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Merge pull request #14798 from owen-mc/go/improve-value-flow-through-slice-exprs
Go: model value flow with array content through slice expressions
2 parents 0668b71 + 64bf6cc commit d26dc68

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‎go/ql/lib/change-notes/2023-11-15-bug-fix-value-flow-in-slice-expression.md‎

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---
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category: fix
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---
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* A bug has been fixed that meant that value flow through a slice expression was not tracked correctly. Taint flow was tracked correctly.

‎go/ql/lib/semmle/go/dataflow/internal/ContainerFlow.qll‎

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@@ -24,6 +24,13 @@ predicate containerStoreStep(Node node1, Node node2, Content c) {
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exists(Write w | w.writesElement(node2.(PostUpdateNode).getPreUpdateNode(), _, node1))
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or
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node1 = node2.(ImplicitVarargsSlice).getCallNode().getAnImplicitVarargsArgument()
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or
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// To model data flow from array elements of the base of a `SliceNode` to
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// the `SliceNode` itself, we consider there to be a read step with array
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// content from the base to the corresponding `SliceElementNode` and then
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// a store step with array content from the `SliceelementNode` to the
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// `SliceNode` itself.
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node2 = node1.(SliceElementNode).getSliceNode()
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)
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)
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or
@@ -57,6 +64,13 @@ predicate containerReadStep(Node node1, Node node2, Content c) {
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)
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or
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node2.(RangeElementNode).getBase() = node1
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or
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// To model data flow from array elements of the base of a `SliceNode` to
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// the `SliceNode` itself, we consider there to be a read step with array
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// content from the base to the corresponding `SliceElementNode` and then
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// a store step with array content from the `SliceelementNode` to the
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// `SliceNode` itself.
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node2.(SliceElementNode).getSliceNode().getBase() = node1
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)
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or
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c instanceof CollectionContent and

‎go/ql/lib/semmle/go/dataflow/internal/DataFlowNodes.qll‎

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@@ -11,6 +11,7 @@ private newtype TNode =
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MkSsaNode(SsaDefinition ssa) or
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MkGlobalFunctionNode(Function f) or
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MkImplicitVarargsSlice(CallExpr c) { c.hasImplicitVarargs() } or
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MkSliceElementNode(SliceExpr se) or
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MkFlowSummaryNode(FlowSummaryImpl::Private::SummaryNode sn)
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/** Nodes intended for only use inside the data-flow libraries. */
@@ -998,6 +999,37 @@ module Public {
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Node getMax() { result = DataFlow::instructionNode(insn.getMax()) }
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}
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/**
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* A data-flow node which exists solely to model the value flow from array
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* elements of the base of a `SliceNode` to array elements of the `SliceNode`
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* itself.
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*/
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class SliceElementNode extends Node, MkSliceElementNode {
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IR::SliceInstruction si;
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SliceElementNode() { this = MkSliceElementNode(si.getExpr()) }
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override ControlFlow::Root getRoot() { result = this.getSliceNode().getRoot() }
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override Type getType() {
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result = si.getResultType().(ArrayType).getElementType() or
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result = si.getResultType().(SliceType).getElementType()
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}
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override string getNodeKind() { result = "slice element node" }
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override string toString() { result = "slice element node" }
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override predicate hasLocationInfo(
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string filepath, int startline, int startcolumn, int endline, int endcolumn
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) {
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si.hasLocationInfo(filepath, startline, startcolumn, endline, endcolumn)
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}
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/** Gets the `SliceNode` which this node relates to. */
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SliceNode getSliceNode() { result = DataFlow::instructionNode(si) }
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}
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/**
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* A data-flow node corresponding to an expression with a binary operator.
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*/

‎go/ql/test/library-tests/semmle/go/dataflow/ArrayConversion/main.go‎

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@@ -4,7 +4,7 @@ func source() string {
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return "untrusted data"
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}
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func sink(string) {
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func sink(any) {
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}
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func sliceToArray(p []string) [1]string {
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// Test the new slice->array conversion permitted in Go 1.20
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var a [4]string
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a[0] = source()
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alias := sliceToArray(a[:])
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sink(alias[0]) // $ hasTaintFlow="index expression"
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alias := [2]string(a[:])
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sink(alias[0]) // $ hasValueFlow="index expression"
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sink(alias[1]) // $ SPURIOUS: hasValueFlow="index expression" // we don't distinguish different elements of arrays or slices
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sink(alias) // $ hasTaintFlow="alias"
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// Compare with the standard dataflow support for arrays
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var b [4]string
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b[0] = source()
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sink(b[0]) // $ hasValueFlow="index expression"
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sink(b[1]) // $ SPURIOUS: hasValueFlow="index expression" // we don't distinguish different elements of arrays or slices
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sink(b) // $ hasTaintFlow="b"
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}

‎go/ql/test/library-tests/semmle/go/dataflow/SliceExpressions/Flows.expected‎

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‎go/ql/test/library-tests/semmle/go/dataflow/SliceExpressions/Flows.ql‎

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import go
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import TestUtilities.InlineFlowTest
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import DefaultFlowTest

‎go/ql/test/library-tests/semmle/go/dataflow/SliceExpressions/main.go‎

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package main
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func source() string {
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return "untrusted data"
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}
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func sink(any) {
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}
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func main() {
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}
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// Value flow with array content through slice expressions
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func arrayBase(base [4]string) {
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base[1] = source()
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slice := base[1:4]
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sink(slice[0]) // $ hasValueFlow="index expression"
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sink(slice[1]) // $ SPURIOUS: hasValueFlow="index expression" // we don't distinguish different elements of arrays or slices
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sink(slice) // $ hasTaintFlow="slice"
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}
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func arrayPointerBase(base *[4]string) {
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base[1] = source()
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slice := base[1:4]
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sink(slice[0]) // $ hasValueFlow="index expression"
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sink(slice[1]) // $ SPURIOUS: hasValueFlow="index expression" // we don't distinguish different elements of arrays or slices
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sink(slice) // $ hasTaintFlow="slice"
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}
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func sliceBase(base []string) {
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base[1] = source()
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slice := base[1:4]
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sink(slice[0]) // $ hasValueFlow="index expression"
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sink(slice[1]) // $ SPURIOUS: hasValueFlow="index expression" // we don't distinguish different elements of arrays or slices
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sink(slice) // $ hasTaintFlow="slice"
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}
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func slicePointerBase(base *[]string) {
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(*base)[1] = source()
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slice := (*base)[1:4]
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sink(slice[0]) // $ hasValueFlow="index expression"
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sink(slice[1]) // $ SPURIOUS: hasValueFlow="index expression" // we don't distinguish different elements of arrays or slices
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sink(slice) // $ hasTaintFlow="slice"
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}

‎go/ql/test/query-tests/Security/CWE-078/CommandInjection.expected‎

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| GitSubcommands.go:10:13:10:27 | call to Query | GitSubcommands.go:15:35:15:41 | tainted |
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| GitSubcommands.go:10:13:10:27 | call to Query | GitSubcommands.go:16:36:16:42 | tainted |
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| SanitizingDoubleDash.go:9:13:9:19 | selection of URL | SanitizingDoubleDash.go:9:13:9:27 | call to Query |
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| SanitizingDoubleDash.go:9:13:9:27 | call to Query | SanitizingDoubleDash.go:13:25:13:31 | tainted |
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| SanitizingDoubleDash.go:9:13:9:27 | call to Query | SanitizingDoubleDash.go:14:23:14:33 | slice expression |
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| SanitizingDoubleDash.go:9:13:9:27 | call to Query | SanitizingDoubleDash.go:39:31:39:37 | tainted |
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| SanitizingDoubleDash.go:9:13:9:27 | call to Query | SanitizingDoubleDash.go:53:21:53:28 | arrayLit |
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| SanitizingDoubleDash.go:9:13:9:27 | call to Query | SanitizingDoubleDash.go:68:31:68:37 | tainted |
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| SanitizingDoubleDash.go:9:13:9:27 | call to Query | SanitizingDoubleDash.go:80:23:80:29 | tainted |
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| SanitizingDoubleDash.go:13:15:13:32 | array literal [array] | SanitizingDoubleDash.go:14:23:14:30 | arrayLit [array] |
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| SanitizingDoubleDash.go:13:25:13:31 | tainted | SanitizingDoubleDash.go:13:15:13:32 | array literal [array] |
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| SanitizingDoubleDash.go:14:23:14:30 | arrayLit [array] | SanitizingDoubleDash.go:14:23:14:33 | slice element node |
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| SanitizingDoubleDash.go:14:23:14:33 | slice element node | SanitizingDoubleDash.go:14:23:14:33 | slice expression [array] |
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| SanitizingDoubleDash.go:14:23:14:33 | slice expression [array] | SanitizingDoubleDash.go:14:23:14:33 | slice expression |
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| SanitizingDoubleDash.go:39:14:39:44 | call to append | SanitizingDoubleDash.go:40:23:40:30 | arrayLit |
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| SanitizingDoubleDash.go:39:31:39:37 | tainted | SanitizingDoubleDash.go:39:14:39:44 | call to append |
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| SanitizingDoubleDash.go:53:14:53:35 | call to append | SanitizingDoubleDash.go:54:23:54:30 | arrayLit |
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| SanitizingDoubleDash.go:69:14:69:35 | call to append | SanitizingDoubleDash.go:70:23:70:30 | arrayLit |
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| SanitizingDoubleDash.go:69:21:69:28 | arrayLit | SanitizingDoubleDash.go:69:14:69:35 | call to append |
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| SanitizingDoubleDash.go:92:13:92:19 | selection of URL | SanitizingDoubleDash.go:92:13:92:27 | call to Query |
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| SanitizingDoubleDash.go:92:13:92:27 | call to Query | SanitizingDoubleDash.go:95:25:95:31 | tainted |
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| SanitizingDoubleDash.go:92:13:92:27 | call to Query | SanitizingDoubleDash.go:96:24:96:34 | slice expression |
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| SanitizingDoubleDash.go:92:13:92:27 | call to Query | SanitizingDoubleDash.go:100:31:100:37 | tainted |
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| SanitizingDoubleDash.go:92:13:92:27 | call to Query | SanitizingDoubleDash.go:101:24:101:34 | slice expression |
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| SanitizingDoubleDash.go:92:13:92:27 | call to Query | SanitizingDoubleDash.go:105:30:105:36 | tainted |
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| SanitizingDoubleDash.go:92:13:92:27 | call to Query | SanitizingDoubleDash.go:106:24:106:31 | arrayLit |
@@ -36,6 +44,16 @@ edges
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| SanitizingDoubleDash.go:92:13:92:27 | call to Query | SanitizingDoubleDash.go:142:31:142:37 | tainted |
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| SanitizingDoubleDash.go:92:13:92:27 | call to Query | SanitizingDoubleDash.go:148:30:148:36 | tainted |
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| SanitizingDoubleDash.go:92:13:92:27 | call to Query | SanitizingDoubleDash.go:152:24:152:30 | tainted |
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| SanitizingDoubleDash.go:95:15:95:32 | array literal [array] | SanitizingDoubleDash.go:96:24:96:31 | arrayLit [array] |
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| SanitizingDoubleDash.go:95:25:95:31 | tainted | SanitizingDoubleDash.go:95:15:95:32 | array literal [array] |
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| SanitizingDoubleDash.go:96:24:96:31 | arrayLit [array] | SanitizingDoubleDash.go:96:24:96:34 | slice element node |
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| SanitizingDoubleDash.go:96:24:96:34 | slice element node | SanitizingDoubleDash.go:96:24:96:34 | slice expression [array] |
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| SanitizingDoubleDash.go:96:24:96:34 | slice expression [array] | SanitizingDoubleDash.go:96:24:96:34 | slice expression |
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| SanitizingDoubleDash.go:100:15:100:38 | array literal [array] | SanitizingDoubleDash.go:101:24:101:31 | arrayLit [array] |
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| SanitizingDoubleDash.go:100:31:100:37 | tainted | SanitizingDoubleDash.go:100:15:100:38 | array literal [array] |
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| SanitizingDoubleDash.go:101:24:101:31 | arrayLit [array] | SanitizingDoubleDash.go:101:24:101:34 | slice element node |
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| SanitizingDoubleDash.go:101:24:101:34 | slice element node | SanitizingDoubleDash.go:101:24:101:34 | slice expression [array] |
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| SanitizingDoubleDash.go:101:24:101:34 | slice expression [array] | SanitizingDoubleDash.go:101:24:101:34 | slice expression |
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| SanitizingDoubleDash.go:105:15:105:37 | slice literal [array] | SanitizingDoubleDash.go:106:24:106:31 | arrayLit |
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| SanitizingDoubleDash.go:105:30:105:36 | tainted | SanitizingDoubleDash.go:105:15:105:37 | slice literal [array] |
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| SanitizingDoubleDash.go:111:14:111:44 | call to append | SanitizingDoubleDash.go:112:24:112:31 | arrayLit |
@@ -68,7 +86,12 @@ nodes
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| GitSubcommands.go:16:36:16:42 | tainted | semmle.label | tainted |
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| SanitizingDoubleDash.go:9:13:9:19 | selection of URL | semmle.label | selection of URL |
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| SanitizingDoubleDash.go:9:13:9:27 | call to Query | semmle.label | call to Query |
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| SanitizingDoubleDash.go:13:15:13:32 | array literal [array] | semmle.label | array literal [array] |
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| SanitizingDoubleDash.go:13:25:13:31 | tainted | semmle.label | tainted |
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| SanitizingDoubleDash.go:14:23:14:30 | arrayLit [array] | semmle.label | arrayLit [array] |
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| SanitizingDoubleDash.go:14:23:14:33 | slice element node | semmle.label | slice element node |
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| SanitizingDoubleDash.go:14:23:14:33 | slice expression | semmle.label | slice expression |
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| SanitizingDoubleDash.go:14:23:14:33 | slice expression [array] | semmle.label | slice expression [array] |
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| SanitizingDoubleDash.go:39:14:39:44 | call to append | semmle.label | call to append |
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| SanitizingDoubleDash.go:39:31:39:37 | tainted | semmle.label | tainted |
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| SanitizingDoubleDash.go:40:23:40:30 | arrayLit | semmle.label | arrayLit |
@@ -83,8 +106,18 @@ nodes
83106
| SanitizingDoubleDash.go:80:23:80:29 | tainted | semmle.label | tainted |
84107
| SanitizingDoubleDash.go:92:13:92:19 | selection of URL | semmle.label | selection of URL |
85108
| SanitizingDoubleDash.go:92:13:92:27 | call to Query | semmle.label | call to Query |
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| SanitizingDoubleDash.go:95:15:95:32 | array literal [array] | semmle.label | array literal [array] |
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| SanitizingDoubleDash.go:95:25:95:31 | tainted | semmle.label | tainted |
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| SanitizingDoubleDash.go:96:24:96:31 | arrayLit [array] | semmle.label | arrayLit [array] |
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| SanitizingDoubleDash.go:96:24:96:34 | slice element node | semmle.label | slice element node |
86113
| SanitizingDoubleDash.go:96:24:96:34 | slice expression | semmle.label | slice expression |
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| SanitizingDoubleDash.go:96:24:96:34 | slice expression [array] | semmle.label | slice expression [array] |
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| SanitizingDoubleDash.go:100:15:100:38 | array literal [array] | semmle.label | array literal [array] |
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| SanitizingDoubleDash.go:100:31:100:37 | tainted | semmle.label | tainted |
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| SanitizingDoubleDash.go:101:24:101:31 | arrayLit [array] | semmle.label | arrayLit [array] |
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| SanitizingDoubleDash.go:101:24:101:34 | slice element node | semmle.label | slice element node |
87119
| SanitizingDoubleDash.go:101:24:101:34 | slice expression | semmle.label | slice expression |
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| SanitizingDoubleDash.go:101:24:101:34 | slice expression [array] | semmle.label | slice expression [array] |
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| SanitizingDoubleDash.go:105:15:105:37 | slice literal [array] | semmle.label | slice literal [array] |
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| SanitizingDoubleDash.go:105:30:105:36 | tainted | semmle.label | tainted |
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| SanitizingDoubleDash.go:106:24:106:31 | arrayLit | semmle.label | arrayLit |

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