How to upload an image using AWS API Gateway Proxy Integration with S3 - rest

Question

After setting up my API to upload files, I realised that there is a special case where you want to upload a picture (jpg), you defined the binary support at the API, but you get the following error:
The request signature we calculated does not match the signature you
provided. Check your AWS Secret Access Key and signing method.
Consult the service documentation for details.
The Canonical String for this request should have been
'PUT /test/vi-dummy-bucket/testImg2.jpg
content-type:application/x-www-form-urlencoded
host:qhweyos7z2.execute-api.us-west-1.amazonaws.com
x-amz-date:20170808T154441Z
x-amz-security-token: // security token string no quotes
content-type;host;x-amz-date;x-amz-security-token 5fa90f0 ...'
The String-to-Sign should have been
'AWS4-HMAC-SHA256\n20170808T154441Z
20170808/us-west-1/execute-api/aws4_request
f7a38fa ...'
The strange thing is that uploading simple text files works with the exact same api call, then only thing I have to change is
Content-Type 'text/plain'
and write a text in the raw portion of the request.
Not sure if this is a Content-Type issue or a Request Body Issue, if I leave everything in the working state (text/plain & text in the body) and just change the body to binary and set the image, I get the above error.
My API gateway is in us-west-1 region
My S3 bucket is in us-east-1 region
And the request I am using is:
PUT /test/vi-dummy-bucket/testImg2.jpg HTTP/1.1
Host: qhwe7z2.execute-api.us-west-1.amazonaws.com
Content-Type: application/x-www-form-urlencoded
X-Amz-Security-Token: FQoDYX ...
X-Amz-Date: 20170808T154441Z
Authorization: AWS4-HMAC-SHA256
Credential=ASIAJICO6JFTJWN7A/20170808/us-west-1/execute-
api/aws4_request, SignedHeaders=content-type;host;x-amz-date;x-amz-
security-token,
Signature=6a792 ... Cache-Control: no-cache
Postman-Token: e9d1f730-f50b-7e27-70cc-c15a138d8cc6
(Binary Image)
This is another version of the request (same error):
PUT /test/vi-dummy-bucket/testImg2.jpg HTTP/1.1
Content-Type: image/jpeg
x-amz-security-token: FQoDY ...
x-amz-date: 20170808T190134Z
Authorization: AWS4-HMAC-SHA256
Credential=ASIAIZSP5YKVLJ3GVVQA/20170808/us-west-1/execute-
api/aws4_request, SignedHeaders=content-type;host;x-amz-date;x-amz-
security-token,
Signature=b2324 ...
Host: qhos7z2.execute-api.us-west-1.amazonaws.com
Connection: close
User-Agent: Paw/3.1.2 (Macintosh; OS X/10.12.6) GCDHTTPRequest
Content-Length: 823236
--- UPDATE ---
After implementing the sigV4 sigining manually using the generated SDK, the signature is no longer an issue.
The only problem left, is that the generated SDK only accepts a string as the "body", so I have to convert the file to a binary string. Then it passes correctly and a file is created in S3, but the size is now double and its not viewable, as if the binary string wasn't converted back to the binary file. So frustrating...
BTW, I've already tried PASSTHROUGH and CONVERT_TO_BINARY.

Answer 1

Updated: It looks like this may be related to a known error in Postman. For reference here is a related SO question: AWS Signature Error using Postman to access the AWS API Gateway when posting a binary
and here is the bug report for Postman: https://github.com/postmanlabs/postman-app-support/issues/3232
Does the request work if you use an alternate rest client and/or a command line utility like curl or httpie?
If you configured the binary support you should probably set the Content-Type to match the binary content you're sending.
From what you've posted you're sending the binary content with Content-Type application/x-www-form-urlencoded but if the body is actually a binary jpeg file I'd expect that you should be sending Content-Type image/jpeg