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1´╗┐University of Cambridge Classic ASP/VBScript Raven Authentication Module - v.1.0 (29/04/2014)\r
6The software comprises a VBScript class 'Ucam_Webauth' and sample files that \r
7provide a Classic ASP/VBScript implementation of a 'Raven' authentication \r
8module; Raven is the web authentication protocol used by the University of \r
9Cambridge, UK. The logic and code of the 'Ucam_Webauth' class are loosely \r
10based on the PHP Raven authentication class provided at \r
11 \r
12- For a full description of the latest Raven specification and an explanation \r
13of how Raven works, go to\r
14- This software was originally created for the Careers Service,\r
15University of Cambridge by For support, please\r
18Files and folders\r
20- [certificates]: Temporary location for Raven public key certificates.\r
21- [js]: Folder containing Javascript cryptography libraries.\r
22- [docs]: Supporting documentation.\r
23- [logs]: Possible location for log files created by the module.\r
24- Default.asp: A sample file showing how the 'Ucam_Webauth' class is used \r
25to provide Raven authentication.\r
26- Test.asp: A test file for unit testing the 'Ucam_Webauth' module using the \r
27'Ucam_RavenWLS' dummy Raven server (separate project, not included).\r
28- Ucam_Webauth.vbs: The main 'Ucam_Webauth' VBScript class.\r
30Platform requirements\r
32This module has been tested on IIS7 with .NET Framework set to \r
33'No managed code', ie. classic ASP.\r
37### Cryptographic functions\r
38Cryptographic functions are provided by the Javascript libraries within the \r
39'js' folder. These libraries are versions of the client-side Javascript \r
40libraries provided at \r
41but modified to run server-side. There is no need to install any \r
42additional cryptography libraries.\r
44### Install Raven certificates\r
45The authentication module uses the Raven public key certificate at \r
46 to verify authentication responses. \r
47Download the certificate from and copy \r
48to the 'certificates' folder provided with this authentication module \r
49download - the 'certificates' folder is a temporary location for the \r
50certificate while you get the module up and running. You will need to supply \r
51the full path to the 'certificates' folder as either a 'key_dir' argument \r
52to the 'Ucam_Webauth' constructor or by modifying the 'Ucam_Webauth' \r
53variable 'DEFAULT_KEY_DIR' directly. \r
55Once you have everything working, move the 'certificates' folder \r
56to a new location on your webserver that is not web- or publicly-accessible \r
57and modify the 'key_dir' string accordingly.\r
58 \r
59- NOTE: you may have to change the name of the key file from 'pubkey2.crt' \r
60to '2.crt'. \r
62If you're using the Raven test server \r
63( for testing purposes, make sure \r
64you install the test server keys instead, but ensure you remove these keys \r
65before using the authentication module in a production environment, as \r
66recommended by the demo Raven server:\r
67>> It is vital to keep these demo keys seperate from keys \r
68>> used with a production service - failure to do so could \r
69>> allow an attacker to successfully replay a response \r
70>> from the demonstration server, which anyone can easily \r
71>> obtain, against a production service. \r
74Getting started\r
77The 'Ucam_Webauth' VBScript class must be used within an ASP server-side page \r
78as it interacts directly with a user's browser session. To use the \r
79'Ucam_Webauth' VBScript class:\r
81- 1. Ensure the 'Ucam_Webauth.vbs' class file and the folder 'js' are in the \r
82same directory as your ASP script. The folders 'certificates' and 'logs' may \r
83also be located here temporarily. \r
84- 2. Include the 'Ucam_Webauth.vbs' class file in the 'head' of your ASP file:\r
88<meta http-equiv="Content-Type" content="text/html; charset=utf-8">\r
89<!--#include file="Ucam_Webauth.vbs"-->\r
94- 3. Set up the initial arguments for the 'Ucam_Webauth' class:\r
97Set args = CreateObject("Scripting.Dictionary")\r
98args.Add "hostname", "localhost"\r
99args.Add "auth_service", ""\r
100args.Add "key_dir", "C:/Ucam_Webauth/certificates"\r
103'args' is an associative array of *text* strings so parameter values must \r
104be converted into strings, ie. numbers and booleans must be supplied within \r
105quotes as in "23", "TRUE", "FALSE".\r
106A full list of allowed parameters is provided at the end of this README. \r
108- 4. Create an instance of the 'Ucam_Webauth' class from within your ASP \r
109server page and initialize with setup variables:\r
112Set oUcam_Webauth = New Ucam_Webauth\r
113Call oUcam_Webauth(args) \r
115 \r
116- 5. Call 'Authenticate()' on the Ucam_Webauth object and act according to \r
117the value returned:\r
120 Select Case oUcam_Webauth.Authenticate()\r
121 \r
124 ... \r
125 Exit Sub\r
129 ...\r
130 \r
133 ...\r
137 ...\r
138 \r
139 End Select\r
142The four possible return values of 'Authenticate()' are:\r
144- AUTHENTICATE_INCOMPLETE : The authentication process has yet to complete. \r
145The user may have been redirected to the Raven server and has yet to enter \r
146their login details.\r
147- AUTHENTICATE_COMPLETE_AUTHENTICATED : The authentication process completed \r
148and the user has been successfully authenticated.\r
149- AUTHENTICATE_COMPLETE_NOT_AUTHENTICATED : The authentication process \r
150completed and the user was not successfully authenticated. \r
151The user may have clicked 'Cancel' at the Raven server.\r
152- AUTHENTICATE_COMPLETE_ERROR : There was an error during the authentication \r
153process forcing the authentication cycle to terminate early.\r
155As the 'Authenticate()' function may need to send HTTP headers, it must be \r
156called before any output (e.g. HTML, HTTP headers) is sent to the browser.\r
158The 'Default.asp' file provided is a sample of a simple server page using \r
159the 'Ucam_Webauth' VBScript class.\r
161Overview of Raven process\r
163A diagram of the Raven authentication process is located within the 'docs' \r
164folder as [I - Overview of Raven Authentication Process.pdf]. \r
166The authentication cycle consists of the following key stages:\r
168#### User first tries to access authenticated page\r
169User tries to load an authenticated page on a particular website. \r
170The 'Ucam_Webauth' class is loaded and the 'Authenticate()' function is called. \r
171If no authentication cookie is found to indicate the user is authenticated, \r
172the user's browser is redirected to a separate Raven server using a special \r
173'Authentication Request'. The authentication request consists of a series of \r
174authentication parameters encoded into the URL redirect as name/value pairs.\r
176#### User is prompted for login information\r
177The Raven server interprets the authentication request sent by the main \r
178website and prompts the user for their username and password. The user may \r
179then be successfully authenticated or may decide to click 'Cancel'. They are \r
180redirected back to the main website with a series of 'Authentication Response' \r
181parameters encoded into a 'WLS-Response' GET variable.\r
183#### User redirected back to main webserver\r
184The user's original page is loaded again and 'Authenticate()' is called a \r
185second time. 'Ucam_Webauth' processes the new 'WLS-Response' GET value and, \r
186if it's valid, sets an authentication cookie on the user's browser. The \r
187user's original page is then loaded again. \r
189#### User redirected back to main webserver again \r
190With an authentication cookie now set, 'Authenticate()' checks the status \r
191code contained in the value of the authentication cookie and returns either \r
194'AUTHENTICATE_COMPLETE_AUTHENTICATED' is returned , the original page can \r
195go on to display authenticated content to the user.\r
197Specifics of module\r
199The 'Authenticate()' function is the overarching authentication function of \r
200'Ucam_Webauth'. It performs some basic sanity checks using 'CheckSetup()' \r
201then uses 'GetCurrentState()' to establish the current state of the \r
202authentication process before branching accordingly. The possible return \r
203values of 'GetCurrentState()' are:\r
206A completely fresh authentication. 'SendAuthenticationRequest()' [*1*] is \r
207then triggered which performs some basic data checks, sets the authentication \r
208cookie to 'AUTHENTICATIONCOOKIE_REDIRECT_WLS' (to record where we are in the \r
209authentication process) and redirects the user's browser to the Raven \r
210authentication server with a series of authentication parameters \r
211encoded as name/value pairs.\r
214The Raven authentication server has processed the user and has returned the \r
215user's browser back to the original website with a series of authentication \r
216response parameters encoded into the 'WLS-Response' GET variable. \r
217'ProcessAuthenticationResponse()' [*2*] is then called which checks the \r
218validity of the 'WLS-Response' value, sets an authentication cookie and \r
219redirects the user back to the original page.\r
222A valid authentication cookie has been set \r
224'ProcessAuthenticationCookie()' [*3*] is then called which checks the \r
225validity of the cookie. If the cookie has expired, \r
226'SendAuthenticationRequest()' is called again in case the user needs to \r
227reauthenticate themselves. If the cookie is still valid, an \r
228'AUTHENTICATE_COMPLETE_XXX' value is returned, indicating that the \r
229authentication cycle has completed successfully. \r
230NOTE: this may be true if the user has cancelled the authentication process, \r
231in which case 'AUTHENTICATE_COMPLETE_NOT_AUTHENTICATED' will be returned.\r
233#### STATE_ERROR\r
234An error occurred, breaking the authentication cycle and returning \r
235AUTHENTICATE_COMPLETE_ERROR to 'Authenticate()'. This return value will \r
236also be generated by the other functions above if they generate an error.\r
238## Accompanying diagrams\r
239Detailed diagrams of the Raven process flow for (i) a successful \r
240authentication (ii) a cancelled authentication, are located in the 'docs' \r
241folder as [II - Ucam_Webauth - Flowchart for Valid Authentication.pdf] and \r
242[III - Ucam_Webauth - Flowchart for Cancelled Authentication.pdf], respectively. \r
244The numbers on these diagrams correspond to the three key secondary functions \r
245described above:\r
246- *1*. SendAuthenticationRequest()\r
247- *2*. ProcessAuthenticationResponse()\r
248- *3*. ProcessAuthenticationCookie()\r
250Other important functions include:\r
252### ResetState()\r
253Attempts to reset state as if a new user has just loaded a fresh browser \r
254window. This is typically used when a user has experienced an error and we \r
255want to give them a fresh opportunity to try again. \r
257### check_signature(...)\r
258Checks the signature provided by the Raven server, when it signed the \r
259'WLS-Response' variable, is a valid signature for the data. This ensures the \r
260data has not been tampered with.\r
262### hmac_sha1(...)\r
263Creates a hash value for signing the local authentication cookie.\r
265### wls_encode/decode(...)\r
266Encoding/decoding functions to allow base64 signatures to be sent within URLs.\r
268Possible arguments to 'Ucam_Webauth'\r
270(Based on documentation for PHP Raven authentication module)\r
272- log_file : \r
273The location for a log file that will record progress and track possible \r
274errors. The folder containing the file must be read/writable by the webserver.\r
275Default: log.txt\r
277- response_timeout : \r
278Responses from the central authentication server are time-stamped. \r
279This parameter sets the period of time in seconds during which these \r
280responses are considered valid. \r
281Default: 30 seconds.\r
283- key_dir : \r
284The name of the directory containing the public key certificate(s) required \r
285to validate the authentication responses sent by the server. \r
286Default: '/etc/httpd/conf/webauth_keys'.\r
288- max_session_life : \r
289The maximum period of time in seconds for which an established session will \r
290be valid. This may be overriden if the authentication reply contains a \r
291shorter 'life' parameter. Note that this does NOT define an expiry time for \r
292the session cookie. Session cookies are always set without an expiry time, \r
293causing them to expire when the browser session finishes. \r
294Default: 7200 (2 hours).\r
296- timeout_message : \r
297A re-authentication by the authentication service will be triggered when an \r
298established session expires. This option sets a text string which is sent to \r
299the authentication server to explain to the user why they are being asked to \r
300authenticate again. HTML markup is suppressed as for the description \r
301parameter described below. \r
302Default: 'your login to the site has expired'.\r
304- hostname (required) :\r
305The fully-qualified TCP/IP hostname that should be used in request URLs \r
306referencing the Ucam_Webauth-enabled application. This *must* be set, as it \r
307is needed for multiple reasons - primarily security but also to avoid varying \r
308hostnames in URLs leading to failed or inconsistent authentication. \r
309No default.\r
311- cookie_key (required): \r
312A random key used to protect session cookies from tampering. Any reasonably \r
313unpredictable string (for example the MD5 checksum of a rapidly changing \r
314logfile) will be satisfactory. This key must be the same for all uses of the \r
315web authentication system that will receive the same session cookies (see the \r
316cookie_name, cookie_path and cookie_domain parameters below). \r
317No default.\r
319- cookie_name :\r
320The name used for the session cookie. \r
321When used for access to resources over HTTPS the string '-S' is appended to \r
322this name. \r
323Default: 'Ucam-Webauth-Session'.\r
325- cookie_path :\r
326The 'Path' attribute for the session cookie. The default is the directory \r
327component of the path to the script currently being executed. This should \r
328result in the cookie being returned for future requests for this script and \r
329for the other resources in the same 'directory'; see the important \r
330information about the cookie_key parameter above. \r
331Default: '/'.\r
333- cookie_domain :\r
334The 'Domain' attribute for the session cookie. By default the 'Domain' \r
335attribute is omitted when setting the cookie. This should result in the \r
336cookie being returned only to the server running the script. Be aware that \r
337some people may treat with suspicion cookies with domain attributes that are \r
338wider than the host setting the cookie. \r
339No default.\r
341- auth_service : The full URL for the web login service to be used. \r
342Default: '' \r
344#### Authentication request properties\r
345The following setup parameters prefixed with 'authrequest_' relate to \r
346properties that will be sent to the authentication server as part of an \r
347authentication request:\r
349- authrequest_desc : A text description of the resource that is requesting \r
350authentication. This may be displayed to the user by the authentication \r
351service. It is restricted to printable ASCII characters (0x20 - 0x7e) though \r
352it may contain HTML entities representing other characters. The characters \r
353'<' and '>' will be converted into HTML entities before being sent to the \r
354browser and so this text cannot usefully contain HTML markup.\r
355No default.\r
357- authrequest_params : Data that will be returned unaltered to the WAA in \r
358any 'authentication response message' issued as a result of this request. \r
359This could be used to carry the identity of the resource originally requested \r
360or other WAA state, or to associate authentication requests with their \r
361eventual replies. When returned, this data will be protected by the digital \r
362signature applied to the authentication response message but nothing else is \r
363done to ensure the integrity or confidentiality of this data - the WAA MUST \r
364take responsibility for this if necessary.\r
365No default.\r
367- authrequest_skew : Interpretation of response_timeout is difficult if the \r
368clocks on the server running the PHP agent and on the authentication server \r
369are out of step. Both servers should use NTP to synchronize their clocks, \r
370but if they don't then this parameter should be set to an estimate of the \r
371maximum expected difference between them (in seconds). \r
372Default: 0.\r
374- authrequest_fail :\r
375If TRUE, sets the fail parameter in any authentication request sent to the \r
376authentication server to 'yes'. This has the effect of requiring the \r
377authentication server itself to report any errors that it encounters, rather \r
378than returning an error indication. Note however that even with this parameter \r
379set errors may be detected by this module that will result in authentication \r
380failing here. \r
381Default: FALSE.\r
383- authrequest_iact :\r
384If TRUE, then the 'iact' parameter provided to the authentication server is \r
385set to 'yes'. If FALSE, then the 'iact' parameter is set to 'no'. If no value \r
386is provided for 'authrequest_iact', the 'iact' parameter is left blank. \r
387The value 'yes' for 'iact' requires that a re-authentication exchange takes \r
388place with the user. This could be used prior to a sensitive transaction in \r
389an attempt to ensure that a previously authenticated user is still present \r
390at the browser. The value 'no' requires that the authentication request will \r
391only succeed if the user's identity can be returned without interacting with \r
392the user. This could be used as an optimisation to take advantage of any \r
393existing authentication but without actively soliciting one. If omitted or \r
394empty, then a previously established identity may be returned if the WLS \r
395supports doing so, and if not then the user will be prompted as necessary.\r
396Default: omitted.