[metrics-team] collector bridge IP:port masking code issue?

[Iain R. Learmonth]

Hi,

On 20/10/17 20:19, nusenu wrote:
>> To ensure anonymity of bridges, all informations about
>> bridges in several files are obfuscated. In those files: data are changed, the real
>> IP address is changed into a 10/8 format, the real port and the fingerprint are
>> changed to keep anonymity of these special nodes.

This would appear to be a version of the description of what CollecTor
does, or at least what comes out of Onionoo.

>> To find a match between those files and the bridges we have extracted, we
>> have studied the source code of TOR and written a small program which con-
>> verts the fingerprint into the hashed fingerprint. The hashed fingerprint is a
>> simple SHA-1 hash of the fingerprint but format issues appeared during the
>> implementation.

It's Tor not TOR. Programs to produce SHA-1 hashes already exist.

>> The fingerprint is a 20-byte hexadecimal string which is then converted into
>> a char string. Then SHA-1 is applied and the hashed fingerprint is converted
>> again in hexadecimal. At first, we have collected different files like consensus
>> file regularly to get a list of hashed fingerprints. Automated bridge extractionenabled to have the real IP address and the real port as well as the fingerprint.

This sounds like they've abused the mail gateway or similar. With enough
time, anyone can do this. There's nothing clever going on here. I don't
know about all the limiting around it, but if you've got 4 months, I'm
not surprised you can get a lot of bridges out.

All this does is permit those bridges to be censored. Private bridges
won't be affected.

I believe BridgeDB is also written in such a way that others may be able
to run bridge authorities to distribute the bridges they run, so it's
not just one source of bridges.

Thanks,
Iain.



-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 512 bytes
Desc: OpenPGP digital signature
URL: <http://lists.torproject.org/pipermail/metrics-team/attachments/20171020/db56c16d/attachment.sig>