External Control of Critical State Data
|ID: 642||Date: (C)2012-05-14 (M)2018-07-27|
|Type: weakness||Status: DRAFT|
|Abstraction Type: Class|
The software stores security-critical state information about
its users, or the software itself, in a location that is accessible to
Extended DescriptionIf an attacker can modify the state information without detection, then it
could be used to perform unauthorized actions or access unexpected
resources, since the application programmer does not expect that the state
can be changed.State information can be stored in various locations such as a cookie, in
a hidden web form field, input parameter or argument, an environment
variable, a database record, within a settings file, etc. All of these
locations have the potential to be modified by an attacker. When this state
information is used to control security or determine resource usage, then it
may create a vulnerability. For example, an application may perform
authentication, then save the state in an "authenticated=true" cookie. An
attacker may simply create this cookie in order to bypass the
Enabling Factors for ExploitationAn application maintains its own state and/or user state (i.e. application
is stateful).State information can be affected by the user of an application through
some means other than the legitimate state transitions (e.g. logging into
the system, purchasing an item, making a payment, etc.)An application does not have means to detect state tampering and behave in
a fail safe manner.
Likelihood of Exploit: High
Applicable PlatformsLanguage Class: AllTechnology Class: OftenTechnology Class: Web-Server
Time Of Introduction
- Architecture and Design
Related Attack Patterns
|Access_Control ||Bypass protection
mechanismGain privileges / assume
identity ||An attacker could potentially modify the state in malicious ways. If
the state is related to the privileges or level of authentication that
the user has, then state modification might allow the user to bypass
authentication or elevate privileges. |
|Confidentiality ||Read application
data ||The state variables may contain sensitive information that should not
be known by the client. |
|Availability ||DoS: crash / exit /
restart ||By modifying state variables, the attacker could violate the
application's expectations for the contents of the state, leading to a
denial of service due to an unexpected error condition. |
|Architecture and Design || ||Understand all the potential locations that are accessible to
attackers. For example, some programmers assume that cookies and hidden
form fields cannot be modified by an attacker, or they may not consider
that environment variables can be modified before a privileged program
is invoked. || || |
|Architecture and Design ||Identify and Reduce Attack Surface ||Store state information and sensitive data on the server side only.Ensure that the system definitively and unambiguously keeps track of
its own state and user state and has rules defined for legitimate state
transitions. Do not allow any application user to affect state directly
in any way other than through legitimate actions leading to state
transitions.If information must be stored on the client, do not do so without
encryption and integrity checking, or otherwise having a mechanism on
the server side to catch tampering. Use a message authentication code
(MAC) algorithm, such as Hash Message Authentication Code (HMAC)
[R.642.2]. Apply this against the state or sensitive data that you have
to expose, which can guarantee the integrity of the data - i.e., that
the data has not been modified. Ensure that you use an algorithm with a
strong hash function (CWE-328). || || |
|Architecture and Design || ||Store state information on the server side only. Ensure that the
system definitively and unambiguously keeps track of its own state and
user state and has rules defined for legitimate state transitions. Do
not allow any application user to affect state directly in any way other
than through legitimate actions leading to state transitions. || || |
|Architecture and Design ||Libraries or Frameworks ||Use a vetted library or framework that does not allow this weakness to
occur or provides constructs that make this weakness easier to
avoid.With a stateless protocol such as HTTP, use some frameworks can
maintain the state for you.Examples include ASP.NET View State and the OWASP ESAPI Session
Management feature.Be careful of language features that provide state support, since
these might be provided as a convenience to the programmer and may not
be considering security. || || |
|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. || || |
|OperationImplementation ||Environment Hardening ||When using PHP, configure the application so that it does not use
register_globals. During implementation, develop the application so that
it does not rely on this feature, but be wary of implementing a
register_globals emulation that is subject to weaknesses such as CWE-95,
CWE-621, and similar issues. || || |
|Testing || ||Use automated static analysis tools that target this type of weakness.
Many modern techniques use data flow analysis to minimize the number of
false positives. This is not a perfect solution, since 100% accuracy and
coverage are not feasible. || || |
|Testing || ||Use dynamic tools and techniques that interact with the software using
large test suites with many diverse inputs, such as fuzz testing
(fuzzing), robustness testing, and fault injection. The software's
operation may slow down, but it should not become unstable, crash, or
generate incorrect results. || || |
|Testing || ||Use tools and techniques that require manual (human) analysis, such as
penetration testing, threat modeling, and interactive tools that allow
the tester to record and modify an active session. These may be more
effective than strictly automated techniques. This is especially the
case with weaknesses that are related to design and business
rules. || || |
|CWE-642 ChildOf CWE-895 ||Category ||CWE-888 || |
Demonstrative Examples (Details)
- In the following example, an authentication flag is read from a
browser cookie, thus allowing for external control of user state
- The following code segment implements a basic server that uses the
"ls" program to perform a directory listing of the directory that is listed
in the "HOMEDIR" environment variable. The code intends to allow the user to
specify an alternate "LANG" environment variable. This causes "ls" to
customize its output based on a given language, which is an important
capability when supporting internationalization.
- The following code uses input from a configuration file to determine
which file to open and echo back to the user. If the program runs with
privileges and malicious users can change the configuration file, they can
use the program to read any file on the system that ends with the extension
.txt. (Demonstrative Example Id DX-66)
- The following 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
(CWE-22). (Demonstrative Example Id DX-65)
- This code prints all of the running processes belonging to the
current user. (Demonstrative Example Id DX-68)
- This program is intended to execute a command that lists the
contents of a restricted directory, then performs other actions. Assume that
it runs with setuid privileges in order to bypass the permissions check by
the operating system. (Demonstrative Example Id DX-67)
- CVE-2005-2428 : Mail client stores password hashes for unrelated accounts in a hidden form field.
- CVE-2008-0306 : Privileged program trusts user-specified environment variable to modify critical configuration settings.
- CVE-1999-0073 : Telnet daemon allows remote clients to specify critical environment variables for the server, leading to code execution.
- CVE-2007-4432 : Untrusted search path vulnerability through modified LD_LIBRARY_PATH environment variable.
- CVE-2006-7191 : Untrusted search path vulnerability through modified LD_LIBRARY_PATH environment variable.
- CVE-2008-5738 : Calendar application allows bypass of authentication by setting a certain cookie value to 1.
- CVE-2008-5642 : Setting of a language preference in a cookie enables path traversal attack.
- CVE-2008-5125 : Application allows admin privileges by setting a cookie value to "admin."
- CVE-2008-5065 : Application allows admin privileges by setting a cookie value to "admin."
- CVE-2008-4752 : Application allows admin privileges by setting a cookie value to "admin."
- CVE-2000-0102 : Shopping cart allows price modification via hidden form field.
- CVE-2000-0253 : Shopping cart allows price modification via hidden form field.
- CVE-2008-1319 : Server allows client to specify the search path, which can be modified to point to a program that the client has uploaded.
For more examples, refer to CVE relations in the bottom box.
White Box Definitions None
Black Box Definitions None
- OWASP .Top 10 2007-Insecure Direct Object Reference. Published on 2007.
- .HMAC. Wikipedia. 2011-08-18.
- Michael Howard David LeBlanc John Viega .24 Deadly Sins of Software Security. McGraw-Hill. Section:'"Sin 4: Use of Magic URLs, Predictable Cookies, and Hidden
Form Fields." Page 75'. Published on 2010.