C++: Refactor leap year logic for UncheckedLeapYearAfterYearModification. Includes new logic for detecting leap year checks, new forms of leap year checks detected, and various heuristics to remove false postives. Move TimeConversionFunction into LeapYear.qll and refactored to separate conversion functions that are expected to be checked for failure from those that auto correct leap year dates if feb 29 is provided on a non-leap year. Increas the set of known TimeConversionFunctions.

Author: bdrodes

cpp/ql/src/Likely Bugs/Leap Year/LeapYear.qll

@@ -308,3 +308,35 @@ private module PossibleYearArithmeticOperationCheckConfig implements DataFlow::C
 
 module PossibleYearArithmeticOperationCheckFlow =
   TaintTracking::Global<PossibleYearArithmeticOperationCheckConfig>;
+
+/**
+ * This list of APIs should check for the return value to detect problems during the conversion.
+ */
+class TimeConversionFunction extends Function {
+  boolean autoLeapYearCorrecting;
+
+  TimeConversionFunction() {
+    autoLeapYearCorrecting = false and
+    (
+      this.getName() =
+        [
+          "FileTimeToSystemTime", "SystemTimeToFileTime", "SystemTimeToTzSpecificLocalTime",
+          "SystemTimeToTzSpecificLocalTimeEx", "TzSpecificLocalTimeToSystemTime",
+          "TzSpecificLocalTimeToSystemTimeEx", "RtlLocalTimeToSystemTime",
+          "RtlTimeToSecondsSince1970", "_mkgmtime", "SetSystemTime", "VarUdateFromDate", "from_tm"
+        ]
+      or
+      // Matches all forms of GetDateFormat, e.g. GetDateFormatA/W/Ex
+      this.getName().matches("GetDateFormat%")
+    )
+    or
+    autoLeapYearCorrecting = true and
+    this.getName() =
+      ["mktime", "_mktime32", "_mktime64", "SystemTimeToVariantTime", "VariantTimeToSystemTime"]
+  }
+
+  /**
+   * Holds if the function is expected to auto convert a bad leap year date.
+   */
+  predicate isAutoLeapYearCorrecting() { autoLeapYearCorrecting = true }
+}