aspnetcore/src/Microsoft.AspNet.Antiforgery/DefaultAntiforgeryTokenGenerator.cs

// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Diagnostics;
using System.Security.Claims;
using System.Security.Principal;
using Microsoft.AspNet.Http;

namespace Microsoft.AspNet.Antiforgery
{
    public class DefaultAntiforgeryTokenGenerator : IAntiforgeryTokenGenerator
    {
        private readonly IClaimUidExtractor _claimUidExtractor;
        private readonly IAntiforgeryAdditionalDataProvider _additionalDataProvider;

        public DefaultAntiforgeryTokenGenerator(
            IClaimUidExtractor claimUidExtractor,
            IAntiforgeryAdditionalDataProvider additionalDataProvider)
        {
            _claimUidExtractor = claimUidExtractor;
            _additionalDataProvider = additionalDataProvider;
        }

        public AntiforgeryToken GenerateCookieToken()
        {
            return new AntiforgeryToken()
            {
                // SecurityToken will be populated automatically.
                IsCookieToken = true
            };
        }

        public AntiforgeryToken GenerateRequestToken(
            HttpContext httpContext,
            AntiforgeryToken cookieToken)
        {
            if (httpContext == null)
            {
                throw new ArgumentNullException(nameof(httpContext));
            }

            Debug.Assert(IsCookieTokenValid(cookieToken));

            var requestToken = new AntiforgeryToken()
            {
                SecurityToken = cookieToken.SecurityToken,
                IsCookieToken = false
            };

            var isIdentityAuthenticated = false;
            var identity = httpContext.User?.Identity as ClaimsIdentity;

            // populate Username and ClaimUid
            if (identity != null && identity.IsAuthenticated)
            {
                isIdentityAuthenticated = true;
                requestToken.ClaimUid = GetClaimUidBlob(_claimUidExtractor.ExtractClaimUid(identity));
                if (requestToken.ClaimUid == null)
                {
                    requestToken.Username = identity.Name;
                }
            }

            // populate AdditionalData
            if (_additionalDataProvider != null)
            {
                requestToken.AdditionalData = _additionalDataProvider.GetAdditionalData(httpContext);
            }

            if (isIdentityAuthenticated
                && string.IsNullOrEmpty(requestToken.Username)
                && requestToken.ClaimUid == null
                && string.IsNullOrEmpty(requestToken.AdditionalData))
            {
                // Application says user is authenticated, but we have no identifier for the user.
                throw new InvalidOperationException(
                    Resources.FormatAntiforgeryTokenValidator_AuthenticatedUserWithoutUsername(
                        identity.GetType(),
                        nameof(IIdentity.IsAuthenticated),
                        "true",
                        nameof(IIdentity.Name),
                        nameof(IAntiforgeryAdditionalDataProvider),
                        nameof(DefaultAntiforgeryAdditionalDataProvider)));
            }

            return requestToken;
        }

        public bool IsCookieTokenValid(AntiforgeryToken cookieToken)
        {
            return (cookieToken != null && cookieToken.IsCookieToken);
        }

        public void ValidateTokens(
            HttpContext httpContext,
            AntiforgeryToken cookieToken,
            AntiforgeryToken requestToken)
        {
            if (httpContext == null)
            {
                throw new ArgumentNullException(nameof(httpContext));
            }

            if (cookieToken == null)
            {
                throw new ArgumentNullException(
                    nameof(cookieToken),
                    Resources.Antiforgery_CookieToken_MustBeProvided_Generic);
            }

            if (requestToken == null)
            {
                throw new ArgumentNullException(
                    nameof(requestToken),
                    Resources.Antiforgery_RequestToken_MustBeProvided_Generic);
            }

            // Do the tokens have the correct format?
            if (!cookieToken.IsCookieToken || requestToken.IsCookieToken)
            {
                throw new InvalidOperationException(Resources.AntiforgeryToken_TokensSwapped);
            }

            // Are the security tokens embedded in each incoming token identical?
            if (!object.Equals(cookieToken.SecurityToken, requestToken.SecurityToken))
            {
                throw new InvalidOperationException(Resources.AntiforgeryToken_SecurityTokenMismatch);
            }

            // Is the incoming token meant for the current user?
            var currentUsername = string.Empty;
            BinaryBlob currentClaimUid = null;

            var identity = httpContext.User?.Identity as ClaimsIdentity;
            if (identity != null && identity.IsAuthenticated)
            {
                currentClaimUid = GetClaimUidBlob(_claimUidExtractor.ExtractClaimUid(identity));
                if (currentClaimUid == null)
                {
                    currentUsername = identity.Name ?? string.Empty;
                }
            }

            // OpenID and other similar authentication schemes use URIs for the username.
            // These should be treated as case-sensitive.
            var comparer = StringComparer.OrdinalIgnoreCase;
            if (currentUsername.StartsWith("http://", StringComparison.OrdinalIgnoreCase) ||
                currentUsername.StartsWith("https://", StringComparison.OrdinalIgnoreCase))
            {
                comparer = StringComparer.Ordinal;
            }

            if (!comparer.Equals(requestToken.Username, currentUsername))
            {
                throw new InvalidOperationException(
                    Resources.FormatAntiforgeryToken_UsernameMismatch(requestToken.Username, currentUsername));
            }

            if (!Equals(requestToken.ClaimUid, currentClaimUid))
            {
                throw new InvalidOperationException(Resources.AntiforgeryToken_ClaimUidMismatch);
            }

            // Is the AdditionalData valid?
            if (_additionalDataProvider != null &&
                !_additionalDataProvider.ValidateAdditionalData(httpContext, requestToken.AdditionalData))
            {
                throw new InvalidOperationException(Resources.AntiforgeryToken_AdditionalDataCheckFailed);
            }
        }

        private static BinaryBlob GetClaimUidBlob(string base64ClaimUid)
        {
            if (base64ClaimUid == null)
            {
                return null;
            }

            return new BinaryBlob(256, Convert.FromBase64String(base64ClaimUid));
        }
    }
}