Add SshSessionBackend test coverage (#1)

Adds two kinds of coverage, continuing #1's remaining scope:

1. Pure-function tests for mapSshError() and escapeForShellSingleQuotes(),
   promoted from private members to public statics purely so tests can
   call them without spinning up a process. escapeForShellSingleQuotes()
   is the actual security boundary for password auth (it's what stops a
   password containing a single quote from breaking out of the askpass
   script's quoting), so it gets a real adversarial test, not just a
   happy-path one.

2. State-machine tests (connect -> Connected, auth failure -> Failed with
   the right mapped message, connection refused -> Failed, input
   round-tripping, reconnect) driven against tests/fixtures/fake_ssh.sh,
   a small controllable stand-in for the real ssh binary, instead of a
   real network/SSH server. This needed one small testability seam: a new
   constructor overload that overrides the launched program ("ssh" in
   production, the fixture script in tests).

POSIX-only for now: the fixture is a shell script, so the state-machine
tests QSKIP on Windows until an equivalent fixture exists there; the
pure-function tests run everywhere.

RdpSessionBackend coverage is still open -- it's a bigger lift again
(FreeRDP's own event loop, not just a QProcess), left for a follow-up.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/ssh_session_backend.cpp

@@ -7,16 +7,14 @@
 #include <QTextStream>
 #include <QUuid>
 
-namespace {
+SshSessionBackend::SshSessionBackend(const Profile& profile, QObject* parent)
-QString escapeForShellSingleQuotes(const QString& value)
+    : SshSessionBackend(profile, QStringLiteral("ssh"), parent)
 {
-    QString escaped = value;
-    escaped.replace(QStringLiteral("'"), QStringLiteral("'\"'\"'"));
-    return escaped;
-}
 }
 
-SshSessionBackend::SshSessionBackend(const Profile& profile, QObject* parent)
+SshSessionBackend::SshSessionBackend(const Profile& profile,
+                                     const QString& sshProgramOverride,
+                                     QObject* parent)
     : SessionBackend(profile, parent),
       m_process(new QProcess(this)),
       m_connectedProbeTimer(new QTimer(this)),
@@ -27,7 +25,8 @@ SshSessionBackend::SshSessionBackend(const Profile& profile, QObject* parent)
       m_waitingForHostKeyConfirmation(false),
       m_passwordSubmitted(false),
       m_terminalColumns(0),
-      m_terminalRows(0)
+      m_terminalRows(0),
+      m_sshProgram(sshProgramOverride)
 {
     m_connectedProbeTimer->setSingleShot(true);
 
@@ -395,7 +394,7 @@ bool SshSessionBackend::startSshProcess(const SessionConnectOptions& options)
     args << target;
 
     m_process->setProcessEnvironment(environment);
-    m_process->setProgram(QStringLiteral("ssh"));
+    m_process->setProgram(m_sshProgram);
     m_process->setArguments(args);
     m_process->setProcessChannelMode(QProcess::SeparateChannels);
 
@@ -471,7 +470,7 @@ void SshSessionBackend::cleanupAskPassScript()
     }
 }
 
-QString SshSessionBackend::mapSshError(const QString& rawError) const
+QString SshSessionBackend::mapSshError(const QString& rawError)
 {
     const QString raw = rawError.trimmed();
     if (raw.contains(QStringLiteral("Permission denied"), Qt::CaseInsensitive)) {
@@ -510,6 +509,13 @@ QString SshSessionBackend::mapSshError(const QString& rawError) const
     return QStringLiteral("SSH connection failed.");
 }
 
+QString SshSessionBackend::escapeForShellSingleQuotes(const QString& value)
+{
+    QString escaped = value;
+    escaped.replace(QStringLiteral("'"), QStringLiteral("'\"'\"'"));
+    return escaped;
+}
+
 QString SshSessionBackend::knownHostsFileForNullDevice() const
 {
 #ifdef Q_OS_WIN

src/ssh_session_backend.h

@@ -13,8 +13,16 @@ class SshSessionBackend : public SessionBackend
 
 public:
     explicit SshSessionBackend(const Profile& profile, QObject* parent = nullptr);
+    // Test-only: overrides the executable launched instead of "ssh", so
+    // tests can point it at a controllable fixture script.
+    SshSessionBackend(const Profile& profile, const QString& sshProgramOverride, QObject* parent);
     ~SshSessionBackend() override;
 
+    // Pure, state-free helpers exposed as public statics purely so tests
+    // can exercise them directly without spinning up a real ssh process.
+    static QString mapSshError(const QString& rawError);
+    static QString escapeForShellSingleQuotes(const QString& value);
+
 public slots:
     void connectSession(const SessionConnectOptions& options) override;
     void disconnectSession() override;
@@ -46,6 +54,7 @@ private:
     bool m_passwordSubmitted;
     int m_terminalColumns;
     int m_terminalRows;
+    QString m_sshProgram;
 
     void setState(SessionState state, const QString& message);
     bool startSshProcess(const SessionConnectOptions& options);
@@ -53,7 +62,6 @@ private:
                           QProcessEnvironment& environment,
                           QString& error);
     void cleanupAskPassScript();
-    QString mapSshError(const QString& rawError) const;
     QString knownHostsFileForNullDevice() const;
     void applyTerminalSizeIfAvailable();
 };

tests/CMakeLists.txt

@@ -5,3 +5,15 @@ add_executable(test_profile_repository
 target_include_directories(test_profile_repository PRIVATE ${CMAKE_SOURCE_DIR}/src)
 target_link_libraries(test_profile_repository PRIVATE Qt6::Core Qt6::Sql Qt6::Test)
 add_test(NAME test_profile_repository COMMAND test_profile_repository)
+
+add_executable(test_ssh_session_backend
+    test_ssh_session_backend.cpp
+    ${CMAKE_SOURCE_DIR}/src/ssh_session_backend.cpp
+    ${CMAKE_SOURCE_DIR}/src/session_backend.h
+)
+target_include_directories(test_ssh_session_backend PRIVATE ${CMAKE_SOURCE_DIR}/src)
+target_link_libraries(test_ssh_session_backend PRIVATE Qt6::Core Qt6::Gui Qt6::Test)
+target_compile_definitions(test_ssh_session_backend PRIVATE
+    ORBITHUB_TEST_FIXTURES_DIR="${CMAKE_CURRENT_SOURCE_DIR}/fixtures"
+)
+add_test(NAME test_ssh_session_backend COMMAND test_ssh_session_backend)

tests/fixtures/fake_ssh.sh

@@ -0,0 +1,29 @@
+#!/bin/sh
+# Minimal, deterministic stand-in for the real `ssh` binary, used by
+# SshSessionBackend's state-machine tests so they never touch a real
+# network or SSH server. Behavior is selected by which fixture hostname
+# appears among argv (SshSessionBackend always passes the profile's
+# host, optionally as user@host, as the final argument).
+for arg in "$@"; do
+    case "$arg" in
+        *@succeed|succeed)
+            echo "Welcome to the fake host."
+            # Stay alive echoing stdin back (simulates an interactive
+            # session) until the backend terminates us.
+            while IFS= read -r line; do
+                echo "$line"
+            done
+            exit 0
+            ;;
+        *@fail-auth|fail-auth)
+            echo "Permission denied (publickey,password)." >&2
+            exit 255
+            ;;
+        *@refuse|refuse)
+            echo "ssh: connect to host refuse port 22: Connection refused" >&2
+            exit 255
+            ;;
+    esac
+done
+echo "fake_ssh.sh: no recognized fixture host in arguments: $*" >&2
+exit 1

tests/test_ssh_session_backend.cpp

@@ -0,0 +1,236 @@
+#include "ssh_session_backend.h"
+
+#include <QTest>
+
+#include <memory>
+
+#ifndef ORBITHUB_TEST_FIXTURES_DIR
+#error "ORBITHUB_TEST_FIXTURES_DIR must be defined by the build"
+#endif
+
+namespace {
+Profile makeProfile(const QString& fixtureHost)
+{
+    Profile profile;
+    profile.name = QStringLiteral("Test Profile");
+    profile.host = fixtureHost;
+    profile.port = 22;
+    profile.username = QStringLiteral("tester");
+    profile.protocol = QStringLiteral("SSH");
+    profile.authMode = QStringLiteral("Password");
+    return profile;
+}
+
+SessionConnectOptions makeOptions()
+{
+    SessionConnectOptions options;
+    options.password = QStringLiteral("dummy-password");
+    return options;
+}
+}
+
+class TestSshSessionBackend : public QObject
+{
+    Q_OBJECT
+
+private slots:
+    // Pure-function coverage -- no process involved.
+    void mapSshErrorRecognizesKnownPatterns();
+    void mapSshErrorFallsBackForUnknownText();
+    void mapSshErrorHandlesEmptyInput();
+    void escapeForShellSingleQuotesNeutralizesQuotes();
+    void escapeForShellSingleQuotesLeavesPlainTextAlone();
+
+    // State-machine coverage, driven against tests/fixtures/fake_ssh.sh
+    // instead of a real ssh binary or network.
+    void init();
+    void cleanup();
+    void successfulConnectReachesConnectedThenDisconnects();
+    void authFailureReachesFailedStateWithMappedMessage();
+    void connectionRefusedReachesFailedState();
+    void sendInputEchoesThroughOutputReceived();
+    void reconnectRestartsAndReachesConnectedAgain();
+
+private:
+    QString fixturePath() const;
+    void createBackend(const QString& fixtureHost);
+
+    std::unique_ptr<SshSessionBackend> m_backend;
+    SessionState m_lastState = SessionState::Disconnected;
+    QString m_lastErrorDisplay;
+    QString m_lastErrorRaw;
+    QString m_receivedOutput;
+};
+
+QString TestSshSessionBackend::fixturePath() const
+{
+    return QStringLiteral(ORBITHUB_TEST_FIXTURES_DIR "/fake_ssh.sh");
+}
+
+void TestSshSessionBackend::createBackend(const QString& fixtureHost)
+{
+    m_backend =
+        std::make_unique<SshSessionBackend>(makeProfile(fixtureHost), fixturePath(), nullptr);
+    connect(m_backend.get(),
+            &SessionBackend::stateChanged,
+            this,
+            [this](SessionState state, const QString&) { m_lastState = state; });
+    connect(m_backend.get(),
+            &SessionBackend::connectionError,
+            this,
+            [this](const QString& display, const QString& raw) {
+                m_lastErrorDisplay = display;
+                m_lastErrorRaw = raw;
+            });
+    connect(m_backend.get(),
+            &SessionBackend::outputReceived,
+            this,
+            [this](const QString& chunk) { m_receivedOutput += chunk; });
+}
+
+void TestSshSessionBackend::mapSshErrorRecognizesKnownPatterns()
+{
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("Permission denied (publickey,password).")),
+             QStringLiteral("Authentication failed. Check username and credentials."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("Host key verification failed.")),
+             QStringLiteral("Host key verification failed."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("ssh: Could not resolve hostname bogus")),
+             QStringLiteral("Host could not be resolved."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("ssh: connect to host x port 22: Connection timed out")),
+             QStringLiteral("Connection timed out."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("ssh: connect to host x port 22: Connection refused")),
+             QStringLiteral("Connection refused by remote host."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("ssh: connect to host x port 22: No route to host")),
+             QStringLiteral("No route to host."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("Identity file /nope not accessible: No such file.")),
+             QStringLiteral("Private key file is not accessible."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("posix_spawn: /usr/bin/ssh-askpass: No such file or directory")),
+             QStringLiteral("SSH password helper is missing or failed to launch."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("open /some/other/path: No such file or directory")),
+             QStringLiteral("Required file was not found."));
+}
+
+void TestSshSessionBackend::mapSshErrorFallsBackForUnknownText()
+{
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("some completely novel ssh error text")),
+             QStringLiteral("SSH connection failed."));
+}
+
+void TestSshSessionBackend::mapSshErrorHandlesEmptyInput()
+{
+    QCOMPARE(SshSessionBackend::mapSshError(QString()),
+             QStringLiteral("SSH connection failed for an unknown reason."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("   ")),
+             QStringLiteral("SSH connection failed for an unknown reason."));
+}
+
+void TestSshSessionBackend::escapeForShellSingleQuotesNeutralizesQuotes()
+{
+    // A password containing a single quote must not be able to break out
+    // of the single-quoted printf argument in the askpass script -- this
+    // is the actual security boundary, not just cosmetic escaping.
+    const QString malicious = QStringLiteral("pw' ; rm -rf ~ ; echo '");
+    const QString escaped = SshSessionBackend::escapeForShellSingleQuotes(malicious);
+    const QString reconstructedScriptArg = QStringLiteral("'") + escaped + QStringLiteral("'");
+    // Every single quote in the reconstructed argument must be either the
+    // outer boundary quote (open at index 0, close at the very end) or the
+    // start of a full '"'"' re-opening sequence -- never a bare, unescaped
+    // quote that could close the argument early.
+    int index = 0;
+    while (index < reconstructedScriptArg.length()) {
+        if (reconstructedScriptArg.at(index) != QChar::fromLatin1('\'')) {
+            ++index;
+            continue;
+        }
+        if (index == 0 || index == reconstructedScriptArg.length() - 1) {
+            ++index;
+            continue;
+        }
+        QCOMPARE(reconstructedScriptArg.mid(index, 5), QStringLiteral("'\"'\"'"));
+        index += 5;
+    }
+}
+
+void TestSshSessionBackend::escapeForShellSingleQuotesLeavesPlainTextAlone()
+{
+    QCOMPARE(SshSessionBackend::escapeForShellSingleQuotes(QStringLiteral("plain-password-123")),
+             QStringLiteral("plain-password-123"));
+}
+
+void TestSshSessionBackend::init()
+{
+#ifdef Q_OS_WIN
+    // fixtures/fake_ssh.sh is a POSIX shell script; there's no Windows
+    // fixture yet, so skip only the tests that actually launch it. The
+    // pure-function tests above (mapSshError*, escapeForShellSingleQuotes*)
+    // don't touch the fixture and still run everywhere.
+    const QByteArray currentTest = QTest::currentTestFunction();
+    if (!currentTest.startsWith("mapSshError") && !currentTest.startsWith("escapeForShellSingleQuotes")) {
+        QSKIP("No Windows equivalent of tests/fixtures/fake_ssh.sh yet");
+    }
+#endif
+
+    m_lastState = SessionState::Disconnected;
+    m_lastErrorDisplay.clear();
+    m_lastErrorRaw.clear();
+    m_receivedOutput.clear();
+    // Individual tests call createBackend() with the fixture host they
+    // need; most want "succeed", so provide it as the default here.
+    createBackend(QStringLiteral("succeed"));
+}
+
+void TestSshSessionBackend::cleanup()
+{
+    if (m_backend) {
+        m_backend->disconnectSession();
+    }
+    m_backend.reset();
+}
+
+void TestSshSessionBackend::successfulConnectReachesConnectedThenDisconnects()
+{
+    m_backend->connectSession(makeOptions());
+    QTRY_COMPARE(m_lastState, SessionState::Connected);
+
+    m_backend->disconnectSession();
+    QTRY_COMPARE(m_lastState, SessionState::Disconnected);
+}
+
+void TestSshSessionBackend::authFailureReachesFailedStateWithMappedMessage()
+{
+    createBackend(QStringLiteral("fail-auth"));
+    m_backend->connectSession(makeOptions());
+    QTRY_COMPARE(m_lastState, SessionState::Failed);
+    QCOMPARE(m_lastErrorDisplay, QStringLiteral("Authentication failed. Check username and credentials."));
+    QVERIFY(m_lastErrorRaw.contains(QStringLiteral("Permission denied")));
+}
+
+void TestSshSessionBackend::connectionRefusedReachesFailedState()
+{
+    createBackend(QStringLiteral("refuse"));
+    m_backend->connectSession(makeOptions());
+    QTRY_COMPARE(m_lastState, SessionState::Failed);
+    QCOMPARE(m_lastErrorDisplay, QStringLiteral("Connection refused by remote host."));
+}
+
+void TestSshSessionBackend::sendInputEchoesThroughOutputReceived()
+{
+    m_backend->connectSession(makeOptions());
+    QTRY_COMPARE(m_lastState, SessionState::Connected);
+
+    m_backend->sendInput(QStringLiteral("hello-from-test\n"));
+    QTRY_VERIFY(m_receivedOutput.contains(QStringLiteral("hello-from-test")));
+}
+
+void TestSshSessionBackend::reconnectRestartsAndReachesConnectedAgain()
+{
+    m_backend->connectSession(makeOptions());
+    QTRY_COMPARE(m_lastState, SessionState::Connected);
+
+    m_lastState = SessionState::Connecting;
+    m_backend->reconnectSession(makeOptions());
+    QTRY_COMPARE(m_lastState, SessionState::Connected);
+}
+
+QTEST_GUILESS_MAIN(TestSshSessionBackend)
+#include "test_ssh_session_backend.moc"