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5de570c9ae
Analysis of customer stalls revealed that the function `detail::hash_with_salt` (invoked by `passwords::check`) often blocks the reactor. Internally, this function uses the external `crypt_r` function to compute password hashes, which is CPU-intensive.
This PR addresses the issue in two ways:
1) `sha-512` is now the only password hashing scheme for new passwords (it was already the common-case).
2) `passwords::check` is moved to a dedicated alien thread.
Regarding point 1: before this change, the following hashing schemes were supported by `identify_best_supported_scheme()`: bcrypt_y, bcrypt_a, SHA-512, SHA-256, and MD5. The reason for this was that the `crypt_r` function used for password hashing comes from an external library (currently `libxcrypt`), and the supported hashing algorithms vary depending on the library in use. However:
- The bcrypt schemes never worked properly because their prefixes lack the required round count (e.g. `$2y$` instead of `$2y$05$`). Moreover, bcrypt is slower than SHA-512, so it not good idea to fix or use it.
- SHA-256 and SHA-512 both belong to the SHA-2 family. Libraries that support one almost always support the other, so it’s very unlikely to find SHA-256 without SHA-512.
- MD5 is no longer considered secure for password hashing.
Regarding point 2: the `passwords::check` call now runs on a shared alien thread created at database startup. An `std::mutex` synchronizes that thread with the shards. In theory this could introduce a frequent lock contention, but in practice each shard handles only a few hundred new connections per second—even during storms. There is already `_conns_cpu_concurrency_semaphore` in `generic_server` limits the number of concurrent connection handlers.
Fixes https://github.com/scylladb/scylladb/issues/24524
Backport not needed, as it is a new feature.
Closes scylladb/scylladb#24924
* github.com:scylladb/scylladb:
main: utils: add thread names to alien workers
auth: move passwords::check call to alien thread
test: wait for 3 clients with given username in test_service_level_api
auth: refactor password checking in password_authenticator
auth: make SHA-512 the only password hashing scheme for new passwords
auth: whitespace change in identify_best_supported_scheme()
auth: require scheme as parameter for `generate_salt`
auth: check password hashing scheme support on authenticator start
(cherry picked from commit c762425ea7)
107 lines
3.1 KiB
C++
107 lines
3.1 KiB
C++
/*
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* Copyright (C) 2016-present ScyllaDB
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*
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* Modified by ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: (LicenseRef-ScyllaDB-Source-Available-1.0 and Apache-2.0)
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*/
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#pragma once
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#include <seastar/core/abort_source.hh>
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#include <seastar/core/shared_future.hh>
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#include "db/consistency_level_type.hh"
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#include "auth/authenticator.hh"
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#include "auth/passwords.hh"
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#include "service/raft/raft_group0_client.hh"
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#include "utils/alien_worker.hh"
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namespace db {
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class config;
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}
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namespace cql3 {
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class query_processor;
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} // namespace cql3
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namespace service {
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class migration_manager;
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}
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namespace auth {
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extern const std::string_view password_authenticator_name;
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class password_authenticator : public authenticator {
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cql3::query_processor& _qp;
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::service::raft_group0_client& _group0_client;
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::service::migration_manager& _migration_manager;
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future<> _stopped;
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abort_source _as;
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std::string _superuser; // default superuser name from the config (may or may not be present in roles table)
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shared_promise<> _superuser_created_promise;
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// We used to also support bcrypt, SHA-256, and MD5 (ref. scylladb#24524).
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constexpr static auth::passwords::scheme _scheme = passwords::scheme::sha_512;
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utils::alien_worker& _hashing_worker;
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public:
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static db::consistency_level consistency_for_user(std::string_view role_name);
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static std::string default_superuser(const db::config&);
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password_authenticator(cql3::query_processor&, ::service::raft_group0_client&, ::service::migration_manager&, utils::alien_worker&);
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~password_authenticator();
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virtual future<> start() override;
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virtual future<> stop() override;
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virtual std::string_view qualified_java_name() const override;
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virtual bool require_authentication() const override;
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virtual authentication_option_set supported_options() const override;
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virtual authentication_option_set alterable_options() const override;
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virtual future<authenticated_user> authenticate(const credentials_map& credentials) const override;
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virtual future<> create(std::string_view role_name, const authentication_options& options, ::service::group0_batch& mc) override;
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virtual future<> alter(std::string_view role_name, const authentication_options& options, ::service::group0_batch&) override;
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virtual future<> drop(std::string_view role_name, ::service::group0_batch&) override;
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virtual future<custom_options> query_custom_options(std::string_view role_name) const override;
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virtual bool uses_password_hashes() const override;
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virtual future<std::optional<sstring>> get_password_hash(std::string_view role_name) const override;
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virtual const resource_set& protected_resources() const override;
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virtual ::shared_ptr<sasl_challenge> new_sasl_challenge() const override;
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virtual future<> ensure_superuser_is_created() const override;
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private:
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bool legacy_metadata_exists() const;
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future<> migrate_legacy_metadata() const;
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future<> legacy_create_default_if_missing();
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future<> maybe_create_default_password();
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future<> maybe_create_default_password_with_retries();
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sstring update_row_query() const;
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};
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}
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