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lucky-vers 2023-11-05 22:09:03 +05:30
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Phase 2/04 Forensics.md
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# tunn3l v1s10n
**Flag:** `picoCTF{qu1t3_a_v13w_2020}`
We're given a file `tunn3l_v1s10n`. Running `exiftool` on it gives us the following information about it
```
~/Downloads $ exiftool tunn3l_v1s10n
ExifTool Version Number : 12.60
File Name : tunn3l_v1s10n
Directory : .
File Size : 2.9 MB
File Modification Date/Time : 2023:11:05 20:32:44+05:30
File Access Date/Time : 2023:11:05 20:32:44+05:30
File Inode Change Date/Time : 2023:11:05 20:36:04+05:30
File Permissions : -rw-r--r--
File Type : BMP
File Type Extension : bmp
MIME Type : image/bmp
BMP Version : Unknown (53434)
Image Width : 1134
Image Height : 1134
Planes : 1
Bit Depth : 24
Compression : None
Image Length : 2893400
Pixels Per Meter X : 5669
Pixels Per Meter Y : 5669
Num Colors : Use BitDepth
Num Important Colors : All
Red Mask : 0x27171a23
Green Mask : 0x20291b1e
Blue Mask : 0x1e212a1d
Alpha Mask : 0x311a1d26
Color Space : Unknown (,5%()
Rendering Intent : Unknown (826103054)
Image Size : 1134x1134
Megapixels : 1.3
```
It seems to be a `.bmp` (bitmap) file with a size of 1134x1134 pixels. Thus wer rename it to `tunn3l_v1s10n.bmp`.
```
~/Downloads $ mv tunn3l_v1s10n tunn3l_v1s10n.bmp
renamed 'tunn3l_v1s10n' -> 'tunn3l_v1s10n.bmp'
```
Opening the file in Photopea, we get this result
![Not a flag](../Images/photopea_1.png)
The file seems to be missing pixels in its height, since it was given its height and width were the same (1134).
So, we need to change the headers of the bitmap to change it to its correct resolution. For this, we open a hex editor such as `xxd` to edit it
The height of a bitmap file is given at offset 0x16.
```
~/Downloads $ xxd tunn3l_v1s10n.bmp | head -2
00000000: 424d 8e26 2c00 0000 0000 bad0 0000 bad0 BM.&,...........
00000010: 0000 6e04 0000 3201 0000 0100 1800 0000 ..n...2.........
^^^^
the height
```
`3201` in this means a height of `0x0132`. This is because the bitmap is a little-endian file format, with the least significant byte (LSB) stored first. So we change it to 1134 in hexdecimal, which turns out to be `0x46e`, or `6e 04` in little-endian form.
```
~/Downloads $ xxd tunn3l_v1s10n.bmp | head -2
00000000: 424d 8e26 2c00 0000 0000 bad0 0000 bad0 BM.&,...........
00000010: 0000 6e04 0000 6e04 0000 0100 1800 0000 ..n...n.........
^^^^
the height
```
Now opening this in Photopea, we get this result, and the flag turns out to be `picoCTF{qu1t3_a_v13w_2020}`.
![The flag](../Images/photopea_2.png)
# Trivial Flag Transfer Protocol
**Flag:** `picoCTF{h1dd3n_1n_pLa1n_51GHT_18375919}`