syntax = "proto2";
import "response.proto";

message Response_PasswordSalt {
    extend Response {
        optional Response_PasswordSalt ext = 1017;
    }
    // Salt for the legacy password hash. Pre-challenge clients derive and send
    // that hash from it. For migrated accounts holding a fresh legacy backup
    // this carries the backup's salt so those clients can still log in; clients
    // that speak challenge-response must use scrypt_salt instead when present.
    optional string password_salt = 1;
    // scrypt cost parameters for the verifier. Absent/zero for legacy accounts.
    optional int32 n = 2;
    optional int32 r = 3;
    optional int32 p = 4;
    // Server-generated challenge. When present the client must authenticate
    // with a challenge-response instead of transmitting the password hash.
    optional bytes nonce = 5;
    // True when the account still uses the legacy password format and should
    // be migrated to the scrypt format after a successful login.
    optional bool needs_migration = 6;
    // Salt of the stored scrypt verifier. Present for migrated accounts;
    // challenge-response clients derive the verifier from this rather than
    // from password_salt, which may carry a legacy backup salt.
    optional string scrypt_salt = 7;
}