| """Reconstruct declared source bases and verify exact Git identities.""" |
| import hashlib |
| import json |
| import os |
| from pathlib import Path, PurePosixPath |
| import re |
| import subprocess |
| import tempfile |
| from common import ROOT, contained, sha256 |
|
|
|
|
| def object_id(kind, content): |
| return hashlib.sha1(kind.encode() + b" " + str(len(content)).encode() + b"\0" + content).hexdigest() |
|
|
|
|
| def relative_path(value): |
| path = PurePosixPath(value) |
| if path.is_absolute() or not path.parts or ".." in path.parts or ".git" in path.parts: |
| raise ValueError(f"Unsafe source transformation path: {value}") |
| return str(path) |
|
|
|
|
| def construct(repo, cache, recipe_path): |
| recipe = json.loads(Path(recipe_path).read_text()) |
| if recipe["schema_version"] != 1 or recipe["kind"] != "git-tree-transform-v1": |
| raise ValueError("Unsupported source construction recipe") |
| if recipe["expected_commit"] != repo["base_commit"]: |
| raise ValueError("Construction recipe changes the task source identity") |
| revision = recipe["upstream_base_commit"] |
| if not re.fullmatch(r"[0-9a-f]{40}", revision): |
| raise ValueError("Invalid upstream construction revision") |
| task_root = Path(recipe_path).resolve().parents[2] |
| ref = recipe["commit_object"] |
| commit_path = contained(task_root, ref["path"]) |
| if sha256(commit_path) != ref["sha256"]: |
| raise ValueError("Synthetic commit metadata changed") |
| commit = commit_path.read_bytes() |
| if object_id("commit", commit) != repo["base_commit"]: |
| raise ValueError("Synthetic commit object does not match the declared base") |
| header = commit.split(b"\n\n", 1)[0].splitlines() |
| parents = [line[7:].decode() for line in header if line.startswith(b"parent ")] |
| declared_parents = recipe.get("parents", []) |
| if declared_parents not in ([], [revision]) or parents != declared_parents: |
| raise ValueError("Construction commit parents must exactly match the declared upstream base or empty root") |
| if [line for line in header if line.startswith(b"tree ")] != [b"tree " + recipe["expected_tree"].encode()]: |
| raise ValueError("Construction commit does not declare its exact expected tree") |
| exists = subprocess.run(["git", "-C", str(cache), "cat-file", "-e", revision + "^{commit}"], stderr=subprocess.DEVNULL).returncode == 0 |
| if not exists: |
| subprocess.run(["git", "-C", str(cache), "fetch", "--depth=1", "--no-tags", repo["url"], revision], check=True) |
| with tempfile.TemporaryDirectory(prefix="crossswe-source-index-") as temporary: |
| environment = dict(os.environ, GIT_INDEX_FILE=str(Path(temporary) / "index"), GIT_WORK_TREE=temporary) |
|
|
| def git(*args, content=None): |
| return subprocess.check_output(["git", "-C", str(cache), *args], env=environment, input=content) |
|
|
| git("read-tree", revision + "^{tree}") |
| for operation in recipe["operations"]: |
| if operation["kind"] in ("remove_tree", "add_symlink", "set_mode"): |
| name = relative_path(operation["path"]) |
| if operation["kind"] == "remove_tree": |
| names = git("ls-files", "-z").split(b"\0") |
| prefix = os.fsencode(name) |
| remove = [item for item in names if item == prefix or item.startswith(prefix + b"/")] |
| if not remove: |
| raise ValueError(f"Source removal did not match upstream files: {name}") |
| git("update-index", "--force-remove", "-z", "--stdin", content=b"\0".join(remove) + b"\0") |
| elif operation["kind"] == "add_symlink": |
| target = operation["target"].encode() |
| oid = git("hash-object", "-w", "--stdin", content=target).decode().strip() |
| if oid != operation["expected_blob"]: |
| raise ValueError("Declared source symlink object changed") |
| git("update-index", "--add", "--cacheinfo", "120000", oid, name) |
| elif operation["kind"] == "set_mode": |
| if operation["from_mode"] not in ("100644", "100755") or operation["to_mode"] not in ("100644", "100755"): |
| raise ValueError("Source mode normalization requires regular file modes") |
| entries = git("ls-files", "--stage", "-z", "--", name).split(b"\0") |
| expected = (operation["from_mode"] + " " + operation["expected_blob"] + " 0\t" + name).encode() |
| if entries != [expected, b""]: |
| raise ValueError("Source mode normalization differs from its declared file") |
| git("update-index", "--cacheinfo", operation["to_mode"], operation["expected_blob"], name) |
| elif operation["kind"] == "reverse_patch": |
| patch = contained(task_root, operation["patch"]["path"]) |
| if sha256(patch) != operation["patch"]["sha256"]: |
| raise ValueError("Source construction patch changed") |
| git("apply", "--cached", "--reverse", "--check", str(patch)) |
| git("apply", "--cached", "--reverse", str(patch)) |
| else: |
| raise ValueError("Unknown source tree operation") |
| tree = git("write-tree").decode().strip() |
| if tree != recipe["expected_tree"]: |
| raise ValueError(f"Constructed source tree differs: {tree}") |
| actual = git("hash-object", "-t", "commit", "-w", "--stdin", content=commit).decode().strip() |
| if actual != repo["base_commit"]: |
| raise ValueError("Constructed source commit differs") |
| git("update-ref", "refs/crossswe/base/" + actual, actual) |
| return actual |
|
|
