Signing a standalone message with a wallet key

1// Copyright (c) 2011-present The Bitcoin Core developers
2// Distributed under the MIT software license, see the accompanying
3// file COPYING or http://www.opensource.org/licenses/mit-license.php.
4
5#include <common/signmessage.h>
6#include <key_io.h>
7#include <rpc/util.h>
8#include <wallet/rpc/util.h>
9#include <wallet/wallet.h>
10
11#include <univalue.h>
12
13namespace wallet {
14RPCMethod signmessage()
15{
16    return RPCMethod{
17        "signmessage",
18        "Sign a message with the private key of an address" +
19          HELP_REQUIRING_PASSPHRASE,
20        {
21            {"address", RPCArg::Type::STR, RPCArg::Optional::NO, "The bitcoin address to use for the private key."},
22            {"message", RPCArg::Type::STR, RPCArg::Optional::NO, "The message to create a signature of."},
23        },
24        RPCResult{
25            RPCResult::Type::STR, "signature", "The signature of the message encoded in base 64"
26        },
27        RPCExamples{
28            "\nUnlock the wallet for 30 seconds\n"
29            + HelpExampleCli("walletpassphrase", "\"mypassphrase\" 30") +
30            "\nCreate the signature\n"
31            + HelpExampleCli("signmessage", "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\" \"my message\"") +
32            "\nVerify the signature\n"
33            + HelpExampleCli("verifymessage", "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\" \"signature\" \"my message\"") +
34            "\nAs a JSON-RPC call\n"
35            + HelpExampleRpc("signmessage", "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\", \"my message\"")
36        },
37        [](const RPCMethod& self, const JSONRPCRequest& request) -> UniValue
38        {
39            const std::shared_ptr<const CWallet> pwallet = GetWalletForJSONRPCRequest(request);
40            if (!pwallet) return UniValue::VNULL;
41
42            LOCK(pwallet->cs_wallet);
43
44            EnsureWalletIsUnlocked(*pwallet);
45
46            std::string strAddress = request.params[0].get_str();
47            std::string strMessage = request.params[1].get_str();
48
49            CTxDestination dest = DecodeDestination(strAddress);
50            if (!IsValidDestination(dest)) {
51                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid address");
52            }
53
54            const PKHash* pkhash = std::get_if<PKHash>(&dest);
55            if (!pkhash) {
56                throw JSONRPCError(RPC_TYPE_ERROR, "Address does not refer to key");
57            }
58
59            std::string signature;
60            SigningResult err = pwallet->SignMessage(strMessage, *pkhash, signature);
61            if (err == SigningResult::SIGNING_FAILED) {
62                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, SigningResultString(err));
63            } else if (err != SigningResult::OK) {
64                throw JSONRPCError(RPC_WALLET_ERROR, SigningResultString(err));
65            }
66
67            return signature;
68        },
69    };
70}
71} // namespace wallet
72