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Merge pull request #201 from asger-semmle/string-concatenation-squashed
Approved by esben-semmle
2 parents 2f4aa64 + 1d793c0 commit 4aca8f4

12 files changed

Lines changed: 283 additions & 54 deletions

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‎javascript/ql/src/javascript.qll‎

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@@ -38,6 +38,7 @@ import semmle.javascript.Regexp
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import semmle.javascript.SSA
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import semmle.javascript.StandardLibrary
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import semmle.javascript.Stmt
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import semmle.javascript.StringConcatenation
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import semmle.javascript.Templates
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import semmle.javascript.Tokens
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import semmle.javascript.TypeScript

‎javascript/ql/src/semmle/javascript/StringConcatenation.qll‎

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/**
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* Provides predicates for analyzing string concatenations and their operands.
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*/
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import javascript
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module StringConcatenation {
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/** Gets a data flow node referring to the result of the given concatenation. */
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private DataFlow::Node getAssignAddResult(AssignAddExpr expr) {
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result = expr.flow()
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or
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exists (SsaExplicitDefinition def | def.getDef() = expr |
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result = DataFlow::valueNode(def.getVariable().getAUse()))
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}
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/** Gets the `n`th operand to the string concatenation defining `node`. */
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DataFlow::Node getOperand(DataFlow::Node node, int n) {
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exists (AddExpr add | node = add.flow() |
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n = 0 and result = add.getLeftOperand().flow()
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or
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n = 1 and result = add.getRightOperand().flow())
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or
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exists (TemplateLiteral template | node = template.flow() |
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result = template.getElement(n).flow() and
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not exists (TaggedTemplateExpr tag | template = tag.getTemplate()))
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or
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exists (AssignAddExpr assign | node = getAssignAddResult(assign) |
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n = 0 and result = assign.getLhs().flow()
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or
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n = 1 and result = assign.getRhs().flow())
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or
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exists (DataFlow::ArrayCreationNode array, DataFlow::MethodCallNode call |
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call = array.getAMethodCall("join") and
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call.getArgument(0).mayHaveStringValue("") and
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(
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// step from array element to array
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result = array.getElement(n) and
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node = array
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or
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// step from array to join call
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node = call and
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result = array and
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n = 0
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))
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}
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/** Gets an operand to the string concatenation defining `node`. */
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DataFlow::Node getAnOperand(DataFlow::Node node) {
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result = getOperand(node, _)
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}
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/** Gets the number of operands to the given concatenation. */
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int getNumOperand(DataFlow::Node node) {
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result = strictcount(getAnOperand(node))
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}
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/** Gets the first operand to the string concatenation defining `node`. */
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DataFlow::Node getFirstOperand(DataFlow::Node node) {
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result = getOperand(node, 0)
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}
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/** Gets the last operand to the string concatenation defining `node`. */
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DataFlow::Node getLastOperand(DataFlow::Node node) {
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result = getOperand(node, getNumOperand(node) - 1)
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}
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/**
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* Holds if `src` flows to `dst` through the `n`th operand of the given concatenation operator.
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*/
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predicate taintStep(DataFlow::Node src, DataFlow::Node dst, DataFlow::Node operator, int n) {
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src = getOperand(dst, n) and
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operator = dst
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}
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/**
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* Holds if there is a taint step from `src` to `dst` through string concatenation.
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*/
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predicate taintStep(DataFlow::Node src, DataFlow::Node dst) {
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taintStep(src, dst, _, _)
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}
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}

‎javascript/ql/src/semmle/javascript/dataflow/Nodes.qll‎

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@@ -304,6 +304,47 @@ class ArrayLiteralNode extends DataFlow::ValueNode, DataFlow::DefaultSourceNode
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}
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/** A data flow node corresponding to a `new Array()` or `Array()` invocation. */
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class ArrayConstructorInvokeNode extends DataFlow::InvokeNode {
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ArrayConstructorInvokeNode() {
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getCallee() = DataFlow::globalVarRef("Array")
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}
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/** Gets the `i`th initial element of this array, if one is provided. */
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DataFlow::ValueNode getElement(int i) {
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getNumArgument() > 1 and // A single-argument invocation specifies the array length, not an element.
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result = getArgument(i)
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}
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/** Gets an initial element of this array, if one is provided. */
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DataFlow::ValueNode getAnElement() {
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getNumArgument() > 1 and
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result = getAnArgument()
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}
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}
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/**
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* A data flow node corresponding to the creation or a new array, either through an array literal
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* or an invocation of the `Array` constructor.
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*/
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class ArrayCreationNode extends DataFlow::ValueNode, DataFlow::DefaultSourceNode {
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ArrayCreationNode() {
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this instanceof ArrayLiteralNode or
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this instanceof ArrayConstructorInvokeNode
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}
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/** Gets the `i`th initial element of this array, if one is provided. */
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DataFlow::ValueNode getElement(int i) {
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result = this.(ArrayLiteralNode).getElement(i) or
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result = this.(ArrayConstructorInvokeNode).getElement(i)
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}
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/** Gets an initial element of this array, if one if provided. */
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DataFlow::ValueNode getAnElement() {
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result = getElement(_)
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}
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}
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/**
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* A data flow node corresponding to a `default` import from a module, or a
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* (AMD or CommonJS) `require` of a module.

‎javascript/ql/src/semmle/javascript/dataflow/TaintTracking.qll‎

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@@ -358,19 +358,8 @@ module TaintTracking {
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*/
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class StringConcatenationTaintStep extends AdditionalTaintStep, DataFlow::ValueNode {
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override predicate step(DataFlow::Node pred, DataFlow::Node succ) {
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succ = this and
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(
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// addition propagates taint
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astNode.(AddExpr).getAnOperand() = pred.asExpr() or
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astNode.(AssignAddExpr).getAChildExpr() = pred.asExpr() or
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exists (SsaExplicitDefinition ssa |
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astNode = ssa.getVariable().getAUse() and
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pred.asExpr().(AssignAddExpr) = ssa.getDef()
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)
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or
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// templating propagates taint
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astNode.(TemplateLiteral).getAnElement() = pred.asExpr()
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)
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succ = this and
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StringConcatenation::taintStep(pred, succ)
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}
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}
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‎javascript/ql/src/semmle/javascript/security/dataflow/DomBasedXss.qll‎

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@@ -77,9 +77,9 @@ module DomBasedXss {
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or
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// or it doesn't start with something other than `<`, and so at least
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// _may_ be interpreted as HTML
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not exists (Expr prefix, string strval |
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not exists (DataFlow::Node prefix, string strval |
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isPrefixOfJQueryHtmlString(astNode, prefix) and
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strval = prefix.getStringValue() and
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strval = prefix.asExpr().getStringValue() and
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not strval.regexpMatch("\\s*<.*")
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)
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)
@@ -93,13 +93,14 @@ module DomBasedXss {
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* Holds if `prefix` is a prefix of `htmlString`, which may be intepreted as
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* HTML by a jQuery method.
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*/
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private predicate isPrefixOfJQueryHtmlString(Expr htmlString, Expr prefix) {
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private predicate isPrefixOfJQueryHtmlString(Expr htmlString, DataFlow::Node prefix) {
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any(JQueryMethodCall call).interpretsArgumentAsHtml(htmlString) and
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prefix = htmlString
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prefix = htmlString.flow()
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or
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exists (Expr pred | isPrefixOfJQueryHtmlString(htmlString, pred) |
101-
prefix = pred.(AddExpr).getLeftOperand() or
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prefix = pred.(ParExpr).getExpression()
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exists (DataFlow::Node pred | isPrefixOfJQueryHtmlString(htmlString, pred) |
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prefix = StringConcatenation::getFirstOperand(pred)
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or
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prefix = pred.getAPredecessor()
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)
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}
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‎javascript/ql/src/semmle/javascript/security/dataflow/ServerSideUrlRedirect.qll‎

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@@ -34,33 +34,23 @@ module ServerSideUrlRedirect {
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)
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}
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}
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/**
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* Gets the left operand of `nd` if it is a concatenation.
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*/
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private DataFlow::Node getPrefixOperand(DataFlow::Node nd) {
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exists (Expr e | e instanceof AddExpr or e instanceof AssignAddExpr |
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nd = DataFlow::valueNode(e) and
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result = DataFlow::valueNode(e.getChildExpr(0))
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)
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}
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/**
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* Gets a node that is transitively reachable from `nd` along prefix predecessor edges.
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*/
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private DataFlow::Node prefixCandidate(Sink sink) {
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result = sink or
53-
result = getPrefixOperand(prefixCandidate(sink)) or
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result = prefixCandidate(sink).getAPredecessor()
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result = prefixCandidate(sink).getAPredecessor() or
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result = StringConcatenation::getFirstOperand(prefixCandidate(sink))
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}
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/**
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* Gets an expression that may end up being a prefix of the string concatenation `nd`.
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*/
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private Expr getAPrefix(Sink sink) {
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exists (DataFlow::Node prefix |
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prefix = prefixCandidate(sink) and
63-
not exists(getPrefixOperand(prefix)) and
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not exists(StringConcatenation::getFirstOperand(prefix)) and
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not exists(prefix.getAPredecessor()) and
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result = prefix.asExpr()
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)

‎javascript/ql/src/semmle/javascript/security/dataflow/UrlConcatenation.qll‎

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@@ -11,16 +11,13 @@ import javascript
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* `nd` or one of its operands, assuming that it is a concatenation.
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*/
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private predicate hasSanitizingSubstring(DataFlow::Node nd) {
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exists (Expr e | e = nd.asExpr() |
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(e instanceof AddExpr or e instanceof AssignAddExpr) and
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hasSanitizingSubstring(DataFlow::valueNode(e.getAChildExpr()))
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or
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e.getStringValue().regexpMatch(".*[?#].*")
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)
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nd.asExpr().getStringValue().regexpMatch(".*[?#].*")
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or
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nd.isIncomplete(_)
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hasSanitizingSubstring(StringConcatenation::getAnOperand(nd))
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or
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hasSanitizingSubstring(nd.getAPredecessor())
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or
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nd.isIncomplete(_)
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}
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/**
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* This is considered as a sanitizing edge for the URL redirection queries.
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*/
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predicate sanitizingPrefixEdge(DataFlow::Node source, DataFlow::Node sink) {
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exists (AddExpr add, DataFlow::Node left |
34-
source.asExpr() = add.getRightOperand() and
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sink.asExpr() = add and
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left.asExpr() = add.getLeftOperand() and
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hasSanitizingSubstring(left)
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)
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or
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exists (TemplateLiteral tl, int i, DataFlow::Node elt |
41-
source.asExpr() = tl.getElement(i) and
42-
sink.asExpr() = tl and
43-
elt.asExpr() = tl.getElement([0..i-1]) and
44-
hasSanitizingSubstring(elt)
45-
)
30+
exists (DataFlow::Node operator, int n |
31+
StringConcatenation::taintStep(source, sink, operator, n) and
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hasSanitizingSubstring(StringConcatenation::getOperand(operator, [0..n-1])))
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}

‎javascript/ql/test/library-tests/StringConcatenation/ContainsTwo.expected‎

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| tst.js:3:3:3:12 | x += "two" |
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| tst.js:3:8:3:12 | "two" |
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| tst.js:4:3:4:3 | x |
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| tst.js:4:3:4:14 | x += "three" |
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| tst.js:5:3:5:3 | x |
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| tst.js:5:3:5:13 | x += "four" |
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| tst.js:6:10:6:10 | x |
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| tst.js:12:5:12:26 | x += "o ... + "two" |
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| tst.js:12:10:12:26 | "one" + y + "two" |
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| tst.js:12:22:12:26 | "two" |
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| tst.js:19:11:19:23 | "one" + "two" |
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| tst.js:19:19:19:23 | "two" |
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| tst.js:20:3:20:3 | x |
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| tst.js:20:3:20:25 | x += (" ... "four") |
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| tst.js:21:10:21:10 | x |
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| tst.js:21:10:21:19 | x + "five" |
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| tst.js:25:10:25:32 | ["one", ... three"] |
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| tst.js:25:10:25:41 | ["one", ... oin("") |
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| tst.js:25:18:25:22 | "two" |
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| tst.js:29:10:29:37 | Array(" ... three") |
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| tst.js:29:10:29:46 | Array(" ... oin("") |
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| tst.js:29:23:29:27 | "two" |
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| tst.js:33:10:33:41 | new Arr ... three") |
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| tst.js:33:10:33:50 | new Arr ... oin("") |
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| tst.js:33:27:33:31 | "two" |
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| tst.js:38:11:38:15 | "two" |
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| tst.js:46:23:46:27 | "two" |
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| tst.js:53:10:53:34 | `one ${ ... three` |
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| tst.js:53:19:53:23 | two |
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| tst.js:71:14:71:18 | "two" |
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| tst.js:77:23:77:27 | "two" |

‎javascript/ql/test/library-tests/StringConcatenation/ContainsTwo.ql‎

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import javascript
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3+
// Select all expressions whose string value contains the word "two"
4+
5+
predicate containsTwo(DataFlow::Node node) {
6+
node.asExpr().getStringValue().regexpMatch(".*two.*")
7+
or
8+
containsTwo(node.getAPredecessor())
9+
or
10+
containsTwo(StringConcatenation::getAnOperand(node))
11+
}
12+
13+
from Expr e
14+
where containsTwo(e.flow())
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select e

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