feat(utils): implement remove-unsafe-symlinks flag for cachi2

What/why:

implement parsing `remove-unsafe-symlinks` flag, which toggles
removing all symlinks which point to location(s) outside of any cloned
repository (default `False`)

How:

 - parse flag `remove-unsafe-symlinks` from "remote-source" section of   'container.yaml'

Signed-off-by: Ben Alkov <ben.alkov@redhat.com>

atomic_reactor/plugins/cachi2_init.py

@@ -135,7 +135,15 @@ def process_remote_sources(self) -> List[Dict[str, Any]]:
                 remote_source_data["ref"]
             )
 
-            enforce_sandbox(source_path_app, remove_unsafe_symlinks=False)
+            remove_unsafe_symlinks = False
+            flags = remote_source_data.get("flags", [])
+            if "remove-unsafe-symlinks" in flags:
+                remove_unsafe_symlinks = True
+
+            enforce_sandbox(
+                source_path_app,
+                remove_unsafe_symlinks,
+            )
             validate_paths(source_path_app, remote_source_data.get("packages", {}))
 
             if clone_only(remote_source_data):

atomic_reactor/utils/cachi2.py

@@ -23,11 +23,12 @@ class SymlinkSandboxError(Exception):
     """Found symlink(s) pointing outside the sandbox."""
 
 
-def enforce_sandbox(repo_root: Path, remove_unsafe_symlinks: bool) -> None:
+def enforce_sandbox(repo_root: Path, remove_unsafe_symlinks: bool = False) -> None:
     """
     Check that there are no symlinks that try to leave the cloned repository.
 
     :param (str | Path) repo_root: absolute path to root of cloned repository
+    :param bool remove_unsafe_symlinks: remove unsafe symlinks if any are found
     :raises OsbsValidationException: if any symlink points outside of cloned repository
     """
     for path_to_dir, subdirs, files in os.walk(repo_root):

tests/plugins/test_cachi2_init.py

@@ -6,6 +6,7 @@
 of the BSD license. See the LICENSE file for details.
 """
 
+from pathlib import Path
 from textwrap import dedent
 import os.path
 import json
@@ -35,6 +36,7 @@
 from tests.mock_env import MockEnv
 
 from tests.stubs import StubSource
+from tests.utils.test_cachi2 import Symlink, write_file_tree
 
 
 REMOTE_SOURCE_REPO = 'https://git.example.com/team/repo.git'
@@ -370,6 +372,35 @@ def test_dependency_replacements(workflow):
                          expect_error="Dependency replacements are not supported by Cachi2")
 
 
+def test_enforce_sandbox(workflow: DockerBuildWorkflow) -> None:
+    """Should remove symlink pointing outside of repository"""
+    container_yaml_config = dedent(f"""\
+            remote_source:
+              flags:
+                - remove-unsafe-symlinks
+              repo: {REMOTE_SOURCE_REPO}
+              ref: {REMOTE_SOURCE_REF}
+              pkg_managers: []
+            """)
+
+    mock_repo_config(workflow, data=container_yaml_config)
+
+    def clone_f(repo, target_dir, ref):
+        bad_symlink = Path(target_dir / 'symlink_to_root')
+        with open(target_dir / "clone.txt", "w") as f:
+            f.write(f"{repo}:{ref}")
+            f.flush()
+        write_file_tree({bad_symlink: Symlink("/")}, target_dir)
+        assert Path(target_dir / bad_symlink).exists()
+
+    mocked = flexmock(Cachi2InitPlugin)
+    mocked.should_receive('clone_remote_source').replace_with(clone_f)
+    Cachi2InitPlugin(workflow).run()
+
+    assert not Path(workflow.build_dir.path / CACHI2_BUILD_DIR / "remote-source"
+                    / CACHI2_BUILD_APP_DIR / "symlink_to_root").exists()
+
+
 def run_plugin_with_args(workflow, dependency_replacements=None, expect_error=None,
                          expect_result=True, expected_plugin_results=None):
     runner = (MockEnv(workflow)

tests/utils/test_cachi2.py

@@ -180,7 +180,7 @@ def test_remote_source_invalid_paths(tmpdir, remote_source_packages, expected_er
 
 
 def test_remote_source_path_to_symlink_out_of_repo(tmpdir):
-    """If cloned repo contains symlink that points out fo repo,
+    """If cloned repo contains symlink that points out of repo,
     path in packages shouldn't be allowed"""
     tmpdir_path = Path(tmpdir)