Class to generate V4 style signing keys for direct browser upload to S3 bucket

DirectS3Upload.php

<?php namespace NeverBounce\Repositories;

use Carbon\Carbon;

class DirectS3Upload {

    /**
     * Supported regions
     * @var array
     */
    protected $supported = [
        'default' => [
            'human' => 'US Standard', // Human friendly name
            'region' => 'us-west-2', // AWS region code
            'bucket' => 'my-default-bucket', // S3 bucket name
        ],
        'eu-frankfurt' => [
            'human' => 'EU Frankfurt',
            'region' => 'eu-central-1',
            'bucket' => 'my-eu-bucket'
        ],
    ];

    /**
     * Stores region short string
     * @var bool|void
     */
    protected $region;

    /**
     * S3Repository constructor.
     * @param \User $user
     */
    public function __construct(\User $user)
    {
        $this->region = $user->getMeta('data_region', 'default');
    }

    /**
     * Returns human friendly name
     * @return mixed
     */
    public function getHuman()
    {
        return $this->supported[$this->region]['human'];
    }

    /**
     * Returns AWS region code
     * @return mixed
     */
    public function getRegionCode()
    {
        return $this->supported[$this->region]['region'];
    }

    /**
     * Returns S3 bucket name
     * @return mixed
     */
    public function getBucketName()
    {
        return $this->supported[$this->region]['bucket'];
    }

    public function getDataRegion()
    {
        return $this->region;
    }

    /**
     * Returns the url for accessing and uploading to the bucket
     * @return string
     */
    public function getUrl()
    {
        return sprintf("https://%s.s3.amazonaws.com/", $this->getBucketName());
    }

    /**
     * Get all the necessary details to directly upload a private file to S3
     * asynchronously with JavaScript using the Signature V4.
     *
     * @return array ['url', 'inputs'] the forms url to s3 and any inputs the form will need.
     */
    public function getS3Details() {
        // Options and Settings
        $awsKey = env('aws.key');
        $awsSecret = env('aws.secret');
        $acl = 'private';

        $algorithm = "AWS4-HMAC-SHA256";
        $service = "s3";
        $date = gmdate('Ymd\THis\Z');
        $shortDate = gmdate("Ymd");
        $requestType = "aws4_request";
        $expires = "86400"; // 24 Hours
        $successStatus = "201";

        // Step 1: Generate the Scope
        $scope = [
            $awsKey,
            $shortDate,
            $this->getRegionCode(),
            $service,
            $requestType
        ];
        $credentials = implode('/', $scope);

        // Step 2: Making a Base64 Policy
        $policy = [
            'expiration' => gmdate('Y-m-d\TG:i:s\Z', strtotime('+6 hours')),
            'conditions' => [
                ['bucket' => $this->getBucketName()],
                ['acl' => $acl],
                ['starts-with', '$key', 'uploads/'],
                ['starts-with', '$Content-Type', ''],
                ['success_action_status' => $successStatus],
                ['x-amz-credential' => $credentials],
                ['x-amz-algorithm' => $algorithm],
                ['x-amz-date' => $date],
                ['x-amz-expires' => $expires],
            ]
        ];
        $base64Policy = base64_encode(json_encode($policy));

        // Step 3: Signing your Request (Making a Signature)
        $dateKey = hash_hmac('sha256', $shortDate, 'AWS4' . $awsSecret, true);
        $dateRegionKey = hash_hmac('sha256', $this->getRegionCode(), $dateKey, true);
        $dateRegionServiceKey = hash_hmac('sha256', $service, $dateRegionKey, true);
        $signingKey = hash_hmac('sha256', $requestType, $dateRegionServiceKey, true);

        $signature = hash_hmac('sha256', $base64Policy, $signingKey);

        // Step 4: Build form inputs
        // This is the data that will get sent with the form to S3
        return [
            'Content-Type' => '',
            'key' => 'uploads/${filename}',
            'acl' => $acl,
            'success_action_status' => $successStatus,
            'policy' => $base64Policy,
            'X-amz-credential' => $credentials,
            'X-amz-algorithm' => $algorithm,
            'X-amz-date' => $date,
            'X-amz-expires' => $expires,
            'X-amz-signature' => $signature
        ];
    }

}