CTF Points Server

This server speaks 3 related protocols: EASY, MEDIUM, and HARD.

All three are simple TLV (Type, Length, Value) binary protocols. Each field is encoded as:

• Type: 16 bit network order short
• Length: 16 bit network order short
• Value: n bytes where n is the value of the Length field

EASY

The request for easy uses 2 fields:

• NAME - Type: 314, Length: <= 127 The team name
• KEY - Type: 42, Length: 25 The flag being submitted

The server responds with RESULT:

• KEY - Type: 7 'OK' if success, 'KERNEL WHO?' otherwise

MEDIUM

Medium is a wrapper for EASY that adds a checksum.

Request:

• BODY - Type: 5 A full EASY packet
• HASH - Type: 19780 ("MD"), Length: 16 An MD5 hash of the entire EASY packet (Not hex encoded)

The response is the same as the request except the contents of BODY is an EASY response.

HARD

Hard is a wrapper for MEDIUM that encrypts the entire MEDIUM packet.

The encryption is done with AES 256 CBC mode. The IV is all 0 bytes (The default in openssl if one is not specified)

Request:

• BODY - Type: 256 A full MEDIUM packet
• KEY - Type: 17218, Length: 32 (256 bits) The encryption key
• HINT - Type: 1337, Length: 3 The string "AES" as a hint in the pcap files

Response:

• BODY - Type: 256 A full MEDIUM packet encrypted with the key passed in the request
• HINT - Type: 1337, Length: 3 The string "AES" as a hint in the pcap files