From 900bb5e845c3ad44defbd427cae3d44a4a43321f Mon Sep 17 00:00:00 2001
From: ivarlovlie <git@ivarlovlie.no>
Date: Sat, 25 Feb 2023 13:15:44 +0100
Subject: feat: Initial commit

---
 .../src/Utilities/BasicAuthenticationHandler.cs    | 79 ++++++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 code/api/src/Utilities/BasicAuthenticationHandler.cs

(limited to 'code/api/src/Utilities/BasicAuthenticationHandler.cs')

diff --git a/code/api/src/Utilities/BasicAuthenticationHandler.cs b/code/api/src/Utilities/BasicAuthenticationHandler.cs
new file mode 100644
index 0000000..b0a2d1a
--- /dev/null
+++ b/code/api/src/Utilities/BasicAuthenticationHandler.cs
@@ -0,0 +1,79 @@
+using System.Net.Http.Headers;
+using System.Text;
+using System.Text.Encodings.Web;
+using Microsoft.Extensions.Options;
+
+namespace IOL.GreatOffice.Api.Utilities;
+
+public class BasicAuthenticationHandler : AuthenticationHandler<AuthenticationSchemeOptions>
+{
+	private readonly MainAppDatabase _context;
+	private readonly AppConfiguration _configuration;
+	private readonly ILogger<BasicAuthenticationHandler> _logger;
+
+	public BasicAuthenticationHandler(
+			IOptionsMonitor<AuthenticationSchemeOptions> options,
+			ILoggerFactory logger,
+			UrlEncoder encoder,
+			ISystemClock clock,
+			MainAppDatabase context,
+			VaultService vaultService
+	) :
+			base(options, logger, encoder, clock) {
+		_context = context;
+		_configuration = vaultService.GetCurrentAppConfiguration();
+		_logger = logger.CreateLogger<BasicAuthenticationHandler>();
+	}
+
+	protected override Task<AuthenticateResult> HandleAuthenticateAsync() {
+		var endpoint = Context.GetEndpoint();
+		if (endpoint?.Metadata.GetMetadata<IAllowAnonymous>() != null)
+			return Task.FromResult(AuthenticateResult.NoResult());
+
+		if (!Request.Headers.ContainsKey("Authorization"))
+			return Task.FromResult(AuthenticateResult.Fail("Missing Authorization Header"));
+
+		try {
+			var tokenEntropy = _configuration.APP_AES_KEY;
+			if (tokenEntropy.IsNullOrWhiteSpace()) {
+				_logger.LogWarning("No token entropy is available in env:TOKEN_ENTROPY, Basic auth is disabled");
+				return Task.FromResult(AuthenticateResult.Fail("Invalid Authorization Header"));
+			}
+
+			var authHeader = AuthenticationHeaderValue.Parse(Request.Headers["Authorization"]);
+			if (authHeader.Parameter == null) return Task.FromResult(AuthenticateResult.Fail("Invalid Authorization Header"));
+			var credentialBytes = Convert.FromBase64String(authHeader.Parameter);
+			var decryptedString = Encoding.UTF8.GetString(credentialBytes).DecryptWithAes(tokenEntropy);
+			var tokenIsGuid = Guid.TryParse(decryptedString, out var tokenId);
+
+			if (!tokenIsGuid) {
+				return Task.FromResult(AuthenticateResult.Fail("Invalid Authorization Header"));
+			}
+
+			var token = _context.AccessTokens.Include(c => c.User).SingleOrDefault(c => c.Id == tokenId);
+			if (token == default) {
+				return Task.FromResult(AuthenticateResult.Fail("Invalid Authorization Header: Not Found"));
+			}
+
+			if (token.HasExpired) {
+				return Task.FromResult(AuthenticateResult.Fail("Invalid Authorization Header: Expired"));
+			}
+
+			var permissions = new List<Claim>() {
+					new(AppConstants.TOKEN_ALLOW_READ, token.AllowRead.ToString()),
+					new(AppConstants.TOKEN_ALLOW_UPDATE, token.AllowUpdate.ToString()),
+					new(AppConstants.TOKEN_ALLOW_CREATE, token.AllowCreate.ToString()),
+					new(AppConstants.TOKEN_ALLOW_DELETE, token.AllowDelete.ToString()),
+			};
+			var claims = token.User.DefaultClaims().Concat(permissions);
+			var identity = new ClaimsIdentity(claims, AppConstants.BASIC_AUTH_SCHEME);
+			var principal = new ClaimsPrincipal(identity);
+			var ticket = new AuthenticationTicket(principal, AppConstants.BASIC_AUTH_SCHEME);
+
+			return Task.FromResult(AuthenticateResult.Success(ticket));
+		} catch (Exception e) {
+			_logger.LogError(e, $"An exception occured when challenging {AppConstants.BASIC_AUTH_SCHEME}");
+			return Task.FromResult(AuthenticateResult.Fail("Invalid Authorization Header"));
+		}
+	}
+}
-- 
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