Implement V2 registration support

.typos.toml

@@ -14,9 +14,8 @@ extend-ignore-re = [
     # In SMTP it's called HELO, so ignore it
     "(?i)helo_name",
     "Server name sent during.+HELO",
-    # COSE Is short for CBOR Object Signing and Encryption, ignore these specific items
+    # COSE Is short for CBOR Object Signing and Encryption
-    "COSEKey",
+    "(?i)cose",
-    "COSEAlgorithm",
     # Ignore this specific string as it's valid
     "Ensure they are valid OTPs",
     # This word is misspelled upstream

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/2026-10-08-120000_cipher_data_longtext/up.sql

@@ -0,0 +1,3 @@
+-- A blob-encrypted cipher keeps all of its content in `data`, up to 500,000 characters, so the
+-- 64 KiB of TEXT is too small. Like upstream, which uses LONGTEXT.
+ALTER TABLE ciphers MODIFY data LONGTEXT NOT NULL;

migrations/mysql/2026-10-09-120000_user_crypto_v2/down.sql

@@ -0,0 +1,5 @@
+DROP TABLE IF EXISTS user_signature_key_pairs;
+
+ALTER TABLE users DROP COLUMN signed_public_key;
+ALTER TABLE users DROP COLUMN security_state;
+ALTER TABLE users DROP COLUMN security_version;

migrations/mysql/2026-10-09-120000_user_crypto_v2/up.sql

@@ -0,0 +1,14 @@
+ALTER TABLE users ADD COLUMN signed_public_key TEXT;
+ALTER TABLE users ADD COLUMN security_state TEXT;
+ALTER TABLE users ADD COLUMN security_version INTEGER;
+
+CREATE TABLE user_signature_key_pairs (
+    uuid                CHAR(36) NOT NULL PRIMARY KEY,
+    user_uuid           CHAR(36) NOT NULL UNIQUE,
+    signature_algorithm INTEGER  NOT NULL, -- 0 = ed25519, 1 = mldsa44
+    signing_key         TEXT     NOT NULL,
+    verifying_key       TEXT     NOT NULL,
+    created_at          DATETIME NOT NULL,
+    updated_at          DATETIME NOT NULL,
+    FOREIGN KEY (user_uuid) REFERENCES users (uuid) ON DELETE CASCADE
+);

migrations/postgresql/2026-10-08-120000_cipher_data_longtext/up.sql

@@ -0,0 +1 @@
+-- TEXT has no size limit here, only MySQL needed the change

migrations/postgresql/2026-10-09-120000_user_crypto_v2/down.sql

@@ -0,0 +1,5 @@
+DROP TABLE IF EXISTS user_signature_key_pairs;
+
+ALTER TABLE users DROP COLUMN signed_public_key;
+ALTER TABLE users DROP COLUMN security_state;
+ALTER TABLE users DROP COLUMN security_version;

migrations/postgresql/2026-10-09-120000_user_crypto_v2/up.sql

@@ -0,0 +1,13 @@
+ALTER TABLE users ADD COLUMN signed_public_key TEXT;
+ALTER TABLE users ADD COLUMN security_state TEXT;
+ALTER TABLE users ADD COLUMN security_version INTEGER;
+
+CREATE TABLE user_signature_key_pairs (
+    uuid                CHAR(36) NOT NULL PRIMARY KEY,
+    user_uuid           CHAR(36) NOT NULL UNIQUE REFERENCES users (uuid) ON DELETE CASCADE,
+    signature_algorithm INTEGER  NOT NULL, -- 0 = ed25519, 1 = mldsa44
+    signing_key         TEXT     NOT NULL,
+    verifying_key       TEXT     NOT NULL,
+    created_at          TIMESTAMP NOT NULL,
+    updated_at          TIMESTAMP NOT NULL
+);

migrations/sqlite/2026-10-08-120000_cipher_data_longtext/up.sql

@@ -0,0 +1 @@
+-- TEXT has no size limit here, only MySQL needed the change

migrations/sqlite/2026-10-09-120000_user_crypto_v2/down.sql

@@ -0,0 +1,5 @@
+DROP TABLE IF EXISTS user_signature_key_pairs;
+
+ALTER TABLE users DROP COLUMN signed_public_key;
+ALTER TABLE users DROP COLUMN security_state;
+ALTER TABLE users DROP COLUMN security_version;

migrations/sqlite/2026-10-09-120000_user_crypto_v2/up.sql

@@ -0,0 +1,13 @@
+ALTER TABLE users ADD COLUMN signed_public_key TEXT;
+ALTER TABLE users ADD COLUMN security_state TEXT;
+ALTER TABLE users ADD COLUMN security_version INTEGER;
+
+CREATE TABLE user_signature_key_pairs (
+    uuid                TEXT     NOT NULL PRIMARY KEY,
+    user_uuid           TEXT     NOT NULL UNIQUE REFERENCES users (uuid) ON DELETE CASCADE,
+    signature_algorithm INTEGER  NOT NULL, -- 0 = ed25519, 1 = mldsa44
+    signing_key         TEXT     NOT NULL,
+    verifying_key       TEXT     NOT NULL,
+    created_at          DATETIME NOT NULL,
+    updated_at          DATETIME NOT NULL
+);

src/api/core/accounts.rs

@@ -22,8 +22,8 @@ use crate::{
         models::{
             AuthRequest, AuthRequestId, Cipher, CipherId, Device, DeviceId, DeviceType, DeviceWithAuthRequest,
             EmergencyAccess, EmergencyAccessId, EventType, Folder, FolderId, Invitation, KeyId, Membership,
-            MembershipId, OrgPolicy, OrgPolicyType, Organization, OrganizationId, Send, SendId, User, UserId,
+            MembershipId, OrgPolicy, OrgPolicyType, Organization, OrganizationId, Send, SendId, SignatureAlgorithm,
-            UserKdfType,
+            User, UserId, UserKdfType, UserSignatureKeyPair,
         },
     },
     mail,
@@ -42,6 +42,7 @@ pub fn routes() -> Vec<rocket::Route> {
         post_profile,
         put_avatar,
         get_public_keys,
+        get_account_public_keys,
         get_keys,
         post_keys,
         post_password,
@@ -113,6 +114,9 @@ pub struct RegisterData {
     #[serde(alias = "userAsymmetricKeys")]
     keys: Option<KeysData>,
 
+    // Supersedes `keys`, and the only way a v2 account can be registered.
+    account_keys: Option<AccountKeysData>,
+
     master_password_hint: Option<String>,
 
     organization_user_id: Option<MembershipId>,
@@ -124,36 +128,6 @@ pub struct RegisterData {
     org_invite_token: Option<String>,
 }
 
-impl RegisterData {
-    fn hash(&self) -> String {
-        self.compat.fold(|rdc| &rdc.master_password_hash, |rdcu| &rdcu.master_password_authentication.hash).to_owned()
-    }
-
-    fn kdf(&self) -> &KDFData {
-        self.compat.fold(|rdc| &rdc.kdf, |rdcu| &rdcu.master_password_authentication.kdf)
-    }
-
-    fn key(&self) -> String {
-        self.compat.fold(|rdc| &rdc.key, |rdcu| &rdcu.master_password_unlock.key).to_owned()
-    }
-
-    // When comparing with salt, email need to be normalized:
-    //  - https://github.com/bitwarden/clients/blob/web-v2026.5.0/libs/common/src/key-management/master-password/services/master-password.service.ts#L171
-    fn unprocessable(&self) -> bool {
-        let mut unprocessable = false;
-        *self.compat.fold(
-            |_| &false,
-            |rdcu| {
-                let email = self.email.trim().to_lowercase();
-                unprocessable = rdcu.master_password_authentication.kdf != rdcu.master_password_unlock.kdf
-                    || rdcu.master_password_authentication.salt != email
-                    || rdcu.master_password_unlock.salt != email;
-                &unprocessable
-            },
-        )
-    }
-}
-
 #[derive(Debug, Deserialize)]
 struct RegisterDataOld {
     #[serde(flatten)]
@@ -193,6 +167,42 @@ impl RegisterDataCompat {
             RegisterDataCompat::RegisterDataCur(rdcu) => fcu(rdcu),
         }
     }
+
+    fn hash(&self) -> String {
+        self.fold(|rdc| &rdc.master_password_hash, |rdcu| &rdcu.master_password_authentication.hash).to_owned()
+    }
+
+    fn kdf(&self) -> &KDFData {
+        self.fold(|rdc| &rdc.kdf, |rdcu| &rdcu.master_password_authentication.kdf)
+    }
+
+    fn key(&self) -> String {
+        self.fold(|rdc| &rdc.key, |rdcu| &rdcu.master_password_unlock.key).to_owned()
+    }
+
+    /// The id of the user key, which only the current format carries.
+    fn key_id(&self) -> Option<KeyId> {
+        match self {
+            RegisterDataCompat::RegisterDataOld(_) => None,
+            RegisterDataCompat::RegisterDataCur(rdcu) => rdcu.master_password_unlock.contained_key_id.clone(),
+        }
+    }
+
+    // When comparing with salt, email need to be normalized:
+    //  - https://github.com/bitwarden/clients/blob/web-v2026.5.0/libs/common/src/key-management/master-password/services/master-password.service.ts#L171
+    fn unprocessable(&self, email: &str) -> bool {
+        let mut unprocessable = false;
+        *self.fold(
+            |_| &false,
+            |rdcu| {
+                let email = email.trim().to_lowercase();
+                unprocessable = rdcu.master_password_authentication.kdf != rdcu.master_password_unlock.kdf
+                    || rdcu.master_password_authentication.salt != email
+                    || rdcu.master_password_unlock.salt != email;
+                &unprocessable
+            },
+        )
+    }
 }
 
 #[derive(Debug, Deserialize)]
@@ -202,6 +212,198 @@ struct KeysData {
     public_key: String,
 }
 
+/// Upstream's implicit `[Required]` on a non-nullable string: present and not blank.
+fn required(value: Option<String>, field: &str) -> ApiResult<String> {
+    match value {
+        Some(value) if !value.trim().is_empty() => Ok(value),
+        _ => err!(format!("The {field} field is required.")),
+    }
+}
+
+/// The `accountKeys` payload: a v1 key pair, or v2 with a signature key pair and security state.
+///
+/// Ref: <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Core/KeyManagement/Models/Api/Request/AccountKeysRequestModel.cs#L6-L50>
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct AccountKeysData {
+    // Required like upstream, but only used without `public_key_encryption_key_pair`
+    user_key_encrypted_account_private_key: Option<String>,
+    account_public_key: Option<String>,
+
+    public_key_encryption_key_pair: Option<PublicKeyEncryptionKeyPairData>,
+    signature_key_pair: Option<SignatureKeyPairData>,
+    security_state: Option<SecurityStateData>,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct PublicKeyEncryptionKeyPairData {
+    wrapped_private_key: String,
+    public_key: String,
+    signed_public_key: Option<String>,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct SignatureKeyPairData {
+    signature_algorithm: String,
+    wrapped_signing_key: String,
+    verifying_key: String,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct SecurityStateData {
+    security_state: String,
+    security_version: i32,
+}
+
+struct ValidatedAccountKeys {
+    private_key: String,
+    public_key: String,
+    v2: Option<ValidatedV2AccountKeys>,
+}
+
+struct ValidatedV2AccountKeys {
+    signed_public_key: String,
+    signing_key: String,
+    verifying_key: String,
+    signature_algorithm: SignatureAlgorithm,
+    security_state: String,
+    security_version: i32,
+}
+
+impl AccountKeysData {
+    /// Upstream's model checks, plus the v2 fields all or none: no client can unlock a partial v2 state.
+    fn validate(self) -> ApiResult<ValidatedAccountKeys> {
+        let top_private_key =
+            required(self.user_key_encrypted_account_private_key, "UserKeyEncryptedAccountPrivateKey")?;
+        let top_public_key = required(self.account_public_key, "AccountPublicKey")?;
+        let (private_key, public_key, signed_public_key) = match self.public_key_encryption_key_pair {
+            Some(key_pair) => (
+                required(Some(key_pair.wrapped_private_key), "WrappedPrivateKey")?,
+                required(Some(key_pair.public_key), "PublicKey")?,
+                key_pair.signed_public_key,
+            ),
+            // Older clients only send the top-level fields, which are always v1
+            None => (top_private_key, top_public_key, None),
+        };
+
+        if let Some(signature_key_pair) = &self.signature_key_pair {
+            required(Some(signature_key_pair.signature_algorithm.clone()), "SignatureAlgorithm")?;
+            required(Some(signature_key_pair.wrapped_signing_key.clone()), "WrappedSigningKey")?;
+            required(Some(signature_key_pair.verifying_key.clone()), "VerifyingKey")?;
+        }
+        if let Some(security_state) = &self.security_state {
+            required(Some(security_state.security_state.clone()), "SecurityState")?;
+            if security_state.security_state.encode_utf16().count() > 10_000 {
+                err!("The field SecurityState must be a string with a maximum length of 10000.")
+            }
+        }
+
+        let v2 = match (signed_public_key, self.signature_key_pair, self.security_state) {
+            (Some(signed_public_key), Some(signature_key_pair), Some(security_state)) => {
+                // Upstream fails on a null one, but takes an empty one that no client can unlock with
+                let signed_public_key = required(Some(signed_public_key), "SignedPublicKey")?;
+                let Some(signature_algorithm) = SignatureAlgorithm::parse(&signature_key_pair.signature_algorithm)
+                else {
+                    err!(format!(
+                        "Unsupported signature algorithm: {}",
+                        signature_key_pair.signature_algorithm.escape_debug()
+                    ))
+                };
+
+                Some(ValidatedV2AccountKeys {
+                    signed_public_key,
+                    signing_key: signature_key_pair.wrapped_signing_key,
+                    verifying_key: signature_key_pair.verifying_key,
+                    signature_algorithm,
+                    security_state: security_state.security_state,
+                    security_version: security_state.security_version,
+                })
+            }
+            (None, None, None) => None,
+            _ => err!(
+                "Invalid account keys: the signed public key, signature key pair and security state must either all be present or all be absent"
+            ),
+        };
+
+        Ok(ValidatedAccountKeys {
+            private_key,
+            public_key,
+            v2,
+        })
+    }
+}
+
+impl From<KeysData> for ValidatedAccountKeys {
+    fn from(keys: KeysData) -> Self {
+        Self {
+            private_key: keys.encrypted_private_key,
+            public_key: keys.public_key,
+            v2: None,
+        }
+    }
+}
+
+impl ValidatedAccountKeys {
+    /// The keys of a registration: `accountKeys` only for a v2 account, like upstream.
+    ///
+    /// Ref: <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Core/Auth/Models/Api/Request/Accounts/RegisterFinishRequestModel.cs#L77-L100>
+    fn for_registration(account_keys: Option<AccountKeysData>, keys: Option<KeysData>) -> ApiResult<Self> {
+        if let Some(account_keys) = account_keys {
+            let account_keys = account_keys.validate()?;
+            if account_keys.is_v2() {
+                return Ok(account_keys);
+            }
+        }
+        let Some(keys) = keys else {
+            err!("PublicKey and WrappedPrivateKey not found in RequestModel")
+        };
+        Ok(keys.into())
+    }
+
+    fn is_v2(&self) -> bool {
+        self.v2.is_some()
+    }
+
+    /// Sets the keys on the user, which then needs saving before [`Self::save_signature_key_pair`].
+    fn apply(&self, user: &mut User) -> EmptyResult {
+        user.private_key = Some(self.private_key.clone());
+        user.public_key = Some(self.public_key.clone());
+
+        user.signed_public_key = self.v2.as_ref().map(|v2| v2.signed_public_key.clone());
+        user.security_state = self.v2.as_ref().map(|v2| v2.security_state.clone());
+        user.security_version = self.v2.as_ref().map(|v2| v2.security_version);
+
+        Ok(())
+    }
+
+    /// Saves the signature key pair, which needs the user to exist for its foreign key.
+    async fn save_signature_key_pair(&self, user_id: &UserId, conn: &DbConn) -> EmptyResult {
+        // Skip if the account is v1, since v1 accounts don't have a signature key pair.
+        let Some(v2) = &self.v2 else {
+            return Ok(());
+        };
+
+        let mut key_pair = match UserSignatureKeyPair::find_by_user(user_id, conn).await {
+            Some(mut key_pair) => {
+                key_pair.signature_algorithm = v2.signature_algorithm as i32;
+                key_pair.signing_key.clone_from(&v2.signing_key);
+                key_pair.verifying_key.clone_from(&v2.verifying_key);
+                key_pair
+            }
+            None => UserSignatureKeyPair::new(
+                user_id.clone(),
+                v2.signature_algorithm,
+                v2.signing_key.clone(),
+                v2.verifying_key.clone(),
+            ),
+        };
+        key_pair.save(conn).await
+    }
+}
+
 #[derive(Debug, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct MasterPasswordAuthentication {
@@ -222,17 +424,19 @@ pub struct MasterPasswordUnlock {
 
     #[serde(alias = "masterKeyWrappedUserKey")]
     key: String,
+    contained_key_id: Option<KeyId>,
 }
 
 #[derive(Debug, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct SetPasswordData {
     #[serde(flatten)]
-    kdf: KDFData,
+    compat: RegisterDataCompat,
 
-    key: String,
     keys: Option<KeysData>,
-    master_password_hash: String,
+    // Supersedes `keys`, and the only way a v2 account can be initialized here.
+    account_keys: Option<AccountKeysData>,
+
     master_password_hint: Option<String>,
     org_identifier: Option<String>,
 }
@@ -274,7 +478,7 @@ pub async fn register(data: Json<RegisterData>, conn: DbConn) -> JsonResult {
     let mut name = None;
     let mut pending_emergency_access = None;
 
-    if data.unprocessable() {
+    if data.compat.unprocessable(&data.email) {
         err_code!("Unexpected RegisterData format", Status::UnprocessableEntity.code);
     }
 
@@ -343,10 +547,11 @@ pub async fn register(data: Json<RegisterData>, conn: DbConn) -> JsonResult {
         err!("The field Name must be a string with a maximum length of 50.");
     }
 
-    // Check against the password hint setting here so if it fails, the user
+    // Check against the password hint setting and the keys here so if they fail,
-    // can retry without losing their invitation below.
+    // the user can retry without losing their invitation below.
     let password_hint = clean_password_hint(data.master_password_hint.as_ref());
     enforce_password_hint_setting(password_hint.as_ref())?;
+    let account_keys = ValidatedAccountKeys::for_registration(data.account_keys, data.keys)?;
 
     let mut user = match User::find_by_mail(&email, &conn).await {
         Some(user) => {
@@ -393,9 +598,9 @@ pub async fn register(data: Json<RegisterData>, conn: DbConn) -> JsonResult {
     // Make sure we don't leave a lingering invitation.
     Invitation::take(&email, &conn).await;
 
-    set_kdf_data(&mut user, data.kdf())?;
+    set_kdf_data(&mut user, data.compat.kdf())?;
 
-    user.set_password(&data.hash(), Some(data.key()), true, None, &conn).await?;
+    user.set_password(&data.compat.hash(), Some(data.compat.key()), true, None, &conn).await?;
     user.password_hint = password_hint;
 
     // Add extra fields if present
@@ -403,9 +608,10 @@ pub async fn register(data: Json<RegisterData>, conn: DbConn) -> JsonResult {
         user.name = name;
     }
 
-    if let Some(keys) = data.keys {
+    account_keys.apply(&mut user)?;
-        user.private_key = Some(keys.encrypted_private_key);
+    // Like upstream, only a v2 registration records the key id; v1 accounts report it through `user-key-id`
-        user.public_key = Some(keys.public_key);
+    if account_keys.is_v2() {
+        user.key_id = data.compat.key_id();
     }
 
     if email_verified {
@@ -428,6 +634,7 @@ pub async fn register(data: Json<RegisterData>, conn: DbConn) -> JsonResult {
     }
 
     user.save(&conn).await?;
+    account_keys.save_signature_key_pair(&user.uuid, &conn).await?;
 
     // accept any open emergency access invitations
     if !CONFIG.mail_enabled() && CONFIG.emergency_access_allowed() {
@@ -441,25 +648,81 @@ pub async fn register(data: Json<RegisterData>, conn: DbConn) -> JsonResult {
     })))
 }
 
+/// Upstream's shape checks of the set-password body, on the raw JSON that the untagged compat would hide.
+///
+/// Ref: <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Api/Auth/Models/Request/Accounts/SetInitialPasswordRequestModel.cs#L75-L106>
+fn validate_set_password_shape(body: &Value) -> EmptyResult {
+    let has = |name: &str| {
+        body.as_object().is_some_and(|o| o.iter().any(|(k, v)| k.eq_ignore_ascii_case(name) && !v.is_null()))
+    };
+
+    if has("accountKeys") && has("keys") {
+        err!("Cannot specify both AccountKeys and Keys. Provide exactly one keypair.")
+    }
+    let (authentication, unlock) = (has("masterPasswordAuthentication"), has("masterPasswordUnlock"));
+    if authentication != unlock {
+        err!(
+            "Must provide both MasterPasswordAuthentication and MasterPasswordUnlock together. Cannot provide one without the other."
+        )
+    }
+    if authentication && (has("masterPasswordHash") || has("key") || has("kdf")) {
+        err!(
+            "Cannot mix modern (MasterPasswordAuthentication/MasterPasswordUnlock) and legacy (MasterPasswordHash/Key/Kdf) fields. Provide one shape or the other."
+        )
+    }
+    Ok(())
+}
+
 #[post("/accounts/set-password", data = "<data>")]
-async fn post_set_password(data: Json<SetPasswordData>, headers: Headers, conn: DbConn) -> JsonResult {
+async fn post_set_password(data: Json<Value>, headers: Headers, conn: DbConn) -> JsonResult {
-    let data: SetPasswordData = data.into_inner();
+    let data = data.into_inner();
+    validate_set_password_shape(&data)?;
+    let Ok(data) = serde_json::from_value::<SetPasswordData>(data) else {
+        err_code!("Unexpected SetPasswordData format", Status::UnprocessableEntity.code)
+    };
+    if data.master_password_hint.as_ref().is_some_and(|h| h.encode_utf16().count() > 50) {
+        err!("The field MasterPasswordHint must be a string with a maximum length of 50.")
+    }
     let mut user = headers.user;
 
     if user.private_key.is_some() || !user.password_hash.is_empty() {
         err!("Account already initialized, cannot set password")
     }
 
+    if data.compat.unprocessable(&user.email) {
+        err_code!("Unexpected SetPasswordData format", Status::UnprocessableEntity.code);
+    }
+
     // Check against the password hint setting here so if it fails,
     // the user can retry without losing their invitation below.
     let password_hint = clean_password_hint(data.master_password_hint.as_ref());
     enforce_password_hint_setting(password_hint.as_ref())?;
 
-    set_kdf_data(&mut user, &data.kdf)?;
+    // Like upstream, `accountKeys` only through the v2 JIT flow
+    // Ref: <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Api/Auth/Controllers/AccountsController.cs#L314-L359>
+    let account_keys = match data.account_keys {
+        Some(account_keys) => {
+            if !matches!(data.compat, RegisterDataCompat::RegisterDataCur(_))
+                || !crate::util::is_client_feature_flag_enabled(
+                    "enable-account-encryption-v2-jit-password-registration",
+                )
+            {
+                err!("Request includes V2 AccountKeys but V2 encryption is not enabled.")
+            }
+            let account_keys = account_keys.validate()?;
+            if !account_keys.is_v2() {
+                err!("AccountKeys are only supported for V2 encryption.")
+            }
+            Some(account_keys)
+        }
+        None => data.keys.map(ValidatedAccountKeys::from),
+    };
+
+    set_kdf_data(&mut user, data.compat.kdf())?;
 
     user.set_password(
-        &data.master_password_hash,
+        &data.compat.hash(),
-        Some(data.key),
+        Some(data.compat.key()),
         false,
         Some(vec![String::from("revision_date")]), // We need to allow revision-date to use the old security_timestamp
         &conn,
@@ -467,9 +730,12 @@ async fn post_set_password(data: Json<SetPasswordData>, headers: Headers, conn:
     .await?;
     user.password_hint = password_hint;
 
-    if let Some(keys) = data.keys {
+    if let Some(ref account_keys) = account_keys {
-        user.private_key = Some(keys.encrypted_private_key);
+        account_keys.apply(&mut user)?;
-        user.public_key = Some(keys.public_key);
+        // As in `register`, only a v2 account records the user key id here
+        if account_keys.is_v2() {
+            user.key_id = data.compat.key_id();
+        }
     }
 
     if let Some(identifier) = data.org_identifier
@@ -497,6 +763,10 @@ async fn post_set_password(data: Json<SetPasswordData>, headers: Headers, conn:
 
     user.save(&conn).await?;
 
+    if let Some(account_keys) = account_keys {
+        account_keys.save_signature_key_pair(&user.uuid, &conn).await?;
+    }
+
     Ok(Json(json!({
       "object": "set-password",
     })))
@@ -577,8 +847,19 @@ async fn get_public_keys(user_id: UserId, _headers: Headers, conn: DbConn) -> Js
     })))
 }
 
+#[get("/users/<user_id>/keys")]
+async fn get_account_public_keys(user_id: UserId, _headers: Headers, conn: DbConn) -> JsonResult {
+    let user = match User::find_by_uuid(&user_id, &conn).await {
+        Some(user) if user.public_key.is_some() => user,
+        Some(_) => err_code!("User has no public_key", Status::NotFound.code),
+        None => err_code!("User doesn't exist", Status::NotFound.code),
+    };
+
+    Ok(Json(user.public_keys_json(&conn).await))
+}
+
 #[get("/accounts/keys")]
-fn get_keys(headers: Headers) -> JsonResult {
+async fn get_keys(headers: Headers, conn: DbConn) -> JsonResult {
     let user = headers.user;
 
     // The SDK reads a 404 as the user having no key pair yet
@@ -590,29 +871,66 @@ fn get_keys(headers: Headers) -> JsonResult {
         "key": (!user.akey.is_empty()).then_some(&user.akey),
         "publicKey": user.public_key,
         "privateKey": user.private_key,
-        "accountKeys": user.account_keys_json(),
+        "accountKeys": user.account_keys_json(&conn).await,
         "object": "keys",
     })))
 }
 
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct PostKeysData {
+    // Required like upstream, even next to `accountKeys`
+    public_key: Option<String>,
+    encrypted_private_key: Option<String>,
+    account_keys: Option<AccountKeysData>,
+    // The id of the user key these account keys belong to, only honored for v2 `accountKeys`
+    user_key_id: Option<KeyId>,
+}
+
 #[post("/accounts/keys", data = "<data>")]
-async fn post_keys(data: Json<KeysData>, headers: Headers, conn: DbConn) -> JsonResult {
+async fn post_keys(data: Json<PostKeysData>, headers: Headers, conn: DbConn) -> JsonResult {
-    let data: KeysData = data.into_inner();
+    let data: PostKeysData = data.into_inner();
 
     let mut user = headers.user;
 
+    // Only for an account without keys, replacing them is what a key rotation does
     if user.private_key.is_some() || user.public_key.is_some() {
         err!("User has existing keypair")
     }
 
-    user.private_key = Some(data.encrypted_private_key);
+    // Ref: <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Core/Auth/Models/Api/Request/Accounts/KeysRequestModel.cs#L11-L19>
-    user.public_key = Some(data.public_key);
+    let public_key = required(data.public_key, "PublicKey")?;
+    let encrypted_private_key = required(data.encrypted_private_key, "EncryptedPrivateKey")?;
 
+    // `accountKeys` supersedes the flat keys when both are sent
+    let account_keys = match data.account_keys {
+        Some(account_keys) => {
+            let account_keys = account_keys.validate()?;
+            if !account_keys.is_v2() {
+                err!("AccountKeys are only supported for V2 encryption.")
+            }
+            // A client that predates key ids sends none, and reports it later through `user-key-id`
+            if data.user_key_id.is_some() {
+                user.key_id = data.user_key_id;
+            }
+            account_keys
+        }
+        None => KeysData {
+            encrypted_private_key,
+            public_key,
+        }
+        .into(),
+    };
+
+    account_keys.apply(&mut user)?;
     user.save(&conn).await?;
+    account_keys.save_signature_key_pair(&user.uuid, &conn).await?;
 
     Ok(Json(json!({
+        "key": (!user.akey.is_empty()).then_some(&user.akey),
         "privateKey": user.private_key,
         "publicKey": user.public_key,
+        "accountKeys": user.account_keys_json(&conn).await,
         "object":"keys"
     })))
 }
@@ -651,6 +969,8 @@ async fn post_password(data: Json<ChangePassData>, headers: Headers, conn: DbCon
                 err!("Invalid master password salt")
             }
 
+            validate_key_id_unchanged(&user, &unlock_data)?;
+
             (authentication_data.master_password_authentication_hash, unlock_data.master_key_wrapped_user_key)
         } else if let (Some(new_master_password_hash), Some(new_key)) = (data.new_master_password_hash, data.key) {
             (new_master_password_hash, new_key)
@@ -753,6 +1073,19 @@ pub(super) struct UnlockData {
     salt: String,
     kdf: KDFData,
     pub(super) master_key_wrapped_user_key: String,
+    contained_key_id: Option<KeyId>,
+}
+
+/// A password or KDF change keeps the user key, so its key id must be the current one, when both are known.
+///
+/// Ref: <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Core/KeyManagement/Models/Data/MasterPasswordUnlockData.cs#L27-L47>
+fn validate_key_id_unchanged(user: &User, unlock_data: &UnlockData) -> EmptyResult {
+    if let (Some(current), Some(contained)) = (&user.key_id, &unlock_data.contained_key_id)
+        && current != contained
+    {
+        err!("Invalid user key sent in master-password unlock data.")
+    }
+    Ok(())
 }
 
 #[derive(Deserialize)]
@@ -773,6 +1106,8 @@ async fn post_kdf(data: Json<ChangeKdfData>, headers: Headers, conn: DbConn, nt:
 
     data.authentication_data.check(&headers.user, &data.unlock_data)?;
 
+    validate_key_id_unchanged(&headers.user, &data.unlock_data)?;
+
     let mut user = headers.user;
 
     set_kdf_data(&mut user, &data.unlock_data.kdf)?;
@@ -948,6 +1283,14 @@ async fn post_rotatekey(data: Json<KeyData>, headers: Headers, conn: DbConn, nt:
         err!("Invalid password")
     }
 
+    // Rotating v2 keys, or upgrading to them, would leave an account that can't be unlocked here
+    if headers.user.is_v2() {
+        err!("Key rotation is not supported for v2 accounts")
+    }
+    if !data.account_keys.user_key_encrypted_account_private_key.starts_with("2.") {
+        err!("The provided account private key was not wrapped with AES-256-CBC-HMAC")
+    }
+
     // Validate the import before continuing
     // Bitwarden does not process the import if there is one item invalid.
     // Since we check for the size of the encrypted note length, we need to do that here to pre-validate it.
@@ -1073,8 +1416,9 @@ struct KeyIdData {
 #[post("/accounts/key-management/user-key-id", data = "<data>")]
 async fn post_user_key(data: Json<KeyIdData>, headers: Headers, conn: DbConn) -> EmptyResult {
     let mut user = headers.user;
+    // Only a backfill for accounts that have none. Afterwards the id changes with the key, in a rotation.
     if user.key_id.is_some() {
-        err_code!("Unexpected data", Status::UnprocessableEntity.code);
+        err!("User key id is already set.")
     }
 
     user.key_id = Some(data.into_inner().user_key_id);
@@ -1932,10 +2276,10 @@ mod tests {
         )
         .unwrap();
 
-        assert!(!data.unprocessable());
+        assert!(!data.compat.unprocessable(&data.email));
-        assert_eq!(data.hash(), "hash");
+        assert_eq!(data.compat.hash(), "hash");
-        assert_eq!(data.key(), "key");
+        assert_eq!(data.compat.key(), "key");
-        assert_eq!(data.kdf().kdf_iterations, 600_000);
+        assert_eq!(data.compat.kdf().kdf_iterations, 600_000);
         assert!(data.keys.is_some());
         assert_eq!(data.email_verification_token.as_deref(), Some("token"));
     }
@@ -1957,10 +2301,10 @@ mod tests {
         )
         .unwrap();
 
-        assert!(!data.unprocessable());
+        assert!(!data.compat.unprocessable(&data.email));
-        assert_eq!(data.hash(), "hash");
+        assert_eq!(data.compat.hash(), "hash");
-        assert_eq!(data.key(), "key");
+        assert_eq!(data.compat.key(), "key");
-        assert_eq!(data.kdf().kdf_iterations, 600_000);
+        assert_eq!(data.compat.kdf().kdf_iterations, 600_000);
         assert!(data.keys.is_some());
     }
 }

src/api/core/ciphers.rs

@@ -23,7 +23,8 @@ use crate::{
         models::{
             Archive, Attachment, AttachmentId, Cipher, CipherId, Collection, CollectionCipher, CollectionGroup,
             CollectionId, CollectionUser, EventType, Favorite, Folder, FolderCipher, FolderId, Group, KeyId,
-            Membership, MembershipType, OrgPolicy, OrgPolicyType, OrganizationId, RepromptType, Send, UserId,
+            Membership, MembershipType, OrgPolicy, OrgPolicyType, OrganizationId, RepromptType, Send, User, UserId,
+            is_data_blob_encrypted,
         },
     },
     util::{NumberOrString, deser_opt_nonempty_str, save_temp_file},
@@ -189,12 +190,19 @@ async fn sync(data: SyncData, headers: Headers, client_version: Option<ClientVer
             // https://github.com/bitwarden/android/blob/release/2025.12-rc41/network/src/main/kotlin/com/bitwarden/network/model/MasterPasswordUnlockDataJson.kt#L22-L26
             "masterKeyEncryptedUserKey": headers.user.akey,
             "masterKeyWrappedUserKey": headers.user.akey,
-            "salt": headers.user.email
+            "salt": headers.user.email,
+            "containedKeyId": headers.user.key_id,
         })
     } else {
         Value::Null
     };
 
+    // Upstream omits these when unset rather than sending null
+    let mut user_decryption = json!({ "masterPasswordUnlock": master_password_unlock });
+    if let Some(key_id) = &headers.user.key_id {
+        user_decryption["userKeyId"] = json!(key_id);
+    }
+
     Ok(Json(json!({
         "profile": user_json,
         "folders": folders_json,
@@ -204,10 +212,7 @@ async fn sync(data: SyncData, headers: Headers, client_version: Option<ClientVer
         "ciphers": ciphers_json,
         "domains": domains_json,
         "sends": sends_json,
-        "userDecryption": {
+        "userDecryption": user_decryption,
-            "masterPasswordUnlock": master_password_unlock,
-            "userKeyId": headers.user.key_id,
-        },
         "object": "sync"
     })))
 }
@@ -269,7 +274,8 @@ pub struct CipherData {
 
     key: Option<String>,
 
-    pub encrypted_for: UserId, // Added in web-v2025.6.0
+    // Added in web-v2025.6.0. Deprecated upstream for `encrypted_by_key_id`, but still checked when sent
+    pub encrypted_for: Option<UserId>,
     // Added in web-v2025.8.1, Optional for compat
     pub encrypted_by_key_id: Option<KeyId>,
 
@@ -284,7 +290,8 @@ pub struct CipherData {
     Passport = 8
     */
     pub r#type: i32,
-    pub name: String,
+    // Absent on a blob-encrypted cipher, whose name is sealed inside `data`
+    pub name: Option<String>,
     pub notes: Option<String>,
     fields: Option<Value>,
 
@@ -298,6 +305,9 @@ pub struct CipherData {
     drivers_license: Option<Value>,
     passport: Option<Value>,
 
+    // The sealed blob of a v2 account's cipher, which replaces all of the fields above
+    data: Option<String>,
+
     favorite: Option<bool>,
     reprompt: Option<i32>,
 
@@ -319,6 +329,79 @@ pub struct CipherData {
     archived_date: Option<String>,
 }
 
+/// A field of a [`CipherData`] that fails upstream's model validation.
+#[derive(Debug)]
+pub struct CipherValidationError {
+    pub field: &'static str,
+    pub message: String,
+}
+
+impl From<CipherValidationError> for crate::Error {
+    fn from(e: CipherValidationError) -> Self {
+        Self::new_msg(e.message)
+    }
+}
+
+/// The cipher must have been encrypted for the acting user. Only checked when the client sends the field.
+///
+/// Ref: <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Api/Vault/Controllers/CiphersController.cs#L1857-L1870>
+fn validate_encrypted_for_user(data: &CipherData, user_id: &UserId) -> EmptyResult {
+    if data.encrypted_for.as_ref().is_some_and(|encrypted_for| encrypted_for != user_id) {
+        err!("Cipher was not encrypted for the current user. Please try again.")
+    }
+    Ok(())
+}
+
+/// [`validate_encrypted_for_user`], plus the key id of a user-owned cipher, when both ids are known.
+///
+/// Ref: <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Api/Vault/Controllers/CiphersController.cs#L1886-L1911>
+fn validate_encrypted_by_user(data: &CipherData, user: &User, is_org_cipher: bool) -> EmptyResult {
+    validate_encrypted_for_user(data, &user.uuid)?;
+
+    if !is_org_cipher
+        && let (Some(cipher_key_id), Some(user_key_id)) = (&data.encrypted_by_key_id, &user.key_id)
+        && cipher_key_id != user_key_id
+    {
+        err!("Cipher was not encrypted with the current user key. Please try again.")
+    }
+    Ok(())
+}
+
+/// Upstream's `[StringLength(500000)]` on `CipherRequestModel.Data`
+const MAX_CIPHER_DATA_LENGTH: usize = 500_000;
+
+impl CipherData {
+    /// Whether `data` is a blob rather than the per-type fields. Parses `data`, so keep the result.
+    pub fn is_blob(&self) -> bool {
+        self.data.as_deref().is_some_and(is_data_blob_encrypted)
+    }
+
+    /// Upstream's model checks that depend on the format: the size of `data`, and a name unless it's a blob.
+    ///
+    /// Ref: <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Api/Vault/Models/Request/CipherRequestModel.cs#L76-L77>
+    /// and <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Api/Vault/Models/Request/CipherRequestModel.cs#L91-L99>
+    pub fn validate_content(&self, is_blob: bool) -> Result<(), CipherValidationError> {
+        if let Some(data) = &self.data
+            && data.len() > MAX_CIPHER_DATA_LENGTH
+        {
+            return Err(CipherValidationError {
+                field: "Data",
+                message: format!("The field Data must be a string with a maximum length of {MAX_CIPHER_DATA_LENGTH}."),
+            });
+        }
+
+        // A blob carries the name inside it, so only the other formats need one
+        if !is_blob && self.name.as_deref().is_none_or(|n| n.trim().is_empty()) {
+            return Err(CipherValidationError {
+                field: "Name",
+                message: String::from("The Name field is required."),
+            });
+        }
+
+        Ok(())
+    }
+}
+
 #[derive(Debug, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct PartialCipherData {
@@ -352,16 +435,14 @@ async fn post_ciphers_create(
 ) -> JsonResult {
     let mut data: ShareCipherData = data.into_inner();
 
-    if data.cipher.encrypted_for != headers.user.uuid {
+    validate_encrypted_by_user(&data.cipher, &headers.user, data.cipher.organization_id.is_some())?;
-        err_code!("Invalid user cipher", Status::UnprocessableEntity.code);
-    }
 
     // This check is usually only needed in update_cipher_from_data(), but we
     // need it here as well to avoid creating an empty cipher in the call to
     // cipher.save() below.
     enforce_personal_ownership_policy(Some(&data.cipher), &headers, &conn).await?;
 
-    let mut cipher = Cipher::new(data.cipher.r#type, data.cipher.name.clone());
+    let mut cipher = Cipher::new(data.cipher.r#type);
     cipher.user_uuid = Some(headers.user.uuid.clone());
     cipher.save(&conn).await?;
 
@@ -385,16 +466,7 @@ async fn post_ciphers_create(
 async fn post_ciphers(data: Json<CipherData>, headers: Headers, conn: DbConn, nt: Notify<'_>) -> JsonResult {
     let mut data: CipherData = data.into_inner();
 
-    if data.encrypted_for != headers.user.uuid {
+    validate_encrypted_by_user(&data, &headers.user, data.organization_id.is_some())?;
-        err_code!("Invalid user cipher", Status::UnprocessableEntity.code);
-    }
-
-    if let Some(cipher_key_id) = &data.encrypted_by_key_id
-        && let Some(user_key_id) = &headers.user.key_id
-        && cipher_key_id != user_key_id
-    {
-        err_code!("Invalid key cipher", Status::UnprocessableEntity.code);
-    }
 
     // The web/browser clients set this field to null as expected, but the
     // mobile clients seem to set the invalid value `0001-01-01T00:00:00`,
@@ -402,7 +474,7 @@ async fn post_ciphers(data: Json<CipherData>, headers: Headers, conn: DbConn, nt
     // needed when creating a new cipher, so just ignore it unconditionally.
     data.last_known_revision_date = None;
 
-    let mut cipher = Cipher::new(data.r#type, data.name.clone());
+    let mut cipher = Cipher::new(data.r#type);
     update_cipher_from_data(&mut cipher, data, &headers, None, &conn, &nt, UpdateType::SyncCipherCreate).await?;
 
     Ok(Json(cipher.to_json(&headers.host, &headers.user.uuid, None, CipherSyncType::User, &conn).await?))
@@ -426,6 +498,44 @@ async fn enforce_personal_ownership_policy(data: Option<&CipherData>, headers: &
     Ok(())
 }
 
+/// The checks of saving a cipher, for callers that run them before writing anything else
+async fn validate_cipher_update(
+    cipher: &Cipher,
+    data: &CipherData,
+    headers: &Headers,
+    conn: &DbConn,
+    ut: UpdateType,
+) -> EmptyResult {
+    // Check that the client isn't updating an existing cipher with stale data.
+    // And only perform this check when not importing ciphers, else the date/time check will fail.
+    if ut != UpdateType::None
+        && let Some(dt) = &data.last_known_revision_date
+    {
+        match NaiveDateTime::parse_from_str(dt, "%+") {
+            // ISO 8601 format
+            Err(err) => warn!("Error parsing LastKnownRevisionDate '{dt}': {err}"),
+            Ok(dt) if cipher.updated_at.signed_duration_since(dt).num_seconds() > 1 => {
+                err!("The client copy of this cipher is out of date. Resync the client and try again.")
+            }
+            Ok(_) => (),
+        }
+    }
+
+    if let Some(note) = &data.notes {
+        let max_note_size = CONFIG._max_note_size();
+        if note.len() > max_note_size {
+            err!(format!("The field Notes exceeds the maximum encrypted value length of {max_note_size} characters."))
+        }
+    }
+
+    if let Some(folder_id) = &data.folder_id
+        && Folder::find_by_uuid_and_user(folder_id, &headers.user.uuid, conn).await.is_none()
+    {
+        err!("Invalid folder", "Folder does not exist or belongs to another user");
+    }
+    Ok(())
+}
+
 pub async fn update_cipher_from_data(
     cipher: &mut Cipher,
     data: CipherData,
@@ -451,32 +561,14 @@ pub async fn update_cipher_from_data(
 
     enforce_personal_ownership_policy(Some(&data), headers, conn).await?;
 
-    // Check that the client isn't updating an existing cipher with stale data.
+    let is_blob = data.is_blob();
-    // And only perform this check when not importing ciphers, else the date/time check will fail.
+    data.validate_content(is_blob)?;
-    if ut != UpdateType::None
+    validate_cipher_update(cipher, &data, headers, conn, ut).await?;
-        && let Some(dt) = data.last_known_revision_date
-    {
-        match NaiveDateTime::parse_from_str(&dt, "%+") {
-            // ISO 8601 format
-            Err(err) => warn!("Error parsing LastKnownRevisionDate '{dt}': {err}"),
-            Ok(dt) if cipher.updated_at.signed_duration_since(dt).num_seconds() > 1 => {
-                err!("The client copy of this cipher is out of date. Resync the client and try again.")
-            }
-            Ok(_) => (),
-        }
-    }
 
     if cipher.organization_uuid.is_some() && cipher.organization_uuid != data.organization_id {
         err!("Organization mismatch. Please resync the client before updating the cipher")
     }
 
-    if let Some(note) = &data.notes {
-        let max_note_size = CONFIG._max_note_size();
-        if note.len() > max_note_size {
-            err!(format!("The field Notes exceeds the maximum encrypted value length of {max_note_size} characters."))
-        }
-    }
-
     // Check if this cipher is being transferred from a personal to an organization vault
     let transfer_cipher = cipher.organization_uuid.is_none() && data.organization_id.is_some();
 
@@ -507,12 +599,6 @@ pub async fn update_cipher_from_data(
         cipher.user_uuid = Some(headers.user.uuid.clone());
     }
 
-    if let Some(ref folder_id) = data.folder_id
-        && Folder::find_by_uuid_and_user(folder_id, &headers.user.uuid, conn).await.is_none()
-    {
-        err!("Invalid folder", "Folder does not exist or belongs to another user");
-    }
-
     // Modify attachments name and keys when rotating
     if let Some(attachments) = data.attachments2 {
         for (id, attachment) in attachments {
@@ -551,26 +637,36 @@ pub async fn update_cipher_from_data(
         _ => err!("Invalid type"),
     };
 
-    let type_data = if let Some(mut data) = type_data_opt {
+    if let Some(blob) = data.data.filter(|_| is_blob) {
+        // A blob holds everything, the name included; the column can't be null, so it's left empty
+        // TODO: Make `ciphers.name` nullable and store `None` here instead.
+        cipher.name = String::new();
+        cipher.notes = None;
+        cipher.fields = None;
+        cipher.password_history = None;
+        cipher.data = blob;
+    } else {
+        let Some(mut type_data) = type_data_opt else {
+            err!("Data missing")
+        };
         // Remove the 'Response' key from the base object.
-        if let Some(data_obj) = data.as_object_mut() {
+        if let Some(data_obj) = type_data.as_object_mut() {
             data_obj.remove("response");
         }
         // Remove the 'Response' key from every Uri.
-        if data["uris"].is_array() {
+        if type_data["uris"].is_array() {
-            data["uris"] = clean_cipher_data(data["uris"].clone());
+            type_data["uris"] = clean_cipher_data(type_data["uris"].clone());
         }
-        data
-    } else {
-        err!("Data missing")
-    };
 
-    cipher.key = data.key;
+        // `validate_content` made sure there is a name
-    cipher.name = data.name;
+        cipher.name = data.name.unwrap_or_default();
         cipher.notes = data.notes;
         cipher.fields = data.fields.map(|f| clean_cipher_data(f).to_string());
-    cipher.data = type_data.to_string();
         cipher.password_history = data.password_history.map(|f| f.to_string());
+        cipher.data = type_data.to_string();
+    }
+
+    cipher.key = data.key;
     cipher.reprompt = data.reprompt.filter(|r| *r == RepromptType::None as i32 || *r == RepromptType::Password as i32);
 
     cipher.save(conn).await?;
@@ -667,7 +763,7 @@ async fn post_ciphers_import(data: Json<ImportData>, headers: Headers, conn: DbC
         let folder_id = relations_map.get(&index).and_then(|i| folders.get(*i).cloned());
         cipher_data.folder_id = folder_id;
 
-        let mut cipher = Cipher::new(cipher_data.r#type, cipher_data.name.clone());
+        let mut cipher = Cipher::new(cipher_data.r#type);
         update_cipher_from_data(&mut cipher, cipher_data, &headers, None, &conn, &nt, UpdateType::None).await?;
     }
 
@@ -735,6 +831,9 @@ async fn put_cipher(
         err!("Cipher is not write accessible")
     }
 
+    // Against the cipher we hold rather than the organization the client claims, like upstream
+    validate_encrypted_by_user(&data, &headers.user, cipher.organization_uuid.is_some())?;
+
     update_cipher_from_data(&mut cipher, data, &headers, None, &conn, &nt, UpdateType::SyncCipherUpdate).await?;
 
     Ok(Json(cipher.to_json(&headers.host, &headers.user.uuid, None, CipherSyncType::User, &conn).await?))
@@ -993,9 +1092,7 @@ async fn post_cipher_share(
     conn: DbConn,
     nt: Notify<'_>,
 ) -> JsonResult {
-    let data: ShareCipherData = data.into_inner();
+    put_cipher_share(cipher_id, data, headers, conn, nt).await
-
-    share_cipher_by_uuid(&cipher_id, data, &headers, &conn, &nt, None).await
 }
 
 #[put("/ciphers/<cipher_id>/share", data = "<data>")]
@@ -1008,6 +1105,21 @@ async fn put_cipher_share(
 ) -> JsonResult {
     let data: ShareCipherData = data.into_inner();
 
+    // Upstream's `PutShare` checks, before anything is written.
+    // Ref: <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Api/Vault/Controllers/CiphersController.cs#L899-L912>
+    // and <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Api/Vault/Models/Request/CipherRequestModel.cs#L498-L519>
+    if data.cipher.organization_id.is_none() {
+        err!("Cipher OrganizationId is required.")
+    }
+    if data.collection_ids.is_empty() {
+        err!("You must select at least one collection.")
+    }
+    if !Cipher::find_by_uuid(&cipher_id, &conn).await.is_some_and(|c| c.user_uuid.as_ref() == Some(&headers.user.uuid))
+    {
+        err_code!("Cipher doesn't exist", Status::NotFound.code)
+    }
+    validate_encrypted_for_user(&data.cipher, &headers.user.uuid)?;
+
     share_cipher_by_uuid(&cipher_id, data, &headers, &conn, &nt, None).await
 }
 
@@ -1027,18 +1139,33 @@ async fn put_cipher_share_selected(
 ) -> EmptyResult {
     let mut data: ShareSelectedCipherData = data.into_inner();
 
+    // Upstream's `PutShareMany` checks, before anything is written.
+    // Ref: <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Api/Vault/Controllers/CiphersController.cs#L1395-L1421>
+    // and <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Api/Vault/Models/Request/CipherRequestModel.cs#L560-L604>
     if data.ciphers.is_empty() {
         err!("You must select at least one cipher.")
     }
-
+    if data.ciphers.iter().any(|c| c.id.is_none() || c.organization_id.is_none()) {
+        err!("All Ciphers must have an Id and OrganizationId.")
+    }
+    if data.ciphers.iter().map(|c| &c.organization_id).collect::<HashSet<_>>().len() != 1 {
+        err!("All ciphers must be for the same organization.")
+    }
     if data.collection_ids.is_empty() {
         err!("You must select at least one collection.")
     }
-
     for cipher in &data.ciphers {
-        if cipher.id.is_none() {
+        cipher.validate_content(cipher.is_blob())?;
-            err!("Request missing ids field")
     }
+    for cipher in &data.ciphers {
+        validate_encrypted_for_user(cipher, &headers.user.uuid)?;
+    }
+    let owned_ciphers = Cipher::find_owned_by_user(&headers.user.uuid, &conn).await;
+    for cipher_data in &data.ciphers {
+        let Some(cipher) = owned_ciphers.iter().find(|c| cipher_data.id.as_ref() == Some(&c.uuid)) else {
+            err!("Trying to share ciphers that you do not own.")
+        };
+        validate_cipher_update(cipher, cipher_data, &headers, &conn, UpdateType::None).await?;
     }
 
     while let Some(cipher) = data.ciphers.pop() {
@@ -1085,6 +1212,20 @@ async fn share_cipher_by_uuid(
         err!("Organization mismatch. Please resync the client before updating the cipher")
     }
 
+    // When LastKnownRevisionDate is None, it is a new cipher, so send CipherCreate.
+    // If there is an override, like when handling multiple items, we want to prevent a push notification for every single item
+    let ut = if let Some(ut) = override_ut {
+        ut
+    } else if data.cipher.last_known_revision_date.is_some() {
+        UpdateType::SyncCipherUpdate
+    } else {
+        UpdateType::SyncCipherCreate
+    };
+
+    // For the same reason, the other checks of saving
+    data.cipher.validate_content(data.cipher.is_blob())?;
+    validate_cipher_update(&cipher, &data.cipher, headers, conn, ut).await?;
+
     let mut shared_to_collections = vec![];
 
     if let Some(organization_id) = &data.cipher.organization_id {
@@ -1103,16 +1244,6 @@ async fn share_cipher_by_uuid(
         }
     }
 
-    // When LastKnownRevisionDate is None, it is a new cipher, so send CipherCreate.
-    // If there is an override, like when handling multiple items, we want to prevent a push notification for every single item
-    let ut = if let Some(ut) = override_ut {
-        ut
-    } else if data.cipher.last_known_revision_date.is_some() {
-        UpdateType::SyncCipherUpdate
-    } else {
-        UpdateType::SyncCipherCreate
-    };
-
     update_cipher_from_data(&mut cipher, data.cipher, headers, Some(shared_to_collections), conn, nt, ut).await?;
 
     Ok(Json(cipher.to_json(&headers.host, &headers.user.uuid, None, CipherSyncType::User, conn).await?))

src/api/core/organizations.rs

@@ -8,7 +8,7 @@ use crate::{
     CONFIG,
     api::admin::FAKE_ADMIN_UUID,
     api::{
-        EmptyResult, JsonResult, Notify, PasswordOrOtpData, UpdateType,
+        ApiResult, EmptyResult, JsonResult, Notify, PasswordOrOtpData, UpdateType,
         core::{CipherSyncData, CipherSyncType, accept_org_invite, log_event, two_factor},
     },
     auth::{AdminHeaders, Headers, ManagerHeaders, ManagerHeadersLoose, OrgMemberHeaders, OwnerHeaders, decode_invite},
@@ -1831,7 +1831,7 @@ async fn post_org_import(
         cipher_data.folder_id = None;
         // Replace the client-provided, unvalidated organizationId with the real target org
         cipher_data.organization_id = Some(org_id.clone());
-        let mut cipher = Cipher::new(cipher_data.r#type, cipher_data.name.clone());
+        let mut cipher = Cipher::new(cipher_data.r#type);
         update_cipher_from_data(
             &mut cipher,
             cipher_data,
@@ -2771,8 +2771,26 @@ struct OrganizationUserRecoverAccountRequest {
 // But the clients do not seem to use this at all
 // Just add it here in case they will
 #[get("/organizations/<org_id>/public-key")]
-async fn get_organization_public_key(org_id: OrganizationId, headers: OrgMemberHeaders, conn: DbConn) -> JsonResult {
+async fn get_organization_public_key(
-    if org_id != headers.membership.org_uuid {
+    org_id: OrganizationId,
+    headers: Headers,
+    member: Result<OrgMemberHeaders, &'static str>,
+    conn: DbConn,
+) -> JsonResult {
+    // SSO users without an org get the fake one, whose key the v2 JIT password flow fetches anyway
+    if org_id.eq_ignore_ascii_case(FAKE_SSO_IDENTIFIER) && headers.user.private_key.is_none() {
+        return Ok(Json(json!({
+            "object": "organizationPublicKey",
+            "publicKey": fake_sso_org_public_key().await?,
+        })));
+    }
+    let member = match member {
+        Ok(member) => member,
+        // The guard already logged it
+        Err(e) => return Err(crate::error::Error::new_msg(e).with_code(Status::Unauthorized.code)),
+    };
+
+    if org_id != member.membership.org_uuid {
         err!("Organization not found", "Organization id's do not match");
     }
     let Some(org) = Organization::find_by_uuid(&org_id, &conn).await else {
@@ -2785,11 +2803,30 @@ async fn get_organization_public_key(org_id: OrganizationId, headers: OrgMemberH
     })))
 }
 
+/// The SDK only uses this key to wrap an account recovery key that it never sends for the fake org,
+/// so it is made once and its private half dropped.
+async fn fake_sso_org_public_key() -> ApiResult<String> {
+    static PUBLIC_KEY: std::sync::LazyLock<Option<String>> = std::sync::LazyLock::new(|| {
+        let der = openssl::rsa::Rsa::generate(2048).and_then(|rsa| rsa.public_key_to_der()).ok()?;
+        Some(data_encoding::BASE64.encode(&der))
+    });
+
+    let Ok(Some(public_key)) = tokio::task::spawn_blocking(|| PUBLIC_KEY.clone()).await else {
+        err!("Failed to generate the organization key")
+    };
+    Ok(public_key)
+}
+
 // Obsolete - Renamed to public-key (2023.8), left for backwards compatibility with older clients
 // https://github.com/bitwarden/server/blob/9ebe16587175b1c0e9208f84397bb75d0d595510/src/Api/AdminConsole/Controllers/OrganizationsController.cs#L487-L492
 #[get("/organizations/<org_id>/keys")]
-async fn get_organization_keys(org_id: OrganizationId, headers: OrgMemberHeaders, conn: DbConn) -> JsonResult {
+async fn get_organization_keys(
-    get_organization_public_key(org_id, headers, conn).await
+    org_id: OrganizationId,
+    headers: Headers,
+    member: Result<OrgMemberHeaders, &'static str>,
+    conn: DbConn,
+) -> JsonResult {
+    get_organization_public_key(org_id, headers, member, conn).await
 }
 
 // Will allow to reset 2FA too

src/api/identity.rs

@@ -551,18 +551,7 @@ async fn authenticated_response(
         Value::Null
     };
 
-    let account_keys = if user.private_key.is_some() {
+    let account_keys = user.account_keys_json(conn).await;
-        json!({
-            "publicKeyEncryptionKeyPair": {
-                "wrappedPrivateKey": user.private_key,
-                "publicKey": user.public_key,
-                "Object": "publicKeyEncryptionKeyPair"
-            },
-            "Object": "privateKeys"
-        })
-    } else {
-        Value::Null
-    };
 
     let mut result = json!({
         "access_token": auth_tokens.access_token(),
@@ -708,18 +697,7 @@ async fn user_api_key_login(
         Value::Null
     };
 
-    let account_keys = if user.private_key.is_some() {
+    let account_keys = user.account_keys_json(conn).await;
-        json!({
-            "publicKeyEncryptionKeyPair": {
-                "wrappedPrivateKey": user.private_key,
-                "publicKey": user.public_key,
-                "Object": "publicKeyEncryptionKeyPair"
-            },
-            "Object": "privateKeys"
-        })
-    } else {
-        Value::Null
-    };
 
     // Note: No refresh_token is returned. The CLI just repeats the
     // client_credentials login flow when the existing token expires.

src/config.rs

@@ -1435,6 +1435,8 @@ pub const SUPPORTED_FEATURE_FLAGS: &[&str] = &[
     // Key Management Team
     "biometrics-sdk-ipc",
     "windows-native-credential-sync",
+    "enable-account-encryption-v2-jit-password-registration",
+    "pm-27278-v2-password-registration",
     // Mobile Team
     "pm-34171-card-scanner",
     // Platform Team

src/db/models/cipher.rs

@@ -19,7 +19,7 @@ use crate::{
         },
     },
     error::MapResult,
-    util::LowerCase,
+    util::{LowerCase, convert_json_key_lcase_first},
 };
 use macros::UuidFromParam;
 
@@ -63,6 +63,18 @@ pub struct Cipher {
     pub reprompt: Option<i32>,
 }
 
+/// Whether `data` is a v2 cipher blob, recognized like upstream by a top-level `format_version` key.
+///
+/// Ref: <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Core/Vault/Entities/Cipher.cs#L36-L41>
+pub fn is_data_blob_encrypted(data: &str) -> bool {
+    serde_json::from_str::<Value>(data).is_ok_and(|d| is_blob_value(&d))
+}
+
+/// [`is_data_blob_encrypted`] for `data` that was already parsed.
+fn is_blob_value(data: &Value) -> bool {
+    data.get("format_version").is_some()
+}
+
 pub enum RepromptType {
     None = 0,
     Password = 1,
@@ -70,7 +82,8 @@ pub enum RepromptType {
 
 /// Local methods
 impl Cipher {
-    pub fn new(atype: i32, name: String) -> Self {
+    /// The name is set when the data is saved, since a blob-encrypted cipher has it inside `data`
+    pub fn new(atype: i32) -> Self {
         let now = Utc::now().naive_utc();
 
         Self {
@@ -84,7 +97,7 @@ impl Cipher {
             key: None,
 
             atype,
-            name,
+            name: String::new(),
 
             notes: None,
             fields: None,
@@ -110,6 +123,11 @@ impl Cipher {
                     .insert(format!("Ciphers[{index}].Notes"), serde_json::to_value([&max_note_size_msg]).unwrap());
             }
 
+            if let Err(e) = cipher.validate_content(cipher.is_blob()) {
+                validation_errors
+                    .insert(format!("Ciphers[{index}].{}", e.field), serde_json::to_value([e.message]).unwrap());
+            }
+
             // Validate the password history if it contains `null` values and if so, return a warning
             if let Some(Value::Array(password_history)) = &cipher.password_history {
                 for pwh in password_history {
@@ -154,6 +172,10 @@ impl Cipher {
     ) -> Result<Value, crate::Error> {
         use crate::util::{format_date, validate_and_format_date};
 
+        // Parsed once, since `data` can be large and this runs for every cipher in a sync
+        let type_data = serde_json::from_str::<Value>(&self.data);
+        let is_blob_encrypted = type_data.as_ref().is_ok_and(is_blob_value);
+
         let mut attachments_json: Value = Value::Null;
         if let Some(cipher_sync_data) = cipher_sync_data {
             if let Some(attachments) = cipher_sync_data.cipher_attachments.get(&self.uuid)
@@ -250,63 +272,9 @@ impl Cipher {
             })
             .unwrap_or_default();
 
-        // Get the type_data or a default to an empty json object '{}'.
+        // Like upstream, fields and password history stored as NULL are sent as null, not `[]`
-        // If not passing an empty object, mobile clients will crash.
+        let fields_json = self.fields.is_some().then_some(fields_json);
-        let mut type_data_json = serde_json::from_str::<LowerCase<Value>>(&self.data)
+        let password_history_json = self.password_history.is_some().then_some(password_history_json);
-            .inspect_err(|_| warn!("Error parsing data field for {}", self.uuid))
-            .map_or_else(|_| Value::Object(serde_json::Map::new()), |d| d.data);
-
-        // NOTE: This was marked as *Backwards Compatibility Code*, but as of January 2021 this is still being used by upstream
-        // Set the first element of the Uris array as Uri, this is needed several (mobile) clients.
-        if self.atype == 1 {
-            // Upstream always has an `uri` key/value
-            type_data_json["uri"] = Value::Null;
-            if let Some(uris) = type_data_json["uris"].as_array_mut()
-                && !uris.is_empty()
-            {
-                // Fix uri match values first, they are only allowed to be a number or null
-                // If it is a string, convert it to an int or null if that fails
-                for uri in &mut *uris {
-                    if uri["match"].is_string() {
-                        let match_value = match uri["match"].as_str().unwrap_or_default().parse::<u8>() {
-                            Ok(n) => json!(n),
-                            _ => Value::Null,
-                        };
-                        uri["match"] = match_value;
-                    }
-                }
-                type_data_json["uri"] = uris[0]["uri"].clone();
-            }
-
-            // Check if `passwordRevisionDate` is a valid date, else convert it
-            if let Some(pw_revision) = type_data_json["passwordRevisionDate"].as_str() {
-                type_data_json["passwordRevisionDate"] = json!(validate_and_format_date(pw_revision));
-            }
-        }
-
-        // Fix secure note issues when data is invalid
-        // This breaks at least the native mobile clients
-        if self.atype == 2 {
-            match type_data_json {
-                Value::Object(ref t) if t.get("type").is_some_and(Value::is_number) => {}
-                _ => {
-                    type_data_json = json!({"type": 0});
-                }
-            }
-        }
-
-        // Fix invalid SSH Entries
-        // This breaks at least the native mobile client if invalid
-        // The only way to fix this is by setting type_data_json to `null`
-        // Opening this ssh-key in the mobile client will probably crash the client, but you can edit, save and afterwards delete it
-        if self.atype == 5
-            && (type_data_json["keyFingerprint"].as_str().is_none_or(str::is_empty)
-                || type_data_json["privateKey"].as_str().is_none_or(str::is_empty)
-                || type_data_json["publicKey"].as_str().is_none_or(str::is_empty))
-        {
-            warn!("Error parsing ssh-key, mandatory fields are invalid for {}", self.uuid);
-            type_data_json = Value::Null;
-        }
 
         let collection_ids = if let Some(cipher_sync_data) = cipher_sync_data {
             if let Some(cipher_collections) = cipher_sync_data.cipher_collections.get(&self.uuid) {
@@ -403,10 +371,84 @@ impl Cipher {
             _ => err!(format!("Cipher {} has an invalid type {}", self.uuid, self.atype)),
         };
 
-        json_object[key] = type_data_json;
+        if is_blob_encrypted {
+            // Like upstream, sent as-is with the structured fields null
+            json_object["data"] = json!(self.data);
+            json_object["name"] = Value::Null;
+        } else {
+            json_object[key] = self.legacy_type_data_json(type_data);
+        }
         Ok(json_object)
     }
 
+    /// The per-type data of a legacy cipher, with fixups for values known to break clients.
+    fn legacy_type_data_json(&self, type_data: Result<Value, serde_json::Error>) -> Value {
+        use crate::util::validate_and_format_date;
+
+        // Get the type_data or a default to an empty json object '{}'.
+        // If not passing an empty object, mobile clients will crash.
+        let mut type_data_json = if let Ok(data @ Value::Object(_)) = type_data {
+            convert_json_key_lcase_first(data)
+        } else {
+            warn!("Error parsing data field for {}", self.uuid);
+            Value::Object(serde_json::Map::new())
+        };
+
+        // NOTE: This was marked as *Backwards Compatibility Code*, but as of January 2021 this is still being used by upstream
+        // Set the first element of the Uris array as Uri, this is needed several (mobile) clients.
+        if self.atype == 1 {
+            // Upstream always has an `uri` key/value
+            type_data_json["uri"] = Value::Null;
+            if let Some(uris) = type_data_json["uris"].as_array_mut()
+                && !uris.is_empty()
+            {
+                // Fix uri match values first, they are only allowed to be a number or null
+                // If it is a string, convert it to an int or null if that fails
+                for uri in &mut *uris {
+                    if uri["match"].is_string() {
+                        let match_value = match uri["match"].as_str().unwrap_or_default().parse::<u8>() {
+                            Ok(n) => json!(n),
+                            _ => Value::Null,
+                        };
+                        uri["match"] = match_value;
+                    }
+                }
+                type_data_json["uri"] = uris[0]["uri"].clone();
+            }
+
+            // Check if `passwordRevisionDate` is a valid date, else convert it
+            if let Some(pw_revision) = type_data_json["passwordRevisionDate"].as_str() {
+                type_data_json["passwordRevisionDate"] = json!(validate_and_format_date(pw_revision));
+            }
+        }
+
+        // Fix secure note issues when data is invalid
+        // This breaks at least the native mobile clients
+        if self.atype == 2 {
+            match type_data_json {
+                Value::Object(ref t) if t.get("type").is_some_and(Value::is_number) => {}
+                _ => {
+                    type_data_json = json!({"type": 0});
+                }
+            }
+        }
+
+        // Fix invalid SSH Entries
+        // This breaks at least the native mobile client if invalid
+        // The only way to fix this is by setting type_data_json to `null`
+        // Opening this ssh-key in the mobile client will probably crash the client, but you can edit, save and afterwards delete it
+        if self.atype == 5
+            && (type_data_json["keyFingerprint"].as_str().is_none_or(str::is_empty)
+                || type_data_json["privateKey"].as_str().is_none_or(str::is_empty)
+                || type_data_json["publicKey"].as_str().is_none_or(str::is_empty))
+        {
+            warn!("Error parsing ssh-key, mandatory fields are invalid for {}", self.uuid);
+            type_data_json = Value::Null;
+        }
+
+        type_data_json
+    }
+
     pub async fn update_users_revision(&self, conn: &DbConn) -> Vec<UserId> {
         let mut user_uuids = Vec::new();
         match self.user_uuid {

src/db/models/mod.rs

@@ -17,11 +17,12 @@ mod two_factor;
 mod two_factor_duo_context;
 mod two_factor_incomplete;
 mod user;
+mod user_signature_key_pair;
 
 pub use self::archive::Archive;
 pub use self::attachment::{Attachment, AttachmentId};
 pub use self::auth_request::{AuthRequest, AuthRequestId};
-pub use self::cipher::{Cipher, CipherId, RepromptType};
+pub use self::cipher::{Cipher, CipherId, RepromptType, is_data_blob_encrypted};
 pub use self::collection::{Collection, CollectionCipher, CollectionId, CollectionUser};
 pub use self::device::{Device, DeviceId, DeviceType, DeviceWithAuthRequest, PushId};
 pub use self::emergency_access::{EmergencyAccess, EmergencyAccessId, EmergencyAccessStatus, EmergencyAccessType};
@@ -40,3 +41,4 @@ pub use self::two_factor::{TwoFactor, TwoFactorType};
 pub use self::two_factor_duo_context::TwoFactorDuoContext;
 pub use self::two_factor_incomplete::TwoFactorIncomplete;
 pub use self::user::{Invitation, KeyId, SsoUser, User, UserId, UserKdfType, UserStampException};
+pub use self::user_signature_key_pair::{SignatureAlgorithm, UserSignatureKeyPair};

src/db/models/user.rs

@@ -20,6 +20,7 @@ use macros::UuidFromParam;
 
 use super::{
     Cipher, Device, EmergencyAccess, Favorite, Folder, Membership, MembershipType, TwoFactor, TwoFactorIncomplete,
+    UserSignatureKeyPair,
 };
 
 #[derive(Identifiable, Queryable, Insertable, AsChangeset, Selectable)]
@@ -71,6 +72,11 @@ 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>,
+
+    // The v2 state: all set, with a `user_signature_key_pairs` row, or none, see `User::is_v2`
+    pub signed_public_key: Option<String>,
+    pub security_state: Option<String>,
+    pub security_version: Option<i32>,
 }
 
 #[derive(Identifiable, Queryable, Insertable)]
@@ -158,9 +164,17 @@ impl User {
             external_id: None, // Todo: Needs to be removed in the future, this is not used anymore.
 
             key_id: None,
+
+            signed_public_key: None,
+            security_state: None,
+            security_version: None,
         }
     }
 
+    pub fn is_v2(&self) -> bool {
+        self.signed_public_key.is_some() && self.security_state.is_some() && self.security_version.is_some()
+    }
+
     pub fn check_valid_password(&self, password: &str) -> bool {
         crypto::verify_password_hash(
             password.as_bytes(),
@@ -265,18 +279,37 @@ impl User {
         !CONFIG.mail_enabled() || self.verified_at.is_some()
     }
 
+    async fn v2_signature_key_pair(&self, conn: &DbConn) -> Option<UserSignatureKeyPair> {
+        if !self.is_v2() {
+            return None;
+        }
+        UserSignatureKeyPair::find_by_user(&self.uuid, conn).await
+    }
+
     /// The `accountKeys` object (upstream's `PrivateKeysResponseModel`), null without a key pair
-    pub fn account_keys_json(&self) -> Value {
+    pub async fn account_keys_json(&self, conn: &DbConn) -> Value {
         if self.private_key.is_some() {
+            let (signed_public_key, signature_key_pair, security_state) = match self.v2_signature_key_pair(conn).await {
+                Some(key_pair) => (
+                    json!(self.signed_public_key),
+                    key_pair.to_json(),
+                    json!({
+                        "securityState": self.security_state,
+                        "securityVersion": self.security_version,
+                    }),
+                ),
+                None => (Value::Null, Value::Null, Value::Null),
+            };
+
             json!({
                 "publicKeyEncryptionKeyPair": {
                     "wrappedPrivateKey": self.private_key,
                     "publicKey": self.public_key,
-                    "signedPublicKey": null,
+                    "signedPublicKey": signed_public_key,
                     "object": "publicKeyEncryptionKeyPair",
                 },
-                "securityState": null,
+                "securityState": security_state,
-                "signatureKeyPair": null,
+                "signatureKeyPair": signature_key_pair,
                 "object": "privateKeys"
             })
         } else {
@@ -284,6 +317,20 @@ impl User {
         }
     }
 
+    pub async fn public_keys_json(&self, conn: &DbConn) -> Value {
+        let (signed_public_key, verifying_key) = match self.v2_signature_key_pair(conn).await {
+            Some(key_pair) => (json!(self.signed_public_key), json!(key_pair.verifying_key)),
+            None => (Value::Null, Value::Null),
+        };
+
+        json!({
+            "publicKey": self.public_key,
+            "signedPublicKey": signed_public_key,
+            "verifyingKey": verifying_key,
+            "object": "publicKeys"
+        })
+    }
+
     pub async fn to_json(&self, conn: &DbConn) -> Value {
         let mut orgs_json = Vec::new();
         for c in Membership::find_confirmed_by_user(&self.uuid, conn).await {
@@ -304,7 +351,7 @@ impl User {
             UserStatus::Enabled
         };
 
-        let account_keys = self.account_keys_json();
+        let account_keys = self.account_keys_json(conn).await;
 
         json!({
             "_status": status as i32,
@@ -380,6 +427,7 @@ impl User {
         Device::delete_all_by_user(&self.uuid, conn).await?;
         TwoFactor::delete_all_by_user(&self.uuid, conn).await?;
         TwoFactorIncomplete::delete_all_by_user(&self.uuid, conn).await?;
+        UserSignatureKeyPair::delete_all_by_user(&self.uuid, conn).await?;
         Invitation::take(&self.email, conn).await; // Delete invitation if any
 
         conn.run(move |conn| {

src/db/models/user_signature_key_pair.rs

@@ -0,0 +1,132 @@
+use chrono::{NaiveDateTime, Utc};
+use derive_more::{AsRef, Deref, Display, From};
+use diesel::prelude::*;
+use serde_json::Value;
+
+use crate::{
+    api::EmptyResult,
+    db::{DbConn, schema::user_signature_key_pairs},
+    error::MapResult,
+    util::get_uuid,
+};
+
+use super::UserId;
+
+/// A user's signature key pair, part of the v2 state, in its own table like upstream.
+///
+/// Ref: <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Sql/dbo/KeyManagement/Tables/UserSignatureKeyPair.sql#L1-L15>
+#[derive(Identifiable, Queryable, Insertable, AsChangeset, Selectable)]
+#[diesel(table_name = user_signature_key_pairs)]
+#[diesel(treat_none_as_null = true)]
+#[diesel(primary_key(uuid))]
+pub struct UserSignatureKeyPair {
+    pub uuid: UserSignatureKeyPairId,
+    pub user_uuid: UserId,
+
+    pub signature_algorithm: i32,
+    /// The signing (private) key, wrapped by the user key.
+    pub signing_key: String,
+    /// The COSE-encoded public verifying key.
+    pub verifying_key: String,
+
+    pub created_at: NaiveDateTime,
+    pub updated_at: NaiveDateTime,
+}
+
+/// Ref: <https://github.com/bitwarden/server/blob/9030c42bf7d8f9ac2ff9fee85c39588d5eb81499/src/Core/KeyManagement/Enums/SignatureAlgorithm.cs#L6-L10>
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum SignatureAlgorithm {
+    Ed25519 = 0,
+    MlDsa44 = 1,
+}
+
+impl SignatureAlgorithm {
+    pub fn parse(algorithm: &str) -> Option<Self> {
+        match algorithm {
+            "ed25519" => Some(Self::Ed25519),
+            "mldsa44" => Some(Self::MlDsa44),
+            _ => None,
+        }
+    }
+}
+
+/// Local methods
+impl UserSignatureKeyPair {
+    pub fn new(
+        user_uuid: UserId,
+        signature_algorithm: SignatureAlgorithm,
+        signing_key: String,
+        verifying_key: String,
+    ) -> Self {
+        let now = Utc::now().naive_utc();
+
+        Self {
+            uuid: UserSignatureKeyPairId(get_uuid()),
+            user_uuid,
+            signature_algorithm: signature_algorithm as i32,
+            signing_key,
+            verifying_key,
+            created_at: now,
+            updated_at: now,
+        }
+    }
+
+    pub fn to_json(&self) -> Value {
+        json!({
+            "wrappedSigningKey": self.signing_key,
+            "verifyingKey": self.verifying_key,
+            "object": "signatureKeyPair",
+        })
+    }
+}
+
+/// Database methods
+impl UserSignatureKeyPair {
+    pub async fn save(&mut self, conn: &DbConn) -> EmptyResult {
+        self.updated_at = Utc::now().naive_utc();
+
+        db_run! { conn:
+            mysql {
+                diesel::insert_into(user_signature_key_pairs::table)
+                    .values(&*self)
+                    .on_conflict(diesel::dsl::DuplicatedKeys)
+                    .do_update()
+                    .set(&*self)
+                    .execute(conn)
+                    .map_res("Error saving user signature key pair")
+            }
+            postgresql, sqlite {
+                diesel::insert_into(user_signature_key_pairs::table)
+                    .values(&*self)
+                    .on_conflict(user_signature_key_pairs::user_uuid)
+                    .do_update()
+                    .set(&*self)
+                    .execute(conn)
+                    .map_res("Error saving user signature key pair")
+            }
+        }
+    }
+
+    /// The user's key pair. There is at most one, enforced by a unique index on `user_uuid`.
+    pub async fn find_by_user(user_uuid: &UserId, conn: &DbConn) -> Option<Self> {
+        conn.run(move |conn| {
+            user_signature_key_pairs::table
+                .filter(user_signature_key_pairs::user_uuid.eq(user_uuid))
+                .first::<Self>(conn)
+                .ok()
+        })
+        .await
+    }
+
+    pub async fn delete_all_by_user(user_uuid: &UserId, conn: &DbConn) -> EmptyResult {
+        conn.run(move |conn| {
+            diesel::delete(user_signature_key_pairs::table.filter(user_signature_key_pairs::user_uuid.eq(user_uuid)))
+                .execute(conn)
+                .map_res("Error deleting user signature key pairs")
+        })
+        .await
+    }
+}
+
+#[derive(Clone, Debug, AsRef, Deref, DieselNewType, Display, From, Hash, PartialEq, Eq, Serialize, Deserialize)]
+pub struct UserSignatureKeyPairId(String);

src/db/schema.rs

@@ -219,6 +219,21 @@ table! {
         avatar_color -> Nullable<Text>,
         external_id -> Nullable<Text>,
         key_id -> Nullable<Text>,
+        signed_public_key -> Nullable<Text>,
+        security_state -> Nullable<Text>,
+        security_version -> Nullable<Integer>,
+    }
+}
+
+table! {
+    user_signature_key_pairs (uuid) {
+        uuid -> Text,
+        user_uuid -> Text,
+        signature_algorithm -> Integer,
+        signing_key -> Text,
+        verifying_key -> Text,
+        created_at -> Timestamp,
+        updated_at -> Timestamp,
     }
 }
 
@@ -384,6 +399,7 @@ joinable!(collections_groups -> groups (groups_uuid));
 joinable!(event -> users_organizations (uuid));
 joinable!(auth_requests -> users (user_uuid));
 joinable!(sso_users -> users (user_uuid));
+joinable!(user_signature_key_pairs -> users (user_uuid));
 
 allow_tables_to_appear_in_same_query!(
     archives,
@@ -410,4 +426,5 @@ allow_tables_to_appear_in_same_query!(
     collections_groups,
     event,
     auth_requests,
+    user_signature_key_pairs,
 );

src/util.rs

@@ -839,6 +839,12 @@ pub fn parse_experimental_client_feature_flags(
         .collect()
 }
 
+/// Whether the admin enabled this supported client feature flag
+pub fn is_client_feature_flag_enabled(flag: &str) -> bool {
+    parse_experimental_client_feature_flags(&CONFIG.experimental_client_feature_flags(), &FeatureFlagFilter::ValidOnly)
+        .contains_key(flag)
+}
+
 /// TODO: This is extracted from IpAddr::is_global, which is unstable:
 /// https://doc.rust-lang.org/nightly/std/net/enum.IpAddr.html#method.is_global
 /// Remove once https://github.com/rust-lang/rust/issues/27709 is merged