scala.lang.security.audit.scalajs-eval.scalajs-eval

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eval() function evaluates JavaScript code represented as a string. Executing JavaScript from a string is an enormous security risk. It is far too easy for a bad actor to run arbitrary code when you use eval(). Do not use eval(). Alternatively: Ensure evaluated content is not definable by external sources. If it’s not possible, strip everything except alphanumeric characters from an input provided for the command string and arguments.

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Defintion

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rules:
  - id: scalajs-eval
    mode: taint
    pattern-sources:
      - patterns:
          - pattern: $PARAM
          - pattern-either:
              - pattern-inside: |
                  def $CTRL(..., $PARAM: $TYPE, ...) = {
                    ...
                  }
              - pattern-inside: |
                  def $CTRL(..., $PARAM: $TYPE, ...) = $A {
                    ...
                  }
              - pattern-inside: |
                  def $CTRL(..., $PARAM: $TYPE, ...) = $A(...) {
                    ...
                  }
    pattern-sinks:
      - patterns:
          - pattern: $JS.eval(...)
          - pattern-inside: |
              import scala.scalajs.$X
              ...
    message: "`eval()` function evaluates JavaScript code represented as a string.
      Executing JavaScript from a string is an enormous security risk. It is far
      too easy for a bad actor to run arbitrary code when you use `eval()`. Do
      not use eval(). Alternatively: Ensure evaluated content is not definable
      by external sources. If it’s not possible, strip everything except
      alphanumeric characters from an input provided for the command string and
      arguments."
    metadata:
      references:
        - https://www.scala-js.org/doc/
      cwe:
        - "CWE-94: Improper Control of Generation of Code ('Code Injection')"
      owasp:
        - A03:2021 - Injection
      category: security
      technology:
        - scala
        - scala-js
      confidence: LOW
      cwe2022-top25: true
      subcategory:
        - vuln
      likelihood: LOW
      impact: HIGH
      license: Commons Clause License Condition v1.0[LGPL-2.1-only]
    languages:
      - scala
    severity: WARNING

Examples

scalajs-eval.scala

package controllers

import scala.scalajs.js

object Smth {
  def call1(code: String) = {
    // ruleid: scalajs-eval
    js.eval(s"console.log($code)")
    // ok: scalajs-eval
    js.eval("FooBar()")
    true
  }
}

object FooBar {
  def call2(code: String) = {
    // ruleid: scalajs-eval
    js.eval("console.log(" + code +")")
    // ok: scalajs-eval
    js.eval("FooBar()")
    true
  }
}