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From cfd61f6958a46d5e9687f87caf04c94680382a9f Mon Sep 17 00:00:00 2001
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From: Nicolas Frayer <nfrayer@redhat.com>
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Date: Wed, 1 Feb 2023 12:13:45 +0100
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Subject: [PATCH] generate_binary: Add NX COMPAT flag manually when genpeimg
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missing
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When genpeimg or python3-pefile is missing, add the NX COMPAT flag
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manually by setting bit8 of the DllCharacteristics in the optional
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header, clear the TimeDateStamp and update the checksum.
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---
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efi/generate_binary.py | 50 ++++++++++++++++++++++++++++++++++++++++--
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1 file changed, 48 insertions(+), 2 deletions(-)
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diff --git a/efi/generate_binary.py b/efi/generate_binary.py
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index 7b802e7..10ab0b3 100755
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--- a/efi/generate_binary.py
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+++ b/efi/generate_binary.py
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@@ -10,6 +10,13 @@
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import subprocess
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import sys
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import argparse
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+import os
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+import struct
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+
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+COFF_HDR_OFFSET = 0x80
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+OPTIONALHDR_CHECKSUM = COFF_HDR_OFFSET + 0x58
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+OPTIONALHDR_DLLCHARACTERISTICS = COFF_HDR_OFFSET + 0x5E
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+PEHEADER_TIMEDATASTAMP = COFF_HDR_OFFSET + 0x8
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def _run_objcopy(args):
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@@ -66,6 +73,27 @@ def _run_genpeimg(args):
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sys.exit(1)
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+def generate_checksum(data):
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+ checksum_offset: int = OPTIONALHDR_CHECKSUM
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+ checksum: int = 0
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+ remainder: int = len(data) % 4
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+ data_len: int = len(data) + ((4 - remainder) * (remainder != 0))
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+ for i in range(int(data_len / 4)):
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+ if i == int(checksum_offset / 4):
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+ continue
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+ if i + 1 == (int(data_len / 4)) and remainder:
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+ dword = struct.unpack("I", data[i * 4 :] + (b"\0" * (4 - remainder)))[0]
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+ else:
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+ dword = struct.unpack("I", data[i * 4 : i * 4 + 4])[0]
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+ checksum += dword
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+ if checksum >= 2**32:
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+ checksum = (checksum & 0xFFFFFFFF) + (checksum >> 32)
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+ checksum = (checksum & 0xFFFF) + (checksum >> 16)
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+ checksum = checksum + (checksum >> 16)
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+ checksum = checksum & 0xFFFF
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+ return checksum + len(data)
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+
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+
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def _add_nx_pefile(args):
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# unnecessary if we have genpeimg
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if args.genpeimg:
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@@ -73,8 +101,26 @@ def _add_nx_pefile(args):
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try:
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import pefile
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except ImportError:
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- print("Unable to add NX support to binaries without genpeimg or python3-pefile")
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- sys.exit(1)
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+ print("Adding NX support manually to the binary")
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+ with open(args.outfile, "r+b") as fh:
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+ buf = bytearray(fh.read(os.path.getsize(args.outfile)))
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+ fh.seek(0)
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+ DllCharacteristics = struct.unpack_from(
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+ "
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+ )[0]
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+ DllCharacteristics |= 0x100
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+ struct.pack_into(
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+ "
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+ )
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+
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+ # set the timestamp to 0
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+ struct.pack_into("
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+
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+ # as we have set the NX COMPAT bit, regenerate the checksum
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+ struct.pack_into("
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+ fh.write(buf)
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+
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+ return
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pe = pefile.PE(args.outfile)
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pe.OPTIONAL_HEADER.DllCharacteristics |= pefile.DLL_CHARACTERISTICS[
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--
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2.39.1
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