consttime_memequal is the same as the old consttime_bcmp.
explicit_memset is to memset as explicit_bzero was to bcmp.
Passes amd64 release and i386/ALL, but I'm sure I missed some spots,
so please let me know.
abd userland, as proposed on tech-security, with explicit_bzero using
a volatile function pointer as suggested by Alan Barrett.
Both do what the name says. For userland, both are prefixed by "__"
to keep them out of the user namespace.
Change some memset/memcmp uses to the new functions where it makes
sense -- these are just some examples, more to come.
This is an incompatible change, and will break all existing cgd images
encrypted with blowfish. Users will need to dump their data before
booting a kernel with this change, and recreate cgd's and restore data
afterwards.
I believe this affects a very small number of users other than myself;
indeed after several alert mails in an attempt to find them, only 2
such users have come forward. They have both agreed the requirement
for backwards compatibility does not warrant the effort nor the mess
in the code. This code does exist, if it should later prove to be
needed, but will not be in the tree.
Further, by the nature of the issue, I have strong reasons to believe
that, even if they missed these mails, there would be few other users
of blowfish who update their systems with any regularity; any such
users would have tripped over the problem in the same way I did when
it was first found over a year ago.
The problem stems from two issues with the underlying blowfish
encryption routines used by cgd:
- they take key length arguments counted in bytes, rather than bits
like all the opther ciphers.
- they silently truncate any keys longer than an internal limit,
rather than returning an error (which would have exposed the
previous discrepancy immediately).
As a result, the kernel reads too much data as the key from cgdconfig,
and then truncates most of it. This can easily be demonstrated/tested.
Currently, Blowfish users will find that if they mis-enter the cgd
passphrase on the first attempt, when validation fails and cgdconfig
prompts for the passphrase again, the cgd will not correctly configure
even when given a correct passphrase.
riastradh