ip6address: fix parser array bounds issue/crash

[pallas]

A malformed IP6Address, i.e. with more than 8 components, will cause the
memmove/memset at the end of parsing to fail. This code is supposed to move
the post-:: bytes to the end of the address and zero out the bytes in the
center. Instead, it moves some of the bytes the wrong way, potentially
writing prior to parts[] and then zeroing with a negative size.

Instead, make the parser stop when it hits 8 components and let parse figure
out that we did not consume the entire String.

Thanks: American Fuzzy Lop

Change-Id: I2966cb22fb5b44eb9e92dfc6a94e891cf5d02fa7

[kohler]

I'm worried this isn't right. The bottom of IP6AddressArg::basic_parse has a bunch of d != 7 cases and 8 != 7.

[pallas]

The loop right above does network conversion for d+1 items. Maybe the coloncolon thing needs more refinement, I'm not sure, but I assumed the d-- if p (not currently looking at the code) would turn the 8 into a 7. ~Derrick • iPhone

…

On Oct 3, 2018, at 6:39 AM, Eddie Kohler ***@***.***> wrote: I'm worried this isn't right. The bottom of IP6AddressArg::basic_parse has a bunch of d != 7 cases and 8 != 7. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub, or mute the thread.