学习acegi-security (转载)

学习acegi-security
这几天对acegi研究了一下，现对这几天的研究做个总结。

网上资料对于acegi在web上的应用非常多，所以特意不从web入手，而从一般的java方法入手。

acegi的基本原理就是利用拦截器，对请求进行拦截，在拦截前和拦截后做些安全验证，以达到安全目的。所谓安全，一般包括两个部分，一为认证(authentication),二为授权(authorization)。

1，拦截器体系
acegi中拦截器为分为三类：
(1)filter拦截器(FilterSecurityInterceptor),主要对web应用进行拦截，即利用servlet的filter进行拦截。
(2)method拦截器，分为spring的method拦截器(MethodSecurityInterceptor)和aspectj的method拦截器(AspectJSecurityInterceptor)。


代码
public abstract class AbstractSecurityInterceptor implements InitializingBean, ApplicationEventPublisherAware,  
    MessageSourceAware {  
    private AccessDecisionManager accessDecisionManager;  
    private AfterInvocationManager afterInvocationManager;  
    private ApplicationEventPublisher eventPublisher;  
    private AuthenticationManager authenticationManager;  
    protected MessageSourceAccessor messages = AcegiMessageSource.getAccessor();  
    private RunAsManager runAsManager = new NullRunAsManager();  
    private boolean alwaysReauthenticate = false;  
    private boolean rejectPublicInvocations = false;  
    private boolean validateConfigAttributes = true;  
    .........  
 
    protected Object afterInvocation(InterceptorStatusToken token, Object returnedObject) {  
       ............  
    SecurityContextHolder.getContext().setAuthentication(token.getAuthentication());  
    ............  
       if (afterInvocationManager != null) {  
            returnedObject = afterInvocationManager.decide(token.getAuthentication(), token.getSecureObject(),token.getAttr(), returnedObject);  
        }  
       ............  
    }  
 
    protected InterceptorStatusToken beforeInvocation(Object object) {          
      ............  
         authenticated = this.authenticationManager.authenticate(SecurityContextHolder.getContext().getAuthentication());  
      ............  
         this.accessDecisionManager.decide(authenticated, object, attr);  
         ............  
         Authentication runAs = this.runAsManager.buildRunAs(authenticated, object, attr);  
         if (runAs == null) {  
        ............  
              return new InterceptorStatusToken(authenticated, false, attr, object);   
         } else {  
        ............  
              SecurityContextHolder.getContext().setAuthentication(runAs);  
              return new InterceptorStatusToken(authenticated, true, attr, object);   
         }  
      ............  
    }  
}  
 
public class FilterSecurityInterceptor extends AbstractSecurityInterceptor implements Filter {  
     public void invoke(FilterInvocation fi) throws IOException, ServletException {  
        if ((fi.getRequest() != null) && (fi.getRequest().getAttribute(FILTER_APPLIED) != null)  
            && observeOncePerRequest) {  
             
            fi.getChain().doFilter(fi.getRequest(), fi.getResponse());  
        } else {  
             
            if (fi.getRequest() != null) {  
                fi.getRequest().setAttribute(FILTER_APPLIED, Boolean.TRUE);  
            }  
 
            InterceptorStatusToken token = super.beforeInvocation(fi);  
 
            try {  
                fi.getChain().doFilter(fi.getRequest(), fi.getResponse());  
            } finally {  
                super.afterInvocation(token, null);  
            }  
        }  
    }  
    ............  
}  
 
public class MethodSecurityInterceptor extends AbstractSecurityInterceptor implements MethodInterceptor {      
    public Object invoke(MethodInvocation mi) throws Throwable {  
        Object result = null;  
        InterceptorStatusToken token = super.beforeInvocation(mi);  
 
        try {  
            result = mi.proceed();  
        } finally {  
            result = super.afterInvocation(token, result);  
        }  
 
        return result;  
    }  
    ............  
}  
 
public class AspectJSecurityInterceptor extends AbstractSecurityInterceptor {  
     public Object invoke(JoinPoint jp, AspectJCallback advisorProceed) {  
        Object result = null;  
        InterceptorStatusToken token = super.beforeInvocation(jp);  
 
        try {  
            result = advisorProceed.proceedWithObject();  
        } finally {  
            result = super.afterInvocation(token, result);  
        }  
 
        return result;  
    }  
    ............  
} 


上面的代码片断已经显示,所有的真正参与验证的代码都在父类AbstractSecurityInterceptor.beforeInvocation()之中进行，而对于拦截器都只是做些委托罢了。这样可以把具体的验证代码同拦截器分开，也有利于扩展，用其他的aop技术或拦截器进行扩展，可以很轻松。

认证体系由AuthenticationManager负责，授权体系由AccessDecisionManager负责，RunAsManager 是作为用户身份转换的手段。AfterInvocationManager留下了一个接口，可以扩展默认的授权体系，可以做一些其他额外的工作。

在AbstractSecurityInterceptor.beforeInvocation()中，
首先进行认证，authenticated = this.authenticationManager.authenticate(SecurityContextHolder.getContext().getAuthentication());
其次进行授权，this.accessDecisionManager.decide(authenticated, object, attr);

AbstractSecurityInterceptor.afterInvocation()中，
做其他扩展，returnedObject = afterInvocationManager.decide(token.getAuthentication(), token.getSecureObject(),token.getAttr(), returnedObject);

2，认证体系
2.1认证管理器
认证体系的核心为AuthenticationManager，他的方法authenticate(Authentication authentication)负责所有的认证。在acegi中，由具体类ProviderManager来进行认证过程。


代码
public interface AuthenticationManager {  
    public Authentication authenticate(Authentication authentication)  
        throws AuthenticationException;  
}  
 
public abstract class AbstractAuthenticationManager  
    implements AuthenticationManager{  
    public final Authentication authenticate(Authentication authRequest)  
        throws AuthenticationException {  
        try {  
            Authentication authResult = doAuthentication(authRequest);  
            copyDetails(authRequest, authResult);  
 
            return authResult;  
        } catch (AuthenticationException e) {  
            e.setAuthentication(authRequest);  
            throw e;  
        }  
    }  
 
    private void copyDetails(Authentication source, Authentication dest) {  
        if ((dest instanceof AbstractAuthenticationToken) && (dest.getDetails() == null)) {  
            AbstractAuthenticationToken token = (AbstractAuthenticationToken) dest;  
 
            token.setDetails(source.getDetails());  
        }  
    }  
 
    protected abstract Authentication doAuthentication(Authentication authentication)  
        throws AuthenticationException;  
 
    .........  
}  
 
public class ProviderManager extends AbstractAuthenticationManager implements InitializingBean,  
    ApplicationEventPublisherAware, MessageSourceAware {  
    private List providers;  
    ............  
    public Authentication doAuthentication(Authentication authentication)  
        throws AuthenticationException {  
     .........  
        Iterator iter = providers.iterator();  
        ............  
        while (iter.hasNext()) {  
            .............  
            AuthenticationProvider provider = (AuthenticationProvider) iter.next();  
            .........  
            result = provider.authenticate(authentication);  
            ............  
        }  
        ............  
    }  
    .........  
} 


从上面代码片断可以看出，真正的认证过程是在ProviderManager.doAuthentication()中进行的。而ProviderManager并不是具体的认证者，他只是个管理器，它要将具体的认证过程委托给具体的认证器提供者AuthenticationProvider去做。

2.2认证提供者
认证提供者就有很多了，可以提供各种各样的认证。如dao,ldap,anonymous,authbyadapter，cas,jaas,remeberme,remote,runnasimpl,testing,x509等。


代码
public interface AuthenticationProvider {  
    public Authentication authenticate(Authentication authentication) throws AuthenticationException;  
    public boolean supports(Class authentication);  
} 


具体的认证提供者类就不详细分析了，只提个名字：DaoAuthenticationProvider,LdapAuthenticationProvider，AnonymousAuthenticationProvider，AuthByAdapterProvider，CasAuthenticationProvider，JaasAuthenticationProvider，RememberMeAuthenticationProvider，RemoteAuthenticationProvider，RunAsImplAuthenticationProvider，TestingAuthenticationProvider，X509AuthenticationProvider。

3，授权体系
3.1授权管理器
授权体系的核心为授权管理器(AccessDecisionManager)，它的方法decide(Authentication authentication, Object object, ConfigAttributeDefinition config)进行具体的授权动作。


代码
public interface AccessDecisionManager {  
     
    public void decide(Authentication authentication, Object object, ConfigAttributeDefinition config)  
        throws AccessDeniedException, InsufficientAuthenticationException;  
    public boolean supports(ConfigAttribute attribute);  
    public boolean supports(Class clazz);  
}  
 
public abstract class AbstractAccessDecisionManager implements AccessDecisionManager, InitializingBean,  
    MessageSourceAware {  
    private List decisionVoters;  
    protected MessageSourceAccessor messages = AcegiMessageSource.getAccessor();  
    private boolean allowIfAllAbstainDecisions = false;  
 
    public boolean supports(ConfigAttribute attribute) {  
        Iterator iter = this.decisionVoters.iterator();  
 
        while (iter.hasNext()) {  
            AccessDecisionVoter voter = (AccessDecisionVoter) iter.next();  
 
            if (voter.supports(attribute)) {  
                return true;  
            }  
        }  
 
        return false;  
    }  
 
    public boolean supports(Class clazz) {  
        Iterator iter = this.decisionVoters.iterator();  
 
        while (iter.hasNext()) {  
            AccessDecisionVoter voter = (AccessDecisionVoter) iter.next();  
 
            if (!voter.supports(clazz)) {  
                return false;  
            }  
        }  
 
        return true;  
    }  
    ..............  
}  
 
public class AffirmativeBased extends AbstractAccessDecisionManager {  
    public void decide(Authentication authentication, Object object, ConfigAttributeDefinition config)  
        throws AccessDeniedException {  
        Iterator iter = this.getDecisionVoters().iterator();  
        int deny = 0;  
 
        while (iter.hasNext()) {  
            AccessDecisionVoter voter = (AccessDecisionVoter) iter.next();  
            int result = voter.vote(authentication, object, config);  
 
            switch (result) {  
            case AccessDecisionVoter.ACCESS_GRANTED:  
                return;  
 
            case AccessDecisionVoter.ACCESS_DENIED:  
                deny++;  
 
                break;  
 
            default:  
                break;  
            }  
        }  
 
        if (deny > 0) {  
            throw new AccessDeniedException(messages.getMessage("AbstractAccessDecisionManager.accessDenied",  
                    "Access is denied"));  
        }  
 
        // To get this far, every AccessDecisionVoter abstained  
        checkAllowIfAllAbstainDecisions();  
    }  
    ..............  
}  
 
public class ConsensusBased extends AbstractAccessDecisionManager {  
    public void decide(Authentication authentication, Object object, ConfigAttributeDefinition config)  
        throws AccessDeniedException {  
        Iterator iter = this.getDecisionVoters().iterator();  
        int grant = 0;  
        int deny = 0;  
        int abstain = 0;  
 
        while (iter.hasNext()) {  
            AccessDecisionVoter voter = (AccessDecisionVoter) iter.next();  
            int result = voter.vote(authentication, object, config);  
 
            switch (result) {  
            case AccessDecisionVoter.ACCESS_GRANTED:  
                grant++;  
 
                break;  
 
            case AccessDecisionVoter.ACCESS_DENIED:  
                deny++;  
 
                break;  
 
            default:  
                abstain++;  
 
                break;  
            }  
        }  
 
        if (grant > deny) {  
            return;  
        }  
 
        if (deny > grant) {  
            throw new AccessDeniedException(messages.getMessage("AbstractAccessDecisionManager.accessDenied",  
                    "Access is denied"));  
        }  
 
        if ((grant == deny) && (grant != 0)) {  
            if (this.allowIfEqualGrantedDeniedDecisions) {  
                return;  
            } else {  
                throw new AccessDeniedException(messages.getMessage("AbstractAccessDecisionManager.accessDenied",  
                        "Access is denied"));  
            }  
        }  
 
        // To get this far, every AccessDecisionVoter abstained  
        checkAllowIfAllAbstainDecisions();  
    }  
    ..............  
}  
 
public class UnanimousBased extends AbstractAccessDecisionManager {  
    public void decide(Authentication authentication, Object object, ConfigAttributeDefinition config)  
        throws AccessDeniedException {  
        int grant = 0;  
        int abstain = 0;  
 
        Iterator configIter = config.getConfigAttributes();  
 
        while (configIter.hasNext()) {  
            ConfigAttributeDefinition thisDef = new ConfigAttributeDefinition();  
            thisDef.addConfigAttribute((ConfigAttribute) configIter.next());  
 
            Iterator voters = this.getDecisionVoters().iterator();  
 
            while (voters.hasNext()) {  
                AccessDecisionVoter voter = (AccessDecisionVoter) voters.next();  
                int result = voter.vote(authentication, object, thisDef);  
 
                switch (result) {  
                case AccessDecisionVoter.ACCESS_GRANTED:  
                    grant++;  
 
                    break;  
 
                case AccessDecisionVoter.ACCESS_DENIED:  
                    throw new AccessDeniedException(messages.getMessage("AbstractAccessDecisionManager.accessDenied",  
                            "Access is denied"));  
 
                default:  
                    abstain++;  
 
                    break;  
                }  
            }  
        }  
 
        // To get this far, there were no deny votes  
        if (grant > 0) {  
            return;  
        }  
 
        // To get this far, every AccessDecisionVoter abstained  
        checkAllowIfAllAbstainDecisions();  
    }  
    ..............  
} 


授权管理器AccessDecisionManager默认有三个实现，具体为AffirmativeBased，ConsensusBased，UnanimousBased。三个具体实现都大同小异，主要在具有角色是否应该授权上。
而具体能否单个角色是否授权，是委派给AccessDecisionVoter去做的。

3.2授权投票者
授权投票责的核心是接口AccessDecisionVoter。他有几个具体实现类：BasicAclEntryVoter，AuthenticatedVoter，RoleVoter。


代码
public interface AccessDecisionVoter {  
     
    public static final int ACCESS_GRANTED = 1;  
    public static final int ACCESS_ABSTAIN = 0;  
    public static final int ACCESS_DENIED = -1;  
 
    public boolean supports(ConfigAttribute attribute);  
    public boolean supports(Class clazz);  
    public int vote(Authentication authentication, Object object, ConfigAttributeDefinition config);  
}  
 
public abstract class AbstractAclVoter implements AccessDecisionVoter {  
    public boolean supports(Class clazz) {  
        if (MethodInvocation.class.isAssignableFrom(clazz)) {  
            return true;  
        } else if (JoinPoint.class.isAssignableFrom(clazz)) {  
            return true;  
        } else {  
            return false;  
        }  
    }  
    ............  
}  
 
public class BasicAclEntryVoter extends AbstractAclVoter implements InitializingBean {    
    private AclManager aclManager;  
    private String internalMethod;  
    private String processConfigAttribute;  
    private int[] requirePermission;  
 
    public boolean supports(ConfigAttribute attribute) {  
        if ((attribute.getAttribute() != null) && attribute.getAttribute().startsWith(getProcessConfigAttribute())) {  
            return true;  
        } else {  
            return false;  
        }  
    }  
 
    public int vote(Authentication authentication, Object object, ConfigAttributeDefinition config) {  
        Iterator iter = config.getConfigAttributes();  
 
        while (iter.hasNext()) {  
            ConfigAttribute attr = (ConfigAttribute) iter.next();  
 
            if (this.supports(attr)) {  
                // Need to make an access decision on this invocation  
                // Attempt to locate the domain object instance to process  
                Object domainObject = getDomainObjectInstance(object);  
 
                // If domain object is null, vote to abstain  
                if (domainObject == null) {  
                    if (logger.isDebugEnabled()) {  
                        logger.debug("Voting to abstain - domainObject is null");  
                    }  
 
                    return AccessDecisionVoter.ACCESS_ABSTAIN;  
                }  
 
                // Evaluate if we are required to use an inner domain object  
                if ((internalMethod != null) && !"".equals(internalMethod)) {  
                    try {  
                        Class clazz = domainObject.getClass();  
                        Method method = clazz.getMethod(internalMethod, new Class[] {});  
                        domainObject = method.invoke(domainObject, new Object[] {});  
                    } catch (NoSuchMethodException nsme) {  
                        throw new AuthorizationServiceException("Object of class '" + domainObject.getClass()  
                            + "' does not provide the requested internalMethod: " + internalMethod);  
                    } catch (IllegalAccessException iae) {  
                        if (logger.isDebugEnabled()) {  
                            logger.debug("IllegalAccessException", iae);  
 
                            if (iae.getCause() != null) {  
                                logger.debug("Cause: " + iae.getCause().getMessage(), iae.getCause());  
                            }  
                        }  
 
                        throw new AuthorizationServiceException("Problem invoking internalMethod: " + internalMethod  
                            + " for object: " + domainObject);  
                    } catch (InvocationTargetException ite) {  
                        if (logger.isDebugEnabled()) {  
                            logger.debug("InvocationTargetException", ite);  
 
                            if (ite.getCause() != null) {  
                                logger.debug("Cause: " + ite.getCause().getMessage(), ite.getCause());  
                            }  
                        }  
 
                        throw new AuthorizationServiceException("Problem invoking internalMethod: " + internalMethod  
                            + " for object: " + domainObject);  
                    }  
                }  
 
                // Obtain the ACLs applicable to the domain object  
                AclEntry[] acls = aclManager.getAcls(domainObject, authentication);  
 
                // If principal has no permissions for domain object, deny  
                if ((acls == null) || (acls.length == 0)) {  
                    if (logger.isDebugEnabled()) {  
                        logger.debug("Voting to deny access - no ACLs returned for this principal");  
                    }  
 
                    return AccessDecisionVoter.ACCESS_DENIED;  
                }  
 
                // Principal has some permissions for domain object, check them  
                for (int i = 0; i < acls.length; i++) {  
                    // Locate processable AclEntrys  
                    if (acls[i] instanceof BasicAclEntry) {  
                        BasicAclEntry processableAcl = (BasicAclEntry) acls[i];  
 
                        // See if principal has any of the required permissions  
                        for (int y = 0; y < requirePermission.length; y++) {  
                            if (processableAcl.isPermitted(requirePermission[y])) {  
                                if (logger.isDebugEnabled()) {  
                                    logger.debug("Voting to grant access");  
                                }  
 
                                return AccessDecisionVoter.ACCESS_GRANTED;  
                            }  
                        }  
                    }  
                }  
 
                // No permissions match  
                if (logger.isDebugEnabled()) {  
                    logger.debug(  
                        "Voting to deny access - ACLs returned, but insufficient permissions for this principal");  
                }  
 
                return AccessDecisionVoter.ACCESS_DENIED;  
            }  
        }  
 
        return AccessDecisionVoter.ACCESS_ABSTAIN;  
    }  
    ...............  
}  
 
public class AuthenticatedVoter implements AccessDecisionVoter {  
 
    public static final String IS_AUTHENTICATED_FULLY = "IS_AUTHENTICATED_FULLY";  
    public static final String IS_AUTHENTICATED_REMEMBERED = "IS_AUTHENTICATED_REMEMBERED";  
    public static final String IS_AUTHENTICATED_ANONYMOUSLY = "IS_AUTHENTICATED_ANONYMOUSLY";  
 
    private AuthenticationTrustResolver authenticationTrustResolver = new AuthenticationTrustResolverImpl();  
 
    private boolean isFullyAuthenticated(Authentication authentication) {  
        return (!authenticationTrustResolver.isAnonymous(authentication)  
        && !authenticationTrustResolver.isRememberMe(authentication));  
    }  
 
    public void setAuthenticationTrustResolver(AuthenticationTrustResolver authenticationTrustResolver) {  
        Assert.notNull(authenticationTrustResolver, "AuthenticationTrustResolver cannot be set to null");  
        this.authenticationTrustResolver = authenticationTrustResolver;  
    }  
 
    public boolean supports(ConfigAttribute attribute) {  
        if ((attribute.getAttribute() != null)  
            && (IS_AUTHENTICATED_FULLY.equals(attribute.getAttribute())  
            || IS_AUTHENTICATED_REMEMBERED.equals(attribute.getAttribute())  
            || IS_AUTHENTICATED_ANONYMOUSLY.equals(attribute.getAttribute()))) {  
            return true;  
        } else {  
            return false;  
        }  
    }  
 
    public boolean supports(Class clazz) {  
        return true;  
    }  
 
    public int vote(Authentication authentication, Object object, ConfigAttributeDefinition config) {  
        int result = ACCESS_ABSTAIN;  
        Iterator iter = config.getConfigAttributes();  
 
        while (iter.hasNext()) {  
            ConfigAttribute attribute = (ConfigAttribute) iter.next();  
 
            if (this.supports(attribute)) {  
                result = ACCESS_DENIED;  
 
                if (IS_AUTHENTICATED_FULLY.equals(attribute.getAttribute())) {  
                    if (isFullyAuthenticated(authentication)) {  
                        return ACCESS_GRANTED;  
                    }  
                }  
 
                if (IS_AUTHENTICATED_REMEMBERED.equals(attribute.getAttribute())) {  
                    if (authenticationTrustResolver.isRememberMe(authentication)  
                        || isFullyAuthenticated(authentication)) {  
                        return ACCESS_GRANTED;  
                    }  
                }  
 
                if (IS_AUTHENTICATED_ANONYMOUSLY.equals(attribute.getAttribute())) {  
                    if (authenticationTrustResolver.isAnonymous(authentication) || isFullyAuthenticated(authentication)  
                        || authenticationTrustResolver.isRememberMe(authentication)) {  
                        return ACCESS_GRANTED;  
                    }  
                }  
            }  
        }  
 
        return result;  
    }  
}  
 
public class RoleVoter implements AccessDecisionVoter {  
    private String rolePrefix = "ROLE_";  
 
    public boolean supports(ConfigAttribute attribute) {  
        if ((attribute.getAttribute() != null) && attribute.getAttribute().startsWith(getRolePrefix())) {  
            return true;  
        } else {  
            return false;  
        }  
    }  
 
    public boolean supports(Class clazz) {  
        return true;  
    }  
 
    public int vote(Authentication authentication, Object object, ConfigAttributeDefinition config) {  
        int result = ACCESS_ABSTAIN;  
        Iterator iter = config.getConfigAttributes();  
 
        while (iter.hasNext()) {  
            ConfigAttribute attribute = (ConfigAttribute) iter.next();  
 
            if (this.supports(attribute)) {  
                result = ACCESS_DENIED;  
 
                for (int i = 0; i < authentication.getAuthorities().length; i++) {  
                    if (attribute.getAttribute().equals(authentication.getAuthorities()[i].getAuthority())) {  
                        return ACCESS_GRANTED;  
                    }  
                }  
            }  
        }  
        return result;  
    }  
} 


这三个授权投票实现类中 acl 又最复杂。他会委托给acl管理器(AclManager)来做具体的授权工作。

3.3acl授权体系
AclManager只有一个实现类AclProviderManager ,负责提供acl授权实体。


代码
public interface AclManager {  
     
    public AclEntry[] getAcls(Object domainInstance);  
    public AclEntry[] getAcls(Object domainInstance, Authentication authentication);  
}  
 
public class AclProviderManager implements AclManager, InitializingBean {    
    public AclEntry[] getAcls(Object domainInstance) {  
        Assert.notNull(domainInstance, "domainInstance is null - violating interface contract");  
 
        Iterator iter = providers.iterator();  
 
        while (iter.hasNext()) {  
            AclProvider provider = (AclProvider) iter.next();  
 
            if (provider.supports(domainInstance)) {  
                if (logger.isDebugEnabled()) {  
                    logger.debug("ACL lookup using " + provider.getClass().getName());  
                }  
 
                return provider.getAcls(domainInstance);  
            }  
        }  
 
        if (logger.isDebugEnabled()) {  
            logger.debug("No AclProvider found for " + domainInstance.toString());  
        }  
 
        return null;  
    }  
 
    public AclEntry[] getAcls(Object domainInstance, Authentication authentication) {  
        Assert.notNull(domainInstance, "domainInstance is null - violating interface contract");  
        Assert.notNull(authentication, "authentication is null - violating interface contract");  
 
        Iterator iter = providers.iterator();  
 
        while (iter.hasNext()) {  
            AclProvider provider = (AclProvider) iter.next();  
 
            if (provider.supports(domainInstance)) {  
                if (logger.isDebugEnabled()) {  
                    logger.debug("ACL lookup using " + provider.getClass().getName());  
                }  
 
                return provider.getAcls(domainInstance, authentication);  
            } else {  
                if (logger.isDebugEnabled()) {  
                    logger.debug("Provider " + provider.toString() + " does not support " + domainInstance);  
                }  
            }  
        }  
 
        if (logger.isDebugEnabled()) {  
            logger.debug("No AclProvider found for " + domainInstance.toString());  
        }  
 
        return null;  
    }  
    .........  
}