Add new device verification

.env.template

@@ -409,6 +409,12 @@
 ## If sending the email fails the login attempt will fail!!
 # REQUIRE_DEVICE_EMAIL=false
 
+## New device verification (Bitwarden "New device login protection").
+## Users without 2FA logging in from a device that is not known yet must first enter a code sent to
+## their account email address. Users can turn this off for their own account in the web vault.
+## Requires a mail transport to be configured, otherwise the server refuses to start.
+# NEW_DEVICE_VERIFICATION=false
+
 ## Enable extended logging, which shows timestamps and targets in the logs
 # EXTENDED_LOGGING=true
 

Cargo.toml

@@ -107,7 +107,7 @@ serde = { version = "1.0.229", features = ["derive"] }
 serde_json = "1.0.151"
 
 # A safe, extensible ORM and Query builder
-diesel = { version = "2.3.13", features = ["chrono", "r2d2", "numeric"] }
+diesel = { version = "2.3.13", features = ["chrono", "r2d2", "numeric", "64-column-tables"] }
 diesel_migrations = "2.3.2"
 
 derive_more = { version = "2.1.1", features = [

migrations/mysql/2026-09-05-120000_add_verify_devices/down.sql

@@ -0,0 +1 @@
+ALTER TABLE users DROP COLUMN verify_devices;

migrations/mysql/2026-09-05-120000_add_verify_devices/up.sql

@@ -0,0 +1,2 @@
+ALTER TABLE users
+ADD COLUMN verify_devices BOOLEAN NOT NULL DEFAULT TRUE;

migrations/postgresql/2026-09-05-120000_add_verify_devices/down.sql

@@ -0,0 +1 @@
+ALTER TABLE users DROP COLUMN verify_devices;

migrations/postgresql/2026-09-05-120000_add_verify_devices/up.sql

@@ -0,0 +1,2 @@
+ALTER TABLE users
+ADD COLUMN verify_devices BOOLEAN NOT NULL DEFAULT TRUE;

migrations/sqlite/2026-09-05-120000_add_verify_devices/down.sql

@@ -0,0 +1 @@
+ALTER TABLE users DROP COLUMN verify_devices;

migrations/sqlite/2026-09-05-120000_add_verify_devices/up.sql

@@ -0,0 +1,2 @@
+ALTER TABLE users
+ADD COLUMN verify_devices BOOLEAN NOT NULL DEFAULT 1; -- TRUE

src/api/core/two_factor/mod.rs

@@ -24,6 +24,7 @@ pub mod authenticator;
 pub mod duo;
 pub mod duo_oidc;
 pub mod email;
+pub mod new_device_verification;
 pub mod protected_actions;
 pub mod webauthn;
 pub mod yubikey;
@@ -60,6 +61,7 @@ pub fn is_twofactor_provider_usable(provider_type: &TwoFactorType, provider_data
         | TwoFactorType::EmailVerificationChallenge
         | TwoFactorType::WebauthnRegisterChallenge
         | TwoFactorType::WebauthnLoginChallenge
+        | TwoFactorType::NewDeviceVerification
         | TwoFactorType::ProtectedActions => false,
     }
 }
@@ -73,6 +75,7 @@ pub fn routes() -> Vec<Route> {
     routes.append(&mut webauthn::routes());
     routes.append(&mut yubikey::routes());
     routes.append(&mut protected_actions::routes());
+    routes.append(&mut new_device_verification::routes());
 
     routes
 }
@@ -236,20 +239,15 @@ pub async fn send_incomplete_2fa_notifications(pool: DbPool) {
     }
 }
 
-// This function currently is just a dummy and the actual part is not implemented yet.
+// Kept to prevent 404 errors, current clients read `verifyDevices` from the profile and change it
-// This also prevents 404 errors.
+// via `/api/accounts/verify-devices`.
 //
 // See the following Bitwarden PR's regarding this feature.
 // https://github.com/bitwarden/clients/pull/2843
 // https://github.com/bitwarden/clients/pull/2839
 // https://github.com/bitwarden/server/pull/2016
-//
-// The HTML part is hidden via the CSS patches done via the bw_web_build repo
 #[get("/two-factor/get-device-verification-settings")]
-fn get_device_verification_settings(_headers: Headers, _conn: DbConn) -> Json<Value> {
+fn get_device_verification_settings(headers: Headers) -> Json<Value> {
-    Json(json!({
+    let user = headers.user;
-        "isDeviceVerificationSectionEnabled":false,
+    Json(new_device_verification::device_verification_settings(&user))
-        "unknownDeviceVerificationEnabled":false,
-        "object":"deviceVerificationSettings"
-    }))
 }

src/api/core/two_factor/new_device_verification.rs

@@ -0,0 +1,497 @@
+//! New device verification, the Bitwarden "New device login protection" feature: a password login
+//! from an unknown device first has to be confirmed with a code mailed to the account address.
+//!
+//! Reference: <https://github.com/bitwarden/server/blob/main/src/Identity/IdentityServer/RequestValidators/DeviceValidator.cs>
+
+use chrono::{NaiveDateTime, TimeDelta, Utc, naive::serde::ts_seconds};
+use rocket::{
+    Route,
+    request::{FromRequest, Outcome},
+    serde::json::Json,
+};
+use serde_json::Value;
+
+use crate::{
+    CONFIG,
+    api::{EmptyResult, PasswordOrOtpData},
+    auth::{ClientIp, Headers},
+    crypto,
+    db::{
+        DbConn,
+        models::{Device, DeviceId, EventType, TwoFactor, TwoFactorType, User},
+    },
+    error::{Error, ErrorEvent},
+    mail,
+};
+
+pub fn routes() -> Vec<Route> {
+    routes![resend_new_device_otp, put_verify_devices, post_verify_devices]
+}
+
+/// Accounts younger than this are exempt upstream.
+const NEW_ACCOUNT_EXEMPTION_HOURS: i64 = 24;
+
+/// Preserve the pending device identifier for resend requests from older mobile clients.
+const PENDING_DEVICE_SECONDS: i64 = 15 * 60;
+
+/// Data stored in the `twofactor` table under [`TwoFactorType::NewDeviceVerification`]. Only read
+/// and written here, so a code issued for a new device can never authorize anything else.
+#[derive(Debug, Serialize, Deserialize)]
+pub struct NewDeviceVerificationData {
+    pub token: String,
+    #[serde(with = "ts_seconds")]
+    pub token_sent: NaiveDateTime,
+    pub device_identifier: DeviceId,
+    pub security_stamp: String,
+}
+
+impl NewDeviceVerificationData {
+    fn new(token: String, device_identifier: DeviceId, security_stamp: String) -> Self {
+        Self {
+            token,
+            token_sent: Utc::now().naive_utc(),
+            device_identifier,
+            security_stamp,
+        }
+    }
+
+    fn to_json(&self) -> String {
+        serde_json::to_string(&self).unwrap()
+    }
+
+    fn from_json(string: &str) -> Result<Self, Error> {
+        if let Ok(data) = serde_json::from_str(string) {
+            Ok(data)
+        } else {
+            err!("Could not decode NewDeviceVerificationData from string")
+        }
+    }
+
+    fn time_since_sent(&self) -> TimeDelta {
+        Utc::now().naive_utc() - self.token_sent
+    }
+
+    fn is_expired(&self, max_age_seconds: i64) -> bool {
+        self.time_since_sent().num_seconds() > max_age_seconds
+    }
+
+    fn matches_device_and_stamp(&self, device_id: &DeviceId, security_stamp: &str) -> bool {
+        &self.device_identifier == device_id && self.security_stamp == security_stamp
+    }
+}
+
+#[expect(clippy::struct_excessive_bools, reason = "Every condition upstream checks, kept separate to stay testable")]
+#[derive(Clone, Copy)]
+pub struct NewDeviceState<'a> {
+    pub enforced: bool,
+    pub verify_devices: bool,
+    /// The account is younger than the Bitwarden exemption period.
+    pub recently_created: bool,
+    pub has_two_factor: bool,
+    pub known_device: bool,
+    pub has_devices: bool,
+    pub new_device_otp: Option<&'a str>,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum NewDeviceAction {
+    Skip,
+    Verify,
+    Challenge,
+}
+
+/// Mirrors `DeviceValidator.HandleNewDeviceVerificationAsync` of the Bitwarden server.
+pub fn new_device_action(state: NewDeviceState<'_>) -> NewDeviceAction {
+    // A non-empty code implies an unknown device, upstream skips the lookup for it.
+    if state.new_device_otp.is_none_or(str::is_empty) && state.known_device {
+        return NewDeviceAction::Skip;
+    }
+
+    // Upstream skips device verification for 2FA users entirely, they keep their existing flow.
+    if !state.enforced || !state.verify_devices || state.recently_created || state.has_two_factor {
+        return NewDeviceAction::Skip;
+    }
+
+    // An empty code counts as a wrong code upstream.
+    if state.new_device_otp.is_some() {
+        return NewDeviceAction::Verify;
+    }
+
+    // A user without any device is a freshly registered user.
+    if !state.has_devices {
+        return NewDeviceAction::Skip;
+    }
+
+    NewDeviceAction::Challenge
+}
+
+/// The clients match `ErrorModel.Message` literally to switch to their new device verification
+/// screen and show `error_description`. See `api.service.ts` and
+/// `new-device-verification.component.ts` in `bitwarden/clients`.
+fn device_error(description: &str, message: &str) -> Error {
+    let body = json!({
+        "error": "device_error",
+        "error_description": description,
+        "ErrorModel": {
+            "Message": message,
+            "Object": "error"
+        }
+    });
+    Error::from((description, body)).with_event(ErrorEvent {
+        event: EventType::UserFailedLogIn,
+    })
+}
+
+fn verification_required_error() -> Error {
+    device_error("New device verification required", "new device verification required")
+}
+
+fn invalid_otp_error() -> Error {
+    device_error("Invalid New Device OTP", "invalid new device otp")
+}
+
+/// Has to run before the device is stored. Errors are the exact responses the Bitwarden clients expect.
+pub async fn validate_new_device_login(
+    user: &mut User,
+    device_id: &DeviceId,
+    device_type: i32,
+    new_device_otp: Option<&str>,
+    is_auth_request: bool,
+    ip: &ClientIp,
+    conn: &DbConn,
+) -> EmptyResult {
+    // Login with device re-uses the password grant but is only ever approved from a known device.
+    let enforced = CONFIG.new_device_verification() && CONFIG.mail_enabled() && !is_auth_request;
+
+    let recently_created = Utc::now().naive_utc() - user.created_at < TimeDelta::hours(NEW_ACCOUNT_EXEMPTION_HOURS);
+
+    // Avoids the queries below, `new_device_action` would return `Skip` for each of these too.
+    if !enforced || !user.verify_devices || recently_created {
+        return Ok(());
+    }
+
+    let known_device = Device::find_by_uuid_and_user(device_id, &user.uuid, conn).await.is_some();
+    let has_devices = known_device || Device::has_any_by_user(&user.uuid, conn).await;
+    let state = NewDeviceState {
+        enforced,
+        verify_devices: user.verify_devices,
+        recently_created,
+        has_two_factor: !TwoFactor::find_by_user(&user.uuid, conn).await.is_empty(),
+        known_device,
+        has_devices,
+        new_device_otp,
+    };
+
+    match new_device_action(state) {
+        NewDeviceAction::Skip => Ok(()),
+        NewDeviceAction::Verify => {
+            validate_otp(new_device_otp.unwrap_or_default(), user, device_id, conn).await?;
+
+            // The user proved access to their mailbox, so upstream marks the address as verified.
+            if user.verified_at.is_none() {
+                user.verified_at = Some(Utc::now().naive_utc());
+                user.save(conn).await?;
+            }
+            Ok(())
+        }
+        NewDeviceAction::Challenge => {
+            send_otp(user, device_id, device_type, ip, conn).await?;
+            Err(verification_required_error())
+        }
+    }
+}
+
+async fn send_otp(user: &User, device_id: &DeviceId, device_type: i32, ip: &ClientIp, conn: &DbConn) -> EmptyResult {
+    // Bitwarden replaces the pending code on each new challenge or resend.
+    let data = NewDeviceVerificationData::new(
+        crypto::generate_email_token(CONFIG.email_token_size()),
+        device_id.clone(),
+        user.security_stamp.clone(),
+    );
+    let twofactor = TwoFactor::new(user.uuid.clone(), TwoFactorType::NewDeviceVerification, data.to_json());
+    twofactor.save(conn).await?;
+
+    if let Err(e) =
+        mail::send_new_device_verification(&user.email, &data.token, &ip.ip.to_string(), &data.token_sent, device_type)
+            .await
+    {
+        error!("Error sending new device verification email: {e:#?}");
+        // Only remove our own unsent code; a concurrent resend may already have replaced it.
+        if let Err(e) = twofactor.delete(conn).await {
+            error!("Error removing the unsent new device verification code: {e:#?}");
+        }
+        err!(
+            "Could not send the new device verification email. Please contact your administrator.",
+            ErrorEvent {
+                event: EventType::UserFailedLogIn
+            }
+        )
+    }
+
+    Ok(())
+}
+
+/// Validate and atomically consume the code only if no newer code has replaced it.
+async fn validate_otp(otp: &str, user: &User, device_id: &DeviceId, conn: &DbConn) -> EmptyResult {
+    let type_ = TwoFactorType::NewDeviceVerification;
+    let tf = TwoFactor::find_by_user_and_type(&user.uuid, type_, conn).await.ok_or_else(invalid_otp_error)?;
+    let data = NewDeviceVerificationData::from_json(&tf.data)?;
+
+    if !data.matches_device_and_stamp(device_id, &user.security_stamp)
+        || data.is_expired(CONFIG.email_expiration_time().cast_signed())
+        || !crypto::ct_eq(&data.token, otp)
+    {
+        // Keep the expired record briefly for mobile clients that resend without a device header.
+        return Err(invalid_otp_error());
+    }
+
+    let expected_data = tf.data.clone();
+    if !tf.delete_if_data_matches(&expected_data, conn).await? {
+        return Err(invalid_otp_error());
+    }
+    Ok(())
+}
+
+#[derive(Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct ResendNewDeviceOtpData {
+    #[serde(alias = "Email")]
+    email: String,
+    #[serde(alias = "MasterPasswordHash")]
+    master_password_hash: Option<String>,
+    #[serde(alias = "OTP", alias = "Otp")]
+    otp: Option<String>,
+}
+
+/// Current web clients identify the device via this header. Older mobile clients omit it.
+struct ResendDeviceIdentifier(Option<String>);
+
+#[rocket::async_trait]
+impl<'r> FromRequest<'r> for ResendDeviceIdentifier {
+    type Error = &'static str;
+
+    async fn from_request(request: &'r rocket::Request<'_>) -> Outcome<Self, Self::Error> {
+        Outcome::Success(Self(request.headers().get_one("Device-Identifier").map(str::to_owned)))
+    }
+}
+
+/// Mirrors the upstream resend endpoint, including its silent success for invalid secrets.
+#[post("/accounts/resend-new-device-otp", data = "<data>")]
+async fn resend_new_device_otp(
+    data: Json<ResendNewDeviceOtpData>,
+    device_identifier: ResendDeviceIdentifier,
+    ip: ClientIp,
+    conn: DbConn,
+) -> EmptyResult {
+    crate::ratelimit::check_limit_login(&ip.ip)?;
+
+    let ResendDeviceIdentifier(request_device_id) = device_identifier;
+    // Reject malformed identifiers before looking up the user, just like Bitwarden.
+    if request_device_id.as_ref().is_some_and(|id| id.len() > 50) {
+        err!("Invalid device identifier");
+    }
+
+    let data: ResendNewDeviceOtpData = data.into_inner();
+    if !CONFIG.new_device_verification() || !CONFIG.mail_enabled() {
+        return Ok(());
+    }
+
+    let Some(user) = User::find_by_mail(data.email.trim(), &conn).await else {
+        return Ok(());
+    };
+
+    if !user.enabled || !user.verify_devices {
+        return Ok(());
+    }
+
+    let secret = PasswordOrOtpData {
+        master_password_hash: data.master_password_hash,
+        otp: data.otp,
+    };
+    if secret.validate(&user, true, &conn).await.is_err() {
+        return Ok(());
+    }
+
+    // Old Android/iOS clients do not send the Device-Identifier header. Reuse the
+    // pending device for up to 15 minutes, independently of the OTP's validity.
+    let device_id = if let Some(id) = request_device_id.filter(|id| !id.trim().is_empty()) {
+        DeviceId::from(id)
+    } else {
+        let Some(tf) = TwoFactor::find_by_user_and_type(&user.uuid, TwoFactorType::NewDeviceVerification, &conn).await
+        else {
+            return Ok(());
+        };
+        let pending = NewDeviceVerificationData::from_json(&tf.data)?;
+        if pending.security_stamp != user.security_stamp || pending.is_expired(PENDING_DEVICE_SECONDS) {
+            return Ok(());
+        }
+        pending.device_identifier
+    };
+
+    if let Err(e) = send_otp(&user, &device_id, 14, &ip, &conn).await {
+        error!("Error resending new device verification code: {e:#?}");
+    }
+
+    Ok(())
+}
+
+#[derive(Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct SetVerifyDevicesData {
+    #[serde(alias = "MasterPasswordHash")]
+    master_password_hash: Option<String>,
+    otp: Option<String>,
+    #[serde(alias = "VerifyDevices")]
+    verify_devices: bool,
+}
+
+/// Current clients use `POST`, older ones and the API docs use `PUT`.
+#[post("/accounts/verify-devices", data = "<data>")]
+async fn post_verify_devices(data: Json<SetVerifyDevicesData>, headers: Headers, conn: DbConn) -> EmptyResult {
+    let data: SetVerifyDevicesData = data.into_inner();
+    let mut user = headers.user;
+
+    // Same user verification upstream requires for this setting.
+    PasswordOrOtpData {
+        master_password_hash: data.master_password_hash,
+        otp: data.otp,
+    }
+    .validate(&user, true, &conn)
+    .await?;
+
+    user.verify_devices = data.verify_devices;
+    user.save(&conn).await
+}
+
+#[put("/accounts/verify-devices", data = "<data>")]
+async fn put_verify_devices(data: Json<SetVerifyDevicesData>, headers: Headers, conn: DbConn) -> EmptyResult {
+    post_verify_devices(data, headers, conn).await
+}
+
+/// Only the pre-2023 web vault reads this. Its section stays disabled because the setter it needs was
+/// never part of Vaultwarden, so showing it would only produce a broken toggle.
+pub fn device_verification_settings(user: &User) -> Value {
+    let enabled = CONFIG.new_device_verification() && CONFIG.mail_enabled() && user.verify_devices;
+
+    json!({
+        "isDeviceVerificationSectionEnabled": false,
+        "unknownDeviceVerificationEnabled": enabled,
+        "object": "deviceVerificationSettings"
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn challenged() -> NewDeviceState<'static> {
+        NewDeviceState {
+            enforced: true,
+            verify_devices: true,
+            recently_created: false,
+            has_two_factor: false,
+            known_device: false,
+            has_devices: true,
+            new_device_otp: None,
+        }
+    }
+
+    type Case = (&'static str, Option<&'static str>, fn(&mut NewDeviceState<'static>), NewDeviceAction);
+
+    #[test]
+    fn decision_matches_upstream() {
+        use NewDeviceAction::{Challenge, Skip, Verify};
+
+        let cases: [Case; 13] = [
+            ("unknown device without 2fa", None, |_| (), Challenge),
+            ("feature disabled", None, |s| s.enforced = false, Skip),
+            ("user opted out", None, |s| s.verify_devices = false, Skip),
+            ("account within the exemption period", None, |s| s.recently_created = true, Skip),
+            ("2fa configured", None, |s| s.has_two_factor = true, Skip),
+            ("2fa configured and a code sent", Some("123456"), |s| s.has_two_factor = true, Skip),
+            ("known device", None, |s| s.known_device = true, Skip),
+            ("account without any device", None, |s| s.has_devices = false, Skip),
+            ("code sent", Some("123456"), |_| (), Verify),
+            ("code sent from a known device", Some("123456"), |s| s.known_device = true, Verify),
+            ("code sent without any device", Some("123456"), |s| s.has_devices = false, Verify),
+            // An empty code counts as wrong, but unlike a real one it does not skip the known device lookup.
+            ("empty code sent", Some(""), |_| (), Verify),
+            ("empty code sent from a known device", Some(""), |s| s.known_device = true, Skip),
+        ];
+
+        for (case, new_device_otp, setup, expected) in cases {
+            let mut state = challenged();
+            state.new_device_otp = new_device_otp;
+            setup(&mut state);
+            assert_eq!(new_device_action(state), expected, "{case}");
+        }
+    }
+
+    /// Guards the early return in `validate_new_device_login`.
+    #[test]
+    fn shortcut_only_skips_what_the_decision_skips() {
+        for enforced in [false, true] {
+            for verify_devices in [false, true] {
+                for recently_created in [false, true] {
+                    if enforced && verify_devices && !recently_created {
+                        continue;
+                    }
+                    let state = NewDeviceState {
+                        enforced,
+                        verify_devices,
+                        recently_created,
+                        ..challenged()
+                    };
+                    assert_eq!(new_device_action(state), NewDeviceAction::Skip);
+                }
+            }
+        }
+    }
+
+    /// The clients compare these strings literally, changing them breaks the flow silently.
+    #[test]
+    fn client_matched_response_fields_are_stable() {
+        for (error, description, message) in [
+            (verification_required_error(), "New device verification required", "new device verification required"),
+            (invalid_otp_error(), "Invalid New Device OTP", "invalid new device otp"),
+        ] {
+            let expected = json!({
+                "error": "device_error",
+                "error_description": description,
+                "ErrorModel": { "Message": message, "Object": "error" }
+            });
+            // An exact match also keeps out `TwoFactorProviders2`, which the clients check first.
+            assert_eq!(serde_json::from_str::<Value>(&error.to_string()).unwrap(), expected);
+        }
+    }
+
+    #[test]
+    fn stored_code_is_device_and_security_stamp_bound() {
+        let device_id = DeviceId::from("device-1".to_owned());
+        let mut sent = NewDeviceVerificationData::new("123456".into(), device_id.clone(), "security-stamp-1".into());
+        let mut data = NewDeviceVerificationData::from_json(&sent.to_json()).expect("stored data must round trip");
+        assert_eq!(data.token, "123456");
+        assert!(data.matches_device_and_stamp(&device_id, "security-stamp-1"));
+        assert!(!data.matches_device_and_stamp(&DeviceId::from("device-2".to_owned()), "security-stamp-1"));
+        assert!(!data.matches_device_and_stamp(&device_id, "security-stamp-2"));
+        assert!(!data.is_expired(600));
+
+        sent.token_sent -= TimeDelta::seconds(601);
+        data = NewDeviceVerificationData::from_json(&sent.to_json()).unwrap();
+        assert!(data.is_expired(600));
+        assert!(!data.is_expired(PENDING_DEVICE_SECONDS));
+    }
+
+    #[test]
+    fn resend_accepts_bitwarden_client_field_names() {
+        for raw in [
+            r#"{"Email":"user@example.com","MasterPasswordHash":"hash"}"#,
+            r#"{"email":"user@example.com","masterPasswordHash":"hash"}"#,
+            r#"{"Email":"user@example.com","MasterPasswordHash":null,"OTP":"654321"}"#,
+        ] {
+            let data: ResendNewDeviceOtpData = serde_json::from_str(raw).expect("client request must deserialize");
+            assert_eq!(data.email, "user@example.com");
+            assert!(data.master_password_hash.is_some() || data.otp.is_some());
+        }
+    }
+}

src/api/identity.rs

@@ -17,7 +17,8 @@ use crate::{
             accounts::{PreloginData, RegisterData, kdf_upgrade, prelogin, register},
             log_user_event,
             two_factor::{
-                authenticator, duo_oidc, email, enforce_2fa_policy, is_twofactor_provider_usable, webauthn, yubikey,
+                authenticator, duo_oidc, email, enforce_2fa_policy, is_twofactor_provider_usable,
+                new_device_verification, webauthn, yubikey,
             },
         },
         identity_master_password_policy,
@@ -476,6 +477,18 @@ async fn password_login(data: ConnectData, user_id: &mut Option<UserId>, conn: &
         )
     }
 
+    // Runs before the device is stored, so a correct master password alone never makes it known.
+    new_device_verification::validate_new_device_login(
+        &mut user,
+        data.device_identifier.as_ref().unwrap(),
+        util::try_parse_string(data.device_type.as_ref()).unwrap_or(14),
+        data.new_device_otp.as_deref(),
+        data.auth_request.is_some(),
+        ip,
+        conn,
+    )
+    .await?;
+
     let mut device = get_device(&data, conn, &user).await?;
 
     let twofactor_token = twofactor_auth(&mut user, &data, &mut device, ip, conn).await?;
@@ -999,6 +1012,7 @@ async fn json_err_twofactor(providers: &[i32], user: &User, data: &ConnectData,
             | Some(
                 TwoFactorType::Authenticator
                 | TwoFactorType::EmailVerificationChallenge
+                | TwoFactorType::NewDeviceVerification
                 | TwoFactorType::OrganizationDuo
                 | TwoFactorType::ProtectedActions
                 | TwoFactorType::RecoveryCode
@@ -1156,6 +1170,11 @@ struct ConnectData {
     #[field(name = uncased("authrequest"))]
     auth_request: Option<AuthRequestId>,
 
+    // Needed for new device verification, the clients send this as `newDeviceOtp`
+    #[field(name = uncased("new_device_otp"))]
+    #[field(name = uncased("newdeviceotp"))]
+    new_device_otp: Option<String>,
+
     // Needed for authorization code
     #[field(name = uncased("code"))]
     code: Option<OIDCCode>,

src/config.rs

@@ -729,6 +729,10 @@ make_config! {
         /// If sending the email fails the login attempt will fail.
         require_device_email:   bool,   true,   def,     false;
 
+        /// New device verification |> Users without 2FA logging in from an unknown device must first enter
+        /// a code emailed to their account address. Requires a mail transport to be configured.
+        new_device_verification: bool,  true,   def,     false;
+
         /// Reload templates (Dev) |> When this is set to true, the templates get reloaded with every request.
         /// ONLY use this during development, as it can slow down the server
         reload_templates:       bool,   true,   def,    false;
@@ -1198,6 +1202,11 @@ fn validate_config(cfg: &ConfigItems, on_update: bool) -> Result<(), Error> {
         err!("To use email 2FA as automatic fallback, email 2fa has to be enabled!");
     }
 
+    // Without a mail transport the code can never arrive, locking users out of every new device.
+    if cfg.new_device_verification && !(cfg._enable_smtp && (cfg.smtp_host.is_some() || cfg.use_sendmail)) {
+        err!("To enable new device verification, a mail transport must be configured")
+    }
+
     // Check if the HTTP request block regex is valid
     if let Some(ref r) = cfg.http_request_block_regex {
         let validate_regex = regex::Regex::new(r);
@@ -1735,6 +1744,7 @@ where
     reg!("email/invite_accepted", ".html");
     reg!("email/invite_confirmed", ".html");
     reg!("email/new_device_logged_in", ".html");
+    reg!("email/new_device_verification", ".html");
     reg!("email/protected_action", ".html");
     reg!("email/pw_hint_none", ".html");
     reg!("email/pw_hint_some", ".html");

src/db/models/device.rs

@@ -201,6 +201,20 @@ impl Device {
         result
     }
 
+    /// A lightweight existence check avoids loading every registered device on login.
+    pub async fn has_any_by_user(user_uuid: &UserId, conn: &DbConn) -> bool {
+        conn.run(move |conn| {
+            devices::table
+                .filter(devices::user_uuid.eq(user_uuid))
+                .select(devices::uuid)
+                .first::<DeviceId>(conn)
+                .optional()
+                .expect("Error checking whether user has devices")
+                .is_some()
+        })
+        .await
+    }
+
     pub async fn find_by_user(user_uuid: &UserId, conn: &DbConn) -> Vec<Self> {
         conn.run(move |conn| {
             devices::table.filter(devices::user_uuid.eq(user_uuid)).load::<Self>(conn).expect("Error loading devices")

src/db/models/two_factor.rs

@@ -45,6 +45,8 @@ pub enum TwoFactorType {
 
     // Special type for Protected Actions verification via email
     ProtectedActions = 2000,
+    // Special type for New Device Verification via email
+    NewDeviceVerification = 2001,
 }
 
 /// Local methods
@@ -117,6 +119,21 @@ impl TwoFactor {
         }
     }
 
+    /// Atomically consume a code only if its stored content still matches what was validated.
+    /// A newer code can replace the row between the lookup and this delete.
+    pub async fn delete_if_data_matches(self, expected_data: &str, conn: &DbConn) -> Result<bool, crate::error::Error> {
+        let expected_data = expected_data.to_owned();
+        conn.run(move |conn| {
+            diesel::delete(
+                twofactor::table.filter(twofactor::uuid.eq(self.uuid)).filter(twofactor::data.eq(expected_data)),
+            )
+            .execute(conn)
+            .map(|deleted| deleted == 1)
+            .map_res("Error consuming new device verification code")
+        })
+        .await
+    }
+
     pub async fn delete(self, conn: &DbConn) -> EmptyResult {
         conn.run(move |conn| {
             diesel::delete(twofactor::table.filter(twofactor::uuid.eq(self.uuid)))

src/db/models/user.rs

@@ -72,6 +72,9 @@ pub struct User {
     pub external_id: Option<String>, // Todo: Needs to be removed in the future, this is not used anymore.
 
     pub key_id: Option<KeyId>,
+
+    /// Verify a new device via an emailed code, when `NEW_DEVICE_VERIFICATION` is enabled.
+    pub verify_devices: bool,
 }
 
 #[derive(Identifiable, Queryable, Insertable)]
@@ -159,6 +162,7 @@ impl User {
             external_id: None, // Todo: Needs to be removed in the future, this is not used anymore.
 
             key_id: None,
+            verify_devices: true,
         }
     }
 
@@ -329,6 +333,7 @@ impl User {
             "avatarColor": self.avatar_color,
             "usesKeyConnector": false,
             "creationDate": format_date(&self.created_at),
+            "verifyDevices": self.verify_devices,
             "object": "profile",
         })
     }

src/db/schema.rs

@@ -219,6 +219,7 @@ table! {
         avatar_color -> Nullable<Text>,
         external_id -> Nullable<Text>,
         key_id -> Nullable<Text>,
+        verify_devices -> Bool,
     }
 }
 

src/mail.rs

@@ -546,6 +546,30 @@ pub async fn send_recover_twofactor(address: &str, ip: &str, dt: &NaiveDateTime)
     send_email(address, &subject, body_html, body_text).await
 }
 
+/// Mails the code for an unknown device, unlike `send_new_device_logged_in`, which notifies after a login.
+pub async fn send_new_device_verification(
+    address: &str,
+    token: &str,
+    ip: &str,
+    dt: &NaiveDateTime,
+    device_type: i32,
+) -> EmptyResult {
+    let fmt = "%A, %B %_d, %Y at %r %Z";
+    let (subject, body_html, body_text) = get_text(
+        "email/new_device_verification",
+        json!({
+            "url": CONFIG.domain(),
+            "img_src": CONFIG._smtp_img_src(),
+            "token": token,
+            "ip": ip,
+            "device_type": DeviceType::from_i32(device_type).to_string(),
+            "datetime": crate::util::format_naive_datetime_local(dt, fmt),
+        }),
+    )?;
+
+    send_email(address, &subject, body_html, body_text).await
+}
+
 pub async fn send_incomplete_2fa_login(
     address: &str,
     ip: &str,

src/static/templates/email/new_device_verification.hbs

@@ -0,0 +1,12 @@
+Your Vaultwarden New Device Verification Code
+<!---------------->
+A login attempt was made from a device that has not been used with your account before. To finish logging in, enter the code below in the client that is asking for it.
+
+Your new device verification code is: {{token}}
+
+* Date: {{datetime}}
+* IP Address: {{ip}}
+* Device Type: {{device_type}}
+
+If this was not you, do not enter the code. Someone knows your master password and you should change it as soon as possible.
+{{> email/email_footer_text }}

src/static/templates/email/new_device_verification.html.hbs

@@ -0,0 +1,36 @@
+Your Vaultwarden New Device Verification Code
+<!---------------->
+{{> email/email_header }}
+<table width="100%" cellpadding="0" cellspacing="0" style="margin: 0; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; -webkit-font-smoothing: antialiased; -webkit-text-size-adjust: none;">
+   <tr style="margin: 0; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; -webkit-font-smoothing: antialiased; -webkit-text-size-adjust: none;">
+      <td class="content-block" style="font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; margin: 0; -webkit-font-smoothing: antialiased; padding: 0 0 10px; -webkit-text-size-adjust: none;" valign="top">
+         A login attempt was made from a device that has not been used with your account before. To finish logging in, enter the code below in the client that is asking for it.
+      </td>
+   </tr>
+   <tr style="margin: 0; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; -webkit-font-smoothing: antialiased; -webkit-text-size-adjust: none;">
+      <td class="content-block" style="font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; margin: 0; -webkit-font-smoothing: antialiased; padding: 0 0 10px; -webkit-text-size-adjust: none;" valign="top">
+         Your new device verification code is: <b>{{token}}</b>
+      </td>
+   </tr>
+   <tr style="margin: 0; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; -webkit-font-smoothing: antialiased; -webkit-text-size-adjust: none;">
+      <td class="content-block" style="font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; margin: 0; -webkit-font-smoothing: antialiased; padding: 0 0 10px; -webkit-text-size-adjust: none;" valign="top">
+         <b>Date:</b> {{datetime}}
+      </td>
+   </tr>
+   <tr style="margin: 0; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; -webkit-font-smoothing: antialiased; -webkit-text-size-adjust: none;">
+      <td class="content-block" style="font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; margin: 0; -webkit-font-smoothing: antialiased; padding: 0 0 10px; -webkit-text-size-adjust: none;" valign="top">
+         <b>IP Address:</b> {{ip}}
+      </td>
+   </tr>
+   <tr style="margin: 0; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; -webkit-font-smoothing: antialiased; -webkit-text-size-adjust: none;">
+      <td class="content-block" style="font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; margin: 0; -webkit-font-smoothing: antialiased; padding: 0 0 10px; -webkit-text-size-adjust: none;" valign="top">
+         <b>Device Type:</b> {{device_type}}
+      </td>
+   </tr>
+   <tr style="margin: 0; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; -webkit-font-smoothing: antialiased; -webkit-text-size-adjust: none;">
+      <td class="content-block last" style="font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; margin: 0; -webkit-font-smoothing: antialiased; padding: 0; -webkit-text-size-adjust: none;" valign="top">
+         If this was not you, do not enter the code. Someone knows your master password and you should change it as soon as possible.
+      </td>
+   </tr>
+</table>
+{{> email/email_footer }}

src/static/templates/scss/vaultwarden.scss.hbs

@@ -115,11 +115,6 @@ bit-nav-logo bit-nav-item a:before {
 bit-nav-logo bit-nav-item .bwi-shield {
   @extend %vw-hide;
 }
-/* Hide Device Login Protection button on user settings page */
-app-user-layout app-danger-zone button:nth-child(1) {
-  @extend %vw-hide;
-}
-
 /* Hide unsupported Forwarding email alias options */
 ng-dropdown-panel div.ng-dropdown-panel-items div:has(> [title="Firefox Relay"]) {
   @extend %vw-hide;