I'm trying to use the AWS API Gateway "Gateway responses" feature to set a custom header on specific authorization failure responses. The documentation in the console says:
Response headers
Specifies the response headers to return to the client. You can specify in single quotes an incoming request parameter or static value to return in the header.
No examples are given for how to utilize incoming parameters, and the typical VTL parameters are not valid. Specifically, I'm attempting to set Location header value to /shell?target=$context.path. I've tried entering this in as many ways as I can guess but I either get an "Invalid mapping expression specified" error or the value I put is just returned as a plain string (i.e. not interpolated).
I'm able to work around the issue by returning a full HTML page using the "Response templates" section on the same page, reference $context.path, and use a meta-refresh to redirect the browser. It works, but I would much rather use the Location header the way it's supposed to be.
I don't know why $context.path works in the following template but not the ones I've tried for the header:
<html>
<head>
<meta http-equiv="refresh" content="0;url=/shell?target=$context.path">
</head>
<body>
Authorizing...
</body>
</html>
AWS OFFICIALUpdated 2 years ago
I should probably add that inserting a Lambda call is not an acceptable solution. The HTML hack I have is better than maintaining more code.