Merge #21467: Move external signer out of wallet module

88d4d5ff2f5c71a9a2f4c78c2b2e2fd00568cfee rpc: add help for enumeratesigners and walletdisplayaddress (Sjors Provoost)
b0db187e5b30a491c9f95685430a82a1e35e921d ci: use --enable-external-signer instead of --with-boost-process (Sjors Provoost)
b54b2e7b1a171203404bd41853372c73f2c64532 Move external signer out of wallet module (Sjors Provoost)

Pull request description:

  In addition, this PR enables external signer testing on CI.

  This PR 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`.

ACKs for top commit:
  ryanofsky:
    Code review ACK 88d4d5ff2f5c71a9a2f4c78c2b2e2fd00568cfee
  fanquake:
    ACK 88d4d5ff2f5c71a9a2f4c78c2b2e2fd00568cfee

Tree-SHA512: 3242a24e22313aed97eee32a520bfcb1c17495ba32a2b8e06a5e151e2611320e2da5ef35b572d84623af0a49a210d2f9377a2531250868d1a0ccf3e144352a97

2 files changed, 78 insertions, 0 deletions

diff --git a/src/rpc/external_signer.cpp b/src/rpc/external_signer.cpp
new file mode 100644
index 0000000000..0f8f197ad8
--- /dev/null
+++ b/src/rpc/external_signer.cpp
@@ -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.
+
+#include <chainparamsbase.h>
+#include <external_signer.h>
+#include <rpc/server.h>
+#include <rpc/util.h>
+#include <util/strencodings.h>
+#include <rpc/protocol.h>
+
+#ifdef ENABLE_EXTERNAL_SIGNER
+
+static RPCHelpMan enumeratesigners()
+{
+    return RPCHelpMan{"enumeratesigners",
+        "Returns a list of external signers from -signer.",
+        {},
+        RPCResult{
+            RPCResult::Type::OBJ, "", "",
+            {
+                {RPCResult::Type::ARR, "signers", /* optional */ false, "",
+                {
+                    {RPCResult::Type::STR_HEX, "masterkeyfingerprint", "Master key fingerprint"},
+                    {RPCResult::Type::STR, "name", "Device name"},
+                },
+                }
+            }
+        },
+        RPCExamples{
+            HelpExampleCli("enumeratesigners", "")
+            + HelpExampleRpc("enumeratesigners", "")
+        },
+        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
+        {
+            const std::string command = gArgs.GetArg("-signer", "");
+            if (command == "") throw JSONRPCError(RPC_MISC_ERROR, "Error: restart bitcoind with -signer=<cmd>");
+            std::string chain = gArgs.GetChainName();
+            UniValue signers_res = UniValue::VARR;
+            try {
+                std::vector<ExternalSigner> signers;
+                ExternalSigner::Enumerate(command, signers, chain);
+                for (ExternalSigner signer : signers) {
+                    UniValue signer_res = UniValue::VOBJ;
+                    signer_res.pushKV("fingerprint", signer.m_fingerprint);
+                    signer_res.pushKV("name", signer.m_name);
+                    signers_res.push_back(signer_res);
+                }
+            } catch (const ExternalSignerException& e) {
+                throw JSONRPCError(RPC_MISC_ERROR, e.what());
+            }
+            UniValue result(UniValue::VOBJ);
+            result.pushKV("signers", signers_res);
+            return result;
+        }
+    };
+}
+
+void RegisterSignerRPCCommands(CRPCTable &t)
+{
+// clang-format off
+static const CRPCCommand commands[] =
+{ // category              actor (function)
+  // --------------------- ------------------------
+  { "signer",              &enumeratesigners,      },
+};
+// clang-format on
+    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