SEI CERT C Coding Standard

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Alternative functions that limit the number of bytes copied are often recommended to mitigate buffer overflow vulnerabilities. For example:

  • strncpy() instead of strcpy()
  • strncat() instead of strcat()
  • fgets() instead of gets()
  • snprintf() instead of sprintf()

These functions truncate strings that exceed the specified limits. Additionally, some functions such as strncpy() do not guarantee that the resulting string is null-terminated [[STR32-C. Null-terminate byte strings as required]].

Unintentional truncation results in a loss of data and, in some cases, leads to software vulnerabilities.

Unable to render {include} The included page could not be found.
Unable to render {include} The included page could not be found.
Unable to render {include} The included page could not be found.

Exceptions

STR03-EX1: The intent of the programmer is to intentionally truncate the null-terminated byte string.

Risk Assessment

Truncating strings can lead to a loss of data.

Recommendation

Severity

Likelihood

Remediation Cost

Priority

Level

STR03-A

1 (low)

1 (unlikely)

2 (medium)

P2

L3

Automated Detection

The LDRA tool suite V 7.6.0 is able to detect violations of this recommendation.

Fortify SCA Version 5.0 with CERT C Rule Pack can detect violations of this recommendation.

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

References

[[ISO/IEC 9899-1999]] Section 7.21, "String handling <string.h>"
[[Seacord 05a]] Chapter 2, "Strings"
[[ISO/IEC TR 24731-1-2007]]

STR02-A. Sanitize data passed to complex subsystems      07. Characters and Strings (STR)       STR05-A. Prefer making string literals const-qualified

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