Vulnerabilities in SSL & TLS :- FREAK

Main Points

• In the 1990s, the US government established rules governing the strength of encryption that could be exported (“Export keys”).
• In any Secure Socket Layer (SSL) implementations aimed at export, these rules limited the strength of the RSA encryption keys to a maximum of 512 bits.
• The RSA Export keys were designed to allow exports to contain encryption that could not be broken by a typical computing resource but could be broken by the NSA.
• For this attack to work, the attacker must use a different exploit to become a person-in-the-middle and inject content into the network traffic stream.
• The FREAK attack necessitates a person-in-the-middle position in order to change the initial HTTP packet that is sent out when negotiating cipher use to request “Export Keys.”
• The use of “Export Keys” suites was stopped, and by the year 2000, browsers could use a higher-security SSL.
• Attack Narrative
  1. An attacker gains a person-in-the-middle position between two computers.
  2. Victim requests a secure connection to a webpage. The victims browser sends a “Client Hello message” to the server asking for typical cipher suites.
  3. The attacker intercepts the conversation and substitutes the requested cipher suites with a request for ‘export RSA’
  4. The server agrees and accepts the request (not understanding that it was modified). It responds with a 512-bit export RSA key.
  5. The client accepts ‘export RSA’ (not understanding that its request was modified).
  6. Attacker breaks weaker keys (first done by a researcher in 1999, modern cloud computing makes this much easier) and obtains information.

Quick Reference

Abbreviation

FREAK

Name

Factoring RSA Export Keys

CVE Number

CVE-2015-0204

Type of Vulnerability

The vulnerability is in the ciphers with which the system is willing to communicate. They cannot be negotiated if the weak cipher is removed. It is a simple fix.

Affected

Any system willing to negotiate RSA Export Keys.

Remediation

Disable support for weak export-grade ciphers

Mediation

Remove any weak ciphers from your configuration. Refuse to communicate using weak ciphers. This way the person-in-the-middle cipher negotiation cannot be modified to support RSA Export Keys.