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Erlang OTP: Distributed & Fault-Tolerant Systems Programming · 课时

身份验证与授权

为访问 Erlang 服务的进程和用户实现稳健的身份验证与授权机制。

身份验证与授权 是 CoddyKit 上的免费 Erlang OTP: Distributed & Fault-Tolerant Systems Programming 课时。 这是第 2 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Erlang OTP: Distributed & Fault-Tolerant Systems Programming 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Erlang OTP: Distributed & Fault-Tolerant Systems Programming 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

AuthN & AuthZ Explained

In distributed systems, knowing who is accessing your services and what they are allowed to do is critical for security. This is where authentication and authorization come in.

  • Authentication (AuthN): Verifies the identity of a user or process. It answers the question, "Who are you?"
  • Authorization (AuthZ): Determines if an authenticated user or process has permission to perform a specific action or access a resource. It answers, "What are you allowed to do?"

They work hand-in-hand to secure your Erlang applications.

Identifying Users

For user authentication, we typically verify credentials like a username and password. In Erlang, you might have a dedicated service (often a GenServer) responsible for managing user accounts and validating login attempts.

This service would receive a login request, check the provided credentials against stored data, and respond with either success or failure. On success, it might issue a session ID or token.

Building an Auth GenServer

Let's create a very basic auth_service using GenServer. For simplicity, it will store a hardcoded user and password. In a real system, you'd integrate with a database and securely hash passwords.

Our auth_service will have a login/2 function that clients can call to authenticate.

Runnable Auth Service

Try running this simple authentication service. You can call auth_service:login("user", "pass") and auth_service:login("wrong", "pass") to see the different responses.

-module(auth_service).
-behaviour(gen_server).

-export([start_link/0, login/2]).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
             terminate/2, code_change/3]).

% Client API
start_link() ->
    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).

login(Username, Password) ->
    gen_server:call(?MODULE, {login, Username, Password}).

% GenServer Callbacks
init([]) ->
    % Store a simple user/pass for demonstration
    Users = #{<<"user">> => <<"pass">>},
    {ok, Users}.

handle_call({login, Username, Password}, _From, State) ->
    case maps:get(Username, State, undefined) of
        Password ->
            {reply, {ok, <<"authenticated">>}, State};
        _ ->
            {reply, {error, <<"invalid_credentials">>}, State}
    end;
handle_call(_Request, _From, State) ->
    {reply, {error, unknown_request}, State}.

handle_cast(_Msg, State) ->
    {noreply, State}.

handle_info(_Info, State) ->
    {noreply, State}.

terminate(_Reason, _State) ->
    ok.

code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

What Can You Do?

Once a user is authenticated, the next step is authorization. This means deciding what actions they are allowed to perform. A common way to manage this is through Role-Based Access Control (RBAC).

  • Roles: Groups of permissions (e.g., admin, editor, viewer).
  • Permissions: Specific actions (e.g., create_post, edit_post, delete_post).

Users are assigned roles, and roles are assigned permissions.

Role-Based Access Control

We can extend our auth_service (or a separate service) to manage roles and permissions. It would need to know:

  • Which roles a user has.
  • Which permissions each role grants.

Then, when a service needs to check if a user can perform an action, it asks the authorization service.

Auth Service with RBAC

Here's an updated auth_service that includes a basic RBAC mechanism. It defines roles and permissions and allows checking if a user has a specific permission.

Try calling auth_service:check_permission("user", "read_data") and auth_service:check_permission("user", "delete_data") after logging in.

-module(auth_service).
-behaviour(gen_server).

-export([start_link/0, login/2, check_permission/2]).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
             terminate/2, code_change/3]).

% Client API
start_link() ->
    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).

login(Username, Password) ->
    gen_server:call(?MODULE, {login, Username, Password}).

check_permission(Username, Permission) ->
    gen_server:call(?MODULE, {check_permission, Username, Permission}).

% GenServer Callbacks
init([]) ->
    Users = #{
        <<"user">> => #{
            password => <<"pass">>,
            roles => [<<"viewer">>, <<"editor">>]
        },
        <<"admin">> => #{
            password => <<"admin_pass">>,
            roles => [<<"admin">>, <<"viewer">>]
        }
    },
    Roles = #{
        <<"viewer">> => [<<"read_data">>],
        <<"editor">> => [<<"read_data">>, <<"write_data">>],
        <<"admin">> => [<<"read_data">>, <<"write_data">>, <<"delete_data">>]
    },
    {ok, #{users => Users, roles => Roles}}.

handle_call({login, Username, Password}, _From, State) ->
    Users = maps:get(users, State),
    case maps:get(Username, Users, undefined) of
        #{password := Password} ->
            {reply, {ok, <<"authenticated">>}, State};
        _ ->
            {reply, {error, <<"invalid_credentials">>}, State}
    end;

handle_call({check_permission, Username, Permission}, _From, State) ->
    Users = maps:get(users, State),
    Roles = maps:get(roles, State),
    case maps:get(Username, Users, undefined) of
        #{roles := UserRoles} ->
            HasPermission = lists:any(
                fun(Role) ->
                    case maps:get(Role, Roles, []) of
                        RolePermissions when is_list(RolePermissions) ->
                            lists:member(Permission, RolePermissions);
                        _ -> false
                    end
                end,
                UserRoles
            ),
            {reply, HasPermission, State};
        _ ->
            {reply, false, State} % User not found or not authenticated
    end;

handle_call(_Request, _From, State) ->
    {reply, {error, unknown_request}, State}.

handle_cast(_Msg, State) ->
    {noreply, State}.

handle_info(_Info, State) ->
    {noreply, State}.

terminate(_Reason, _State) ->
    ok.

code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

Securing Your Services

Once you have an authentication and authorization service, other services in your system can use it. A typical flow looks like this:

  1. Client Authenticates: Calls auth_service:login/2.
  2. Receives Session/Token: If successful, the client gets a session ID or token (e.g., a process ID, or a more complex JWT).
  3. Client Makes Authorized Request: When calling another service (e.g., data_service), the client includes its session/token and the action it wants to perform.
  4. Service Authorizes: The data_service calls auth_service:check_permission/2 using the client's identity and the requested action.
  5. Service Responds: If authorized, the action proceeds; otherwise, an error is returned.

Beyond Basic Auth

While our examples are simple, real-world systems need more:

  • Password Hashing: Never store plaintext passwords. Use strong hashing algorithms like bcrypt or pbkdf2.
  • Session Management: Securely generate, store, and validate session tokens. Ensure they expire and can be revoked.
  • Auditing: Log all authentication attempts and authorization checks for security monitoring and forensics.
  • External Identity Providers: Integrate with OAuth2/OpenID Connect for single sign-on.

Erlang's concurrency makes it great for building robust auth services.

AuthN vs AuthZ Check

Consider a user trying to access a secure document in an Erlang application.

Recap: Securing Services

We've covered the fundamentals of authentication and authorization in Erlang:

  • Authentication (AuthN) verifies identity ("Who are you?").
  • Authorization (AuthZ) determines permissions ("What can you do?").
  • We built a simple auth_service using GenServer for both user login and role-based access control (RBAC).
  • Understanding how to integrate these services is key to building secure and robust distributed Erlang applications.

Next, explore how to protect sensitive data itself within your Erlang applications.

常见问题解答

「身份验证与授权」课时是免费的吗？

是的 — 「身份验证与授权」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Erlang OTP: Distributed & Fault-Tolerant Systems Programming 课程的其余内容，请升级到 CoddyKit PRO。 Erlang OTP: Distributed & Fault-Tolerant Systems Programming 课程共包含 4 节课。

「身份验证与授权」这节课中我会学到什么？

为访问 Erlang 服务的进程和用户实现稳健的身份验证与授权机制。 你通过在浏览器中直接运行的动手代码来练习 Erlang OTP: Distributed & Fault-Tolerant Systems Programming，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

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无需任何先前经验。CoddyKit 上的 Erlang OTP: Distributed & Fault-Tolerant Systems Programming 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 2 节课，共 4 节。

「身份验证与授权」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

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此课程中的所有课时

  1. 安全节点通信（TLS）
  2. 身份验证与授权
  3. 保护敏感数据
  4. 强化分布式 Cookie 与节点访问控制
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