docs: Clean up resources for Hackoctoberfest 2019 (#41)

* Clean up resources for Hackoctoberfest 2019

* 👩🏾‍🦱 Add cloud hacking readme

CTFs_and_WarGames/2014/9447/README.md

@@ -0,0 +1,213 @@
+# 9447's CTF 2014
+
+## On Redis & AES Encryption 
+
+### The Client File
+
+The first file was a script **client.py**, where, by using Python's [socket](https://docs.python.org/2/library/socket.html) library, showed how a connection to the server could be made:
+
+```py
+import os, socket, struct, sys
+from Crypto.Cipher import AES
+
+class EncryptedStream(object):
+ key = 'this is not the flag nor the key'[:16]
+ def __init__(self, host, port):
+ self.sock = socket.socket()
+ self.sock.connect((host, port))
+ def send(self, msg):
+ while len(msg) % 16:
+ msg += '\0'
+ iv = os.urandom(16)
+ aes = AES.new(self.key, AES.MODE_ECB, iv)
+ enc = aes.encrypt(msg)
+ self.sock.send(struct.pack('<I', len(enc)))
+ self.sock.send(enc)
+ def recv(self, nbytes):
+ return self.sock.recv(nbytes)
+
+client = '''\
+HELLO
+SHOW VERSION
+SET example This tiny script is basically a RedisStore...
+GET example
+SHOW KEYS
+SET brucefact#1 Bruce Schneier can break elliptic curve cryptography by bending it into a circle
+SET brucefact#2 Bruce Schneier always cooks his eggs scrambled. When he wants hardboiled eggs, he unscrambles them
+SET brucefact#3 Bruce Schneier could solve this by inverting md5 hash of the flag
+ENCRYPTION HEX
+MD5 flag
+'''
+
+stream = EncryptedStream(sys.argv[1], int(sys.argv[2]))
+stream.send(client)
+while 1:
+ data = stream.recv(1000)
+ if not data: break
+ sys.stdout.write(data)
+```
+
+This client script makes [AES](http:https://en.wikipedia.org/wiki/Advanced_Encryption_Standard) encrypted packets for a given host and port (the arguments), with the class **EncryptedStream**. It then sends the packets and prints out any received stream.
+
+The snippet also shows an example of a client packet, with some request options (which we will see the response later in the network dump).
+
+
+### The Server File
+
+The second file was the **server.py** script, which is a [Redis](http:https://redis.io/) like a database (hence, the *nosql* title). Unlike SQL databases, Redis *maps keys to types of values*. In this challenge, the idea was to recover an entry that had the key **flag** returning the value of the flag.
+
+In the script below, besides creating this database, functions such as: **AES decrypting** (encryption), **MD5** (hashing), and **hex** (encoding) are implemented using Python's library:
+
+```py
+import hashlib, os, signal, struct, sys
+from Crypto.Cipher import AES
+
+key = 'this is not the flag nor the key'[:16]
+db = { }
+
+def md5(data):
+ return hashlib.md5(data).digest()
+
+def decrypt(data):
+ iv = os.urandom(16)
+ aes = AES.new(key, AES.MODE_ECB, iv)
+ data = aes.decrypt(data)
+ return data.rstrip('\0')
+
+def reply_plain(message):
+ sys.stdout.write(message + '\n')
+
+def reply_hex(message):
+ # This is totally encrypted, right?
+ sys.stdout.write(message.encode('hex') + '\n')
+
+def main():
+ global db
+ reply = reply_plain
+
+ datalen = struct.unpack('<I', sys.stdin.read(4))[0]
+ data = ''
+ while len(data) != datalen:
+ s = sys.stdin.read(1)
+ if not s:
+ sys.exit(1)
+ data += s
+ data = decrypt(data)
+
+ commands = data.split('\n')
+
+ for cmd in commands:
+ if not cmd:
+ continue
+ if ' ' in cmd:
+ cmd, args = cmd.split(' ', 1)
+
+ if cmd == 'HELLO':
+ reply('WELCOME')
+ elif cmd == 'SHOW':
+ if args == 'VERSION':
+ reply('NoRedisSQL v1.0')
+ elif args == 'KEYS':
+ reply(repr(db.keys()))
+ elif args == 'ME THE MONEY':
+ reply("Jerry, doesn't it make you feel good just to say that!")
+ else:
+ reply('u w0t m8')
+ elif cmd == 'SET':
+ key, value = args.split(' ', 1)
+ db[key] = value
+ reply('OK')
+ elif cmd == 'GET':
+ reply(args + ': ' + db.get(args, ''))
+ elif cmd == 'SNIPPET':
+ reply(db[args][:10] + '...')
+ elif cmd == 'MD5':
+ reply(md5(db.get(args, '')))
+ elif cmd == 'ENCRYPTION':
+ if args == 'HEX':
+ reply = reply_hex
+ reply('OK')
+ elif args == 'OFF':
+ reply = reply_plain
+ reply('OK')
+ else:
+ reply('u w0t m8')
+ else:
+ reply('Unknown command %r' % (cmd))
+
+
+if __name__ == '__main__':
+ signal.alarm(10)
+ signal.signal(signal.SIGALRM, lambda a,b: sys.exit(0))
+ main()
+```
+
+This script pretty much gives away all the requests that you can issue to inspect the database.
+
+In addition, a crucial detail is to understand how the client encrypts the commands using the [electronic codebook (ECB)](http:https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Electronic_codebook_.28ECB.29) block cipher type. In this type of operation the message is divided into blocks that are encrypted separately ([PyCryptos's AES.MODE_ECB](https://www.dlitz.net/software/pycrypto/api/2.6/)).
+
+
+
+### The PCAP File
+
+The last file was a **pcap** dump. When opening it with [Wireshark](http:https://bt3gl.github.io/wiresharking-for-fun-or-profit.html), I verified it was really short, and the content was simply a [TCP handshake](http:https://www.inetdaemon.com/tutorials/internet/tcp/3-way_handshake.shtml). Right-clicking some packet and selecting *Follow TCP Stream* returned the dump of the connection suggested by the **client.py** script:
+
+![cyber](http:https://i.imgur.com/2Y6aaW1.png)
+
+However, we see that the database has already an entry for flag:
+
+```
+['flag', 'example']
+```
+
+The response **4f4b** is **OK** in ASCII, meaning that the switch **ENCRYPTION HEX** was on (it's good to keep in mind that the "encryption" is actually just an encoding in hex, *i.e*, completely reversible).
+
+Finally, our MD5 for the flag was printed as **b7133e9fe8b1abb64b72805d2d97495f**.
+
+As it was expected, searching for this hash in the usual channels (for example [here](http:https://hash-killer.com/), [here](http:https://www.md5this.com/), or [here](http:https://www.hashkiller.co.uk/)) was not successful: *brute force it is not the way to go*.
+
+
+### Solving the Challenge
+
+It's pretty clear from our **server.py** script that we could craft a direct request to the server to get our flag before it is hashed to MD5. For example, if the request *GET flag*,
+
+```py
+ elif cmd == 'GET':
+ reply(args + ': ' + db.get(args, ''))
+```
+
+is exactly like *MD5 flag*, without the hashing:
+
+```py
+ elif cmd == 'MD5':
+ reply(md5(db.get(args, '')))
+```
+
+However, we do not have the AES key used by the server, only an example of communication given by the PCAP file. How do we get to send a **GET flag** message?
+
+The first thing that comes to our minds is to use the network dump to replay the message, re-shaping it somehow to have a *GET flag*. Remember that the blocks have a size of 16, and we see two blocks that are particularly interesting:
+
+```
+ION HEX
+MD5 flag
+```
+
+and
+
+```
+edisStore...
+GET
+```
+
+Now we check how the oracle responds to several types of responses:
+
+```
+$ python client.py 54.148.249.150 4479
+```
+We are able to learn that if we send a **command without arguments** or an **invalid command**, the argument variables (*args*) is not overwritten: it gets the **same args value from the previous valid request**! That's wonderful!
+
+Now the solution is clear:
+
+1. We send the invalid command and a valid command with the argument that we will keep: ```ION HEX\nMD5 flag```.
+2. We send the invalid command and command without an argument: ```edisStore...\nGET``` (this will get the last valid argument (*flag*), returning us the flag!).
+

CTFs_and_WarGames/2014/ASIS-final/crypto_paillier/paillier.md

@@ -1,16 +1,6 @@
-Title: On Paillier, Binary Search, and the ASIS CTF 2014
-Date: 2014-10-13 3:30
-Category: Cryptography
-Tags: CTF, Paillier, Python, Binary_Search, Oracle, Decimal
+# On Paillier, Binary Search, and the ASIS CTF 2014
 
 
-![](http:https://i.imgur.com/7LMyBGx.png)
-
-The [ASIS CTF] was last weekend. Although I ended up not playing all I wanted, I did spend some time working on a crypto challenge that was worth a lot of points in the game. The challenge was about a system I never heard about before, the [Paillier cryptosystem].
-
-
-____
-
 ## The Cryptosystem
 
 The challenge was started by netcating to ```nc asis-ctf.ir 12445```:
@@ -392,11 +382,6 @@ ASIS_85c9febd4c15950ab1f19a6bd7a94f87
 
 ```
 
-Cool, right?
-
-If you think so, all scripts I mentioned are [here].
-
-Hack all the things!
 
 
 ----