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Mitigation Strategies Analysis for serbanghita/mobile-detect

Mitigation Strategy: Use for Progressive Enhancement Only

  • Description:

    1. Identify Core Functionality: Determine essential application features that must function regardless of device.
    2. Implement Core Functionality: Build these features using standard, widely-supported web technologies. Do not use mobile-detect in this core logic.
    3. Identify Enhancement Opportunities: Determine where mobile-detect can improve the user experience (layout adjustments, optimized images, touch-friendly controls, mobile-specific content – not access restriction).
    4. Implement Enhancements: Use mobile-detect within conditional blocks to apply enhancements only if the device is detected as mobile.
    5. Ensure Fallback: Provide a default, functional experience if mobile-detect fails or returns an unexpected result. Core functionality remains accessible.
    6. Example: 
      <?php
require_once 'Mobile_Detect.php';
$detect = new Mobile_Detect;

// Core functionality (always executed)
echo "<h1>Welcome!</h1>";

// Progressive enhancement
if ($detect->isMobile()) {
    echo "<p>Mobile-optimized content.</p>";
} else {
    // Fallback
    echo "<p>Desktop content.</p>";
}
?>

  • Threats Mitigated:

    • Inaccurate Device/OS Detection: (Severity: Medium) - Reduces the impact of incorrect detection; core functionality is unaffected.

  • Impact:

    • Inaccurate Detection: Risk reduced significantly (High impact). Application remains functional.

  • Currently Implemented: (Example - Needs to be filled in based on your project)

    • Partially implemented in the user profile section.

  • Missing Implementation: (Example - Needs to be filled in based on your project)

    • Missing in the payment processing module.

Mitigation Strategy: Validate and Sanitize User-Agent Before mobile-detect

  • Description:

    1. Obtain User-Agent: Get the User-Agent header from the HTTP request.
    2. Length Check: Before passing to mobile-detect, check the length. If it exceeds a reasonable limit (e.g., 256 characters), reject or truncate. Log the event.
    3. Character Filtering (Optional/Caution): If used, do so carefully. A limited whitelist is safer than a blacklist. Focus on common characters. This is less recommended than the length check.
    4. Pass to mobile-detect: Only after validation, pass the (potentially truncated) User-Agent to mobile-detect.
    5. Example: 
      <?php
require_once 'Mobile_Detect.php';

$userAgent = $_SERVER['HTTP_USER_AGENT'] ?? '';
$maxLength = 256;

if (strlen($userAgent) > $maxLength) {
    error_log("Truncated User-Agent: " . substr($userAgent, 0, $maxLength));
    $userAgent = substr($userAgent, 0, $maxLength);
}

$detect = new Mobile_Detect;
$detect->setUserAgent($userAgent); // Set validated User-Agent

// ...
?>

  • Threats Mitigated:

    • ReDoS (Regular Expression Denial of Service): (Severity: High) - Limits malicious strings causing excessive processing.

  • Impact:

    • ReDoS: Risk reduced significantly (High impact). Length check is a strong defense.

  • Currently Implemented: (Example)

    • Not implemented.

  • Missing Implementation: (Example)

    • Missing in all application parts using mobile-detect.

Mitigation Strategy: Monitor mobile-detect Performance and Implement Timeouts

  • Description:

    1. Wrap mobile-detect Calls: Create a wrapper function around mobile-detect methods (e.g., isMobile()).
    2. Implement Timeout: Within the wrapper, enforce a strict timeout. Use a library like Symfony/Process to run mobile-detect in a separate process with a timeout (best practice). set_time_limit() is less ideal as it affects the whole script.
    3. Measure Execution Time: Record the time before and after the mobile-detect call.
    4. Log Timeouts/Long Executions: If the timeout is reached or execution exceeds a threshold (e.g., 100ms), log the event and User-Agent.
    5. Integrate with APM (Optional): Use an Application Performance Monitoring tool to track performance and set alerts.
    6. Example (simple timer - separate process is better): 
      <?php
require_once 'Mobile_Detect.php';

function isMobileWithTimeout($userAgent, $timeoutMs = 100) {
    $detect = new Mobile_Detect;
    $detect->setUserAgent($userAgent);

    $start = microtime(true);
    $isMobile = $detect->isMobile();
    $end = microtime(true);
    $duration = ($end - $start) * 1000;

    if ($duration > $timeoutMs) {
        error_log("mobile-detect timeout ($duration ms): " . $userAgent);
    }
    return $isMobile;
}

$userAgent = $_SERVER['HTTP_USER_AGENT'] ?? '';
$isMobile = isMobileWithTimeout($userAgent);
?>

  • Threats Mitigated:

    • ReDoS (Regular Expression Denial of Service): (Severity: High) - Prevents a single request from consuming excessive resources.

  • Impact:

    • ReDoS: Risk reduced significantly (High impact). Timeouts prevent long operations.

  • Currently Implemented: (Example)

    • Not implemented.

  • Missing Implementation: (Example)

    • Missing in all application parts.

Mitigation Strategy: Stay Updated and Monitor for Vulnerabilities (of mobile-detect)

  • Description:

    1. Regular Updates: Check for mobile-detect updates regularly. Automate with dependency management tools (e.g., Composer).
    2. Subscribe to Notifications: Subscribe to security advisories or mailing lists for mobile-detect vulnerability notifications.
    3. Monitor CVE Databases: Regularly check CVE databases for reported mobile-detect vulnerabilities.
    4. Prompt Patching: Update the library promptly after testing, especially for security releases.

  • Threats Mitigated:

    • ReDoS (Regular Expression Denial of Service): (Severity: High) - New versions may fix ReDoS vulnerabilities.
    • Other Unknown Vulnerabilities: (Severity: Variable) - Addresses future vulnerabilities.
    • Inaccurate Device/OS Data: (Severity: Medium)

  • Impact:

    • ReDoS/Unknown Vulnerabilities: Risk reduced significantly (High impact) by patching.
    • Inaccurate Device/OS Data: Risk reduced (Medium impact)

  • Currently Implemented: (Example)

    • Partially. Composer is used, but automatic updates aren't enabled.

  • Missing Implementation: (Example)

    • Enable automatic updates (with testing) or a more frequent manual schedule.