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char src1[100] = "hello";
char src2[8] =  {'g','o','o','d','b','y','e','\0'};
char dst1[6],;
char dst2[5];
int r1,;
int r2;

r1 = strcpy_s(dst1, sizeof(dst1), src1);
r2 = strcpy_s(dst2, sizeof(dst2), src2);

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Users of the C11 Annex K functions are less likely to introduce a security flaw because the size of the destination buffer and the maximum number of characters to append must be specified. ISO/IEC TR 24731 Part II [ISO/IEC TR 24731-2:2010] offers another approach, supplying functions that allocate enough memory for their results. ISO/IEC TR 24731 Part II functions also ensure null termination of the destination string.

ISO/IEC TR 24731-1 [ISO/IEC TR 24731-1:2007] C11 Annex K functions are still capable of overflowing a buffer if the maximum length of the destination buffer and number of characters to copy are incorrectly specified. ISO/IEC TR 24731 -2 Part II functions can make it more difficult to keep track of memory that must be freed, leading to memory leaks. As a result, the C11 Annex K and the ISO/IEC TR 24731 Part II functions are not particularly secure but may be useful in preventive maintenance to reduce the likelihood of vulnerabilities in an existing legacy code base.

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String-handling functions defined in the C Standard, Section 7.24 [ISO/IEC 9899:2011], and elsewhere are susceptible to common programming errors that can lead to serious, exploitable vulnerabilities. Proper use of TR 24731 the C11 Annex K functions can eliminate most of these issues.

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

Related Guidelines

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