The three functions has been modeled after the arc4random family of
functions, and they will always return random bytes.
The isc_random family of functions internally use these CSPRNG (if available):
1. getrandom() libc call (might be available on Linux and Solaris)
2. SYS_getrandom syscall (might be available on Linux, detected at runtime)
3. arc4random(), arc4random_buf() and arc4random_uniform() (available on BSDs and Mac OS X)
4. crypto library function:
4a. RAND_bytes in case OpenSSL
4b. pkcs_C_GenerateRandom() in case PKCS#11 library
Certain isc_buffer_*() functions might call memmove() with the second
argument (source) set to NULL and the third argument (length) set to 0.
While harmless, it triggers an ubsan warning:
runtime error: null pointer passed as argument 2, which is declared to never be null
Modify all memmove() call sites in lib/isc/include/isc/buffer.h and
lib/isc/buffer.c which may potentially use NULL as the second argument
(source) so that memmove() is only called if the third argument (length)
is non-zero.
compare_rdata() was meant to be used as a qsort() callback. Meanwhile,
dns_rdataslab_merge() calls compare_rdata() for a pair of dns_rdata_t
structures rather than a pair of struct xrdata structures, which is
harmless, but triggers an ubsan warning:
rdataslab.c:84:33: runtime error: member access within address <address> with insufficient space for an object of type 'const struct xrdata'
Use dns_rdata_compare() instead of compare_rdata() to prevent the
warning from being triggered.
Replace the outer for loop with a while loop to emphasize it keeps
processing the first element of diff->tuples, which changes on each
iteration due to tuples being removed from diff->tuples by
move_matching_tuples().
The ENSURE assertion at the end of dns_diff_appendminimal() is not
needed because it is placed right after code which resets *tuplep to
NULL if it is not NULL already.
The INSIST assertion in move_matching_tuples() checks the same pointer
again.
Extract the portion of the do-while loop responsible for finding the
next tuple with the same name and type into a separate function to
improve code clarity.
The do-while loop in dns__zone_updatesigs() is hard to follow due to
heavy nesting and the 'tuple' variable also being used in the outer for
loop. Add a comment to explain the purpose of the do-while loop.
Extract it into a separate function to decrease indentation and prevent
using 'tuple' in two different loops.
Add a new ATF test, sigs_test, containing everything required to start
defining test cases for dns__zone_updatesigs(). The framework is
written in a way which ensures that changes to zone database applied by
any dns__zone_updatesigs() invocation are preserved between subsequent
checks.
