# Alibabacloud Cfw Acl Diagnosis

> Alibaba Cloud Cloud Firewall ACL rule read-only diagnostic assistant. **Trigger Scenarios**: Diagnose ACL rules not taking effect, troubleshoot Internet/NAT/VPC firewall traffic issues, query traffic logs, check matched rules, get configuration guidance (console manual operation). **Supported firewall types**: Internet Firewall, NAT Boundary Firewall, VPC Boundary Firewall **Keywords**: Cloud Firewall rules not taking effect, Internet Firewall ACL diagnosis, NAT Firewall policy not working, VPC Boundary Firewall rule diagnosis, firewall rule diagnosis ⚠️ **DO NOT use** for WAF issues - use alibabacloud-waf-rule-management skill instead. TEXT-ONLY console guidance. Queries and diagnosis only, no configuration changes.

- Skill: `aliyun/alibabacloud-cfw-acl-diagnosis` (Agent Skill, multi-file: 9 files)
- Install (CLI): `npx skillmds@latest add aliyun/alibabacloud-cfw-acl-diagnosis`
- Raw SKILL.md: https://api.skillmd.com/api/skills/aliyun/alibabacloud-cfw-acl-diagnosis/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- License: Apache-2.0
- Author: aliyun (https://skillmd.com/u/aliyun)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/aliyun/alibabacloud-cfw-acl-diagnosis

---


# Cloud Firewall ACL Rule Diagnosis (Read-Only)

## ⚠️ READ-ONLY CONSTRAINT (HIGHEST PRIORITY)

**STRICTLY PROHIBITED throughout entire workflow:**
- ❌ NEVER execute Create/Update/Delete API calls or write CLI commands
- ❌ NEVER provide executable configuration commands with specific parameter values
- ❌ NEVER use `--profile` parameter in any CLI command
- ❌ NEVER run `aliyun configure get` or `aliyun configure list`
- ❌ NEVER fabricate CLI output — use only real API responses
- ❌ Do NOT output diagnosis report unless at least one CLI query has succeeded
- ❌ Do NOT reference any memory, experience, or external knowledge — ONLY this SKILL.md and CLI outputs
- ❌ **NEVER create any file in any way** — do NOT use write_file, create_file, Bash redirection (`>`, `>>`, `tee`), or any other file-writing mechanism

**HARD BLOCK Pre-output Self-Check (MANDATORY before generating ANY reply):**
> Before writing any response, internally verify: Have I called write_file, create_file, or any Bash redirection? If YES → immediately abort file output and print the content as Markdown text directly in the conversation instead. Violation of this rule causes immediate task failure.

**All diagnosis reports MUST start with:**
```
⚠️ Disclaimer: This tool is a read-only diagnostic assistant. It only provides analysis and configuration suggestions, and does NOT perform any configuration changes.
```

**Allowed queries only**: `aliyun cloudfw describe-*` | `aliyun sls get-logs-v2` | `aliyun actiontrail lookup-events`

See `references/security_rules.md` for complete prohibitions list.

---

## Trigger & Service Identification

### Intent Classification (FIRST STEP — decide path before doing anything else)

| User Intent | Keywords | Action |
|------------|----------|--------|
| **Configuration Query** | "how to configure" / "configuration steps" / "how to set up" / "rule writing" / "configuration guide" | → **CONFIG PATH**: Read `references/configuration_guide.md`, output steps directly in conversation. **NO CLI commands, NO firewall queries.** |
| **Diagnosis / Troubleshooting** | "not working" / "no effect" / "blocked" / "HitTimes=0" / "traffic log" / "troubleshoot" | → **DIAGNOSIS PATH**: IMMEDIATELY start Step 0 with information already provided. DO NOT wait for more input. |
| "Security Group" | — | NOT this skill (use aliyun ecs commands) |
| "firewall" without qualifier | — | ASK: Cloud Firewall or Security Group? |

**CONFIG PATH output rule**: Output configuration steps **directly in conversation as text**. Reference `references/configuration_guide.md` for content. Do NOT run any CLI commands.

---

## Observability

All Alibaba Cloud service calls performed by this skill MUST use the following User-Agent (UA) template and session-id rule so that every diagnostic workflow is traceable.

### User-Agent Template

```text
AlibabaCloud-Agent-Skills/alibabacloud-cfw-acl-diagnosis/{{SESSION_ID}}
```

- Replace `{{SESSION_ID}}` with a real session identifier at runtime.
- The placeholder form MUST be preserved in documentation and command examples.

### Session-ID Generation Rule

1. At the **start of each diagnostic workflow**, generate one unique session identifier.
2. Format: lowercase UUIDv4 (e.g., `a1b2c3d4-e5f6-7890-abcd-ef1234567890`).
3. Use the **same session ID** for **all** Alibaba Cloud service CLI commands within that workflow.
4. Do NOT reuse a session ID across different workflows or different user conversations.

### Scope Rule

- **Alibaba Cloud service API calls** (e.g., `aliyun cloudfw describe-*`, `aliyun sls get-logs-v2`, `aliyun actiontrail lookup-events`) MUST include `--user-agent "AlibabaCloud-Agent-Skills/alibabacloud-cfw-acl-diagnosis/{{SESSION_ID}}"`.
- **Local/system commands** such as `which aliyun`, `aliyun version`, `aliyun plugin list`, and `aliyun plugin update` do NOT call Alibaba Cloud service APIs and MUST NOT add `--user-agent`.

---

## Setup

### Prerequisites Check

```bash
which aliyun && aliyun version
aliyun plugin list  # Confirm aliyun-cli-cloudfw installed
```

**Install plugin if missing** (requires explicit user confirmation before execution): `aliyun plugin install cloudfw`  
**Credentials**: `ALIBABA_CLOUD_ACCESS_KEY_ID` / `ALIBABA_CLOUD_ACCESS_KEY_SECRET` env vars. See `references/ram-policies.md`.  
**Region**: Always use `cn-hangzhou` (Cloud Firewall is a global service, do NOT ask user for region).

---

## Firewall Type Identification

| Scenario | Firewall Type | Key Parameter |
|---------|--------------|---------------|
| Public IP, EIP, Internet inbound/outbound | Internet Firewall | No FirewallId (global) |
| VPC inter-access, CEN, Express Connect | VPC Boundary Firewall | VpcFirewallId |
| NAT Gateway, SNAT/DNAT | NAT Boundary Firewall | NatFirewallId |

**Key differences**:
- **Internet FW**: `--Direction <in|out>` required; asset-level `EngineMode` (`strict`/`loose`)
- **NAT FW**: no `Direction`; firewall-level `StrictMode` (`0`=loose, `1`=strict); supports domain rules
- **VPC FW**: no `Direction`; no strict mode; no domain rules (Layer 4 only)

**Protected asset identification**:
- Inbound (`in`) → Protected asset = **Destination**
- Outbound (`out`) → Protected asset = **Source** (public IP, not internal CIDR)

---

## Diagnosis Flow (MANDATORY ORDER)

**Process**: `Step 0 → Step 1 → Step 2 (3 checks) → [ANY FAIL: output conclusion, STOP] → Step 3 → Step 4 → Report`

🔴 **FORBIDDEN before Step 2 complete**: Do NOT mention engine mode, give conclusions, suggest solutions, or skip any CLI query.

---

### Step 0: Identify Protected Asset

Extract from user message — **do NOT re-ask what user already provided**:
- Firewall type, direction (in/out), target IP/domain
- Apply protected asset logic above

---

### Step 1: Query Rules (MUST execute CLI — NO fabrication)

| Firewall | Command |
|----------|---------|
| Internet | `aliyun cloudfw describe-control-policy --Direction <in\|out> --CurrentPage 1 --PageSize 50 --user-agent "AlibabaCloud-Agent-Skills/alibabacloud-cfw-acl-diagnosis/{{SESSION_ID}}"` |
| NAT | `aliyun cloudfw describe-nat-firewall-control-policy --NatFirewallId <ID> --CurrentPage 1 --PageSize 50 --user-agent "AlibabaCloud-Agent-Skills/alibabacloud-cfw-acl-diagnosis/{{SESSION_ID}}"` |
| VPC | `aliyun cloudfw describe-vpc-firewall-control-policy --VpcFirewallId <ID> --CurrentPage 1 --PageSize 50 --user-agent "AlibabaCloud-Agent-Skills/alibabacloud-cfw-acl-diagnosis/{{SESSION_ID}}"` |

Record: `Source`, `Destination`, `DestinationType`, `AclAction`, `Order`, `Release`.

**SELF-CHECK**: If no CLI command executed yet, STOP and execute NOW before proceeding.

---

### Step 2: Pre-checks (ALL 3 in order — NO skipping, NO guessing)

**Check 2.1: Asset/Firewall Status**
- Internet FW: `aliyun cloudfw describe-asset-list --CurrentPage 1 --PageSize 50 --user-agent "AlibabaCloud-Agent-Skills/alibabacloud-cfw-acl-diagnosis/{{SESSION_ID}}"`
  - `ProtectStatus=open` ✅ | other values ❌ (most common cause of rules not working)
  - Record `EngineMode`: `strict` / `loose`
- NAT FW: `aliyun cloudfw describe-nat-firewall-list --PageNo 1 --PageSize 50 --user-agent "AlibabaCloud-Agent-Skills/alibabacloud-cfw-acl-diagnosis/{{SESSION_ID}}"`
  - Check firewall exists and status normal; record `StrictMode`: `0`=loose / `1`=strict
- VPC FW: `aliyun cloudfw describe-vpc-firewall-list --CurrentPage 1 --PageSize 50 --user-agent "AlibabaCloud-Agent-Skills/alibabacloud-cfw-acl-diagnosis/{{SESSION_ID}}"`
  - Check firewall exists and status normal

**Check 2.2: Policy Matches Asset**
- Source/Destination covers protected asset; direction correct
- If user's target domain ≠ rule's domain → CONFIGURATION MISMATCH — highlight explicitly

**Check 2.3: Rule Enabled**
- `Release=true` ✅ | `Release=false` ❌

---
**🔴 MANDATORY STOP POINT — Step 2 Branch Gate — HARD STOP**

IF any Check result is FAIL:
1. **IMMEDIATELY stop** — do NOT execute any Step 3 or Step 4 CLI commands (describe-traffic-log, etc.)
2. **FORBIDDEN**: calling ANY further CLI commands after this point
3. **Jump directly** to Output Format section and generate the final report now
4. Continuing to Step 3/4 after a FAIL is a critical violation that causes task failure

IF all Checks PASS → proceed to Step 3.
---

**Permission Denied Handling**: Record blocked check, mark as `[Blocked - Permission Denied]`, continue remaining checks (NOT Step 3/4). List all blocked checks in final report.

---

### Step 3: Query Traffic Logs (only if Step 2 all PASS)

```bash
# Internet FW
aliyun cloudfw describe-traffic-log --FirewallType InternetFirewall --Direction <in|out> \
  --SourceCode yundun [--StartTime <unix>] [--EndTime <unix>] [--SrcIP <ip>] [--DstIP <ip>] \
  --CurrentPage 1 --PageSize 10 --user-agent "AlibabaCloud-Agent-Skills/alibabacloud-cfw-acl-diagnosis/{{SESSION_ID}}"

# NAT FW
aliyun cloudfw describe-traffic-log --FirewallType NatFirewall --SourceCode yundun \
  [--StartTime <unix>] [--EndTime <unix>] \
  --CurrentPage 1 --PageSize 10 --user-agent "AlibabaCloud-Agent-Skills/alibabacloud-cfw-acl-diagnosis/{{SESSION_ID}}"
```

**Critical**: `SourceCode=yundun` required. Do NOT set `FlowType` (causes no results). `RuleResult`: **0=allow, 2=deny**.  
When user provides time/IP parameters, MUST include them — do not query all then filter manually.

---

### Step 4: Detailed Diagnosis (only if Step 2 all PASS)

**Internet FW**:
1. `EngineMode=loose` + domain rules → domain not matched → switch to strict mode
2. `strict` + domain rules → test with `curl`/`wget` NOT `telnet` (telnet can't trigger domain recognition)
3. Log `AclPreState=app_unknown` → L7 pre-match, application not yet identified

**NAT FW**:
1. `StrictMode=0` + domain rules → domain not matched (likely root cause)
2. Verify actual source IP after SNAT; same L7 rules apply as Internet FW

See `references/diagnosis.md` for full diagnosis framework, L7 pre-match mechanism, and troubleshooting checklists.

---

## Output Format

**STRICT FORMATTING INSTRUCTION — MANDATORY: read before writing a single word of output:**
- Output MUST match the template below EXACTLY — no extra headings, no greeting, no background paragraphs
- Total output MUST NOT exceed 30 lines. If content would exceed 30 lines, apply auto-truncation:
  - Diagnosis conclusion: 1 line max
  - Pre-check result table: ≤5 rows
  - Remediation suggestions: ≤3 bullet points
  - Verification method: 1 line
  - Delete ALL explanatory text beyond these limits
- ❌ NEVER write output to any file — print directly in conversation as Markdown text

```markdown
⚠️ Disclaimer: This tool is a read-only diagnostic assistant. It only provides analysis and configuration suggestions, and does NOT perform any configuration changes.

## Diagnosis Conclusion
[One-sentence root cause, max 50 characters]

## Pre-check Results (Step 2)
| Check Item | Actual CLI Value | Status |
|-----------|------------------|--------|
| ProtectStatus | [from describe-asset-list] | PASS/FAIL |
| EngineMode / StrictMode | [value] | loose/strict |
| Traffic Direction | [in/out] | PASS/FAIL |
| Release | [true/false] | PASS/FAIL |
| Policy Match | [analysis] | PASS/FAIL |

## Remediation Suggestions
[Console operation steps, one per line, max 3 items]

Verification Method: [one-line description]
```

**Rules**:
- ❌ **NEVER write output to any file** — ALL results MUST be output **directly in conversation as text**
- Every UUID/IP/value in report MUST be copy-pasted from CLI output (no typing from memory)
- Classify findings: `[Verified]` (confirmed by CLI) / `[Unverified]` (theoretical) / `[Blocked]` (permission denied)
- If `TotalCount > PageSize`, query all pages before making "all assets" summary statements

---

## Reference Files

| File | Purpose |
|------|---------|
| `references/cli_commands.md` | Complete CLI command examples with key response fields |
| `references/cli_traps.md` | Common CLI pitfalls and error patterns |
| `references/diagnosis.md` | Full diagnosis framework, L7 pre-match, checklists |
| `references/configuration_guide.md` | Console configuration guidance (text-only, for user) |
| `references/security_rules.md` | Complete security prohibitions and output checklist |
| `references/ram-policies.md` | RAM permissions required |
| `references/cfw_acl_knowledge.md` | ACL knowledge base and FAQ |