Flutter S3 download using presigned URL issue - flutter

Question

I am attempting to use presigned urls to download files on s3 to my flutter app. I have a lambda function that generates and passes the url. The presigned url works fine by itself but once it gets into flutter the data is somehow changed and AWS comes back with 404 error. It seems that somehow the token is corrupted.
If have tried parsing the data returned as XML, JSON and with no parsing what so ever. I have also changed the output from the lambda to be JSON or just send the url directly, neither solved the issue. None of these approaches have worked. Do I have to extract XML or something?
Here's the code that gets the url from a lambda call:
http.Response res1 = await http.get(url2);
dynamic data1 = cnv.jsonDecode(res1.body); //XmlDocument.parse(res1.body);
if (data1['theStatus'] == "error") {
String theStatus2 = "error";
return theStatus2;
} else {
(data1['theUrl']);
writeData(77, data1['theUrl']); //save in Hive
return data1;
}
Here's the code that uses the presigned url:
tFuture<File?> downloadFile(String url, String name) async {
final appStorage = await getApplicationDocumentsDirectory();
final file = File('${appStorage.path}/$name');
final response = await Dio().get(
url,
options: Options(
responseType: ResponseType.bytes,
followRedirects: false,
receiveTimeout: 0,
),
);
final raf = file.openSync(mode: FileMode.write);
raf.writeFromSync(response.data);
print('file saved');
await raf.close();
return file;
}
http.Response res1 = await http.get(url2);
final data1 = cnv.jsonDecode(res1.body); //XmlDocument.parse(res1.body);
if (data1['theStatus'] == "error") {
String theStatus2 = "error";
return theStatus2;
} else {
String theUrl = data1['theUrl'];
writeData(77, data1['theUrl']); //save in Hive
return theUrl;
}
If I hard code theUrl above with a presigned url from the browser accessing the lambda everything works fine...
I believe the issue is something to do with XML but when I use XML parse it throws an error no root... Any help appreciated.

Answer 1

Found the issue... my lambda function did not have the correct credentials. I found the solution using this:
How I can generated pre-signed url for different file versions of AWS S3 objects in NodeJS?