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

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

These functionfunctions truncate strings that exceed the specified limits. Additionally, some functions such as {{strncpy()}} do not guarantee that the resulting string is null-terminated \[[STR33-C|STR33-C. Guarantee that all strings are null-terminated]\].

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

Non-Compliant Code Example

The standard function functions strncpy() and strncat() copy a specified number n characters from a source string to a destination array. If there is no null character in the first n characters of the source array, the result is will not be null-terminated and any remaining charactes are truncated.

char *string_data;
char a[16];
...
strncpy(a, string_data, sizeof(a));

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The {{strcpy_s()}} function provides additional safeguards, including accepting the size of the destination buffer as an additional argument \[[STR00-A|STR00-A. Use TR 24731 for remediation of existing string manipulation code]\].

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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 made clear statement clearly stated in comments.

Priority: P2 Level: L3

Truncating strings can lead to a loss of data and exploitable vulnerabilities , in some cases, exploitable vulnerabilities.

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