快速定位log4j新漏洞影响的项目

第一步：将FossEye知识库更新至最新版本

第二步：【项目管理】全量扫描代码仓库

第三步【资产管理-漏洞】根据漏洞id搜索“CVE-2021-44228”，点击查看影响项目数

第四步溯源页面显示出该漏洞影响的所有项目，点击放大镜图标可查看代码具体位置

漏洞详情

漏洞概述

此次Apache Log4j2 漏洞是用于 Log4j2 提供的 lookup 功能造成的，该功能允许开发者通过一些协议去读取相应环境中的配置。但在实现的过程中，并未对输入进行严格的判断，从而造成漏洞的发生。恶意攻击者可以利用该漏洞注入恶意class文件从而执行任意命令。

漏洞编号

CVE-2021-44228

漏洞危险等级：严重

影响版本

Apache Log4j <=2.15.0-rc1

可能的受影响应用包括但不限于如下：

• Spring-Boot-strater-log4j2

• Apache Struts2

• Apache Solr

• Apache Flink

• Apache Druid

• ElasticSearch

• flume

• dubbo

• Redis

• logstash

• kafka

漏洞复现

漏洞分析

略去一些非关键流程，日志信息最终会进入MessagePatternConverter.java 文件的format方法，如下图，当日志信息中出现 "${"关键字 则通过StrSubstitutor.java的replace方法对其进行替换和解析

最终通过StrSubstitutor.java文件中的substitute方法对传入的日志信息进行替换。这个函数主要作用就是提取出日志信息中的${}信息，并根据内容调用。varName就是提取出来的关键信息，最关键的位置如下：

在lookup中，prefix是对应配置类，name是其参数并通过调用对应方法进行解析。

lookup保存有如下解析类：

最终在JndiLookup.java中触发漏洞

堆栈：

lookup:172, JndiManager (org.apache.logging.log4j.core.net)
lookup:56, JndiLookup (org.apache.logging.log4j.core.lookup)
lookup:184, Interpolator (org.apache.logging.log4j.core.lookup)
resolveVariable:1054, StrSubstitutor (org.apache.logging.log4j.core.lookup)
substitute:976, StrSubstitutor (org.apache.logging.log4j.core.lookup)
substitute:872, StrSubstitutor (org.apache.logging.log4j.core.lookup)
replace:427, StrSubstitutor (org.apache.logging.log4j.core.lookup)
format:132, MessagePatternConverter (org.apache.logging.log4j.core.pattern)
format:38, PatternFormatter (org.apache.logging.log4j.core.pattern)
toSerializable:334, PatternLayout$PatternSerializer (org.apache.logging.log4j.core.layout)
toText:233, PatternLayout (org.apache.logging.log4j.core.layout)
encode:218, PatternLayout (org.apache.logging.log4j.core.layout)
encode:58, PatternLayout (org.apache.logging.log4j.core.layout)
directEncodeEvent:177, AbstractOutputStreamAppender (org.apache.logging.log4j.core.appender)
tryAppend:170, AbstractOutputStreamAppender (org.apache.logging.log4j.core.appender)
append:161, AbstractOutputStreamAppender (org.apache.logging.log4j.core.appender)
tryCallAppender:156, AppenderControl (org.apache.logging.log4j.core.config)
callAppender0:129, AppenderControl (org.apache.logging.log4j.core.config)
callAppenderPreventRecursion:120, AppenderControl (org.apache.logging.log4j.core.config)
callAppender:84, AppenderControl (org.apache.logging.log4j.core.config)
callAppenders:448, LoggerConfig (org.apache.logging.log4j.core.config)
processLogEvent:433, LoggerConfig (org.apache.logging.log4j.core.config)
log:417, LoggerConfig (org.apache.logging.log4j.core.config)
log:403, LoggerConfig (org.apache.logging.log4j.core.config)
log:49, DefaultReliabilityStrategy (org.apache.logging.log4j.core.config)
logMessage:146, Logger (org.apache.logging.log4j.core)
log:2117, AbstractLogger (org.apache.logging.log4j.spi)
tryLogMessage:2205, AbstractLogger (org.apache.logging.log4j.spi)
logMessageTrackRecursion:2159, AbstractLogger (org.apache.logging.log4j.spi)
logMessageSafely:2142, AbstractLogger (org.apache.logging.log4j.spi)
logMessage:2017, AbstractLogger (org.apache.logging.log4j.spi)
logIfEnabled:1983, AbstractLogger (org.apache.logging.log4j.spi)
error:740, AbstractLogger (org.apache.logging.log4j.spi)
main:14, log4j (com.z)

修复建议

官方修复链接如下：

https://github.com/apache/logging-log4j2/releases/tag/log4j-2.15.0-rc2

临时解决方案（三选一）：

（1） 修改jvm参数 -Dlog4j2.formatMsgNoLookups=true

（2） 修改配置log4j2.formatMsgNoLookups=True

（3） 将系统环境变量 FORMAT_MESSAGES_PATTERN_DISABLE_LOOKUPS 设置为 true

参考链接

https://nvd.nist.gov/vuln/detail/CVE-2021-44228
https://github.com/apache/logging-log4j2/pull/608
https://github.com/tangxiaofeng7/apache-log4j-poc
https://logging.apache.org/log4j/2.x/changes-report.html#a2.15.0
https://logging.apache.org/log4j/2.x/manual/lookups.html#JndiLookup
https://github.com/advisories/GHSA-jfh8-c2jp-5v3q