JavaScript: Use shared library for serverless

javascript/ql/lib/semmle/javascript/frameworks/ServerLess.qll

@@ -1,120 +1,52 @@
 /**
  * Provides classes and predicates for working with serverless handlers.
  * E.g. [AWS](https://docs.aws.amazon.com/lambda/latest/dg/nodejs-handler.html) or [serverless](https://npmjs.com/package/serverless)
+ * In particular a `RemoteFlowSource` is added for AWS, Alibaba, and serverless.
  */
 
 import javascript
+import codeql.serverless.ServerLess
+
+private module YamlImpl implements Input {
+  import semmle.javascript.Files
+  import semmle.javascript.YAML
+}
+
+module SL = ServerLess<YamlImpl>;
 
 /**
- * Provides classes and predicates for working with serverless handlers.
- * In particular a `RemoteFlowSource` is added for AWS, Alibaba, and serverless.
+ * Gets a function that is a serverless request handler.
+ *
+ * For example: if an AWS serverless resource contains the following properties (in the "template.yml" file):
+ * ```yaml
+ * Handler: mylibrary.handler
+ * Runtime: nodejs12.x
+ * CodeUri: backend/src/
+ * ```
+ *
+ * And a file "mylibrary.js" exists in the folder "backend/src" (relative to the "template.yml" file).
+ * Then the result of this predicate is a function exported as "handler" from "mylibrary.js".
+ * The "mylibrary.js" file could for example look like:
+ *
+ * ```JavaScript
+ * module.exports.handler = function (event) { ... }
+ * ```
  */
-private module ServerLess {
-  /**
-   * Holds if the `.yml` file `ymlFile` contains a serverless configuration with `handler` and `codeURI` properties.
-   * `codeURI` defaults to the empty string if no explicit value is set in the configuration.
-   */
-  private predicate hasServerlessHandler(File ymlFile, string handler, string codeUri) {
-    exists(YamlMapping resource | ymlFile = resource.getFile() |
-      // There exists at least "AWS::Serverless::Function" and "Aliyun::Serverless::Function"
-      resource.lookup("Type").(YamlScalar).getValue().regexpMatch(".*::Serverless::Function") and
-      exists(YamlMapping properties | properties = resource.lookup("Properties") |
-        handler = properties.lookup("Handler").(YamlScalar).getValue() and
-        if exists(properties.lookup("CodeUri"))
-        then codeUri = properties.lookup("CodeUri").(YamlScalar).getValue()
-        else codeUri = ""
-      )
-      or
-      // The `serverless` library, which specifies a top-level `functions` property
-      exists(YamlMapping functions |
-        functions = resource.lookup("functions") and
-        not exists(resource.getParentNode()) and
-        handler = functions.getValue(_).(YamlMapping).lookup("handler").(YamlScalar).getValue() and
-        codeUri = ""
-      )
-    )
-  }
-
-  /**
-   * Gets a string where an ending "/." is simplified to "/" (if it exists).
-   */
-  bindingset[base]
-  private string removeTrailingDot(string base) {
-    if base.regexpMatch(".*/\\.")
-    then result = base.substring(0, base.length() - 1)
-    else result = base
-  }
-
-  /**
-   * Gets a string where a leading "./" is simplified to "" (if it exists).
-   */
-  bindingset[base]
-  private string removeLeadingDotSlash(string base) {
-    if base.regexpMatch("\\./.*") then result = base.substring(2, base.length()) else result = base
-  }
-
-  /**
-   * Gets a path to a file from a `codeURI` property and a file name from a serverless configuration.
-   *
-   * For example if `codeURI` is "function/." and `file` is "index", then the result becomes "function/index.js".
-   */
-  bindingset[codeUri, file]
-  private string getPathFromHandlerProperties(string codeUri, string file) {
-    exists(string folder | folder = removeLeadingDotSlash(removeTrailingDot(codeUri)) |
-      result = folder + file + ".js"
-    )
-  }
-
-  /**
-   * Holds if `file` has a serverless handler function with name `func`.
-   */
-  private predicate hasServerlessHandler(File file, string func) {
-    exists(File ymlFile, string handler, string codeUri, string fileName |
-      hasServerlessHandler(ymlFile, handler, codeUri) and
-      // Splits a `handler` into two components. The `fileName` to the left of the dot, and the `func` to the right.
-      // E.g. if `handler` is "index.foo", then `fileName` is "index" and `func` is "foo".
-      exists(string pattern | pattern = "(.*)\\.(.*)" |
-        fileName = handler.regexpCapture(pattern, 1) and
-        func = handler.regexpCapture(pattern, 2)
-      )
-    |
-      file.getAbsolutePath() =
-        ymlFile.getParentContainer().getAbsolutePath() + "/" +
-          getPathFromHandlerProperties(codeUri, fileName)
-    )
-  }
-
-  /**
-   * Gets a function that is a serverless request handler.
-   *
-   * For example: if an AWS serverless resource contains the following properties (in the "template.yml" file):
-   * ```yaml
-   * Handler: mylibrary.handler
-   * Runtime: nodejs12.x
-   * CodeUri: backend/src/
-   * ```
-   *
-   * And a file "mylibrary.js" exists in the folder "backend/src" (relative to the "template.yml" file).
-   * Then the result of this predicate is a function exported as "handler" from "mylibrary.js".
-   * The "mylibrary.js" file could for example look like:
-   *
-   * ```JavaScript
-   * module.exports.handler = function (event) { ... }
-   * ```
-   */
-  private DataFlow::FunctionNode getAServerlessHandler() {
-    exists(File file, string handler, Module mod | hasServerlessHandler(file, handler) |
-      mod.getFile() = file and
-      result = mod.getAnExportedValue(handler).getAFunctionValue()
-    )
-  }
-
-  /**
-   * A serverless request handler event, seen as a RemoteFlowSource.
-   */
-  private class ServerlessHandlerEventAsRemoteFlow extends RemoteFlowSource {
-    ServerlessHandlerEventAsRemoteFlow() { this = getAServerlessHandler().getParameter(0) }
-
-    override string getSourceType() { result = "Serverless event" }
-  }
+private DataFlow::FunctionNode getAServerlessHandler() {
+  exists(File file, string stem, string handler, Module mod |
+    SL::hasServerlessHandler(stem, handler, _, _) and
+    file.getAbsolutePath() = stem + ".js"
+  |
+    mod.getFile() = file and
+    result = mod.getAnExportedValue(handler).getAFunctionValue()
+  )
+}
+
+/**
+ * A serverless request handler event, seen as a RemoteFlowSource.
+ */
+private class ServerlessHandlerEventAsRemoteFlow extends RemoteFlowSource {
+  ServerlessHandlerEventAsRemoteFlow() { this = getAServerlessHandler().getParameter(0) }
+
+  override string getSourceType() { result = "Serverless event" }
 }