CAPEC-12 - Choosing a Message/Channel Identifier on a Public/Multicast Channel

Attackers aware that more data is being fed into a multicast or public information distribution means can 'select' information bound only for another client, even if the distribution means itself forces users to authenticate in order to connect initially.

Doing so allows the attacker to gain access to possibly privileged information, possibly perpetrate other attacks through the distribution means by impersonation.

If the channel/message being manipulated is an input rather than output mechanism for the system, (such as a command bus), this style of attack could change its identifier from a less privileged to more so privileged channel or command.

Severity

Likelihood

Confidentiality

Integrity

Availability

  • Purposes 1
  • Penetration
  • Sec Principles 1
  • Complete Mediation
  • Scopes 2
  • Read application data
  • Confidentiality
  • Gain privileges / assume identity
  • Authorization
  • Access_Control
  • Confidentiality

Low level: All the attacker needs to discover is the format of the messages on the channel/distribution means and the particular identifier used within the messages.

Information and client-sensitive (and client-specific) data must be present through a distribution channel available to all users.

Distribution means must code (through channel, message identifiers, or convention) message destination in a manner visible within the distribution means itself (such as a control channel) or in the messages themselves.

The Attacker needs the ability to control source code or application configuration responsible for selecting which message/channel id is absorbed from the public distribution means.

Assisted protocol analysis: because the protocol under attack is a public channel, or one in which the attacker likely has authorized access to, they need simply to decode the aspect of channel or message interpretation that codes for message identifiers.

Probing is as simple as changing this value and watching its effect.

Use Authentication Mechanisms, Where Appropriate, Correctly

Use Authorization Mechanisms Correctly: this refers to Ambiguity of authentication. Many authorization systems use ambiguous symbols (i.e., principal names) to identify principals allowing circumvention of authorization by using a different, though equivalent, principal name. For example, there are many implementations for restricting remote host access to local services that may allow many proper (but apparently different) names for unique hosts (e.g., fully qualified domain names, shortened names, CNAMEs, IPv4 addresses, IPv6 addresses).

Step 1 -

Determine the nature of messages being transported as well as the identifiers to be used as part of the attack.


Step 1 -

If required, authenticate to the distribution channel.

Step 2 -

If any particular client's information is available through the transport means simply by selecting a particular identifier, an attacker can simply provide that particular identifier..

Step 3 -

Attackers with client access connecting to output channels could change their channel identifier and see someone else's (perhaps more privileged) data..


Associate some ACL (in the form of a token) with an authenticated user which they provide middleware. The middleware uses this token as part of its channel/message selection for that client, or part of a discerning authorization decision for privileged channels/messages.
The purpose is to architect the system in a way that associates proper authentication/authorization with each channel/message.

Re-architect system input/output channels as appropriate to distribute self-protecting data. That is, encrypt (or otherwise protect) channels/messages so that only authorized readers can see them.