An attacker initiates cross domain HTTP / GET requests and times the server responses. The timing of these responses may leak important information on what is happening on the server. Browser's same origin policy prevents the attacker from directly reading the server responses (in the absence of any other weaknesses), but does not prevent the attacker from timing the responses to requests that the attacker issued cross domain.
Extended Description
For GET requests an attacker could for instance leverage the "img" tag in conjunction with "onload() / onerror()" javascript events. For the POST requests, an attacker could leverage the "iframe" element and leverage the "onload()" event. There is nothing in the current browser security model that prevents an attacker to use these methods to time responses to the attackers' cross domain requests. The timing for these responses leaks information. For instance, if a victim has an active session with their online e-mail account, an attacker could issue search requests in the victim's mailbox. While the attacker is not able to view the responses, based on the timings of the responses, the attacker could ask yes / no questions as to the content of victim's e-mails, who the victim e-mailed, when, etc. This is but one example; There are other scenarios where an attacker could infer potentially sensitive information from cross domain requests by timing the responses while asking the right questions that leak information.
Typical Severity
Medium
Relationships
This table shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf and ParentOf, and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.
Nature
Type
ID
Name
ChildOf
Standard Attack Pattern - A standard level attack pattern in CAPEC is focused on a specific methodology or technique used in an attack. It is often seen as a singular piece of a fully executed attack. A standard attack pattern is meant to provide sufficient details to understand the specific technique and how it attempts to accomplish a desired goal. A standard level attack pattern is a specific type of a more abstract meta level attack pattern.
Determine service to send cross domain requests to: The adversary first determines which service they will be sending the requests to
Experiment
Send and time various cross domain requests: Adversaries will send a variety of cross domain requests to the target, timing the time it takes for the target to respond. Although they won't be able to read the response, the adversary can use the time to infer information about what the service did upon receiving the request.
Techniques
Using a GET request, leverage the "img" tag in conjunction with "onload() / onerror()" javascript events to time a response
Using a POST request, leverage the "iframe" element and use the "onload()" event to time a response
Exploit
Infer information from the response time: After obtaining reponse times to various requests, the adversary will compare these times and infer potentially sensitive information. An example of this could be asking a service to retrieve information and random usernames. If one request took longer to process, it is likely that a user with that username exists, which could be useful knowledge to an adversary.
Techniques
Compare timing of different requests to infer potentially sensitive information about a target service
Prerequisites
Ability to issue GET / POST requests cross domainJava Script is enabled in the victim's browserThe victim has an active session with the site from which the attacker would like to receive informationThe victim's site does not protect search functionality with cross site request forgery (CSRF) protection
Skills Required
[Level: Low]
Some knowledge of Java Script
Resources Required
Ability to issue GET / POST requests cross domain
Consequences
This table specifies different individual consequences associated with the attack pattern. The Scope identifies the security property that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in their attack. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a pattern will be used to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Scope
Impact
Likelihood
Confidentiality
Read Data
Mitigations
Design: The victim's site could protect all potentially sensitive functionality (e.g. search functions) with cross site request forgery (CSRF) protection and not perform any work on behalf of forged requests
Design: The browser's security model could be fixed to not leak timing information for cross domain requests
Related Weaknesses
A Related Weakness relationship associates a weakness with this attack pattern. Each association implies a weakness that must exist for a given attack to be successful. If multiple weaknesses are associated with the attack pattern, then any of the weaknesses (but not necessarily all) may be present for the attack to be successful. Each related weakness is identified by a CWE identifier.
Description
This table shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf and ParentOf, and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.
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