SSL Stripping

SSL stripping is a technique introduced by Moxie Marlinspike during BlackHat DC 2009, the website description of this technique goes like:

    It will transparently hijack HTTP traffic on a network, watch for HTTPS links and redirects, then map those links into either look-alike HTTP links or homograph-similar HTTPS links.

Long story short, this technique will replace every https link in webpages the target is browsing with http ones so, if a page would normally look like:
... Login ...

During a SSL stripping attack its HTML code will be modified as:

... Login ...

Being the man in the middle, this allow us to sniff and modify pages that normally we wouldn't be able to even see.

HSTS Bypass

SSL stripping worked quite well until 2010, when the HSTS specification was introduced, Wikipedia says:

    HTTP Strict Transport Security (HSTS) is a web security policy mechanism which helps to protect websites against protocol downgrade attacks and cookie hijacking. It allows web servers to declare that web browsers (or other complying user agents) should only interact with it using secure HTTPS connections, and never via the insecure HTTP protocol. HSTS is an IETF standards track protocol and is specified in RFC 6797.

Moreover HSTS policies have been prebuilt into major browsers meaning that now, even with a SSL stripping attack running, the browser will connect to HTTPS anyway, even if the http:// schema is specified, making the attack itself useless.

For this reason, Leonardo Nve Egea presented sslstrip+ ( or sslstrip2 ) during BlackHat Asia 2014. This tool was an improvement over the original Moxie's version, specifically created to bypass HSTS policies. Since HSTS rules most of the time are applied on a per-hostname basis, the trick is to downgrade HTTPS links to HTTP and to prepend some custom sub domain name to them. Every resulting link won't be valid for any DNS server, but since we're MITMing we can resolve these hostnames anyway.

Let's take the previous example page:

... Login ...

A HSTS bypass attack will change it to something like:

... Login ...

Notice that https has been downgraded to http and www replaced with wwww ).

When the "victim" will click on that link, no HSTS rule will be applied ( since there's no rule for such subdomain we just created ) and the MITM software ( BetterCap in our case ^_^ ) will take care of the DNS resolution, allowing us to see and alter the traffic we weren't supposed to see.

(кстати, тут прошу камрадов пояснить - это дсн спуффинг или обычный редирикт?)

www.facebook.com

[COLOR=rgb(226, 80, 65)]w[/COLOR]www.facebook.com

снова вопрос камрадам форума: с помощью какого, чер-возьми, инструмента зеркалировать фейсбук в режиме реального времени?! КАК?

SSLsplit is designed to transparently terminate connections that are redirected to it using a network address translation engine. SSLsplit then terminates SSL/TLS and initiates a new SSL/TLS connection to the original destination address, while logging all data transmitted. Besides NAT based operation, SSLsplit also supports static destinations and using the server name indicated by SNI as upstream destination. SSLsplit is purely a transparent proxy and cannot act as a HTTP or SOCKS proxy configured in a browser.

SSLsplit supports plain TCP, plain SSL, HTTP and HTTPS connections over both IPv4 and IPv6. It also has the ability to dynamically upgrade plain TCP to SSL in order to generically support SMTP STARTTLS and similar upgrade mechanisms. SSLsplit fully supports Server Name Indication (SNI) and is able to work with RSA, DSA and ECDSA keys and DHE and ECDHE cipher suites. Depending on the version of OpenSSL built against, SSLsplit supports SSL 3.0, TLS 1.0, TLS 1.1 and TLS 1.2, and optionally SSL 2.0 as well.

For SSL and HTTPS connections, SSLsplit generates and signs forged X509v3 certificates on-the-fly, mimicking the original server certificate’s subject DN, subjectAltName extension and other characteristics. SSLsplit has the ability to use existing certificates of which the private key is available, instead of generating forged ones. SSLsplit supports NULL-prefix CN certificates but otherwise does not implement exploits against specific certificate verification vulnerabilities in SSL/TLS stacks.