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C++: Relax the restrictions on when '%' is a barrier and accept test changes.

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Mathias Vorreiter Pedersen
2021-06-25 15:15:26 +02:00
parent a6f1f8d3b6
commit 4fc60aedc6
3 changed files with 8 additions and 31 deletions
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25
cpp/ql/src/Security/CWE/CWE-190/Bounded.qll
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@@ -15,16 +15,11 @@ pragma[inline]
private predicate boundedDiv(Expr e, Expr left) { e = left }
/**
* An operand `e` of a remainder expression `rem` (i.e., `rem` is either a `RemExpr` or
* an `AssignRemExpr`) with left-hand side `left` and right-ahnd side `right` is bounded
* when `e` is `left` and `right` is upper bounded by some number that is less than the maximum integer
* allowed by the result type of `rem`.
* An operand `e` of a remainder expression (i.e., `e` is an operand of either a `RemExpr` or
* a `AssignRemExpr`) is bounded when `e` is the left-hand side of the remainder.
*/
pragma[inline]
private predicate boundedRem(Expr e, Expr rem, Expr left, Expr right) {
e = left and
upperBound(right.getFullyConverted()) < exprMaxVal(rem.getFullyConverted())
}
private predicate boundedRem(Expr e, Expr left) { e = left }
/**
* An operand `e` of a bitwise and expression `andExpr` (i.e., `andExpr` is either an `BitwiseAndExpr`
@@ -50,19 +45,9 @@ predicate bounded(Expr e) {
) and
not convertedExprMightOverflow(e)
or
// For `%` and `&` we require that `e` is bounded by a value that is strictly smaller than the
// maximum possible value of the result type of the operation.
// For example, the function call `rand()` is considered bounded in the following program:
// ```
// int i = rand() % (UINT8_MAX + 1);
// ```
// but not in:
// ```
// unsigned char uc = rand() % (UINT8_MAX + 1);
// ```
exists(RemExpr rem | boundedRem(e, rem, rem.getLeftOperand(), rem.getRightOperand()))
boundedRem(e, any(RemExpr rem).getLeftOperand())
or
exists(AssignRemExpr rem | boundedRem(e, rem, rem.getLValue(), rem.getRValue()))
boundedRem(e, any(AssignRemExpr rem).getLValue())
or
exists(BitwiseAndExpr andExpr |
boundedBitwiseAnd(e, andExpr, andExpr.getAnOperand(), andExpr.getAnOperand())

8
cpp/ql/test/query-tests/Security/CWE/CWE-190/semmle/uncontrolled/ArithmeticUncontrolled.expected
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@@ -7,8 +7,6 @@ edges
| 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.c:115:12:115:15 | call to rand | test.c:116:3:116:4 | r1 |
| test.c:118:13:118:16 | call to rand | test.c:119:3:119:4 | r2 |
| 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 |
| test.cpp:13:2:13:15 | Chi [[]] | test.cpp:30:13:30:14 | get_rand2 output argument [[]] |
@@ -35,10 +33,6 @@ nodes
| 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.c:115:12:115:15 | call to rand | semmle.label | call to rand |
| test.c:116:3:116:4 | r1 | semmle.label | r1 |
| test.c:118:13:118:16 | call to rand | semmle.label | call to rand |
| test.c:119:3:119:4 | r2 | semmle.label | r2 |
| test.cpp:8:9:8:12 | Store | semmle.label | Store |
| test.cpp:8:9:8:12 | call to rand | semmle.label | call to rand |
| test.cpp:13:2:13:15 | Chi [[]] | semmle.label | Chi [[]] |
@@ -62,8 +56,6 @@ nodes
| 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.c:116:3:116:4 | r1 | test.c:115:12:115:15 | call to rand | test.c:116:3:116:4 | r1 | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test.c:115:12:115:15 | call to rand | Uncontrolled value |
| test.c:119:3:119:4 | r2 | test.c:118:13:118:16 | call to rand | test.c:119:3:119:4 | r2 | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test.c:118:13:118:16 | 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 |
| test.cpp:37:7:37:7 | r | test.cpp:18:9:18:12 | call to rand | test.cpp:37:7:37:7 | r | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test.cpp:18:9:18:12 | call to rand | Uncontrolled value |

6
cpp/ql/test/query-tests/Security/CWE/CWE-190/semmle/uncontrolled/test.c
View File

@@ -113,9 +113,9 @@ void add_100(int r) {
void randomTester2(int bound, int min, int max) {
int r1 = rand() % bound;
r1 += 100; // GOOD [FALSE POSITIVE] (`bound` may possibly be MAX_INT in which case this could
// still overflow, but it's most likely fine)
r1 += 100; // GOOD (`bound` may possibly be MAX_INT in which case this could
// still overflow, but it's most likely fine)
int r2 = (rand() % (max - min + 1)) + min;
r2 += 100; // GOOD [FALSE POSITIVE] (This is a common way to clamp the random value between [min, max])
r2 += 100; // GOOD (This is a common way to clamp the random value between [min, max])
}