CWE-99: Improper Control of Resource Identifiers ('Resource Injection')
Improper Control of Resource Identifiers ('Resource Injection')
Weakness ID: 99 (Weakness Base)
Status: Draft
Description
Description Summary
The software 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
This may enable an attacker to access or modify otherwise protected system resources.
Alternate Terms
Insecure Direct Object Reference:
OWASP uses this term, although is is effectively the same as resource
injection.
Time of Introduction
Architecture and Design
Implementation
Applicable Platforms
Languages
All
Common Consequences
Scope
Effect
Confidentiality
Integrity
Technical Impact: Read application
data; Modify application
data; Read files or
directories; Modify files or
directories
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.
Likelihood of Exploit
High
Demonstrative Examples
Example 1
The following Java code uses input from an HTTP request to create a
file name. The programmer has not considered the possibility that an
attacker could provide a file name such as "../../tomcat/conf/server.xml",
which causes the application to delete one of its own configuration
files.
File rFile = new File("/usr/local/apfr/reports/" + rName);
...
rFile.delete();
Example 2
The following code uses input from the command line to determine
which file to open and echo back to the user. If the program runs with
privileges and malicious users can create soft links to the file, they can
use the program to read the first part of any file on the
system.
(Bad Code)
Example
Language: C++
ifstream ifs(argv[0]);
string s;
ifs >> s;
cout << s;
The kind of resource the data affects indicates the kind of content
that may be dangerous. For example, data containing special characters
like period, slash, and backslash, are risky when used in methods that
interact with the file system. (Resource injection, when it is related
to file system resources, sometimes goes by the name "path
manipulation.") Similarly, data that contains URLs and URIs is risky for
functions that create remote connections.
Potential Mitigations
Phase: Implementation
Strategy: Input Validation
Assume all input is malicious. Use an "accept known good" input
validation strategy, i.e., use a whitelist 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
(i.e., do not rely on a blacklist). A blacklist 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, blacklists can be useful for detecting potential
attacks or determining which inputs are so malformed that they should be
rejected outright.
Other Notes
A resource injection issue occurs when the following two conditions are
met:
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.
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.
Note: Resource injection that involves resources stored on the filesystem
goes by the name path manipulation and is reported in a separate category.
See the path manipulation description for further details of this
vulnerability.
Weakness Ordinalities
Ordinality
Description
Primary
(where
the weakness exists independent of other weaknesses)
2. a statement that allocates a System Resource using name where the
input is part of the name
3. end statement that accesses the System Resource where
a. the name of the System Resource violates protection
Maintenance Notes
The relationship between CWE-99 and CWE-610 needs further investigation and clarification. They might be duplicates. CWE-99 "Resource Injection," as originally defined in Seven Pernicious Kingdoms taxonomy, emphasizes the "identifier used to access a system resource" such as a file name or port number, yet it explicitly states that the "resource injection" term does not apply to "path manipulation," which effectively identifies the path at which a resource can be found and could be considered to be one aspect of a resource identifier. Also, CWE-610 effectively covers any type of resource, whether that resource is at the system layer, the application layer, or the code layer.
Description
