How to authenticate with AWS IAM Roles Anywhere in C#

I am trying to get the temporary credentials for Iam role anywhere. I am using the input parameters

using System.Security.Cryptography; using System.Security.Cryptography.X509Certificates; using System.Text;

namespace ConsoleApp1 { internal class Program { static void Main(string[] args) { token().GetAwaiter().GetResult();

    }

    static string HexToDecimal(string hex)
    {
        List<int> dec = new List<int> { 0 };   // decimal result
        foreach (char c in hex)
        {
            int carry = Convert.ToInt32(c.ToString(), 16);
            // initially holds decimal value of current hex digit;
            // subsequently holds carry-over for multiplication
            for (int i = 0; i < dec.Count; ++i)
            {
                int val = dec[i] * 16 + carry;
                dec[i] = val % 10;
                carry = val / 10;
            }
            while (carry > 0)
            {
                dec.Add(carry % 10);
                carry /= 10;
            }
        }
        var chars = dec.Select(d => (char)('0' + d));
        var cArr = chars.Reverse().ToArray();
        return new string(cArr);
    }

    static async Task token()
    {
        private_key_file = ''  # PEM format
        public_certificate_file = ''  # PEM format
        region = ''  # AWS Region
        duration_seconds = '1200'  # From 900 to 3600
        profile_arn = ''
        role_arn = ''  # IAM Role ARN
        session_name = 'test_session'
        trust_anchor_arn = ''
        // ************* REQUEST VALUES *************
        string method = "POST";
        string service = "rolesanywhere";
        string host = $"rolesanywhere.{region}.amazonaws.com";
        string endpoint = $"https://rolesanywhere.{region}.amazonaws.com";
        string content_type = "application/json";

        // Load public certificate
        string amz_x509;
        string serial_number_dec;
        try
        {
            string pemContents = File.ReadAllText(public_certificate_file);
            string[] pemLines = pemContents.Split('\n');
            StringBuilder base64String = new StringBuilder();
            for (int i = 1; i < pemLines.Length - 1; i++)
            {
                base64String.Append(pemLines[i]);
            }
            byte[] certBytes = Convert.FromBase64String(base64String.ToString());

            X509Certificate2 cert = new X509Certificate2(certBytes);
            var snum = cert.SerialNumber;

            serial_number_dec = HexToDecimal(snum);
            amz_x509 = Convert.ToBase64String(cert.Export(X509ContentType.Cert));
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Failed to load public certificate: {ex.Message}");
            return;
        }

        // Request parameters for CreateSession--passed in a JSON block.
        string request_parameters = $"{{\"durationSeconds\": {duration_seconds},\"profileArn\": \"{profile_arn}\",\"roleArn\": \"{role_arn}\",\"sessionName\": \"{session_name}\",\"trustAnchorArn\": \"{trust_anchor_arn}\"}}";

        // Create a date for headers and the credential string
        DateTime t = DateTime.UtcNow;
        string amz_date = t.ToString("yyyyMMddTHHmmssZ");
        string date_stamp = t.ToString("yyyyMMdd");

        // ************* TASK 1: CREATE A CANONICAL REQUEST *************
        // Step 1 is to define the verb (GET, POST, etc.)--already done.
        string canonical_uri = "/sessions";
        string canonical_querystring = "";
        string canonical_headers = "content-type:" + content_type + @"\n" + "host:" + host + @"\n" + "x-amz-date:" + amz_date + @"\n" + "x-amz-x509:" + amz_x509 + @"\n";
        string signed_headers = "content-type;host;x-amz-date;x-amz-x509";
        string payload_hash = BitConverter.ToString(SHA256.Create().ComputeHash(Encoding.UTF8.GetBytes(request_parameters))).Replace("-", "").ToLower();
        string canonical_request = method + @"\n" + canonical_uri + @"\n" + canonical_querystring + @"\n" + canonical_headers + @"\n" + signed_headers + @"\n" + payload_hash;

        // ************* TASK 2: CREATE THE STRING TO SIGN*************
        string algorithm = "AWS4-X509-RSA-SHA256";
        string credential_scope = $"{date_stamp}/{region}/{service}/aws4_request";
        string string_to_sign = algorithm + @"\n" + amz_date + @"\n" + credential_scope + @"\n" + BitConverter.ToString(SHA256.Create().ComputeHash(Encoding.UTF8.GetBytes(canonical_request))).Replace("-", "").ToLower();

        // ************* TASK 3: CALCULATE THE SIGNATURE *************
        byte[] signature;
        {
            using (var rsa = RSA.Create(8192))
            {
                var dataToSign = Encoding.UTF8.GetBytes(string_to_sign);
                rsa.ImportFromPem(File.ReadAllText(private_key_file));
                signature = rsa.SignData(dataToSign, HashAlgorithmName.SHA512, RSASignaturePadding.Pkcs1);
            }
        }

        string signature_hex = BitConverter.ToString(signature).Replace("-", "").ToLower();

        // ************* TASK 4: ADD SIGNING INFORMATION TO THE REQUEST *************
        string authorization_header = $"{algorithm} Credential={serial_number_dec.ToString()}/{credential_scope}, SignedHeaders={signed_headers}, Signature={signature_hex}";

        HttpClient httpClient = new HttpClient();
        httpClient.DefaultRequestHeaders.Clear();
        httpClient.DefaultRequestHeaders.Add("X-Amz-Date", amz_date);
        httpClient.DefaultRequestHeaders.Add("X-Amz-X509", amz_x509);
        httpClient.DefaultRequestHeaders.Add("Accept", "application/json");
        httpClient.DefaultRequestHeaders.Add("Authorization", authorization_header);

        // ************* SEND THE REQUEST *************
        Console.WriteLine("\nBEGIN REQUEST++++++++++++++++++++++++++++++++++++");
        Console.WriteLine($"Request URL = {endpoint}");

        StringContent strContent = new StringContent(request_parameters, Encoding.UTF8, "application/json");

        HttpResponseMessage response = await httpClient.PostAsync(endpoint + canonical_uri, strContent);

        Console.WriteLine("\nRESPONSE++++++++++++++++++++++++++++++++++++");
        Console.WriteLine($"Response code: {response.StatusCode}");
        Console.WriteLine(await response.Content.ReadAsStringAsync());
    }
}

}

I am using the method below to add Authorization httpClient.DefaultRequestHeaders.Add("Authorization", authorization_header);

authorization_header value is in this format -> AWS4-X509-RSA-SHA256 Credential={{Certificate_serial_number}}/20240321/{{region}}/rolesanywhere/aws4_request, SignedHeaders=content-type;host;x-amz-date;x-amz-x509, Signature={{signature}} I am facing problem while adding the Authorization header. Error message is authorization_header format is invalid.

We developed this code taking refence of python code which you find using this link https://nerdydrunk.info/aws:roles_anywhere This python code is working.