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AspNetCore3.1_Secutiry源码解析_5_Authentication_OAuth

2020-03-25 01:08 941 查看

title: "AspNetCore3.1_Secutiry源码解析_5_Authentication_OAuth"
date: 2020-03-24T23:27:45+08:00
draft: false
---

系列文章目录

OAuth简介

现在随便一个网站，不用注册，只用微信扫一扫，然后就可以自动登录，然后第三方网站右上角还出现了你的微信头像和昵称，怎么做到的？


sequenceDiagram
用户->>x站点: 请求微信登录
x站点->>微信: 请求 oauth token
微信->>用户: x站点请求基本资料权限,是否同意?
用户->>微信: 同意
微信->>x站点: token
x站点->>微信: 请求user基本资料(token)
微信->微信: 校验token
微信->>x站点: user基本资料

大概就这么个意思，OAuth可以让第三方获取有限的授权去获取资源。

入门的看博客

https://www.geek-share.com/detail/2694926000.html

英文好有基础的直接看协议

https://tools.ietf.org/html/rfc6749

依赖注入

配置类：OAuthOptions
处理器类： OAuthHandler

public static class OAuthExtensions
{
public static AuthenticationBuilder AddOAuth(this AuthenticationBuilder builder, string authenticationScheme, Action<OAuthOptions> configureOptions)
=> builder.AddOAuth<OAuthOptions, OAuthHandler<OAuthOptions>>(authenticationScheme, configureOptions);

public static AuthenticationBuilder AddOAuth(this AuthenticationBuilder builder, string authenticationScheme, string displayName, Action<OAuthOptions> configureOptions)
=> builder.AddOAuth<OAuthOptions, OAuthHandler<OAuthOptions>>(authenticationScheme, displayName, configureOptions);

public static AuthenticationBuilder AddOAuth<TOptions, THandler>(this AuthenticationBuilder builder, string authenticationScheme, Action<TOptions> configureOptions)
where TOptions : OAuthOptions, new()
where THandler : OAuthHandler<TOptions>
=> builder.AddOAuth<TOptions, THandler>(authenticationScheme, OAuthDefaults.DisplayName, configureOptions);

public static AuthenticationBuilder AddOAuth<TOptions, THandler>(this AuthenticationBuilder builder, string authenticationScheme, string displayName, Action<TOptions> configureOptions)
where TOptions : OAuthOptions, new()
where THandler : OAuthHandler<TOptions>
{
builder.Services.TryAddEnumerable(ServiceDescriptor.Singleton<IPostConfigureOptions<TOptions>, OAuthPostConfigureOptions<TOptions, THandler>>());
return builder.AddRemoteScheme<TOptions, THandler>(authenticationScheme, displayName, configureOptions);
}
}

OAuthOptions - 配置类

classDiagram class OAuthOptions{ ClientId ClientSecret AuthorizationEndpoint TokenEndPoint UserInformationEndPoint Scope Events ClaimActions StateDataFormat } class RemoteAuthenticationOptions{ BackchannelTimeout BackchannelHttpHandler Backchannel DataProtectionProvider CallbackPath AccessDeniedPath ReturnUrlParameter SignInScheme RemoteAuthenticationTimeout SaveTokens } class AuthenticationSchemeOptions{ } OAuthOptions-->RemoteAuthenticationOptions RemoteAuthenticationOptions-->AuthenticationSchemeOptions

下面是校验逻辑，这些配置是必需的。

public override void Validate()
{
base.Validate();

if (string.IsNullOrEmpty(ClientId))
{
throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, Resources.Exception_OptionMustBeProvided, nameof(ClientId)), nameof(ClientId));
}

if (string.IsNullOrEmpty(ClientSecret))
{
throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, Resources.Exception_OptionMustBeProvided, nameof(ClientSecret)), nameof(ClientSecret));
}

if (string.IsNullOrEmpty(AuthorizationEndpoint))
{
throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, Resources.Exception_OptionMustBeProvided, nameof(AuthorizationEndpoint)), nameof(AuthorizationEndpoint));
}

if (string.IsNullOrEmpty(TokenEndpoint))
{
throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, Resources.Exception_OptionMustBeProvided, nameof(TokenEndpoint)), nameof(TokenEndpoint));
}

if (!CallbackPath.HasValue)
{
throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, Resources.Exception_OptionMustBeProvided, nameof(CallbackPath)), nameof(CallbackPath));
}
}

OAuthPostConfigureOptions - 配置处理

  1. DataProtectionProvider没有配置的话则使用默认实现
  2. Backchannel没有配置的话则处理构造默认配置
  3. StateDataFormat没有配置的话则使用PropertiesDataFormat
public void PostConfigure(string name, TOptions options)
{
options.DataProtectionProvider = options.DataProtectionProvider ?? _dp;
if (options.Backchannel == null)
{
options.Backchannel = new HttpClient(options.BackchannelHttpHandler ?? new HttpClientHandler());
options.Backchannel.DefaultRequestHeaders.UserAgent.ParseAdd("Microsoft ASP.NET Core OAuth handler");
options.Backchannel.Timeout = options.BackchannelTimeout;
options.Backchannel.MaxResponseContentBufferSize = 1024 * 1024 * 10; // 10 MB
}

if (options.StateDataFormat == null)
{
var dataProtector = options.DataProtectionProvider.CreateProtector(
typeof(THandler).FullName, name, "v1");
options.StateDataFormat = new PropertiesDataFormat(dataProtector);
}
}

这个StateDataFormat就是处理state字段的加密解密的，state在认证过程中用于防止跨站伪造攻击和存放一些状态信息，我们看一下协议的定义

state
RECOMMENDED.  An opaque value used by the client to maintain
state between the request and callback.  The authorization
server includes this value when redirecting the user-agent back
to the client.  The parameter SHOULD be used for preventing
cross-site request forgery as described in Section 10.12.

比如，认证之后的回跳地址就是存放在这里。所以如果希望从state字段中解密得到信息的话，就需要使用到PropertiesDataFormat。PropertiesDataFormat没有任何代码，继承自SecureDataFormat。 为什么这里介绍这么多呢，因为实际项目中用到过这个。

public class SecureDataFormat<TData> : ISecureDataFormat<TData>
{
private readonly IDataSerializer<TData> _serializer;
private readonly IDataProtector _protector;

public SecureDataFormat(IDataSerializer<TData> serializer, IDataProtector protector)
{
_serializer = serializer;
_protector = protector;
}

public string Protect(TData data)
{
return Protect(data, purpose: null);
}

public string Protect(TData data, string purpose)
{
var userData = _serializer.Serialize(data);

var protector = _protector;
if (!string.IsNullOrEmpty(purpose))
{
protector = protector.CreateProtector(purpose);
}

var protectedData = protector.Protect(userData);
return Base64UrlTextEncoder.Encode(protectedData);
}

public TData Unprotect(string protectedText)
{
return Unprotect(protectedText, purpose: null);
}

public TData Unprotect(string protectedText, string purpose)
{
try
{
if (protectedText == null)
{
return default(TData);
}

var protectedData = Base64UrlTextEncoder.Decode(protectedText);
if (protectedData == null)
{
return default(TData);
}

var protector = _protector;
if (!string.IsNullOrEmpty(purpose))
{
protector = protector.CreateProtector(purpose);
}

var userData = protector.Unprotect(protectedData);
if (userData == null)
{
return default(TData);
}

return _serializer.Deserialize(userData);
}
catch
{
// TODO trace exception, but do not leak other information
return default(TData);
}
}
}

AddRemoteSchema和AddShema的差别就是做了下面的处理，确认始终有不是远程schema的SignInSchema

private class EnsureSignInScheme<TOptions> : IPostConfigureOptions<TOptions> where TOptions : RemoteAuthenticationOptions
{
private readonly AuthenticationOptions _authOptions;

public EnsureSignInScheme(IOptions<AuthenticationOptions> authOptions)
{
_authOptions = authOptions.Value;
}

public void PostConfigure(string name, TOptions options)
{
options.SignInScheme = options.SignInScheme ?? _authOptions.DefaultSignInScheme ?? _authOptions.DefaultScheme;
}
}

OAuthHandler

  • 解密state
  • 校验CorrelationId，防跨站伪造攻击
  • 如果error不为空说明失败返回错误
  • 拿到授权码code，换取token
  • 如果SaveTokens设置为true，将access_token,refresh_token,token_type存放到properties中
  • 创建凭据，返回成功
protected override async Task<HandleRequestResult> HandleRemoteAuthenticateAsync()
{
var query = Request.Query;

var state = query["state"];
var properties = Options.StateDataFormat.Unprotect(state);

if (properties == null)
{
return HandleRequestResult.Fail("The oauth state was missing or invalid.");
}

// OAuth2 10.12 CSRF
if (!ValidateCorrelationId(properties))
{
return HandleRequestResult.Fail("Correlation failed.", properties);
}

var error = query["error"];
if (!StringValues.IsNullOrEmpty(error))
{
// Note: access_denied errors are special protocol errors indicating the user didn't
// approve the authorization demand requested by the remote authorization server.
// Since it's a frequent scenario (that is not caused by incorrect configuration),
// denied errors are handled differently using HandleAccessDeniedErrorAsync().
// Visit https://tools.ietf.org/html/rfc6749#section-4.1.2.1 for more information.
if (StringValues.Equals(error, "access_denied"))
{
return await HandleAccessDeniedErrorAsync(properties);
}

var failureMessage = new StringBuilder();
failureMessage.Append(error);
var errorDescription = query["error_description"];
if (!StringValues.IsNullOrEmpty(errorDescription))
{
failureMessage.Append(";Description=").Append(errorDescription);
}
var errorUri = query["error_uri"];
if (!StringValues.IsNullOrEmpty(errorUri))
{
failureMessage.Append(";Uri=").Append(errorUri);
}

return HandleRequestResult.Fail(failureMessage.ToString(), properties);
}

var code = query["code"];

if (StringValues.IsNullOrEmpty(code))
{
return HandleRequestResult.Fail("Code was not found.", properties);
}

var tokens = await ExchangeCodeAsync(code, BuildRedirectUri(Options.CallbackPath));

if (tokens.Error != null)
{
return HandleRequestResult.Fail(tokens.Error, properties);
}

if (string.IsNullOrEmpty(tokens.AccessToken))
{
return HandleRequestResult.Fail("Failed to retrieve access token.", properties);
}

var identity = new ClaimsIdentity(ClaimsIssuer);

if (Options.SaveTokens)
{
var authTokens = new List<AuthenticationToken>();

authTokens.Add(new AuthenticationToken { Name = "access_token", Value = tokens.AccessToken });
if (!string.IsNullOrEmpty(tokens.RefreshToken))
{
authTokens.Add(new AuthenticationToken { Name = "refresh_token", Value = tokens.RefreshToken });
}

if (!string.IsNullOrEmpty(tokens.TokenType))
{
authTokens.Add(new AuthenticationToken { Name = "token_type", Value = tokens.TokenType });
}

if (!string.IsNullOrEmpty(tokens.ExpiresIn))
{
int value;
if (int.TryParse(tokens.ExpiresIn, NumberStyles.Integer, CultureInfo.InvariantCulture, out value))
{
// https://www.w3.org/TR/xmlschema-2/#dateTime
// https://msdn.microsoft.com/en-us/library/az4se3k1(v=vs.110).aspx
var expiresAt = Clock.UtcNow + TimeSpan.FromSeconds(value);
authTokens.Add(new AuthenticationToken
{
Name = "expires_at",
Value = expiresAt.ToString("o", CultureInfo.InvariantCulture)
});
}
}

properties.StoreTokens(authTokens);
}

var ticket = await CreateTicketAsync(identity, properties, tokens);
if (ticket != null)
{
return HandleRequestResult.Success(ticket);
}
else
{
return HandleRequestResult.Fail("Failed to retrieve user information from remote server.", properties);
}
}
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