Re: [9front] Totp in factotum

[cinap_lenrek@felloff.net]

> I guess I need a heads up there. When decoding the base32 encoded binary data,
> how would I know how many bytes I need?
> Should I just assume that a buffer of length 1024 is enough,
> or count on dec32 to give me a result and allocate more memory if I need it?

from the manpage:

         Dec16, dec32 and dec64 return the number of bytes decoded or
          -1 if the decoding fails.  The decoding fails if the output
          buffer is not large enough or, for base 32, if the input
          buffer length is not a multiple of 8.

just using the return value and a fixed 1024 sized buffer is probably fine.
my concern was about the secret containing 0x00 bytes.

otherwise, you can estimate the size by taking the string length of
the input like (strlen(input)*5+8)/8 or something and allocate it.

> For compatibility, does it make sense to write my own enc32 encoding function,
> just in case the default changes?

there is a dec32x() function that you can pass a character converting
function wich maps the alphabet.

see the HISTORY section in the manpage, if they use RFC4648 then
you should be fine. it will break with labs plan9 tho as they still use
the custom plan9 alphabet by default and also have no dec32x() function.

     HISTORY
          In Jan 2018, base 32 encoding was changed from non-standard
          to standard RFC4648 alphabet.

          old: 23456789abcdefghijkmnpqrstuvwxyz

          new: ABCDEFGHIJKLMNOPQRSTUVWXYZ234567

--
cinap