AddressSanitizer: stack-use-after-scope in dns_tsig_verify (dns_message_checksig test)

Summary

ASAN error:

testing 63 bytes from /builds/isc-projects/bind9/fuzz/dns_message_checksig.in/tsig-reply
=================================================================
==1074==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7ffe14b1d780 at pc 0x55eeaf01c3ff bp 0x7ffe14b1c990 sp 0x7ffe14b1c160
READ of size 12 at 0x7ffe14b1d780 thread T0
    #0 0x55eeaf01c3fe in __asan_memmove (/builds/isc-projects/bind9/fuzz/.libs/dns_message_checksig+0xa63fe) (BuildId: 73cf12c5424a9fda378fddea924b696e6cb966ca)
    #1 0x7f93f3d6a227 in memmove /usr/include/x86_64-linux-gnu/bits/string_fortified.h:40:10
    #2 0x7f93f3d6a227 in dns_tsig_verify /builds/isc-projects/bind9/lib/dns/tsig.c:1241:3
    #3 0x7f93f3dd122d in dns_view_checksig /builds/isc-projects/bind9/lib/dns/view.c:1471:10
    #4 0x7f93f38f42a8 in dns_message_checksig /builds/isc-projects/bind9/lib/dns/message.c:3145:12
    #5 0x55eeaf058c18 in LLVMFuzzerTestOneInput /builds/isc-projects/bind9/fuzz/dns_message_checksig.c:393:11
    #6 0x55eeaf05c189 in test_one_file /builds/isc-projects/bind9/fuzz/main.c:53:3
    #7 0x55eeaf05c468 in test_all_from /builds/isc-projects/bind9/fuzz/main.c:89:3
    #8 0x55eeaf05bc18 in main /builds/isc-projects/bind9/fuzz/main.c:130:2
    #9 0x7f93f2dc5d09 in __libc_start_main csu/../csu/libc-start.c:308:16
    #10 0x55eeaef9a569 in _start (/builds/isc-projects/bind9/fuzz/.libs/dns_message_checksig+0x24569) (BuildId: 73cf12c5424a9fda378fddea924b696e6cb966ca)

Jobs:

• https://gitlab.isc.org/isc-projects/bind9/-/jobs/2793490: test-suite.log
• https://gitlab.isc.org/isc-projects/bind9/-/jobs/2793597: test-suite.log

BIND version used

4108d79c (!6822 (merged)), but change in this MR affects only tests.

Steps to reproduce

Run unit:clang:asan job in CI.

What is the current bug behavior?