This attack further exploits the SSL secure Renegotiation feature to trigger thousands of renegotiations via single TCP connection.

Usage

./thc-ssl-dos 127.3.133.7 443
Handshakes 0 [0.00 h/s], 0 Conn, 0 Err
Secure Renegotiation support: yes
Handshakes 0 [0.00 h/s], 97 Conn, 0 Err
Handshakes 68 [67.39 h/s], 97 Conn, 0 Err
Handshakes 148 [79.91 h/s], 97 Conn, 0 Err
Handshakes 228 [80.32 h/s], 100 Conn, 0 Err
Handshakes 308 [80.62 h/s], 100 Conn, 0 Err
Handshakes 390 [81.10 h/s], 100 Conn, 0 Err
Handshakes 470 [80.24 h/s], 100 Conn, 0 Err

Comparing flood DDoS vs. SSL-Exhaustion attack

A traditional flood DDoS attack cannot be mounted from a single DSL connection. This is because the bandwidth of a server is far superior to the bandwidth of a DSL connection: A DSL connection is not an equal opponent to challenge the bandwidth of a server.

This is turned upside down for THC-SSL-DOS: The processing capacity for SSL handshakes is far superior at the client side: A laptop on a DSL connection can challenge a server on a 30Gbit link. Traditional DDoS attacks based on flooding are sub optimal: Servers are prepared to handle large amount of traffic and clients are constantly sending requests to the server even when not under attack.

The SSL-handshake is only done at the beginning of a secure session and only if security is required. Servers are _not_ prepared to handle large amount of SSL Handshakes. The worst attack scenario is an SSL-Exhaustion attack mounted from thousands of clients (SSL-DDoS).

Tips & Tricks for Whitehats

1. The average server can do 300 handshakes per second. This would require 10-25% of your laptops CPU.
2. Use multiple hosts (SSL-DOS) if an SSL Accelerator is used.
3. Be smart in target acquisition: The HTTPS Port (443) is not always the best choice. Other SSL enabled ports are more unlikely to use an SSL Accelerator (like the POP3S, SMTPS, … or the secure database port).

Counter measurements

No real solutions exists. The following steps can mitigate (but not solve) the problem:

1. Disable SSL-Renegotiation
2. Invest into SSL Accelerator

Either of these countermeasures can be circumventing by modifying THC-SSL-DOS. A better solution is desireable. Somebody should fix this.

You can download THC-SSL-DOS here:

Windows: thc-ssl-dos-1.4-win-bin.zip
Linux: thc-ssl-dos-1.4.tar.gz

Or read more here.

We first wrote about Complemento 0.4b a little while ago when it first hit the public domain just last month (December 2008).

Now there have been 2 major updated versions, the latest being 0.6.

What is Complemento?

Complemento is a collection of tools that the author originally created for his own personal toolchain for solving some problems or just for fun. Now he has decided to release it to the public.

LetDown is a TCP flooder written after the author read the article by fyodor entitled article “TCP Resource Exhaustion and Botched Disclosure“. It has an (experimental) userland TCP/IP stack, and support multistage payloads for complex protocols, fragmentation of packets and variable TCP window.

ReverseRaider is a domain scanner that uses brute force wordlist scanning for finding a target sub-domains or reverse resolution for a range of ip addresses. This is similar to some of the functionality in DNSenum. It supports permutation on wordlist and IPv6.

Httsquash is an HTTP server scanner, banner grabber and data retriever. It can be used for scanning large ranges of IP addresses and finding devices or HTTP servers (there is an alpha version of a GUI for this). It supports IPv6 and personalized HTTP requests.

Improvements for v0.6

LetDown:

• New (experimental) userland TCP stack
• Support for multistage payloads (for complex and stateful protocol, such as FTP, SMTP…)
• Variable TCP Window size
• Fragmentation of packets
• Polite mode (ACK received packets and/or closing the connection with FIR or RST packets)

ReverseRaider:

• Support for IPv6

HttSquash:

• Support for IPv6

You can download Complemento v0.6 here:

complemento-0.6

Or read more here.

An interesting collection of tools for pen-testing including a DoS tool (something you don’t often see publicly released).

Complemento is a collection of tools that the author originally created for his own personal toolchain for solving some problems or just for fun. Now he has decided to release it to the public.

The Tools

LetDown is a TCP flooder written after the author read the article by fyodor entitled article “TCP Resource Exhaustion and Botched Disclosure“.

ReverseRaider is a domain scanner that uses brute force wordlist scanning for finding a target sub-domains or reverse resolution for a range of ip addresses. This is similar to some of the functionality in DNSenum.

Httsquash is an HTTP server scanner, banner grabber and data retriever. It can be used for scanning large ranges of IP addresses and finding devices or HTTP servers (there is an alpha version of a GUI for this).

You can download Complemento v0.4b here:

complemento-0.4b

Or read more here.