Improper Control of Generation of Code ('Code Injection')
|ID: 94||Date: (C)2012-05-14 (M)2017-12-01|
|Type: weakness||Status: DRAFT|
|Abstraction Type: Class|
The software constructs all or part of a code segment using
externally-influenced input from an upstream component, but it does not
neutralize or incorrectly neutralizes special elements that could modify the
syntax or behavior of the intended code segment.
Extended DescriptionWhen software allows a user's input to contain code syntax, it might be
possible for an attacker to craft the code in such a way that it will alter
the intended control flow of the software. Such an alteration could lead to
arbitrary code execution.Injection problems encompass a wide variety of issues -- all mitigated in
very different ways. For this reason, the most effective way to discuss
these weaknesses is to note the distinct features which classify them as
injection weaknesses. The most important issue to note is that all injection
problems share one thing in common -- i.e., they allow for the injection of
control plane data into the user-controlled data plane. This means that the
execution of the process may be altered by sending code in through
legitimate data channels, using no other mechanism. While buffer overflows,
and many other flaws, involve the use of some further issue to gain
execution, injection problems need only for the data to be parsed. The most
classic instantiations of this category of weakness are SQL injection and
format string vulnerabilities.
Likelihood of Exploit: Medium
Applicable PlatformsLanguage Class: SometimesLanguage Class: Interpreted languages
Time Of Introduction
- Architecture and Design
Related Attack Patterns
|Access_Control ||Bypass protection
mechanism ||In some cases, injectable code controls authentication; this may lead
to a remote vulnerability. |
|Access_Control ||Gain privileges / assume
identity ||Injected code can access resources that the attacker is directly
prevented from accessing. |
|IntegrityConfidentialityAvailability ||Execute unauthorized code or
commands ||Code injection attacks can lead to loss of data integrity in nearly
all cases as the control-plane data injected is always incidental to
data recall or writing. Additionally, code injection can often result in
the execution of arbitrary code. |
|Non-Repudiation ||Hide activities ||Often the actions performed by injected control code are
|Architecture and Design || ||Refactor your program so that you do not have to dynamically generate
code. || || |
|Architecture and Design || ||Run your code in a "jail" or similar sandbox environment that enforces
strict boundaries between the process and the operating system. This may
effectively restrict which code can be executed by your software.Examples include the Unix chroot jail and AppArmor. In general,
managed code may provide some protection.This may not be a feasible solution, and it only limits the impact to
the operating system; the rest of your application may still be subject
to compromise.Be careful to avoid CWE-243 and other weaknesses related to jails. || || |
|Implementation ||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.To reduce the likelihood of code injection, use stringent whitelists
that limit which constructs are allowed. If you are dynamically
constructing code that invokes a function, then verifying that the input
is alphanumeric might be insufficient. An attacker might still be able
to reference a dangerous function that you did not intend to allow, such
as system(), exec(), or exit(). || || |
|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. || || |
|Operation ||Compilation or Build HardeningEnvironment Hardening ||Run the code in an environment that performs automatic taint
propagation and prevents any command execution that uses tainted
variables, such as Perl's "-T" switch. This will force the program to
perform validation steps that remove the taint, although you must be
careful to correctly validate your inputs so that you do not
accidentally mark dangerous inputs as untainted (see CWE-183 and
CWE-184). || || |
|CWE-94 ChildOf CWE-896 ||Category ||CWE-888 || |
Demonstrative Examples (Details)
- This example attempts to write user messages to a message file and
allow users to view them. (Demonstrative Example Id DX-32)
- edit-config.pl: This CGI script is used to modify settings in a
configuration file. (Demonstrative Example Id DX-31)
- CVE-2008-5071 : Eval injection in PHP program.
- CVE-2002-1750 : Eval injection in Perl program.
- CVE-2008-5305 : Eval injection in Perl program using an ID that should only contain hyphens and numbers.
- CVE-2002-1752 : Direct code injection into Perl eval function.
- CVE-2002-1753 : Eval injection in Perl program.
- CVE-2005-1527 : Direct code injection into Perl eval function.
- CVE-2005-2837 : Direct code injection into Perl eval function.
- CVE-2005-1921 : MFV. code injection into PHP eval statement using nested constructs that should not be nested.
- CVE-2005-2498 : MFV. code injection into PHP eval statement using nested constructs that should not be nested.
- CVE-2005-3302 : Code injection into Python eval statement from a field in a formatted file.
- CVE-2007-1253 : Eval injection in Python program.
- CVE-2001-1471 : chain: Resultant eval injection. An invalid value prevents initialization of variables, which can be modified by attacker and later injected into PHP eval statement.
- CVE-2002-0495 : Perl code directly injected into CGI library file from parameters to another CGI program.
- CVE-2005-1876 : Direct PHP code injection into supporting template file.
- CVE-2005-1894 : Direct code injection into PHP script that can be accessed by attacker.
- CVE-2003-0395 : PHP code from User-Agent HTTP header directly inserted into log file implemented as PHP script.
For more examples, refer to CVE relations in the bottom box.
White Box Definitions None
Black Box Definitions None
|PLOVER ||CODE ||Code Evaluation and Injection || |
- Michael Howard David LeBlanc John Viega .24 Deadly Sins of Software Security. McGraw-Hill. Section:'"Sin 3: Web-Client Related Vulnerabilities (XSS)." Page
63'. Published on 2010.