shiro 密碼如何驗證？

Authentication：身份認證/登錄，驗證用戶是不是擁有相應的身份。

Authorization：授權，即權限驗證，驗證某個已認證的用戶是否擁有某個權限；即判斷用戶是否能做事情。

這里我們主要分析Authentication過程

一般在登陸方法中我們會這么寫：

 

Subject subject =SecurityUtils.getSubject();
UsernamePasswordToken token = new UsernamePasswordToken(username, password);
subject.login(token);

 

其中username,paasword為客戶端登陸請求傳過來的賬號密碼，現在我們只要知道 token中含有客戶端輸入的賬號密碼，那么怎么和數據庫中的做驗證呢？

再看spring中shiro的一部分xml配置：

MyRealm類：

@Service
public class MyRealm extends AuthorizingRealm {
   @Autowired
   private UserSerivce userService;
    @Override
    protected AuthorizationInfo doGetAuthorizationInfo(PrincipalCollection principals) {
        SimpleAuthorizationInfo info = new SimpleAuthorizationInfo();
        return info;
    }
    @Override
    protected AuthenticationInfo doGetAuthenticationInfo(AuthenticationToken authenticationToken)
            throws AuthenticationException {
        UsernamePasswordToken token = (UsernamePasswordToken) authenticationToken;
        String account= token.getUsername(); 
        User user = userService.getUserByAccount(account);
        return new SimpleAuthenticationInfo(user, user.getCpassword(), getName());
    }
 
    @Override
    public void setCredentialsMatcher(CredentialsMatcher credentialsMatcher) {
        HashedCredentialsMatcher shaCredentialsMatcher = new HashedCredentialsMatcher();
        shaCredentialsMatcher.setHashAlgorithmName("SHA-256");
        shaCredentialsMatcher.setHashIterations("1");
        super.setCredentialsMatcher(shaCredentialsMatcher);
    }
}

    上面securityManager是shiro的核心，其realm是我們自己定義的myRealm。doGetAuthorizationInfo跟授權相關我們先不看。大致上可以看出，doGetAuthenticationInfo方法返回的東西跟數據庫中實際的用戶名和密碼有關，setCredentialsMatcher方法跟加密規則有關。    

       回到最開始的三行代碼。subject.login(token)，入參的token帶有用戶輸入的賬號密碼，而我們的myRealm的方法返回值有數據庫中該賬號的密碼。那么最后肯定是兩者比較來進行認證。所以我們跟下subject.login方法。

DelegatingSubject：

 

public void login(AuthenticationToken token) throws AuthenticationException {
    clearRunAsIdentitiesInternal();
    Subject subject = securityManager.login(this, token);
    ......
}

因為我們的myRealm是在securityManager中，所以在跟下securityManager.login：

DefaultSecurityManager：

public Subject login(Subject subject, AuthenticationToken token) throws AuthenticationException {
    AuthenticationInfo info;
    try {
       //看這里
        info = authenticate(token);
    } catch (AuthenticationException ae) {
        try {
            onFailedLogin(token, ae, subject);
        } catch (Exception e) {
            if (log.isInfoEnabled()) {
                log.info("onFailedLogin method threw an " +
                        "exception.  Logging and propagating original AuthenticationException.", e);
            }
        }
        throw ae; //propagate
    }
 
    Subject loggedIn = createSubject(token, info, subject);
 
    onSuccessfulLogin(token, info, loggedIn);
 
    return loggedIn;
}

前面MyRealm的doGetAuthenticationInfo方法返回的是SimpleAuthenticationInfo，其實是 AuthenticationInfo的子類，所以我再看authenticate()方法，因為使用了代理模式，實際調用在Authenticator類的子類

AbstractAuthenticator：

public final AuthenticationInfo authenticate(AuthenticationToken token) throws AuthenticationException {
 
    if (token == null) {
        throw new IllegalArgumentException("Method argument (authentication token) cannot be null.");
    }
 
    log.trace("Authentication attempt received for token [{}]", token);
 
    AuthenticationInfo info;
    try {
        //看這里
        info = doAuthenticate(token);
        if (info == null) {
            String msg = "No account information found for authentication token [" + token + "] by this " +
                    "Authenticator instance.  Please check that it is configured correctly.";
            throw new AuthenticationException(msg);
        }
    } catch (Throwable t) {
        AuthenticationException ae = null;
        if (t instanceof AuthenticationException) {
            ae = (AuthenticationException) t;
        }
        if (ae == null) {
            //Exception thrown was not an expected AuthenticationException.  Therefore it is probably a little more
            //severe or unexpected.  So, wrap in an AuthenticationException, log to warn, and propagate:
            String msg = "Authentication failed for token submission [" + token + "].  Possible unexpected " +
                    "error? (Typical or expected login exceptions should extend from AuthenticationException).";
            ae = new AuthenticationException(msg, t);
            if (log.isWarnEnabled())
                log.warn(msg, t);
        }
        try {
            notifyFailure(token, ae);
        } catch (Throwable t2) {
            if (log.isWarnEnabled()) {
                String msg = "Unable to send notification for failed authentication attempt - listener error?.  " +
                        "Please check your AuthenticationListener implementation(s).  Logging sending exception " +
                        "and propagating original AuthenticationException instead...";
                log.warn(msg, t2);
            }
        }
 
 
        throw ae;
    }
 
    log.debug("Authentication successful for token [{}].  Returned account [{}]", token, info);
 
    notifySuccess(token, info);
 
    return info;
}

又是一個方法返回AuthenticationInfo，再看下去。

ModularRealmAuthenticator：

protected AuthenticationInfo doAuthenticate(AuthenticationToken authenticationToken) throws AuthenticationException {
    assertRealmsConfigured();
    Collection<Realm> realms = getRealms();
    if (realms.size() == 1) {
        //看這里
        return doSingleRealmAuthentication(realms.iterator().next(), authenticationToken);
    } else {
        return doMultiRealmAuthentication(realms, authenticationToken);
    }
}
 
protected AuthenticationInfo doSingleRealmAuthentication(Realm realm, AuthenticationToken token) {
    if (!realm.supports(token)) {
        String msg = "Realm [" + realm + "] does not support authentication token [" +
                token + "].  Please ensure that the appropriate Realm implementation is " +
                "configured correctly or that the realm accepts AuthenticationTokens of this type.";
        throw new UnsupportedTokenException(msg);
    }
    //看這里
    AuthenticationInfo info = realm.getAuthenticationInfo(token);
    if (info == null) {
        String msg = "Realm [" + realm + "] was unable to find account data for the " +
                "submitted AuthenticationToken [" + token + "].";
        throw new UnknownAccountException(msg);
    }
    return info;
}
 

我們就一個realm所以看doSingleRealmAuthentication，這次終於看到我們熟悉的MyRealm里的方法了？不對,還少了個do。繼續跟進。

AuthenticatingRealm：

 

public final AuthenticationInfo getAuthenticationInfo(AuthenticationToken token) throws AuthenticationException {
 
    AuthenticationInfo info = getCachedAuthenticationInfo(token);
    if (info == null) {
        //otherwise not cached, perform the lookup:
        info = doGetAuthenticationInfo(token);
        log.debug("Looked up AuthenticationInfo [{}] from doGetAuthenticationInfo", info);
        if (token != null && info != null) {
            cacheAuthenticationInfoIfPossible(token, info);
        }
    } else {
        log.debug("Using cached authentication info [{}] to perform credentials matching.", info);
    }
 
    if (info != null) {
        assertCredentialsMatch(token, info);
    } else {
        log.debug("No AuthenticationInfo found for submitted AuthenticationToken [{}].  Returning null.", token);
    }
 
    return info;
}
 
protected void assertCredentialsMatch(AuthenticationToken token, AuthenticationInfo info) throws AuthenticationException {
    CredentialsMatcher cm = getCredentialsMatcher();
    if (cm != null) {
        if (!cm.doCredentialsMatch(token, info)) {
            //not successful - throw an exception to indicate this:
            String msg = "Submitted credentials for token [" + token + "] did not match the expected credentials.";
            throw new IncorrectCredentialsException(msg);
        }
    } else {
        throw new AuthenticationException("A CredentialsMatcher must be configured in order to verify " +
                "credentials during authentication.  If you do not wish for credentials to be examined, you " +
                "can configure an " + AllowAllCredentialsMatcher.class.getName() + " instance.");
    }
}

      這個方法才是重頭。整體邏輯就是，先從緩存根據token取認證信息（AuthenticationInfo），若沒有，則調用我們自己實現的MyRealm中的doGetAuthenticationInfo去獲取，然后嘗試緩存，最后再通過assertCredentialsMatch去驗證token和info,assertCredentialsMatch則會根據MyReaml中setCredentialsMatcher我們設置的加密方式去進行相應的驗證。

　　整個流程的牽涉到的uml圖：

 我們在xml配置文件中配置的MyRealm會被放到RealmSecurityManager的reals集合中，也就是說SercurityManager和下圖中的AuthenticatingRealm是一對多的關系。

 

 

總結：一路跟蹤下來其實學到不少，比如ModularRealmAuthenticator類中如果realm有多個那會走doMultiRealmAuthentication()方法，而ModularRealmAuthenticator類有個authenticationStrategy屬性，在doMultiRealmAuthentication()方法中有用到，看名字就知道，使用了策略模式實現了各種realm的匹配規則。總而言之，流行起來的框架隨便看一看都會有很多收獲，希望有一天自己也能寫出這樣的代碼。