tar.py: Fix hardlink extraction with latest Python

src/buildstream/plugins/sources/tar.py

@@ -145,14 +145,14 @@ def stage(self, directory):
                         base_dir = base_dir + os.sep
 
                 filter_function = functools.partial(self._extract_filter, base_dir)
+                filtered_members = []
+                for member in tar.getmembers():
+                    member = filter_function(member, directory)
+                    if member is not None:
+                        filtered_members.append(member)
                 if sys.version_info >= (3, 12):
-                    tar.extractall(path=directory, filter=filter_function)
+                    tar.extractall(path=directory, members=filtered_members, filter="tar")
                 else:
-                    filtered_members = []
-                    for member in tar.getmembers():
-                        member = filter_function(member, directory)
-                        if member is not None:
-                            filtered_members.append(member)
                     tar.extractall(path=directory, members=filtered_members)
 
         except (tarfile.TarError, OSError) as e:

tests/sources/tar.py

@@ -561,3 +561,48 @@ def ensure_link(member):
     result.assert_success()
     result = cli.run(project=project, args=["source", "fetch", "malicious_target.bst"])
     result.assert_main_error(ErrorDomain.STREAM, None)
+
+
+@pytest.mark.datafiles(os.path.join(DATA_DIR, "symlinks"))
+def test_symlinks(cli, tmpdir, datafiles):
+    project = str(datafiles)
+    generate_project(project, config={"aliases": {"tmpdir": "file:///" + str(tmpdir)}})
+    checkoutdir = os.path.join(str(tmpdir), "checkout")
+
+    absolute_target = "/tmp/foo"
+    relative_target = "foo/../bar"
+
+    # Create a tarball with an absolute symlink
+    src_tar = os.path.join(str(tmpdir), "contents.tar.gz")
+    old_dir = os.getcwd()
+    os.chdir(str(tmpdir))
+    os.mkdir("contents")
+    os.symlink(absolute_target, "contents/absolute-symlink")
+    os.symlink(relative_target, "contents/relative-symlink")
+    with tarfile.open(src_tar, "w:gz") as tar:
+        tar.add("contents")
+    os.chdir(old_dir)
+
+    # Make sure our tarfile is actually created with the desired attributes set
+    with tarfile.open(src_tar, "r:gz") as tar:
+        assert any(
+            member.issym() and member.path == "contents/absolute-symlink" and member.linkname == absolute_target
+            for member in tar.getmembers()
+        )
+        assert any(
+            member.issym() and member.path == "contents/relative-symlink" and member.linkname == relative_target
+            for member in tar.getmembers()
+        )
+
+    # Assert that we will allow and not mangle symlinks with relative and absolute target paths
+    result = cli.run(project=project, args=["source", "track", "target.bst"])
+    result.assert_success()
+    result = cli.run(project=project, args=["source", "fetch", "target.bst"])
+    result.assert_success()
+    result = cli.run(project=project, args=["build", "target.bst"])
+    result.assert_success()
+    result = cli.run(project=project, args=["artifact", "checkout", "target.bst", "--directory", checkoutdir])
+    result.assert_success()
+
+    assert os.readlink(checkoutdir + "/absolute-symlink") == absolute_target
+    assert os.readlink(checkoutdir + "/relative-symlink") == relative_target

tests/sources/tar/symlinks/target.bst

@@ -0,0 +1,5 @@
+kind: import
+description: The kind of this element is irrelevant.
+sources:
+- kind: tar
+  url: tmpdir:/contents.tar.gz