Tweet from Powershell using oAuth

I wanted to be able to post tweets from a Powershell script. There are alot of old blog posts and examples of composing tweets before Twitter introduced oAuth. I've seen a few examples of Powershell scripts that can post tweets using external dll's to handle the oAuth authentication. I wanted to keep my script self contained and only use .NET Framework assemblies where necessary and not rely on 3rd party dlls.

The first step is to create a Twitter application by logging on to http://dev.twitter.com. Complete the Application Details making sure to set the Application Type - Access to at least Read and Write. Make a note of the following:

• Consumer key
• Consumer secret
• Access token
• Access token secret

You'll need to update the associated Powershell script variables with your real values.

[Reflection.Assembly]::LoadWithPartialName("System.Security")
[Reflection.Assembly]::LoadWithPartialName("System.Net")

$status = [System.Uri]::EscapeDataString("My first tweet from Powershell");
$oauth_consumer_key = "<consumer key>";
$oauth_consumer_secret = "<consumer secret>";
$oauth_token = "<auth token>";
$oauth_token_secret = "<auth token secret>";
$oauth_nonce = [System.Convert]::ToBase64String([System.Text.Encoding]::ASCII.GetBytes([System.DateTime]::Now.Ticks.ToString()));
$ts = [System.DateTime]::UtcNow - [System.DateTime]::ParseExact("01/01/1970", "dd/MM/yyyy", $null).ToUniversalTime();
$oauth_timestamp = [System.Convert]::ToInt64($ts.TotalSeconds).ToString();

$signature = "POST&";
$signature += [System.Uri]::EscapeDataString("http://api.twitter.com/1/statuses/update.json") + "&";
$signature += [System.Uri]::EscapeDataString("oauth_consumer_key=" + $oauth_consumer_key + "&");
$signature += [System.Uri]::EscapeDataString("oauth_nonce=" + $oauth_nonce + "&"); 
$signature += [System.Uri]::EscapeDataString("oauth_signature_method=HMAC-SHA1&");
$signature += [System.Uri]::EscapeDataString("oauth_timestamp=" + $oauth_timestamp + "&");
$signature += [System.Uri]::EscapeDataString("oauth_token=" + $oauth_token + "&");
$signature += [System.Uri]::EscapeDataString("oauth_version=1.0&");
$signature += [System.Uri]::EscapeDataString("status=" + $status);

$signature_key = [System.Uri]::EscapeDataString($oauth_consumer_secret) + "&" + [System.Uri]::EscapeDataString($oauth_token_secret);

$hmacsha1 = new-object System.Security.Cryptography.HMACSHA1;
$hmacsha1.Key = [System.Text.Encoding]::ASCII.GetBytes($signature_key);
$oauth_signature = [System.Convert]::ToBase64String($hmacsha1.ComputeHash([System.Text.Encoding]::ASCII.GetBytes($signature)));

$oauth_authorization = 'OAuth ';
$oauth_authorization += 'oauth_consumer_key="' + [System.Uri]::EscapeDataString($oauth_consumer_key) + '",';
$oauth_authorization += 'oauth_nonce="' + [System.Uri]::EscapeDataString($oauth_nonce) + '",';
$oauth_authorization += 'oauth_signature="' + [System.Uri]::EscapeDataString($oauth_signature) + '",';
$oauth_authorization += 'oauth_signature_method="HMAC-SHA1",'
$oauth_authorization += 'oauth_timestamp="' + [System.Uri]::EscapeDataString($oauth_timestamp) + '",'
$oauth_authorization += 'oauth_token="' + [System.Uri]::EscapeDataString($oauth_token) + '",';
$oauth_authorization += 'oauth_version="1.0"';

$post_body = [System.Text.Encoding]::ASCII.GetBytes("status=" + $status); 
[System.Net.HttpWebRequest] $request = [System.Net.WebRequest]::Create("http://api.twitter.com/1/statuses/update.json");
$request.Method = "POST";
$request.Headers.Add("Authorization", $oauth_authorization);
$request.ContentType = "application/x-www-form-urlencoded";
$body = $request.GetRequestStream();
$body.write($post_body, 0, $post_body.length);
$body.flush();
$body.close();
$response = $request.GetResponse();