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C++: Block flow through all bitwise 'and' and 'or' operations. This seems to be a common source of false positives on LGTM.

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This commit is contained in:
Mathias Vorreiter Pedersen
2021-06-24 15:44:14 +02:00
parent e8bba78825
commit 5bfb78b583
3 changed files with 11 additions and 17 deletions
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10
cpp/ql/src/Security/CWE/CWE-190/ArithmeticUncontrolled.ql
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@@ -97,7 +97,15 @@ class UncontrolledArithConfiguration extends TaintTracking::Configuration {
override predicate isSink(DataFlow::Node sink) { missingGuard(sink.asExpr(), _) }
override predicate isSanitizer(DataFlow::Node barrier) { bounded(barrier.asExpr()) }
override predicate isSanitizer(DataFlow::Node node) {
bounded(node.asExpr())
or
// If this expression is part of bitwise 'and' or 'or' operation it's likely that the value is
// only used as a bit pattern.
node.asExpr() =
any(BinaryBitwiseOperation op | op instanceof BitwiseOrExpr or op instanceof BitwiseAndExpr)
.getAnOperand*()
}
}
Expr getExpr(DataFlow::Node node) { result = [node.asExpr(), node.asDefiningArgument()] }

14
cpp/ql/test/query-tests/Security/CWE/CWE-190/semmle/uncontrolled/ArithmeticUncontrolled.expected
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@@ -2,10 +2,6 @@ edges
| test.c:18:13:18:16 | call to rand | test.c:21:17:21:17 | r |
| test.c:34:13:34:18 | call to rand | test.c:35:5:35:5 | r |
| test.c:44:13:44:16 | call to rand | test.c:45:5:45:5 | r |
| test.c:75:13:75:19 | call to rand | test.c:77:9:77:9 | r |
| test.c:75:13:75:19 | call to rand | test.c:77:9:77:9 | r |
| test.c:81:14:81:17 | call to rand | test.c:83:9:83:9 | r |
| test.c:81:23:81:26 | call to rand | test.c:83:9:83:9 | r |
| test.c:99:14:99:19 | call to rand | test.c:100:5:100:5 | r |
| test.cpp:8:9:8:12 | Store | test.cpp:24:11:24:18 | call to get_rand |
| test.cpp:8:9:8:12 | call to rand | test.cpp:8:9:8:12 | Store |
@@ -25,12 +21,6 @@ nodes
| test.c:35:5:35:5 | r | semmle.label | r |
| test.c:44:13:44:16 | call to rand | semmle.label | call to rand |
| test.c:45:5:45:5 | r | semmle.label | r |
| test.c:75:13:75:19 | call to rand | semmle.label | call to rand |
| test.c:75:13:75:19 | call to rand | semmle.label | call to rand |
| test.c:77:9:77:9 | r | semmle.label | r |
| test.c:81:14:81:17 | call to rand | semmle.label | call to rand |
| test.c:81:23:81:26 | call to rand | semmle.label | call to rand |
| test.c:83:9:83:9 | r | semmle.label | r |
| test.c:99:14:99:19 | call to rand | semmle.label | call to rand |
| test.c:100:5:100:5 | r | semmle.label | r |
| test.cpp:8:9:8:12 | Store | semmle.label | Store |
@@ -51,10 +41,6 @@ nodes
| test.c:21:17:21:17 | r | test.c:18:13:18:16 | call to rand | test.c:21:17:21:17 | r | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test.c:18:13:18:16 | call to rand | Uncontrolled value |
| test.c:35:5:35:5 | r | test.c:34:13:34:18 | call to rand | test.c:35:5:35:5 | r | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test.c:34:13:34:18 | call to rand | Uncontrolled value |
| test.c:45:5:45:5 | r | test.c:44:13:44:16 | call to rand | test.c:45:5:45:5 | r | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test.c:44:13:44:16 | call to rand | Uncontrolled value |
| test.c:77:9:77:9 | r | test.c:75:13:75:19 | call to rand | test.c:77:9:77:9 | r | $@ flows to here and is used in arithmetic, potentially causing an underflow. | test.c:75:13:75:19 | call to rand | Uncontrolled value |
| test.c:77:9:77:9 | r | test.c:75:13:75:19 | call to rand | test.c:77:9:77:9 | r | $@ flows to here and is used in arithmetic, potentially causing an underflow. | test.c:75:13:75:19 | call to rand | Uncontrolled value |
| test.c:83:9:83:9 | r | test.c:81:14:81:17 | call to rand | test.c:83:9:83:9 | r | $@ flows to here and is used in arithmetic, potentially causing an underflow. | test.c:81:14:81:17 | call to rand | Uncontrolled value |
| test.c:83:9:83:9 | r | test.c:81:23:81:26 | call to rand | test.c:83:9:83:9 | r | $@ flows to here and is used in arithmetic, potentially causing an underflow. | test.c:81:23:81:26 | call to rand | Uncontrolled value |
| test.c:100:5:100:5 | r | test.c:99:14:99:19 | call to rand | test.c:100:5:100:5 | r | $@ flows to here and is used in arithmetic, potentially causing an underflow. | test.c:99:14:99:19 | call to rand | Uncontrolled value |
| test.cpp:25:7:25:7 | r | test.cpp:8:9:8:12 | call to rand | test.cpp:25:7:25:7 | r | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test.cpp:8:9:8:12 | call to rand | Uncontrolled value |
| test.cpp:31:7:31:7 | r | test.cpp:13:10:13:13 | call to rand | test.cpp:31:7:31:7 | r | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test.cpp:13:10:13:13 | call to rand | Uncontrolled value |

4
cpp/ql/test/query-tests/Security/CWE/CWE-190/semmle/uncontrolled/test.c
View File

@@ -74,13 +74,13 @@ void randomTester() {
{
int r = RAND2();
r = r - 100; // BAD
r = r - 100; // BAD [NOT DETECTED]
}
{
int r = (rand() ^ rand());
r = r - 100; // BAD
r = r - 100; // BAD [NOT DETECTED]
}
{