Coding 101 13

Welcome to Coding 101 - It's the TWiT show that gives YOU the knowledge to live in the wonderful world of the programmer. This week we are introducing our newest module, Python with Code Warrior Dale Chase!

To see all the code used in today's episode, go to Our Github Repository for Module 2

Loops (Recap)

• As we may recall, loops are an easy way to reuse code.
• It allows us to "loop" a section of code so that it doesn't have to be writen over and over.

While Loops

While loops in Python work very much like they do in C#

They use some sort of counter and some sort of relational true/false statement. The while loop will continue to run as long as the statement is true. The true/false statement is pre-test, meaning that it will evaluate the statement BEFORE the loop code is executed.

Code Sample:

counter = 0

while counter < 5:

counter = counter +1

print counter

Output:
1
2
3
4
5

Sanitizing your Input! The Heartbleed Bug

What is the Hearbeat?

• The problem lies in the "Hearbeart"
  • It's a way to keep a SECURE TLS session alive /// to keep it from "timing out"
  • The Heartbeat is a payload of arbitrary data which is sent from one end of the connection to the other, and back again.
  • If the heartbeat makes the round trip intact, then both sides of the connection know that the connection is still active and still secure.

Here is the OpenSSL Cod

(The Bug starts on Line 3972)

/* Read type and payload length first */

hbtype = *p++;

n2s(p, payload);

pl = p;

hbtype is the TYPE of data

P++ increments the pointer

p is the pointer for the payload

payload is the length of the payload

The problem is that the SENDER gets to set the "payload" length and the code never checks to see if the sent length matches the recieved length of the payload.

The Crux of the Matter:

• The Hearbleed bug stems from code that does not check to make sure it's recieving into memory what it expected.
• In other words... IT DIDN'T SANITIZE IT'S INPUT!

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• Transcripts: Coding 101 13 (Transcript)