Zcash: strtol[l] and atoi[64] have undefined behaviour on invalid input, and are locale-dependent

[daira]

We use these in contexts that should only accept ASCII digits, e.g. https://github.com/zcash/zcash/pull/1990#discussion_r99040894 . However,

"In other than the C or POSIX locales, other implementation-defined subject sequences may be accepted."

http://pubs.opengroup.org/onlinepubs/009695399/functions/strtol.html

[daira]

https://github.com/zcash/zcash/commit/a8c22cc4d1e3c55d2b2f16a72fe4130be54baaa4 is relevant but does not fix the cases mentioned in this ticket.

[daira]

Not only is it locale-dependent, it is undefined behaviour if the input is out-of-range :-( :-( :-(

[LarryRuane]

Daira, what would be the right way to fix this? Implement our own super-simple versions of these functions, so that the behaviour is obvious and well-defined (even if less feature-rich)? If so, it seems that src/utilstrencodings.cpp may be a good place for these new functions.

There are about 40 calls in all of src/ to atoi[64] or strtol[l] so this does not seem too difficult to update them all to new functions.

If it makes sense for me to work on this, please assign to me.

[daira]

Please check whether upstream Bitcoin has changed this first.