41 lines
1.6 KiB
Python
41 lines
1.6 KiB
Python
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"""Pure reviewed k3s unit transformation. No write, reload or restart capability."""
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import hashlib
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import os
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from pathlib import Path
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import re
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import stat
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BEFORE = 'b5398c385430ce225faadc1f3724597fe4b05dd999a04b8abbca64d4b0d68c0e'
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AFTER = '866ea58bfab00215e5bd3352287ebb0230d4ddb7dd3ed4b1cd853e74c6698d7d'
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PATH = Path('/etc/systemd/system/k3s.service')
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def transform(raw, *, before=BEFORE, after=AFTER):
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if hashlib.sha256(raw).hexdigest() != before:
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raise ValueError('unit_preimage_changed')
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candidate, count = re.subn(rb'(--write-kubeconfig-mode(?:=|[ \t]+)[\x22\x27]?)644\b', rb'\g<1>600', raw)
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if count != 1 or len(candidate) != len(raw) or sum(a != b for a,b in zip(raw,candidate)) != 2:
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raise ValueError('unit_change_not_exact')
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if hashlib.sha256(candidate).hexdigest() != after:
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raise ValueError('unit_candidate_mismatch')
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return candidate
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def prepare():
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# Open without symlink following and bind metadata/read to the same object.
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fd = os.open(PATH, os.O_RDONLY | os.O_NOFOLLOW)
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try:
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st = os.fstat(fd)
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if (not stat.S_ISREG(st.st_mode) or stat.S_IMODE(st.st_mode) != 0o644
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or (st.st_uid, st.st_gid, st.st_dev, st.st_ino) != (0,0,2049,7875)
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or st.st_nlink != 1):
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raise ValueError('unit_identity_changed')
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with os.fdopen(os.dup(fd), 'rb') as stream:
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candidate = transform(stream.read())
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end = os.fstat(fd)
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if (end.st_mtime_ns,end.st_ctime_ns,end.st_size) != (st.st_mtime_ns,st.st_ctime_ns,st.st_size):
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raise ValueError('unit_changed_during_read')
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return candidate
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finally:
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os.close(fd)
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