Fix insecure default temp file path in session dump/load#751
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eddieran wants to merge 1 commit intouqfoundation:masterfrom
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Fix insecure default temp file path in session dump/load#751eddieran wants to merge 1 commit intouqfoundation:masterfrom
eddieran wants to merge 1 commit intouqfoundation:masterfrom
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The default /tmp/session.pkl path used by dump_module(), load_module(), and load_module_asdict() is insecure because /tmp is world-writable and shared, making it vulnerable to symlink attacks, pickle substitution, and information disclosure. - Add _check_symlink() using os.lstat() to reject symlinks - Add _safe_open_for_writing() using O_CREAT|O_EXCL|O_WRONLY with 0o600 - Emit SecurityWarning when the default path is used - Add test_symlink_rejected() and test_default_path_warning() tests Fixes uqfoundation#749
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Summary
Fixes #749 — the default
/tmp/session.pklpath used bydump_module(),load_module(), andload_module_asdict()is insecure because/tmpis world-writable and shared, making it vulnerable to symlink attacks and race conditions.Changes
_check_symlink()that usesos.lstat()to reject symlinks before reading or writing session files._safe_open_for_writing()that usesos.open()withO_CREAT | O_EXCL | O_WRONLYand mode0o600for race-free exclusive file creation. If the file already exists, it verifies it is not a symlink before opening.SecurityWarningwhen the default shared/tmp/session.pklpath is used, advising users to pass an explicit filename.test_symlink_rejected()andtest_default_path_warning()totest_session.py.Files changed
dill/session.py— security helpers and warning indump_module,load_module,load_module_asdictdill/tests/test_session.py— new security testsTest plan
dump_module/load_module/load_module_asdictbehavior unchanged for explicit paths and stream objectstest_symlink_rejectedverifies symlinks are rejected by all three functionstest_default_path_warningverifiesSecurityWarningis emitted for the default path