Alternative functions that limit the number of bytes copied are often recommended to mitigate buffer overflow vulnerabilities. For example:
strncpy()instead ofstrcpy()strncat()instead ofstrcat()fgets()instead ofgets()snprintf()instead ofsprintf()
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.
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Exceptions
An exception to this rule applies if the intent of the programmer was to intentionally truncate the NULL-terminated byte string. To be compliant with this standard, this intent must be clearly stated in comments.
Risk Assessment
Truncating strings can lead to a loss of data.
Rule |
Severity |
Likelihood |
Remediation Cost |
Priority |
Level |
|---|---|---|---|---|---|
STR03-A |
1 (low) |
1 (unlikely) |
2 (medium) |
P2 |
L3 |
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 24731-2006]]