[tor-bugs] #19531 [Core Tor/Tor]: Major cleanup in our baseXX APIs

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#19531: Major cleanup in our baseXX APIs
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 Reporter:  dgoulet                          |          Owner:
     Type:  enhancement                      |         Status:  new
 Priority:  Medium                           |      Milestone:  Tor:
                                             |  unspecified
Component:  Core Tor/Tor                     |        Version:
 Severity:  Normal                           |     Resolution:
 Keywords:  util, tor-03-unspecified-201612  |  Actual Points:
Parent ID:                                   |         Points:  1
 Reviewer:                                   |        Sponsor:
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Comment (by catalyst):

 `REND_DESC_COOKIE_LEN_BASE64` is a special case because it's the length of
 a truncated base64 encoding (not just an unpadded one).
 `rend_auth_encode_cookie()` removes the `A` character that represents the
 low bits of the extended auth cookie that are known to be zero. This gives
 the encoded cookie different properties than a 22-byte unpadded base64
 encoding (which would ordinarily decode to 16 bytes).

 I think this is not a great situation but it's already deployed, right? We
 should probably document it better.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/19531#comment:9>
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