unpacker for Microsoft EXEPACK
Unpacker for Microsoft EXEPACK utility compressor.
+--------------------------+
| EXEPACK HEADER |
+--------------------------+
| UNPACKER STUB |
+--------------------------+
| Error string |
| "Packed file is corrupt" |
+--------------------------+
| RELOCATION TABLE |
+--------------------------+
Header format:
+ 0x00 : REAL_IP [WORD] // Original initial IP value
+ 0x02 : REAL_CS [WORD] // Original initial (relative) CS value
+ 0x04 : MEM_START [WORD] // Start of executable in memory : not used by the unpacker
+ 0x06 : EXEPACK_SIZE [WORD] // sizeof (EXEPACK HEADER) + unpacker stub length + strlen(ERROR_STRING) + relocation table length
+ 0x08 : REAL_SP [WORD] // Original initial SP value
+ 0x0A : REAL_SS [WORD] // Original initial (relative) SS value
+ 0x0C : DEST_LEN [WORD] // Unpacked data length (in paragraphs)
+ 0x0E : SKIP_LEN [WORD] // field only present in specific version of EXEPACK : not used by the unpacker
+ 0x10 : SIGNATURE [WORD] // Magic number "RB"
EXEPACK employs a fairly basic run-length encoding, commands are encoded on bits 1-7 (mask 0xFE).
0xB0, write LENGTH bytes with VALUE.[LENGTH (WORD)][VALUE (BYTE)]
0xB2, copy the next LENGTH bytes[LENGTH (WORD)][BYTES ((BYTE) * LENGTH)]
Relocation table is optimized too, for each segment (0-15), there is the following layout, where entry is relative to the start of the exe in memory.
+ 0x00 : NB_ENTRIES [WORD]
+ 0x02 : ENTRY [WORD] * NB_ENTRIES
unpack.exe <EXEPACK_file> [OUTPUT_FILE]
default ouput file is "unpacked"
EXEPACK_file : Specifies the input file to unpack
OUTPUT_FILE : Specifies the output file to which the unpacked executable results will be written to. Defaults to ‘unpacked’.
If you are wondering if an game/executable is using EXEPACK, a list of EXEPACK executable is available here.
This list is based on the awesome Total DOS Collection Release 14 archive, thanks to the authors!
Only works on the English version of EXEPACK.
Relocation table location is computed by looking at the pattern “Packed file is corrupt”.
E.g: Sound.exe (md5 : F176559889278FFD535D753CEC99EA53) from Batman Returns (Es) (1992)(Konami Inc.) [Adventure]:
Offset(h) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
00002EE0 00 00 00 00 00 00 7D 01 00 01 3B 28 3C 28 02 00 ......}...;(<(..
00002EF0 52 42 8C C0 05 10 00 0E 1F A3 04 00 03 06 0C 00 RBŒÀ.....£......
00002F00 8E C0 8B 0E 06 00 8B F9 4F 8B F7 FD F3 A4 8B 16 ŽÀ‹...‹ùO‹÷ýó¤‹.
00002F10 0E 00 50 B8 38 00 50 CB 8C C3 8C D8 2B C2 8E D8 ..P¸8.PˌÌØ+ÂŽØ
00002F20 8E C0 BF 0F 00 B9 10 00 B0 FF F3 AE 47 8B F7 8B ŽÀ¿..¹..°ÿó®G‹÷‹
00002F30 C3 2B C2 8E C0 BF 0F 00 B1 04 8B C6 F7 D0 D3 E8 Ã+ÂŽÀ¿..±.‹Æ÷ÐÓè
00002F40 74 09 8C DA 2B D0 8E DA 83 CE F0 8B C7 F7 D0 D3 t.ŒÚ+ÐŽÚƒÎð‹Ç÷ÐÓ
00002F50 E8 74 09 8C C2 2B D0 8E C2 83 CF F0 AC 8A D0 4E èt.ŒÂ+ЎƒÏð¬ŠÐN
00002F60 AD 8B C8 46 8A C2 24 FE 3C B0 75 06 AC F3 AA EB .‹ÈFŠÂ$þ<°u.¬óªë
00002F70 07 90 3C B2 75 6B F3 A4 8A C2 A8 01 74 BA BE 2D ..<²ukó¤ŠÂ¨.tº¾-
00002F80 01 0E 1F 8B 1E 04 00 FC 33 D2 AD 8B C8 E3 13 8B ...‹...ü3Ò.‹Èã.‹
00002F90 C2 03 C3 8E C0 AD 8B F8 83 FF FF 74 11 26 01 1D Â.ÃŽÀ.‹øƒÿÿt.&..
00002FA0 E2 F3 81 FA 00 F0 74 16 81 C2 00 10 EB DC 8C C0 âó.ú.ðt..Â..ëÜŒÀ
00002FB0 40 8E C0 83 EF 10 26 01 1D 48 8E C0 EB E2 8B C3 @ŽÀƒï.&..HŽÀëâ‹Ã
00002FC0 8B 3E 08 00 8B 36 0A 00 03 F0 01 06 02 00 2D 10 ‹>..‹6...ð....-.
00002FD0 00 8E D8 8E C0 BB 00 00 FA 8E D6 8B E7 FB 2E FF .ŽØŽÀ»..úŽÖ‹çû.ÿ
00002FE0 2F B4 40 BB 02 00 B9 16 00 8C CA 8E DA BA 17 01 /´@»..¹..ŒÊŽÚº..
00002FF0 CD 21 B8 FF 4C CD 21 46 69 63 68 65 72 6F 20 63 Í!¸ÿLÍ!Fichero c
00003000 6F 72 72 6F 6D 70 69 64 6F 20 20 20 20 18 00 EA orrompido ..ê