Download of Code Without Integrity Check
|ID: 494||Date: (C)2012-05-14 (M)2020-01-25|
|Type: weakness||Status: DRAFT|
|Abstraction Type: Base|
The product downloads source code or an executable from a
remote location and executes the code without sufficiently verifying the origin
and integrity of the code.
Extended DescriptionAn attacker can execute malicious code by compromising the host server,
performing DNS spoofing, or modifying the code in transit.
Likelihood of Exploit: Medium
Applicable PlatformsLanguage Class: Language-independent
Time Of Introduction
- Architecture and Design
Related Attack Patterns
|IntegrityAvailabilityConfidentialityOther ||Execute unauthorized code or
logicOther ||Executing untrusted code could compromise the control flow of the
program. The untrusted code could execute attacker-controlled commands,
read or modify sensitive resources, or prevent the software from
functioning correctly for legitimate users. |
|Manual Analysis ||This weakness can be detected using 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.Specifically, manual static analysis is typically required to find the
behavior that triggers the download of code, and to determine whether
integrity-checking methods are in use. || || |
|Black Box ||Use monitoring tools that examine the software's process as it
interacts with the operating system and the network. This technique is
useful in cases when source code is unavailable, if the software was not
developed by you, or if you want to verify that the build phase did not
introduce any new weaknesses. Examples include debuggers that directly
attach to the running process; system-call tracing utilities such as
truss (Solaris) and strace (Linux); system activity monitors such as
FileMon, RegMon, Process Monitor, and other Sysinternals utilities
(Windows); and sniffers and protocol analyzers that monitor network
traffic.Attach the monitor to the process and also sniff the network
connection. Trigger features related to product updates or plugin
installation, which is likely to force a code download. Monitor when
files are downloaded and separately executed, or if they are otherwise
read back into the process. Look for evidence of cryptographic library
calls that use integrity checking. || || |
|Implementation || ||Perform proper forward and reverse DNS lookups to detect DNS spoofing. || ||This is only a partial solution since it will not prevent your code
from being modified on the hosting site or in transit. |
|Architecture and DesignOperation || ||Encrypt the code with a reliable encryption scheme before
transmitting.This will only be a partial solution, since it will not detect DNS
spoofing and it will not prevent your code from being modified on the
hosting site. || || |
|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.Speficially, it may be helpful to use tools or frameworks to perform
integrity checking on the transmitted code. || || |
|Architecture and DesignOperation ||Environment Hardening ||Run your code using the lowest privileges that are required to
accomplish the necessary tasks [R.494.7]. 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. || || |
|Architecture and DesignOperation ||Sandbox or Jail ||Run the code in a "jail" or similar sandbox environment that enforces
strict boundaries between the process and the operating system. This may
effectively restrict which files can be accessed in a particular
directory or which commands can be executed by the software.OS-level examples include the Unix chroot jail, AppArmor, and SELinux.
In general, managed code may provide some protection. For example,
java.io.FilePermission in the Java SecurityManager allows the software
to specify restrictions on file operations.This may not be a feasible solution, and it only limits the impact to
the operating system; the rest of the application may still be subject
to compromise.Be careful to avoid CWE-243 and other weaknesses related to jails. ||Limited ||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. |
|CWE-494 ChildOf CWE-896 ||Category ||CWE-888 || |
Demonstrative Examples (Details)
- This code includes an external script to get database credentials,
then authenticates a user against the database, allowing access to the
- This example loads an external class from a local
- CVE-2008-3438 : OS does not verify authenticity of its own updates.
- CVE-2008-3324 : online poker client does not verify authenticity of its own updates.
- CVE-2001-1125 : anti-virus product does not verify automatic updates for itself.
- CVE-2002-0671 : VOIP phone downloads applications from web sites without verifying integrity.
For more examples, refer to CVE relations in the bottom box.
White Box Definitions None
Black Box Definitions None
|CLASP || ||Invoking untrusted mobile code || |
|CERT Java Secure Coding ||SEC06-J ||Do not rely on the default automatic signature verification
provided by URLClassLoader and java.util.jar || |
- Microsoft .Introduction to Code Signing.
- Microsoft .Authenticode.
- Apple .Code Signing Guide. Apple Developer Connection. 2008-11-19.
- Anthony Bellissimo John Burgess Kevin Fu .Secure Software Updates: Disappointments and New
- Michael Howard David LeBlanc John Viega .24 Deadly Sins of Software Security. McGraw-Hill. Section:'"Sin 18: The Sins of Mobile Code." Page
267'. Published on 2010.
- Johannes Ullrich .Top 25 Series - Rank 20 - Download of Code Without Integrity
Check. SANS Software Security Institute. 2010-04-05.
- Sean Barnum Michael Gegick .Least Privilege. Published on 2005-09-14.