Files
jobtrackingapp/JobTrackerApi/Services/MicrosoftTokenValidator.cs
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feat(auth): Microsoft OAuth sign-in/link + self-serve signup via Google/Microsoft
Wave 7. Mirrors the existing Google ID-token-exchange pattern (Program.cs
smart-scheme dispatch, JWT bearer scheme, AuthController exchange/link/
unlink endpoints, ApplicationUser fields, reconciler columns) for
Microsoft Entra ID + personal accounts via the multi-tenant "common"
endpoint.

Google/Microsoft sign-in previously only worked for accounts already
linked to an existing local user -- there was no way to actually sign
up via OAuth. Both exchange endpoints now create a new user when no
match is found and Auth:AllowRegistration is true, same gate as
email/password registration.

Frontend: new MicrosoftAuthCard (MSAL popup flow -- Microsoft has no
vanilla-JS equivalent to Google's Identity Services script) wired into
the login page's provider tabs and the profile page's account-linking
section. REACT_APP_MICROSOFT_CLIENT_ID env var, Auth:MicrosoftClientId
config gate on the backend.
2026-07-12 00:12:23 +02:00

101 lines
4.5 KiB
C#

using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using Microsoft.IdentityModel.Protocols;
using Microsoft.IdentityModel.Protocols.OpenIdConnect;
using Microsoft.IdentityModel.Tokens;
namespace JobTrackerApi.Services;
public sealed record MicrosoftTokenPrincipal(string Subject, string? Email, bool EmailVerified, string? GivenName, string? FamilyName, string? Name);
public interface IMicrosoftTokenValidator
{
Task<MicrosoftTokenPrincipal> ValidateAsync(string idToken, CancellationToken cancellationToken = default);
}
public sealed class MicrosoftTokenValidator : IMicrosoftTokenValidator
{
private readonly IConfiguration _cfg;
private readonly IConfigurationManager<OpenIdConnectConfiguration> _configManager;
public MicrosoftTokenValidator(IConfiguration cfg)
{
_cfg = cfg;
// "common" endpoint: accepts both personal Microsoft accounts and work/school (Entra ID) tenants.
_configManager = new ConfigurationManager<OpenIdConnectConfiguration>(
"https://login.microsoftonline.com/common/v2.0/.well-known/openid-configuration",
new OpenIdConnectConfigurationRetriever());
}
public MicrosoftTokenValidator(IConfiguration cfg, IConfigurationManager<OpenIdConnectConfiguration> configManager)
{
_cfg = cfg;
_configManager = configManager;
}
public async Task<MicrosoftTokenPrincipal> ValidateAsync(string idToken, CancellationToken cancellationToken = default)
{
var audience = (_cfg["Auth:MicrosoftClientId"] ?? "").Trim();
if (string.IsNullOrWhiteSpace(audience))
{
throw new InvalidOperationException("Microsoft sign-in is not configured.");
}
var config = await _configManager.GetConfigurationAsync(cancellationToken);
var handler = new JwtSecurityTokenHandler
{
// The handler's default inbound claim map rewrites "oid"/"tid" to long Microsoft
// schema URIs (an AAD-specific quirk not shared by Google's OIDC claims) -- keep
// claim names as issued so FindFirst("oid") below actually matches.
MapInboundClaims = false,
};
// ponytail: multi-tenant "common" app -- each tenant's issuer embeds its own tenant id
// (https://login.microsoftonline.com/{tenantId}/v2.0), so issuer is checked by shape below
// rather than pinned to one value. Signature/audience/lifetime are still fully validated.
var principal = handler.ValidateToken(idToken, new TokenValidationParameters
{
ValidateIssuer = false,
ValidateAudience = true,
ValidAudience = audience,
ValidateLifetime = true,
ValidateIssuerSigningKey = true,
IssuerSigningKeys = config.SigningKeys,
ClockSkew = TimeSpan.FromMinutes(2),
}, out var validatedToken);
var issuer = (validatedToken as JwtSecurityToken)?.Issuer ?? principal.FindFirst("iss")?.Value ?? "";
if (!IsMicrosoftIssuer(issuer))
{
throw new InvalidOperationException("Microsoft token has an unexpected issuer.");
}
var subject = principal.FindFirst("oid")?.Value?.Trim()
?? principal.FindFirst(JwtRegisteredClaimNames.Sub)?.Value?.Trim()
?? principal.FindFirst(ClaimTypes.NameIdentifier)?.Value?.Trim();
if (string.IsNullOrWhiteSpace(subject))
{
throw new InvalidOperationException("Microsoft token is missing a subject.");
}
var email = principal.FindFirst("email")?.Value?.Trim()
?? principal.FindFirst(ClaimTypes.Email)?.Value?.Trim()
?? principal.FindFirst("preferred_username")?.Value?.Trim();
return new MicrosoftTokenPrincipal(
Subject: subject,
Email: email,
// Microsoft ID tokens don't carry an email_verified claim; presence of an email claim
// from a signature-validated token is treated as verified, same trust level Microsoft's
// own APIs give it.
EmailVerified: !string.IsNullOrWhiteSpace(email),
GivenName: principal.FindFirst("given_name")?.Value?.Trim(),
FamilyName: principal.FindFirst("family_name")?.Value?.Trim(),
Name: principal.FindFirst("name")?.Value?.Trim() ?? principal.Identity?.Name?.Trim()
);
}
private static bool IsMicrosoftIssuer(string issuer)
=> issuer.StartsWith("https://login.microsoftonline.com/", StringComparison.OrdinalIgnoreCase)
&& issuer.EndsWith("/v2.0", StringComparison.OrdinalIgnoreCase);
}