LoginAuthority.cs

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using System;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
 
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
 
using Tgstation.Server.Api;
using Tgstation.Server.Api.Models;
using Tgstation.Server.Api.Models.Response;
using Tgstation.Server.Host.Authority.Core;
using Tgstation.Server.Host.Database;
using Tgstation.Server.Host.GraphQL.Mutations.Payloads;
using Tgstation.Server.Host.Models;
using Tgstation.Server.Host.Models.Transformers;
using Tgstation.Server.Host.Security;
using Tgstation.Server.Host.Security.OAuth;
using Tgstation.Server.Host.Utils;
 
namespace Tgstation.Server.Host.Authority
{
    sealed class LoginAuthority : AuthorityBase, ILoginAuthority
    {
        readonly IApiHeadersProvider apiHeadersProvider;
 
        readonly ISystemIdentityFactory systemIdentityFactory;
 
        readonly IOAuthProviders oAuthProviders;
 
        readonly ITokenFactory tokenFactory;
 
        readonly ICryptographySuite cryptographySuite;
 
        readonly IIdentityCache identityCache;
 
        readonly ISessionInvalidationTracker sessionInvalidationTracker;
 
        static AuthorityResponse<TResult> GenerateHeadersExceptionResponse<TResult>(HeadersException headersException)
            => new(
                new ErrorMessageResponse(ErrorCode.BadHeaders)
                {
                    AdditionalData = headersException.Message,
                },
                headersException.ParseErrors.HasFlag(HeaderErrorTypes.Accept)
                    ? HttpFailureResponse.NotAcceptable
                    : HttpFailureResponse.BadRequest);
 
        static async ValueTask<User?> SelectUserInfoFromQuery(IQueryable<User> query, CancellationToken cancellationToken)
        {
            var users = await query
                .ToListAsync(cancellationToken);
 
            // Pick the DB user first
            var user = users
                .OrderByDescending(dbUser => dbUser.SystemIdentifier == null)
                .FirstOrDefault();
 
            return user;
        }
 
        public LoginAuthority(
            IAuthenticationContext authenticationContext,
            IDatabaseContext databaseContext,
            ILogger<LoginAuthority> logger,
            IApiHeadersProvider apiHeadersProvider,
            ISystemIdentityFactory systemIdentityFactory,
            IOAuthProviders oAuthProviders,
            ITokenFactory tokenFactory,
            ICryptographySuite cryptographySuite,
            IIdentityCache identityCache,
            ISessionInvalidationTracker sessionInvalidationTracker)
            : base(
                  authenticationContext,
                  databaseContext,
                  logger)
        {
            this.apiHeadersProvider = apiHeadersProvider ?? throw new ArgumentNullException(nameof(apiHeadersProvider));
            this.systemIdentityFactory = systemIdentityFactory ?? throw new ArgumentNullException(nameof(systemIdentityFactory));
            this.oAuthProviders = oAuthProviders ?? throw new ArgumentNullException(nameof(oAuthProviders));
            this.tokenFactory = tokenFactory ?? throw new ArgumentNullException(nameof(tokenFactory));
            this.cryptographySuite = cryptographySuite ?? throw new ArgumentNullException(nameof(cryptographySuite));
            this.identityCache = identityCache ?? throw new ArgumentNullException(nameof(identityCache));
            this.sessionInvalidationTracker = sessionInvalidationTracker ?? throw new ArgumentNullException(nameof(sessionInvalidationTracker));
        }
 
        public async ValueTask<AuthorityResponse<LoginResult>> AttemptLogin(CancellationToken cancellationToken)
        {
            var headers = apiHeadersProvider.ApiHeaders;
            if (headers == null)
                return GenerateHeadersExceptionResponse<LoginResult>(apiHeadersProvider.HeadersException!);
 
            if (headers.IsTokenAuthentication)
                return BadRequest<LoginResult>(ErrorCode.TokenWithToken);
 
            var oAuthLogin = headers.OAuthProvider.HasValue;
 
            ISystemIdentity? systemIdentity = null;
            if (!oAuthLogin)
                try
                {
                    // trust the system over the database because a user's name can change while still having the same SID
                    systemIdentity = await systemIdentityFactory.CreateSystemIdentity(headers.Username!, headers.Password!, cancellationToken);
                }
                catch (NotImplementedException)
                {
                    // Intentionally suppressed
                }
 
            using (systemIdentity)
            {
                // Get the user from the database
                IQueryable<User> query = DatabaseContext.Users.AsQueryable();
                if (oAuthLogin)
                {
                    var oAuthProvider = headers.OAuthProvider!.Value;
                    var (errorResponse, oauthResult) = await TryOAuthenticate<LoginResult>(headers, oAuthProvider, true, cancellationToken);
                    if (errorResponse != null)
                        return errorResponse;
 
                    query = query.Where(
                        x => x.OAuthConnections!.Any(
                            y => y.Provider == oAuthProvider
                            && y.ExternalUserId == oauthResult!.Value.UserID));
                }
                else
                {
                    var canonicalUserName = User.CanonicalizeName(headers.Username!);
                    if (canonicalUserName == User.CanonicalizeName(User.TgsSystemUserName))
                        return Unauthorized<LoginResult>();
 
                    if (systemIdentity == null)
                        query = query.Where(x => x.CanonicalName == canonicalUserName);
                    else
                        query = query.Where(x => x.CanonicalName == canonicalUserName || x.SystemIdentifier == systemIdentity.Uid);
                }
 
                var user = await SelectUserInfoFromQuery(query, cancellationToken);
 
                // No user? You're not allowed
                if (user == null)
                    return Unauthorized<LoginResult>();
 
                // A system user may have had their name AND password changed to one in our DB...
                // Or a DB user was created that had the same user/pass as a system user
                // Dumb admins...
                // FALLBACK TO THE DB USER HERE, DO NOT REVEAL A SYSTEM LOGIN!!!
                // This of course, allows system users to discover TGS users in this (HIGHLY IMPROBABLE) case but that is not our fault
                var originalHash = user.PasswordHash;
                var isLikelyDbUser = originalHash != null;
                var usingSystemIdentity = systemIdentity != null && !isLikelyDbUser;
                if (!oAuthLogin)
                    if (!usingSystemIdentity)
                    {
                        // DB User password check and update
                        if (!isLikelyDbUser || !cryptographySuite.CheckUserPassword(user, headers.Password!))
                            return Unauthorized<LoginResult>();
                        if (user.PasswordHash != originalHash)
                        {
                            Logger.LogDebug("User ID {userId}'s password hash needs a refresh, updating database.", user.Id);
                            var updatedUser = new User
                            {
                                Id = user.Id,
                            };
                            DatabaseContext.Users.Attach(updatedUser);
                            updatedUser.PasswordHash = user.PasswordHash;
                            await DatabaseContext.Save(cancellationToken);
                        }
                    }
                    else
                    {
                        var usernameMismatch = systemIdentity!.Username != user.Name;
                        if (isLikelyDbUser || usernameMismatch)
                        {
                            DatabaseContext.Users.Attach(user);
                            if (usernameMismatch)
                            {
                                // System identity username change update
                                Logger.LogDebug("User ID {userId}'s system identity needs a refresh, updating database.", user.Id);
                                user.Name = systemIdentity.Username;
                                user.CanonicalName = User.CanonicalizeName(user.Name);
                            }
 
                            if (isLikelyDbUser)
                            {
                                // cleanup from https://github.com/tgstation/tgstation-server/issues/1528
                                Logger.LogDebug("System user ID {userId}'s PasswordHash is polluted, updating database.", user.Id);
                                user.PasswordHash = null;
                                sessionInvalidationTracker.UserModifiedInvalidateSessions(user);
                            }
 
                            await DatabaseContext.Save(cancellationToken);
                        }
                    }
 
                // Now that the bookeeping is done, tell them to fuck off if necessary
                if (!user.Enabled!.Value)
                {
                    Logger.LogTrace("Not logging in disabled user {userId}.", user.Id);
                    return Forbid<LoginResult>();
                }
 
                var token = tokenFactory.CreateToken(user, oAuthLogin);
                var payload = new LoginResult
                {
                    Bearer = token,
                    User = ((IApiTransformable<User, GraphQL.Types.User, UserGraphQLTransformer>)user).ToApi(),
                };
 
                if (usingSystemIdentity)
                    await CacheSystemIdentity(systemIdentity!, user, payload);
 
                Logger.LogDebug("Successfully logged in user {userId}!", user.Id);
 
                return new AuthorityResponse<LoginResult>(payload);
            }
        }
 
        public async ValueTask<AuthorityResponse<OAuthGatewayLoginResult>> AttemptOAuthGatewayLogin(CancellationToken cancellationToken)
        {
            var headers = apiHeadersProvider.ApiHeaders;
            if (headers == null)
                return GenerateHeadersExceptionResponse<OAuthGatewayLoginResult>(apiHeadersProvider.HeadersException!);
 
            var oAuthProvider = headers.OAuthProvider;
            if (!oAuthProvider.HasValue)
                return BadRequest<OAuthGatewayLoginResult>(ErrorCode.BadHeaders);
 
            var (errorResponse, oAuthResult) = await TryOAuthenticate<OAuthGatewayLoginResult>(headers, oAuthProvider.Value, false, cancellationToken);
            if (errorResponse != null)
                return errorResponse;
 
            Logger.LogDebug("Generated {provider} OAuth AccessCode", oAuthProvider.Value);
 
            return new AuthorityResponse<OAuthGatewayLoginResult>(
                new OAuthGatewayLoginResult
                {
                    AccessCode = oAuthResult!.Value.AccessCode,
                });
        }
 
        private async ValueTask CacheSystemIdentity(ISystemIdentity systemIdentity, User user, LoginResult loginPayload)
        {
            // expire the identity slightly after the auth token in case of lag
            var identExpiry = loginPayload.ToApi().ParseJwt().ValidTo;
            identExpiry += tokenFactory.ValidationParameters.ClockSkew;
            identExpiry += TimeSpan.FromSeconds(15);
            await identityCache.CacheSystemIdentity(user, systemIdentity!, identExpiry);
        }
 
        async ValueTask<(AuthorityResponse<TResult>? ErrorResponse, (string? UserID, string AccessCode)? OAuthResult)> TryOAuthenticate<TResult>(ApiHeaders headers, OAuthProvider oAuthProvider, bool forLogin, CancellationToken cancellationToken)
        {
            (string? UserID, string AccessCode)? oauthResult;
            try
            {
                var validator = oAuthProviders
                    .GetValidator(oAuthProvider, forLogin);
 
                if (validator == null)
                    return (BadRequest<TResult>(ErrorCode.OAuthProviderDisabled), null);
                oauthResult = await validator
                    .ValidateResponseCode(headers.OAuthCode!, forLogin, cancellationToken);
 
                Logger.LogTrace("External {oAuthProvider} UID: {externalUserId}", oAuthProvider, oauthResult);
            }
            catch (Octokit.RateLimitExceededException ex)
            {
                return (RateLimit<TResult>(ex), null);
            }
 
            if (!oauthResult.HasValue)
                return (Unauthorized<TResult>(), null);
 
            return (null, OAuthResult: oauthResult);
        }
    }
}