String data passed to complex subsystems may contain special characters that can trigger commands or actions, resulting in a software vulnerability. As a result it is necessary to sanatize sanitize all string data passed to complex subsystems including, but not limited to:
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It is necessary to ensure that all valid data is accepted while potentially dangerous data is rejected or sanitized. This can be difficult when vald valid characters or sequences of characters also have special meanining meaning to the subsystem and may involve validating the data against a grammer. In cases where there is no overlap, white listing can be used to eliminate dangerous characters from the data.
The white listing approach to data sanatization sanitization is to define a list of acceptable characters and remove any character that is not acceptable. The list of valid input values is typically a predictable, well-defined set of manageable size. The following example, based on the tcp_wrappers package written by Wietse Venema, illustrates white listing approach:
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The benefit of white listing is that a programmer can be certain that a string contains only characters that are considered safe by the programmer. White listing is recommended over black listing because , instead of having to trap which traps all unacceptable characters , as the programmer only needs to ensure that acceptable characters are identified. As a result, the programmer can be less concerned about which characters an attacker may try in an attempt to bypass security checks.
Priority: P12 Level: L1
Failure to sanatize sanitize data passed to a complex subsystem can lead to an injection attack, data integrity issues, and a loss of sensitive data.
Component | Value |
|---|---|
Severity | 2 (medium) |
Likelihood | 3 (likely) |
Remediation cost | 2 (medium) |
References
- Viega 03 Viega, John and Messier, Matt. Secure Programming Cookbook for C and C++: Recipes for Cryptography, Authentication, Networking, Input Validation & More. Sebastopol, CA: O'Reilly, 2003 (ISBN: 0-596-00394-3).
- ISO/IEC 9899-1999 Section 7.20.4.6 The system function