Salesforce Apex AWS S3 Signature Helper class

AWS_Helper.cls

/**
 * Created by gtandeciarz on 12/14/16.
 */

public class AWS_Helper {
    public string secret { get; set; }
    public string key { get; set; }
    public string bucket {get;set;}
    public String endpoint_x = 'https://s3.amazonaws.com/';
    public Integer version = 2;
    public static AWS_Setting__c settings;
    static {
        settings = AWS_Setting__c.getInstance('CaseAttachments');
    }
    public AWS_Helper() {
        this.secret = AWS_Helper.settings.Access_Secret__c;
        this.key = AWS_Helper.settings.Access_Key__c;
        this.bucket = AWS_Helper.settings.Bucket__c;
    }
    public AWS_Helper(Integer versionInt) {
        this.secret = AWS_Helper.settings.Access_Secret__c;
        this.key = AWS_Helper.settings.Access_Key__c;
        this.bucket = AWS_Helper.settings.Bucket__c;
        this.version = versionInt;
    }

    public Blob createCanonicalRequest(String method, String queryString, Map<String, String> headers, String payload) {
        String canonicalRequest = method + '\n';
        canonicalRequest += '/' + '\n';
        canonicalRequest += queryString + '\n';

        List<String> headersList = new List<String>(headers.keySet());
        headersList.sort();

        for (String header : headersList) {
            String headerContent = header.toLowerCase() + ':' + headers.get(header).trim();
            canonicalRequest += headerContent + '\n';
        }

        for (String header : headersList) {
            canonicalRequest += header.toLowerCase() + ';';
        }

        canonicalRequest = canonicalRequest.removeEnd(';');
        canonicalRequest += '\n';
        canonicalRequest += EncodingUtil.convertToHex(Crypto.generateDigest('SHA256', Blob.valueOf(payload))).toLowerCase();

        return Crypto.generateDigest('SHA256', Blob.valueOf(canonicalRequest));
    }

    public String getStringToSignV4(Blob canonicalRequest, Datetime requestdate, String region, String service) {
        String stringToSign = 'AWS4-HMAC-SHA256' + '\n';

        String formatedDate = requestdate.formatGmt('yyyyMMdd') + 'T' + requestdate.formatGmt('hhmmss') + 'Z';
        stringToSign += formatedDate + '\n';
        stringToSign += requestdate.formatGmt('yyyyMMdd') + '/' + region + '/' + service + '/aws4_request\n';
        //stringToSign += String.valueOf(canonicalRequest);
        // stringToSign += EncodingUtil.base64Encode(canonicalRequest); COMMENTED OUT THIS LINE AND REPLACED WITH THE ONE BELOW
        stringToSign += EncodingUtil.convertToHex(Crypto.generateDigest('SHA-256', canonicalRequest));

        return stringToSign;
    }

    public String signatureV4(String secret, String today, String region, String service, String stringToSign) {
        Blob privateKey = Crypto.generateMac('HmacSHA256', Crypto.generateMac('HmacSHA256', Crypto.generateMac('HmacSHA256', Crypto.generateMac('HmacSHA256',
                Blob.valueOf(today), Blob.valueOf('AWS4' + secret)),
                Blob.valueOf(region)),
                Blob.valueOf(service)),
                Blob.valueOf('aws4_request'));
        return EncodingUtil.convertToHex(Crypto.generateMac('HmacSHA256', Blob.valueOf(stringToSign), privateKey));
    }

    public static string GetSigningSignatureV2(string stringToSign, string key){
        Blob mac = Crypto.generateMac('HMACSHA1', blob.valueOf(stringToSign), blob.valueof(key));
        String signed = EncodingUtil.base64Encode(mac);
        return signed;
    }

    public String GetAuthHeaderStringV2(String stringToSign){
        return 'AWS' + ' ' + this.key + ':' + AWS_Helper.GetSigningSignatureV2(stringToSign, this.secret);
    }

    public HttpRequest generateHttpRequest(Attachment a, String fileName){
        return this.generateHttpRequest(a.Name, a.contentType,a.Body,fileName);
    }
    public HttpRequest generateHttpRequest(String attachmentName, string attachmentContentType, Blob body, String fileName){

        string extension = '.' + attachmentName.substringAfterLast('.');

        String contentType = attachmentContentType == null ? 'binary/octet-stream' :  attachmentContentType;
        System.debug('extension: ' + extension);
        System.debug('Filename: ' + fileName);
        String attachmentBody = EncodingUtil.base64Encode(body);
        String formattedDateString = DateTime.now().formatGMT('EEE, dd MMM yyyy HH:mm:ss z');// + '+0000';
        String bucketname = this.bucket;//you can write the bucket name where files should be uploaded
        String host = 's3.amazonaws.com';//aws server base url'https://s3.amazonaws.com/'+bucketName+'/'+uploadedFilename

        String method = 'PUT';

        String endpointUrl = 'https://' + host + '/' + bucketname + '/' + filename;
        //endpointUrl = 'https://' + bucketname + '.' + host + '/' + filename;
        HttpRequest req = new HttpRequest();
        req.setMethod(method);
        req.setEndpoint(endpointUrl);
        //host = bucketname + '.' + host;
        //req.setHeader('Host',  host);
        req.setHeader('Content-Length', String.valueOf(attachmentBody.length()));
        req.setHeader('Content-Type', contentType);
        req.setHeader('Connection', 'keep-alive');
        req.setHeader('Date', formattedDateString);
        req.setHeader('x-amz-server-side-encryption', 'AES256');
        req.setHeader('ACL', 'public-read');
        Blob blobBody = EncodingUtil.base64Decode(attachmentBody);
        req.setBodyAsBlob(blobBody);

        String stringToSign = method+'\n\n'
                + contentType + '\n'
                + formattedDateString + '\n'
                + 'x-amz-server-side-encryption:AES256\n'
                + '/' + bucketname
                + '/'
                + filename;
        System.debug(stringToSign);
        System.debug('key: ' + this.key);
        System.debug('secret: ' + this.secret);
        req.setHeader('Authorization', GetAuthHeaderStringV2(stringToSign));

        return req;
    }

}