bitcoin-tx: Require that input amount is provided for witness transactions #23784

pull theStack wants to merge 2 commits into bitcoin:master from theStack:bitcoin-tx_check_witness_input_amount changing 4 files +30 −1

theStack commented at 3:25 PM on December 15, 2021: member

This PR picks up the obviously abandoned PR #13608 (last activity was three and a half years ago) by rebasing it on master and adding missing tests. Original PR description: "Applies fix from #12458 / #13547 to bitcoin-tx."

The private key is the compressed version of the one used in most other util tests (5HpHagT65TZzG1PH3CSu63k8DbpvD8s5ip4nEB3kEsreAnchuDf, corresponds to the scalar value k=1 in big endian), since segwit signing refuses uncompressed keys.

The error message from the picked up PR is changed to not include the amount, as showing any value would be just confusing.
theStack force-pushed on Dec 15, 2021
DrahtBot added the label Build system on Dec 15, 2021
DrahtBot added the label Utils/log/libs on Dec 15, 2021
laanwj removed the label Build system on Dec 15, 2021
in src/bitcoin-tx.cpp:673 in 8dc5fa1ee5 outdated
```
 668 | @@ -669,6 +669,10 @@ static void MutateTxSign(CMutableTransaction& tx, const std::string& flagStr)
 669 |          if (!fHashSingle || (i < mergedTx.vout.size()))
 670 |              ProduceSignature(keystore, MutableTransactionSignatureCreator(&mergedTx, i, amount, nHashType), prevPubKey, sigdata);
 671 |  
 672 | +        if (amount == MAX_MONEY && !sigdata.scriptWitness.IsNull()) {
 673 | +            throw std::runtime_error(strprintf("Missing amount for %s", coin.out.ToString()));
```
josibake commented at 2:57 PM on December 29, 2021:

I tend to agree that seeing CTxOut(nValue=21000000.00000000... when the error is for a missing amount is confusing.

Using MAX_AMOUNT for the check is already a nuanced concept (I had to read through all the linked PRs/issues before I understood why it was being used here). I don't think displaying 0 is correct, either, since a 0 amount UTXO is a valid spend.

Perhaps just print the scriptPubKey? Something like Missing amount for CTxOut with scriptPubKey=0014751e76e8199196d454941c45d1

theStack commented at 8:29 PM on December 29, 2021:

Thanks, I agree that the best would be to not display the amount at all if it is missing and picked up your suggestion.
josibake commented at 2:59 PM on December 29, 2021: member

Concept ACK

+1 for adding the tests! I don't think printing nValue=21000000.00000000 is a great idea, so I left a suggestion inline
josibake commented at 3:00 PM on December 29, 2021: member

One other suggestion: add a test with a 0 amount as that is a good (edge?) case to have tested.
Require that input amount is provided for bitcoin-tx witness transactions
Co-authored-by: Sebastian Falbesoner <sebastian.falbesoner@gmail.com>
c337b27d7c
test: check that bitcoin-tx detects missing input amount for segwit transactions 8bd34dc774
theStack force-pushed on Dec 29, 2021
theStack commented at 8:33 PM on December 29, 2021: member
Thanks for the valuable review @josibake! Rebased on master and force-pushed with the following adaptions:
- changed the error message to not include the amount, as showing any value would be just confusing (https://github.com/bitcoin/bitcoin/pull/23784#discussion_r776366558)
- changed the input value of the first introduced passing test from 31337 to 0, as this is an edge-case (https://github.com/bitcoin/bitcoin/pull/23784#issuecomment-1002635962)
(git range-diff 8dc5fa1...8bd34dc)
josibake commented at 1:13 AM on December 30, 2021: member

ACK https://github.com/bitcoin/bitcoin/commit/8bd34dc774788cbf3cad8e139542a0ed9f3e8bb4
MarcoFalke commented at 11:40 AM on January 3, 2022: member

Needs OP adjusted before merge?
theStack commented at 1:57 PM on January 3, 2022: member

Needs OP adjusted before merge?

Thanks, done.
MarcoFalke merged this on Jan 5, 2022
MarcoFalke closed this on Jan 5, 2022
theStack deleted the branch on Jan 5, 2022
sidhujag referenced this in commit aefcb9b11f on Jan 6, 2022
DrahtBot locked this on Jan 5, 2023

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#12458 Enforce that amount is provided for signrawtransaction prevtxs #13547 Make signrawtransaction* give an error when amount is needed but missing #13608 WIP: bitcoin-tx: Require that input amount is provided for witness transactions