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CAPEC-36: Using Unpublished APIs

Using Unpublished APIs
Definition in a New Window Definition in a New Window
Attack Pattern ID: 36
Abstraction: Standard
Status: Draft
Completeness: Complete
Presentation Filter:
+ Summary

An adversary searches for and invokes APIs that the target system designers did not intend to be publicly available. If these APIs fail to authenticate requests the attacker may be able to invoke functionality they are not authorized for.

+ Attack Execution Flow
  1. Discover a service of interest by exploring service registry listings or by connecting on a known port or some similar means.

  2. Authenticate to the service, if required, in order to explore it.

  3. Determine the exposed interfaces by querying the registry as well as probably sniffing to expose interfaces that are not explicitly listed.

+ Attack Prerequisites
  • The architecture under attack must publish or otherwise make available services that clients can attach to, either in an unauthenticated fashion, or having obtained an authentication token elsewhere. The service need not be 'discoverable', but in the event it isn't it must have some way of being discovered by an attacker. This might include listening on a well-known port. Ultimately, the likelihood of exploit depends on discoverability of the vulnerable service.

+ Typical Severity


+ Typical Likelihood of Exploit

Likelihood: Medium

+ Methods of Attack
  • Analysis
  • API Abuse
+ Examples-Instances


To an extent, Google services (such as Google Maps) are all well-known examples. Calling these services, or extending them for one's own (perhaps very different) purposes is as easy as knowing they exist. Their unencumbered public use, however, is a purposeful aspect of Google's business model. Most organizations, however, do not have the same business model. Organizations publishing services usually fall back on thoughts that Attackers "will not know services exist" and that "even if they did, they wouldn't be able to access them because they're not on the local LAN." Simple threat modeling exercises usually uncovers simple attack vectors that can invalidate these assumptions.

+ Attacker Skills or Knowledge Required

Skill or Knowledge Level: Low

A number of web service digging tools are available for free that help discover exposed web services and their interfaces. In the event that a web service is not listed, the attacker does not need to know much more in addition to the format of web service messages that he can sniff/monitor for.

+ Resources Required

No special resources are required in order to conduct these attacks. Web service digging tools may be helpful.

+ Probing Techniques

Probing techniques should often follow normal means of identifying services. Attackers will simply have to execute code that sends the appropriate interrogating SOAP messages to suspected UDDI services (in web-services scenarios). Attackers will likely want to detect and query the organization's SOA Registry.

Probing techniques become more difficult when the service isn't advertised, or doesn't leverage discovery frameworks such as UDDI or the WS-I standard. In these cases, sniffing network traffic may suffice, depending on whether or not discovery occurs over a protected channel.

+ Solutions and Mitigations

Authenticating both services and their discovery, and protecting that authentication mechanism simply fixes the bulk of this problem. Protecting the authentication involves the standard means, including: 1) protecting the channel over which authentication occurs, 2) preventing the theft, forgery, or prediction of authentication credentials or the resultant tokens, or 3) subversion of password reset and the like.

+ Attack Motivation-Consequences
ScopeTechnical ImpactNote
Read application data
Gain privileges / assume identity
+ Relevant Security Requirements

Authenticate every request or message to a service

Do not rely on lack of discoverability to protect privileged functions within the service

+ Purposes
  • Penetration
+ CIA Impact
Confidentiality Impact: HighIntegrity Impact: MediumAvailability Impact: Low
+ Technical Context
Architectural Paradigms
+ Content History
CAPEC Content TeamThe MITRE Corporation2014-06-23Internal_CAPEC_Team
CAPEC Content TeamThe MITRE Corporation2015-12-07Updated Attack_Phases, Attack_Prerequisites, Description SummaryInternal
Previous Entry Names
DatePrevious Entry Name
2015-12-07Using Unpublished Web Service APIs
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Page Last Updated or Reviewed: May 01, 2017