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63591 You passed the step 0! (The maximum score (in the best case) is indicated )

This is the server por the Network Computer ginkana. Version 0.20170316.

Remember that you can see the server log in: http://atclab.esi.uclm.es/ginkana/

Students are advised to use UTF-8 encoding in their terminal to avoid coding problems.

Step 1: UDP

Create a UDP server on your machine (on the port you want)
Send a message to the UDP server atclab.esi.uclm.es: 2000 indicating the identifier "63591" and the port on which you have created your UDP server, separated by a space. Example: "63591 7777" (without quotes).

Your UDP server will receive the instructions to continue. You have 4 seconds.

Hints:

Check that it is possible to connect to your UDP server from a machine with a public IP (use netcat to check that).

1929 You passed the step 1!

Etapa 2: Aritmetic

Connect to server atclab.esi.uclm.es:1929
You will receive a text string with a mathematical operation in ASCII format.
The expression contains parentheses and brackets, and are well balanced (there are so many opening and closure).
Calculate the result of the operation and reply through the same socket, placing the result within parentheses.
The process is repeated for an undetermined number of operations.

If everything is right, the server will instruct you to continue. You have 20 seconds.

Tracks:

The parentheses are vital, the spaces trivial.
The symbol '/' represents an entire division.
Example:
- server: (2 * [3+ 5] * {1 -0})
- client: (16)

Restrictions:

It is not allowed to use the function eval(), exec() or any other that evaluates python statements.

You have 20 seconds.

[1+ 81] Result is 82

([{(94/ 57)/[30-40]} + [32*72]]+ (48 /{24+36})) Result is 2303

[[16+ (65 + [73/83])] * 0] Result is 0

(79-(4 - 98)) Result is 173

{[80 -[52 * 15]]-{(57 - 85)-[12 - 22]}} Result is -682

[10 * {46 +{88 -{81 + 27}}}] Result is 260

35832 You passed the step 2!

Step 3: HTTP Client

You must download the file "http://atclab.esi.uclm.es:5000/35832".

The file contains the instructions to continue. You have 6 seconds.

Restrictions:

It is not allowed to use urllib, urllib2 and urllib3 modules.

72814 You passed the step 3!

Step 4: Ping

You must send an ICMP Echo Request message to atclab.esi.uclm.es. the payload of this message must include, AFTER the usual content, the ASCII string "72814".

+--------------+----------------------------+ | Echo Request | | | Header | timestamp(8 bytes) + 72814 | +--------------+----------------------------+
You will receive an ICMP Echo Reply message with the instructions to continue.

You have 5 seconds.

Hints:

Using wireshark, analyze the content and size of a conventional ping message. You can send pings that are shorter than normal with "ping -s size".
Study the chapter "RAW Sockets" in the lab manual.
Remember that to use raw sockets you must run the program with admin privileges.
Build an ICMP message mimicking the one you have captured. Identical at first. If it works, add your changes step by step.
To construct the message you can use struct.pack().
You can use the checksum calculation function in https://bitbucket.org/arco_group/python-net/src/tip/raw/icmp_checksum.py
Constructs the ICMP message indicating a 0 in the checksum field. Calculate the checksum and rebuilds the message using the calculation result.

46005 You passed the step 4!

Step 5: Proxy Web

Create an HTTP Proxy server on your computer (in the port of your choice).
Your server will receive a random amount of HTTP requests for download third-party URLs, you must download these resources (using HTTP) and return them to the requesting customer.

+--------+ +--------------+ +-------------+ | Client | | Proxy server | | HTTP server | +--------+ +--------------+ +-------------+ | | | | GET(server, url) | | +------------------>+++ connect(server) | | | |------------------->| | | | file: GET(url) | | file | |------------------->| |<------------------+++ | | | |

Create a client socket and send a message to the server TCP atclab.esi.uclm.es:9000 Indicating the identifier "46005" and the port on which you have created Your proxy server, separated by a space. Example: "46005 7777".
Through the same socket you will receive further instructions or information about errors.

Hints:

Caution: Your proxy will receive simultaneous requests and it is expected that serve them quickly. If it takes too long, this step will fail. In order to achieve it create a concurrent server for your proxy.
You can prove that your proxy is right by executing it as a independent program (unrelated to gink

---------- Enviando petición HTTP... ---------- GET http://www.ietf.org/rfc/rfc864.txt HTTP/1.1 Accept-Encoding: identity Host: www.ietf.org Connection: close User-Agent: Python-urllib/2.7