aws-s3

AWS S3

Manage Amazon S3 object storage with production-grade security, lifecycle policies, replication, and access controls.

When to Use This Skill

• Creating S3 buckets with security hardening (encryption, public access block, versioning)
• Writing bucket policies to enforce HTTPS, restrict IP ranges, or grant cross-account access
• Setting up lifecycle rules to transition objects between storage classes
• Configuring cross-region replication for disaster recovery
• Generating presigned URLs for temporary access to private objects
• Setting up static website hosting or CloudFront origins
• Troubleshooting access denied errors or policy conflicts

Prerequisites

• AWS CLI v2 installed and configured
• Least-privilege IAM permissions for the selected bucket/object operations; grant only the required KMS actions for SSE-KMS. Do not grant wildcard service permissions as a default.
• For replication: IAM role with replication permissions and destination bucket in target region
• For logging: a separate logging bucket with appropriate ACL

Create and Secure a Bucket

# Create a bucket (us-east-1 does not need LocationConstraint)
aws s3api create-bucket \
  --bucket my-app-data-prod \
  --region us-east-1

# Create a bucket in another region
aws s3api create-bucket \
  --bucket my-app-data-dr \
  --region us-west-2 \
  --create-bucket-configuration LocationConstraint=us-west-2

# Block ALL public access (always do this first)
aws s3api put-public-access-block \
  --bucket my-app-data-prod \
  --public-access-block-configuration '{
    "BlockPublicAcls": true,
    "IgnorePublicAcls": true,
    "BlockPublicPolicy": true,
    "RestrictPublicBuckets": true
  }'

# Enable versioning
aws s3api put-bucket-versioning \
  --bucket my-app-data-prod \
  --versioning-configuration Status=Enabled

# Enable server-side encryption with SSE-KMS
aws s3api put-bucket-encryption \
  --bucket my-app-data-prod \
  --server-side-encryption-configuration '{
    "Rules": [{
      "ApplyServerSideEncryptionByDefault": {
        "SSEAlgorithm": "aws:kms",
        "KMSMasterKeyID": "alias/s3-key"
      },
      "BucketKeyEnabled": true
    }]
  }'

# Enable access logging
aws s3api put-bucket-logging \
  --bucket my-app-data-prod \
  --bucket-logging-status '{
    "LoggingEnabled": {
      "TargetBucket": "my-access-logs-bucket",
      "TargetPrefix": "s3-logs/my-app-data-prod/"
    }
  }'

# Add tags
aws s3api put-bucket-tagging \
  --bucket my-app-data-prod \
  --tagging '{
    "TagSet": [
      {"Key": "Environment", "Value": "production"},
      {"Key": "Team", "Value": "platform"},
      {"Key": "DataClassification", "Value": "confidential"}
    ]
  }'

Bucket Policies

# Apply a bucket policy (enforce HTTPS and restrict to VPC endpoint)
aws s3api put-bucket-policy \
  --bucket my-app-data-prod \
  --policy '{
    "Version": "2012-10-17",
    "Statement": [
      {
        "Sid": "DenyInsecureTransport",
        "Effect": "Deny",
        "Principal": "*",
        "Action": "s3:*",
        "Resource": [
          "arn:aws:s3:::my-app-data-prod",
          "arn:aws:s3:::my-app-data-prod/*"
        ],
        "Condition": {
          "Bool": {"aws:SecureTransport": "false"}
        }
      },
      {
        "Sid": "RestrictToVPCEndpoint",
        "Effect": "Deny",
        "Principal": "*",
        "Action": "s3:*",
        "Resource": [
          "arn:aws:s3:::my-app-data-prod",
          "arn:aws:s3:::my-app-data-prod/*"
        ],
        "Condition": {
          "StringNotEquals": {
            "aws:sourceVpce": "vpce-abc123"
          }
        }
      }
    ]
  }'

Cross-account access policy:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "CrossAccountRead",
      "Effect": "Allow",
      "Principal": {
        "AWS": "arn:aws:iam::987654321098:role/DataAnalystRole"
      },
      "Action": [
        "s3:GetObject",
        "s3:ListBucket"
      ],
      "Resource": [
        "arn:aws:s3:::my-app-data-prod",
        "arn:aws:s3:::my-app-data-prod/shared/*"
      ]
    }
  ]
}

Lifecycle Rules

# Apply a comprehensive lifecycle configuration
aws s3api put-bucket-lifecycle-configuration \
  --bucket my-app-data-prod \
  --lifecycle-configuration '{
    "Rules": [
      {
        "ID": "TierDownOldData",
        "Status": "Enabled",
        "Filter": {"Prefix": "data/"},
        "Transitions": [
          {"Days": 30, "StorageClass": "STANDARD_IA"},
          {"Days": 90, "StorageClass": "GLACIER_IR"},
          {"Days": 180, "StorageClass": "GLACIER"},
          {"Days": 365, "StorageClass": "DEEP_ARCHIVE"}
        ]
      },
      {
        "ID": "ExpireLogs",
        "Status": "Enabled",
        "Filter": {"Prefix": "logs/"},
        "Expiration": {"Days": 90},
        "Transitions": [
          {"Days": 7, "StorageClass": "STANDARD_IA"},
          {"Days": 30, "StorageClass": "GLACIER"}
        ]
      },
      {
        "ID": "CleanupOldVersions",
        "Status": "Enabled",
        "Filter": {"Prefix": ""},
        "NoncurrentVersionTransitions": [
          {"NoncurrentDays": 30, "StorageClass": "STANDARD_IA"},
          {"NoncurrentDays": 90, "StorageClass": "GLACIER"}
        ],
        "NoncurrentVersionExpiration": {"NoncurrentDays": 180}
      },
      {
        "ID": "AbortIncompleteUploads",
        "Status": "Enabled",
        "Filter": {"Prefix": ""},
        "AbortIncompleteMultipartUpload": {"DaysAfterInitiation": 7}
      },
      {
        "ID": "ExpireDeleteMarkers",
        "Status": "Enabled",
        "Filter": {"Prefix": ""},
        "Expiration": {"ExpiredObjectDeleteMarker": true}
      }
    ]
  }'

Cross-Region Replication

# Enable replication (requires versioning on both buckets)
aws s3api put-bucket-replication \
  --bucket my-app-data-prod \
  --replication-configuration '{
    "Role": "arn:aws:iam::123456789012:role/S3ReplicationRole",
    "Rules": [
      {
        "ID": "ReplicateAll",
        "Status": "Enabled",
        "Priority": 1,
        "Filter": {"Prefix": ""},
        "Destination": {
          "Bucket": "arn:aws:s3:::my-app-data-dr",
          "StorageClass": "STANDARD_IA",
          "EncryptionConfiguration": {
            "ReplicaKmsKeyID": "arn:aws:kms:us-west-2:123456789012:key/dr-key-id"
          },
          "Metrics": {"Status": "Enabled", "EventThreshold": {"Minutes": 15}},
          "ReplicationTime": {"Status": "Enabled", "Time": {"Minutes": 15}}
        },
        "DeleteMarkerReplication": {"Status": "Enabled"},
        "SourceSelectionCriteria": {
          "SseKmsEncryptedObjects": {"Status": "Enabled"}
        }
      }
    ]
  }'

# Check replication status
aws s3api head-object \
  --bucket my-app-data-prod \
  --key data/important-file.json \
  --query "ReplicationStatus"

Presigned URLs

# Generate a presigned URL for downloading (valid 1 hour)
aws s3 presign s3://my-app-data-prod/reports/quarterly.pdf \
  --expires-in 3600

# Upload signing requires an SDK configured for PutObject, not `aws s3 presign`.
# See the SDK procedure linked below; no s3api generate-presigned-url command exists.

The AWS CLI presign command signs GET requests. For PUT uploads, use the installed SDK's documented presigner with PutObject, a bounded expiry and the required content headers. Treat signed URLs as bearer secrets and do not print or persist them unnecessarily.

Common S3 Operations

# Preview a sync first; --delete removes remote objects absent locally.
# Use long cache lifetimes only for immutable, versioned assets.
aws s3 sync ./build s3://my-app-data-prod/static/ --dryrun

# Apply only after reviewing the preview within authorized scope.
# Do not set Content-Encoding: gzip unless source bytes are actually compressed.
# Sync a local directory to S3
aws s3 sync ./build s3://my-app-data-prod/static/ \
  --delete \
  --exclude "*.tmp" \
  --cache-control "max-age=31536000"

# Copy with storage class
aws s3 cp large-archive.tar.gz s3://my-app-data-prod/archives/ \
  --storage-class GLACIER_IR

# List objects with size summary
aws s3 ls s3://my-app-data-prod/ --recursive --summarize --human-readable

# Remove all objects with a prefix
aws s3 rm s3://my-app-data-prod/temp/ --recursive

# Get bucket size via CloudWatch (most efficient for large buckets)
aws cloudwatch get-metric-statistics \
  --namespace AWS/S3 \
  --metric-name BucketSizeBytes \
  --dimensions Name=BucketName,Value=my-app-data-prod Name=StorageType,Value=StandardStorage \
  --start-time "$(date -u -d '2 days ago' +%Y-%m-%dT%H:%M:%SZ)" \
  --end-time "$(date -u +%Y-%m-%dT%H:%M:%SZ)" \
  --period 86400 \
  --statistics Average \
  --output table

Terraform S3 Bucket

resource "aws_s3_bucket" "main" {
  bucket = "my-app-data-prod"

  tags = {
    Environment        = "production"
    DataClassification = "confidential"
  }
}

resource "aws_s3_bucket_versioning" "main" {
  bucket = aws_s3_bucket.main.id
  versioning_configuration {
    status = "Enabled"
  }
}

resource "aws_s3_bucket_public_access_block" "main" {
  bucket = aws_s3_bucket.main.id

  block_public_acls       = true
  block_public_policy     = true
  ignore_public_acls      = true
  restrict_public_buckets = true
}

resource "aws_s3_bucket_server_side_encryption_configuration" "main" {
  bucket = aws_s3_bucket.main.id

  rule {
    apply_server_side_encryption_by_default {
      sse_algorithm     = "aws:kms"
      kms_master_key_id = aws_kms_key.s3.arn
    }
    bucket_key_enabled = true
  }
}

resource "aws_s3_bucket_lifecycle_configuration" "main" {
  bucket = aws_s3_bucket.main.id

  rule {
    id     = "tier-down"
    status = "Enabled"

    transition {
      days          = 30
      storage_class = "STANDARD_IA"
    }

    transition {
      days          = 90
      storage_class = "GLACIER"
    }

    noncurrent_version_transition {
      noncurrent_days = 30
      storage_class   = "GLACIER"
    }

    noncurrent_version_expiration {
      noncurrent_days = 180
    }

    abort_incomplete_multipart_upload {
      days_after_initiation = 7
    }
  }
}

resource "aws_s3_bucket_policy" "enforce_https" {
  bucket = aws_s3_bucket.main.id

  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [{
      Sid       = "DenyInsecureTransport"
      Effect    = "Deny"
      Principal = "*"
      Action    = "s3:*"
      Resource  = [
        aws_s3_bucket.main.arn,
        "${aws_s3_bucket.main.arn}/*"
      ]
      Condition = {
        Bool = { "aws:SecureTransport" = "false" }
      }
    }]
  })
}

Troubleshooting

Related Skills

• aws-iam (aws-iam) - Bucket and object access policies
• aws-vpc (aws-vpc) - VPC endpoints for private S3 access
• aws-cost-optimization (aws-cost-optimization) - Storage class optimization
• terraform-aws (terraform-aws) - IaC deployment for S3
• cloudformation (cloudformation) - AWS-native S3 templates

Limitations

• VPC-endpoint deny policies can lock out console/admin access; verify the endpoint and a recovery path before applying. Policy, lifecycle and tagging PUTs replace existing configurations: inspect and preserve required entries.
• Infrastructure commands can disrupt services: confirm target host/scope and have backups/snapshots before mutating state.
• Docs-only import: upstream scripts and templates not bundled.