[tor-bugs] #17728 [Tor]: Use NETINFO handshake rather than date header to check time with authorities (was: Use TLS handshake rather than date header to check time with authorities)

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#17728: Use NETINFO handshake rather than date header to check time with
authorities
-------------------------+------------------------------------
 Reporter:  teor         |          Owner:
     Type:  enhancement  |         Status:  new
 Priority:  Medium       |      Milestone:  Tor: 0.2.9.x-final
Component:  Tor          |        Version:
 Severity:  Normal       |     Resolution:
 Keywords:               |  Actual Points:
Parent ID:  #9675        |         Points:
 Reviewer:               |        Sponsor:
-------------------------+------------------------------------
Description changed by nickm:

Old description:

> tor currently checks its clock against the directory authorities by
> reading the HTTP date header in the directory documents.
>
> In #15775, we allow clients to bootstrap using fallback directories,
> rather than authorities.
>
> In #4483, we make multiple connections, and use the first connection that
> starts downloading. If there are multiple connections downloading, we
> favour authority connections, so that tor can still get a clock check.
>
> But if tor used the date from the TLS handshake, it could abort authority
> connections sooner. This would place less load on the authorities.
>
> This would be similar to the tlsdate implementation:
> https://github.com/ioerror/tlsdate

New description:

 tor currently checks its clock against the directory authorities by
 reading the HTTP date header in the directory documents.

 In #15775, we allow clients to bootstrap using fallback directories,
 rather than authorities.

 In #4483, we make multiple connections, and use the first connection that
 starts downloading. If there are multiple connections downloading, we
 favour authority connections, so that tor can still get a clock check.

 But if tor used the date from ~~the TLS handshake~~, it could abort
 authority connections sooner. This would place less load on the
 authorities.

 This would be similar to the tlsdate implementation:
 https://github.com/ioerror/tlsdate

 Edited: Look at the netinfo cell, not the TLS handshake. -- nickm

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/17728#comment:3>
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