Cross-Account Access

This guide explains how to set up Quilt across multiple AWS accounts, enabling you to separate your control plane (Quilt infrastructure) from your data plane (S3 buckets) for enhanced security, compliance, and organizational structure.

🎯 Architecture Overview

Why Cross-Account Setup?

Common Use Cases:

• 🏢 Organizational Separation: Different teams/departments own different accounts

• 🔒 Security Isolation: Separate sensitive data from application infrastructure

• 📊 Compliance Requirements: Regulatory requirements for data segregation

• 💰 Cost Management: Separate billing and resource management

• 🛡️ Blast Radius Reduction: Limit impact of security incidents

Account Structure

In this guide, we'll configure two accounts:

┌─────────────────────────────────────┐
│           Control Account           │
│  ┌─────────────────────────────────┐│
│  │     Quilt Infrastructure        ││
│  │  • CloudFormation Stack        ││
│  │  • Lambda Functions            ││
│  │  • Elasticsearch/OpenSearch    ││
│  │  • API Gateway                 ││
│  │  • Web Application             ││
│  └─────────────────────────────────┘│
└─────────────────────────────────────┘
                   │
                   │ Cross-Account
                   │ Access
                   ▼
┌─────────────────────────────────────┐
│            Data Account             │
│  ┌─────────────────────────────────┐│
│  │        S3 Buckets              ││
│  │  • Raw Data Bucket            ││
│  │  • Processed Data Bucket      ││
│  │  • Archive Bucket             ││
│  └─────────────────────────────────┘│
└─────────────────────────────────────┘

Account Definitions:

• Control Account: Contains the Quilt CloudFormation stack and infrastructure

• Data Account: Contains the S3 buckets with your actual data

🚀 Step-by-Step Implementation Guide

Prerequisites

Before starting, ensure you have:

• ✅ Administrative access to both AWS accounts

• ✅ Quilt already deployed in the Control Account

• ✅ S3 buckets created in the Data Account

• ✅ AWS CLI configured with appropriate profiles

Step 1: Configure S3 Object Ownership

Why This Matters: When Quilt (running in Control Account) writes objects to buckets in Data Account, you want the Data Account to own those objects for proper access control.

Implementation:

1. Navigate to S3 Console in Data Account

2. Select your bucket → Permissions → Object Ownership

3. Edit Object Ownership and select "Bucket owner enforced"

Using AWS CLI:

# Set object ownership to bucket owner enforced
aws s3api put-bucket-ownership-controls \
    --bucket your-data-bucket \
    --ownership-controls Rules='[{ObjectOwnership=BucketOwnerEnforced}]' \
    --profile data-account

Why "Bucket owner enforced"?

• ✅ Data Account automatically owns all objects

• ✅ Simplifies access control management

• ✅ Prevents ACL-based access complications

• ✅ Required for cross-account Quilt operations

Step 2: Create Cross-Account Bucket Policy

Purpose: Grant Quilt infrastructure in Control Account the necessary permissions to manage buckets in Data Account.

Create the Bucket Policy:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "QuiltCrossAccountAccess",
            "Effect": "Allow",
            "Principal": {
                "AWS": "arn:aws:iam::CONTROL-ACCOUNT-ID:root"
            },
            "Action": [
                "s3:GetObject",
                "s3:GetObjectAttributes", 
                "s3:GetObjectTagging",
                "s3:GetObjectVersion",
                "s3:GetObjectVersionAttributes",
                "s3:GetObjectVersionTagging",
                "s3:ListBucket",
                "s3:ListBucketVersions",
                "s3:DeleteObject",
                "s3:DeleteObjectVersion",
                "s3:PutObject",
                "s3:PutObjectTagging",
                "s3:GetBucketNotification",
                "s3:PutBucketNotification"
            ],
            "Resource": [
                "arn:aws:s3:::your-data-bucket",
                "arn:aws:s3:::your-data-bucket/*"
            ]
        }
    ]
}

Apply the Policy:

Console Method:

1. Go to S3 Console → Your Bucket → Permissions → Bucket Policy

2. Paste the JSON above (replace CONTROL-ACCOUNT-ID and your-data-bucket)

3. Click Save changes

CLI Method:

# Save policy to file
cat > bucket-policy.json << 'EOF'
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "QuiltCrossAccountAccess",
            "Effect": "Allow",
            "Principal": {
                "AWS": "arn:aws:iam::123456789012:root"
            },
            "Action": [
                "s3:GetObject",
                "s3:GetObjectAttributes",
                "s3:GetObjectTagging",
                "s3:GetObjectVersion", 
                "s3:GetObjectVersionAttributes",
                "s3:GetObjectVersionTagging",
                "s3:ListBucket",
                "s3:ListBucketVersions",
                "s3:DeleteObject",
                "s3:DeleteObjectVersion",
                "s3:PutObject",
                "s3:PutObjectTagging",
                "s3:GetBucketNotification",
                "s3:PutBucketNotification"
            ],
            "Resource": [
                "arn:aws:s3:::your-data-bucket",
                "arn:aws:s3:::your-data-bucket/*"
            ]
        }
    ]
}
EOF

# Apply the policy
aws s3api put-bucket-policy \
    --bucket your-data-bucket \
    --policy file://bucket-policy.json \
    --profile data-account

🔒 Security Note:

Quilt admins can still control user access to this bucket through the Quilt Admin Panel's Roles and Policies. The bucket policy only grants access to Quilt infrastructure, not end users.

Step 3: Configure Cross-Account SNS (Optional)

When You Need This: If you're using EventBridge integration or have existing SNS topics in the Data Account that Quilt should use for notifications.

Create SNS Topic Policy:

Add this statement to your SNS topic's resource policy in the Data Account:

{
    "Sid": "QuiltCrossAccountSNSAccess",
    "Effect": "Allow",
    "Principal": {
        "AWS": "arn:aws:iam::CONTROL-ACCOUNT-ID:root"
    },
    "Action": [
        "sns:GetTopicAttributes",
        "sns:Subscribe",
        "sns:Unsubscribe"
    ],
    "Resource": "arn:aws:sns:region:DATA-ACCOUNT-ID:your-topic-name"
}

Apply SNS Policy:

# Get current policy
aws sns get-topic-attributes \
    --topic-arn arn:aws:sns:region:DATA-ACCOUNT-ID:your-topic-name \
    --attribute-names Policy \
    --profile data-account

# Update policy (merge with existing statements)
aws sns set-topic-attributes \
    --topic-arn arn:aws:sns:region:DATA-ACCOUNT-ID:your-topic-name \
    --attribute-name Policy \
    --attribute-value file://sns-policy.json \
    --profile data-account

Configure in Quilt:

1. Open Quilt Admin Panel → Buckets

2. Add or edit your cross-account bucket

3. Under "Indexing and notifications", set the SNS Topic ARN

4. Save the configuration

Step 4: Set Up CloudTrail (Required)

Why CloudTrail is Required:

• 🔍 Security & Auditing: Track all S3 API calls

• 📊 User Analytics: Quilt uses CloudTrail data for user-facing analytics

• 🚨 Compliance: Many regulatory frameworks require audit trails

Implementation Options:

Option A: Quilt-Managed CloudTrail (Recommended)

If Quilt manages CloudTrail in the Control Account:

1. Check CloudFormation Stack in Control Account

2. Go to CloudFormation → Your Quilt Stack → Resources

3. Look for a CloudTrail resource (Quilt will auto-add your buckets)

Option B: Existing CloudTrail

If you have existing CloudTrail in either account:

1. Identify the Trail:

   # List trails in Data Account
   aws cloudtrail describe-trails --profile data-account
   
   # List trails in Control Account  
   aws cloudtrail describe-trails --profile control-account

2. Add S3 Data Events:

   # Add data events for your bucket
   aws cloudtrail put-event-selectors \
       --trail-name your-trail-name \
       --event-selectors '[
           {
               "ReadWriteType": "All",
               "IncludeManagementEvents": true,
               "DataResources": [
                   {
                       "Type": "AWS::S3::Object",
                       "Values": ["arn:aws:s3:::your-data-bucket/*"]
                   },
                   {
                       "Type": "AWS::S3::Bucket", 
                       "Values": ["arn:aws:s3:::your-data-bucket"]
                   }
               ]
           }
       ]' \
       --profile data-account

3. Update Quilt Configuration:

   • Go to CloudFormation → Your Quilt Stack → Parameters

   • Update the CloudTrail bucket parameter with your existing trail's S3 bucket

Option C: Cross-Account CloudTrail Access

If CloudTrail is in Data Account but Quilt needs access:

CloudTrail Bucket Policy:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "QuiltCloudTrailAccess",
            "Effect": "Allow",
            "Principal": {
                "AWS": "arn:aws:iam::CONTROL-ACCOUNT-ID:root"
            },
            "Action": [
                "s3:GetObject",
                "s3:ListBucket"
            ],
            "Resource": [
                "arn:aws:s3:::your-cloudtrail-bucket",
                "arn:aws:s3:::your-cloudtrail-bucket/*"
            ]
        }
    ]
}

Step 5: Add Bucket to Quilt

Final Configuration:

1. Open Quilt Admin Panel in Control Account

2. Navigate to Buckets → Add Bucket

3. Configure the bucket:

   • Bucket Name: your-data-bucket

   • Region: Same as the bucket

   • SNS Topic ARN: (If using cross-account SNS)

   • Event Notifications: Leave disabled if using EventBridge

4. Save and Test:

   • Click Save

   • Upload a test file to verify indexing works

   • Check Quilt catalog for the new file

🔧 Testing Your Cross-Account Setup

Verification Steps

1. Test Basic Access

# From Control Account, test bucket access
aws s3 ls s3://your-data-bucket --profile control-account

# Upload a test file
echo "Cross-account test" > test.txt
aws s3 cp test.txt s3://your-data-bucket/ --profile control-account

2. Verify Quilt Integration

1. Upload a file to your cross-account bucket

2. Wait 2-3 minutes for processing

3. Check Quilt catalog to see if the file appears

4. Test search functionality in Quilt

3. Check CloudTrail Logging

# Verify CloudTrail is capturing events
aws logs filter-log-events \
    --log-group-name CloudTrail/YourLogGroup \
    --filter-pattern "{ $.eventSource = s3.amazonaws.com }" \
    --profile data-account

Troubleshooting Common Issues

Issue 1: Access Denied Errors

Symptoms:

• Quilt can't access the bucket

• "Access Denied" in Quilt logs

Solutions:

1. Verify bucket policy is correctly applied

2. Check object ownership is set to "Bucket owner enforced"

3. Confirm account IDs in policies are correct

4. Test with AWS CLI from Control Account

Issue 2: Objects Not Appearing in Quilt

Symptoms:

• Files upload successfully but don't appear in Quilt catalog

Solutions:

1. Check CloudTrail is logging S3 data events

2. Verify SNS configuration if using custom topics

3. Review Quilt logs for processing errors

4. Manual re-index the bucket in Quilt Admin Panel

Issue 3: Permission Errors in Quilt Admin

Symptoms:

• Can't add bucket in Quilt Admin Panel

• IAM permission errors

Solutions:

1. Check Quilt IAM roles have cross-account assume permissions

2. Verify bucket policy allows required actions

3. Review CloudFormation stack permissions

🔐 Security Best Practices

Principle of Least Privilege

Bucket Policy Refinements: Instead of granting access to the entire Control Account root, consider restricting to specific Quilt roles:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "QuiltSpecificRoleAccess",
            "Effect": "Allow",
            "Principal": {
                "AWS": [
                    "arn:aws:iam::CONTROL-ACCOUNT-ID:role/QuiltLambdaRole",
                    "arn:aws:iam::CONTROL-ACCOUNT-ID:role/QuiltIndexerRole"
                ]
            },
            "Action": [
                "s3:GetObject",
                "s3:ListBucket",
                "s3:PutObject"
            ],
            "Resource": [
                "arn:aws:s3:::your-data-bucket",
                "arn:aws:s3:::your-data-bucket/*"
            ]
        }
    ]
}

Network Security

VPC Considerations:

• ✅ VPC Endpoints: Use S3 VPC endpoints to keep traffic within AWS network

• ✅ Security Groups: Restrict Lambda function network access

• ✅ NACLs: Additional network-level controls if required

Example VPC Endpoint Policy:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": "*",
            "Action": [
                "s3:GetObject",
                "s3:PutObject",
                "s3:ListBucket"
            ],
            "Resource": [
                "arn:aws:s3:::your-data-bucket",
                "arn:aws:s3:::your-data-bucket/*"
            ],
            "Condition": {
                "StringEquals": {
                    "aws:PrincipalAccount": ["CONTROL-ACCOUNT-ID"]
                }
            }
        }
    ]
}

Monitoring and Auditing

CloudWatch Alarms: Set up monitoring for cross-account access:

# Create alarm for failed S3 access attempts
aws cloudwatch put-metric-alarm \
    --alarm-name "CrossAccountS3AccessFailures" \
    --alarm-description "Monitor failed cross-account S3 access" \
    --metric-name ErrorCount \
    --namespace AWS/S3 \
    --statistic Sum \
    --period 300 \
    --threshold 5 \
    --comparison-operator GreaterThanThreshold \
    --profile control-account

CloudTrail Monitoring: Monitor specific cross-account activities:

{
    "eventVersion": "1.05",
    "userIdentity": {
        "type": "AssumedRole",
        "principalId": "AIDACKCEVSQ6C2EXAMPLE",
        "arn": "arn:aws:sts::CONTROL-ACCOUNT-ID:assumed-role/QuiltRole/QuiltLambda",
        "accountId": "CONTROL-ACCOUNT-ID"
    },
    "eventTime": "2024-08-26T10:30:00Z",
    "eventSource": "s3.amazonaws.com",
    "eventName": "GetObject",
    "resources": [
        {
            "ARN": "arn:aws:s3:::your-data-bucket/file.csv",
            "accountId": "DATA-ACCOUNT-ID"
        }
    ]
}

Compliance Considerations

Data Residency:

• 🌍 Regional Compliance: Ensure both accounts are in compliant regions

• 📋 Data Classification: Tag buckets with appropriate data classification

• 🔒 Encryption: Enable S3 encryption with appropriate KMS keys

Audit Requirements:

• 📊 Access Logging: Enable S3 access logging for detailed audit trails

• 🔍 Regular Reviews: Periodically review cross-account permissions

• 📝 Documentation: Maintain documentation of cross-account relationships

🚀 Advanced Configurations

Multi-Region Setup

For multi-region deployments:

# Replicate bucket policy across regions
for region in us-east-1 us-west-2 eu-west-1; do
    aws s3api put-bucket-policy \
        --bucket "your-data-bucket-${region}" \
        --policy file://bucket-policy.json \
        --region $region \
        --profile data-account
done

Automated Policy Management

CloudFormation Template for Bucket Policies:

AWSTemplateFormatVersion: '2010-09-09'
Description: 'Cross-account bucket policies for Quilt'

Parameters:
  ControlAccountId:
    Type: String
    Description: 'Control account ID where Quilt is deployed'
  
  DataBucketName:
    Type: String
    Description: 'Name of the data bucket'

Resources:
  CrossAccountBucketPolicy:
    Type: AWS::S3::BucketPolicy
    Properties:
      Bucket: !Ref DataBucketName
      PolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Sid: QuiltCrossAccountAccess
            Effect: Allow
            Principal:
              AWS: !Sub 'arn:aws:iam::${ControlAccountId}:root'
            Action:
              - 's3:GetObject'
              - 's3:GetObjectAttributes'
              - 's3:ListBucket'
              - 's3:PutObject'
              - 's3:DeleteObject'
            Resource:
              - !Sub 'arn:aws:s3:::${DataBucketName}'
              - !Sub 'arn:aws:s3:::${DataBucketName}/*'

📚 Additional Resources

AWS Documentation

• Cross-Account Access - AWS IAM cross-account access patterns

• S3 Bucket Policies - Comprehensive S3 policy guide

• CloudTrail Cross-Account - CloudTrail log sharing

Quilt-Specific Resources

• Quilt Admin API - Programmatic bucket management

• EventBridge Integration - Alternative event routing

• Security Best Practices - General Quilt security guidance

Tools and Scripts

• AWS CLI Reference - S3 API commands

• Policy Generator - AWS Policy Generator tool

• IAM Policy Simulator - Test policies before applying

📞 Support

Need Help with Cross-Account Setup?

• 📧 Email: [e-mail]

• 💬 Slack: Quilt Community

• 📖 Documentation: Quilt Docs

• 🐛 Issues: GitHub Issues

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Success! You now have a secure, compliant cross-account Quilt deployment that separates your control plane from your data plane while maintaining full functionality.