aws-iam-best-practices

IAM policy review, hardening, and least privilege implementation

Install with Tessl CLI

npx tessl i github:boisenoise/skills-collections --skill aws-iam-best-practices

What are skills?

Overall
score

61%

Review — 49%

Does it follow best practices?

If you maintain this skill, you can automatically optimize it using the tessl CLI to improve its score:

npx tessl skill review --optimize ./path/to/skill

Learn more

Validation — 10 / 11 Passed

Validation for skill structure

SKILL.md

Review

Evals

AWS IAM Best Practices

Review and harden IAM policies following AWS security best practices and least privilege principles.

When to Use

Use this skill when you need to review IAM policies, implement least privilege access, or harden IAM security.

Core Principles

Least Privilege

Grant minimum permissions needed
Use managed policies when possible
Avoid wildcard (*) permissions
Regular access reviews

Defense in Depth

Enable MFA for all users
Use IAM roles instead of access keys
Implement service control policies (SCPs)
Enable CloudTrail for audit

Separation of Duties

Separate admin and user roles
Use different roles for different environments
Implement approval workflows
Regular permission audits

IAM Security Checks

Find Overly Permissive Policies

# List policies with full admin access
aws iam list-policies --scope Local \
  --query 'Policies[*].[PolicyName,Arn]' --output table | \
  grep -i admin

# Find policies with wildcard actions
aws iam list-policies --scope Local --query 'Policies[*].Arn' --output text | \
while read arn; do
  version=$(aws iam get-policy --policy-arn "$arn" \
    --query 'Policy.DefaultVersionId' --output text)
  doc=$(aws iam get-policy-version --policy-arn "$arn" \
    --version-id "$version" --query 'PolicyVersion.Document')
  if echo "$doc" | grep -q '"Action": "\*"'; then
    echo "Wildcard action in: $arn"
  fi
done

# Find inline policies (should use managed policies)
aws iam list-users --query 'Users[*].UserName' --output text | \
while read user; do
  policies=$(aws iam list-user-policies --user-name "$user" \
    --query 'PolicyNames' --output text)
  if [ -n "$policies" ]; then
    echo "Inline policies on user $user: $policies"
  fi
done

MFA Enforcement

# List users without MFA
aws iam get-credential-report --output text | \
  awk -F, 'NR>1 && $4=="false" {print $1}'

# Check if MFA is required in policies
aws iam list-policies --scope Local --query 'Policies[*].Arn' --output text | \
while read arn; do
  version=$(aws iam get-policy --policy-arn "$arn" \
    --query 'Policy.DefaultVersionId' --output text)
  doc=$(aws iam get-policy-version --policy-arn "$arn" \
    --version-id "$version" --query 'PolicyVersion.Document')
  if echo "$doc" | grep -q "aws:MultiFactorAuthPresent"; then
    echo "MFA enforced in: $arn"
  fi
done

# Enable MFA for a user (returns QR code)
aws iam create-virtual-mfa-device \
  --virtual-mfa-device-name user-mfa \
  --outfile /tmp/qr.png \
  --bootstrap-method QRCodePNG

Access Key Management

# Find old access keys (>90 days)
aws iam list-users --query 'Users[*].UserName' --output text | \
while read user; do
  aws iam list-access-keys --user-name "$user" \
    --query 'AccessKeyMetadata[*].[AccessKeyId,CreateDate,Status]' \
    --output text | \
  while read key_id create_date status; do
    age_days=$(( ($(date +%s) - $(date -d "$create_date" +%s)) / 86400 ))
    if [ $age_days -gt 90 ]; then
      echo "$user: Key $key_id is $age_days days old"
    fi
  done
done

# Rotate access key
OLD_KEY="AKIAIOSFODNN7EXAMPLE"
USER="myuser"

# Create new key
NEW_KEY=$(aws iam create-access-key --user-name "$USER")
echo "New key created. Update applications, then run:"
echo "aws iam delete-access-key --user-name $USER --access-key-id $OLD_KEY"

# Deactivate old key (test first)
aws iam update-access-key \
  --user-name "$USER" \
  --access-key-id "$OLD_KEY" \
  --status Inactive

Role and Policy Analysis

# List unused roles (no activity in 90 days)
aws iam list-roles --query 'Roles[*].[RoleName,RoleLastUsed.LastUsedDate]' \
  --output text | \
while read role last_used; do
  if [ "$last_used" = "None" ]; then
    echo "Never used: $role"
  fi
done

# Find roles with trust relationships to external accounts
aws iam list-roles --query 'Roles[*].RoleName' --output text | \
while read role; do
  trust=$(aws iam get-role --role-name "$role" \
    --query 'Role.AssumeRolePolicyDocument')
  if echo "$trust" | grep -q '"AWS":'; then
    echo "External trust: $role"
  fi
done

# Analyze policy permissions
aws iam simulate-principal-policy \
  --policy-source-arn arn:aws:iam::123456789012:user/myuser \
  --action-names s3:GetObject s3:PutObject \
  --resource-arns arn:aws:s3:::mybucket/*

IAM Policy Templates

Least Privilege S3 Access

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "s3:GetObject",
        "s3:PutObject"
      ],
      "Resource": "arn:aws:s3:::my-bucket/user-data/${aws:username}/*"
    },
    {
      "Effect": "Allow",
      "Action": "s3:ListBucket",
      "Resource": "arn:aws:s3:::my-bucket",
      "Condition": {
        "StringLike": {
          "s3:prefix": "user-data/${aws:username}/*"
        }
      }
    }
  ]
}

MFA-Required Policy

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Deny",
      "Action": "*",
      "Resource": "*",
      "Condition": {
        "BoolIfExists": {
          "aws:MultiFactorAuthPresent": "false"
        }
      }
    }
  ]
}

Time-Based Access

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": "ec2:*",
      "Resource": "*",
      "Condition": {
        "DateGreaterThan": {
          "aws:CurrentTime": "2026-01-01T00:00:00Z"
        },
        "DateLessThan": {
          "aws:CurrentTime": "2026-12-31T23:59:59Z"
        }
      }
    }
  ]
}

IP-Restricted Access

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Deny",
      "Action": "*",
      "Resource": "*",
      "Condition": {
        "NotIpAddress": {
          "aws:SourceIp": [
            "203.0.113.0/24",
            "198.51.100.0/24"
          ]
        }
      }
    }
  ]
}

IAM Hardening Checklist

User Management

Enable MFA for all users
Remove unused IAM users
Rotate access keys every 90 days
Use IAM roles instead of long-term credentials
Implement password policy (length, complexity, rotation)

Policy Management

Replace inline policies with managed policies
Remove wildcard (*) permissions
Implement least privilege
Use policy conditions (MFA, IP, time)
Regular policy reviews

Role Management

Use roles for EC2 instances
Implement cross-account roles properly
Review trust relationships
Remove unused roles
Use session tags for fine-grained access

Monitoring

Enable CloudTrail for IAM events
Set up CloudWatch alarms for IAM changes
Use AWS IAM Access Analyzer
Regular access reviews
Monitor for privilege escalation

Automated IAM Hardening

#!/usr/bin/env python3
# iam-hardening.py

import boto3
from datetime import datetime, timedelta

iam = boto3.client('iam')

def enforce_mfa():
    """Identify users without MFA"""
    users = iam.list_users()['Users']
    no_mfa = []
    
    for user in users:
        mfa_devices = iam.list_mfa_devices(
            UserName=user['UserName']
        )['MFADevices']
        
        if not mfa_devices:
            no_mfa.append(user['UserName'])
    
    return no_mfa

def rotate_old_keys():
    """Find access keys older than 90 days"""
    users = iam.list_users()['Users']
    old_keys = []
    
    for user in users:
        keys = iam.list_access_keys(
            UserName=user['UserName']
        )['AccessKeyMetadata']
        
        for key in keys:
            age = datetime.now(key['CreateDate'].tzinfo) - key['CreateDate']
            if age.days > 90:
                old_keys.append({
                    'user': user['UserName'],
                    'key_id': key['AccessKeyId'],
                    'age_days': age.days
                })
    
    return old_keys

def find_overpermissive_policies():
    """Find policies with wildcard actions"""
    policies = iam.list_policies(Scope='Local')['Policies']
    overpermissive = []
    
    for policy in policies:
        version = iam.get_policy_version(
            PolicyArn=policy['Arn'],
            VersionId=policy['DefaultVersionId']
        )
        
        doc = version['PolicyVersion']['Document']
        for statement in doc.get('Statement', []):
            if statement.get('Action') == '*':
                overpermissive.append(policy['PolicyName'])
                break
    
    return overpermissive

if __name__ == "__main__":
    print("IAM Hardening Report")
    print("=" * 50)
    
    print("\nUsers without MFA:")
    for user in enforce_mfa():
        print(f"  - {user}")
    
    print("\nOld access keys (>90 days):")
    for key in rotate_old_keys():
        print(f"  - {key['user']}: {key['age_days']} days")
    
    print("\nOverpermissive policies:")
    for policy in find_overpermissive_policies():
        print(f"  - {policy}")

Example Prompts

"Review my IAM policies for security issues"
"Find users without MFA enabled"
"Create a least privilege policy for S3 access"
"Identify overly permissive IAM roles"
"Generate an IAM hardening report"

Best Practices

Use AWS managed policies when possible
Implement policy versioning
Test policies in non-production first
Document policy purposes
Regular access reviews (quarterly)
Use IAM Access Analyzer
Implement SCPs for organization-wide controls

Kiro CLI Integration

kiro-cli chat "Use aws-iam-best-practices to review my IAM setup"
kiro-cli chat "Create a least privilege policy with aws-iam-best-practices"

Additional Resources

Repository: github.com/boisenoise/skills-collections
Last updated: 7 days ago
Created: 7 days ago

Is this your skill?

If you maintain this skill, you can claim it as your own. Once claimed, you can manage eval scenarios, bundle related skills, attach documentation or rules, and ensure cross-agent compatibility.