SentinelGuard 1.2.0

SentinelGuard

Defensive preflight checks for .NET desktop applications on Windows — validate paths, URLs, external binaries, ACLs, TLS certificates and your own execution location before trusting them.

Pure functions, no side effects. Every check returns a bool, with an optional out string? reason overload giving the exact rejection cause. Nothing is logged, nothing is thrown at you behind your back: you decide what to do with the reason — log it, show it, ignore it.

Verifying a binary only covers the moment before you launch it, so the package also supervises what you run — see Running what you verified.

Extracted from Chaturbate Recorder, where it guards a desktop app that launches third-party executables (yt-dlp.exe, ffmpeg.exe) against user-supplied paths and URLs.

Install

dotnet add package SentinelGuard

Targets net8.0-windows and net10.0-windows.

What it checks

Example

using SentinelGuard;

// Reject a path before touching the filesystem.
if (!PathValidator.IsValidPath(userSuppliedPath, mustExist: true, out var reason))
{
    Console.WriteLine($"Path rejected: {reason}");
    return;
}

// Reject a URL before opening a connection.
if (!UrlValidator.IsSafeUrl(url,
        allowedDomains: new[] { "example.com" },
        blacklist: Array.Empty<string>(),
        out var urlReason))
{
    Console.WriteLine($"URL rejected: {urlReason}");
    return;
}

// Refuse to launch a third-party binary that is not exactly what you expect.
if (!BinaryVerifier.VerifyTrustedBinary(toolPath, expectedSha256, out var binReason))
{
    Console.WriteLine($"Binary rejected: {binReason}");
    return;
}

Every method also has an overload without the out string? reason parameter, when you only care whether the check passed.

Running what you verified

A hash check tells you the executable is the one you expect. It says nothing about what happens next — and two failures after launch raise no exception you can catch:

• the process hangs. Still alive, producing nothing, holding its handles open. Waiting on it waits forever.
• the process spawns children. Killing the one you started leaves them running, still writing to your files.

GuardedProcessRunner covers both:

using var runner = new GuardedProcessRunner();

runner.OutputLineReceived += line => Console.WriteLine(line);
runner.StateChanged += state => Console.WriteLine($"-> {state}");

// No output for 2 minutes = hung: killed, reported as Failed.
// TimeSpan.Zero disables the watchdog for a legitimately silent process.
if (!runner.Start(toolPath, new[] { "--input", @"C:\some path\file.mkv" },
        TimeSpan.FromMinutes(2), out var reason))
{
    Console.WriteLine($"Could not start: {reason}");
    return;
}

// ...later, from anywhere:
runner.Stop();   // kills the whole tree, reports Stopped — not Failed

The final state distinguishes what a raw exit code cannot: Completed (exited 0), Failed (non-zero exit, or killed by the watchdog) and Stopped (you asked for it). Arguments are passed one element per argument, so a path containing spaces needs no escaping and cannot be split in two.

Events are raised on thread-pool threads, never on the caller's thread — marshal before touching a UI control.

LogFileRotator completes the picture for long-running captures: RotateIfTooLarge renames a log file that grew past a threshold so the caller can reopen an empty one, and PurgeOlderThan clears out old files at startup. Both swallow their failures and report through their return value — housekeeping must never take down an application.

These two are not pure functions, unlike everything above: one starts a process, the other moves files. They follow the same rule about diagnostics though — nothing is written to a log or the console, ever.

Why Windows only

AclValidator reads NTFS ACLs through System.Security.AccessControl, and BinaryVerifier / CertificateValidator rely on Authenticode and Windows certificate stores. These have no cross-platform equivalent, so the package targets -windows TFMs rather than pretending to be portable.

A note on what this is not

SentinelGuard is a set of input-validation guardrails, not a sandbox or a security boundary. It reduces the blast radius of untrusted input in a desktop app; it does not contain a hostile process. Treat it as defence in depth, layered with OS-level controls — not as a replacement for them.

License

Dual-licensed MIT OR Apache-2.0 — pick whichever suits your project.

Source, full history and issue tracker: github.com/Tomoushie/ChaturbateRecorder.