New Blast-RADIUS Attack Breaks 30-Year-Old Protocol Used in Networks Everywhere
Freeman writes:
One of the most widely used network protocols is vulnerable to a newly discovered attack that can allow adversaries to gain control over a range of environments, including industrial controllers, telecommunications services, ISPs, and all manner of enterprise networks.
Short for Remote Authentication Dial-In User Service, RADIUS harkens back to the days of dial-in Internet and network access through public switched telephone networks. It has remained the de facto standard for lightweight authentication ever since and is supported in virtually all switches, routers, access points, and VPN concentrators shipped in the past two decades.
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The protocol was developed in 1991 by a company known as Livingston Enterprises. In 1997 the Internet Engineering Task Force made it an official standard, which was updated three years later. Although there is a draft proposal for sending RADIUS traffic inside of a TLS-encrypted session that's supported by some vendors, many devices using the protocol only send packets in clear text through UDP (User Datagram Protocol).
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Since 1994, RADIUS has relied on an improvised, home-grown use of the MD5 hash function. First created in 1991 and adopted by the IETF in 1992
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For a cryptographic hash function, it should be computationally impossible for an attacker to find two inputs that map to the same output. Unfortunately, MD5 proved to be based on a weak design: Within a few years, there were signs that the function might be more susceptible than originally thought to attacker-induced collisions, a fatal flaw that allows the attacker to generate two distinct inputs that produce identical outputs. These suspicions were formally verified in a paper published in 2004 by researchers Xiaoyun Wang and Hongbo Yu and further refined in a research paper published three years later.The latter paper-published in 2007 by researchers Marc Stevens, Arjen Lenstra, and Benne de Weger-described what's known as a chosen-prefix collision
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This type of collision attack is much more powerful because it allows the attacker the freedom to create highly customized forgeries.
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