COMMON WEAKNESS ENUMERATIONDraft

CWE-99

Improper Control of Resource Identifiers ('Resource Injection')

The product receives input from an upstream component, but it does not restrict or incorrectly restricts the input before it is used as an identifier for a resource that may be outside the intended sphere of control.

Abstraction

Class

Structure

Simple

Likelihood of Exploit

High

Understand the problem

What is the problem?

The product receives input from an upstream component, but it does not restrict or incorrectly restricts the input before it is used as an identifier for a resource that may be outside the intended sphere of control.

Extended description

A resource injection issue occurs when the following two conditions are met: 1. An attacker can specify the identifier used to access a system resource. For example, an attacker might be able to specify part of the name of a file to be opened or a port number to be used. 1. By specifying the resource, the attacker gains a capability that would not otherwise be permitted. For example, the program may give the attacker the ability to overwrite the specified file, run with a configuration controlled by the attacker, or transmit sensitive information to a third-party server. This may enable an attacker to access or modify otherwise protected system resources.

Terminology

Alternate terms and usages

Insecure Direct Object Reference

OWASP uses this term, although it is effectively the same as resource injection.

Root cause

How and when does the problem arise?

Lifecycle phase

Architecture and Design

Lifecycle phase

Implementation

REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Risk

What does successful exploitation lead to?

Read Application DataModify Application DataRead Files or DirectoriesModify Files or Directories

Affected security scopes: Confidentiality, Integrity

An attacker could gain access to or modify sensitive data or system resources. This could allow access to protected files or directories including configuration files and files containing sensitive information.

Defence

How is it prevented and fixed?

Implementation

Input Validation

Detail
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, it can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Verification

How is it detected?

Automated Static Analysis

High
Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)