.Net Notebooks

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   "source": [
    "# Generating Authorization Header for [SecureAuth](https://www.secureauth.com/)\r\n",
    "\r\n",
    "This notebooks describes how to generate an authorization header for the SecureAuth Authentication API using C#.  The [documentation for PowerShell](https://support.secureauth.com/hc/en-us/articles/360020784892-How-to-generate-an-Authorization-header-for-the-SecureAuth-API-using-Powershell) was used as a reference and may be refered to if need-be."
   ]
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   "cell_type": "markdown",
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   "source": [
    "The first item that is required is to organize all required information.  Typically the timestamp will be generated when the request is created.  The Application Id and Key are both provided by SecureAuth, more details may be found in the [Authentication API Guide](https://docs.secureauth.com/2006/en/authentication-api-guide.html)."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "dotnet_interactive": {
     "language": "csharp"
    }
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   "outputs": [],
   "source": [
    "var method=\"GET\";\r\n",
    "var timestamp = \"Fri, 14 May 2021 19:55:20.597 GMT\";\r\n",
    "var appId=\"c655ca3c5d5640a79f462084d34dada8\";\r\n",
    "var uri = \"/secureauth254/api/v2/users/49137\";\r\n",
    "var key = \"77c1a1fa63eb499155d730ae66cfe77a48363990c64cc49a8189244f4c88d08a\";"
   ]
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   "cell_type": "markdown",
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   "source": [
    "Our next step is to create the message.  Since this is a 'GET' request there will be no message body that we have to concern ourselves with.  Here we use [string interpolation](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/tokens/interpolated) for readability."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "dotnet_interactive": {
     "language": "csharp"
    }
   },
   "outputs": [],
   "source": [
    "var message = $\"{method}\\n{timestamp}\\n{appId}\\n{uri}\";"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Our next step is to grab the bytes for the key and the message.  The trick to this is that the key is a Hexadecimal string, this will need to be handled appropriately.  To do this, I have the static method 'HexStringToByteArray' below, which is a simple LINQ call."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "dotnet_interactive": {
     "language": "csharp"
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   "outputs": [],
   "source": [
    "static byte[] HexStringToByteArray(string hex)\r\n",
    "{\r\n",
    "\treturn Enumerable.Range(0, hex.Length)\r\n",
    "\t\t\t\t\t .Where(x => x % 2 == 0)\r\n",
    "\t\t\t\t\t .Select(x => Convert.ToByte(hex.Substring(x, 2), 16))\r\n",
    "\t\t\t\t\t .ToArray();\r\n",
    "}\r\n",
    "\r\n",
    "//Grab the bytes here\r\n",
    "var keyBytes = HexStringToByteArray(key);\r\n",
    "var messageByte = Encoding.UTF8.GetBytes(message);"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Now that we have the bytes we have to create an HMAC SHA256 hash of the message's byte array using the key.  The result is then Base64 encoded."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "dotnet_interactive": {
     "language": "csharp"
    }
   },
   "outputs": [],
   "source": [
    "var hmacProvider = new System.Security.Cryptography.HMACSHA256(keyBytes);\r\n",
    "var computedHash = hmacProvider.ComputeHash(messageByte);\r\n",
    "var hmac = Convert.ToBase64String(computedHash);"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Once we have this done, the final step would be to concatenate \"Basic\" to the returned Base64 value.  The result would ultimately look like this:\r\n",
    "\r\n",
    "```\r\n",
    "Basic U1AIyLQ+AVCeHAvQ/6+moHaz6oUK89V/ZH86trV8WHw=\r\n",
    "```\r\n",
    "\r\n",
    "However, for now since I already know what the value **should** be we will just compare the two and see if everything is working correctly."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "dotnet_interactive": {
     "language": "csharp"
    }
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True\r\n"
      ]
     },
     "output_type": "unknown"
    }
   ],
   "source": [
    "var hmacTest = \"U1AIyLQ+AVCeHAvQ/6+moHaz6oUK89V/ZH86trV8WHw=\";\r\n",
    "Console.WriteLine(hmacTest == hmac);"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": []
  }
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