Redacting Formatter

Sharkable provides a structured log field redaction feature that automatically masks sensitive values in ILogger output. Instead of wrapping or replacing providers, it swaps the default ILogger<T> with a redacting wrapper at the DI level — no double output, no recursion.

Quick Start

builder.Services.AddShark(opt =>
{
    opt.ConfigureRedactingLog(cfg =>
    {
        cfg.RedactFields = ["password", "secret", "token"];
    });
});

var app = builder.Build();
app.UseShark();

Every structured log call is now scanned for fields matching the configured names:

public class PaymentService(ILogger<PaymentService> logger)
{
    public void ProcessPayment(string email, string password, decimal amount)
    {
        logger.LogInformation(
            "Processing payment for {Email} with password {Password}",
            email, password);
        // Output: "Processing payment for user@test.com with password ***"
    }
}

Configuration

opt.ConfigureRedactingLog(cfg =>
{
    // Field names to redact (case-insensitive).
    // Defaults: ["password", "secret", "token", "apiKey",
    //            "authorization", "creditCard", "ssn"]
    cfg.RedactFields = ["password", "secret", "token", "apiKey"];

    // Replacement text. Default "***".
    cfg.RedactWith = "****";
});

How It Works

1. ConfigureRedactingLog() stores RedactingLogOptions globally
2. During AddCommon(), it replaces the open generic ILogger<T> registration with RedactingLogger<T>
3. RedactingLogger<T> creates an inner ILogger via ILoggerFactory and wraps it with a RedactingLogger
4. When Log<TState>() is called, the wrapper detects structured state via IReadOnlyList<KeyValuePair<string, object?>>
5. Values whose key names match the redact list are replaced in the formatted output
6. Replacements are sorted longest-first to avoid partial-value collisions

The original ILoggerProvider chain (console, file, etc.) is untouched — this is a wrapper around the ILogger<T> that each class receives.

Standalone Registration

You can also register via ILoggingBuilder directly, outside of AddShark():

builder.Logging.AddRedactingFormatter(cfg =>
{
    cfg.RedactFields = ["creditCard", "ssn"];
});

AOT Support

The implementation is fully AOT-safe. No reflection, no dynamic. The wrapper uses generic typing (ILogger<T> → RedactingLogger<T>) and interface checks (is IReadOnlyList<KeyValuePair<,>>), all of which the native AOT compiler handles correctly.

What Gets Redacted

Only structured log parameters — the named placeholders in message templates like {Password} — are checked against the redact list. Non-structured string messages pass through unmodified.

The redact list is matched by key name, not by value content. A field named {Password} is redacted regardless of its value (a short string like "x" or a long token). This avoids false positives from value-based scanning.