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.

11 files changed, 70 insertions, 96 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 4e09c86ebd..3359be8a6c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -144,6 +144,7 @@ BITCOIN_CORE_H = \
   core_memusage.h \
   cuckoocache.h \
   dbwrapper.h \
+  external_signer.h \
   flatfile.h \
   fs.h \
   httprpc.h \
@@ -267,13 +268,11 @@ BITCOIN_CORE_H = \
   wallet/crypter.h \
   wallet/db.h \
   wallet/dump.h \
-  wallet/external_signer.h \
   wallet/external_signer_scriptpubkeyman.h \
   wallet/feebumper.h \
   wallet/fees.h \
   wallet/ismine.h \
   wallet/load.h \
-  wallet/rpcsigner.h \
   wallet/rpcwallet.h \
   wallet/salvage.h \
   wallet/scriptpubkeyman.h \
@@ -387,13 +386,11 @@ libbitcoin_wallet_a_SOURCES = \
   wallet/db.cpp \
   wallet/dump.cpp \
   wallet/external_signer_scriptpubkeyman.cpp \
-  wallet/external_signer.cpp \
   wallet/feebumper.cpp \
   wallet/fees.cpp \
   wallet/interfaces.cpp \
   wallet/load.cpp \
   wallet/rpcdump.cpp \
-  wallet/rpcsigner.cpp \
   wallet/rpcwallet.cpp \
   wallet/scriptpubkeyman.cpp \
   wallet/wallet.cpp \
@@ -520,6 +517,7 @@ libbitcoin_common_a_SOURCES = \
   compressor.cpp \
   core_read.cpp \
   core_write.cpp \
+  external_signer.cpp \
   key.cpp \
   key_io.cpp \
   merkleblock.cpp \
@@ -532,6 +530,7 @@ libbitcoin_common_a_SOURCES = \
   protocol.cpp \
   psbt.cpp \
   rpc/rawtransaction_util.cpp \
+  rpc/external_signer.cpp \
   rpc/util.cpp \
   scheduler.cpp \
   script/descriptor.cpp \
diff --git a/src/wallet/external_signer.cpp b/src/external_signer.cpp
index 3396111760..b82dcc503d 100644
--- a/src/wallet/external_signer.cpp
+++ b/src/external_signer.cpp
@@ -7,7 +7,7 @@
 #include <psbt.h>
 #include <util/strencodings.h>
 #include <util/system.h>
-#include <wallet/external_signer.h>
+#include <external_signer.h>
 
 ExternalSigner::ExternalSigner(const std::string& command, const std::string& fingerprint, std::string chain, std::string name): m_command(command), m_fingerprint(fingerprint), m_chain(chain), m_name(name) {}
 
diff --git a/src/wallet/external_signer.h b/src/external_signer.h
index 4b9711107b..17428ba2f9 100644
--- a/src/wallet/external_signer.h
+++ b/src/external_signer.h
@@ -2,8 +2,8 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#ifndef BITCOIN_WALLET_EXTERNAL_SIGNER_H
-#define BITCOIN_WALLET_EXTERNAL_SIGNER_H
+#ifndef BITCOIN_EXTERNAL_SIGNER_H
+#define BITCOIN_EXTERNAL_SIGNER_H
 
 #include <stdexcept>
 #include <string>
@@ -48,7 +48,7 @@ public:
     //! @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"
-    //! @param[out] success     Boolean
+    //! @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>`.
@@ -59,7 +59,7 @@ public:
     //! 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'`)
-    //! @param[out] UniValue see doc/external-signer.md
+    //! @returns see doc/external-signer.md
     UniValue GetDescriptors(int account);
 
     //! Sign PartiallySignedTransaction on the device.
@@ -70,4 +70,4 @@ public:
 #endif
 };
 
-#endif // BITCOIN_WALLET_EXTERNAL_SIGNER_H
+#endif // BITCOIN_EXTERNAL_SIGNER_H
diff --git a/src/wallet/rpcsigner.cpp b/src/rpc/external_signer.cpp
index 696c74d665..628c684215 100644
--- a/src/wallet/rpcsigner.cpp
+++ b/src/rpc/external_signer.cpp
@@ -3,13 +3,11 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <chainparamsbase.h>
-#include <key_io.h>
+#include <external_signer.h>
 #include <rpc/server.h>
 #include <rpc/util.h>
 #include <util/strencodings.h>
-#include <wallet/rpcsigner.h>
-#include <wallet/rpcwallet.h>
-#include <wallet/wallet.h>
+#include <rpc/protocol.h>
 
 #ifdef ENABLE_EXTERNAL_SIGNER
 
@@ -33,7 +31,7 @@ static RPCHelpMan enumeratesigners()
         RPCExamples{""},
         [](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue {
             const std::string command = gArgs.GetArg("-signer", "");
-            if (command == "") throw JSONRPCError(RPC_WALLET_ERROR, "Error: restart bitcoind with -signer=<cmd>");
+            if (command == "") throw JSONRPCError(RPC_MISC_ERROR, "Error: restart bitcoind with -signer=<cmd>");
             std::string chain = gArgs.GetChainName();
             UniValue signers_res = UniValue::VARR;
             try {
@@ -46,7 +44,7 @@ static RPCHelpMan enumeratesigners()
                     signers_res.push_back(signer_res);
                 }
             } catch (const ExternalSignerException& e) {
-                throw JSONRPCError(RPC_WALLET_ERROR, e.what());
+                throw JSONRPCError(RPC_MISC_ERROR, e.what());
             }
             UniValue result(UniValue::VOBJ);
             result.pushKV("signers", signers_res);
@@ -55,54 +53,18 @@ static RPCHelpMan enumeratesigners()
     };
 }
 
-static RPCHelpMan signerdisplayaddress()
+void RegisterSignerRPCCommands(CRPCTable &t)
 {
-    return RPCHelpMan{
-        "signerdisplayaddress",
-        "Display address on an external signer for verification.\n",
-        {
-            {"address",     RPCArg::Type::STR, RPCArg::Optional::NO, /* default_val */ "", "bitcoin address to display"},
-        },
-        RPCResult{RPCResult::Type::NONE,"",""},
-        RPCExamples{""},
-        [](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue {
-            std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
-            if (!wallet) return NullUniValue;
-            CWallet* const pwallet = wallet.get();
-
-            LOCK(pwallet->cs_wallet);
-
-            CTxDestination dest = DecodeDestination(request.params[0].get_str());
-
-            // Make sure the destination is valid
-            if (!IsValidDestination(dest)) {
-                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid address");
-            }
-
-            if (!pwallet->DisplayAddress(dest)) {
-                throw JSONRPCError(RPC_WALLET_ERROR, "Failed to display address");
-            }
-
-            UniValue result(UniValue::VOBJ);
-            result.pushKV("address", request.params[0].get_str());
-            return result;
-        }
-    };
-}
-
-Span<const CRPCCommand> GetSignerRPCCommands()
-{
-
 // clang-format off
 static const CRPCCommand commands[] =
 { // category              actor (function)
   // --------------------- ------------------------
   { "signer",              &enumeratesigners,      },
-  { "signer",              &signerdisplayaddress,  },
 };
 // clang-format on
-    return MakeSpan(commands);
+    for (const auto& c : commands) {
+        t.appendCommand(c.name, &c);
+    }
 }
 
-
 #endif // ENABLE_EXTERNAL_SIGNER
diff --git a/src/rpc/register.h b/src/rpc/register.h
index 374a1e3db8..6724203ffe 100644
--- a/src/rpc/register.h
+++ b/src/rpc/register.h
@@ -19,6 +19,8 @@ void RegisterMiscRPCCommands(CRPCTable &tableRPC);
 void RegisterMiningRPCCommands(CRPCTable &tableRPC);
 /** Register raw transaction RPC commands */
 void RegisterRawTransactionRPCCommands(CRPCTable &tableRPC);
+/** Register raw transaction RPC commands */
+void RegisterSignerRPCCommands(CRPCTable &tableRPC);
 
 static inline void RegisterAllCoreRPCCommands(CRPCTable &t)
 {
@@ -27,6 +29,9 @@ static inline void RegisterAllCoreRPCCommands(CRPCTable &t)
     RegisterMiscRPCCommands(t);
     RegisterMiningRPCCommands(t);
     RegisterRawTransactionRPCCommands(t);
+#ifdef ENABLE_EXTERNAL_SIGNER
+    RegisterSignerRPCCommands(t);
+#endif // ENABLE_EXTERNAL_SIGNER
 }
 
 #endif // BITCOIN_RPC_REGISTER_H
diff --git a/src/wallet/external_signer_scriptpubkeyman.cpp b/src/wallet/external_signer_scriptpubkeyman.cpp
index a2071e521a..a113c128d7 100644
--- a/src/wallet/external_signer_scriptpubkeyman.cpp
+++ b/src/wallet/external_signer_scriptpubkeyman.cpp
@@ -3,7 +3,7 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <chainparams.h>
-#include <wallet/external_signer.h>
+#include <external_signer.h>
 #include <wallet/external_signer_scriptpubkeyman.h>
 
 #ifdef ENABLE_EXTERNAL_SIGNER
diff --git a/src/wallet/interfaces.cpp b/src/wallet/interfaces.cpp
index 23bdaa671a..64ce09d1d1 100644
--- a/src/wallet/interfaces.cpp
+++ b/src/wallet/interfaces.cpp
@@ -22,7 +22,6 @@
 #include <wallet/fees.h>
 #include <wallet/ismine.h>
 #include <wallet/load.h>
-#include <wallet/rpcsigner.h>
 #include <wallet/rpcwallet.h>
 #include <wallet/wallet.h>
 
@@ -520,17 +519,6 @@ public:
             }, command.argNames, command.unique_id);
             m_rpc_handlers.emplace_back(m_context.chain->handleRpc(m_rpc_commands.back()));
         }
-
-#ifdef ENABLE_EXTERNAL_SIGNER
-        for (const CRPCCommand& command : GetSignerRPCCommands()) {
-            m_rpc_commands.emplace_back(command.category, command.name, [this, &command](const JSONRPCRequest& request, UniValue& result, bool last_handler) {
-                JSONRPCRequest wallet_request = request;
-                wallet_request.context = &m_context;
-                return command.actor(wallet_request, result, last_handler);
-            }, command.argNames, command.unique_id);
-            m_rpc_handlers.emplace_back(m_context.chain->handleRpc(m_rpc_commands.back()));
-        }
-#endif
     }
     bool verify() override { return VerifyWallets(*m_context.chain); }
     bool load() override { return LoadWallets(*m_context.chain); }
diff --git a/src/wallet/rpcsigner.h b/src/wallet/rpcsigner.h
deleted file mode 100644
index f3ab83c428..0000000000
--- a/src/wallet/rpcsigner.h
+++ /dev/null
@@ -1,25 +0,0 @@
-// 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_WALLET_RPCSIGNER_H
-#define BITCOIN_WALLET_RPCSIGNER_H
-
-#include <span.h>
-#include <util/system.h>
-#include <vector>
-
-#ifdef ENABLE_EXTERNAL_SIGNER
-
-class CRPCCommand;
-
-namespace interfaces {
-class Chain;
-class Handler;
-}
-
-Span<const CRPCCommand> GetSignerRPCCommands();
-
-#endif // ENABLE_EXTERNAL_SIGNER
-
-#endif //BITCOIN_WALLET_RPCSIGNER_H
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 672ee3e7a4..dc821dc06d 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -4526,6 +4526,48 @@ static RPCHelpMan upgradewallet()
     };
 }
 
+#ifdef ENABLE_EXTERNAL_SIGNER
+static RPCHelpMan walletdisplayaddress()
+{
+    return RPCHelpMan{
+        "walletdisplayaddress",
+        "Display address on an external signer for verification.\n",
+        {
+            {"address",     RPCArg::Type::STR, RPCArg::Optional::NO, /* default_val */ "", "bitcoin address to display"},
+        },
+        RPCResult{
+            RPCResult::Type::OBJ,"","",
+            {
+                {RPCResult::Type::STR, "address", "The address as confirmed by the signer"},
+            }
+        },
+        RPCExamples{""},
+        [](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue {
+            std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
+            if (!wallet) return NullUniValue;
+            CWallet* const pwallet = wallet.get();
+
+            LOCK(pwallet->cs_wallet);
+
+            CTxDestination dest = DecodeDestination(request.params[0].get_str());
+
+            // Make sure the destination is valid
+            if (!IsValidDestination(dest)) {
+                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid address");
+            }
+
+            if (!pwallet->DisplayAddress(dest)) {
+                throw JSONRPCError(RPC_MISC_ERROR, "Failed to display address");
+            }
+
+            UniValue result(UniValue::VOBJ);
+            result.pushKV("address", request.params[0].get_str());
+            return result;
+        }
+    };
+}
+#endif // ENABLE_EXTERNAL_SIGNER
+
 RPCHelpMan abortrescan();
 RPCHelpMan dumpprivkey();
 RPCHelpMan importprivkey();
@@ -4602,6 +4644,9 @@ static const CRPCCommand commands[] =
     { "wallet",             &unloadwallet,                   },
     { "wallet",             &upgradewallet,                  },
     { "wallet",             &walletcreatefundedpsbt,         },
+#ifdef ENABLE_EXTERNAL_SIGNER
+    { "wallet",             &walletdisplayaddress,           },
+#endif // ENABLE_EXTERNAL_SIGNER
     { "wallet",             &walletlock,                     },
     { "wallet",             &walletpassphrase,               },
     { "wallet",             &walletpassphrasechange,         },
diff --git a/src/wallet/scriptpubkeyman.cpp b/src/wallet/scriptpubkeyman.cpp
index 9a75002b6c..149549410c 100644
--- a/src/wallet/scriptpubkeyman.cpp
+++ b/src/wallet/scriptpubkeyman.cpp
@@ -13,7 +13,7 @@
 #include <util/system.h>
 #include <util/time.h>
 #include <util/translation.h>
-#include <wallet/external_signer.h>
+#include <external_signer.h>
 #include <wallet/scriptpubkeyman.h>
 
 #include <optional>
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 192fd60dc2..5bf3c91bec 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -22,7 +22,7 @@
 #include <wallet/coinselection.h>
 #include <wallet/crypter.h>
 #include <wallet/scriptpubkeyman.h>
-#include <wallet/external_signer.h>
+#include <external_signer.h>
 #include <wallet/walletdb.h>
 #include <wallet/walletutil.h>