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C++: Use range analysis in Overflow.qll

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This commit is contained in:
Mathias Vorreiter Pedersen
2021-04-13 16:15:37 +02:00
parent 2d618d6b92
commit d1457995dd
4 changed files with 7 additions and 9 deletions
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7
cpp/ql/src/semmle/code/cpp/security/Overflow.qll
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@@ -5,6 +5,7 @@
import cpp
import semmle.code.cpp.controlflow.Dominance
import semmle.code.cpp.rangeanalysis.SimpleRangeAnalysis
/**
* Holds if the value of `use` is guarded using `abs`.
@@ -94,9 +95,10 @@ predicate guardedGreater(Operation e, Expr use) {
VariableAccess varUse(LocalScopeVariable v) { result = v.getAnAccess() }
/**
* Holds if `e` is not guarded against overflow by `use`.
* Holds if `e` potentially overflows and `use` is an operand of `e` that is not guarded.
*/
predicate missingGuardAgainstOverflow(Operation e, VariableAccess use) {
convertedExprMightOverflow(e) and
use = e.getAnOperand() and
exists(LocalScopeVariable v | use.getTarget() = v |
// overflow possible if large
@@ -115,9 +117,10 @@ predicate missingGuardAgainstOverflow(Operation e, VariableAccess use) {
}
/**
* Holds if `e` is not guarded against underflow by `use`.
* Holds if `e` potentially underflows and `use` is an operand of `e` that is not guarded.
*/
predicate missingGuardAgainstUnderflow(Operation e, VariableAccess use) {
convertedExprMightOverflowNegatively(e) and
use = e.getAnOperand() and
exists(LocalScopeVariable v | use.getTarget() = v |
// underflow possible if use is left operand and small

2
cpp/ql/test/query-tests/Security/CWE/CWE-190/semmle/extreme/ArithmeticWithExtremeValues.expected
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@@ -3,6 +3,4 @@
| test.c:50:3:50:5 | sc3 | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test.c:49:9:49:16 | 127 | Extreme value |
| test.c:59:3:59:5 | sc6 | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test.c:58:9:58:16 | 127 | Extreme value |
| test.c:63:3:63:5 | sc8 | $@ flows to here and is used in arithmetic, potentially causing an underflow. | test.c:62:9:62:16 | - ... | Extreme value |
| test.c:75:3:75:5 | sc1 | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test.c:74:9:74:16 | 127 | Extreme value |
| test.c:76:3:76:5 | sc1 | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test.c:74:9:74:16 | 127 | Extreme value |
| test.c:124:9:124:9 | x | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test.c:118:17:118:23 | 2147483647 | Extreme value |

4
cpp/ql/test/query-tests/Security/CWE/CWE-190/semmle/extreme/test.c
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@@ -72,8 +72,8 @@ void test_negatives() {
signed char sc1, sc2, sc3, sc4, sc5, sc6, sc7, sc8;
sc1 = CHAR_MAX;
sc1 += 0; // GOOD [FALSE POSITIVE]
sc1 += -1; // GOOD [FALSE POSITIVE]
sc1 += 0; // GOOD
sc1 += -1; // GOOD
sc2 = CHAR_MIN;
sc2 += -1; // BAD [NOT DETECTED]
sc3 = CHAR_MIN;

3
cpp/ql/test/query-tests/Security/CWE/CWE-190/semmle/tainted/ArithmeticTainted.expected
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@@ -1,8 +1,5 @@
| test2.cpp:14:11:14:11 | v | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test2.cpp:25:22:25:23 | & ... | User-provided value |
| test2.cpp:14:11:14:11 | v | $@ flows to here and is used in arithmetic, potentially causing an underflow. | test2.cpp:25:22:25:23 | & ... | User-provided value |
| test3.c:15:10:15:10 | x | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test3.c:11:15:11:18 | argv | User-provided value |
| test3.c:15:14:15:14 | y | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test3.c:11:15:11:18 | argv | User-provided value |
| test3.c:15:18:15:18 | z | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test3.c:11:15:11:18 | argv | User-provided value |
| test5.cpp:17:6:17:18 | call to getTaintedInt | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test5.cpp:9:7:9:9 | buf | User-provided value |
| test5.cpp:19:6:19:6 | y | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test5.cpp:9:7:9:9 | buf | User-provided value |
| test5.cpp:19:6:19:6 | y | $@ flows to here and is used in arithmetic, potentially causing an underflow. | test5.cpp:9:7:9:9 | buf | User-provided value |