Vulnerabilities > CVE-2017-12735 - Man-in-the-Middle vulnerability in Siemens Logo! 8 BM Firmware

An attacker leverages a man in the middle attack in order to bypass the same origin policy protection in the victim's browser. This active man in the middle attack could be launched, for instance, when the victim is connected to a public WIFI hot spot. An attacker is able to intercept requests and responses between the victim's browser and some non-sensitive website that does not use TLS. For instance, the victim may be checking flight or weather information. When an attacker intercepts a response bound to the victim, an attacker adds an iFrame (which is possibly invisible) to the response referencing some domain with sensitive functionality and forwards the response to the victim. The victim's browser than automatically initiates an unauthorized request to the site with sensitive functionality. The same origin policy would prevent making these requests to a site other than the one from which the Java Script came, but the attacker once again uses active man in the middle to intercept these automatic requests and redirect them to the domain / service with sensitive functionality. Any persistent cookies that the victim has in his or her browser would be used for these unauthorized requests. The attacker thus actively directs the victim to a site with sensitive functionality. When the site with sensitive functionality responds back to the victim's request, an active man in the middle attacker intercepts these responses, injects his or her own malicious Java Script into these responses, and forwards to the victim's browser. In the victim's browser, that Java Script executes under the restrictions of the site with sensitive functionality and can essentially be used to continue to interact with the sensitive site. So an attacker can execute scripts within the victim's browser on any domains the attacker desires. The attacker is able to use this technique to steal cookies from the victim's browser for whatever site the attacker wants. This applies to both persistent cookies and HTTP only cookies (unlike traditional XSS attacks). An attacker is also able to use this technique to steal authentication credentials for sites that only encrypt the login form, but do not require a secure channel for the initial request to get to the page with the login form. Further the attacker is also able to steal any autocompletion information. This attack pattern can also be used to enable session fixation and cache poisoning attacks. Additional attacks can be enabled as well.

This attack utilizes a REST(REpresentational State Transfer)-style applications' trust in the system resources and environment to place man in the middle once SSL is terminated. Rest applications premise is that they leverage existing infrastructure to deliver web services functionality. An example of this is a Rest application that uses HTTP Get methods and receives a HTTP response with an XML document. These Rest style web services are deployed on existing infrastructure such as Apache and IIS web servers with no SOAP stack required. Unfortunately from a security standpoint, there frequently is no interoperable identity security mechanism deployed, so Rest developers often fall back to SSL to deliver security. In large data centers, SSL is typically terminated at the edge of the network - at the firewall, load balancer, or router. Once the SSL is terminated the HTTP request is in the clear (unless developers have hashed or encrypted the values, but this is rare). The attacker can utilize a sniffer such as Wireshark to snapshot the credentials, such as username and password that are passed in the clear once SSL is terminated. Once the attacker gathers these credentials, they can submit requests to the web service provider just as authorized user do. There is not typically an authentication on the client side, beyond what is passed in the request itself so once this is compromised, then this is generally sufficient to compromise the service's authentication scheme.

This type of attack targets the communication between two components (typically client and server). The attacker places himself in the communication channel between the two components. Whenever one component attempts to communicate with the other (data flow, authentication challenges, etc.), the data first goes to the attacker, who has the opportunity to observe or alter it, and it is then passed on to the other component as if it was never intercepted. This interposition is transparent leaving the two compromised components unaware of the potential corruption or leakage of their communications. The potential for Man-in-the-Middle attacks yields an implicit lack of trust in communication or identify between two components.