Hi All,

I am writing a simple request to upload the file to AWS. I have verified different my calculated signature but still getting an error message in the callout. Refer below code to verify.
 

public static void SendRequest(){    
         
        String fileString='fileString';
        String key='xxxxxxxxxxxxxxx';
        String secret='xxxxxxxxxxxxxxxxxxxxxxxx';
        //String formattedDateString= Datetime.now().formatGMT('EEE,dd MMM yyyy HH:mm:ss z');
        String formattedDateString = Datetime.now().format('EEE, dd MMM yyyy HH:mm:ss z','America/Los_Angeles');
        String bucketname = 'bucket';
        String method = 'PUT';
        String filename = 'MyFile';
        HttpRequest req = new HttpRequest();
        req.setMethod(method);
        
        req.setHeader('Host','bucket.s3.amazonaws.com');
        req.setEndpoint('https://bucket.s3.amazonaws.com' + '/'+ bucketname + '/' + filename);
        req.setHeader('Content-Length', string.valueOf(fileString.length()));
        req.setHeader('Content-Encoding', 'UTF-8');
    //  req.setHeader('Content-Disposition', 'attachment'); 
        req.setHeader('Content-type', 'application/json');        
        req.setHeader('Connection','keep-alive');
        req.setHeader('Date', formattedDateString);
        req.setHeader('ACL','public-read');
        req.setBody(fileString);     
                  
        String stringToSign ='PUT\n\n'+'application/json\n'+formattedDateString+'\n/'+bucketname+'/'+bucketname+'/'+filename;
        String encodedStringToSign = EncodingUtil.urlEncode(stringToSign,'UTF-8');        
        String signed = createSignature(stringToSign,secret);
        String authHeader = 'AWS' + ' ' + key + ':' + signed;
        req.setHeader('Authorization',authHeader);
        String decoded = EncodingUtil.urlDecode(encodedStringToSign , 'UTF-8');        
       
        Http http = new Http();
        try {
             HTTPResponse res = http.send(req);          
             System.debug('*Resp:'+String.ValueOF(res.getBody()));                    
             
             if(res.getStatusCode()==200 && res.getStatus()=='OK')
             {
                 String success= filename +' File has uploaded Successfully.';
//this is executing 
                  //inputFile=null;
             }

            } catch(System.CalloutException e) {
            
        }

   // return ApexPages.Currentpage();
}

 

    public static string createSignature(string canonicalBuffer,String secret){
        string sig;
        Blob mac = Crypto.generateMac('HMACSHA1', blob.valueof(canonicalBuffer),blob.valueof(secret));
        sig = EncodingUtil.base64Encode(mac);  
        return sig;
    }

When I perform callout I am getting a response:

<Error><Code>SignatureDoesNotMatch</Code><Message>The request signature we calculated does not match the signature you provided. Check your key and signing method.</Message><AWSAccessKeyId>kdjkhkghkjhkhdkhkdhkhfkh</AWSAccessKeyId><StringToSign>PUT

Thanks.