docker-minecraft-server/scripts/start-finalExec-log4j

#!/bin/bash

useGeneratedLogs=${GENERATE_LOG4J2_CONFIG:-${ENABLE_ROLLING_LOGS:-false}}
useFallbackJvmFlag=false

patchLog4jConfig() {
  file=${1?}
  url=${2?}
  if ! get -o "${SERVER_DIR}/${file}" "$url"; then
    logError "Failed to download corrected log4j config, fallback to JVM flag"
    useFallbackJvmFlag=true
    return 1
  fi
  JVM_OPTS="-Dlog4j.configurationFile=${file} ${JVM_OPTS}"
  useGeneratedLogs=false
}

# Temporarily disable debugging output
oldState=$(shopt -po xtrace || true)
shopt -u -o xtrace
# Patch Log4j remote code execution vulnerability
# See https://www.minecraft.net/en-us/article/important-message--security-vulnerability-java-edition
if isFamily NATIVE; then
  : # Native server, so there is no log4j to patch
elif versionLessThan 1.7; then
  : # No patch required here.
elif isFamily VANILLA && versionLessThan 1.12; then
  patchLog4jConfig log4j2_17-111.xml https://launcher.mojang.com/v1/objects/dd2b723346a8dcd48e7f4d245f6bf09e98db9696/log4j2_17-111.xml
elif isFamily VANILLA && versionLessThan 1.17; then
  patchLog4jConfig log4j2_112-116.xml https://launcher.mojang.com/v1/objects/02937d122c86ce73319ef9975b58896fc1b491d1/log4j2_112-116.xml
# See https://purpurmc.org/docs/Log4j/
elif isType PURPUR && versionLessThan 1.17; then
  patchLog4jConfig purpur_log4j2_1141-1165.xml https://purpurmc.org/docs/xml/purpur_log4j2_1141-1165.xml
elif isType PURPUR && versionLessThan 1.18.1; then
  patchLog4jConfig purpur_log4j2_117.xml https://purpurmc.org/docs/xml/purpur_log4j2_117.xml
elif versionLessThan 1.18.1; then
  useFallbackJvmFlag=true
fi
eval "$oldState"

if ${useFallbackJvmFlag}; then
  JVM_OPTS="-Dlog4j2.formatMsgNoLookups=true ${JVM_OPTS}"
fi

if isFamily NATIVE; then
  : # Native server, so no Log4jPatcher agent
elif versionLessThan 1.7; then
  : # No patch required here.
elif versionLessThan 1.18.1; then
  if isTrue "${SKIP_LOG4J_PATCHER:-false}"; then
    log "Skipping Log4jPatcher, make sure you are not affected"
  else
    JVM_OPTS="-javaagent:/image/Log4jPatcher.jar ${JVM_OPTS}"
  fi
fi

# Set up log4j2 configuration with templating support
LOGFILE="${SERVER_DIR}/log4j2.xml"
if isFamily NATIVE; then
  : # Native server, so no log4j configuration
elif ${useGeneratedLogs}; then
  # Set up log configuration defaults
  : "${LOG_LEVEL:=info}"
  : "${ROLLING_LOG_MAX_FILES:=1000}"
  # Note: Can't use ${VAR:=default} syntax for values containing } as it breaks parsing
  if [ -z "${ROLLING_LOG_FILE_PATTERN}" ]; then
    ROLLING_LOG_FILE_PATTERN='logs/%d{yyyy-MM-dd}-%i.log.gz'
  fi

  # Pattern format defaults (compatible with vanilla Minecraft)
  # Note: Can't use ${VAR:=default} syntax because } in the value breaks parsing
  if [ -z "${LOG_CONSOLE_FORMAT}" ]; then
    LOG_CONSOLE_FORMAT='[%d{HH:mm:ss}] [%t/%level]: %msg%n'
  fi
  if [ -z "${LOG_TERMINAL_FORMAT}" ]; then
    LOG_TERMINAL_FORMAT='[%d{HH:mm:ss} %level]: %msg%n'
  fi
  if [ -z "${LOG_FILE_FORMAT}" ]; then
    LOG_FILE_FORMAT='[%d{HH:mm:ss}] [%t/%level]: %msg%n'
  fi

  export LOG_LEVEL ROLLING_LOG_FILE_PATTERN ROLLING_LOG_MAX_FILES
  export LOG_CONSOLE_FORMAT LOG_TERMINAL_FORMAT LOG_FILE_FORMAT


  # Always regenerate if file doesn't exist
  if [ ! -e "$LOGFILE" ] || isTrue "${REGENERATE_LOG4J2:-true}"; then
    log "Generating log4j2.xml from template in ${LOGFILE}"

    # Generate log4j2.xml using heredoc for reliable variable substitution
    cat > "$LOGFILE" <<EOF
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
    <Appenders>
        <Console name="SysOut" target="SYSTEM_OUT">
            <PatternLayout pattern="${LOG_CONSOLE_FORMAT}" />
        </Console>
        <Queue name="TerminalConsole">
            <PatternLayout pattern="${LOG_TERMINAL_FORMAT}" />
        </Queue>
        <RollingRandomAccessFile name="File" fileName="logs/latest.log" filePattern="${ROLLING_LOG_FILE_PATTERN}">
            <PatternLayout pattern="${LOG_FILE_FORMAT}" />
            <Policies>
                <TimeBasedTriggeringPolicy />
                <OnStartupTriggeringPolicy />
            </Policies>
            <DefaultRolloverStrategy max="${ROLLING_LOG_MAX_FILES}"/>
        </RollingRandomAccessFile>
    </Appenders>
    <Loggers>
        <Root level="${LOG_LEVEL}">
            <filters>
                <MarkerFilter marker="NETWORK_PACKETS" onMatch="DENY" onMismatch="NEUTRAL" />
            </filters>
            <AppenderRef ref="SysOut"/>
            <AppenderRef ref="File"/>
            <AppenderRef ref="TerminalConsole"/>
        </Root>
    </Loggers>
</Configuration>
EOF
  else
    log "log4j2.xml already exists and is up to date, skipping generation"
  fi

  # Apply the log4j2 configuration
  JVM_OPTS="-Dlog4j.configurationFile=log4j2.xml ${JVM_OPTS}"
else
  rm -f "${LOGFILE}"
fi