Fix creating template.rpm symlink

Create symlink using absolute path to the template rpm package.
This is important because relative path given to qvm-template should be
considered in relation to the current working directory, not
template.rpm symlink location.
This fixes calling `qvm-template install` using relative path to the
package.

Fixes QubesOS/qubes-issues#9246

qubesadmin/tests/tools/qvm_template.py

@@ -196,7 +196,8 @@ def test_004_verify_rpm_badname(self, mock_proc, mock_call, mock_ts):
 
     @mock.patch('os.path.exists')
     @mock.patch('subprocess.Popen')
-    def test_010_extract_rpm_success(self, mock_popen, mock_path_exists):
+    @mock.patch('os.symlink')
+    def test_010_extract_rpm_success(self, mock_symlink, mock_popen, mock_path_exists):
         mock_popen.return_value.__enter__.return_value = mock_popen.return_value
         pipe = mock.Mock()
         mock_popen.return_value.stdout = pipe
@@ -234,20 +235,17 @@ def test_010_extract_rpm_success(self, mock_popen, mock_path_exists):
             ]),
             mock.call().__enter__(),
             mock.call().__exit__(None, None, None),
-            mock.call([
-                'ln',
-                '-s',
-                path,
-                dirpath + '//var/lib/qubes/vm-templates/test-vm/template.rpm'
-            ]),
-            mock.call().__enter__(),
-            mock.call().__exit__(None, None, None),
+        ])
+        self.assertEqual(mock_symlink.mock_calls, [
+            mock.call(path,
+             dirpath + '//var/lib/qubes/vm-templates/test-vm/template.rpm')
         ])
         self.assertAllCalled()
 
     @mock.patch('os.path.exists')
     @mock.patch('subprocess.Popen')
-    def test_011_extract_rpm_fail(self, mock_popen, mock_path_exists):
+    @mock.patch('os.symlink')
+    def test_011_extract_rpm_fail(self, mock_symlink, mock_popen, mock_path_exists):
         for failing_call in range(1, 5):
             mock_popen.reset_mock()
             with self.subTest(failing_call=failing_call):
@@ -269,6 +267,12 @@ def side_effect(_, **__):
                 mock_popen.side_effect = side_effect
                 mock_path_exists.return_value = True
 
+                def symlink_side_effect(_s, _d):
+                    if failing_call >= 4:
+                        raise OSError("Error")
+                    return None
+                mock_symlink.side_effect = symlink_side_effect
+
                 with tempfile.NamedTemporaryFile() as fd, \
                         tempfile.TemporaryDirectory() as tmpdir:
                     path = fd.name
@@ -302,16 +306,6 @@ def side_effect(_, **__):
                     ]),
                     mock.call().__enter__(),
                     mock.call().__exit__(None, None, None),
-                ]) + ([] if failing_call < 4 else [
-                    mock.call([
-                        'ln',
-                        '-s',
-                        path,
-                        dirpath
-                        + '//var/lib/qubes/vm-templates/test-vm/template.rpm'
-                    ]),
-                    mock.call().__enter__(),
-                    mock.call().__exit__(None, None, None),
                 ]))
                 self.assertAllCalled()
 

qubesadmin/tools/qvm_template.py

@@ -768,11 +768,13 @@ def extract_rpm(name: str, path: str, target: str) -> bool:
         if truncate.returncode != 0:
             return False
         # and create rpm file symlink
-        with subprocess.Popen([
-            'ln', '-s', path, f'{target}/{PATH_PREFIX}/{name}/template.rpm'
-        ]) as symlink:
-            pass
-        if symlink.returncode != 0:
+        link_path = f'{target}/{PATH_PREFIX}/{name}/template.rpm'
+        try:
+            os.symlink(os.path.abspath(path),
+                       f'{target}/{PATH_PREFIX}/{name}/template.rpm')
+        except OSError as e:
+            print(f"Failed to create {link_path} symlink: {e!s}",
+                  file=sys.stderr)
             return False
     return True