feat(auth): LDAP login — authenticate imported users against the directory

LDAP-imported users have no local passwordHash, and validateUser only checked
the local password, so they could never log in. Now a passwordless user with
an ldapDn is authenticated by binding as their OWN DN with the entered
password against the tenant's active LDAP config (reusing the ldaps TLS-skip
option). Empty passwords are rejected before binding to avoid AD's
unauthenticated-bind bypass. Local-password users are unchanged.

LdapService.verifyUserCredentials added; LdapModule now exports
LdapConfigService; AuthModule imports LdapModule (no circular dep). 8 new
specs (bind success/fail, empty-password guard, login via bind, wrong pw, no
config, no ldapDn, inactive). API 226 green, tsc clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/api/src/auth/auth.module.ts

@@ -2,6 +2,7 @@ import { Module } from '@nestjs/common';
 import { ConfigService } from '@nestjs/config';
 import { JwtModule } from '@nestjs/jwt';
 import { PassportModule } from '@nestjs/passport';
+import { LdapModule } from '../ldap/ldap.module';
 import { MailModule } from '../mail/mail.module';
 import { AuthController } from './auth.controller';
 import { AuthService } from './auth.service';
@@ -19,6 +20,7 @@ import { LocalStrategy } from './strategies/local.strategy';
       inject: [ConfigService],
     }),
     MailModule,
+    LdapModule,
   ],
   controllers: [AuthController],
   providers: [AuthService, LocalStrategy, JwtStrategy],

apps/api/src/auth/auth.service.spec.ts

@@ -0,0 +1,109 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { AuthService } from './auth.service';
+
+/**
+ * validateUser — LDAP login path (AUTH-06 follow-up): users imported from LDAP
+ * have no local passwordHash and must be authenticated by binding as their own
+ * DN against the tenant's directory. These tests cover that branch; the local
+ * password path (argon2) is unchanged and exercised elsewhere.
+ */
+describe('AuthService.validateUser — LDAP login', () => {
+  let service: AuthService;
+  let prisma: any;
+  let ldapService: any;
+  let ldapConfigService: any;
+
+  const ldapUser = {
+    id: 'u1',
+    tenantId: 't1',
+    username: 'alice',
+    passwordHash: null,
+    ldapDn: 'CN=alice,OU=Users,DC=ctl,DC=local',
+    isActive: true,
+  };
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    prisma = {
+      user: {
+        findUnique: vi.fn().mockResolvedValue(ldapUser),
+        update: vi.fn().mockResolvedValue({}),
+      },
+    };
+    ldapService = { verifyUserCredentials: vi.fn() };
+    ldapConfigService = {
+      getConfig: vi.fn().mockResolvedValue({
+        serverUrl: 'ldaps://balios.ctl.local:636',
+        isActive: true,
+        tlsRejectUnauthorized: false,
+      }),
+    };
+    service = new AuthService(
+      prisma,
+      {} as any,
+      {} as any,
+      {} as any,
+      ldapService,
+      ldapConfigService,
+    );
+  });
+
+  it('authenticates an LDAP user via a successful directory bind', async () => {
+    ldapService.verifyUserCredentials.mockResolvedValue(true);
+
+    const result = await service.validateUser('Alice', 'ad-password');
+
+    expect(result).toEqual(ldapUser);
+    expect(ldapService.verifyUserCredentials).toHaveBeenCalledWith(
+      {
+        serverUrl: 'ldaps://balios.ctl.local:636',
+        tlsRejectUnauthorized: false,
+      },
+      ldapUser.ldapDn,
+      'ad-password',
+    );
+    expect(prisma.user.update).toHaveBeenCalledWith({
+      where: { id: 'u1' },
+      data: { lastLoginAt: expect.any(Date) },
+    });
+  });
+
+  it('rejects an LDAP user when the directory bind fails', async () => {
+    ldapService.verifyUserCredentials.mockResolvedValue(false);
+
+    const result = await service.validateUser('alice', 'wrong');
+
+    expect(result).toBeNull();
+    expect(prisma.user.update).not.toHaveBeenCalled();
+  });
+
+  it('rejects an LDAP user when no active LDAP config exists', async () => {
+    ldapConfigService.getConfig.mockResolvedValue(null);
+
+    const result = await service.validateUser('alice', 'pw');
+
+    expect(result).toBeNull();
+    expect(ldapService.verifyUserCredentials).not.toHaveBeenCalled();
+  });
+
+  it('rejects a passwordless user that has no ldapDn (never binds)', async () => {
+    prisma.user.findUnique.mockResolvedValue({
+      ...ldapUser,
+      ldapDn: null,
+    });
+
+    const result = await service.validateUser('alice', 'pw');
+
+    expect(result).toBeNull();
+    expect(ldapService.verifyUserCredentials).not.toHaveBeenCalled();
+  });
+
+  it('rejects an inactive LDAP user before any bind', async () => {
+    prisma.user.findUnique.mockResolvedValue({ ...ldapUser, isActive: false });
+
+    const result = await service.validateUser('alice', 'pw');
+
+    expect(result).toBeNull();
+    expect(ldapService.verifyUserCredentials).not.toHaveBeenCalled();
+  });
+});

apps/api/src/auth/auth.service.ts

@@ -9,6 +9,8 @@ import { JwtService } from '@nestjs/jwt';
 import * as argon2 from 'argon2';
 import { randomUUID } from 'crypto';
 import { Response } from 'express';
+import { LdapConfigService } from '../ldap/ldap-config.service';
+import { LdapService } from '../ldap/ldap.service';
 import { MailService } from '../mail/mail.service';
 import { PrismaService } from '../prisma/prisma.service';
 
@@ -21,6 +23,8 @@ export class AuthService {
     private jwtService: JwtService,
     private configService: ConfigService,
     private mailService: MailService,
+    private ldapService: LdapService,
+    private ldapConfigService: LdapConfigService,
   ) {}
 
   /**
@@ -40,9 +44,35 @@ export class AuthService {
       return null;
     }
 
-    // LDAP users without local password cannot log in via local auth
+    // LDAP users have no local password — authenticate them against the
+    // directory by binding as their OWN DN with the password they entered.
     if (!user.passwordHash) {
-      return null;
+      if (!user.ldapDn) {
+        return null;
+      }
+
+      const config = await this.ldapConfigService.getConfig(user.tenantId);
+      if (!config || !config.isActive) {
+        return null;
+      }
+
+      const ok = await this.ldapService.verifyUserCredentials(
+        {
+          serverUrl: config.serverUrl,
+          tlsRejectUnauthorized: config.tlsRejectUnauthorized,
+        },
+        user.ldapDn,
+        password,
+      );
+      if (!ok) {
+        return null;
+      }
+
+      await this.prisma.user.update({
+        where: { id: user.id },
+        data: { lastLoginAt: new Date() },
+      });
+      return user;
     }
 
     const isPasswordValid = await argon2.verify(user.passwordHash, password);

apps/api/src/ldap/ldap.module.ts

@@ -16,6 +16,6 @@ import { LdapService } from './ldap.service';
   imports: [ScheduleModule.forRoot(), UserModule],
   controllers: [LdapController],
   providers: [LdapService, LdapConfigService, LdapSyncScheduler],
-  exports: [LdapService],
+  exports: [LdapService, LdapConfigService],
 })
 export class LdapModule {}

apps/api/src/ldap/ldap.service.spec.ts

@@ -308,3 +308,44 @@ describe('LdapService.testConnection — TLS verification opt-out (ldaps)', () =
     expect(opts.tlsOptions).toBeUndefined();
   });
 });
+
+describe('LdapService.verifyUserCredentials — LDAP login bind', () => {
+  let service: LdapService;
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    mockUnbind.mockResolvedValue(undefined);
+    service = new LdapService({} as any, {} as any);
+  });
+
+  it('returns true when the user bind succeeds', async () => {
+    mockBind.mockResolvedValue(undefined);
+    const ok = await service.verifyUserCredentials(
+      { serverUrl: 'ldaps://ad:636', tlsRejectUnauthorized: false },
+      'CN=alice,DC=x',
+      'correct-pw',
+    );
+    expect(ok).toBe(true);
+    expect(mockBind).toHaveBeenCalledWith('CN=alice,DC=x', 'correct-pw');
+  });
+
+  it('returns false when the user bind fails (wrong password)', async () => {
+    mockBind.mockRejectedValue(new Error('invalid credentials'));
+    const ok = await service.verifyUserCredentials(
+      { serverUrl: 'ldaps://ad:636' },
+      'CN=alice,DC=x',
+      'wrong-pw',
+    );
+    expect(ok).toBe(false);
+  });
+
+  it('rejects an empty password WITHOUT binding (no anonymous-bind bypass)', async () => {
+    const ok = await service.verifyUserCredentials(
+      { serverUrl: 'ldaps://ad:636' },
+      'CN=alice,DC=x',
+      '',
+    );
+    expect(ok).toBe(false);
+    expect(mockBind).not.toHaveBeenCalled();
+  });
+});

apps/api/src/ldap/ldap.service.ts

@@ -152,6 +152,41 @@ export class LdapService {
     }
   }
 
+  /**
+   * Authenticate a user for LOGIN by binding as their OWN DN with the password
+   * they entered (distinct from the service-account bind used for sync/search).
+   * Returns true only on a successful authenticated bind.
+   *
+   * SECURITY: an empty password is rejected up front — many AD servers treat a
+   * bind with a DN and empty password as an unauthenticated/anonymous bind that
+   * "succeeds", which would let anyone log in as any LDAP user. Never allow it.
+   */
+  async verifyUserCredentials(
+    config: { serverUrl: string; tlsRejectUnauthorized?: boolean | null },
+    userDn: string,
+    password: string,
+  ): Promise<boolean> {
+    if (!userDn || !password) {
+      return false;
+    }
+
+    const client = new Client(
+      this.buildClientOptions(config.serverUrl, config.tlsRejectUnauthorized),
+    );
+    try {
+      await client.bind(userDn, password);
+      return true;
+    } catch {
+      return false;
+    } finally {
+      try {
+        await client.unbind();
+      } catch {
+        // Ignore unbind errors
+      }
+    }
+  }
+
   /**
    * Discover groups and organizational units under the configured base DN.
    * Used by the admin UI to build a selective import filter (groupFilterDns).