feat: add OIDC login with account linking

Add OpenID Connect as an alternative login method. Users can sign in
via an external identity provider (e.g., Authentik, Keycloak, Google).

- OIDC settings configured in admin UI (discovery URL, client ID/secret,
  redirect URI, button label, enable/disable toggle)
- PKCE-based authorization code flow with state and nonce validation
- Admin can manually link any user's OIDC identity (sub/issuer fields)
- Self-service linking: logged-in users can link/unlink their own account
- SSO button conditionally shown on login page when OIDC is enabled
- Username in header now clickable to open profile for all users
- Callback errors/success communicated via URL hash fragments

.env.example

@@ -5,3 +5,7 @@ SESSION_SECRET=replace-with-a-random-64-character-hex-string
 SESSION_MAX_AGE_HOURS=168   # default: 168 (7 days)
 PORT=3000
 DB_PATH=/app/data/check-printing.db
+
+# OIDC settings are configured in the admin UI (Manage Users > Single Sign-On).
+# No environment variables needed — discovery URL, client ID/secret, and
+# redirect URI are stored in the database settings table.

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "ezcheck",
-  "version": "0.1.0",
+  "version": "0.2.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "ezcheck",
-      "version": "0.1.0",
+      "version": "0.2.0",
       "dependencies": {
         "bcryptjs": "^3.0.3",
         "better-sqlite3": "^9.4.3",
@@ -14,6 +14,7 @@
         "express-session": "^1.19.0",
         "multer": "^2.1.1",
         "nodemailer": "^8.0.4",
+        "openid-client": "^5.7.1",
         "pdfkit": "^0.15.0"
       },
       "devDependencies": {
@@ -1391,6 +1392,15 @@
       "integrity": "sha512-xHjhDr3cNBK0BzdUJSPXZntQUx/mwMS5Rw4A7lPJ90XGAO6ISP/ePDNuo0vhqOZU+UD5JoodwCAAoZQd3FeAKw==",
       "license": "MIT"
     },
+    "node_modules/jose": {
+      "version": "4.15.9",
+      "resolved": "https://registry.npmjs.org/jose/-/jose-4.15.9.tgz",
+      "integrity": "sha512-1vUQX+IdDMVPj4k8kOxgUqlcK518yluMuGZwqlr44FS1ppZB/5GWh4rZG89erpOBOJjU/OBsnCVFfapsRz6nEA==",
+      "license": "MIT",
+      "funding": {
+        "url": "https://github.com/sponsors/panva"
+      }
+    },
     "node_modules/jpeg-exif": {
       "version": "1.1.4",
       "resolved": "https://registry.npmjs.org/jpeg-exif/-/jpeg-exif-1.1.4.tgz",
@@ -1417,6 +1427,18 @@
         "node": ">= 0.4"
       }
     },
+    "node_modules/lru-cache": {
+      "version": "6.0.0",
+      "resolved": "https://registry.npmjs.org/lru-cache/-/lru-cache-6.0.0.tgz",
+      "integrity": "sha512-Jo6dJ04CmSjuznwJSS3pUeWmd/H0ffTlkXXgwZi+eq1UCmqQwCh+eLsYOYCwY991i2Fah4h1BEMCx4qThGbsiA==",
+      "license": "ISC",
+      "dependencies": {
+        "yallist": "^4.0.0"
+      },
+      "engines": {
+        "node": ">=10"
+      }
+    },
     "node_modules/math-intrinsics": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/math-intrinsics/-/math-intrinsics-1.1.0.tgz",
@@ -1654,6 +1676,15 @@
         "node": ">=0.10.0"
       }
     },
+    "node_modules/object-hash": {
+      "version": "2.2.0",
+      "resolved": "https://registry.npmjs.org/object-hash/-/object-hash-2.2.0.tgz",
+      "integrity": "sha512-gScRMn0bS5fH+IuwyIFgnh9zBdo4DV+6GhygmWM9HyNJSgS0hScp1f5vjtm7oIIOiT9trXrShAkLFSc2IqKNgw==",
+      "license": "MIT",
+      "engines": {
+        "node": ">= 6"
+      }
+    },
     "node_modules/object-inspect": {
       "version": "1.13.4",
       "resolved": "https://registry.npmjs.org/object-inspect/-/object-inspect-1.13.4.tgz",
@@ -1711,6 +1742,15 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
+    "node_modules/oidc-token-hash": {
+      "version": "5.2.0",
+      "resolved": "https://registry.npmjs.org/oidc-token-hash/-/oidc-token-hash-5.2.0.tgz",
+      "integrity": "sha512-6gj2m8cJZ+iSW8bm0FXdGF0YhIQbKrfP4yWTNzxc31U6MOjfEmB1rHvlYvxI1B7t7BCi1F2vYTT6YhtQRG4hxw==",
+      "license": "MIT",
+      "engines": {
+        "node": "^10.13.0 || >=12.0.0"
+      }
+    },
     "node_modules/on-finished": {
       "version": "2.4.1",
       "resolved": "https://registry.npmjs.org/on-finished/-/on-finished-2.4.1.tgz",
@@ -1741,6 +1781,21 @@
         "wrappy": "1"
       }
     },
+    "node_modules/openid-client": {
+      "version": "5.7.1",
+      "resolved": "https://registry.npmjs.org/openid-client/-/openid-client-5.7.1.tgz",
+      "integrity": "sha512-jDBPgSVfTnkIh71Hg9pRvtJc6wTwqjRkN88+gCFtYWrlP4Yx2Dsrow8uPi3qLr/aeymPF3o2+dS+wOpglK04ew==",
+      "license": "MIT",
+      "dependencies": {
+        "jose": "^4.15.9",
+        "lru-cache": "^6.0.0",
+        "object-hash": "^2.2.0",
+        "oidc-token-hash": "^5.0.3"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/panva"
+      }
+    },
     "node_modules/pako": {
       "version": "0.2.9",
       "resolved": "https://registry.npmjs.org/pako/-/pako-0.2.9.tgz",
@@ -2542,6 +2597,12 @@
       "resolved": "https://registry.npmjs.org/wrappy/-/wrappy-1.0.2.tgz",
       "integrity": "sha512-l4Sp/DRseor9wL6EvV2+TuQn63dMkPjZ/sp9XkghTEbV9KlPS1xUsZ3u7/IQO4wxtcFB4bgpQPRcR3QCvezPcQ==",
       "license": "ISC"
+    },
+    "node_modules/yallist": {
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/yallist/-/yallist-4.0.0.tgz",
+      "integrity": "sha512-3wdGidZyq5PB084XLES5TpOSRA3wjXAlIWMhum2kRcv/41Sn2emQ0dycQW4uZXLejwKvg6EsvbdlVL+FYEct7A==",
+      "license": "ISC"
     }
   }
 }

package.json

@@ -15,6 +15,7 @@
     "express-session": "^1.19.0",
     "multer": "^2.1.1",
     "nodemailer": "^8.0.4",
+    "openid-client": "^5.7.1",
     "pdfkit": "^0.15.0"
   },
   "devDependencies": {

public/index.html

@@ -43,6 +43,10 @@
         </div>
         <div id="login-error" class="wizard-error" hidden></div>
         <button id="btn-login-submit" class="btn-primary" style="width:100%;margin-top:8px">Sign In</button>
+        <div id="oidc-login-section" hidden>
+          <div style="text-align:center;margin:12px 0 4px;color:var(--text-muted);font-size:12px">or</div>
+          <a id="btn-oidc-login" href="/api/auth/oidc/authorize" class="btn-secondary" style="width:100%;display:block;text-align:center;text-decoration:none">Sign in with SSO</a>
+        </div>
         <div style="text-align:center;margin-top:8px">
           <a href="#" id="link-forgot-password" style="font-size:12px;color:var(--text-muted)">Forgot password?</a>
         </div>
@@ -91,7 +95,7 @@
     <div class="header-right">
       <span class="header-info">Next check: <strong id="current-check-no">—</strong><button id="btn-set-check-no" class="btn-header-inline" title="Set next check number" data-admin-only>✎</button></span>
       <button id="btn-users" class="btn-header-icon" title="Manage users" data-admin-only hidden>👥</button>
-      <span id="header-username" class="header-username"></span>
+      <span id="header-username" class="header-username" style="cursor:pointer" title="Account settings"></span>
       <button id="btn-logout" class="btn-header-icon" title="Sign out">↩</button>
     </div>
   </header>
@@ -648,7 +652,7 @@
     </div>
     <div class="modal-body">
       <div id="users-list"></div>
-      <div style="margin-top:16px;border-top:1px solid var(--border);padding-top:16px">
+      <div id="user-form-section" style="margin-top:16px;border-top:1px solid var(--border);padding-top:16px">
         <h3 style="font-size:13px;font-weight:600;margin-bottom:10px" id="user-form-title">Add User</h3>
         <div class="form-row">
           <div class="form-group required">
@@ -676,6 +680,16 @@
           <label>Account Access <span class="field-hint">(admins see all — no selection needed)</span></label>
           <div id="uf-accounts-checkboxes" class="account-checkboxes"></div>
         </div>
+        <div id="uf-oidc-group" class="form-row" hidden>
+          <div class="form-group">
+            <label for="uf-oidc-sub">OIDC Subject <span class="field-hint">(sub claim from provider)</span></label>
+            <input type="text" id="uf-oidc-sub" autocomplete="off">
+          </div>
+          <div class="form-group">
+            <label for="uf-oidc-issuer">OIDC Issuer <span class="field-hint">(provider URL)</span></label>
+            <input type="text" id="uf-oidc-issuer" autocomplete="off">
+          </div>
+        </div>
         <div id="user-form-error" class="wizard-error" hidden></div>
         <div style="display:flex;gap:8px;margin-top:8px">
           <button id="btn-save-user" class="btn-primary">Add User</button>
@@ -720,6 +734,48 @@
         <div id="smtp-success" class="import-result" hidden></div>
         <button id="btn-save-smtp" class="btn-secondary" style="margin-top:8px">Save Email Settings</button>
       </div>
+      <!-- OIDC settings (admin only) -->
+      <div id="oidc-settings-section" style="margin-top:16px;border-top:1px solid var(--border);padding-top:16px">
+        <h3 style="font-size:13px;font-weight:600;margin-bottom:10px">Single Sign-On (OIDC)</h3>
+        <div class="form-row">
+          <div class="form-group" style="max-width:100px">
+            <label for="oidc-enabled">Enabled</label>
+            <select id="oidc-enabled">
+              <option value="0">No</option>
+              <option value="1">Yes</option>
+            </select>
+          </div>
+          <div class="form-group">
+            <label for="oidc-button-label">Button Label</label>
+            <input type="text" id="oidc-button-label" placeholder="Sign in with SSO">
+          </div>
+        </div>
+        <div class="form-row">
+          <div class="form-group">
+            <label for="oidc-discovery-url">Discovery URL</label>
+            <input type="url" id="oidc-discovery-url" placeholder="https://auth.example.com/.well-known/openid-configuration">
+          </div>
+        </div>
+        <div class="form-row">
+          <div class="form-group">
+            <label for="oidc-client-id">Client ID</label>
+            <input type="text" id="oidc-client-id" autocomplete="off">
+          </div>
+          <div class="form-group">
+            <label for="oidc-client-secret">Client Secret <span class="field-hint" id="oidc-secret-hint"></span></label>
+            <input type="password" id="oidc-client-secret" autocomplete="new-password">
+          </div>
+        </div>
+        <div class="form-row">
+          <div class="form-group">
+            <label for="oidc-redirect-uri">Redirect URI <span class="field-hint">(full external callback URL)</span></label>
+            <input type="url" id="oidc-redirect-uri" placeholder="https://checks.example.com/api/auth/oidc/callback">
+          </div>
+        </div>
+        <div id="oidc-error" class="wizard-error" hidden></div>
+        <div id="oidc-success" class="import-result" hidden></div>
+        <button id="btn-save-oidc" class="btn-secondary" style="margin-top:8px">Save OIDC Settings</button>
+      </div>
       <!-- Change own password -->
       <div style="margin-top:16px;border-top:1px solid var(--border);padding-top:16px">
         <h3 style="font-size:13px;font-weight:600;margin-bottom:10px">Change My Password</h3>
@@ -741,6 +797,13 @@
         <div id="cp-success" class="import-result" hidden>Password changed.</div>
         <button id="btn-change-password" class="btn-secondary" style="margin-top:8px">Change Password</button>
       </div>
+      <!-- Link my OIDC identity (self-service, shown when OIDC is enabled) -->
+      <div id="oidc-link-section" style="margin-top:16px;border-top:1px solid var(--border);padding-top:16px" hidden>
+        <h3 style="font-size:13px;font-weight:600;margin-bottom:10px">Single Sign-On</h3>
+        <p id="oidc-link-status" style="font-size:12px;color:var(--text-muted);margin-bottom:8px"></p>
+        <a id="btn-oidc-link" href="/api/auth/oidc/link" class="btn-secondary" style="display:inline-block;text-decoration:none">Link My Account</a>
+        <button id="btn-oidc-unlink" class="btn-ghost" style="margin-left:8px" hidden>Unlink</button>
+      </div>
     </div>
   </div>
 

public/js/app.js

@@ -52,6 +52,23 @@ async function checkAuth() {
     showLoginOverlay();
     return false;
   }
+
+  // OIDC callback error/success detection
+  if (location.hash.startsWith('#oidc-error=')) {
+    const msg = decodeURIComponent(location.hash.slice('#oidc-error='.length));
+    history.replaceState(null, '', location.pathname);
+    showLoginSection('login-form-section');
+    const errEl = document.getElementById('login-error');
+    errEl.textContent = msg;
+    errEl.hidden = false;
+    showLoginOverlay();
+    return false;
+  }
+  if (location.hash === '#oidc-linked') {
+    history.replaceState(null, '', location.pathname);
+    // Fall through to normal auth check — user is still logged in
+  }
+
   // Is there already a session?
   const res = await fetch('/api/auth/me');
   if (res.ok) {
@@ -68,10 +85,27 @@ async function checkAuth() {
   } else {
     showLoginSection('login-form-section');
   }
+  // Show SSO button if OIDC is enabled
+  loadOidcLoginButton();
   showLoginOverlay();
   return false;
 }
 
+async function loadOidcLoginButton() {
+  try {
+    const res = await fetch('/api/auth/oidc/config');
+    if (!res.ok) return;
+    const cfg = await res.json();
+    const section = document.getElementById('oidc-login-section');
+    if (cfg.enabled) {
+      document.getElementById('btn-oidc-login').textContent = cfg.button_label || 'Sign in with SSO';
+      section.hidden = false;
+    } else {
+      section.hidden = true;
+    }
+  } catch { /* ignore */ }
+}
+
 async function submitLogin() {
   const username = document.getElementById('login-username').value.trim();
   const password = document.getElementById('login-password').value;
@@ -158,12 +192,23 @@ function applyRoleUI() {
 let usersState = { users: [], editingId: null };
 
 function openUsersModal() {
+  const isAdmin = state.user && state.user.role === 'admin';
   document.getElementById('user-form-error').hidden = true;
+  document.getElementById('users-title').textContent = isAdmin ? 'Manage Users' : 'My Account';
   document.getElementById('users-overlay').classList.add('open');
   document.getElementById('users-modal').classList.add('open');
-  loadUsers();
+  // Admin-only sections
-  renderUfAccountCheckboxes();
+  document.getElementById('users-list').hidden = !isAdmin;
-  if (state.user && state.user.role === 'admin') loadSmtpSettings();
+  document.getElementById('user-form-section').hidden = !isAdmin;
+  document.getElementById('smtp-settings-section').hidden = !isAdmin;
+  document.getElementById('oidc-settings-section').hidden = !isAdmin;
+  if (isAdmin) {
+    loadUsers();
+    renderUfAccountCheckboxes();
+    loadSmtpSettings();
+    loadOidcSettings();
+  }
+  loadOidcLinkStatus();
 }
 
 function closeUsersModal() {
@@ -204,8 +249,9 @@ function renderUsersList() {
             const name = escHtml(a ? (a.company1 || `Account ${a.account_id}`) : `#${ua.account_id}`);
             return `${name} <span style="font-size:10px;color:${ua.role === 'editor' ? '#16a34a' : '#6b7280'};font-weight:600;text-transform:uppercase">${ua.role}</span>`;
           }).join(', ') : '<em style="color:var(--text-muted)">None</em>');
+      const oidcTag = u.oidc_sub ? ' <span style="font-size:10px;color:#2563eb;font-weight:600" title="OIDC linked">SSO</span>' : '';
       return `<tr>
-        <td><strong>${escHtml(u.username)}</strong>${isSelf ? ' <em style="color:var(--text-muted)">(you)</em>' : ''}</td>
+        <td><strong>${escHtml(u.username)}</strong>${isSelf ? ' <em style="color:var(--text-muted)">(you)</em>' : ''}${oidcTag}</td>
         <td>${roleBadge(u.role)}</td>
         <td style="font-size:12px">${accountsLabel}</td>
         <td style="white-space:nowrap">
@@ -253,6 +299,10 @@ function startUserEdit(userId) {
   document.getElementById('btn-save-user').textContent   = 'Save Changes';
   document.getElementById('btn-cancel-user-edit').hidden = false;
   document.getElementById('user-form-error').hidden = true;
+  // OIDC fields
+  document.getElementById('uf-oidc-sub').value    = u.oidc_sub || '';
+  document.getElementById('uf-oidc-issuer').value = u.oidc_issuer || '';
+  document.getElementById('uf-oidc-group').hidden = false;
   renderUfAccountCheckboxes();
   document.getElementById('uf-username').scrollIntoView({ behavior: 'smooth', block: 'nearest' });
 }
@@ -268,6 +318,10 @@ function cancelUserEdit() {
   document.getElementById('btn-save-user').textContent     = 'Add User';
   document.getElementById('btn-cancel-user-edit').hidden   = true;
   document.getElementById('user-form-error').hidden = true;
+  // OIDC fields
+  document.getElementById('uf-oidc-sub').value    = '';
+  document.getElementById('uf-oidc-issuer').value = '';
+  document.getElementById('uf-oidc-group').hidden = true;
   renderUfAccountCheckboxes();
 }
 
@@ -296,6 +350,8 @@ async function saveUser() {
     const body = { username, email, role, accounts };
     if (password) body.password = password;
     if (usersState.editingId) {
+      body.oidc_sub    = document.getElementById('uf-oidc-sub').value.trim();
+      body.oidc_issuer = document.getElementById('uf-oidc-issuer').value.trim();
       await apiFetch('PUT', `/api/users/${usersState.editingId}`, body);
     } else {
       await apiFetch('POST', '/api/users', body);
@@ -1603,6 +1659,83 @@ async function saveSmtpSettings() {
   }
 }
 
+// ── OIDC settings ────────────────────────────────────────────────────────────
+
+async function loadOidcSettings() {
+  try {
+    const s = await apiFetch('GET', '/api/settings/oidc');
+    if (!s) return;
+    document.getElementById('oidc-enabled').value        = s.enabled ? '1' : '0';
+    document.getElementById('oidc-discovery-url').value   = s.discovery_url;
+    document.getElementById('oidc-client-id').value       = s.client_id;
+    document.getElementById('oidc-redirect-uri').value    = s.redirect_uri;
+    document.getElementById('oidc-button-label').value    = s.button_label;
+    document.getElementById('oidc-secret-hint').textContent = s.has_secret ? '(leave blank to keep)' : '';
+  } catch (_) {}
+}
+
+async function saveOidcSettings() {
+  const errEl     = document.getElementById('oidc-error');
+  const successEl = document.getElementById('oidc-success');
+  const btn       = document.getElementById('btn-save-oidc');
+  errEl.hidden = true; successEl.hidden = true;
+  btn.disabled = true;
+  try {
+    await apiFetch('PUT', '/api/settings/oidc', {
+      enabled:       document.getElementById('oidc-enabled').value === '1',
+      discovery_url: document.getElementById('oidc-discovery-url').value.trim(),
+      client_id:     document.getElementById('oidc-client-id').value.trim(),
+      client_secret: document.getElementById('oidc-client-secret').value,
+      redirect_uri:  document.getElementById('oidc-redirect-uri').value.trim(),
+      button_label:  document.getElementById('oidc-button-label').value.trim(),
+    });
+    successEl.textContent = 'Saved.'; successEl.hidden = false;
+    document.getElementById('oidc-client-secret').value = '';
+    await loadOidcSettings();
+    setTimeout(() => { successEl.hidden = true; }, 3000);
+  } catch (err) {
+    errEl.textContent = err.message; errEl.hidden = false;
+  } finally {
+    btn.disabled = false;
+  }
+}
+
+// ── OIDC self-service linking ────────────────────────────────────────────────
+
+async function loadOidcLinkStatus() {
+  try {
+    const cfg = await fetch('/api/auth/oidc/config').then(r => r.json());
+    const section = document.getElementById('oidc-link-section');
+    if (!cfg.enabled) { section.hidden = true; return; }
+    section.hidden = false;
+
+    const me = await apiFetch('GET', '/api/auth/me');
+    const statusEl  = document.getElementById('oidc-link-status');
+    const linkBtn   = document.getElementById('btn-oidc-link');
+    const unlinkBtn = document.getElementById('btn-oidc-unlink');
+
+    if (me.oidc_linked) {
+      statusEl.textContent = 'Your account is linked to SSO.';
+      linkBtn.hidden  = true;
+      unlinkBtn.hidden = false;
+    } else {
+      statusEl.textContent = 'Link your account to sign in with SSO.';
+      linkBtn.hidden  = false;
+      unlinkBtn.hidden = true;
+    }
+  } catch (_) {}
+}
+
+async function unlinkOidc() {
+  if (!confirm('Unlink your SSO identity? You will need to use your password to sign in.')) return;
+  try {
+    await apiFetch('POST', '/api/auth/oidc/unlink');
+    await loadOidcLinkStatus();
+  } catch (err) {
+    alert(err.message);
+  }
+}
+
 // ── Initialization ───────────────────────────────────────────────────────────
 
 async function init() {
@@ -1796,6 +1929,7 @@ async function init() {
 
   // User management
   document.getElementById('btn-users').addEventListener('click', openUsersModal);
+  document.getElementById('header-username').addEventListener('click', openUsersModal);
   document.getElementById('btn-close-users').addEventListener('click', closeUsersModal);
   document.getElementById('users-overlay').addEventListener('click', closeUsersModal);
   document.getElementById('users-list').addEventListener('click', e => {
@@ -1809,6 +1943,8 @@ async function init() {
   document.getElementById('uf-role').addEventListener('change', renderUfAccountCheckboxes);
   document.getElementById('btn-change-password').addEventListener('click', changeOwnPassword);
   document.getElementById('btn-save-smtp').addEventListener('click', saveSmtpSettings);
+  document.getElementById('btn-save-oidc').addEventListener('click', saveOidcSettings);
+  document.getElementById('btn-oidc-unlink').addEventListener('click', unlinkOidc);
 
   // Add checking account
   document.getElementById('btn-add-account').addEventListener('click', openWizard);

src/db/database.js

@@ -139,6 +139,17 @@ db.exec(`
   )
 `);
 
+// Migration: add OIDC columns to users
+const usersInfo2 = db.prepare('PRAGMA table_info(users)').all();
+if (!usersInfo2.some(c => c.name === 'oidc_sub')) {
+  db.exec(`
+    ALTER TABLE users ADD COLUMN oidc_sub TEXT;
+    ALTER TABLE users ADD COLUMN oidc_issuer TEXT;
+    CREATE UNIQUE INDEX IF NOT EXISTS idx_users_oidc ON users(oidc_issuer, oidc_sub)
+      WHERE oidc_sub IS NOT NULL;
+  `);
+}
+
 // Migration: create settings table
 db.exec(`
   CREATE TABLE IF NOT EXISTS settings (

src/routes/auth.js

@@ -123,7 +123,13 @@ router.get('/me', (req, res) => {
   if (!req.session || !req.session.userId) {
     return res.status(401).json({ error: 'Not authenticated.' });
   }
-  res.json({ id: req.session.userId, username: req.session.username, role: req.session.role });
+  const user = db.prepare('SELECT oidc_sub FROM users WHERE id = ?').get(req.session.userId);
+  res.json({
+    id: req.session.userId,
+    username: req.session.username,
+    role: req.session.role,
+    oidc_linked: !!(user && user.oidc_sub),
+  });
 });
 
 // POST /api/auth/change-password — any logged-in user can change their own password
@@ -200,5 +206,180 @@ router.post('/reset-password', async (req, res) => {
   res.json({ ok: true });
 });
 
+// ── OIDC helpers ─────────────────────────────────────────────────────────────
+
+function getOidcSettings() {
+  const rows = db.prepare("SELECT key, value FROM settings WHERE key LIKE 'oidc_%'").all();
+  const s = Object.fromEntries(rows.map(r => [r.key.replace('oidc_', ''), r.value || '']));
+  return {
+    enabled:       s.enabled === '1',
+    discovery_url: s.discovery_url || '',
+    client_id:     s.client_id     || '',
+    client_secret: s.client_secret || '',
+    redirect_uri:  s.redirect_uri  || '',
+    button_label:  s.button_label  || 'Sign in with SSO',
+  };
+}
+
+async function getOidcClient(settings) {
+  const { Issuer } = require('openid-client');
+  const issuer = await Issuer.discover(settings.discovery_url);
+  return new issuer.Client({
+    client_id:     settings.client_id,
+    client_secret: settings.client_secret,
+    redirect_uris: [settings.redirect_uri],
+    response_types: ['code'],
+  });
+}
+
+// GET /api/auth/oidc/config — public, returns whether OIDC is enabled + button label
+router.get('/oidc/config', (req, res) => {
+  const s = getOidcSettings();
+  res.json({ enabled: s.enabled, button_label: s.button_label });
+});
+
+// GET /api/auth/oidc/authorize — initiates the OIDC flow (redirect to provider)
+router.get('/oidc/authorize', async (req, res) => {
+  try {
+    const settings = getOidcSettings();
+    if (!settings.enabled) return res.status(400).json({ error: 'OIDC is not enabled.' });
+
+    const { generators } = require('openid-client');
+    const client = await getOidcClient(settings);
+
+    const code_verifier = generators.codeVerifier();
+    const code_challenge = generators.codeChallenge(code_verifier);
+    const state = generators.state();
+    const nonce = generators.nonce();
+
+    req.session.oidc = { code_verifier, state, nonce };
+
+    const authUrl = client.authorizationUrl({
+      scope: 'openid email profile',
+      state,
+      nonce,
+      code_challenge,
+      code_challenge_method: 'S256',
+    });
+
+    // Ensure session is persisted before redirecting (saveUninitialized is false)
+    req.session.save(() => res.redirect(authUrl));
+  } catch (err) {
+    console.error('[oidc] authorize error:', err.message);
+    res.redirect('/#oidc-error=' + encodeURIComponent('Failed to initiate SSO login.'));
+  }
+});
+
+// GET /api/auth/oidc/callback — handles the provider redirect
+router.get('/oidc/callback', async (req, res) => {
+  try {
+    const settings = getOidcSettings();
+    if (!settings.enabled) return res.redirect('/#oidc-error=' + encodeURIComponent('OIDC is not enabled.'));
+
+    const oidcSession = req.session.oidc;
+    if (!oidcSession) return res.redirect('/#oidc-error=' + encodeURIComponent('Session expired. Please try again.'));
+
+    const client = await getOidcClient(settings);
+    const params = client.callbackParams(req);
+
+    const tokenSet = await client.callback(settings.redirect_uri, params, {
+      code_verifier: oidcSession.code_verifier,
+      state:         oidcSession.state,
+      nonce:         oidcSession.nonce,
+    });
+
+    const claims = tokenSet.claims();
+    const sub    = claims.sub;
+    const issuer = claims.iss;
+
+    delete req.session.oidc;
+
+    // Self-service linking flow
+    if (oidcSession.linking && oidcSession.linkUserId) {
+      const existing = db.prepare(
+        'SELECT id FROM users WHERE oidc_issuer = ? AND oidc_sub = ? AND id != ?'
+      ).get(issuer, sub, oidcSession.linkUserId);
+      if (existing) {
+        return res.redirect('/#oidc-error=' + encodeURIComponent('This identity is already linked to another account.'));
+      }
+
+      db.prepare("UPDATE users SET oidc_sub = ?, oidc_issuer = ?, updated_at = datetime('now') WHERE id = ?")
+        .run(sub, issuer, oidcSession.linkUserId);
+      return res.redirect('/#oidc-linked');
+    }
+
+    // Login flow — look up user by OIDC identity
+    const user = db.prepare(
+      'SELECT id, username, role FROM users WHERE oidc_issuer = ? AND oidc_sub = ?'
+    ).get(issuer, sub);
+
+    if (!user) {
+      return res.redirect('/#oidc-error=' + encodeURIComponent(
+        'No account is linked to this identity. Ask an admin to link your account, or sign in with your password and link it yourself.'
+      ));
+    }
+
+    req.session.userId   = user.id;
+    req.session.username = user.username;
+    req.session.role     = user.role;
+
+    // Load account access into session (mirrors login behavior)
+    if (user.role !== 'admin') {
+      const accts = db.prepare('SELECT account_id, role FROM user_accounts WHERE user_id = ?').all(user.id);
+      req.session.accounts = accts;
+    }
+
+    res.redirect('/');
+  } catch (err) {
+    console.error('[oidc] callback error:', err.message);
+    res.redirect('/#oidc-error=' + encodeURIComponent('SSO login failed. Please try again.'));
+  }
+});
+
+// GET /api/auth/oidc/link — logged-in user initiates linking flow
+router.get('/oidc/link', async (req, res) => {
+  if (!req.session || !req.session.userId) {
+    return res.redirect('/#oidc-error=' + encodeURIComponent('You must be signed in to link your account.'));
+  }
+
+  try {
+    const settings = getOidcSettings();
+    if (!settings.enabled) return res.redirect('/#oidc-error=' + encodeURIComponent('OIDC is not enabled.'));
+
+    const { generators } = require('openid-client');
+    const client = await getOidcClient(settings);
+
+    const code_verifier = generators.codeVerifier();
+    const code_challenge = generators.codeChallenge(code_verifier);
+    const state = generators.state();
+    const nonce = generators.nonce();
+
+    req.session.oidc = { code_verifier, state, nonce, linking: true, linkUserId: req.session.userId };
+
+    const authUrl = client.authorizationUrl({
+      scope: 'openid email profile',
+      state,
+      nonce,
+      code_challenge,
+      code_challenge_method: 'S256',
+    });
+
+    req.session.save(() => res.redirect(authUrl));
+  } catch (err) {
+    console.error('[oidc] link error:', err.message);
+    res.redirect('/#oidc-error=' + encodeURIComponent('Failed to initiate SSO linking.'));
+  }
+});
+
+// POST /api/auth/oidc/unlink — logged-in user removes their own OIDC link
+router.post('/oidc/unlink', (req, res) => {
+  if (!req.session || !req.session.userId) {
+    return res.status(401).json({ error: 'Not authenticated.' });
+  }
+  db.prepare("UPDATE users SET oidc_sub = NULL, oidc_issuer = NULL, updated_at = datetime('now') WHERE id = ?")
+    .run(req.session.userId);
+  res.json({ ok: true });
+});
+
 module.exports = router;
 module.exports.validatePassword = validatePassword;

src/routes/settings.js

@@ -36,4 +36,35 @@ router.put('/smtp', (req, res) => {
   res.json({ ok: true });
 });
 
+// GET /api/settings/oidc
+router.get('/oidc', (req, res) => {
+  const rows = db.prepare("SELECT key, value FROM settings WHERE key LIKE 'oidc_%'").all();
+  const s = Object.fromEntries(rows.map(r => [r.key.replace('oidc_', ''), r.value || '']));
+  res.json({
+    enabled:       s.enabled === '1',
+    discovery_url: s.discovery_url || '',
+    client_id:     s.client_id     || '',
+    redirect_uri:  s.redirect_uri  || '',
+    button_label:  s.button_label  || 'Sign in with SSO',
+    has_secret:    !!(rows.find(r => r.key === 'oidc_client_secret') || {}).value,
+  });
+});
+
+// PUT /api/settings/oidc
+router.put('/oidc', (req, res) => {
+  const { enabled, discovery_url, client_id, client_secret, redirect_uri, button_label } = req.body;
+  const upsert = db.prepare('INSERT OR REPLACE INTO settings (key, value) VALUES (?, ?)');
+  db.transaction(() => {
+    upsert.run('oidc_enabled',       enabled ? '1' : '0');
+    upsert.run('oidc_discovery_url', discovery_url || '');
+    upsert.run('oidc_client_id',     client_id     || '');
+    upsert.run('oidc_redirect_uri',  redirect_uri  || '');
+    upsert.run('oidc_button_label',  button_label  || 'Sign in with SSO');
+    if (client_secret !== undefined && client_secret !== '') {
+      upsert.run('oidc_client_secret', client_secret);
+    }
+  })();
+  res.json({ ok: true });
+});
+
 module.exports = router;

src/routes/users.js

@@ -11,7 +11,7 @@ const { validatePassword } = require('./auth');
 router.use(requireAuth, requireAdmin);
 
 function userWithAccounts(id) {
-  const user = db.prepare('SELECT id, username, email, role, created_at FROM users WHERE id = ?').get(id);
+  const user = db.prepare('SELECT id, username, email, role, oidc_sub, oidc_issuer, created_at FROM users WHERE id = ?').get(id);
   if (!user) return null;
   user.accounts = db.prepare('SELECT account_id, role FROM user_accounts WHERE user_id = ?').all(id);
   return user;
@@ -19,7 +19,7 @@ function userWithAccounts(id) {
 
 // GET /api/users
 router.get('/', (req, res) => {
-  const users = db.prepare('SELECT id, username, email, role, created_at FROM users ORDER BY id ASC').all();
+  const users = db.prepare('SELECT id, username, email, role, oidc_sub, oidc_issuer, created_at FROM users ORDER BY id ASC').all();
   users.forEach(u => {
     u.accounts = db.prepare('SELECT account_id, role FROM user_accounts WHERE user_id = ?').all(u.id);
   });
@@ -60,7 +60,7 @@ router.put('/:id', async (req, res) => {
   const user = db.prepare('SELECT id, role FROM users WHERE id = ?').get(req.params.id);
   if (!user) return res.status(404).json({ error: 'User not found.' });
 
-  const { username, password, role, accounts, email } = req.body;
+  const { username, password, role, accounts, email, oidc_sub, oidc_issuer } = req.body;
 
   if (role && !['admin', 'editor', 'viewer'].includes(role)) {
     return res.status(400).json({ error: 'Invalid role.' });
@@ -94,6 +94,23 @@ router.put('/:id', async (req, res) => {
       .run(hash, req.params.id);
   }
 
+  // OIDC linking — admin can set or clear oidc_sub/oidc_issuer
+  if (oidc_sub !== undefined) {
+    const newSub    = oidc_sub    ? oidc_sub.trim()    : null;
+    const newIssuer = oidc_issuer ? oidc_issuer.trim() : null;
+    if (newSub && !newIssuer) {
+      return res.status(400).json({ error: 'OIDC issuer is required when setting OIDC subject.' });
+    }
+    if (newSub) {
+      const existing = db.prepare(
+        'SELECT id FROM users WHERE oidc_issuer = ? AND oidc_sub = ? AND id != ?'
+      ).get(newIssuer, newSub, req.params.id);
+      if (existing) return res.status(409).json({ error: 'This OIDC identity is already linked to another user.' });
+    }
+    db.prepare("UPDATE users SET oidc_sub = ?, oidc_issuer = ?, updated_at = datetime('now') WHERE id = ?")
+      .run(newSub, newSub ? newIssuer : null, req.params.id);
+  }
+
   if (Array.isArray(accounts)) {
     db.prepare('DELETE FROM user_accounts WHERE user_id = ?').run(req.params.id);
     const effectiveRole = role || user.role;