys;
+ out_sigdata->missing_sigs = sigdata.missing_sigs;
+ out_sigdata->missing_redeem_script = sigdata.missing_redeem_script;
+ out_sigdata->missing_witness_script = sigdata.missing_witness_script;
+ }
+
  return sig_complete;
 }
 

src/psbt.h

@@ -544,7 +544,7 @@ struct PartiallySignedTransaction
 bool PSBTInputSigned(PSBTInput& input);
 
 /** Signs a PSBTInput, verifying that all provided data matches what is being signed. */
-bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, int sighash = SIGHASH_ALL);
+bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, int sighash = SIGHASH_ALL, SignatureData* out_sigdata = nullptr, bool use_dummy = false);
 
 /**
  * Finalizes a PSBT if possible, combining partial signatures.

src/script/sign.cpp

@@ -83,6 +83,8 @@ static bool CreateSig(const BaseSignatureCreator& creator, SignatureData& sigdat
  assert(i.second);
  return true;
  }
+ // Could not make signature or signature not found, add keyid to missing
+ sigdata.missing_sigs.push_back(keyid);
  return false;
 }
 
@@ -116,17 +118,24 @@ static bool SignStep(const SigningProvider& provider, const BaseSignatureCreator
  case TX_PUBKEYHASH: {
  CKeyID keyID = CKeyID(uint160(vSolutions[0]));
  CPubKey pubkey;
- if (!GetPubKey(provider, sigdata, keyID, pubkey)) return false;
+ if (!GetPubKey(provider, sigdata, keyID, pubkey)) {
+ // Pubkey could not be found, add to missing
+ sigdata.missing_pubkeys.push_back(keyID);
+ return false;
+ }
  if (!CreateSig(creator, sigdata, provider, sig, pubkey, scriptPubKey, sigversion)) return false;
  ret.push_back(std::move(sig));
  ret.push_back(ToByteVector(pubkey));
  return true;
  }
  case TX_SCRIPTHASH:
- if (GetCScript(provider, sigdata, uint160(vSolutions[0]), scriptRet)) {
+ h160 = uint160(vSolutions[0]);
+ if (GetCScript(provider, sigdata, h160, scriptRet)) {
  ret.push_back(std::vector<unsigned char>(scriptRet.begin(), scriptRet.end()));
  return true;
  }
+ // Could not find redeemScript, add to missing
+ sigdata.missing_redeem_script = h160;
  return false;
 
  case TX_MULTISIG: {
@@ -154,6 +163,8 @@ static bool SignStep(const SigningProvider& provider, const BaseSignatureCreator
  ret.push_back(std::vector<unsigned char>(scriptRet.begin(), scriptRet.end()));
  return true;
  }
+ // Could not find witnessScript, add to missing
+ sigdata.missing_witness_script = uint256(vSolutions[0]);
  return false;
 
  default:

src/script/sign.h

@@ -117,6 +117,10 @@ struct SignatureData {
  CScriptWitness scriptWitness; ///< The scriptWitness of an input. Contains complete signatures or the traditional partial signatures format. scriptWitness is part of a transaction input per BIP 144.
  std::map<CKeyID, SigPair> signatures; ///< BIP 174 style partial signatures for the input. May contain all signatures necessary for producing a final scriptSig or scriptWitness.
  std::map<CKeyID, std::pair<CPubKey, KeyOriginInfo>> misc_pubkeys;
+ std::vector<CKeyID> missing_pubkeys; ///< KeyIDs of pubkeys which could not be found
+ std::vector<CKeyID> missing_sigs; ///< KeyIDs of pubkeys for signatures which could not be found
+ uint160 missing_redeem_script; ///< ScriptID of the missing redeemScript (if any)
+ uint256 missing_witness_script; ///< SHA256 of the missing witnessScript (if any)
 
  SignatureData() {}
  explicit SignatureData(const CScript& script) : scriptSig(script) {}