Fix checksum file parsing in get_url (#53685)

* Fix checksum file parsing. Fixes #48790

* guard invalid int conversion

Co-Authored-By: sivel <matt@sivel.net>

* Remove extra newline

changelogs/fragments/get_url-checksum.yaml

@@ -0,0 +1,4 @@
+bugfixes:
+- get_url - Fix issue with checksum validation when using a file to ensure we skip lines in the file that
+  do not contain exactly 2 parts. Also restrict exception handling to the minimum number of
+  necessary lines (https://github.com/ansible/ansible/issues/48790)

lib/ansible/modules/net_tools/basics/get_url.py

@@ -487,6 +487,9 @@ def main():
     if checksum:
         try:
             algorithm, checksum = checksum.split(':', 1)
+        except ValueError:
+            module.fail_json(msg="The checksum parameter has to be in format <algorithm>:<checksum>", **result)
+
         if checksum.startswith('http://') or checksum.startswith('https://') or checksum.startswith('ftp://'):
             checksum_url = checksum
             # download checksum file to checksum_tmpsrc
@@ -494,12 +497,16 @@ def main():
             with open(checksum_tmpsrc) as f:
                 lines = [line.rstrip('\n') for line in f]
             os.remove(checksum_tmpsrc)
-                lines = dict(s.split(None, 1) for s in lines)
+            checksum_map = {}
+            for line in lines:
+                parts = line.split(None, 1)
+                if len(parts) == 2:
+                    checksum_map[parts[0]] = parts[1]
             filename = url_filename(url)
 
             # Look through each line in the checksum file for a hash corresponding to
             # the filename in the url, returning the first hash that is found.
-                for cksum in (s for (s, f) in lines.items() if f.strip('./') == filename):
+            for cksum in (s for (s, f) in checksum_map.items() if f.strip('./') == filename):
                 checksum = cksum
                 break
             else:
@@ -511,9 +518,10 @@ def main():
         # Unicode zero-width space
         checksum = re.sub(r'\W+', '', checksum).lower()
         # Ensure the checksum portion is a hexdigest
+        try:
             int(checksum, 16)
         except ValueError:
-            module.fail_json(msg="The checksum parameter has to be in format <algorithm>:<checksum>", **result)
+            module.fail_json(msg='The checksum format is invalid', **result)
 
     if not dest_is_dir and os.path.exists(dest):
         checksum_mismatch = False