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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 Set args = CreateObject("Scripting.Dictionary")
95 args.Add "hostname", "localhost"
96 args.Add "auth_service", ""
97 args.Add "key_dir", "C:/Ucam_Webauth/certificates"
99 'args' is an associative array of *text* strings so parameter values must
100 be converted into strings, ie. numbers and booleans must be supplied within
101 quotes as in "23", "TRUE", "FALSE".
102 A full list of allowed parameters is provided at the end of this README.
104 4. Create an instance of the 'Ucam_Webauth' class from within your ASP
105 server page and initialize with setup variables:
107 Set oUcam_Webauth = New Ucam_Webauth
108 Call oUcam_Webauth(args)
110 5. Call 'Authenticate()' on the Ucam_Webauth object and act according to
111 the value returned:
113 Select Case oUcam_Webauth.Authenticate()
117 ...
118 Exit Sub
122 ...
126 ...
130 ...
132 End Select
134 The four possible return values of 'Authenticate()' are:
136 - AUTHENTICATE_INCOMPLETE : The authentication process has yet to complete.
137 The user may have been redirected to the Raven server and has yet to enter
138 their login details.
139 - AUTHENTICATE_COMPLETE_AUTHENTICATED : The authentication process completed
140 and the user has been successfully authenticated.
141 - AUTHENTICATE_COMPLETE_NOT_AUTHENTICATED : The authentication process
142 completed and the user was not successfully authenticated.
143 The user may have clicked 'Cancel' at the Raven server.
144 - AUTHENTICATE_COMPLETE_ERROR : There was an error during the authentication
145 process forcing the authentication cycle to terminate early.
147 As the 'Authenticate()' function may need to send HTTP headers, it must be
148 called before any output (e.g. HTML, HTTP headers) is sent to the browser.
150 The 'Default.asp' file provided is a sample of a simple server page using
151 the 'Ucam_Webauth' VBScript class.
153 Overview of Raven process
154 -------------------------
155 A diagram of the Raven authentication process is located within the 'docs'
156 folder as [I - Overview of Raven Authentication Process.pdf].
158 The authentication cycle consists of the following key stages:
160 #### User first tries to access authenticated page
161 User tries to load an authenticated page on a particular website.
162 The 'Ucam_Webauth' class is loaded and the 'Authenticate()' function is called.
163 If no authentication cookie is found to indicate the user is authenticated,
164 the user's browser is redirected to a separate Raven server using a special
165 'Authentication Request'. The authentication request consists of a series of
166 authentication parameters encoded into the URL redirect as name/value pairs.
168 #### User is prompted for login information
169 The Raven server interprets the authentication request sent by the main
170 website and prompts the user for their username and password. The user may
171 then be successfully authenticated or may decide to click 'Cancel'. They are
172 redirected back to the main website with a series of 'Authentication Response'
173 parameters encoded into a 'WLS-Response' GET variable.
175 #### User redirected back to main webserver
176 The user's original page is loaded again and 'Authenticate()' is called a
177 second time. 'Ucam_Webauth' processes the new 'WLS-Response' GET value and,
178 if it's valid, sets an authentication cookie on the user's browser. The
179 user's original page is then loaded again.
181 #### User redirected back to main webserver again
182 With an authentication cookie now set, 'Authenticate()' checks the status
183 code contained in the value of the authentication cookie and returns either
186 'AUTHENTICATE_COMPLETE_AUTHENTICATED' is returned , the original page can
187 go on to display authenticated content to the user.
189 Specifics of module
190 -------------------
191 The 'Authenticate()' function is the overarching authentication function of
192 'Ucam_Webauth'. It performs some basic sanity checks using 'CheckSetup()'
193 then uses 'GetCurrentState()' to establish the current state of the
194 authentication process before branching accordingly. The possible return
195 values of 'GetCurrentState()' are:
198 A completely fresh authentication. 'SendAuthenticationRequest()' [*1*] is
199 then triggered which performs some basic data checks, sets the authentication
200 cookie to 'AUTHENTICATIONCOOKIE_REDIRECT_WLS' (to record where we are in the
201 authentication process) and redirects the user's browser to the Raven
202 authentication server with a series of authentication parameters
203 encoded as name/value pairs.
206 The Raven authentication server has processed the user and has returned the
207 user's browser back to the original website with a series of authentication
208 response parameters encoded into the 'WLS-Response' GET variable.
209 'ProcessAuthenticationResponse()' [*2*] is then called which checks the
210 validity of the 'WLS-Response' value, sets an authentication cookie and
211 redirects the user back to the original page.
214 A valid authentication cookie has been set
216 'ProcessAuthenticationCookie()' [*3*] is then called which checks the
217 validity of the cookie. If the cookie has expired,
218 'SendAuthenticationRequest()' is called again in case the user needs to
219 reauthenticate themselves. If the cookie is still valid, an
220 'AUTHENTICATE_COMPLETE_XXX' value is returned, indicating that the
221 authentication cycle has completed successfully.
222 NOTE: this may be true if the user has cancelled the authentication process,
223 in which case 'AUTHENTICATE_COMPLETE_NOT_AUTHENTICATED' will be returned.
225 #### STATE_ERROR
226 An error occurred, breaking the authentication cycle and returning
227 AUTHENTICATE_COMPLETE_ERROR to 'Authenticate()'. This return value will
228 also be generated by the other functions above if they generate an error.
230 ## Accompanying diagrams
231 Detailed diagrams of the Raven process flow for (i) a successful
232 authentication (ii) a cancelled authentication, are located in the 'docs'
233 folder as [II - Ucam_Webauth - Flowchart for Valid Authentication.pdf] and
234 [III - Ucam_Webauth - Flowchart for Cancelled Authentication.pdf], respectively.
236 The numbers on these diagrams correspond to the three key secondary functions
237 described above:
238 - *1*. SendAuthenticationRequest()
239 - *2*. ProcessAuthenticationResponse()
240 - *3*. ProcessAuthenticationCookie()
242 Other important functions include:
244 ### ResetState()
245 Attempts to reset state as if a new user has just loaded a fresh browser
246 window. This is typically used when a user has experienced an error and we
247 want to give them a fresh opportunity to try again.
249 ### check_signature(...)
250 Checks the signature provided by the Raven server, when it signed the
251 'WLS-Response' variable, is a valid signature for the data. This ensures the
252 data has not been tampered with.
254 ### hmac_sha1(...)
255 Creates a hash value for signing the local authentication cookie.
257 ### wls_encode/decode(...)
258 Encoding/decoding functions to allow base64 signatures to be sent within URLs.
260 Possible arguments to 'Ucam_Webauth'
261 ------------------------------------
262 (Based on documentation for PHP Raven authentication module)
264 - log_file :
265 The location for a log file that will record progress and track possible
266 errors. The folder containing the file must be read/writable by the webserver.
267 Default: log.txt
269 - response_timeout :
270 Responses from the central authentication server are time-stamped.
271 This parameter sets the period of time in seconds during which these
272 responses are considered valid.
273 Default: 30 seconds.
275 - key_dir :
276 The name of the directory containing the public key certificate(s) required
277 to validate the authentication responses sent by the server.
278 Default: '/etc/httpd/conf/webauth_keys'.
280 - max_session_life :
281 The maximum period of time in seconds for which an established session will
282 be valid. This may be overriden if the authentication reply contains a
283 shorter 'life' parameter. Note that this does NOT define an expiry time for
284 the session cookie. Session cookies are always set without an expiry time,
285 causing them to expire when the browser session finishes.
286 Default: 7200 (2 hours).
288 - timeout_message :
289 A re-authentication by the authentication service will be triggered when an
290 established session expires. This option sets a text string which is sent to
291 the authentication server to explain to the user why they are being asked to
292 authenticate again. HTML markup is suppressed as for the description
293 parameter described below.
294 Default: 'your login to the site has expired'.
296 - hostname (required) :
297 The fully-qualified TCP/IP hostname that should be used in request URLs
298 referencing the Ucam_Webauth-enabled application. This *must* be set, as it
299 is needed for multiple reasons - primarily security but also to avoid varying
300 hostnames in URLs leading to failed or inconsistent authentication.
301 No default.
303 - cookie_key (required):
304 A random key used to protect session cookies from tampering. Any reasonably
305 unpredictable string (for example the MD5 checksum of a rapidly changing
306 logfile) will be satisfactory. This key must be the same for all uses of the
307 web authentication system that will receive the same session cookies (see the
308 cookie_name, cookie_path and cookie_domain parameters below).
309 No default.
311 - cookie_name :
312 The name used for the session cookie.
313 When used for access to resources over HTTPS the string '-S' is appended to
314 this name.
315 Default: 'Ucam-Webauth-Session'.
317 - cookie_path :
318 The 'Path' attribute for the session cookie. The default is the directory
319 component of the path to the script currently being executed. This should
320 result in the cookie being returned for future requests for this script and
321 for the other resources in the same 'directory'; see the important
322 information about the cookie_key parameter above.
323 Default: '/'.
325 - cookie_domain :
326 The 'Domain' attribute for the session cookie. By default the 'Domain'
327 attribute is omitted when setting the cookie. This should result in the
328 cookie being returned only to the server running the script. Be aware that
329 some people may treat with suspicion cookies with domain attributes that are
330 wider than the host setting the cookie.
331 No default.
333 - auth_service : The full URL for the web login service to be used.
334 Default: ''
336 #### Authentication request properties
337 The following setup parameters prefixed with 'authrequest_' relate to
338 properties that will be sent to the authentication server as part of an
339 authentication request:
341 - authrequest_desc : A text description of the resource that is requesting
342 authentication. This may be displayed to the user by the authentication
343 service. It is restricted to printable ASCII characters (0x20 - 0x7e) though
344 it may contain HTML entities representing other characters. The characters
345 '<' and '>' will be converted into HTML entities before being sent to the
346 browser and so this text cannot usefully contain HTML markup.
347 No default.
349 - authrequest_params : Data that will be returned unaltered to the WAA in
350 any 'authentication response message' issued as a result of this request.
351 This could be used to carry the identity of the resource originally requested
352 or other WAA state, or to associate authentication requests with their
353 eventual replies. When returned, this data will be protected by the digital
354 signature applied to the authentication response message but nothing else is
355 done to ensure the integrity or confidentiality of this data - the WAA MUST
356 take responsibility for this if necessary.
357 No default.
359 - authrequest_skew : Interpretation of response_timeout is difficult if the
360 clocks on the server running the PHP agent and on the authentication server
361 are out of step. Both servers should use NTP to synchronize their clocks,
362 but if they don't then this parameter should be set to an estimate of the
363 maximum expected difference between them (in seconds).
364 Default: 0.
366 - authrequest_fail :
367 If TRUE, sets the fail parameter in any authentication request sent to the
368 authentication server to 'yes'. This has the effect of requiring the
369 authentication server itself to report any errors that it encounters, rather
370 than returning an error indication. Note however that even with this parameter
371 set errors may be detected by this module that will result in authentication
372 failing here.
373 Default: FALSE.
375 - authrequest_iact :
376 If TRUE, then the 'iact' parameter provided to the authentication server is
377 set to 'yes'. If FALSE, then the 'iact' parameter is set to 'no'. If no value
378 is provided for 'authrequest_iact', the 'iact' parameter is left blank.
379 The value 'yes' for 'iact' requires that a re-authentication exchange takes
380 place with the user. This could be used prior to a sensitive transaction in
381 an attempt to ensure that a previously authenticated user is still present
382 at the browser. The value 'no' requires that the authentication request will
383 only succeed if the user's identity can be returned without interacting with
384 the user. This could be used as an optimisation to take advantage of any
385 existing authentication but without actively soliciting one. If omitted or
386 empty, then a previously established identity may be returned if the WLS
387 supports doing so, and if not then the user will be prompted as necessary.
388 Default: omitted.