Azure Log Analytics Workspace Request Forbidden

Question

I am trying to send logs from my application to an Azure Log Analytics Workspace, in order to do that I develop the following code based on what I found in https://learn.microsoft.com/en-us/azure/azure-monitor/logs/data-collector-api

using maintenance.messaging;
using System;
using System.Collections.Generic;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
namespace maintenance.dataaccessobjects
{
    public class LogAnalyticsWorkspaceDAO
    {
        private static LogAnalyticsWorkspaceDAO _Instance { get; set; }
        private String WorkspaceId { get; set; } = AzureKeyVaultDAO.Instance.GetSecret("WorkspaceId"); //Get WorkspaceId from KeyVault
        private String SharedKey { get; set; } = AzureKeyVaultDAO.Instance.GetSecret("SharedKey"); //Get SharedKey from KeyVault
        private String ApiVersion { get; set; } = AzureKeyVaultDAO.Instance.GetSecret("LAWApiVersion"); //Get API Version from KeyVault 2016-04-01
        private String LogType { get; set; } = AzureKeyVaultDAO.Instance.GetSecret("LogType"); //Get LogType from KeyVault ApplicationLog
        private LogAnalyticsWorkspaceDAO()
        {
        }
        public static LogAnalyticsWorkspaceDAO Instance
        {
            get
            {
                if (_Instance == null)
                {
                    _Instance = new LogAnalyticsWorkspaceDAO();
                }
                return _Instance;
            }
        }
        private string GetSignature(String Method, Int32 ContentLength, String ContentType, DateTime Date, String Resource)
        {
            string Message = $"{Method}\n{ContentLength}\n{ContentType}\nx-ms-date:{Date}\n{Resource}";
            byte[] Bytes = Encoding.UTF8.GetBytes(Message);
            HMACSHA256 Encryptor = new HMACSHA256(Convert.FromBase64String(SharedKey));
            return $"SharedKey {WorkspaceId}:{Convert.ToBase64String(Encryptor.ComputeHash(Bytes))}";
        }
        public async Task<String> Post(String Message)
        {
            DateTime Date = DateTime.UtcNow;
            Dictionary<String, String> Headers = new Dictionary<String, String>();
            MessageSender MessageSender = new MessageSender(new Uri($"https://{WorkspaceId}.ods.opinsights.azure.com/api/logs?api-version={ApiVersion}"));
            Headers.Add("Method", "POST");
            Headers.Add("Log-Type", LogType);
            Headers.Add("x-ms-date", Date.ToString("r"));
            Headers.Add("Authorization", GetSignature("POST", Message.Length, "application/json", Date, "/api/logs"));
            return await MessageSender.Post(MessageSender.Message(Headers, Message));
        }
    }
}
using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
namespace maintenance.messaging
{
    public class MessageSender : IDisposable
    {
        private readonly HttpClient Client;
        private Uri Url { get; set; }
        public MessageSender(Uri Url)
        {
            this.Client = new HttpClient();
            this.Url = Url;
        }
        public HttpRequestMessage Message(Dictionary<String, String> Headers, String Message)
        {
            HttpRequestMessage Request = new HttpRequestMessage(HttpMethod.Post, this.Url);
            Request.Content = new StringContent(Message, Encoding.UTF8, "application/json");
            foreach (KeyValuePair<String, String> Header in Headers)
            {
                Request.Headers.Add(Header.Key, Header.Value);
            }
            return Request;
        }
        public async Task<String> Post(HttpRequestMessage Request)
        {
            HttpResponseMessage Response = await Client.SendAsync(Request);
            Response.EnsureSuccessStatusCode();
            return await Response.Content.ReadAsStringAsync();
        }
        public void Dispose()
        {
            Client?.Dispose();
        }
    }
}

However I always fall under a 403 Forbiden, I guess the error should be in the Authorization header (Signature generation)
Do you know what I am missing? I tried looking for other signature generations but didn't find anything new

I may be wrong, but as far as I can see SharedKey is not Base64 encoded, so I just try with

HMACSHA256 Encryptor = new HMACSHA256(Encoding.UTF8.GetBytes(SharedKey));

But get the same error 403 Forbidden

Answer 1

However I always fall under a 403 Forbiden, I guess the error should be in the Authorization header (Signature generation) Do you know what I am missing? I tried looking for other signature generations but didn't find anything new.

Yes you are correct @delucaezequiel, This error is caused due to InvalidAuthorization ,Make sure that you have added the correct value of workspace ID and connection key which are valid.

For the encoded part to configure in code please Refer this SO THREAD as suggested by @GreenRock.

For more information please refer this Blog.