#!/usr/bin/bash
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
# Update all locally existing PGP keys in pacman's gnupg keyring, that are
# relevant for Arch Linux packaging using the distribution's Web Key Directory
# (WKD).
# This ensures, that new signatures on already existing keys are fetched before
# a new version of archlinux-keyring is installed. Fetching signatures early
# prevents marginal trust issues with packages that are signed by keys which
# only gain full trust when updating to a new version of archlinux-keyring in
# that same system upgrade action.

set -eu

readonly main_key_domain_match="@master-key.archlinux.org$"
readonly packager_domain_match="@archlinux.org$"
readonly homedir="$(pacman-conf GPGDir)"
# fingerprints of keys with SHA-1 self-signatures (no longer used)
readonly invalid_fingerprints=(
    0F334D8698881578F65D2AE55ED514A45BD5C938  # djgera@archlinux.org
    F4DDD6DDCEC320B665F502AAE8F18BA1615137BC  # ibiru@archlinux.org
    EA84EA00866F51FB10CD19AE426991CD8406FFF3  # ronald@archlinux.org
)

domain_match=""
gpg_locate_external=(
    # force update a key using WKD
    gpg
    --homedir
    "$homedir"
    --quiet
    --no-permission-warning
    --auto-key-locate
    "clear,nodefault,wkd"
    --locate-external-keys
)
# a list of <fingerprint> <mbox> tuples of all keys in the keyring
# e.g.:
# C7E7849466FE2358343588377258734B41C31549 dvzrv@archlinux.org
# 8FC15A064950A99DD1BD14DD39E4B877E62EB915 svenstaro@gmail.com
fingerprint_mboxes="$(
    gpg --homedir "$homedir" --no-permission-warning --list-keys --list-options show-only-fpr-mbox
)"
error=0

# a list of <fingerprints> of all revoked keys and keys that have no valid main
# key signatures
old_fingerprints="$(
    gpg --homedir "$homedir" --no-permission-warning --list-keys --with-colons |
    awk -F: '$1 == "pub" && $2 ~ /-|q|r/ { getline; print $10 }'
)"

if (( EUID != 0 )); then
     printf "This script must be run as root.\n" >&2
     exit 1
fi

# first update the main signing keys, then the packager keys
for domain_match in "$main_key_domain_match" "$packager_domain_match"; do
    while read -ra fpr_email; do
        if [[ ${fpr_email[1]} =~ $domain_match && ! "$old_fingerprints" =~ ${fpr_email[0]} && ! "${invalid_fingerprints[*]}" =~ ${fpr_email[0]} ]]; then
            printf "Refreshing key %s with UID %s...\n" "${fpr_email[0]}" "${fpr_email[1]}"
            "${gpg_locate_external[@]}" "${fpr_email[1]}" || let ++error
        else
            printf "Skipping key %s with UID %s...\n" "${fpr_email[0]}" "${fpr_email[1]}"
        fi
    done <<< "$fingerprint_mboxes"
done

exit ${error}