Olicyber.it挑战：Wireshark捕获的gzip压缩十六进制数据解压求助

Step 1: Fix Hex String Length #

Your provided hex string ends with 1517e26—an odd number of characters. Hex data requires even-length formatting, so first verify if you missed a character during copying. If you can't recover the missing byte, try truncating the last character to make the string even-length (this is a common quick fix for truncated capture data).

Step 2: CyberChef Recipe with Error Tolerance #

Once the hex string is even-length:

• Paste the corrected hex into CyberChef.
• Apply the Hex to Raw operation to convert hex to binary gzip data.
• Add the Gunzip operation, then enable the "Ignore errors" option in its settings. CTF challenges often include slightly corrupted gzip data or extra trailing bytes, and this flag bypasses strict validation checks that would otherwise block decompression.

Step 3: Command-Line Workaround #

If CyberChef still fails, use command-line tools for more lenient decompression:

1. Convert hex to a binary gzip file:

   echo -n "CORRECTED_HEX_STRING" | xxd -r -p > data.gz
   

2. Use zcat to decompress while ignoring errors:

   zcat data.gz 2>/dev/null
   

   This command outputs decompressed data even if there are CRC or length mismatches, discarding error messages that would stop standard gunzip.

Step 4: Trim Trailing Extra Bytes #

TCP captures sometimes include extra non-gzip bytes at the end. If decompression still fails, try truncating the hex string by removing the last 2-4 pairs of characters (one or two bytes) and re-running the decompression steps. Trial and error here often works for CTF scenarios where payloads are appended with irrelevant data.

内容的提问来源于stack exchange，提问作者Leonardo Martinelli