iOS Self-Root Certificates & Privacy

TL;DR

Yes, a maliciously crafted self-root certificate can spy on your iOS device’s network traffic even without a VPN or proxy. However, it requires you to install the certificate and trust it in your settings. Modern iOS versions have improved security features making this harder, but not impossible. Regularly checking and removing untrusted certificates is crucial.

Understanding Self-Root Certificates

A self-root certificate is a digital certificate that isn’t signed by a trusted Certificate Authority (CA). Normally, your iPhone trusts certificates issued by well-known CAs like Let’s Encrypt or DigiCert. A self-root certificate means someone created their own authority and is asking your phone to trust it.

How a Malicious Certificate Could Spy

1. Man-in-the-Middle (MITM) Attack: The attacker intercepts network traffic between your device and websites/services.
2. Certificate Installation: You’d need to install the malicious certificate onto your iPhone. This often happens through a fake profile or website designed to look legitimate.
3. Trusting the Certificate: Crucially, you must trust the installed certificate in your iOS settings (Settings > General > VPN & Device Management). Without trust, the certificate is useless.
4. Traffic Interception: Once trusted, all network traffic that matches the domains covered by the certificate can be intercepted and read by the attacker. This includes usernames, passwords, browsing history, and other sensitive data.

Steps to Check for & Remove Untrusted Certificates

1. Check Installed Profiles:
   • Go to Settings > General > VPN & Device Management.
   • Look for any profiles you don’t recognize or didn’t intentionally install.
   • Tap on the profile and tap Remove Profile. You will likely be asked for your passcode.
2. Check Trusted Root Certificates: (This is more advanced, but important)
   • Connect your iPhone to a computer.
   • Open Finder (macOS) or iTunes (Windows).
   • Select your device.
   • Go to the Info tab.
   • Scroll down to Profiles and click on it. If you see any profiles, review them carefully as in step 1.
3. Revoke Trust (if necessary): If you find a suspicious certificate that isn’t easily removable via Profiles, you may need to restore your iPhone from a backup (created before the certificate was installed). This is because iOS doesn’t provide an easy way to selectively remove trusted root certificates.

How Modern iOS Protects You

• Profile Installation Warnings: iOS now provides more prominent warnings when installing profiles, making it harder for attackers to trick users.
• Certificate Pinning: Many apps use certificate pinning, which means they only trust specific certificates and will refuse to connect if a different one is presented (even if trusted by the system).
• Transparency Features: iOS provides features that help detect and warn about potentially malicious configurations.

Using a VPN or Proxy

A VPN or proxy adds an extra layer of security by encrypting your traffic before it leaves your device. This means even if a malicious certificate is installed, the attacker will only see encrypted data.

Code Example (Checking Certificate Details – for advanced users)

You can use tools like openssl on a computer to examine the details of a certificate file (.cer or .pem). This requires you to first export the certificate from your iPhone (which is not straightforward).

openssl x509 -in suspicious_certificate.cer -text -noout

Final Thoughts

While iOS has improved security, it’s still important to be cautious about installing profiles and trusting certificates from unknown sources. Regularly checking your installed profiles is the best way to protect yourself.