SPAM checking/detecting/filtering #99

index.js

@@ -24,6 +24,8 @@ console.log("AWS Lambda SES Forwarder // @arithmetric // Version 5.0.0");
 //   `[email protected]` would be treated as if it was sent to
 //   `[email protected]`.
 //
+// - rejectSpam: Rejects any emails that fail the SES spam checks.
+//
 // - forwardMapping: Object where the key is the lowercase email address from
 //   which to forward and the value is an array of email addresses to which to
 //   send the message.
@@ -41,6 +43,7 @@ var defaultConfig = {
   emailBucket: "s3-bucket-name",
   emailKeyPrefix: "emailsPrefix/",
   allowPlusSign: true,
+  rejectSpam: false,
   forwardMapping: {
     "[email protected]": [
       "[email protected]",
@@ -85,6 +88,36 @@ exports.parseEvent = function(data) {
   return Promise.resolve(data);
 };
 
+/**
+ * Filters out SPAM emails
+ *
+ * @param {object} data - Data bundle with context, email, etc.
+ *
+ * @return {object} - Promise resolved with data.
+ */
+exports.filterSpam = function(data) {
+  const receipt = data.event.Records[0].ses.receipt;
+  if (data.config.rejectSpam && receipt) {
+    const verdicts = [
+      'spamVerdict',
+      'virusVerdict',
+      'spfVerdict',
+      'dkimVerdict',
+      'dmarcVerdict'
+    ];
+    for (let key of verdicts) {
+      const verdict = receipt[key];
+      if (verdict && verdict.status === 'FAIL') {
+        return Promise.reject(
+          new Error('Error: Email failed spam filter: ' + key)
+        );
+      }
+    }
+  }
+
+  return Promise.resolve(data);
+};
+
 /**
  * Transforms the original recipients to the desired forwarded destinations.
  *
@@ -340,6 +373,7 @@ exports.handler = function(event, context, callback, overrides) {
   var steps = overrides && overrides.steps ? overrides.steps :
     [
       exports.parseEvent,
+      exports.filterSpam,
       exports.transformRecipients,
       exports.fetchMessage,
       exports.processMessage,

test/filterSpam.js

@@ -0,0 +1,120 @@
+
+/* global describe, it */
+
+var assert = require("assert");
+var fs = require("fs");
+
+var index = require("../index");
+
+describe('index.js', function() {
+  describe('#filterSpam()', function() {
+    it('skip if not configured',
+      function(done) {
+        var data = {
+          event: JSON.parse(fs.readFileSync("test/assets/event.json")),
+          log: console.log,
+          context: {},
+          config: {}
+        };
+        index.filterSpam(data)
+          .then(function() {
+            assert.ok(true, "filterSpam returned successfully");
+            done();
+          });
+      });
+
+    it('skip if filtering disabled',
+      function(done) {
+        var data = {
+          event: JSON.parse(fs.readFileSync("test/assets/event.json")),
+          log: console.log,
+          context: {},
+          config: {rejectSpam: false}
+        };
+        index.filterSpam(data)
+          .then(function() {
+            assert.ok(true, "filterSpam returned successfully");
+            done();
+          });
+      });
+
+    it('allow good message through',
+      function(done) {
+        var data = {
+          event: JSON.parse(fs.readFileSync("test/assets/event.json")),
+          log: console.log,
+          context: {},
+          config: {rejectSpam: true}
+        };
+        index.filterSpam(data)
+          .then(function() {
+            assert.ok(true, "filterSpam returned successfully");
+            done();
+          });
+      });
+
+    it('should reject spam messages',
+      function(done) {
+        var data = {
+          event: JSON.parse(fs.readFileSync("test/assets/event.json")),
+          log: console.log,
+          context: {},
+          config: {rejectSpam: true}
+        };
+        data.event.Records[0].ses.receipt.spamVerdict.status = "FAIL";
+        index.filterSpam(data)
+          .catch(function(err) {
+            assert.ok(err, "Error: Email failed spam filter: spamVerdict");
+            done();
+          });
+      });
+
+    it('should reject messages that might have a virus',
+      function(done) {
+        var data = {
+          event: JSON.parse(fs.readFileSync("test/assets/event.json")),
+          log: console.log,
+          context: {},
+          config: {rejectSpam: true}
+        };
+        data.event.Records[0].ses.receipt.virusVerdict.status = "FAIL";
+        index.filterSpam(data)
+          .catch(function(err) {
+            assert.ok(err, "Error: Email failed spam filter: virusVerdict");
+            done();
+          });
+      });
+
+    it('should reject messages that fail a DKIM check',
+      function(done) {
+        var data = {
+          event: JSON.parse(fs.readFileSync("test/assets/event.json")),
+          log: console.log,
+          context: {},
+          config: {rejectSpam: true}
+        };
+        data.event.Records[0].ses.receipt.dkimVerdict.status = "FAIL";
+        index.filterSpam(data)
+          .catch(function(err) {
+            assert.ok(err, "Error: Email failed spam filter: dkimVerdict");
+            done();
+          });
+      });
+
+    it('should reject messages that fail a SPF check',
+      function(done) {
+        var data = {
+          event: JSON.parse(fs.readFileSync("test/assets/event.json")),
+          log: console.log,
+          context: {},
+          config: {rejectSpam: true}
+        };
+        data.event.Records[0].ses.receipt.spfVerdict.status = "FAIL";
+        index.filterSpam(data)
+          .catch(function(err) {
+            assert.ok(err, "Error: Email failed spam filter: spfVerdict");
+            done();
+          });
+      });
+  });
+});