Lambda Function

1import json
2import boto3
3import os
4
5s3_client = boto3.client('s3')
6
7def lambda_handler(event, context):
8    print(f"Received event: {json.dumps(event)}")
9
10    detail = event.get('detail', {})
11    bucket = detail.get('bucket', {}).get('name')
12    key = detail.get('object', {}).get('key')
13    size = detail.get('object', {}).get('size', 0)
14
15    # Validate S3 parameters before downloading
16    if not bucket or not key or not isinstance(key, str) or '/..' in key:
17        raise ValueError('Invalid S3 path')
18    if len(key) > 1024:
19        raise ValueError('S3 key exceeds maximum length')
20    if size > 512 * 1024 * 1024:
21        raise ValueError('File too large for Lambda processing')
22
23    # Download the file to /tmp
24    local_path = f"/tmp/{os.path.basename(key)}"
25    try:
26        s3_client.download_file(bucket, key, local_path)
27        print(f"Downloaded s3://{bucket}/{key} to {local_path}")
28
29        # Log metadata
30        metadata = {
31            'bucket': bucket,
32            'key': key,
33            'size_bytes': size,
34            'local_path': local_path,
35            'file_size_on_disk': os.path.getsize(local_path)
36        }
37        print(f"File metadata: {json.dumps(metadata)}")
38    finally:
39        try:
40            os.remove(local_path)
41        except OSError:
42            pass
43
44    return {
45        'statusCode': 200,
46        'body': metadata
47    }