SSL proxy bypass is a mechanism used within SSL forward proxies where a URL is either intercepted or explicitly bypassed based on predefined lists. The proxy checks if a URL matches an entry in either an "intercept list" (for decrypting and inspecting traffic) or a "bypass list" (for skipping decryption and inspection).
Here's a breakdown:
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How it Works: The SSL forward proxy examines each URL. It compares the URL against its configured lists. The first match found dictates the action.
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Intercept List: If the URL is found on this list, the proxy decrypts the SSL traffic, allowing it to inspect the contents. This is typically used for security purposes, such as malware scanning or data loss prevention.
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Bypass List: If the URL is found on this list, the proxy does not decrypt the SSL traffic. The traffic passes through without inspection. This is often used for performance reasons (to reduce the load on the proxy) or for compatibility with sites that might not work correctly with SSL interception.
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Default Action: If the URL doesn't match any entry on either the intercept or bypass list, the proxy applies its default action, which is typically either to intercept or bypass, depending on the overall configuration of the proxy.
In simpler terms: Think of an SSL proxy as a customs agent at a border.
- Intercept List: This is a list of people flagged for closer inspection.
- Bypass List: This is a list of people who are allowed to pass through without inspection.
- Default Action: If someone is not on either list, the customs agent has a default procedure – either check their luggage (intercept) or wave them through (bypass).
Example Scenario:
A company might configure its SSL proxy to:
- Intercept traffic to known file-sharing websites (to prevent unauthorized data exfiltration).
- Bypass traffic to online banking websites (to avoid potential compatibility issues or privacy concerns).
- Default to intercepting all other SSL traffic (for malware scanning).
Key Takeaway: SSL proxy bypass provides granular control over which SSL traffic is decrypted and inspected, allowing organizations to balance security, performance, and compatibility. The bypass list takes precedence in that the first match dictates the action.
