// 安全事件日志
public class SecurityLogger {
    public void logLoginAttempt(String username, boolean success, String ipAddress) {
        logger.info("Login attempt: user={}, success={}, ip={}, time={}",
            username, success, ipAddress, Instant.now());
    }
    
    public void logAccessDenied(String userId, String resource, String action) {
        logger.warn("Access denied: user={}, resource={}, action={}, time={}",
            userId, resource, action, Instant.now());
    }
    
    public void logSensitiveOperation(String userId, String operation, String details) {
        logger.info("Sensitive operation: user={}, op={}, details={}, time={}",
            userId, operation, details, Instant.now());
    }
}

// 危险！日志中记录敏感信息
logger.info("User login: username={}, password={}", username, password);    // 不要记录密码！

public class AuditTrail {
    public void record(AuditEvent event) {
        // 不可变的审计记录
        AuditRecord record = new AuditRecord(
            UUID.randomUUID(),
            event.getUserId(),
            event.getAction(),
            event.getResource(),
            event.getTimestamp(),
            event.getIpAddress(),
            event.getUserAgent(),
            computeHash(event)    // 完整性校验
        );
        
        // 写入审计日志（只追加，不可修改）
        auditRepository.append(record);
    }
    
    private String computeHash(AuditEvent event) {
        // 计算哈希确保记录不被篡改
        return DigestUtils.sha256Hex(event.toString() + secretKey);
    }
}

日志安全风险：
1. 日志注入：攻击者在输入中注入换行符伪造日志
   → 对策：转义日志输入

2. 敏感信息泄露：日志中记录密码、信用卡号等
   → 对策：过滤敏感字段

3. 日志篡改：攻击者修改日志掩盖痕迹
   → 对策：只追加存储、哈希校验

4. 日志洪泛：大量假日志淹没真实事件
   → 对策：限流、异常检测

public class SecureLogger {
    private static final Set<String> SENSITIVE_FIELDS = Set.of(
        "password", "ssn", "creditCard", "token", "secret"
    );
    
    public void log(String template, Object... args) {
        Object[] safeArgs = Arrays.stream(args)
            .map(this::sanitize)
            .toArray();
        logger.info(template, safeArgs);
    }
    
    private Object sanitize(Object arg) {
        if (arg instanceof Map) {
            Map<?, ?> map = (Map<?, ?>) arg;
            Map<Object, Object> sanitized = new HashMap<>();
            for (Map.Entry<?, ?> entry : map.entrySet()) {
                String key = String.valueOf(entry.getKey());
                if (SENSITIVE_FIELDS.contains(key.toLowerCase())) {
                    sanitized.put(entry.getKey(), "***REDACTED***");
                } else {
                    sanitized.put(entry.getKey(), entry.getValue());
                }
            }
            return sanitized;
        }
        return arg;
    }
}