84 lines
2.2 KiB
Python
84 lines
2.2 KiB
Python
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#!/usr/bin/env python3
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"""Replace ENDBR and the unsafe 0F 1F 40 00 NOP with 90 90 90 90.
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Nested VMX leaks user CET: glibc ENDBR64 #GPs. Multi-byte NOP
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`0F 1F 40 00` (`nop dword ptr [rax]`) can still #GP when RAX is 0.
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Four 0x90 NOPs do not.
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"""
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from __future__ import annotations
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import os
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import sys
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OLD = (
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b"\xf3\x0f\x1e\xfa", # endbr64
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b"\xf3\x0f\x1e\xfb", # endbr32
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b"\x0f\x1f\x40\x00", # nop dword ptr [rax]
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)
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NEW = b"\x90\x90\x90\x90"
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def is_elf(path: str) -> bool:
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try:
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with open(path, "rb") as f:
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return f.read(4) == b"\x7fELF"
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except OSError:
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return False
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def patch_file(path: str) -> int:
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try:
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with open(path, "rb") as f:
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data = f.read()
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except OSError:
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return 0
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if len(data) < 64 or data[:4] != b"\x7fELF":
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return 0
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n = 0
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out = data
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for old in OLD:
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c = out.count(old)
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if c:
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out = out.replace(old, NEW)
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n += c
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if n:
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with open(path, "wb") as f:
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f.write(out)
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return n
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def walk(root: str) -> None:
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files = 0
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hits = 0
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scanned = 0
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for dirpath, dirnames, filenames in os.walk(root, followlinks=False):
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dirnames[:] = [d for d in dirnames if d not in ("proc", "sys", "dev", "run")]
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for name in filenames:
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path = os.path.join(dirpath, name)
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try:
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if os.path.islink(path) or not os.path.isfile(path):
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continue
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if os.path.getsize(path) < 64:
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continue
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except OSError:
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continue
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scanned += 1
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if scanned % 500 == 0:
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print(f"[endbr90] {root}: scanned={scanned} patched={files}", flush=True)
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if not is_elf(path):
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continue
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try:
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n = patch_file(path)
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except Exception as exc:
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print(f"[endbr90] skip {path}: {exc}", flush=True)
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continue
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if n:
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files += 1
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hits += n
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print(f"[endbr90] {root}: files={files} replacements={hits} scanned={scanned}", flush=True)
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if __name__ == "__main__":
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for root in sys.argv[1:]:
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walk(root)
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