Allocation of Resources Without Limits or Throttling

Opis

The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

Skutki

• Availability

  DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)

  When allocating resources without limits, an attacker could prevent other systems, applications, or processes from accessing the same type of resource. It can be easy for an attacker to consume many resources by rapidly making many requests or causing larger resources to be used than is needed.

Zapobieganie

• Requirements

  Clearly specify the minimum and maximum expectations for capabilities, and dictate which behaviors are acceptable when resource allocation reaches limits.

• Architecture and Design

  Limit the amount of resources that are accessible to unprivileged users. Set per-user limits for resources. Allow the system administrator to define these limits. Be careful to avoid CWE-410.

• Architecture and Design

  Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place, and it will help the administrator to identify who is committing the abuse. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.

• Implementation · Input Validation

  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, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

• Architecture and Design

  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.

• Architecture and Design

  Mitigation of resource exhaustion attacks requires that the target system either:

  - recognizes the attack and denies that user further access for a given amount of time, typically by using increasing time delays

  - uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed.

  The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.

  The second solution can be difficult to effectively institute -- and even when properly done, it does not provide a full solution. It simply requires more resources on the part of the attacker.

• Architecture and Design

  Ensure that protocols have specific limits of scale placed on them.

• Architecture and Design, Implementation

  If the program must fail, ensure that it fails gracefully (fails closed). There may be a temptation to simply let the program fail poorly in cases such as low memory conditions, but an attacker may be able to assert control before the software has fully exited. Alternately, an uncontrolled failure could cause cascading problems with other downstream components; for example, the program could send a signal to a downstream process so the process immediately knows that a problem has occurred and has a better chance of recovery.

  Ensure that all failures in resource allocation place the system into a safe posture.

• Operation, Architecture and Design · Resource Limitation

  Use quotas or other resource-limiting settings provided by the operating system or environment. For example, when managing system resources in POSIX, setrlimit() can be used to set limits for certain types of resources, and getrlimit() can determine how many resources are available. However, these functions are not available on all operating systems.

  When the current levels get close to the maximum that is defined for the application (see CWE-770), then limit the allocation of further resources to privileged users; alternately, begin releasing resources for less-privileged users. While this mitigation may protect the system from attack, it will not necessarily stop attackers from adversely impacting other users.

  Ensure that the application performs the appropriate error checks and error handling in case resources become unavailable (CWE-703).

Przykłady podatności

• CVE-2019-19911 Chain: Python library does not limit the resources used to process images that specify a very large number of bands (CWE-1284), leading to excessive memory consumption (CWE-789) or an integer overflow (CWE-190).
• CVE-2009-4017 Language interpreter does not restrict the number of temporary files being created when handling a MIME request with a large number of parts..
• CVE-2009-2726 Driver does not use a maximum width when invoking sscanf style functions, causing stack consumption.
• CVE-2009-2540 Large integer value for a length property in an object causes a large amount of memory allocation.
• CVE-2009-2054 Product allows exhaustion of file descriptors when processing a large number of TCP packets.
• CVE-2008-5180 Communication product allows memory consumption with a large number of SIP requests, which cause many sessions to be created.
• CVE-2008-1700 Product allows attackers to cause a denial of service via a large number of directives, each of which opens a separate window.
• CVE-2005-4650 CMS does not restrict the number of searches that can occur simultaneously, leading to resource exhaustion.
• CVE-2020-15100 web application scanner attempts to read an excessively large file created by a user, causing process termination
• CVE-2020-7218 Go-based workload orchestrator does not limit resource usage with unauthenticated connections, allowing a DoS by flooding the service

Słabość nadrzędna

• CWE-400 Uncontrolled Resource Consumption
• CWE-665 Improper Initialization

Słabości podrzędne

• CWE-774 Allocation of File Descriptors or Handles Without Limits or Throttling
• CWE-789 Memory Allocation with Excessive Size Value
• CWE-1325 Improperly Controlled Sequential Memory Allocation

Kiedy powstaje

• Architecture and Design — OMISSION: This weakness is caused by missing a security tactic during the architecture and design phase.
• Implementation
• Operation
• System Configuration

Dotyczy

Not Language-Specific, Not Technology-Specific

Uwagi

This entry is different from uncontrolled resource consumption (CWE-400) in that there are other weaknesses that are related to inability to control resource consumption, such as holding on to a resource too long after use, or not correctly keeping track of active resources so that they can be managed and released when they are finished (CWE-771).

Vulnerability theory is largely about how behaviors and resources interact. "Resource exhaustion" can be regarded as either a consequence or an attack, depending on the perspective. This entry is an attempt to reflect one of the underlying weaknesses that enable these attacks (or consequences) to take place.

Źródła

1. Detection and Prediction of Resource-Exhaustion Vulnerabilities — Joao Antunes, Nuno Ferreira Neves, Paulo Verissimo, Proceedings of the IEEE International Symposium on Software Reliability Engineering (ISSRE), 2008
2. Resource exhaustion — D.J. Bernstein
3. Resource exhaustion — Pascal Meunier, Secure Programming Educational Material, 2004
4. Writing Secure Code — Michael Howard, David LeBlanc, Chapter 17, "Protecting Against Denial of Service Attacks" Page 517, Microsoft Press, 2002
5. Real-Life Example of a 'Business Logic Defect' (Screen Shots!) — Rafal Los, 2011
6. Top 25 Series - Rank 22 - Allocation of Resources Without Limits or Throttling — Frank Kim, SANS Software Security Institute, 2010
7. The Art of Software Security Assessment — Mark Dowd, John McDonald, Justin Schuh, Chapter 10, "Resource Limits", Page 574, Addison Wesley, 2006