43 lines
2.2 KiB
Markdown
43 lines
2.2 KiB
Markdown
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# do you hear that?
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> I'm not sure why, but when I look at this image I can hear some sort of faint sound. Do you hear it too?
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## About the Challenge
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We were given an image called `help.png` (You can download the file [here](help.png)) and if we check using `zsteg` there's a wav file inside the image
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```
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root@ubuntu:~# zsteg help.png
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[?] 317564 bytes of extra data after image end (IEND), offset = 0x8a24
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extradata:0 .. file: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, mono 44100 Hz
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00000000: 52 49 46 46 74 d8 04 00 57 41 56 45 66 6d 74 20 |RIFFt...WAVEfmt |
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00000010: 10 00 00 00 01 00 01 00 44 ac 00 00 88 58 01 00 |........D....X..|
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00000020: 02 00 10 00 64 61 74 61 50 d8 04 00 00 00 00 00 |....dataP.......|
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00000030: 01 00 03 00 05 00 08 00 0a 00 0b 00 0b 00 09 00 |................|
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00000040: 06 00 02 00 fe ff f9 ff f6 ff f4 ff f5 ff f7 ff |................|
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00000050: fb ff 00 00 04 00 08 00 09 00 06 00 00 00 f7 ff |................|
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00000060: ec ff e0 ff d5 ff cd ff c8 ff c8 ff ce ff d7 ff |................|
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00000070: e3 ff f0 ff fb ff 03 00 05 00 01 00 f7 ff e9 ff |................|
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00000080: d8 ff c9 ff be ff b9 ff bd ff cb ff e0 ff fd ff |................|
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00000090: 1b 00 39 00 51 00 60 00 64 00 5c 00 4b 00 32 00 |..9.Q.`.d.\.K.2.|
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000000a0: 18 00 02 00 f6 ff f7 ff 08 00 29 00 57 00 8d 00 |..........).W...|
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000000b0: c3 00 f1 00 0e 01 16 01 05 01 db 00 9e 00 55 00 |..............U.|
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000000c0: 0c 00 ce ff a6 ff 9d ff b7 ff f2 ff 46 00 a4 00 |............F...|
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000000d0: fb 00 36 01 40 01 09 01 88 00 ba ff aa fe 6a fd |..6.@.........j.|
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000000e0: 17 fc d3 fa c5 f9 10 f9 d2 f8 21 f9 01 fa 6d fb |..........!...m.|
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000000f0: 4c fd 7b ff cb 01 09 04 04 06 8f 07 89 08 de 08 |L.{.............|
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[!] possible image block size is 639x5, downscaling may be necessary
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```
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## How to Solve?
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First, we need to extract the WAV file inside the png using this command
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```bash
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zsteg -e extradata:0 help.png > sound.wav
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```
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And then use spectogram analyzer, there's an online tool like https://www.dcode.fr/spectral-analysis or you can use `Sonic Visualizer`
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```
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bctf{y0u_h4v3_s0m3_g00d_34rs}
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```
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