ersatztv/ErsatzTV/Controllers/Api/AuthController.cs

using System.Security.Claims;
using ErsatzTV.Application.Auth;
using ErsatzTV.Controllers.Api.Requests;
using ErsatzTV.Core;
using ErsatzTV.Extensions;
using ErsatzTV.Filters;
using MediatR;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.RateLimiting;

namespace ErsatzTV.Controllers.Api;

/// <summary>
///     Browser SPA session authentication (issue #295). Excluded from the OpenAPI document — the spec's
///     audience is machine <c>X-Api-Key</c> clients, and a browser-interactive cookie login is not something a
///     generated client drives — and exempt from the global <see cref="ApiAuthorizationFilter" /> (this surface
///     must be reachable before a caller has a session). Sensitive operations self-check the principal.
/// </summary>
[ApiController]
[ApiExplorerSettings(IgnoreApi = true)]
[SkipApiAuthorization]
public class AuthController(IMediator mediator, IConfiguration configuration) : ControllerBase
{
    // When the operator has set an env seed, the local admin is managed via configuration — the browser
    // setup-claim is closed. This also eliminates the startup race where an attacker could claim admin in the
    // window before LocalAdminSeedService runs (the seed would then lose and its insert be swallowed).
    private bool EnvSeedConfigured => !string.IsNullOrWhiteSpace(configuration["Auth:LocalAdmin:Password"]);

    /// <summary>Public: what auth options exist + whether first-run setup is still needed (drives the SPA boot gate).</summary>
    [HttpGet("/api/auth/config")]
    public async Task<IActionResult> Config(CancellationToken cancellationToken)
    {
        bool configured = await mediator.Send(new IsLocalAdminConfigured(), cancellationToken);
        return Ok(new AuthConfigResponse(OidcHelper.IsEnabled, true, !configured && !EnvSeedConfigured));
    }

    /// <summary>The current session (anonymous is a 200 with authenticated=false, never a 401).</summary>
    [HttpGet("/api/auth/session")]
    public IActionResult Session()
    {
        if (User.Identity?.IsAuthenticated != true)
        {
            return Ok(new AuthSessionResponse(false, null, null));
        }

        return Ok(new AuthSessionResponse(true, User.Identity?.Name, User.FindFirst(AuthConstants.AuthMethodClaim)?.Value));
    }

    /// <summary>First-run setup-claim: create the local admin. Fails 409 if one already exists.</summary>
    [HttpPost("/api/auth/setup")]
    [EnableRateLimiting("auth")]
    public async Task<IActionResult> Setup([FromBody] SetupRequest request, CancellationToken cancellationToken)
    {
        if (EnvSeedConfigured)
        {
            return ApiResults.ConflictProblem(
                "Managed via configuration",
                "The local administrator is provisioned from Auth:LocalAdmin:* configuration; browser setup is disabled.");
        }

        if (await mediator.Send(new IsLocalAdminConfigured(), cancellationToken))
        {
            return ApiResults.ConflictProblem("Already configured", "A local administrator already exists.");
        }

        Either<BaseError, LocalAdminPrincipal> result =
            await mediator.Send(new ClaimLocalAdmin(request.Username, request.Password), cancellationToken);

        return await result.Match(
            Left: async error =>
            {
                // A concurrent claim that lost the race reports 409 (the record now exists), not the 422 a
                // validation error gets.
                if (await mediator.Send(new IsLocalAdminConfigured(), cancellationToken))
                {
                    return ApiResults.ConflictProblem("Already configured", "A local administrator already exists.");
                }

                return error.ToErrorResult();
            },
            Right: async principal =>
            {
                await IssueLocalCookieAsync(principal);
                return (IActionResult)Ok(new AuthSessionResponse(true, principal.Username, AuthConstants.MethodLocal));
            });
    }

    /// <summary>Local username/password login. A generic 401 on any failure (no username enumeration).</summary>
    [HttpPost("/api/auth/login")]
    [EnableRateLimiting("auth")]
    public async Task<IActionResult> Login([FromBody] LoginRequest request, CancellationToken cancellationToken)
    {
        Either<BaseError, LocalAdminPrincipal> result =
            await mediator.Send(new VerifyLocalAdminLogin(request.Username, request.Password), cancellationToken);

        return await result.Match(
            Left: _ => Task.FromResult((IActionResult)Unauthorized(new ProblemDetails
            {
                Status = StatusCodes.Status401Unauthorized,
                Title = "Unauthorized",
                Detail = "Invalid username or password."
            })),
            Right: async principal =>
            {
                await IssueLocalCookieAsync(principal);
                return (IActionResult)Ok(new AuthSessionResponse(true, principal.Username, AuthConstants.MethodLocal));
            });
    }

    /// <summary>
    ///     Sign out of the cookie session. Requires the CSRF header (this controller is filter-exempt). For a
    ///     local session this rotates the security stamp, ending the session <b>server-side</b> (a captured
    ///     cookie can't be replayed after logout) — which, for the single local admin, revokes all local
    ///     sessions ("log out everywhere"). Gated on an authenticated session so an unauthenticated caller
    ///     can't force-revoke the admin.
    /// </summary>
    [HttpPost("/api/auth/logout")]
    public async Task<IActionResult> Logout(CancellationToken cancellationToken)
    {
        // Prevent forced-logout CSRF: a same-site form POST carries the Lax cookie but can't set a custom
        // header. The whole controller is [SkipApiAuthorization], so the filter's CSRF check doesn't apply.
        if (RequiresCsrf(out IActionResult csrfError))
        {
            return csrfError;
        }

        if (User.Identity?.IsAuthenticated == true &&
            string.Equals(
                User.FindFirst(AuthConstants.AuthMethodClaim)?.Value,
                AuthConstants.MethodLocal,
                StringComparison.Ordinal))
        {
            await mediator.Send(new RotateLocalAdminSecurityStamp(), cancellationToken);
        }

        await HttpContext.SignOutAsync(AuthConstants.CookieScheme);
        return NoContent();
    }

    /// <summary>Change the local admin password (requires a local-login session); rotates the stamp, revoking other sessions.</summary>
    [HttpPost("/api/auth/password")]
    [EnableRateLimiting("auth")]
    public async Task<IActionResult> ChangePassword([FromBody] ChangePasswordRequest request, CancellationToken cancellationToken)
    {
        // Filter-exempt controller, so apply the session-mutation CSRF check here explicitly.
        if (RequiresCsrf(out IActionResult csrfError))
        {
            return csrfError;
        }

        // A machine key must not be able to rotate the local admin's password — require a local session.
        if (User.Identity?.IsAuthenticated != true ||
            !string.Equals(
                User.FindFirst(AuthConstants.AuthMethodClaim)?.Value,
                AuthConstants.MethodLocal,
                StringComparison.Ordinal))
        {
            return Unauthorized(new ProblemDetails
            {
                Status = StatusCodes.Status401Unauthorized,
                Title = "Unauthorized",
                Detail = "A local-login session is required to change the password."
            });
        }

        Either<BaseError, LocalAdminPrincipal> result = await mediator.Send(
            new ChangeLocalAdminPassword(User.Identity?.Name, request.CurrentPassword, request.NewPassword),
            cancellationToken);

        return await result.Match(
            Left: error => Task.FromResult(error.ToErrorResult()),
            Right: async principal =>
            {
                // Re-issue the cookie with the rotated stamp so THIS session survives while others are revoked.
                await IssueLocalCookieAsync(principal);
                return (IActionResult)NoContent();
            });
    }

    /// <summary>Browser-navigation OIDC challenge. Outside <c>/api</c> (a top-level GET redirect). 404 when OIDC is off.</summary>
    [HttpGet("/auth/oidc/login")]
    public IActionResult OidcLogin()
    {
        if (!OidcHelper.IsEnabled)
        {
            return NotFound();
        }

        return Challenge(
            new AuthenticationProperties { RedirectUri = $"{Request.PathBase}/app" },
            AuthConstants.OidcScheme);
    }

    // Session-mutation CSRF gate for the [SkipApiAuthorization] auth surface (the global filter doesn't see
    // it). Presence-only: a custom header can't be set by a cross-site form/navigation. Returns true (with a
    // 403 result) when the header is missing.
    private bool RequiresCsrf(out IActionResult error)
    {
        if (Request.Headers.ContainsKey(ApiAuthorizationFilter.CsrfHeaderName))
        {
            error = null;
            return false;
        }

        error = new ObjectResult(new ProblemDetails
        {
            Status = StatusCodes.Status403Forbidden,
            Title = "Forbidden",
            Detail = $"This request requires the '{ApiAuthorizationFilter.CsrfHeaderName}' header."
        })
        {
            StatusCode = StatusCodes.Status403Forbidden
        };
        return true;
    }

    private Task IssueLocalCookieAsync(LocalAdminPrincipal principal)
    {
        var claims = new List<Claim>
        {
            new(ClaimTypes.Name, principal.Username),
            new(AuthConstants.AuthMethodClaim, AuthConstants.MethodLocal),
            new(AuthConstants.SecurityStampClaim, principal.SecurityStamp)
        };
        var identity = new ClaimsIdentity(claims, AuthConstants.CookieScheme);
        return HttpContext.SignInAsync(AuthConstants.CookieScheme, new ClaimsPrincipal(identity));
    }
}

public record AuthConfigResponse(bool OidcEnabled, bool LocalLoginEnabled, bool SetupRequired);

public record AuthSessionResponse(bool Authenticated, string Username, string Method);