analyzing-docker-container-forensics

分析 Docker 容器取证

何时使用

• 在调查受入侵的 Docker 容器或容器主机时
• 分析从镜像仓库拉取的恶意 Docker 镜像时
• 在涉及容器化应用入侵的事件响应过程中
• 检查容器逃逸尝试或权限提升时
• 审计容器配置并识别错误配置时

前置条件

• 在取证工作站上具备 Docker CLI 访问权限
• 可访问 Docker 主机文件系统（取证镜像或实时系统）
• 了解 Docker 分层文件系统（overlay2、aufs）
• 使用 dive、docker-explorer 或 container-diff 进行镜像分析
• 了解 Docker 守护进程配置和套接字安全
• 使用 Trivy 或 Grype 对容器镜像进行漏洞扫描

工作流

步骤 1：保存容器状态与证据

# List all containers (including stopped)
docker ps -a --no-trunc > /cases/case-2024-001/docker/container_list.txt

# Inspect the compromised container
CONTAINER_ID="abc123def456"
docker inspect $CONTAINER_ID > /cases/case-2024-001/docker/container_inspect.json

# Export container filesystem as tarball (preserves current state)
docker export $CONTAINER_ID > /cases/case-2024-001/docker/container_export.tar

# Create an image from the container's current state
docker commit $CONTAINER_ID forensic-evidence:case-2024-001
docker save forensic-evidence:case-2024-001 > /cases/case-2024-001/docker/container_image.tar

# Capture container logs
docker logs $CONTAINER_ID --timestamps > /cases/case-2024-001/docker/container_logs.txt 2>&1

# Capture running processes (if container is still running)
docker top $CONTAINER_ID > /cases/case-2024-001/docker/container_processes.txt

# Capture network connections
docker exec $CONTAINER_ID netstat -tlnp 2>/dev/null > /cases/case-2024-001/docker/container_network.txt

# Copy specific files from the container
docker cp $CONTAINER_ID:/var/log/ /cases/case-2024-001/docker/container_var_log/
docker cp $CONTAINER_ID:/tmp/ /cases/case-2024-001/docker/container_tmp/
docker cp $CONTAINER_ID:/etc/passwd /cases/case-2024-001/docker/container_passwd

# Hash all exported evidence
sha256sum /cases/case-2024-001/docker/*.tar > /cases/case-2024-001/docker/evidence_hashes.txt

步骤 2：分析容器镜像层

# Install dive for image layer analysis
wget https://github.com/wagoodman/dive/releases/latest/download/dive_linux_amd64.deb
sudo dpkg -i dive_linux_amd64.deb

# Analyze image layers interactively
dive forensic-evidence:case-2024-001

# Non-interactive layer analysis
dive forensic-evidence:case-2024-001 --ci --json /cases/case-2024-001/docker/dive_analysis.json

# Extract and examine individual layers
mkdir -p /cases/case-2024-001/docker/layers/
tar -xf /cases/case-2024-001/docker/container_image.tar -C /cases/case-2024-001/docker/layers/

# List the image manifest and layer order
cat /cases/case-2024-001/docker/layers/manifest.json | python3 -m json.tool

# Examine each layer for changes
for layer in /cases/case-2024-001/docker/layers/*/layer.tar; do
    echo "=== Layer: $(dirname $layer | xargs basename) ==="
    tar -tf "$layer" | head -20
    echo "..."
done

# Use container-diff to compare with original base image
# Install container-diff
curl -LO https://storage.googleapis.com/container-diff/latest/container-diff-linux-amd64
chmod +x container-diff-linux-amd64

# Compare committed image with original
./container-diff-linux-amd64 diff daemon://nginx:latest daemon://forensic-evidence:case-2024-001 \
   --type=file --type=apt --type=history --json \
   > /cases/case-2024-001/docker/container_diff.json

步骤 3：检查 Docker 主机工件

# Docker data directory (default: /var/lib/docker/)
DOCKER_ROOT="/mnt/evidence/var/lib/docker"

# Examine overlay2 filesystem layers
ls -la $DOCKER_ROOT/overlay2/

# Find the container's merged filesystem
CONTAINER_HASH=$(docker inspect $CONTAINER_ID --format '{{.GraphDriver.Data.MergedDir}}' 2>/dev/null)
# Or manually from forensic image:
# Look in /var/lib/docker/containers/<container_id>/config.v2.json

# Analyze container configuration files
cat $DOCKER_ROOT/containers/$CONTAINER_ID/config.v2.json | python3 -m json.tool \
   > /cases/case-2024-001/docker/container_config.json

# Check Docker daemon configuration
cat /mnt/evidence/etc/docker/daemon.json 2>/dev/null > /cases/case-2024-001/docker/daemon_config.json

# Examine Docker events log
cat $DOCKER_ROOT/containers/$CONTAINER_ID/*.log > /cases/case-2024-001/docker/container_json_logs.txt

# Check for volume mounts (potential host filesystem access)
python3 << 'PYEOF'
import json

with open('/cases/case-2024-001/docker/container_inspect.json') as f:
    data = json.load(f)

inspect = data[0] if isinstance(data, list) else data

print("=== CONTAINER SECURITY ANALYSIS ===\n")

# Check mounts
print("Volume Mounts:")
for mount in inspect.get('Mounts', []):
    rw = "READ-WRITE" if mount.get('RW') else "READ-ONLY"
    print(f"  {mount.get('Source', 'N/A')} -> {mount.get('Destination', 'N/A')} ({rw})")
    if mount.get('Source') in ('/', '/etc', '/var', '/root') and mount.get('RW'):
        print(f"    WARNING: Sensitive host path mounted read-write!")

# Check privileged mode
host_config = inspect.get('HostConfig', {})
if host_config.get('Privileged'):
    print("\nWARNING: Container was running in PRIVILEGED mode!")

# Check capabilities
cap_add = host_config.get('CapAdd', [])
if cap_add:
    print(f"\nAdded Capabilities: {cap_add}")
    dangerous_caps = ['SYS_ADMIN', 'SYS_PTRACE', 'NET_ADMIN', 'SYS_MODULE']
    for cap in cap_add:
        if cap in dangerous_caps:
            print(f"  WARNING: Dangerous capability: {cap}")

# Check PID namespace
if host_config.get('PidMode') == 'host':
    print("\nWARNING: Container shares host PID namespace!")

# Check network mode
if host_config.get('NetworkMode') == 'host':
    print("\nWARNING: Container shares host network namespace!")

# Check user
user = inspect.get('Config', {}).get('User', 'root (default)')
print(f"\nRunning as user: {user}")

# Check environment variables for secrets
env_vars = inspect.get('Config', {}).get('Env', [])
print(f"\nEnvironment Variables: {len(env_vars)}")
for env in env_vars:
    key = env.split('=')[0]
    if any(s in key.upper() for s in ['PASSWORD', 'SECRET', 'KEY', 'TOKEN', 'CREDENTIAL']):
        print(f"  SENSITIVE: {key}=***REDACTED***")
PYEOF

步骤 4：分析容器文件系统变更

# Compare container filesystem to original image
docker diff $CONTAINER_ID > /cases/case-2024-001/docker/filesystem_changes.txt

# A = Added, C = Changed, D = Deleted
# Analyze changes
python3 << 'PYEOF'
added = []
changed = []
deleted = []

with open('/cases/case-2024-001/docker/filesystem_changes.txt') as f:
    for line in f:
        line = line.strip()
        if line.startswith('A '):
            added.append(line[2:])
        elif line.startswith('C '):
            changed.append(line[2:])
        elif line.startswith('D '):
            deleted.append(line[2:])

print(f"Files Added: {len(added)}")
print(f"Files Changed: {len(changed)}")
print(f"Files Deleted: {len(deleted)}")

# Flag suspicious additions
suspicious = [f for f in added if any(s in f for s in
    ['/tmp/', '/dev/shm/', '/root/', '.sh', '.py', '.elf', 'reverse', 'shell', 'backdoor'])]
if suspicious:
    print(f"\nSuspicious Added Files:")
    for f in suspicious:
        print(f"  {f}")

# Flag suspicious changes
sus_changed = [f for f in changed if any(s in f for s in
    ['/etc/passwd', '/etc/shadow', '/etc/crontab', '/etc/ssh', '.bashrc'])]
if sus_changed:
    print(f"\nSuspicious Changed Files:")
    for f in sus_changed:
        print(f"  {f}")
PYEOF

# Extract and examine the container export
mkdir -p /cases/case-2024-001/docker/container_fs/
tar -xf /cases/case-2024-001/docker/container_export.tar -C /cases/case-2024-001/docker/container_fs/

# Scan for webshells and malicious files
find /cases/case-2024-001/docker/container_fs/tmp/ -type f -exec file {} \;
find /cases/case-2024-001/docker/container_fs/ -name "*.php" -newer /cases/case-2024-001/docker/container_fs/etc/hostname

步骤 5：扫描漏洞并生成报告

# Scan the image for known vulnerabilities
trivy image forensic-evidence:case-2024-001 \
   --format json \
   --output /cases/case-2024-001/docker/vulnerability_scan.json

# Scan the exported filesystem
trivy fs /cases/case-2024-001/docker/container_fs/ \
   --format table \
   --output /cases/case-2024-001/docker/fs_vulnerabilities.txt

# Check for secrets in the image
trivy image forensic-evidence:case-2024-001 \
   --scanners secret \
   --format json \
   --output /cases/case-2024-001/docker/secrets_scan.json

关键概念

概念	描述
镜像层	叠加构成容器镜像的只读文件系统层
overlay2	默认的 Docker 存储驱动，使用联合文件系统实现分层
容器差异	将运行时文件系统变更与原始镜像进行对比
特权模式	拥有完整主机能力的容器（绕过大多数隔离机制）
Docker 套接字	控制 Docker 守护进程的 Unix 套接字（/var/run/docker.sock）
容器逃逸	突破容器隔离进入主机的技术
卷挂载	使主机文件系统路径可在容器内访问
镜像历史	用于构建每个层的 Dockerfile 指令记录

工具与系统

工具	用途
docker inspect	详细的容器配置和状态信息
docker diff	显示运行中/已停止容器所做的文件系统变更
dive	交互式 Docker 镜像层分析工具
container-diff	用于比较容器镜像内容的 Google 工具
Trivy	针对容器镜像和文件系统的漏洞扫描器
docker-explorer	用于离线 Docker 工件分析的取证工具
Sysdig	容器运行时安全监控与取证
Falco	针对容器和 Kubernetes 的运行时威胁检测

常见场景

场景 1：Web 应用容器被入侵 导出容器文件系统，识别 Web 根目录中的 webshell，分析访问日志以查找利用尝试，检查新增文件和修改的配置，检查网络连接以发现 C2 通信，审查容器能力以寻找提权路径。

场景 2：通过恶意镜像发起的供应链攻击 使用 dive 分析镜像层以确定哪个层添加了恶意内容，使用 container-diff 与官方基础镜像进行比较，检查镜像历史中可疑的 RUN 命令，扫描嵌入的后门和加密货币挖矿程序，从镜像仓库日志追踪镜像拉取记录。

场景 3：容器逃逸调查 检查容器是否以特权模式运行或具有危险能力，检查主机文件系统挂载点是否存在未授权访问，审查启用 Docker-in-Docker 滥用的 Docker 套接字挂载，分析主机系统日志以寻找容器逃逸迹象，检查内核漏洞利用工件。

场景 4：容器环境中的挖矿劫持 识别高 CPU 占用的容器，导出并分析容器镜像以查找挖矿二进制文件，检查镜像仓库中是否存在未授权镜像，审查容器创建事件以发现恶意部署，检查网络连接以发现矿池通信。

输出格式

Docker Container Forensics Summary:
  Container: abc123def456 (nginx-app)
  Image: company/web-app:v2.1
  Status: Running (started 2024-01-10 09:00 UTC)
  Host: docker-host-01.corp.local

  Security Configuration:
    Privileged: No
    Capabilities Added: NET_ADMIN (WARNING)
    Volume Mounts: /var/log -> /host-logs (RW)
    Network Mode: bridge
    User: root (WARNING)

  Filesystem Changes:
    Added: 23 files (5 suspicious)
    Changed: 12 files (2 suspicious)
    Deleted: 0 files

  Suspicious Findings:
    /tmp/reverse.sh - Reverse shell script (Added)
    /var/www/html/.hidden/shell.php - PHP webshell (Added)
    /etc/crontab - Modified (persistence cron entry added)
    /root/.ssh/authorized_keys - Modified (unauthorized key added)

  Vulnerability Scan:
    Critical: 3 (CVE-2024-xxxx in base image)
    High: 12
    Medium: 34

  Evidence: /cases/case-2024-001/docker/