external_signer: replace boost::process with cpp-subprocess

This primarily affects the `RunCommandParseJSON` utility function.

src/Makefile.am

@@ -323,6 +323,7 @@ BITCOIN_CORE_H = \
   util/sock.h \
   util/spanparsing.h \
   util/string.h \
+  util/subprocess.hpp \
   util/syserror.h \
   util/task_runner.h \
   util/thread.h \

src/common/run_command.cpp

@@ -12,39 +12,34 @@
 #include <univalue.h>
 
 #ifdef ENABLE_EXTERNAL_SIGNER
-#include <boost/process.hpp>
+#include <util/subprocess.hpp>
 #endif // ENABLE_EXTERNAL_SIGNER
 
 UniValue RunCommandParseJSON(const std::string& str_command, const std::string& str_std_in)
 {
 #ifdef ENABLE_EXTERNAL_SIGNER
-    namespace bp = boost::process;
+    namespace sp = subprocess;
 
     UniValue result_json;
-    bp::opstream stdin_stream;
+    std::istringstream stdout_stream;
-    bp::ipstream stdout_stream;
+    std::istringstream stderr_stream;
-    bp::ipstream stderr_stream;
 
     if (str_command.empty()) return UniValue::VNULL;
 
-    bp::child c(
+    auto c = sp::Popen(str_command, sp::input{sp::PIPE}, sp::output{sp::PIPE}, sp::error{sp::PIPE});
-        str_command,
-        bp::std_out > stdout_stream,
-        bp::std_err > stderr_stream,
-        bp::std_in < stdin_stream
-    );
     if (!str_std_in.empty()) {
-        stdin_stream << str_std_in << std::endl;
+        c.send(str_std_in);
     }
-    stdin_stream.pipe().close();
+    auto [out_res, err_res] = c.communicate();
+    stdout_stream.str(std::string{out_res.buf.begin(), out_res.buf.end()});
+    stderr_stream.str(std::string{err_res.buf.begin(), err_res.buf.end()});
 
     std::string result;
     std::string error;
     std::getline(stdout_stream, result);
     std::getline(stderr_stream, error);
 
-    c.wait();
+    const int n_error = c.retcode();
-    const int n_error = c.exit_code();
     if (n_error) throw std::runtime_error(strprintf("RunCommandParseJSON error: process(%s) returned %d: %s\n", str_command, n_error, error));
     if (!result_json.read(result)) throw std::runtime_error("Unable to parse JSON: " + result);
 

src/external_signer.cpp

@@ -62,12 +62,12 @@ bool ExternalSigner::Enumerate(const std::string& command, std::vector<ExternalS
 
 UniValue ExternalSigner::DisplayAddress(const std::string& descriptor) const
 {
-    return RunCommandParseJSON(m_command + " --fingerprint \"" + m_fingerprint + "\"" + NetworkArg() + " displayaddress --desc \"" + descriptor + "\"");
+    return RunCommandParseJSON(m_command + " --fingerprint " + m_fingerprint + NetworkArg() + " displayaddress --desc " + descriptor);
 }
 
 UniValue ExternalSigner::GetDescriptors(const int account)
 {
-    return RunCommandParseJSON(m_command + " --fingerprint \"" + m_fingerprint + "\"" + NetworkArg() + " getdescriptors --account " + strprintf("%d", account));
+    return RunCommandParseJSON(m_command + " --fingerprint " + m_fingerprint + NetworkArg() + " getdescriptors --account " + strprintf("%d", account));
 }
 
 bool ExternalSigner::SignTransaction(PartiallySignedTransaction& psbtx, std::string& error)
@@ -93,8 +93,8 @@ bool ExternalSigner::SignTransaction(PartiallySignedTransaction& psbtx, std::str
         return false;
     }
 
-    const std::string command = m_command + " --stdin --fingerprint \"" + m_fingerprint + "\"" + NetworkArg();
+    const std::string command = m_command + " --stdin --fingerprint " + m_fingerprint + NetworkArg();
-    const std::string stdinStr = "signtx \"" + EncodeBase64(ssTx.str()) + "\"";
+    const std::string stdinStr = "signtx " + EncodeBase64(ssTx.str());
 
     const UniValue signer_result = RunCommandParseJSON(command, stdinStr);
 

src/test/system_tests.cpp

@@ -11,7 +11,7 @@
 #include <univalue.h>
 
 #ifdef ENABLE_EXTERNAL_SIGNER
-#include <boost/process.hpp>
+#include <util/subprocess.hpp>
 #endif // ENABLE_EXTERNAL_SIGNER
 
 #include <boost/test/unit_test.hpp>
@@ -34,20 +34,16 @@ BOOST_AUTO_TEST_CASE(run_command)
         BOOST_CHECK(result.isNull());
     }
     {
-        const UniValue result = RunCommandParseJSON("echo \"{\"success\": true}\"");
+        const UniValue result = RunCommandParseJSON("echo {\"success\": true}");
         BOOST_CHECK(result.isObject());
         const UniValue& success = result.find_value("success");
         BOOST_CHECK(!success.isNull());
         BOOST_CHECK_EQUAL(success.get_bool(), true);
     }
     {
-        // An invalid command is handled by Boost
+        // An invalid command is handled by cpp-subprocess
-        const int expected_error{2};
+        const std::string expected{"execve failed: "};
-        BOOST_CHECK_EXCEPTION(RunCommandParseJSON("invalid_command"), boost::process::process_error, [&](const boost::process::process_error& e) {
+        BOOST_CHECK_EXCEPTION(RunCommandParseJSON("invalid_command"), subprocess::CalledProcessError, HasReason(expected));
-            BOOST_CHECK(std::string(e.what()).find("RunCommandParseJSON error:") == std::string::npos);
-            BOOST_CHECK_EQUAL(e.code().value(), expected_error);
-            return true;
-        });
     }
     {
         // Return non-zero exit code, no output to stderr

test/lint/lint-includes.py

@@ -30,7 +30,6 @@ EXPECTED_BOOST_INCLUDES = ["boost/date_time/posix_time/posix_time.hpp",
                            "boost/multi_index/tag.hpp",
                            "boost/multi_index_container.hpp",
                            "boost/operators.hpp",
-                           "boost/process.hpp",
                            "boost/signals2/connection.hpp",
                            "boost/signals2/optional_last_value.hpp",
                            "boost/signals2/signal.hpp",