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Talking SOAP With Exchange


Previously, talking to Exchange without using Microsoft products was pretty much out of the question. The binary MAPI protocol is proprietary and poorly documented. Exchange supports IMAP and POP, but these protocols only give acesss to emails, not the calendar, address book, todo lists etc. But beginning with version 2007, Exchange now ships with a SOAP interface called Exchange Web Services, or EWS. This interface gives us access to the functions necessary to write clients in any programming language on any platform.

This article describes a PHP program to look up, delete and insert items in an Exchange calendar.

Overview

SOAP is an XML-based standard for web services. PHP supports SOAP in a separate module. One part of the SOAP specification is WSDL, an XML-based web service definition language which defines the data types and the functions available. The functions and data types in EWS are actually very well documented on MSDN: http://msdn.microsoft.com/en-us/library/bb204119.aspx. EWS uses the HTTPS protocol for communication, but instead of basic authentication, it uses Microsoft-specific NTLM authentication. PHP doesn’t support this protocol with SOAP but, as we shall see, we can work around this.

The script

A normal SOAP communication in PHP goes something like this:

$wsdl = "http://example.com/webservice/definition.wsdl"; $client = new SoapClient($wsdl); $request = 123; $response = $client->MyFunction($request); # Do something with the response

On an Exchange 2007 server, the WSDL file is usually located at https://exchange.example.com/EWS/Services.wsdl. To access this file, we need a username and password for a valid user on the Exhange server. However, since Exchange uses NTLM authentication, we need to make a wrapper for SoapClient. The CURL library (also found as a PHP library) supports NTLM authentication, so we’ll use this to make the wrapper:

class NTLMSoapClient extends SoapClient { function __doRequest($request, $location, $action, $version) { $headers = array( 'Method: POST', 'Connection: Keep-Alive', 'User-Agent: PHP-SOAP-CURL', 'Content-Type: text/xml; charset=utf-8', 'SOAPAction: "'.$action.'"', ); $this->__last_request_headers = $headers; $ch = curl_init($location); curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); curl_setopt($ch, CURLOPT_HTTPHEADER, $headers); curl_setopt($ch, CURLOPT_POST, true ); curl_setopt($ch, CURLOPT_POSTFIELDS, $request); curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1); curl_setopt($ch, CURLOPT_HTTPAUTH, CURLAUTH_NTLM); curl_setopt($ch, CURLOPT_USERPWD, $this->user.':'.$this->password); $response = curl_exec($ch); return $response; } function __getLastRequestHeaders() { return implode("n", $this->__last_request_headers)."n"; } }

This class overrides the doRequest function of SoapClient to use CURL to fetch the WSDL file. Depending on you PHP installation, you might need to install the PHP CURL module for this to work. Edit: If you experience SoapClient errors, you may need to disable SSL certificate validation. I haven’t found the real cause for these errors (it’s not just an expired certificate), and obviously it’s a security risk to disable validation, but it might what you need to get around the errors. Add these options to the __doRequest() method above:

curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false); curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);

Edit2: If you get a “looks like we got no XML document” SoapFault, it may be because the server is responding with a non-XML document. In my case, the response was an HTML 401 authentication error page. Printing out the $request and $response objects in the doRequest function above is a big help when debugging. I solved the auth error by deleting the line containing “CURLAUTH_NTLM”, so apparently NTLM authentication is not always used. Oh well.

 

We supply the username and password in another wrapper:

class ExchangeNTLMSoapClient extends NTLMSoapClient { protected $user = 'john.doe@example.com'; protected $password = 'secret'; }

Now we can call EWS:

$client = new ExchangeNTLMSoapClient($wsdl);

However, this will fail for two resaons. The first reason is that the WSDL file should contain a soap:address element describing where to find the location of the SOAP web service. The WSDL file served by Exchange does not contain such an element. There are possibly other ways to do this, but one solution is to download the WSDL file and add the following at the end:

<wsdl:service name="ExchangeServices"> <wsdl:port name="ExchangeServicePort" binding="tns:ExchangeServiceBinding"> <soap:address location="https://exchange.example.com/EWS/Exchange.asmx"/> </wsdl:port> </wsdl:service> </wsdl:definitions>

This tells SoapClient where to find the actual web service. This solution requires that two files referenced by the WSDL file, types.xsd and messages.xsd, are also downloaded and placed locally. This is not a problem of you’re only contacting one Exchange server, but it’s not an elegant solution if you need to contact many servers.

The other reason the call to ExchangeNTLMSoapClient will fail is that the wrapper only adds NTLM support to the initial download of the WSDL file. When SoapClient proceeds to contact the web service, it switches back to basic authentication. To work around this, we create a new stream object which uses CURL:

class NTLMStream { private $path; private $mode; private $options; private $opened_path; private $buffer; private $pos; public function stream_open($path, $mode, $options, $opened_path) { echo "[NTLMStream::stream_open] $path , mode=$mode n"; $this->path = $path; $this->mode = $mode; $this->options = $options; $this->opened_path = $opened_path; $this->createBuffer($path); return true; } public function stream_close() { echo "[NTLMStream::stream_close] n"; curl_close($this->ch); } public function stream_read($count) { echo "[NTLMStream::stream_read] $count n"; if(strlen($this->buffer) == 0) { return false; } $read = substr($this->buffer,$this->pos, $count); $this->pos += $count; return $read; } public function stream_write($data) { echo "[NTLMStream::stream_write] n"; if(strlen($this->buffer) == 0) { return false; } return true; } public function stream_eof() { echo "[NTLMStream::stream_eof] "; if($this->pos > strlen($this->buffer)) { echo "true n"; return true; } echo "false n"; return false; } /* return the position of the current read pointer */ public function stream_tell() { echo "[NTLMStream::stream_tell] n"; return $this->pos; } public function stream_flush() { echo "[NTLMStream::stream_flush] n"; $this->buffer = null; $this->pos = null; } public function stream_stat() { echo "[NTLMStream::stream_stat] n"; $this->createBuffer($this->path); $stat = array( 'size' => strlen($this->buffer), ); return $stat; } public function url_stat($path, $flags) { echo "[NTLMStream::url_stat] n"; $this->createBuffer($path); $stat = array( 'size' => strlen($this->buffer), ); return $stat; } /* Create the buffer by requesting the url through cURL */ private function createBuffer($path) { if($this->buffer) { return; } echo "[NTLMStream::createBuffer] create buffer from : $pathn"; $this->ch = curl_init($path); curl_setopt($this->ch, CURLOPT_RETURNTRANSFER, true); curl_setopt($this->ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1); curl_setopt($this->ch, CURLOPT_HTTPAUTH, CURLAUTH_NTLM); curl_setopt($this->ch, CURLOPT_USERPWD, $this->user.':'.$this->password); echo $this->buffer = curl_exec($this->ch); echo "[NTLMStream::createBuffer] buffer size : ".strlen($this->buffer)."bytesn"; $this->pos = 0; } }

… and a second wrapper over this stream to supply the password for NTLMStream:

class ExchangeNTLMStream extends NTLMStream { protected $user = 'john.doe@example.com'; protected $password = 'secret'; }

Now we need to tell PHP to use this stream instead while calling the web service:

stream_wrapper_unregister('https'); stream_wrapper_register('https', 'ExchangeNTLMStream') or die("Failed to register protocol"); $wsdl = "/usr/local/www/Services.wsdl"; $client = new ExchangeNTLMSoapClient($wsdl); /* Do something with the web service connection */ stream_wrapper_restore('https');

Now we have a working communication with EWS. Let’s do something with it:

print_r($client->__getFunctions());

This lists the available functions. Let’s use the FindItem function. It fetches all items in a specific folder on the Exchange server. But how do we compose a request? Looking at the list of functions, we se that they define the data types of the argument and the return value. EWS data types are fairly detailed and complex, and there are more than 400 data types. Let’s look up what these data types look like:

print_r($client->__getTypes());

This describes the individual data types in a general C-like syntax.

Let’s create a request. The MSDN documentation is helpful to determine required fields and their possible values. First, we’ll list the folders in the top level of the account:

$FindFolder->Traversal = "Shallow"; $FindFolder->FolderShape->BaseShape = "Default"; $FindFolder->ParentFolderIds->DistinguishedFolderId->Id = "root"; $result = $client->FindFolder($FindFolder); $folders = $result->ResponseMessages->FindFolderResponseMessage->RootFolder->Folders->Folder; foreach($folders as $folder) { echo $folder->DisplayName."n"; }

Now, let’s find all items in the calendar:

$FindItem->Traversal = "Shallow"; $FindItem->ItemShape->BaseShape = "AllProperties"; $FindItem->ParentFolderIds->DistinguishedFolderId->Id = "calendar"; $FindItem->CalendarView->StartDate = "2008-12-01T00:00:00Z"; $FindItem->CalendarView->EndDate = "2008-12-31T00:00:00Z"; $result = $client->FindItem($FindItem); $calendaritems = $result->ResponseMessages->FindItemResponseMessage->RootFolder->Items->CalendarItem; foreach($calendaritems as $item) { echo $item->Subject."n"; }

This gets us a list of all John Doe’s calendar items for december 2008. Now let’s delete all items on this list. For this, we need Id and a ChangeKey for all items:

$ids = array(); $changeKeys = array(); foreach($calendaritems as $item) { $ids[] = $item->ItemId->Id; $changeKeys[] = $item->ItemId->ChangeKey; } if(sizeof($ids) > 0) { $DeleteItem->DeleteType = "HardDelete"; $DeleteItem->SendMeetingCancellations = "SendToNone"; $DeleteItem->ItemIds->ItemId = array(); for($i = 0; $i < sizeof($ids); $i++ ) { $DeleteItem->ItemIds->ItemId[$i]->Id = $ids[$i]; $DeleteItem->ItemIds->ItemId[$i]->ChangeKey = $changeKeys[$i]; } $result = $client->DeleteItem($DeleteItem); print_r($result); }

And finally, let’s create a new item in the calendar:

$CreateItem->SendMeetingInvitations = "SendToNone"; $CreateItem->SavedItemFolderId->DistinguishedFolderId->Id = "calendar"; $CreateItem->Items->CalendarItem = array(); for($i = 0; $i < 1; $i++) { $CreateItem->Items->CalendarItem[$i]->Subject = "Hello from PHP"; $CreateItem->Items->CalendarItem[$i]->Start = "2010-01-01T16:00:00Z"; # ISO date format. Z denotes UTC time $CreateItem->Items->CalendarItem[$i]->End = "2010-01-01T17:00:00Z"; $CreateItem->Items->CalendarItem[$i]->IsAllDayEvent = false; $CreateItem->Items->CalendarItem[$i]->LegacyFreeBusyStatus = "Busy"; $CreateItem->Items->CalendarItem[$i]->Location = "Bahamas"; $CreateItem->Items->CalendarItem[$i]->Categories->String = "MyCategory"; } $result = $client->CreateItem($CreateItem); print_r($result);

There are many other functions available and many other attributes for the objects I have used in this tutorial.

Advanced

If you need to extend the classes defined in the WSDL with e.g. a function, it is possible to do this using the NTLMSoapClient class. Add a constructor to the class which registers the WSDL classes as PHP classes:

function __construct($wsdl, $options = null) { $client = new NTLMSoapClient($wsdl, $options); $types = array(); foreach($client->__getTypes() as $type) { # Match the type information using a regular expession preg_match("/([a-z0-9_]+)s+([a-z0-9_]+([])?)(.*)?/si", $type, $matches); $qualifier = $matches[1]; $name = $matches[2]; if($qualifier == "struct") { # Store the data type information in an array for later use in the classmap $types[$name] = $name; # Check that the class does not exsit before creating it. We only need to create empty classes. if (! class_exists($name)) { eval("class $name {}"); } else { echo "[ExchangeNTLMSoapClient::__construct] Class $name already exists.n"; } } } # Add the classmap to the options array and call the parent constructor if(is_null($options)) { $options = array(); } $options['classmap'] = $types; parent::__construct($wsdl, $options); }

This loads empty class definitions for classes not already defined in the PHP script. Now it’s possible to define a class that overrides the one automatically loaded:

class EmailAddressDictionaryEntryType { function validate() { # Lame email validator return stristr("@", $this->Value); } }

Finally

That’s all. There’s still a long way from this sample script to an Outlook replacement, but this can be very useful for e.g. integration purposes and data migration.

Thanks to Thomas Rabaix for his article on NTLM authentication in SOAP and PHP: http://rabaix.net/en/articles/2008/03/13/using-soap-php-with-ntlm-authentication. Thanks to Adam Delves for his article on WSDL and PHP: http://www.phpbuilder.com/columns/adam_delves20060606.php3.

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