Introduce util for locating the plugins dir

This commit adds a method to `gssapi.tests._utils`
to locate the `krb5` plugin directory.

The logic works roughly as such:

If there is a LD_LIBRARY_PATH set, start searching there.
First, assume that LD_LIBRARY_PATH refers to a normal
installation root (like '/usr/lib'), and so search for
a 'krb5/plugins' directory contain .so files somewhere
amongst its subdirectories.

If that doesn't work, assume LD_LIBRARY_PATH points right
into a krb5 source directory's lib folder, so search for a
'plugins' directory which contains .so files,
in the parent directory of LD_LIBRARY_PATH.

If no LD_LIBRARY_PATH is set, or the above fails, use the
'$(krb5-config --prefix)/lib' instead of LD_LIBRARY_PATH
in the first case.

If multiple results are found, use the shortest path.

Also-Authored-By: Robbie Harwood (frozencemetery) <rharwood@redhat.com>

Author: DirectXMan12

gssapi/tests/_utils.py

@@ -1,17 +1,13 @@
-from gssapi._utils import import_gssapi_extension
+import os
+import subprocess
 
-try:
-    import commands
-    get_output = commands.getoutput
-except ImportError:
-    import subprocess
+from gssapi._utils import import_gssapi_extension
 
-    def _get_output(*args, **kwargs):
-        res = subprocess.check_output(*args, shell=True, **kwargs)
-        decoded = res.decode('utf-8')
-        return decoded.strip()
 
-    get_output = _get_output
+def get_output(*args, **kwargs):
+    res = subprocess.check_output(*args, shell=True, **kwargs)
+    decoded = res.decode('utf-8')
+    return decoded.strip()
 
 
 def _extension_test(extension_name, extension_text):
@@ -47,3 +43,80 @@ def ext_test(self, *args, **kwargs):
         return ext_test
 
     return make_ext_test
+
+
+_PLUGIN_DIR = None
+
+
+def _find_plugin_dir():
+    global _PLUGIN_DIR
+    if _PLUGIN_DIR is not None:
+        return _PLUGIN_DIR
+
+    # if we've set a LD_LIBRARY_PATH, use that first
+    ld_path_raw = os.environ.get('LD_LIBRARY_PATH')
+    if ld_path_raw is not None:
+        # first, try assuming it's just a normal install
+
+        ld_paths = [path for path in ld_path_raw.split(':') if path]
+
+        for ld_path in ld_paths:
+            if not os.path.exists(ld_path):
+                continue
+
+            _PLUGIN_DIR = _decide_plugin_dir(
+                _find_plugin_dirs_installed(ld_path))
+            if _PLUGIN_DIR is None:
+                _PLUGIN_DIR = _decide_plugin_dir(
+                    _find_plugin_dirs_src(ld_path))
+
+            if _PLUGIN_DIR is not None:
+                break
+
+    # if there was no LD_LIBRARY_PATH, or the above failed
+    if _PLUGIN_DIR is None:
+        # if we don't have a LD_LIBRARY_PATH, just search in
+        # $prefix/lib
+
+        lib_dir = os.path.join(get_output('krb5-config --prefix'), 'lib')
+        _PLUGIN_DIR = _decide_plugin_dir(_find_plugin_dirs_installed(lib_dir))
+
+    if _PLUGIN_DIR is not None:
+        _PLUGIN_DIR = os.path.normpath(_PLUGIN_DIR)
+        return _PLUGIN_DIR
+    else:
+        return None
+
+
+def _decide_plugin_dir(dirs):
+    if dirs is None:
+        return None
+
+    # the shortest path is probably more correct
+    shortest_first = sorted(dirs, key=len)
+
+    for path in shortest_first:
+        # check to see if it actually contains .so files
+        if get_output('find %s -name "*.so"' % path):
+            return path
+
+    return None
+
+
+def _find_plugin_dirs_installed(search_path):
+    options_raw = get_output('find %s/ -type d '
+                             '-path "*/krb5/plugins"' % search_path)
+
+    if options_raw:
+        return options_raw.split('\n')
+    else:
+        return None
+
+
+def _find_plugin_dirs_src(search_path):
+    options_raw = get_output('find %s/../ -type d -name plugins' % search_path)
+
+    if options_raw:
+        return options_raw.split('\n')
+    else:
+        return None

gssapi/tests/k5test.py

@@ -37,6 +37,8 @@
 
 import six
 
+from gssapi.tests import _utils
+
 
 def _cfg_merge(cfg1, cfg2):
     if not cfg2:
@@ -85,6 +87,8 @@ def _cfg_merge(cfg1, cfg2):
             'kdc_tcp_ports': '$port0',
             'database_name': '$tmpdir/db'}},
     'dbmodules': {
+        'db_module_dir': os.path.join(_utils._find_plugin_dir(),
+                                      'kdb'),
         'db': {'db_library': 'db2', 'database_name': '$tmpdir/db'}},
     'logging': {
         'admin_server': 'FILE:$tmpdir/kadmind5.log',