Summary and Info:

Pacman v6.0.1
libalpm v13.0.1

As far as I understand, the uids member of gpgme_key_t is a linked list that may be empty, but key_search_keyserver assumes there is a valid primary user ID.


Steps to Reproduce:

1. cat /etc/pacman.d/gnupg/dirmngr.conf
keyserver hkps://keys.openpgp.org
2. sudo pacman --debug -S avisynthplus
...
checking package integrity...
debug: found cached pkg: /var/cache/pacman/pkg/avisynthplus-3.7.1.a-1-x86_64.pkg.tar.zst
debug: sig data: iHUEABYIAB0WIQSAJH2Z6r06TR46GDboW4aD60i8lQUCYevutQAKCRDoW4aD60i8lRDmAP9K/bFU4Ac/p45ke9v6aD67WLcDP4ANlI4XWsyu9rQikgEA37aFW4FaU4fyAYHf30ZsR8Iu6dSOHcUXYVlDK0VeFg8=
debug: checking signature for /var/cache/pacman/pkg/avisynthplus-3.7.1.a-1-x86_64.pkg.tar.zst
debug: 1 signatures returned
debug: fingerprint: 80247D99EABD3A4D1E3A1836E85B8683EB48BC95
debug: summary: key missing
debug: status: No public key
debug: timestamp: 1642852021
debug: exp_timestamp: 0
debug: validity: unknown; reason: Success
debug: key lookup failed, unknown key
debug: signature is not valid
debug: looking up key 80247D99EABD3A4D1E3A1836E85B8683EB48BC95 locally
debug: key lookup failed, unknown key
error: avisynthplus: key "80247D99EABD3A4D1E3A1836E85B8683EB48BC95" is unknown
:: Import PGP key 80247D99EABD3A4D1E3A1836E85B8683EB48BC95? [Y/n]
debug: looking up key 80247D99EABD3A4D1E3A1836E85B8683EB48BC95 remotely

error: segmentation fault
Please submit a full bug report with --debug if appropriate.
(full log is attached)

GDB:
>>> bt
#0 key_search_keyserver (handle=0x555555583fd0, fpr=0x5555555c3d70 "80247D99EABD3A4D1E3A1836E85B8683EB48BC95", pgpkey=0x7fffffffdeb0) at ../lib/libalpm/signing.c:356
#1 0x00007ffff7f4fca7 in _alpm_key_import (handle=0x555555583fd0, uid=0x0, fpr=0x5555555c3d70 "80247D99EABD3A4D1E3A1836E85B8683EB48BC95") at ../lib/libalpm/signing.c:529
#2 0x00007ffff7f51186 in _alpm_process_siglist (handle=0x555555583fd0, identifier=0x555555e15f10 "avisynthplus", siglist=0x5555575a2f70, optional=0, marginal=0, unknown=0) at ../lib/libalpm/signing.c:970
#3 0x00007ffff7f5597d in check_validity (handle=0x555555583fd0, total=1, total_bytes=1475983) at ../lib/libalpm/sync.c:1025
#4 0x00007ffff7f5606a in _alpm_sync_load (handle=0x555555583fd0, data=0x7fffffffe108) at ../lib/libalpm/sync.c:1173
#5 0x00007ffff7f56e58 in alpm_trans_commit (handle=0x555555583fd0, data=0x7fffffffe108) at ../lib/libalpm/trans.c:188
#6 0x000055555556cc1e in sync_prepare_execute () at ../src/pacman/sync.c:829
#7 0x000055555556c771 in sync_trans (targets=0x555555583ba0) at ../src/pacman/sync.c:728
#8 0x000055555556d0ef in pacman_sync (targets=0x555555583ba0) at ../src/pacman/sync.c:958
#9 0x000055555556875d in main (argc=3, argv=0x7fffffffe348) at ../src/pacman/pacman.c:1258
>>> print gpg_err_code(gpg_err)
$3 = GPG_ERR_NO_ERROR
>>> list 356,356
356 pgpkey->uid = key->uids->uid;
>>> print key->uids
$1 = (gpgme_user_id_t) 0x0