IngyHere created LOG4J2-970:
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Summary: Bad Mapped Hostname Results in Errors
Key: LOG4J2-970
URL: https://issues.apache.org/jira/browse/LOG4J2-970
Project: Log4j 2
Issue Type: Bug
Components: Core, Pattern Converters
Affects Versions: 2.1
Reporter: IngyHere
Log4J returns errors while parsing PatternLayout in certain situations where
${map:hostName} is substituted into the pattern. This occurred on a dual-homed
Linux System with an IPv4/IPv6 dual stack. When running Java 7u60 with Log4J2
v2.1 I received errors when the hostname call reported back an IPv6
transitional address with "%3" appended to the end. Log4J2 then reported errors
when it tried to parse the resulting pattern after substituting the property.
Explanation: The underlying Java API that retrieves hostname values uses the
InetAddress class via InetAddress.getLocalHost().getHostName(). Returning a
single hostname on a multihomed system is inexact and uses one of several Java
API internal mechanisms that vary. If the returned value contains special
characters also used to format logging patterns, it can cause an unrecognized
format specifier error.
Detail: See
https://git-wip-us.apache.org/repos/asf?p=logging-log4j2.git;a=blob;f=log4j-core/src/main/java/org/apache/logging/log4j/core/util/NetUtils.java
on line 45 where it collects the information.
Proposed Fix: Scrub the hostName property (probably a few other properties,
too) of any protected or special symbols that are interpreted by Log4J to
output conversions. I'm also considering a situation where a hostname can be
illegally specified in a hosts file to contain conversions -- can this happen?
See logs.
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