claude-skills-reference/docs/skills/engineering-team/cloud-security.md

title, description

title	description
Cloud Security — Agent Skill & Codex Plugin	Use when assessing cloud infrastructure for security misconfigurations, IAM privilege escalation paths, S3 public exposure, open security group. Agent skill for Claude Code, Codex CLI, Gemini CLI, OpenClaw.

Cloud Security

:material-code-braces: Engineering - Core :material-identifier: `cloud-security` :material-github: Source

Install: claude /plugin install engineering-skills

Cloud security posture assessment skill for detecting IAM privilege escalation, public storage exposure, network configuration risks, and infrastructure-as-code misconfigurations. This is NOT incident response for active cloud compromise (see incident-response) or application vulnerability scanning (see security-pen-testing) — this is about systematic cloud configuration analysis to prevent exploitation.

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Table of Contents

• Overview
• Cloud Posture Check Tool
• IAM Policy Analysis
• S3 Exposure Assessment
• Security Group Analysis
• IaC Security Review
• Cloud Provider Coverage Matrix
• Workflows
• Anti-Patterns
• Cross-References

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Overview

What This Skill Does

This skill provides the methodology and tooling for cloud security posture management (CSPM) — systematically checking cloud configurations for misconfigurations that create exploitable attack surface. It covers IAM privilege escalation paths, storage public exposure, network over-permissioning, and infrastructure code security.

Distinction from Other Security Skills

Skill	Focus	Approach
cloud-security (this)	Cloud configuration risk	Preventive — assess before exploitation
incident-response	Active cloud incidents	Reactive — triage confirmed cloud compromise
threat-detection	Behavioral anomalies	Proactive — hunt for attacker activity in cloud logs
security-pen-testing	Application vulnerabilities	Offensive — actively exploit found weaknesses

Prerequisites

Read access to IAM policy documents, S3 bucket configurations, and security group rules in JSON format. For continuous monitoring, integrate with cloud provider APIs (AWS Config, Azure Policy, GCP Security Command Center).

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Cloud Posture Check Tool

The cloud_posture_check.py tool runs three types of checks: iam (privilege escalation), s3 (public access), and sg (network exposure). It auto-detects the check type from the config file structure or accepts explicit --check flags.

# Analyze an IAM policy for privilege escalation paths
python3 scripts/cloud_posture_check.py policy.json --check iam --json

# Assess S3 bucket configuration for public access
python3 scripts/cloud_posture_check.py bucket_config.json --check s3 --json

# Check security group rules for open admin ports
python3 scripts/cloud_posture_check.py sg.json --check sg --json

# Run all checks with internet-facing severity bump
python3 scripts/cloud_posture_check.py config.json --check all \
  --provider aws --severity-modifier internet-facing --json

# Regulated data context (bumps severity by one level for all findings)
python3 scripts/cloud_posture_check.py config.json --check all \
  --severity-modifier regulated-data --json

# Pipe IAM policy from AWS CLI
aws iam get-policy-version --policy-arn arn:aws:iam::123456789012:policy/MyPolicy \
  --version-id v1 | jq '.PolicyVersion.Document' | \
  python3 scripts/cloud_posture_check.py - --check iam --json

Exit Codes

Code	Meaning	Required Action
0	No high/critical findings	No action required
1	High-severity findings	Remediate within 24 hours
2	Critical findings	Remediate immediately — escalate to incident-response if active

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IAM Policy Analysis

IAM analysis detects privilege escalation paths, overprivileged grants, public principal exposure, and data exfiltration risk.

Privilege Escalation Patterns

Pattern	Severity	Key Action Combination	MITRE
Lambda PassRole escalation	Critical	iam:PassRole + lambda:CreateFunction	T1078.004
EC2 instance profile abuse	Critical	iam:PassRole + ec2:RunInstances	T1078.004
CloudFormation PassRole	Critical	iam:PassRole + cloudformation:CreateStack	T1078.004
Self-attach policy escalation	Critical	iam:AttachUserPolicy + sts:GetCallerIdentity	T1484.001
Inline policy self-escalation	Critical	iam:PutUserPolicy + sts:GetCallerIdentity	T1484.001
Policy version backdoor	Critical	iam:CreatePolicyVersion + iam:ListPolicies	T1484.001
Credential harvesting	High	iam:CreateAccessKey + iam:ListUsers	T1098.001
Group membership escalation	High	iam:AddUserToGroup + iam:ListGroups	T1098
Password reset attack	High	iam:UpdateLoginProfile + iam:ListUsers	T1098
Service-level wildcard	High	iam:* or s3:* or ec2:*	T1078.004

IAM Finding Severity Guide

Finding Type	Condition	Severity
Full admin wildcard	Action=* Resource=*	Critical
Public principal	Principal: '*'	Critical
Dangerous action combo	Two-action escalation path	Critical
Individual priv-esc actions	On wildcard resource	High
Data exfiltration actions	s3:GetObject, secretsmanager:GetSecretValue on *	High
Service wildcard	service:* action	High
Data actions on named resource	Appropriate scope	Low/Clean

Least Privilege Recommendations

For every critical or high finding, the tool outputs a least_privilege_suggestion field with specific remediation guidance:

• Replace Action: * with a named list of required actions
• Replace Resource: * with specific ARN patterns
• Use AWS Access Analyzer to identify actually-used permissions
• Separate dangerous action combinations into different roles with distinct trust policies

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S3 Exposure Assessment

S3 assessment checks four dimensions: public access block configuration, bucket ACL, bucket policy principal exposure, and default encryption.

S3 Configuration Check Matrix

Check	Finding Condition	Severity
Public access block	Any of four flags missing/false	High
Bucket ACL	public-read-write	Critical
Bucket ACL	public-read or authenticated-read	High
Bucket policy Principal	"Principal": "*" with Allow	Critical
Default encryption	No ServerSideEncryptionConfiguration	High
Default encryption	Non-standard SSEAlgorithm	Medium
No PublicAccessBlockConfiguration	Status unknown	Medium

Recommended S3 Baseline Configuration

{
  "PublicAccessBlockConfiguration": {
    "BlockPublicAcls": true,
    "BlockPublicPolicy": true,
    "IgnorePublicAcls": true,
    "RestrictPublicBuckets": true
  },
  "ServerSideEncryptionConfiguration": {
    "Rules": [{
      "ApplyServerSideEncryptionByDefault": {
        "SSEAlgorithm": "aws:kms",
        "KMSMasterKeyID": "arn:aws:kms:region:account:key/key-id"
      },
      "BucketKeyEnabled": true
    }]
  },
  "ACL": "private"
}

All four public access block settings must be enabled at both the bucket level and the AWS account level. Account-level settings can be overridden by bucket-level settings if not both enforced.

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Security Group Analysis

Security group analysis flags inbound rules that expose admin ports, database ports, or all traffic to internet CIDRs (0.0.0.0/0, ::/0).

Critical Port Exposure Rules

Port	Service	Finding Severity	Remediation
22	SSH	Critical	Restrict to VPN CIDR or use AWS Systems Manager Session Manager
3389	RDP	Critical	Restrict to VPN CIDR or use AWS Fleet Manager
0–65535 (all)	All traffic	Critical	Remove rule; add specific required ports only

High-Risk Database Port Rules

Port	Service	Finding Severity	Remediation
1433	MSSQL	High	Allow from application tier SG only — move to private subnet
3306	MySQL	High	Allow from application tier SG only — move to private subnet
5432	PostgreSQL	High	Allow from application tier SG only — move to private subnet
27017	MongoDB	High	Allow from application tier SG only — move to private subnet
6379	Redis	High	Allow from application tier SG only — move to private subnet
9200	Elasticsearch	High	Allow from application tier SG only — move to private subnet

Severity Modifiers

Use --severity-modifier internet-facing when the assessed resource is directly internet-accessible (load balancer, API gateway, public EC2). Use --severity-modifier regulated-data when the resource handles PCI, HIPAA, or GDPR-regulated data. Both modifiers bump each finding's severity by one level.

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IaC Security Review

Infrastructure-as-code review catches configuration issues at definition time, before deployment.

IaC Check Matrix

Tool	Check Types	When to Run
Terraform	Resource-level checks (aws_s3_bucket_acl, aws_security_group, aws_iam_policy_document)	Pre-plan, pre-apply, PR gate
CloudFormation	Template property validation (PublicAccessBlockConfiguration, SecurityGroupIngress)	Template lint, deploy gate
Kubernetes manifests	Container privileges, network policies, secret exposure	PR gate, admission controller
Helm charts	Same as Kubernetes	PR gate

Terraform IAM Policy Example — Finding vs. Clean

# BAD: Will generate critical findings
resource "aws_iam_policy" "bad_policy" {
  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [{
      Effect   = "Allow"
      Action   = "*"
      Resource = "*"
    }]
  })
}

# GOOD: Least privilege
resource "aws_iam_policy" "good_policy" {
  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [{
      Effect   = "Allow"
      Action   = ["s3:GetObject", "s3:PutObject"]
      Resource = "arn:aws:s3:::my-specific-bucket/*"
    }]
  })
}

Full CSPM check reference: references/cspm-checks.md

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Cloud Provider Coverage Matrix

Check Type	AWS	Azure	GCP
IAM privilege escalation	Full (IAM policies, trust policies, ESCALATION_COMBOS)	Partial (RBAC assignments, service principal risks)	Partial (IAM bindings, workload identity)
Storage public access	Full (S3 bucket policies, ACLs, public access block)	Partial (Blob SAS tokens, container access levels)	Partial (GCS bucket IAM, uniform bucket-level access)
Network exposure	Full (Security Groups, NACLs, port-level analysis)	Partial (NSG rules, inbound port analysis)	Partial (Firewall rules, VPC firewall)
IaC scanning	Full (Terraform, CloudFormation)	Partial (ARM templates, Bicep)	Partial (Deployment Manager)

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Workflows

Workflow 1: Quick Posture Check (20 Minutes)

For a newly provisioned resource or pre-deployment review:

# 1. Export IAM policy document
aws iam get-policy-version --policy-arn ARN --version-id v1 | \
  jq '.PolicyVersion.Document' > policy.json
python3 scripts/cloud_posture_check.py policy.json --check iam --json

# 2. Check S3 bucket configuration
aws s3api get-bucket-acl --bucket my-bucket > acl.json
aws s3api get-public-access-block --bucket my-bucket >> bucket.json
python3 scripts/cloud_posture_check.py bucket.json --check s3 --json

# 3. Review security groups for open admin ports
aws ec2 describe-security-groups --group-ids sg-123456 | \
  jq '.SecurityGroups[0]' > sg.json
python3 scripts/cloud_posture_check.py sg.json --check sg --json

Decision: Exit code 2 = block deployment and remediate. Exit code 1 = schedule remediation within 24 hours.

Workflow 2: Full Cloud Security Assessment (Multi-Day)

Day 1 — IAM and Identity:

1. Export all IAM policies attached to production roles
2. Run cloud_posture_check.py --check iam on each policy
3. Map all privilege escalation paths found
4. Identify overprivileged service accounts and roles
5. Review cross-account trust policies

Day 2 — Storage and Network:

1. Enumerate all S3 buckets and export configurations
2. Run cloud_posture_check.py --check s3 --severity-modifier regulated-data for data buckets
3. Export security group configurations for all VPCs
4. Run cloud_posture_check.py --check sg for internet-facing resources
5. Review NACL rules for network segmentation gaps

Day 3 — IaC and Continuous Integration:

1. Review Terraform/CloudFormation templates in version control
2. Check CI/CD pipeline for IaC security gates
3. Validate findings against references/cspm-checks.md
4. Produce remediation plan with priority ordering (Critical → High → Medium)

Workflow 3: CI/CD Security Gate

Integrate posture checks into deployment pipelines to prevent misconfigured resources reaching production:

# Validate IaC before terraform apply
terraform show -json plan.json | \
  jq '[.resource_changes[].change.after | select(. != null)]' > resources.json
python3 scripts/cloud_posture_check.py resources.json --check all --json
if [ $? -eq 2 ]; then
  echo "Critical cloud security findings — blocking deployment"
  exit 1
fi

# Validate existing S3 bucket before modifying
aws s3api get-bucket-policy --bucket "${BUCKET}" | jq '.Policy | fromjson' | \
  python3 scripts/cloud_posture_check.py - --check s3 \
  --severity-modifier regulated-data --json

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Anti-Patterns

1. Running IAM analysis without checking escalation combos — Individual high-risk actions in isolation may appear low-risk. The danger is in combinations: iam:PassRole alone is not critical, but iam:PassRole + lambda:CreateFunction is a confirmed privilege escalation path. Always analyze the full statement, not individual actions.
2. Enabling only bucket-level public access block — AWS S3 has both account-level and bucket-level public access block settings. A bucket-level setting can override an account-level setting. Both must be configured. Account-level block alone is insufficient if any bucket has explicit overrides.
3. Treating --severity-modifier internet-facing as optional for public resources — Internet-facing resources have significantly higher exposure than internal resources. High findings on internet-facing infrastructure should be treated as critical. Always apply --severity-modifier internet-facing for DMZ, load balancer, and API gateway configurations.
4. Checking only administrator policies — Privilege escalation paths frequently originate from non-administrator policies that combine innocuous-looking permissions. All policies attached to production identities must be checked, not just policies with obvious elevated access.
5. Remediating findings without root cause analysis — Removing a dangerous permission without understanding why it was granted will result in re-addition. Document the business justification for every high-risk permission before removing it, to prevent silent re-introduction.
6. Ignoring service account over-permissioning — Service accounts are often over-provisioned during development and never trimmed for production. Every service account in production must be audited against AWS Access Analyzer or equivalent to identify and remove unused permissions.
7. Not applying severity modifiers for regulated data workloads — A high finding in a general-purpose S3 bucket is different from the same finding in a bucket containing PHI or cardholder data. Always use --severity-modifier regulated-data when assessing resources in regulated data environments.

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Cross-References

Skill	Relationship
incident-response	Critical findings (public S3, privilege escalation confirmed active) may trigger incident classification
threat-detection	Cloud posture findings create hunting targets — over-permissioned roles are likely lateral movement destinations
red-team	Red team exercises specifically test exploitability of cloud misconfigurations found in posture assessment
security-pen-testing	Cloud posture findings feed into the infrastructure security section of pen test assessments