Support base URLs with optional query params

The example lambda event handlers currently build a query string which
presumes that at least one parameter exists. This change will now
support the situation where there are no parameters.

Author: crftr

5-Create_CloudFront_SignedURL_Canned/cf_signedurl_canned.js

@@ -39,8 +39,9 @@ exports.handler = async (event, data, callback) => {
   signer.update(cannedPolicy);
   let signedPolicy = signer.sign(await getKeyFromSecretsManager(), 'base64');
   signedPolicy = signedPolicy.replace(/[+=/]/g, m => replacementChars[m]);
-
-  const cfSignedUrl = `${event.baseUrl}&Expires=${expiration}&Signature=${signedPolicy}&Key-Pair-Id=${process.env.amazonCloudFrontKeyPairId}`;
+  
+  const paramDelimiter = (event.baseUrl.indexOf('?') === -1) ? '?' : '&';
+  const cfSignedUrl = `${event.baseUrl}${paramDelimiter}Expires=${expiration}&Signature=${signedPolicy}&Key-Pair-Id=${process.env.amazonCloudFrontKeyPairId}`;
 
   const response = {
     cfSignedUrl: cfSignedUrl

6-Create_CloudFront_SignedURL_Custom/cf_signedurl_custom.js

@@ -47,7 +47,8 @@ exports.handler = async (event, data, callback) => {
   let signedPolicy = signer.sign(await getKeyFromSecretsManager(), 'base64');
   signedPolicy = signedPolicy.replace(/[+=/]/g, m => replacementChars[m]);
 
-  const cfSignedUrl = `${event.baseUrl}&Policy=${encodedPolicy}&Signature=${signedPolicy}&Key-Pair-Id=${process.env.amazonCloudFrontKeyPairId}`;
+  const paramDelimiter = (event.baseUrl.indexOf('?') === -1) ? '?' : '&';
+  const cfSignedUrl = `${event.baseUrl}${paramDelimiter}Policy=${encodedPolicy}&Signature=${signedPolicy}&Key-Pair-Id=${process.env.amazonCloudFrontKeyPairId}`;
 
   const response = {
     cfSignedUrl: cfSignedUrl