Classic ASP amazon s3 rest authorisation

Question

I am confused on what I am doing wrong here...

Answer 1

The Amazon Signature must be url encoded in a slightly different way to what VBSCript encodes. The following function will encode the result correctly:

JScript Version:

function amazonEncode(s)
{
    return Server.UrlEncode(s).replace(/\+/g,"%20").replace(/\%2E/g,".").replace(/\%2D/g,"-").replace(/\%7E/g,"~").replace(/\%5F/g,"_");
}

VBScript Version:

function amazonEncode(s)
    dim retval
    retval = Server.UrlEncode(s)
    retval = replace(retval,"+","%20")
    retval = replace(retval,"%2E",".")
    retval = replace(retval,"%2D","-")
    retval = replace(retval,"%7E","~")
    retval = replace(retval,"%5F","_")
    amazonEncode = retval
end function

As for base64, I used .NET's already built functionality for it. I had to create a DLL to wrap it, so that I could use it from JScript (or VBScript).

Here's how to create that dll:

Download the free C# 2010 Express and install it.
You also need to use two other tools that you won’t have a path to, so you will need to add the path to your PATH environment variable, so at a cmd prompt search for regasm.exe, guidgen.exe and sn.exe (you might find several versions – select the one with the latest date).
•   cd\
•   dir/s regasm.exe
•   dir/s sn.exe
•   dir/s guidgen.exe


So as an example, a COM object that has just one method which just returns “Hello”:
Our eventual aim is to use it like this:
<%@Language=JScript%>
<%
var x = Server.CreateObject("blah.whatever");
Response.Write(x.someMethod());
%>

or 

<%@Language=VBScript%>
<%
dim x
set x = Server.CreateObject("blah.whatever")
Response.Write x.someMethod()
%>

•   Start C# and create a new project
•   Select “Empty Project”
•   Give it a name – this becomes the namespace by default (the blah in the sample above)
•   Next save the project (so you know where to go for the next bit).  This will create a folder structure like so:
o   blah    this contains your solution files that the editor needs (blah.sln etc)
   blah    this contains your source code and project files
•   bin
o   Debug           the compiled output ends up here
•   Next, using the cmd console, navigate to the root blah folder and create a key pair file:
   sn –k key.snk
•   Next you need a unique guid (enter guidgen at the cmd prompt)
o   Select registry format
o   Click “New Guid”
o   Click “Copy”
•   Back to C# editor – from the menu, select Project – Add Class
•   Give it a name – this is the whatever in the sample above
•   After the opening brace just after the namespace line type:
   [GuidAttribute(“paste your guid here”)]
   remove the curly brackets from your pasted guid
•   You will need to add another “using” at the top
  using System.Runtime.InteropServices;
•   Finally you need to create someMethod

The final C# code looks like this (the bits in red may be different in your version):
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;

namespace blah
{
    [GuidAttribute("AEF4F27F-9E97-4189-9AD5-64386A1699A7")]
    public class whatever
    {
        public string someMethod()
        {
            return "Hello";
        }
    }
}

•   Next, from the menu, select Project – Properties
o   On the left, select Application and, for the Output type dropdown, select “Class Library”
o   On the left, select Signing and tick the “Sign the assembly” box, then browse to the key.snk file you made earlier
o   Save the properties (CTRL-S)
•   Next build the dll (Press F6) – This will create a dll in the Debug folder
•   Open a cmd window as administrator (right click cmd.exe and select “Run as Administrator”)
•   Navigate to the Debug folder and enter the following to register the assembly:
  regasm blah.dll /tlb:blah.tlb /codebase blah

That’s it – the above is a genuine COM component and will work in other applications, the example below allows for event handling and only really works in ASP due to the default property mechanism of ASP:

The code for the base64 stuff would be:

    // returns a base 64 encoded string that has been encrypted with SHA256
    // parameters:
    //  s   string to encrypt
    //  k   key to use during encryption
    public string getBase64SHA256(string s, string k)
    {
        HMACSHA256 sha = new HMACSHA256();
        System.Text.UTF8Encoding encoding = new System.Text.UTF8Encoding();
        sha.Key = encoding.GetBytes(k);
        byte[] hashBytes = sha.ComputeHash(encoding.GetBytes(s));
        return System.Convert.ToBase64String(hashBytes);
    }

    // returns a base 64 encoded string that has been encrypted with SHA1
    // parameters:
    //  s   string to encrypt
    //  k   key to use during encryption
    public string getBase64SHA1(string s, string k)
    {
        HMACSHA1 sha = new HMACSHA1();
        System.Text.UTF8Encoding encoding = new System.Text.UTF8Encoding();
        sha.Key = encoding.GetBytes(k);
        byte[] hashBytes = sha.ComputeHash(encoding.GetBytes(s));
        return System.Convert.ToBase64String(hashBytes);
    }

You would need the relevant usings:

using System.Security.Cryptography;

The signature in full must have all the query string name-value pairs in alphabetical order before computing the SHA and base64. Here is my version of the signature creator function:

function buildAmazonSignature(host,req,qstring)
{
    var str="", i, arr = String(qstring).split("&");

    for (i=0; ib[0])?1:0);
}

VBScript doesn't have a very good array sort facility, so you'll have to work that one out yourself - sorry

Also I have the timestamp in this format:

YYYY-MM-DDTHH:MM:SSZ

Also the stuff in the query string included the following:

AWSAccessKeyId
SignatureMethod
SignatureVersion
Version
Expires
Action

Hope that helps