Move external signer out of wallet module

This commit moves the ExternalSigner class and RPC methods out of the wallet module.

The enumeratesigners RPC can be used without a wallet since #21417.
With additional modifications external signers could be used without a wallet in general, e.g. via signrawtransaction.

The signerdisplayaddress RPC is ranamed to walletdisplayaddress because it requires wallet context.
A future displayaddress RPC call without wallet context could take a descriptor argument.

This commit fixes a rpc_help.py failure when configured with --disable-wallet.

1 files changed, 73 insertions, 0 deletions

diff --git a/src/external_signer.h b/src/external_signer.h
new file mode 100644
index 0000000000..17428ba2f9
--- /dev/null
+++ b/src/external_signer.h
@@ -0,0 +1,73 @@
+// Copyright (c) 2018-2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_EXTERNAL_SIGNER_H
+#define BITCOIN_EXTERNAL_SIGNER_H
+
+#include <stdexcept>
+#include <string>
+#include <univalue.h>
+#include <util/system.h>
+
+struct PartiallySignedTransaction;
+
+class ExternalSignerException : public std::runtime_error {
+public:
+    using std::runtime_error::runtime_error;
+};
+
+//! Enables interaction with an external signing device or service, such as
+//! a hardware wallet. See doc/external-signer.md
+class ExternalSigner
+{
+private:
+    //! The command which handles interaction with the external signer.
+    std::string m_command;
+
+public:
+    //! @param[in] command      the command which handles interaction with the external signer
+    //! @param[in] fingerprint  master key fingerprint of the signer
+    //! @param[in] chain        "main", "test", "regtest" or "signet"
+    //! @param[in] name         device name
+    ExternalSigner(const std::string& command, const std::string& fingerprint, std::string chain, std::string name);
+
+    //! Master key fingerprint of the signer
+    std::string m_fingerprint;
+
+    //! Bitcoin mainnet, testnet, etc
+    std::string m_chain;
+
+    //! Name of signer
+    std::string m_name;
+
+    const std::string NetworkArg() const;
+
+#ifdef ENABLE_EXTERNAL_SIGNER
+    //! Obtain a list of signers. Calls `<command> enumerate`.
+    //! @param[in]              command the command which handles interaction with the external signer
+    //! @param[in,out] signers  vector to which new signers (with a unique master key fingerprint) are added
+    //! @param chain            "main", "test", "regtest" or "signet"
+    //! @returns success
+    static bool Enumerate(const std::string& command, std::vector<ExternalSigner>& signers, std::string chain, bool ignore_errors = false);
+
+    //! Display address on the device. Calls `<command> displayaddress --desc <descriptor>`.
+    //! @param[in] descriptor Descriptor specifying which address to display.
+    //!            Must include a public key or xpub, as well as key origin.
+    UniValue DisplayAddress(const std::string& descriptor) const;
+
+    //! Get receive and change Descriptor(s) from device for a given account.
+    //! Calls `<command> getdescriptors --account <account>`
+    //! @param[in] account  which BIP32 account to use (e.g. `m/44'/0'/account'`)
+    //! @returns see doc/external-signer.md
+    UniValue GetDescriptors(int account);
+
+    //! Sign PartiallySignedTransaction on the device.
+    //! Calls `<command> signtransaction` and passes the PSBT via stdin.
+    //! @param[in,out] psbt  PartiallySignedTransaction to be signed
+    bool SignTransaction(PartiallySignedTransaction& psbt, std::string& error);
+
+#endif
+};
+
+#endif // BITCOIN_EXTERNAL_SIGNER_H