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