"Unsupported target format 'COFF64'" when using --mode raw

[user7]

I use --mode raw to decompile x86 code. It mostly works, but if input file contains 18 leading zeroes, then it complains about file being COFF64. For example the following bash script:

offset=18
dd if=/dev/zero bs=$offset count=1 >raw.bin
printf "\x31\xc0\xc3" >>raw.bin # xor eax, eax; ret
./retdec-decompiler.py \
    --mode raw \
    --arch x86 \
    --endian little \
    --raw-section-vma 0 \
    --raw-entry-point $offset \
    raw.bin

produces an error:

##### Gathering file information...
RUN: /media/data/b/u/p/retdec/sandbox/bin/retdec-fileinfo -c /media/data/b/u/p/retdec/140/raw.bin.c.json --similarity /media/data/b/u/p/retdec/140/raw.bin --no-hashes=all --crypto /media/data/b/u/p/retdec/sandbox/bin/../share/retdec/support/generic/yara_patterns/signsrch/signsrch.yara --max-memory-half-ram
Input file               : /media/data/b/u/p/retdec/140/raw.bin
File format              : COFF
File class               : 64-bit
File type                : Relocatable file
Architecture             : Unknown machine type (0)
Overlay offset           : 0
Overlay size             : 0x15
Warning: Unknown compiler or packer.

##### Trying to unpack /media/data/b/u/p/retdec/140/raw.bin into /media/data/b/u/p/retdec/140/raw.bin-unpacked.tmp by using generic unpacker...
RUN: /media/data/b/u/p/retdec/sandbox/bin/retdec-unpacker /media/data/b/u/p/retdec/140/raw.bin -o /media/data/b/u/p/retdec/140/raw.bin-unpacked.tmp --max-memory-half-ram
##### Unpacking by using generic unpacker: nothing to do

##### Trying to unpack /media/data/b/u/p/retdec/140/raw.bin into /media/data/b/u/p/retdec/140/raw.bin-unpacked.tmp by using UPX...
RUN: upx -d /media/data/b/u/p/retdec/140/raw.bin -o /media/data/b/u/p/retdec/140/raw.bin-unpacked.tmp
upx: /media/data/b/u/p/retdec/140/raw.bin: EOFException: premature end of file
##### Unpacking by using UPX: nothing to do
Error: Unsupported target format 'COFF64'. Supported formats: ELF32, PE32, Intel HEX 32, Mach-O 32.

while if I change offset to 17 or less, then decompilation works.

I thought --mode raw is supposed to skip format guessing and unpacking. Is this right?

[mbandzi]

may be related to #421

[jkbenaim]

I ran into this bug too. My file started with a few kilobytes of padding zeroes. I was able to work around the problem by replacing the zeroes with random bytes.

[PeterMatula]

Indeed related to #421, but it should not matter - even if COFF detection is wrong, when user specifies mode raw it should be used.

Fixed by forcing raw mode if user set it.