p2sh – What is wrong with my script

There are a few issues with the provided Bash script for creating and signing a Bitcoin transaction using bitcoin-cli.

Here’s a detailed breakdown of the problems and suggested fixes:

Private Key Format:

Issue: The PRIVATE_KEY_1 and PRIVATE_KEY_2 are provided as 64-character hexadecimal strings. However, bitcoin-cli expects private keys in Wallet Import Format (WIF), which typically starts with a K, L, or 5 and is Base58 encoded.
Fix: Convert the hexadecimal private keys to WIF format. You can use tools like bitcoin-tool or online converters, but ensure you’re operating in a secure environment to protect the keys.

Example Conversion Using bitcoin-cli:

# Convert HEX to WIF for PRIVATE_KEY_1
WIF_PRIVATE_KEY_1=$(bitcoin-cli -regtest dumpprivkey )

# Convert HEX to WIF for PRIVATE_KEY_2
WIF_PRIVATE_KEY_2=$(bitcoin-cli -regtest dumpprivkey )

Replace and with the actual Bitcoin addresses linked to your private keys.

Invalid INPUT_TXID:

Issue: The INPUT_TXID is set to all zeroes (0000…0000), which is not a valid transaction ID. This will cause the createrawtransaction command to fail because it references a non-existent transaction.

Fix: Use a valid transaction ID from your blockchain (especially since you’re operating in regtest, ensure the transaction exists there).

Example:

INPUT_TXID="your_valid_txid_here"

ScriptPubKey Format:

Issue: The REDEEM_SCRIPT_HEX provided seems to be intended for a multisig setup, but ensure it matches the actual script of the UTXO you’re trying to spend.

Fix: Verify that the REDEEM_SCRIPT_HEX corresponds correctly to the locking script of the UTXO. If it’s a standard P2SH or P2WSH script, ensure the format aligns with expected patterns.

Deprecated signrawtransactionwithkey Command:

Issue: Depending on your bitcoin-cli version, the signrawtransactionwithkey command might be deprecated.

Fix: Use signrawtransactionwithkey if supported. Otherwise, consider using signrawtransactionwithwallet or updating your script according to the latest bitcoin-cli documentation.

Output Address Validation:

Issue: The OUTPUT_ADDRESS starts with 3, which isn’t a standard prefix on regtest. On regtest, addresses typically start with different characters.

Regtest Prefixes:

Legacy addresses start with: m or n
P2SH addresses start with: 2
Bech32 addresses start with: bcrt1

The address 325UUecEQuyrTd28Xs2hvAxdAjHM7XzqVF
does NOT conform to standard regtest address formats.

Fix: Ensure the OUTPUT_ADDRESS is a valid address for your regtest environment. You can generate a new address using:

# Generate a new legacy address in regtest
bitcoin-cli -regtest getnewaddress "" legacy

# Generate a new P2SH address in regtest
bitcoin-cli -regtest getnewaddress "" p2sh

# Generate a new bech32 address in regtest
bitcoin-cli -regtest getnewaddress "" bech32

Replace the address 325UUecEQuyrTd28Xs2hvAxdAjHM7XzqVF with an address generated directly from your regtest Bitcoin node using the commands above.

Dependencies and Tools:

Issue: The script uses jq to parse JSON. Ensure that jq is installed on your system.

Fix: Install jq if it’s not already present.

# sudo apt-get install jq

Sequence Number Usage:

Issue: The SEQUENCE is set to 0xffffffff, which is the default and might not be necessary unless you’re implementing specific features like Replace-By-Fee (RBF).

Fix: If not needed, you can omit the sequence field in the input object.

Overall Script Enhancements:

Security: Avoid hardcoding private keys in scripts. Consider using environment variables or secure key management systems.

Error Handling: Add checks to ensure each command executes successfully before proceeding to the next step. This can help in debugging issues more effectively.

Example:

# Create raw transaction
UNSIGNED_TX=$(bitcoin-cli -regtest -rpcuser=alice -rpcpassword=password createrawtransaction '[{"txid":"'$INPUT_TXID'","vout":'$INPUT_VOUT'}]' '{"'$OUTPUT_ADDRESS'":'$VALUE'}')
if [ $? -ne 0 ]; then
  echo "Failed to create raw transaction."
  exit 1
fi

# Sign transaction
SIGNED_TX=$(bitcoin-cli -regtest -rpcuser=alice -rpcpassword=password signrawtransactionwithkey "$UNSIGNED_TX" '["'$WIF_PRIVATE_KEY_1'", "'$WIF_PRIVATE_KEY_2'"]' '[{"txid":"'$INPUT_TXID'","vout":'$INPUT_VOUT',"scriptPubKey":"'$REDEEM_SCRIPT_HEX'","redeemScript":"'$REDEEM_SCRIPT_HEX'"}]')
if [ $? -ne 0 ]; then
  echo "Failed to sign transaction."
  exit 1
fi

By addressing these issues, your script should function correctly in creating and signing a Bitcoin transaction within your regtest environment.