CVE-2007-1103 in Tor
Summary
by MITRE
Tor does not verify a node s uptime and bandwidth advertisements, which allows remote attackers who operate a low resource node to make false claims of greater resources, which places the node into use for many circuits and compromises the anonymity of traffic sources and destinations.
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Analysis
by VulDB Data Team • 08/20/2018
The vulnerability described in CVE-2007-1103 represents a critical weakness in the Tor network's resource verification mechanisms that fundamentally undermines the anonymity infrastructure. This flaw exists within the Tor protocol's node advertisement system where routers fail to authenticate or validate the uptime and bandwidth claims made by participating nodes. The vulnerability stems from the absence of cryptographic verification or cross-checking mechanisms that would normally ensure node operators cannot fabricate their resource capabilities.
Tor operates on a distributed network of relays where nodes advertise their available bandwidth and uptime to help the network select appropriate paths for circuit creation. When a node falsely advertises high bandwidth or extended uptime, it becomes more attractive for routing traffic and can be included in many more circuits than its actual capabilities would justify. This creates a situation where malicious actors can manipulate the network's path selection algorithm to route traffic through their compromised nodes, potentially enabling traffic analysis attacks and deanonymization.
The technical flaw can be categorized under CWE-347 as it involves insufficient verification of data integrity and authenticity. The vulnerability allows for a form of resource manipulation that directly impacts the network's security properties, enabling attackers to exploit the trust model inherent in Tor's design. This issue particularly aligns with ATT&CK technique T1583.002 which involves subverting trust relationships through false resource claims.
The operational impact of this vulnerability is significant as it allows attackers to compromise the anonymity of Tor users by strategically placing malicious nodes in high-traffic paths. When a low-resource node falsely advertises high capabilities, it can be selected for numerous circuits, creating a disproportionate influence over traffic routing. This manipulation can lead to traffic correlation attacks where an attacker can monitor traffic patterns and potentially identify source and destination nodes, effectively breaking the anonymity guarantees that Tor provides.
Mitigation strategies should focus on implementing cryptographic verification mechanisms for node advertisements, including digital signatures that can be validated by other network participants. The network should also implement reputation systems that track node behavior over time and cross-reference advertised capabilities with actual performance metrics. Additionally, implementing rate limiting for bandwidth claims and establishing more robust peer validation mechanisms would help prevent the exploitation of this vulnerability. The Tor Project's subsequent implementations have addressed similar issues through enhanced certificate validation and more rigorous node verification processes that ensure advertised resources accurately reflect actual node capabilities.