libparted/labels/dos.c:generate_random_id()
is used to create a new mbr_signature where none exists. The possible
return values for generate_random_id() range from 0 to 999999, derived
from the tv_usec field of gettimeofday(2).
This limits the actual value written to mbr_signature to 0.023% of the
possible uint32 values.
I don't know how many MBRs in the world libparted has written the
mbr_signature to, but the chance of collisions are greatly increased by
having an artificially restricted value.
Is there a better libc-provided rand(3)/random(3) function which can be
used to provide a full 32 bits of randomness?
I haven't checked all the other mklabel types, but it's possible they
have similar limitations. gpt.c uses uuid_generate() which delegates the
task to libuuid. Perhaps this could be used (with truncated output) for
the MBR signature?
Cheers,
Phil
