uk.gov.dwp.logging.LogEntryBuilderFactory Maven / Gradle / Ivy

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Wrapper class to sanitise log output and mitigate possible log forging
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package uk.gov.dwp.logging;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;

import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.time.Instant;
import java.time.format.DateTimeFormatter;

public class LogEntryBuilderFactory {

    private static final String UNKNOWN = "";
    private static final String APP_NAME = "app_name";
    private static final String APP_VERSION = "app_version";
    private static final String HOST_NAME = "hostname";
    private static final String PID = "pid";
    private static final String TIMESTAMP = "ts";
    private static final String MESSAGE = "message";
    private static final String LEVEL = "level";
    private static final String NAME_SPACE = "ns";
    private static final String META = "meta";

    private static final DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ISO_INSTANT;

    private final ObjectMapper mapper;
    private final Sanitiser sanitiser;

    private final String processId;
    private final String appName;
    private final String appVersion;
    private final String hostname;

    public LogEntryBuilderFactory(String appName, String appVersion) {
        this.processId = getPID();
        this.appName = appName;
        this.appVersion = appVersion;
        String localHostName;
        try {
            localHostName = InetAddress.getLocalHost().getHostName();
        } catch (UnknownHostException ex) {
            localHostName = UNKNOWN;
        }
        this.hostname = localHostName;
        
        mapper = new ObjectMapper();

        sanitiser = new Sanitiser();
    }

    public LogEntryBuilder getBuilder() {
        return new LogEntryBuilder()
                .withAppName(appName)
                .withAppVersion(appVersion)
                .withPid(processId);
    }
    

    private static String getPID() {
        String vmName = ManagementFactory.getRuntimeMXBean().getName();
        int p = vmName.indexOf('@');
        return vmName.substring(0, p);
    }

    public class LogEntryBuilder {

        private final ObjectNode eventNode;
        private final ObjectNode metaNode;

        public LogEntryBuilder() {
            this.eventNode = mapper.createObjectNode();
            this.eventNode.put(APP_NAME, UNKNOWN);
            this.eventNode.put(APP_VERSION, UNKNOWN);
            this.eventNode.put(HOST_NAME, hostname);
            this.eventNode.put(PID, processId);
            this.eventNode.put(TIMESTAMP, dateTimeFormatter.format(Instant.now()));
            this.eventNode.put(MESSAGE, UNKNOWN);
            this.eventNode.put(LEVEL, UNKNOWN);
            this.eventNode.put(NAME_SPACE, UNKNOWN);

            this.metaNode = eventNode.putObject(META);

        }

        private void addToNode(String key, String val) {
            eventNode.put(key.toLowerCase(), val);
        }

        private void addToMeta(String key, String val) {
            metaNode.put(key.toLowerCase(), val);
        }

        public LogEntryBuilder withAppName(String appName) {
            addToNode(APP_NAME, appName);
            return this;
        }

        public LogEntryBuilder withAppVersion(String appVersion) {
            addToNode(APP_VERSION, appVersion);
            return this;
        }

        public LogEntryBuilder withPid(String pid) {
            addToNode(PID, pid);
            return this;
        }

        public LogEntryBuilder withMessage(String message) {
            addToNode(MESSAGE, sanitiser.sanitise(message));
            return this;
        }

        public LogEntryBuilder withLevel(String level) {
            addToNode(LEVEL, level);
            return this;
        }

        public LogEntryBuilder withNameSpace(String namespace) {
            addToNode(NAME_SPACE, namespace);
            return this;
        }
        
        public LogEntryBuilder withTimeStamp(long timestamp) {
            addToNode(TIMESTAMP, dateTimeFormatter.format(Instant.ofEpochMilli(timestamp)));
            return this;
        }

        public LogEntryBuilder withTimeStamp(Instant timestamp) {
            addToNode(TIMESTAMP, dateTimeFormatter.format(timestamp));
            return this;
        }
        
        public LogEntryBuilder withMeta(String key, String value) {
            addToMeta(key, sanitiser.sanitise(value));
            return this;
        }

        public String build() {
            try {
                return mapper.writeValueAsString(eventNode) + "\n";
            } catch (JsonProcessingException ex) {
                return ex.getMessage();
            }
        }

    }

}