Merge pull request #632 from asger-semmle/pseudo-random-bytes

JS: add crypto.pseudoRandomBytes as source in InsecureRandomness.ql

Author: Max Schaefer

change-notes/1.20/analysis-javascript.md

@@ -20,6 +20,7 @@
 | **Query**                                  | **Expected impact**          | **Change**                                                                   |
 |--------------------------------------------|------------------------------|------------------------------------------------------------------------------|
 | Client-side cross-site scripting           | More results                 | This rule now recognizes WinJS functions that are vulnerable to HTML injection. |
+| Insecure randomness | More results | This rule now flags insecure uses of `crypto.pseudoRandomBytes`. |
 | Unused parameter                           | Fewer false-positive results | This rule no longer flags parameters with leading underscore. |
 | Unused variable, import, function or class | Fewer false-positive results | This rule now flags fewer variables that are implictly used by JSX elements, and no longer flags variables with leading underscore. |
 

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

@@ -68,7 +68,7 @@ module InsecureRandomness {
    * A simple random number generator that is not cryptographically secure.
    */
   class DefaultSource extends Source, DataFlow::ValueNode {
-    override CallExpr astNode;
+    override InvokeExpr astNode;
 
     DefaultSource() {
       exists(DataFlow::ModuleImportNode mod, string name | mod.getPath() = name |
@@ -98,6 +98,9 @@ module InsecureRandomness {
       or
       // (new require('chance')).<name>()
       this = DataFlow::moduleImport("chance").getAnInstantiation().getAMemberInvocation(_)
+      or
+      // require('crypto').pseudoRandomBytes()
+      this = DataFlow::moduleMember("crypto", "pseudoRandomBytes").getAnInvocation()
     }
   }
 

javascript/ql/test/library-tests/Security/CWE-338/InsecureRandomnessSource.expected

@@ -6,3 +6,5 @@
 | tst.js:15:1:15:12 | randomSeed() |
 | tst.js:18:1:18:14 | uniqueRandom() |
 | tst.js:22:1:22:12 | chance.XYZ() |
+| tst.js:25:1:25:29 | crypto. ... es(100) |
+| tst.js:26:1:26:33 | new cry ... es(100) |

javascript/ql/test/library-tests/Security/CWE-338/tst.js

@@ -20,3 +20,7 @@ uniqueRandom();
 var Chance = require('chance'),
     chance = new Chance();
 chance.XYZ();
+
+let crypto = require('crypto');
+crypto.pseudoRandomBytes(100);
+new crypto.pseudoRandomBytes(100);