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- Filename: 149-using-netinfo-data.txt
- Title: Using data from NETINFO cells
- Author: Nick Mathewson
- Created: 2-Jul-2008
- Status: Open
- Target: 0.2.1.x
- Overview
- Current Tor versions send signed IP and timestamp information in
- NETINFO cells, but don't use them to their fullest. This proposal
- describes how they should start using this info in 0.2.1.x.
- Motivation
- Our directory system relies on clients and routers having
- reasonably accurate clocks to detect replayed directory info, and
- to set accurate timestamps on directory info they publish
- themselves. NETINFO cells contain timestamps.
- Also, the directory system relies on routers having a reasonable
- idea of their own IP addresses, so they can publish correct
- descriptors. This is also in NETINFO cells.
- Learning the time and IP address
- We need to think about attackers here. Just because a router tells
- us that we have a given IP or a given clock skew doesn't mean that
- it's true. We believe this information only if we've heard it from
- a majority of the routers we've connected to recently, including at
- least 3 routers. Routers only believe this information if the
- majority includes at least one authority.
- Avoiding MITM attacks
- Current Tors use the IP addresses published in the other router's
- NETINFO cells to see whether the connection is "canonical". Right
- now, we prefer to extend circuits over "canonical" connections. In
- 0.2.1.x, we should refuse to extend circuits over non-canonical
- connections without first trying to build a canonical one.
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