Add gpg_fingerprint lookup and filter (#639)

* Add gpg_fingerprint lookup.

* Work around problems on some CI targets.

* Use get_bin_path to find the gpg executable. Document that we need it.

* Improve and test error handling.

* Refactor (potentially) common code to module_utils and plugin_utils.

This will be useful to create a filter version of this, and further lookups, filters, and modules.

* Do not create a keyring when there isn't one.

* Fixups.

* Fix description.

* More fixes for lookup.

* Also add a gpg_fingerprint filter.

* Improve formulation.

Co-authored-by: Sandra McCann <samccann@redhat.com>

---------

Co-authored-by: Sandra McCann <samccann@redhat.com>

plugins/filter/gpg_fingerprint.py

@@ -0,0 +1,68 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) 2023, Felix Fontein <felix@fontein.de>
+# GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+DOCUMENTATION = """
+name: gpg_fingerprint
+short_description: Retrieve a GPG fingerprint from a GPG public or private key
+author: Felix Fontein (@felixfontein)
+version_added: 2.15.0
+description:
+  - "Takes the content of a private or public GPG key as input and returns its fingerprint."
+options:
+  _input:
+    description:
+      - The content of a GPG public or private key.
+    type: string
+    required: true
+requirements:
+  - GnuPG (C(gpg) executable)
+seealso:
+  - plugin: community.crypto.gpg_fingerprint
+    plugin_type: lookup
+"""
+
+EXAMPLES = """
+- name: Show fingerprint of GPG public key
+  ansible.builtin.debug:
+    msg: "{{ lookup('file', '/path/to/public_key.gpg') | community.crypto.gpg_fingerprint }}"
+"""
+
+RETURN = """
+  _value:
+    description:
+      - The fingerprint of the provided public or private GPG key.
+    type: string
+"""
+
+from ansible.errors import AnsibleFilterError
+from ansible.module_utils.common.text.converters import to_bytes, to_native
+from ansible.module_utils.six import string_types
+
+from ansible_collections.community.crypto.plugins.module_utils.gnupg.cli import GPGError, get_fingerprint_from_bytes
+from ansible_collections.community.crypto.plugins.plugin_utils.gnupg import PluginGPGRunner
+
+
+def gpg_fingerprint(input):
+    if not isinstance(input, string_types):
+        raise AnsibleFilterError(
+            'The input for the community.crypto.gpg_fingerprint filter must be a string; got {type} instead'.format(type=type(input))
+        )
+    try:
+        gpg = PluginGPGRunner()
+        return get_fingerprint_from_bytes(gpg, to_bytes(input))
+    except GPGError as exc:
+        raise AnsibleFilterError(to_native(exc))
+
+
+class FilterModule(object):
+    '''Ansible jinja2 filters'''
+
+    def filters(self):
+        return {
+            'gpg_fingerprint': gpg_fingerprint,
+        }