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Account for the signedness of the lesser operand

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This commit is contained in:
Remco Vermeulen
2023-06-19 16:57:36 -07:00
parent 9c774ac97f
commit 32d7faa3b8
3 changed files with 32 additions and 2 deletions
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11
cpp/ql/src/Security/CWE/CWE-190/ComparisonWithWiderType.ql
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@@ -45,13 +45,22 @@ Element friendlyLoc(Expr e) {
not e instanceof Access and not e instanceof Call and result = e
}
int getComparisonSizeAdjustment(Expr e) {
if e.getType().(IntegralType).isSigned()
then result = 1
else result = 0
}
from Loop l, RelationalOperation rel, VariableAccess small, Expr large
where
small = rel.getLesserOperand() and
large = rel.getGreaterOperand() and
rel = l.getCondition().getAChild*() and
forall(Expr conv | conv = large.getConversion*() |
upperBound(conv).log2() > getComparisonSize(small) * 8
// We adjust the comparison size in the case of a signed integer type.
// This is to exclude the sign bit from the comparison that determines if the small type's size is sufficient to hold
// the value of the larger type determined with range analysis.
upperBound(conv).log2() > (getComparisonSize(small) * 8 - getComparisonSizeAdjustment(small))
) and
// Ignore cases where the smaller type is int or larger
// These are still bugs, but you should need a very large string or array to

2
cpp/ql/test/query-tests/Security/CWE/CWE-190/semmle/ComparisonWithWiderType/ComparisonWithWiderType.expected
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@@ -1,6 +1,7 @@
| test.c:4:14:4:18 | ... < ... | Comparison between $@ of type char and $@ of wider type int. | test.c:3:7:3:7 | c | c | test.c:2:17:2:17 | x | x |
| test.c:9:14:9:18 | ... > ... | Comparison between $@ of type char and $@ of wider type int. | test.c:8:7:8:7 | c | c | test.c:7:17:7:17 | x | x |
| test.c:14:14:14:18 | ... < ... | Comparison between $@ of type short and $@ of wider type int. | test.c:13:8:13:8 | s | s | test.c:12:17:12:17 | x | x |
| test.c:42:15:42:29 | ... < ... | Comparison between $@ of type short and $@ of wider type int. | test.c:41:9:41:10 | s1 | s1 | test.c:42:20:42:29 | 65535 | 65535 |
| test.c:65:14:65:18 | ... < ... | Comparison between $@ of type short and $@ of wider type int. | test.c:64:8:64:8 | s | s | test.c:63:17:63:17 | x | x |
| test.c:87:14:87:18 | ... < ... | Comparison between $@ of type unsigned char and $@ of wider type unsigned int. | test.c:83:16:83:16 | c | c | test.c:84:15:84:15 | x | x |
| test.c:91:14:91:23 | ... < ... | Comparison between $@ of type unsigned char and $@ of wider type int. | test.c:83:16:83:16 | c | c | test.c:91:18:91:23 | 65280 | 65280 |
@@ -13,3 +14,4 @@
| test.c:107:14:107:26 | ... < ... | Comparison between $@ of type unsigned char and $@ of wider type unsigned int. | test.c:83:16:83:16 | c | c | test.c:107:19:107:25 | ... >> ... | ... >> ... |
| test.c:128:15:128:21 | ... < ... | Comparison between $@ of type unsigned char and $@ of wider type unsigned int. | test.c:121:16:121:17 | uc | uc | test.c:123:19:123:20 | sz | sz |
| test.c:139:15:139:21 | ... < ... | Comparison between $@ of type unsigned char and $@ of wider type unsigned int. | test.c:121:16:121:17 | uc | uc | test.c:123:19:123:20 | sz | sz |
| test.c:156:9:156:14 | ... < ... | Comparison between $@ of type short and $@ of wider type int. | test.c:150:8:150:8 | s | s | test.c:151:6:151:7 | sx | sx |

21
cpp/ql/test/query-tests/Security/CWE/CWE-190/semmle/ComparisonWithWiderType/test.c
View File

@@ -39,7 +39,7 @@ void test5 () {
void test6() {
short s1;
for (s1 = 0; s1 < 0x0000ffff; s1++) {}
for (s1 = 0; s1 < 0x0000ffff; s1++) {} // BAD
}
void test7(long long l) {
@@ -145,3 +145,22 @@ void test13() {
sz = (unsigned)sx & (unsigned)sy;
for (uc = 0; uc < sz; uc++) {} // GOOD
}
void test14() {
short s = 0;
int sx = 0x7FFF + 1;
// BAD: 's' is compared with a value of a wider type.
// 's' overflows before reaching 'sx',
// causing an infinite loop
while (s < sx) {
s += 1;
}
unsigned int ux = 0;
// GOOD: 'ux' has a type at least as wide as 'max_get'
while (ux < sx) {
ux += 1;
}
}