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C++: Block flow out of sinks that are qualifiers. This removes the new result duplication and keeps the new result.

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This commit is contained in:
Mathias Vorreiter Pedersen
2023-11-14 09:29:47 +00:00
parent c73e6f1fa8
commit 967bbbc1a7
2 changed files with 11 additions and 27 deletions
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32
cpp/ql/src/Security/CWE/CWE-120/UnboundedWrite.ql
View File

@@ -52,35 +52,25 @@ predicate isUnboundedWrite(BufferWrite bw) {
* Holds if `e` is a source buffer going into an unbounded write `bw` or a
* qualifier of (a qualifier of ...) such a source.
*/
predicate unboundedWriteSource(Expr e, BufferWrite bw) {
isUnboundedWrite(bw) and e = bw.getASource()
predicate unboundedWriteSource(Expr e, BufferWrite bw, boolean qualifier) {
isUnboundedWrite(bw) and e = bw.getASource() and qualifier = false
or
exists(FieldAccess fa | unboundedWriteSource(fa, bw) and e = fa.getQualifier())
exists(FieldAccess fa | unboundedWriteSource(fa, bw, _) and e = fa.getQualifier()) and
qualifier = true
}
predicate isSource(FS::FlowSource source, string sourceType) { source.getSourceType() = sourceType }
/**
* Holds if `bw` is a `BufferWrite` that reads from `stdin`. In such cases the
* sink is the outgoing argument that is written to.
*
* By factoring these cases out into this predicate we can place an out barrier
* on exactly these sinks in `Config`.
*/
predicate isSinkFromStdIn(DataFlow::Node sink, BufferWrite bw) {
predicate isSink(DataFlow::Node sink, BufferWrite bw, boolean qualifier) {
unboundedWriteSource(sink.asIndirectExpr(), bw, qualifier)
or
// `gets` and `scanf` reads from stdin so there's no real input.
// The `BufferWrite` library models this as the call itself being
// the source. In this case we mark the output argument as being
// the sink so that we report a path where source = sink (because
// the same output argument is also included in `isSource`).
bw.getASource() = bw and
unboundedWriteSource(sink.asDefiningArgument(), bw)
}
predicate isSink(DataFlow::Node sink, BufferWrite bw) {
unboundedWriteSource(sink.asIndirectExpr(), bw)
or
isSinkFromStdIn(sink, bw)
unboundedWriteSource(sink.asDefiningArgument(), bw, qualifier)
}
predicate lessThanOrEqual(IRGuardCondition g, Expr e, boolean branch) {
@@ -95,9 +85,9 @@ predicate lessThanOrEqual(IRGuardCondition g, Expr e, boolean branch) {
module Config implements DataFlow::ConfigSig {
predicate isSource(DataFlow::Node source) { isSource(source, _) }
predicate isSink(DataFlow::Node sink) { isSink(sink, _) }
predicate isSink(DataFlow::Node sink) { isSink(sink, _, _) }
predicate isBarrierOut(DataFlow::Node node) { isSinkFromStdIn(node, _) }
predicate isBarrierOut(DataFlow::Node node) { isSink(node, _, false) }
predicate isBarrier(DataFlow::Node node) {
// Block flow if the node is guarded by any <, <= or = operations.
@@ -127,7 +117,7 @@ from BufferWrite bw, Flow::PathNode source, Flow::PathNode sink, string sourceTy
where
Flow::flowPath(source, sink) and
isSource(source.getNode(), sourceType) and
isSink(sink.getNode(), bw)
isSink(sink.getNode(), bw, _)
select bw, source, sink,
"This '" + bw.getBWDesc() + "' with input from $@ may overflow the destination.",
source.getNode(), sourceType

6
cpp/ql/test/query-tests/Security/CWE/CWE-120/semmle/tests/UnboundedWrite.expected
View File

@@ -1,24 +1,18 @@
edges
| tests.c:16:26:16:29 | argv indirection | tests.c:28:22:28:28 | access to array indirection |
| tests.c:16:26:16:29 | argv indirection | tests.c:29:28:29:34 | access to array indirection |
| tests.c:16:26:16:29 | argv indirection | tests.c:31:15:31:23 | buffer100 indirection |
| tests.c:16:26:16:29 | argv indirection | tests.c:33:21:33:29 | buffer100 indirection |
| tests.c:16:26:16:29 | argv indirection | tests.c:34:10:34:16 | access to array indirection |
nodes
| tests.c:16:26:16:29 | argv indirection | semmle.label | argv indirection |
| tests.c:28:22:28:28 | access to array indirection | semmle.label | access to array indirection |
| tests.c:29:28:29:34 | access to array indirection | semmle.label | access to array indirection |
| tests.c:31:15:31:23 | buffer100 indirection | semmle.label | buffer100 indirection |
| tests.c:31:15:31:23 | scanf output argument | semmle.label | scanf output argument |
| tests.c:33:21:33:29 | buffer100 indirection | semmle.label | buffer100 indirection |
| tests.c:33:21:33:29 | scanf output argument | semmle.label | scanf output argument |
| tests.c:34:10:34:16 | access to array indirection | semmle.label | access to array indirection |
subpaths
#select
| tests.c:28:3:28:9 | call to sprintf | tests.c:16:26:16:29 | argv indirection | tests.c:28:22:28:28 | access to array indirection | This 'call to sprintf' with input from $@ may overflow the destination. | tests.c:16:26:16:29 | argv indirection | a command-line argument |
| tests.c:29:3:29:9 | call to sprintf | tests.c:16:26:16:29 | argv indirection | tests.c:29:28:29:34 | access to array indirection | This 'call to sprintf' with input from $@ may overflow the destination. | tests.c:16:26:16:29 | argv indirection | a command-line argument |
| tests.c:31:15:31:23 | buffer100 | tests.c:16:26:16:29 | argv indirection | tests.c:31:15:31:23 | buffer100 indirection | This 'scanf string argument' with input from $@ may overflow the destination. | tests.c:16:26:16:29 | argv indirection | a command-line argument |
| tests.c:31:15:31:23 | buffer100 | tests.c:31:15:31:23 | scanf output argument | tests.c:31:15:31:23 | scanf output argument | This 'scanf string argument' with input from $@ may overflow the destination. | tests.c:31:15:31:23 | scanf output argument | value read by scanf |
| tests.c:33:21:33:29 | buffer100 | tests.c:16:26:16:29 | argv indirection | tests.c:33:21:33:29 | buffer100 indirection | This 'scanf string argument' with input from $@ may overflow the destination. | tests.c:16:26:16:29 | argv indirection | a command-line argument |
| tests.c:33:21:33:29 | buffer100 | tests.c:33:21:33:29 | scanf output argument | tests.c:33:21:33:29 | scanf output argument | This 'scanf string argument' with input from $@ may overflow the destination. | tests.c:33:21:33:29 | scanf output argument | value read by scanf |
| tests.c:34:25:34:33 | buffer100 | tests.c:16:26:16:29 | argv indirection | tests.c:34:10:34:16 | access to array indirection | This 'sscanf string argument' with input from $@ may overflow the destination. | tests.c:16:26:16:29 | argv indirection | a command-line argument |