Crlf Injection in Laravel with Cockroachdb

Crlf Injection occurs when user-controlled data containing carriage return (CR, \r) and line feed (\n) characters is reflected into HTTP headers or logs without sanitization. In a Laravel application using Cockroachdb as the backend, the database itself does not introduce the injection, but the way data is handled before storage and output can expose the attack surface. If a Laravel controller directly uses request input in headers, log entries, or stored values that later influence responses, an attacker can inject malicious sequences such as %0D%0A (URL-encoded CR LF).

For example, consider a profile update form where a user provides a display name. If the application stores the raw input into a Cockroachdb table via Laravel Eloquent and later uses that value in a header or log line without validation, an attacker could submit a name like Alice\r\nX-Admin: injected. When Laravel writes this value to a log or includes it in a header via header() or a response helper, the injected CRLF can split the header, leading to header manipulation or response splitting. Cockroachdb stores the bytes as provided; the risk emerges during output handling, where the injected sequences are interpreted by downstream components such as web servers or logging pipelines.

Another scenario involves authentication tokens or session identifiers stored in Cockroachdb. If an attacker can inject CRLF into these stored values and the application later concatenates them into Set-Cookie headers or redirects, the injected lines can forge additional headers, enabling cookie poisoning or open redirects. Because Cockroachdb does not sanitize HTTP semantics, the onus is on Laravel to validate and encode user input before persistence and before any use in protocol-level constructs. The database merely persists what the application allows; the injection is realized when the tainted data is emitted into headers, logs, or other protocol-sensitive contexts.

Remediation centers on strict input validation, context-aware encoding, and avoiding direct concatenation of user input into headers or logs. For Cockroachdb-stored data, treat every retrieved value as potentially tainted and encode based on its usage context. Below are concrete Laravel code examples that demonstrate safe patterns when working with Cockroachdb via Eloquent.

1. Storing user input safely

Normalize and restrict input before saving to Cockroachdb. For a display name, strip or reject CR/LF characters at the application layer.

<?php
namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Models\Profile;

class ProfileController extends Controller
{
    public function update(Request $request, Profile $profile)
    {
        $validated = $request->validate([
            'display_name' => 'required|string|max:255',
        ]);

        // Remove CR/LF to prevent injection into headers/logs later
        $validated['display_name'] = preg_replace('/[\r\n]+/', '', $validated['display_name']);

        $profile->fill($validated);
        $profile->save(); // Cockroachdb via Laravel's DB layer

        return redirect()->back()->with('status', 'Profile updated');
    }
}

2. Using stored values in headers safely

When retrieving data from Cockroachdb for header usage, apply strict encoding. For Set-Cookie or Location headers, use Laravel's built-in helpers and avoid raw concatenation.

<?php
namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Models\Profile;

class RedirectController extends Controller
{
    public function toProfile(Profile $profile)
    {
        // Safe: use Laravel's redirect helper; do not embed user data directly in header lines
        return redirect()->route('profile.show', ['profile' => $profile->id]);
    }
}

// If you must set a custom header, encode and validate
public function customHeader(Profile $profile)
{
    $name = preg_replace('/[\r\n]+/', '', $profile->display_name);
    // Encode for header context: prevent injection by disallowing control chars
    $encoded = str_replace(['\r', '\n'], '', $name);
    header('X-Display-Name: ' . $encoded);
    return response('OK');
}

3. Logging and monitoring

When logging data from Cockroachdb, ensure log entries are structured and avoid inserting raw user input into message templates that could be later parsed as headers.

<?php
namespace App\Http\Controllers;

use Illuminate\Support\Facades\Log;
use App\Models\Profile;

class LogController extends Controller
{
    public function info(Profile $profile)
    {
        // Safe: structured logging with context, not concatenated into a line that may be parsed as headers
        Log::info('Profile viewed', [
            'profile_id' => $profile->id,
            'display_name' => $profile->display_name,
        ]);
        return response('Logged');
    }
}

4. Using Laravel middleware for early rejection

Add a global middleware to reject requests containing CR/LF in headers and body fields that map to stored values.

<?php
namespace App\Http\Middleware;

use Closure;

class RejectCrlfInput
{
    public function handle($request, Closure $next)
    {
        $input = array_merge($request->input(), $request->headers->all());
        foreach ($input as $value) {
            if (is_string($value) && preg_match('/[\r\n]/', $value)) {
                return response('Invalid characters', 400);
            }
        }
        return $next($request);
    }
}

Register this middleware in app/Http/Kernel.php to apply it across relevant routes. This prevents malicious payloads from reaching Cockroachdb or any downstream output.