Add new so-docker-prune script

* Script will pull list of so- images and prune any older than most recent + last version

salt/common/tools/sbin/so-docker-prune

@@ -0,0 +1,77 @@
+#!/usr/bin/env python3
+
+# Copyright 2014,2015,2016,2017,2018,2019,2020,2021 Security Onion Solutions, LLC
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import sys, argparse, re, docker
+from packaging.version import Version
+from itertools import groupby, chain
+
+
+def get_image_name(string) -> str:
+  return ':'.join(string.split(':')[:-1])
+
+
+def get_so_image_basename(string) -> str:
+  return get_image_name(string).split('/so-')[-1]
+
+
+def get_image_version(string) -> str:
+  ver = string.split(':')[-1]
+  if ver == 'latest':
+    # Version doesn't like "latest", so use a high semver
+    return '999999.9.9'
+  else:
+    return ver
+
+
+def main(quiet):
+  client = docker.from_env()
+
+  # Get list of non-dangling images
+  image_list = client.images.list(filters={ 'dangling': False })
+
+  # Map image objects to flattened list of tags (format: "name:version")
+  tag_list = list(chain.from_iterable(list(map(lambda x: x.attrs.get('RepoTags'), image_list))))
+
+  # Filter to only SO images (base name begins with "so-")
+  tag_list = list(filter(lambda x: re.match(r'^.*\/so-[^\/]*$', get_image_name(x)), tag_list))
+
+  # Group tags into lists by base name (sort by same projection first)
+  tag_list.sort(key=lambda x: get_so_image_basename(x))
+  grouped_tag_lists = [ list(it) for _, it in groupby(tag_list, lambda x: get_so_image_basename(x)) ]
+
+  no_prunable = True
+  for t_list in grouped_tag_lists:
+    # Keep the 2 most current images
+    t_list.sort(key=lambda x: Version(get_image_version(x)), reverse=True)
+    if len(t_list) <= 2:
+      continue
+    else:
+      no_prunable = False
+      for tag in t_list[2:]:
+        if not quiet: print(f'Removing image {tag}')
+        client.images.remove(tag)
+  
+  if no_prunable and not quiet:
+    print('No Security Onion images to prune')
+
+
+if __name__ == "__main__":
+  main_parser = argparse.ArgumentParser(add_help=False)
+  main_parser.add_argument('-q', '--quiet', action='store_const', const=True, required=False)
+  args = main_parser.parse_args(sys.argv[1:])
+ 
+  main(args.quiet)