Scripts for creating and working with pre-signed URLS for S3 uploads.

post-gen.py

import boto3
import json

def generate_presigned_post(bucket_name, key_prefix='uploads/', expiration=3600):
    # Initialize the S3 client
    s3 = boto3.client('s3')

    # Generate the pre-signed POST request
    response = s3.generate_presigned_post(
        Bucket=bucket_name,
        Key=f"{key_prefix}${{filename}}",  # Arbitrary filenames allowed
        Fields={"acl": "private"},  # Default ACL for uploaded files
        Conditions=[
            {"acl": "private"},  # Enforce private uploads
            ["starts-with", "$key", key_prefix],  # Ensure files follow prefix structure
        ],
        ExpiresIn=expiration  # URL expiration time in seconds
    )
    return response

def save_presigned_post_to_file(bucket_name, file_name='presigned_post.json'):
    # Generate the POST data
    post_data = generate_presigned_post(bucket_name)

    # Save the JSON data to a file
    with open(file_name, 'w') as f:
        json.dump(post_data, f, indent=4)

    print(f"Pre-signed POST request saved to {file_name}")

# Usage example
bucket_name = 'more-dogfish-20230223041658282000000004'
save_presigned_post_to_file(bucket_name)

upload.sh

#!/bin/bash

# Usage: ./upload.sh my-local-file.txt
if [ $# -ne 1 ]; then
  echo "Usage: $0 <file-to-upload>"
  exit 1
fi

FILE_TO_UPLOAD=$1
POST_FILE="presigned_post.json"

# Check if the presigned POST JSON file exists
if [ ! -f "$POST_FILE" ]; then
  echo "Error: $POST_FILE not found!"
  exit 1
fi

# Get the hostname and current date in YYYY-MM-DD format
HOSTNAME=$(hostname)
CURRENT_DATE=$(date +%F)  # %F outputs YYYY-MM-DD

# Create the S3 "folder" structure using hostname and date as prefixes
PREFIX="${HOSTNAME}/${CURRENT_DATE}"
FILENAME=$(basename "$FILE_TO_UPLOAD")
KEY="${PREFIX}/${FILENAME}"

# Extract fields from the JSON file
URL=$(jq -r '.url' "$POST_FILE")
ACL=$(jq -r '.fields.acl' "$POST_FILE")
AWS_ACCESS_KEY_ID=$(jq -r '.fields.AWSAccessKeyId' "$POST_FILE")
POLICY=$(jq -r '.fields.policy' "$POST_FILE")
SIGNATURE=$(jq -r '.fields.signature' "$POST_FILE")

# Use curl to upload the file with the new key
curl -F "key=uploads/$KEY" \
     -F "acl=$ACL" \
     -F "AWSAccessKeyId=$AWS_ACCESS_KEY_ID" \
     -F "policy=$POLICY" \
     -F "signature=$SIGNATURE" \
     -F "file=@$FILE_TO_UPLOAD" \
     "$URL"

echo "File uploaded to: $KEY"