Signet mining is not possible when using descriptor wallet #28911

Is there an existing issue for this?

• I have searched the existing issues

Current behaviour

Signet mining is not possible when using descriptor wallet. The error message is "PSBT signing failed"

Errors were confirmed in the following two cases.

1. In an environment where mining is performed using a legacy wallet, the wallet is changed to a descriptor type using the "migratewallet" command.
2. A case where the private key descriptor of the address that generated the signetchallenge was imported into a new descriptor wallet.

Expected behaviour

signet mining

Steps to reproduce

bitcoin core v25.0, v26.0rc2

Relevant log output

PSBT signing failed

How did you obtain Bitcoin Core

Pre-built binaries

What version of Bitcoin Core are you using?

v25.0, v26.0rc2

Operating system and version

ubuntu22.04

Machine specifications

No response

Could you share the signet challenge?

Quick guess; you defined the block script as a multisig, and you didn't import the multisig descriptor. The wallet will not automatically infer the multisig redeem script if it imported pk()/pkh()/wpkh() descriptors.

@furszy You can reproduce the phenomenon by following the steps below.

wget https://bitcoincore.org/bin/bitcoin-core-25.0/bitcoin-25.0-x86_64-linux-gnu.tar.gz
tar -xzvf bitcoin-25.0-x86_64-linux-gnu.tar.gz
cd bitcoin-25.0
mv bin/* .

git clone https://github.com/bitcoin/bitcoin.git
cd bitcoin
git checkout v25.0
cd ..
cp -r bitcoin/test/functional/test_framework .
cp bitcoin/contrib/signet/miner .

./bitcoind -regtest -daemon
./bitcoin-cli -regtest createwallet "test" false false "" false false
ADDR=$(./bitcoin-cli -regtest getnewaddress "" "legacy")
echo $ADDR
mqKkNvg2zGLp7LrEkKzZyheg2RKxLpVGdx

PRIVKEY=$(./bitcoin-cli -regtest dumpprivkey $ADDR)
echo $PRIVKEY
cPVg1oJmHSwWCgzAbAeH7ZcBHyqtGJBZCr79tj6fWgnVD4YNXcii

./bitcoin-cli -regtest getaddressinfo $ADDR | grep pubkey
  "pubkey": "03176706ed990b936e2348392c08cfc9b7a8550d88b2b4cde4175bfb3b8af6398e",

./bitcoin-cli -regtest stop

CHALLENGE=512103176706ed990b936e2348392c08cfc9b7a8550d88b2b4cde4175bfb3b8af6398e51ae

./bitcoind -signet -daemon -signetchallenge=$CHALLENGE
CLI="./bitcoin-cli -signet"
$CLI createwallet "signet" false false "" false false
$CLI -signet importprivkey $PRIVKEY

MINER="./miner"
GRIND="./bitcoin-util grind"
ADDR=$(./bitcoin-cli -signet getnewaddress "" "legacy")
echo $ADDR
mvESocNVHsEmWurJ4V62CA6C4C8cwKYfLH

NBITS=1e0377ae

$MINER --cli="$CLI" generate --grind-cmd="$GRIND" --address="$ADDR" --nbits=$NBITS --set-block-time=1696086000
2023-11-19 18:23:42 INFO Mined block at height 1; next in -1203h13m42s (mine)

$MINER --cli="$CLI" generate --grind-cmd="$GRIND" --address="$ADDR" --nbits=$NBITS --ongoing
2023-11-19 18:24:05 INFO Mined block at height 2; next in -1203h4m5s (mine)
2023-11-19 18:24:06 INFO Mined block at height 3; next in -1202h54m5s (mine)
2023-11-19 18:24:08 INFO Mined block at height 4; next in -1202h44m8s (mine)
2023-11-19 18:24:11 INFO Mined block at height 5; next in -1202h34m11s (mine)
2023-11-19 18:24:12 INFO Mined block at height 6; next in -1202h24m12s (mine)
2023-11-19 18:24:13 INFO Mined block at height 7; next in -1202h14m13s (mine)
2023-11-19 18:24:16 INFO Mined block at height 8; next in -1202h4m16s (mine)
2023-11-19 18:24:16 INFO Mined block at height 9; next in -1201h54m16s (mine)
2023-11-19 18:24:17 INFO Mined block at height 10; next in -1201h44m16s (mine)
[Ctrl/C]

$CLI migratewallet signet
{
  "wallet_name": "signet",
  "backup_path": "/root/.bitcoin/signet/wallets/signet/signet-1700418526.legacy.bak"
}

$MINER --cli="$CLI" generate --grind-cmd="$GRIND" --address="$ADDR" --nbits=$NBITS --ongoing
PSBT signing failed

Ok, yes. Thats what I imagined.

Your challenge 512103176706ed990b936e2348392c08cfc9b7a8550d88b2b4cde4175bfb3b8af6398e51ae, is a 1-of-1 multisig of your pubkey. This script is not watched by your wallet by default, is a consensus parameter. The wallet migration process will not create the matching multisig descriptor without further instructions from your end.

You either can:

1. Import the multisig redeem script on the legacy wallet (pre-migration).
2. Import the multisig descriptor on the descriptor wallet (post-migration).

My advice for you is to create a descriptor wallet by default, not the legacy one anymore. And, if you still want to use the 1-of-1 multisig challenge; import the descriptor in the following form: multi(1, <priv_key>)#<checksum>. You can obtain the checksum by calling getdescriptorinfo "multi(1, $PRIVKEY)".

@furszy Thank you for your accurate advice. I confirmed that signet mining can be executed successfully using the second method (Import the multisig descriptor on the descriptor wallet).