Asiri Rathnayake wrote: > Hi Devs, > > I have hit a wall trying to implement Digest Access Authentication for the > xwiki-webdav module. I'll try to be clear as much as possible. > > *+ INTRO* : Digest Access Authentication is used to avoid the transmission > of clear text passwords over http for authenticating users. Instead of the > clear text password, following hash (RESPONSE) will be transferred to the > server by client, > > HA1 = MD5(username,password,realm) > HA2 = MD5(method,digestURI) > RESPONSE = MD5(HA1,nonce,HA2) > > Here the 'nonce' is some weird string token generated by the server for that > particular client for a particular session. So the RESPONSE instead of the > clear text password will be transferred to the server. For more specific > information about Digest Authentication, you may refer [1]. > > *+ PROBLEM* : Simply put, the way xwiki handles authentication requires the > presentation of a clear text password by the client (which is not available > with Digest Authentication scheme). What we have with xwiki (on the server > side) is a crypted version of the original password. > > One possible solution to overcome this limitation is to store the HA1 value > in our databases (is this possible ?). This is one of the limitations of > Digest Authentication scheme as mentioned in [1] : > > *"There is an important problem with implementing Digest access > authentication. This is the requirement that either cleartext passwords or > the HA1 hashes must be known in order to perform client response validation" > * > > I would like to know what other developers have to say about this issue, and > possible workarounds ... [?] > > Thanks. > > - Asiri > > [1] http://en.wikipedia.org/wiki/Digest_access_authentication
Hi devs, This is a serious roadblock, and it cannot be easily solved. The main idea is that whatever data we keep in the database of the wiki, it is accessible. Storing HA1 is as safe as storing a plaintext password. Anybody with edit access and a bit of cracking/hacking experience can get it out of the wiki. So I'm a strong -1 against storing any unencrypted login information. I can't see any simple and clean mechanism to work around this problem. There's no way we can validate the correct password. Some hacks we could use in the worst case are: 1. Something like Niels suggested, authenticate in a third service over SSL and use a generated token as the password. This is cumbersome for many reasons, like: this token should expire often, for security reasons; the need for a certificate + HTTPS configuration; adding a new service; increased complexity; and many others. 2. Something similar to what is done for the current password. I don't go into further details now since I'm sleepy, and it's too ugly to be taken into account seriously. 3. Use Basic auth, but force https to be used. This means that we must document (or link to external documentation) how to setup https on various containers. 4. Find the time to implement crypt password storing mechanism. This means that the password can also be decrypted, unlike the current hash mechanism. This involves more effort, and is less secure than what we have now (I'd like that the user's password can never be retrieved, not even by the wiki and server owner). 5. Try to find other ways to authenticate. I always try to approach the problem from a different angle, since many times a difficult technical question is actually the dead end of a wrong solution to a different problem. So, why do you need to implement Digest authentication? What is your scenario? What is the goal? Do you have a link to the WebDAV authentication specification? Can we use cookies instead? Can we use OpenID authentication? -- Sergiu Dumitriu http://purl.org/net/sergiu/ _______________________________________________ devs mailing list [email protected] http://lists.xwiki.org/mailman/listinfo/devs
