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Software vulnerabilities can result when a programmer fails to consider all possible data states.

Noncompliant Code Example (

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if Chain)

This noncompliant code example fails to test for conditions in which a is neither b nor c. This may be the correct behavior in this case, but failure to account for all the values of a can result in logic errors if a unexpectedly assumes a different value.

if (a == b) {
  /* ... */
}
else if (a == c) {
  /* ... */
}

Compliant Solution (

...

if Chain)

This compliant solution explicitly checks for the unexpected condition and handles it appropriately:

if (a == b) {
  /* ... */
}
else if (a == c) {
  /* ... */
}
else {
  /* Handle error condition */
}

Noncompliant Code Example (

...

switch)

Even though x is supposed to represent a bit (0 or 1) in the following this noncompliant code example, some previous error may have allowed x to assume a different value. Detecting and dealing with that inconsistent state now sooner rather than later will make makes the error easier to find and may prevent security violations.

switch(x) {
  case 0: foo(); break;
  case 1: bar(); break;
}

Compliant Solution (

...

switch)

This compliant solution provides the default label to handle all valid possible values of type int:

switch(x) {
  case 0: foo(); break;
  case 1: bar(); break;
  default: /* Handle error */ break;
} 

...

final static int ORIGIN_YEAR = 1980;
public void zune_nce1(long days){  /* Number of days since January 1, 1980 */
public void convertDays(long days){  
	int year = ORIGIN_YEAR;
    /* ... */
    while (days > 365) {
    	if (IsLeapYear(year)) {
        	if (days > 366) {
            	days -= 366;
              	year += 1;
            }
        } else {
            days -= 365;
            year += 1;
        }
    }
}

The original ConvertDays method () function in the real-time clock (RTC) routines for the MC13783 PMIC RTC takes the number of days since January 1, 1980, and computes the correct year and number of days since January 1 of the correct year.

...

final static int ORIGIN_YEAR = 1980;
public void zune_cs1(long days){   /* Number of days since January 1, 1980 */
public void convertDays(long days){    
	int year = ORIGIN_YEAR;
    /* ... */
    int daysThisYear = (IsLeapYear(year) ? 366 : 365);
    while (days > daysThisYear) {
    	days -= daysThisYear;
        year += 1;
        daysThisYear = (IsLeapYear(year) ? 366 : 365);
    }
}

This compliant solution is for illustrative purposes and is not necessarily may differ from the solution implemented by Microsoft.

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