[jira] [Commented] (LOG4J2-970) Bad Mapped Hostname Results in Errors

["IngyHere (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LOG4J2-970?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14346409#comment-14346409 ] 

IngyHere commented on LOG4J2-970:
---------------------------------

Log Snippet ... 

{code}
2015-02-01 14:18:52,793 DEBUG Calling build() on class class org.apache.logging.log4j.core.layout.PatternLayout$Builder for element PatternLayout with params(pattern="%d{ISO8601} MyFollyApplicationName dd61:0:0:0:b64a:76dd:df41:d5ef%3 [%-10.10t] %-5.5p %40.40c - %m%n", Configuration(AGoodConfigName), null, charset="UTF-8", alwaysWriteExceptions="null", noConsoleNoAnsi="null", header="null", footer="null")
2015-02-01 14:18:52,793 DEBUG PluginManager 'Converter' found 33 plugins
2015-02-01 14:18:52,801 ERROR Unrecognized format specifier []
2015-02-01 14:18:52,801 ERROR Empty conversion specifier starting at position 58 in conversion pattern.
2015-02-01 14:18:52,804 DEBUG Built Plugin[name=layout] OK from builder factory method.
{code}

Note the weirdly formed IPv6 address with the "%3" appended: "dd61:0:0:0:b64a:76dd:df41:d5ef%3". 

The actual pattern is ... 
{code}
 "%d{ISO8601} ${sys:anAppName} ${map:hostName} [%-10.10t] %-5.5p %40.40c - %m%n"
{code}

Also, FYI, this is being configured using a JSON file.

> 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 for whatever reason. 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. Note that there are several bugs reported against this API at Oracle, see http://bugs.java.com/bugdatabase/view_bug.do?bug_id=8044306 .
> 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? 
> NOTE: Log4J2 outputs errors about parsing the pattern but continues to parse the remainder of the pattern and appears to continue logging successfully. 
> See attached log snippets.



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