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Last active May 20, 2023 07:38
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Python Script to disable ASLR and make nv fatbins read-only to reduce memory commit
# Simple script to disable ASLR and make .nv_fatb sections read-only
# Requires: pefile ( python -m pip install pefile )
# Usage: --input path/to/*.dll
import argparse
import pefile
import glob
import os
import shutil
def main(args):
failures = []
for file in glob.glob( args.input, recursive=args.recursive ):
print(f"\n---\nChecking {file}...")
pe = pefile.PE(file, fast_load=True)
nvbSect = [ section for section in pe.sections if section.Name.decode().startswith(".nv_fatb")]
if len(nvbSect) == 1:
sect = nvbSect[0]
size = sect.Misc_VirtualSize
writable = 0 != ( sect.Characteristics & pefile.SECTION_CHARACTERISTICS['IMAGE_SCN_MEM_WRITE'] )
print(f"Found NV FatBin! Size: {size/1024/1024:0.2f}MB ASLR: {aslr} Writable: {writable}")
if (writable or aslr) and size > 0:
print("- Modifying DLL")
if args.backup:
bakFile = f"{file}_bak"
print(f"- Backing up [{file}] -> [{bakFile}]")
if os.path.exists( bakFile ):
print( f"- Warning: Backup file already exists ({bakFile}), not modifying file! Delete the 'bak' to allow modification")
failures.append( file )
shutil.copy2( file, bakFile)
except Exception as e:
print( f"- Failed to create backup! [{str(e)}], not modifying file!")
failures.append( file )
# Disable ASLR for DLL, and disable writing for section
sect.Characteristics = sect.Characteristics & ~pefile.SECTION_CHARACTERISTICS['IMAGE_SCN_MEM_WRITE']
newFile = f"{file}_mod"
print( f"- Writing modified DLL to [{newFile}]")
pe.write( newFile )
print( f"- Moving modified DLL to [{file}]")
os.remove( file )
shutil.move( newFile, file )
except Exception as e:
print( f"- Failed to write modified DLL! [{str(e)}]")
failures.append( file )
if len(failures) > 0:
print("***WARNING**** These files needed modification but failed: ")
for failure in failures:
print( f" - {failure}")
def parseArgs():
parser = argparse.ArgumentParser( description="Disable ASLR and make .nv_fatb sections read-only", formatter_class=argparse.ArgumentDefaultsHelpFormatter )
parser.add_argument('--input', help="Glob to parse", default="*.dll")
parser.add_argument('--backup', help="Backup modified files", default=True, required=False)
parser.add_argument('--recursive', '-r', default=False, action='store_true', help="Recurse into subdirectories")
return parser.parse_args()
# program entry point
if __name__ == "__main__":
args = parseArgs()
main( args )
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szan12 commented Nov 24, 2022

Hi @cobryan05 , I'm getting this output that says :
" Failed to write modified DLL! [[WinError 5] Access is denied: .. "

Can I know what should I do to enable it to be modified?


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cobryan05 commented Nov 28, 2022

@szan12 For it to be getting 'access denied' in your User directory, I would assume that it means the file is in use. Try restarting your computer and then running it, or try typing "taskkill /f /im python.exe" in your command prompt before running it (this will forcefully close any python process you have running). If that still fails, try running from a cmd prompt that is "Run as administrator", but that shouldn't be necessary in the 'user' directory

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