The code on the right is designed to manage typecasting safely. As a result, when the same value is printed twice – interpreted once as signed and once as unsigned – two different results are produced. In the vulnerable code on the left, these variables are unsafely cast to the opposite signedness. In contrast, a value of -5 can be stored in a signed int but not an unsigned one. The value of a in the main function can be safely stored in an unsigned int but not in a signed one. The code samples shown above demonstrate safe and unsafe casts between signed and unsigned integers. For this reason, it is vital to ensure that a value can be correctly interpreted within a target variable type before casting it over to that type. Since unsigned ints can hold larger values than signed ones, it is possible that more data is copied than space is allocated for (even if the bits used in both values are identical).ĭifferent interpretations of values occur when a variable is typecast from one type to another (either explicitly or implicitly). For example, a variable may be used as a signed int for memory allocation and an unsigned int when copying over data to the newly-allocated memory block. This typically becomes a major issue when a variable is interpreted one way in one location and another way in a different location. As a result, a variable may be interpreted as larger or smaller than it originally was. Integer overflow and underflow vulnerabilities occur when an application tries to place a value into a variable where it doesn’t fit. Mitigating Integer Overflow and Underflow Vulnerabilities
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