ESP8266 has been able to get OAuth token by Device Flow OAuth2.0

After getting OAuth token, I was hitting the REST API endpoint /services/data/v45.0/sobjects/Account with a JSON body in the request:

HTTPSRedirect client;
client.setInsecure(); // does not validate Certificate of the server , this is needed as i do not want to store the fingerprint of the server as it changes  with certificate renewal
String access_token = (*tokenJSON)["access_token"].as<char*>();
String authorization_header_str = "OAuth " + access_token ;
const char* server = "ap8.lightning.force.com";
const char* host="ap8.lightning.force.com";  // Server URL 
client.connect(server, 443)
String url="/services/data/v45.0/sobjects/Account";
String data ="{\"Name\":\"Raja\"}"  ;
client.println("POST " + url + " HTTP/1.1");
client.println("Host: " + (String)host);
client.println("User-Agent: ESP8266/1.0");
client.println("Content-Type: application/json");
client.println("Authorization: "+authorization_header_str);
client.print("Content-Length: ");
String response = client.readString();

The response given back is as follows:

Connected to server!
HTTP/1.1 302 Found
Date: Sat, 16 Feb 2019 06:47:17 GMT
Strict-Transport-Security: max-age=31536001; includeSubDomains
Public-Key-Pins-Report-Only: pin sha256="9n0izTnSRF+W4W4JTq51avSXkWhQB8duS2bxVLfzXsY="; pin-    sha256="5kJvNEMw0KjrCAu7eXY5HZdvyCS13BbA0VJG1RSP91w="; pin-sha256="njN4rRG+22dNXAi+yb8e3UMypgzPUPHlv4+foULwl1g="; max-age=86400; includeSubDomains; report-uri="https://a.forcesslreports.com/hpkp-report/nullm";
Expect-CT: max-age=0; report-uri="https://a.forcesslreports.com/Expect-CT-report/nullm";
X-Content-Type-Options: nosniff
X-XSS-Protection: 1; mode=block
Content-Security-Policy: upgrade-insecure-requests  //// SEE THIS, it says to pgrade to https
X-Robots-Tag: none
Cache-Control: no-cache,must-revalidate,max-age=0,no-store,private
Set-Cookie: BrowserId=tlUX-F_cRg6EKM-qch5thw;Path=/;Domain=.force.com;Expires=Wed, 17-Apr-2019 06:47:17 GMT;Max-Age=5184000

Expires: Thu, 01 Jan 1970 00:00:00 GMT
Location: https://ap8.salesforce.com/services/data/v45.0/sobjects/Account
Content-Length: 0

So, how to solve this redirect problem?

It would be solved if :

  1. If I could get the certificate fingerprint of https://ap8.salesforce.com by some API call or from somewhere(dynamically)

  2. I can somehow upgrade the insecure https request to a secure https request

  3. Some how http to https proxy maybe?

  4. Take something from the response header and some how verify certificate?

Any help is greatly appreciated.


I had a similar issue and solved simply by substituting the server URL with the location indicated in the response

const char* server = "ap8.salesforce.com";
const char* host="ap8.salesforce.com";  // Server URL 
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