## Pretty Slim
Opening the file in Winhex/Notepad, it seems like a Zip file.We changed the first byte to `P` (PK header) and extracted it but it seemed to be corrupted!!  More changes are needed to fix it.We had no time to fix it manually and we wanted the bonus points badly.The `DiskInternals ZIP Repair` did it right and by extracting it we got another file with string `KGB in Kremlin28` in header
KGB archiver?We should fix the header again
```$ unzip slim_fix.zip Archive:  slim_fix.zipThis Zip file has been recovered! extracting: flaggggg    
$ stat /tmp/1 | grep Size  Size: 8626         Blocks: 8          IO Block: 4096   regular file $ kgb 1.kgb /tmp/1/tmp/1                           0KB -> 0KB0KB -> 0KB w 0.01s. (112.53% czas: 29 KB/s)
$ hexdump -C 1.kgb| head -200000000  4b 47 42 5f 61 72 63 68  20 2d 33 0d 0a 38 36 32  |KGB_arch -3..862|00000010  36 09 2f 74 6d 70 2f 31  0d 0a 1a 0c 00 82 4a c5  |6./tmp/1......J.|
$ stat flaggggg | grep Size  Size: 359         Blocks: 8          IO Block: 4096   regular file $ hexdump -C flaggggg| head -200000000  4b 47 42 20 69 6e 20 4b  72 65 6d 6c 69 6e 32 38  |KGB in Kremlin28|00000010  09 66 6c 61 67 67 67 67  67 0d 0a 1a 0c 00 7b 00  |.flaggggg.....{.|```
KGB is not sensitive to the size of file in its header (inner file size before decompression)We set it to 359 and it worked so no need to bruteforce it
```$ vbindiff flaggggg flaggggg_fixed_kgb flaggggg                                                                        0000 0000: 4B 47 42 20 69 6E 20 4B  72 65 6D 6C 69 6E 32 38  KGB in K remlin28[...]flaggggg_fixed_kgb                                                              0000 0000: 4B 47 42 5F 61 72 63 68  20 2D 33 0D 0A 33 35 39  KGB_arch  -3..359[...]
$ file flaggggg_fixed_kgb flaggggg_fixed_kgb: KGB Archiver file with compression level 3
$ kgb flaggggg_fixed_kgb Extracting archive KGB_arch -3 flaggggg_fixed_kgb ...         0KB flaggggg: different: offset 0, archive=137 file=750KB -> 0KB w 0.01s. (100.00% czas: 44 KB/s)
$ rm flaggggg; kgb flaggggg_fixed_kgbExtracting archive KGB_arch -3 flaggggg_fixed_kgb ...         0KB flaggggg: extracted0KB -> 0KB w 0.01s. (100.00% czas: 37 KB/s)
$ file flagggggflaggggg: PNG image data, 111 x 111, 1-bit grayscale, non-interlaced```
![flaggggg.png](flaggggg.png)