Tag Archives: Improper Control of Filename for Include/Require Statement in PHP Program (‘PHP Remote File Inclusion’)

CWE

CWE-98 – Improper Control of Filename for Include/Require Statement in PHP Program (‘PHP Remote File Inclusion’)

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Description

The PHP application receives input from an upstream component, but it does not restrict or incorrectly restricts the input before its usage in “require,” “include,” or similar functions.

In certain versions and configurations of PHP, this can allow an attacker to specify a URL to a remote location from which the software will obtain the code to execute. In other cases in association with path traversal, the attacker can specify a local file that may contain executable statements that can be parsed by PHP.

Modes of Introduction:

– Implementation

Likelihood of Exploit: High

 

Related Weaknesses

CWE-706
CWE-829
CWE-94
CWE-426

 

Consequences

Integrity, Confidentiality, Availability: Execute Unauthorized Code or Commands

The attacker may be able to specify arbitrary code to be executed from a remote location. Alternatively, it may be possible to use normal program behavior to insert php code into files on the local machine which can then be included and force the code to execute since php ignores everything in the file except for the content between php specifiers.

 

Potential Mitigations

Phase: Architecture and Design

Effectiveness:

Description: 

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

Phase: Architecture and Design

Effectiveness:

Description: 

Phase: Architecture and Design

Effectiveness:

Description: 

For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

Phase: Architecture and Design, Operation

Effectiveness: Limited

Description: 

The effectiveness of this mitigation depends on the prevention capabilities of the specific sandbox or jail being used and might only help to reduce the scope of an attack, such as restricting the attacker to certain system calls or limiting the portion of the file system that can be accessed.

Phase: Architecture and Design, Operation

Effectiveness:

Description: 

Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.

Phase: Implementation

Effectiveness: High

Description: 

Phase: Architecture and Design, Operation

Effectiveness:

Description: 

Phase: Architecture and Design, Implementation

Effectiveness:

Description: 

Phase: Operation

Effectiveness: Moderate

Description: 

Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.

An application firewall might not cover all possible input vectors. In addition, attack techniques might be available to bypass the protection mechanism, such as using malformed inputs that can still be processed by the component that receives those inputs. Depending on functionality, an application firewall might inadvertently reject or modify legitimate requests. Finally, some manual effort may be required for customization.

Phase: Operation, Implementation

Effectiveness:

Description: 

Develop and run your code in the most recent versions of PHP available, preferably PHP 6 or later. Many of the highly risky features in earlier PHP interpreters have been removed, restricted, or disabled by default.

Phase: Operation, Implementation

Effectiveness:

Description: 

Phase: Operation

Effectiveness: High

Description: 

Set allow_url_fopen to false, which limits the ability to include files from remote locations.

Be aware that some versions of PHP will still accept ftp:// and other URI schemes. In addition, this setting does not protect the code from path traversal attacks (CWE-22), which are frequently successful against the same vulnerable code that allows remote file inclusion.

CVE References

 

  • CVE-2004-0285
    • Modification of assumed-immutable configuration variable in include file allows file inclusion via direct request.
  • CVE-2004-0030
    • Modification of assumed-immutable configuration variable in include file allows file inclusion via direct request.
  • CVE-2004-0068
    • Modification of assumed-immutable configuration variable in include file allows file inclusion via direct request.
  • CVE-2005-2157
    • Modification of assumed-immutable configuration variable in include file allows file inclusion via direct request.
  • CVE-2005-2162
    • Modification of assumed-immutable configuration variable in include file allows file inclusion via direct request.
  • CVE-2005-2198
    • Modification of assumed-immutable configuration variable in include file allows file inclusion via direct request.
  • CVE-2004-0128
    • Modification of assumed-immutable variable in configuration script leads to file inclusion.
  • CVE-2004-0127
    • Directory traversal vulnerability in PHP include statement.
  • CVE-2005-1971
    • Directory traversal vulnerability in PHP include statement.
  • CVE-2005-3335
    • PHP file inclusion issue, both remote and local; local include uses “..” and “%00” characters as a manipulation, but many remote file inclusion issues probably have this vector.
  • CVE-2009-1936
    • chain: library file sends a redirect if it is directly requested but continues to execute, allowing remote file inclusion and path traversal.