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Created attachment 1519858 [details]
crash input files and gdb backtrace of p11-kit-0.23.5-3.el7.x86_64

Description of problem:
As subject

Version-Release number of selected component (if applicable):
p11-kit-0.23.14-4.el8.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Prepare a file:
# cat /tmp/crashes/id:000000,sig:06,src:000066,op:ext_AO,pos:6 
1-----BEGIN ------------#

2. Run following command:
# trust anchor /tmp/crashes/id:000000,sig:06,src:000066,op:ext_AO,pos:6
trust: trust/pem.c:87: pem_find_begin: Assertion `suff > pref' failed.
[1]    21880 abort (core dumped)  trust anchor /tmp/crashes/id:000000,sig:06,src:000066,op:ext_AO,pos:6

Actual results:
As above

Expected results:
No SIGABRT

Additional info:
It could be reproduced on p11-kit-0.23.5-3.el7.x86_64 and upstream 0.23.14-27-g5e6a92b.
The crash input files and gdb backtrace of p11-kit-0.23.5-3.el7.x86_64  are in attachment.
This bug is find by afl.

Thank you for running afl against the package.  However, I wouldn't call it a bug, but just an assertion failure.  
As we don't compile it with NDEBUG=1 in RHEL, there shouldn't be a practical problem.

If you suggest to make the error handling more courteous, feel free to open an upstream issue.

Sorry, after a second thought, I realized that you are right: the assert condition itself is wrong and the parser should accept such PEM header.  I have opened a PR:
https://github.com/p11-glue/p11-kit/pull/210

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Moderate: p11-kit security, bug fix, and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2021:1609