support that two indexOf() calls use the same string-concatenation in getAnEquivalentIndexOfCall()

Author: erik-krogh

javascript/ql/src/Security/CWE-020/IncorrectSuffixCheck.ql

@@ -49,9 +49,20 @@ class IndexOfCall extends DataFlow::MethodCallNode {
     exists(DataFlow::Node recv, string m |
       this.receiverAndMethodName(recv, m) and result.receiverAndMethodName(recv, m)
     |
+      // both directly reference the same value
       result.getArgument(0).getALocalSource() = this.getArgument(0).getALocalSource()
       or
+      // both use the same string literal
       result.getArgument(0).getStringValue() = this.getArgument(0).getStringValue()
+      or
+      // both use the same concatenation of a string and a value
+      exists(Expr origin, StringLiteral str, AddExpr otherAdd |
+        this.getArgument(0).asExpr().(AddExpr).hasOperands(origin, str) and
+        otherAdd = result.getArgument(0).asExpr().(AddExpr)
+      |
+        otherAdd.getAnOperand().(StringLiteral).getStringValue() = str.getStringValue() and
+        otherAdd.getAnOperand().flow().getALocalSource() = origin.flow().getALocalSource()
+      )
     )
   }
 

javascript/ql/test/query-tests/Security/CWE-020/IncorrectSuffixCheck/IncorrectSuffixCheck.expected

@@ -9,4 +9,3 @@
 | tst.js:67:32:67:71 | x.index ... gth - 1 | This suffix check is missing a length comparison to correctly handle indexOf returning -1. |
 | tst.js:76:25:76:57 | index = ... gth - 1 | This suffix check is missing a length comparison to correctly handle indexOf returning -1. |
 | tst.js:80:10:80:57 | x.index ... th + 1) | This suffix check is missing a length comparison to correctly handle indexOf returning -1. |
-| tst.js:110:65:110:164 | trusted ... gth - 1 | This suffix check is missing a length comparison to correctly handle indexOf returning -1. |

javascript/ql/test/query-tests/Security/CWE-020/IncorrectSuffixCheck/tst.js

@@ -107,5 +107,5 @@ function sameCheck(allowedOrigin) {
 
 function sameConcatenation(allowedOrigin) {
     const trustedAuthority = "example.com";
-    return trustedAuthority.indexOf("." + allowedOrigin) > 0 && trustedAuthority.indexOf("." + allowedOrigin) === trustedAuthority.length - allowedOrigin.length - 1; // OK - but currently failing
+    return trustedAuthority.indexOf("." + allowedOrigin) > 0 && trustedAuthority.indexOf("." + allowedOrigin) === trustedAuthority.length - allowedOrigin.length - 1; // OK
 }