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build.run: prohibit absolute paths in BuildPlan.add_file.

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This makes the build impure and also causes the contents of a file
outside of the build directory to be overwritten.

The check in `BuildPlan.execute_local` is also expanded to cover
the possibility of an absolute path sneaking through.
This commit is contained in:
Catherine 2023-08-22 16:20:44 +00:00
parent 4ffadff20d
commit c9fd0d8391
1 changed files with 6 additions and 3 deletions
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9
amaranth/build/run.py
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@ -33,6 +33,9 @@ class BuildPlan:
forward slashes (``/``).
"""
assert isinstance(filename, str) and filename not in self.files
if (pathlib.PurePosixPath(filename).is_absolute or
pathlib.PureWindowsPath(filename).is_absolute):
raise ValueError(f"Filename {filename!r} must not be an absolute path")
self.files[filename] = content
def digest(self, size=64):
@ -78,9 +81,9 @@ class BuildPlan:
for filename, content in self.files.items():
filename = pathlib.Path(filename)
# Forbid parent directory components completely to avoid the possibility
# of writing outside the build root.
assert ".." not in filename.parts
# Forbid parent directory components and absolute paths completely to avoid
# the possibility of writing outside the build root.
assert not filename.is_absolute and ".." not in filename.parts
dirname = os.path.dirname(filename)
if dirname:
os.makedirs(dirname, exist_ok=True)