Write a custom authenticate handler.

1 files changed, 96 insertions, 0 deletions

diff --git a/Timeline/Authenticate/AuthHandler.cs b/Timeline/Authenticate/AuthHandler.cs
new file mode 100644
index 00000000..71d8aeaa
--- /dev/null
+++ b/Timeline/Authenticate/AuthHandler.cs
@@ -0,0 +1,96 @@
+using Microsoft.AspNetCore.Authentication;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using Microsoft.IdentityModel.Tokens;
+using Microsoft.Net.Http.Headers;
+using System;
+using System.IdentityModel.Tokens.Jwt;
+using System.Text.Encodings.Web;
+using System.Threading.Tasks;
+
+namespace Timeline.Authenticate
+{
+    static class AuthConstants
+    {
+        public const string Scheme = "Bearer";
+        public const string DisplayName = "My Jwt Auth Scheme";
+    }
+
+    class AuthOptions : AuthenticationSchemeOptions
+    {
+        /// <summary>
+        /// The query param key to search for token. If null then query params are not searched for token. Default to <c>"token"</c>.
+        /// </summary>
+        public string TokenQueryParamKey { get; set; } = "token";
+
+        public TokenValidationParameters TokenValidationParameters { get;
+            set; } 
+            = new TokenValidationParameters();
+    }
+
+    class AuthHandler : AuthenticationHandler<AuthOptions>
+    {
+        private readonly ILogger<AuthHandler> _logger;
+
+        public AuthHandler(IOptionsMonitor<AuthOptions> options, ILoggerFactory logger, UrlEncoder encoder, ISystemClock clock)
+            : base(options, logger, encoder, clock)
+        {
+            _logger = logger.CreateLogger<AuthHandler>();
+        }
+
+        // return null if no token is found
+        private string ExtractToken()
+        {
+            // check the authorization header
+            string header = Request.Headers[HeaderNames.Authorization];
+            if (!string.IsNullOrEmpty(header) && header.StartsWith("Bearer ", StringComparison.OrdinalIgnoreCase))
+            {
+                var token = header.Substring("Bearer ".Length).Trim();
+                _logger.LogInformation("Token is found in authorization header. Token is {} .", token);
+                return token;
+            }
+
+            // check the query params
+            var paramQueryKey = Options.TokenQueryParamKey;
+            if (!string.IsNullOrEmpty(paramQueryKey))
+            {
+                string token = Request.Query[paramQueryKey];
+                if (!string.IsNullOrEmpty(token))
+                {
+                    _logger.LogInformation("Token is found in query param with key \"{}\". Token is {} .", paramQueryKey, token);
+                    return token;
+                }
+            }
+
+            // not found anywhere then return null
+            return null;
+        }
+
+        protected override async Task<AuthenticateResult> HandleAuthenticateAsync()
+        {
+            var token = ExtractToken();
+            if (string.IsNullOrEmpty(token))
+            {
+                _logger.LogInformation("No jwt token is found.");
+                return AuthenticateResult.NoResult();
+            }
+
+            var handler = new JwtSecurityTokenHandler();
+            try
+            {
+                var principal = handler.ValidateToken(token, Options.TokenValidationParameters, out var validatedToken);
+                return AuthenticateResult.Success(new AuthenticationTicket(principal, AuthConstants.Scheme));
+            }
+            catch (SecurityTokenException e)
+            {
+                _logger.LogInformation(e, "A jwt token validation failed.");
+                return AuthenticateResult.Fail(e);
+            }
+            catch (Exception e)
+            {
+                _logger.LogError(e, "Arguments passed to the JwtSecurityTokenHandler.ValidateToken are bad.");
+                throw e;
+            }
+        }
+    }
+}