C++: Add tests for bounded hex format values

Author: rdmarsh2

cpp/ql/test/query-tests/Security/CWE/CWE-120/semmle/tests/OverrunWrite.expected

@@ -14,6 +14,13 @@
 | tests.c:120:3:120:9 | call to sprintf | This 'call to sprintf' operation requires 17 bytes but the destination is only 1 bytes. |
 | tests.c:121:3:121:9 | call to sprintf | This 'call to sprintf' operation requires 17 bytes but the destination is only 16 bytes. |
 | tests.c:136:2:136:8 | call to sprintf | This 'call to sprintf' operation requires 11 bytes but the destination is only 10 bytes. |
+| tests.c:178:2:178:8 | call to sprintf | This 'call to sprintf' operation requires 9 bytes but the destination is only 2 bytes. |
+| tests.c:179:2:179:8 | call to sprintf | This 'call to sprintf' operation requires 9 bytes but the destination is only 3 bytes. |
+| tests.c:180:2:180:8 | call to sprintf | This 'call to sprintf' operation requires 9 bytes but the destination is only 5 bytes. |
+| tests.c:182:3:182:9 | call to sprintf | This 'call to sprintf' operation requires 9 bytes but the destination is only 2 bytes. |
+| tests.c:186:3:186:9 | call to sprintf | This 'call to sprintf' operation requires 9 bytes but the destination is only 2 bytes. |
+| tests.c:189:3:189:9 | call to sprintf | This 'call to sprintf' operation requires 9 bytes but the destination is only 2 bytes. |
+| tests.c:193:3:193:9 | call to sprintf | This 'call to sprintf' operation requires 9 bytes but the destination is only 5 bytes. |
 | unions.c:26:2:26:7 | call to strcpy | This 'call to strcpy' operation requires 21 bytes but the destination is only 16 bytes. |
 | unions.c:27:2:27:7 | call to strcpy | This 'call to strcpy' operation requires 21 bytes but the destination is only 15 bytes. |
 | unions.c:27:2:27:7 | call to strcpy | This 'call to strcpy' operation requires 21 bytes but the destination is only 16 bytes. |

cpp/ql/test/query-tests/Security/CWE/CWE-120/semmle/tests/tests.c

@@ -169,3 +169,27 @@ void testVarSizeStruct()
 
 	snprintf(s->data, 10, "abcdefghijklmnopqrstuvwxyz"); // GOOD
 }
+
+void tesHexBounds(int x) {
+	char buffer2[2];
+	char buffer3[3];
+	char buffer5[5];
+
+	sprintf(buffer2, "%x", 1);  // GOOD [FALSE POSITIVE]
+	sprintf(buffer3, "%x", 16); // GOOD [FALSE POSITIVE]
+	sprintf(buffer5, "%x", (unsigned short)x); // GOOD: bounded by conversion [FALSE POSITIVE]
+	if (x < 16 && x > 0) {
+		sprintf(buffer2, "%x", x); // GOOD: bounded by check [FALSE POSITIVE]
+	}
+
+	if (x < 16) {
+		sprintf(buffer2, "%x", x); // BAD:  negative values
+	}
+	if (x <= 16 && x > 0) {
+		sprintf(buffer2, "%x", x); // BAD: bound too loose
+	}
+
+	if(x < 0x10000 && x > 0) {
+		sprintf(buffer5, "%x", x); // GOOD: bounded by check [FALSE POSITIVE]
+	}
+}