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1 University of Cambridge Classic ASP/VBScript Raven Authentication Module - v.1.0 (29/04/2014)
2 ==========================================================================
4 Description
5 -----------
6 This software comprises a VBScript class 'Ucam_Webauth' and sample
7 files that provide a Classic ASP/VBScript implementation of a 'Raven'
8 authentication module; Raven is the web authentication protocol used
9 by the University of Cambridge, UK. The logic and code of the
10 'Ucam_Webauth' class are loosely based on the PHP Raven authentication
11 class provided at
12 - For a full description of the latest Raven specification and an explanation
13 of how Raven works, go to
14 - This software was originally created for the Careers Service,
15 University of Cambridge by For support, please
16 contact
18 Files and folders
19 -----------------
20 - [certificates]: Temporary location for Raven public key certificates.
21 - [js]: Folder containing Javascript cryptography libraries.
22 - [docs]: Supporting documentation.
23 - [logs]: Possible location for log files created by the module.
24 - Default.asp: A sample file showing how the 'Ucam_Webauth' class is used
25 to provide Raven authentication.
26 - Test.asp: A test file for unit testing the 'Ucam_Webauth' module using the
27 'Ucam_RavenWLS' dummy Raven server (separate project, not included).
28 - Ucam_Webauth.vbs: The main 'Ucam_Webauth' VBScript class.
30 Platform requirements
31 ---------------------
32 This module has been tested on IIS7 with .NET Framework set to
33 'No managed code', ie. classic ASP.
35 Installation
36 ------------
37 ### Cryptographic functions
38 Cryptographic functions are provided by the Javascript libraries within the
39 'js' folder. These libraries are versions of the client-side Javascript
40 libraries provided at
41 but modified to run server-side. There is no need to install any
42 additional cryptography libraries.
44 ### Install Raven certificates
45 The authentication module uses the Raven public key certificate at
46 to verify authentication responses.
47 Download the certificate from and copy
48 to the 'certificates' folder provided with this authentication module
49 download - the 'certificates' folder is a temporary location for the
50 certificate while you get the module up and running. You will need to supply
51 the full path to the 'certificates' folder as either a 'key_dir' argument
52 to the 'Ucam_Webauth' constructor or by modifying the 'Ucam_Webauth'
53 variable 'DEFAULT_KEY_DIR' directly.
55 Once you have everything working, move the 'certificates' folder
56 to a new location on your webserver that is not web- or publicly-accessible
57 and modify the 'key_dir' string accordingly.
59 - NOTE: you may have to change the name of the key file from 'pubkey2.crt'
60 to '2.crt'.
62 If you're using the Raven test server
63 ( for testing purposes, make sure
64 you install the test server keys instead, but ensure you remove these keys
65 before using the authentication module in a production environment, as
66 recommended by the demo Raven server:
68 > It is vital to keep these demo keys seperate from keys
69 > used with a production service - failure to do so could
70 > allow an attacker to successfully replay a response
71 > from the demonstration server, which anyone can easily
72 > obtain, against a production service.
74 Getting started
75 ---------------
77 The 'Ucam_Webauth' VBScript class must be used within an ASP server-side page
78 as it interacts directly with a user's browser session. To use the
79 'Ucam_Webauth' VBScript class:
81 - 1. Ensure the 'Ucam_Webauth.vbs' class file and the folder 'js' are in the
82 same directory as your ASP script. The folders 'certificates' and 'logs' may
83 also be located here temporarily.
84 - 2. Include the 'Ucam_Webauth.vbs' class file in the 'head' of your ASP file:
87 <head>
88 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
89 <!--#include file="Ucam_Webauth.vbs"-->
90 </head>
92 - 3. Set up the initial arguments for the 'Ucam_Webauth' class:
94 ```
95 Set args = CreateObject("Scripting.Dictionary")
96 args.Add "hostname", "localhost"
97 args.Add "auth_service", ""
98 args.Add "key_dir", "C:/Ucam_Webauth/certificates"
99 ```
101 'args' is an associative array of *text* strings so parameter values must
102 be converted into strings, ie. numbers and booleans must be supplied within
103 quotes as in "23", "TRUE", "FALSE".
104 A full list of allowed parameters is provided at the end of this README.
106 - 4. Create an instance of the 'Ucam_Webauth' class from within your ASP
107 server page and initialize with setup variables:
109 ```
110 Set oUcam_Webauth = New Ucam_Webauth
111 Call oUcam_Webauth(args)
112 ```
114 - 5. Call 'Authenticate()' on the Ucam_Webauth object and act according to
115 the value returned:
117 ```
118 Select Case oUcam_Webauth.Authenticate()
122 ...
123 Exit Sub
127 ...
131 ...
135 ...
137 End Select
138 ```
140 The four possible return values of 'Authenticate()' are:
142 - AUTHENTICATE_INCOMPLETE : The authentication process has yet to complete.
143 The user may have been redirected to the Raven server and has yet to enter
144 their login details.
145 - AUTHENTICATE_COMPLETE_AUTHENTICATED : The authentication process completed
146 and the user has been successfully authenticated.
147 - AUTHENTICATE_COMPLETE_NOT_AUTHENTICATED : The authentication process
148 completed and the user was not successfully authenticated.
149 The user may have clicked 'Cancel' at the Raven server.
150 - AUTHENTICATE_COMPLETE_ERROR : There was an error during the authentication
151 process forcing the authentication cycle to terminate early.
153 As the 'Authenticate()' function may need to send HTTP headers, it must be
154 called before any output (e.g. HTML, HTTP headers) is sent to the browser.
156 The 'Default.asp' file provided is a sample of a simple server page using
157 the 'Ucam_Webauth' VBScript class.
159 Overview of Raven process
160 -------------------------
161 A diagram of the Raven authentication process is located within the 'docs'
162 folder as [I - Overview of Raven Authentication Process.pdf].
164 The authentication cycle consists of the following key stages:
166 #### User first tries to access authenticated page
167 User tries to load an authenticated page on a particular website.
168 The 'Ucam_Webauth' class is loaded and the 'Authenticate()' function is called.
169 If no authentication cookie is found to indicate the user is authenticated,
170 the user's browser is redirected to a separate Raven server using a special
171 'Authentication Request'. The authentication request consists of a series of
172 authentication parameters encoded into the URL redirect as name/value pairs.
174 #### User is prompted for login information
175 The Raven server interprets the authentication request sent by the main
176 website and prompts the user for their username and password. The user may
177 then be successfully authenticated or may decide to click 'Cancel'. They are
178 redirected back to the main website with a series of 'Authentication Response'
179 parameters encoded into a 'WLS-Response' GET variable.
181 #### User redirected back to main webserver
182 The user's original page is loaded again and 'Authenticate()' is called a
183 second time. 'Ucam_Webauth' processes the new 'WLS-Response' GET value and,
184 if it's valid, sets an authentication cookie on the user's browser. The
185 user's original page is then loaded again.
187 #### User redirected back to main webserver again
188 With an authentication cookie now set, 'Authenticate()' checks the status
189 code contained in the value of the authentication cookie and returns either
192 'AUTHENTICATE_COMPLETE_AUTHENTICATED' is returned , the original page can
193 go on to display authenticated content to the user.
195 Specifics of module
196 -------------------
197 The 'Authenticate()' function is the overarching authentication function of
198 'Ucam_Webauth'. It performs some basic sanity checks using 'CheckSetup()'
199 then uses 'GetCurrentState()' to establish the current state of the
200 authentication process before branching accordingly. The possible return
201 values of 'GetCurrentState()' are:
204 A completely fresh authentication. 'SendAuthenticationRequest()' [*1*] is
205 then triggered which performs some basic data checks, sets the authentication
206 cookie to 'AUTHENTICATIONCOOKIE_REDIRECT_WLS' (to record where we are in the
207 authentication process) and redirects the user's browser to the Raven
208 authentication server with a series of authentication parameters
209 encoded as name/value pairs.
212 The Raven authentication server has processed the user and has returned the
213 user's browser back to the original website with a series of authentication
214 response parameters encoded into the 'WLS-Response' GET variable.
215 'ProcessAuthenticationResponse()' [*2*] is then called which checks the
216 validity of the 'WLS-Response' value, sets an authentication cookie and
217 redirects the user back to the original page.
220 A valid authentication cookie has been set
222 'ProcessAuthenticationCookie()' [*3*] is then called which checks the
223 validity of the cookie. If the cookie has expired,
224 'SendAuthenticationRequest()' is called again in case the user needs to
225 reauthenticate themselves. If the cookie is still valid, an
226 'AUTHENTICATE_COMPLETE_XXX' value is returned, indicating that the
227 authentication cycle has completed successfully.
228 NOTE: this may be true if the user has cancelled the authentication process,
229 in which case 'AUTHENTICATE_COMPLETE_NOT_AUTHENTICATED' will be returned.
231 #### STATE_ERROR
232 An error occurred, breaking the authentication cycle and returning
233 AUTHENTICATE_COMPLETE_ERROR to 'Authenticate()'. This return value will
234 also be generated by the other functions above if they generate an error.
236 ## Accompanying diagrams
237 Detailed diagrams of the Raven process flow for (i) a successful
238 authentication (ii) a cancelled authentication, are located in the 'docs'
239 folder as [II - Ucam_Webauth - Flowchart for Valid Authentication.pdf] and
240 [III - Ucam_Webauth - Flowchart for Cancelled Authentication.pdf], respectively.
242 The numbers on these diagrams correspond to the three key secondary functions
243 described above:
244 - *1*. SendAuthenticationRequest()
245 - *2*. ProcessAuthenticationResponse()
246 - *3*. ProcessAuthenticationCookie()
248 Other important functions include:
250 ### ResetState()
251 Attempts to reset state as if a new user has just loaded a fresh browser
252 window. This is typically used when a user has experienced an error and we
253 want to give them a fresh opportunity to try again.
255 ### check_signature(...)
256 Checks the signature provided by the Raven server, when it signed the
257 'WLS-Response' variable, is a valid signature for the data. This ensures the
258 data has not been tampered with.
260 ### hmac_sha1(...)
261 Creates a hash value for signing the local authentication cookie.
263 ### wls_encode/decode(...)
264 Encoding/decoding functions to allow base64 signatures to be sent within URLs.
266 Possible arguments to 'Ucam_Webauth'
267 ------------------------------------
268 (Based on documentation for PHP Raven authentication module)
270 - log_file :
271 The location for a log file that will record progress and track possible
272 errors. The folder containing the file must be read/writable by the webserver.
273 Default: log.txt
275 - response_timeout :
276 Responses from the central authentication server are time-stamped.
277 This parameter sets the period of time in seconds during which these
278 responses are considered valid.
279 Default: 30 seconds.
281 - key_dir :
282 The name of the directory containing the public key certificate(s) required
283 to validate the authentication responses sent by the server.
284 Default: '/etc/httpd/conf/webauth_keys'.
286 - max_session_life :
287 The maximum period of time in seconds for which an established session will
288 be valid. This may be overriden if the authentication reply contains a
289 shorter 'life' parameter. Note that this does NOT define an expiry time for
290 the session cookie. Session cookies are always set without an expiry time,
291 causing them to expire when the browser session finishes.
292 Default: 7200 (2 hours).
294 - timeout_message :
295 A re-authentication by the authentication service will be triggered when an
296 established session expires. This option sets a text string which is sent to
297 the authentication server to explain to the user why they are being asked to
298 authenticate again. HTML markup is suppressed as for the description
299 parameter described below.
300 Default: 'your login to the site has expired'.
302 - hostname (required) :
303 The fully-qualified TCP/IP hostname that should be used in request URLs
304 referencing the Ucam_Webauth-enabled application. This *must* be set, as it
305 is needed for multiple reasons - primarily security but also to avoid varying
306 hostnames in URLs leading to failed or inconsistent authentication.
307 No default.
309 - cookie_key (required):
310 A random key used to protect session cookies from tampering. Any reasonably
311 unpredictable string (for example the MD5 checksum of a rapidly changing
312 logfile) will be satisfactory. This key must be the same for all uses of the
313 web authentication system that will receive the same session cookies (see the
314 cookie_name, cookie_path and cookie_domain parameters below).
315 No default.
317 - cookie_name :
318 The name used for the session cookie.
319 When used for access to resources over HTTPS the string '-S' is appended to
320 this name.
321 Default: 'Ucam-Webauth-Session'.
323 - cookie_path :
324 The 'Path' attribute for the session cookie. The default is the directory
325 component of the path to the script currently being executed. This should
326 result in the cookie being returned for future requests for this script and
327 for the other resources in the same 'directory'; see the important
328 information about the cookie_key parameter above.
329 Default: '/'.
331 - cookie_domain :
332 The 'Domain' attribute for the session cookie. By default the 'Domain'
333 attribute is omitted when setting the cookie. This should result in the
334 cookie being returned only to the server running the script. Be aware that
335 some people may treat with suspicion cookies with domain attributes that are
336 wider than the host setting the cookie.
337 No default.
339 - auth_service : The full URL for the web login service to be used.
340 Default: ''
342 #### Authentication request properties
343 The following setup parameters prefixed with 'authrequest_' relate to
344 properties that will be sent to the authentication server as part of an
345 authentication request:
347 - authrequest_desc : A text description of the resource that is requesting
348 authentication. This may be displayed to the user by the authentication
349 service. It is restricted to printable ASCII characters (0x20 - 0x7e) though
350 it may contain HTML entities representing other characters. The characters
351 '<' and '>' will be converted into HTML entities before being sent to the
352 browser and so this text cannot usefully contain HTML markup.
353 No default.
355 - authrequest_params : Data that will be returned unaltered to the WAA in
356 any 'authentication response message' issued as a result of this request.
357 This could be used to carry the identity of the resource originally requested
358 or other WAA state, or to associate authentication requests with their
359 eventual replies. When returned, this data will be protected by the digital
360 signature applied to the authentication response message but nothing else is
361 done to ensure the integrity or confidentiality of this data - the WAA MUST
362 take responsibility for this if necessary.
363 No default.
365 - authrequest_skew : Interpretation of response_timeout is difficult if the
366 clocks on the server running the PHP agent and on the authentication server
367 are out of step. Both servers should use NTP to synchronize their clocks,
368 but if they don't then this parameter should be set to an estimate of the
369 maximum expected difference between them (in seconds).
370 Default: 0.
372 - authrequest_fail :
373 If TRUE, sets the fail parameter in any authentication request sent to the
374 authentication server to 'yes'. This has the effect of requiring the
375 authentication server itself to report any errors that it encounters, rather
376 than returning an error indication. Note however that even with this parameter
377 set errors may be detected by this module that will result in authentication
378 failing here.
379 Default: FALSE.
381 - authrequest_iact :
382 If TRUE, then the 'iact' parameter provided to the authentication server is
383 set to 'yes'. If FALSE, then the 'iact' parameter is set to 'no'. If no value
384 is provided for 'authrequest_iact', the 'iact' parameter is left blank.
385 The value 'yes' for 'iact' requires that a re-authentication exchange takes
386 place with the user. This could be used prior to a sensitive transaction in
387 an attempt to ensure that a previously authenticated user is still present
388 at the browser. The value 'no' requires that the authentication request will
389 only succeed if the user's identity can be returned without interacting with
390 the user. This could be used as an optimisation to take advantage of any
391 existing authentication but without actively soliciting one. If omitted or
392 empty, then a previously established identity may be returned if the WLS
393 supports doing so, and if not then the user will be prompted as necessary.
394 Default: omitted.