BUUCTF_MISC——[MRCTF2020]ezmisc, Dutch broadband data breach, [BJDCTF 2nd] the simplest misc-y1ng

1. [MRCTF2020]ezmisc

Ⅰ. Tools

1. TweakPNG
2. Winhex

Ⅱ. Solution

Use TweakPNG to view the picture, a chunk error appears, that is, the picture size has been modified

The picture is 500x319, and it is suspected that the picture has been highly modified

Open with Winhex, the red frame is the size data of the PNG image, in hexadecimal

Change the latter to 1F4 (16), which is 500 (10)

Save it to find that the hidden part has FLAG

2. The Dutch broadband data breach

Ⅰ. Tools

1. RouterPassView

Ⅱ. Solution

The file is conf.bina broadband data file and needs to be opened with RouterPassView

Not give a clear prompt FLAG, then it should be the account name or password

several attempts to find a user name

flag{053700357621}

3. [BJDCTF 2nd] The simplest misc-y1ng

Ⅰ. Tools

1. ZipCenOp
2. Winhex

Ⅱ. Solution

The topic is an encrypted compressed package, there is no prompt password, consider it is pseudo encryption

Use ZipCenOp to crack fake encryption

Run the following code in cmd:

java ZipCenOp.jar r secret.zip

Successfully decompressed

Use Winhex to check the file data and find the IHDRstring, indicating that this is a PNG file with a missing header

Insert four bytes of 0 data before the first byte, ready to complete the file header

Add PNG file header 89504E47and save

Add a suffix to the file .pngand find a hexadecimal string424A447B79316E677A756973687561697D

Use online conversion tool to get FLAG plaintext

BJD {y1ngzuishuai}

Finish

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