学习acegi-security

2006-06-10

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)。

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。

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。

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。

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。

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。

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;
    }
    .........
}