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Subject: RE: [wss] Web Services Security Username Token Profile
Thanks for the comments, Zahid. I agree that in practice SSL/TLS can, and will often (usually?), be used to provide these capabilities. I still believe, however, that we should address cases where transport level security is either not an option, or for some other reason (application specific, perhaps) is not being used. On the XML Signature spec, the use of other algorithms will not break our compliance with the standard. While the spec does define identifiers for the DSA and RSA algorithms, it is intended to be extensible: "... the mechanism is extensible; alternative algorithms may be used by signature applications." This is analogous to the extensions in the <ds:KeyInfo> element, or the definition of Transform URIs, both of which we are currently planning to use for SecurityTokenReferences. I actually have no problem with your idea of keeping the existing Username token profile (using nonce, creation timestame, digests, etc.), and perhaps adding a second Username profile which would provide the binding with the message. This was, in fact, where my thinking was headed, as well. I do think, however, that we need to point out the security issues in the Threat Model, and at least state that secure transports can alleviate these concerns. (But, then again, if you are using a secure transport, why bother doing anything more than sending the password in clear text?) Thanks, again, - Gene - -----Original Message----- From: Ahmed, Zahid [mailto:zahid.ahmed@commerceone.com] Sent: Wednesday, January 29, 2003 1:09 PM To: 'Web Services Security' Subject: RE: [wss] Web Services Security Username Token Profile Generally, I don't think it is a good idea to coerce Password tokens to behave like other types of tokens that require proof of possession or evidence of holding the (signing) key. I do, however, appreciate the motivation of securely binding the Password token to a part of SOAP message such that we can protect the integrity of token association with the message indepedent of the transport protocol used to transmit the SOAP message. We can also argue that encryption of password is required independent of transport security. However, in practice, the SSL/TLS transport is sufficient in both of these problem domains. I'm also concerned that we do not want to generate signature using PBE algorithm (using the Password in Password token) if it will imply not being compatible with W3C XML Signature which specifies use of DSA (required) and RSA algorithms (optional). Perhaps we could consider this as new token profile, but keep the basic password token profile scope as is. thanks, Zahid -----Original Message----- From: Gene Thurston [mailto:gthurston@amberpoint.com] Sent: Wednesday, January 29, 2003 12:10 PM To: 'Web Services Security' Subject: RE: [wss] Web Services Security Username Token Profile Colleagues, [.......] (General) Discussion: Overall, while I think that this token profile will be widely used (perhaps the first one to be widely used, since folks are generally familiar with, and have large databases of, username/password pairs), I see that its main weakness is the lack of binding the token to the message "request" or "response" (that is, some part of the message body which represents what the username is "saying". While it is true that using a secure transport (such as HTTP over SSL) can provide this, there is an alternative approach, which in some sense fits in better with the overall WS-Security processing model of using signatures to provide this "binding". (Of course, signatures also provide evidence of the "claims" asserted by the presence of various tokens.) So, I think another profile here, surrounding the Username token goes something like this: * Username token only carries the username. (The implicit claim here is that the user named is the "sender", I suppose.) * A signature is included using a PBE algorithm, and signs that portion of the body that the "sender" is stating ... typically, the message Body. * The signature may also sign the timestamp header (described in Appendix A of the Web Services Security: SOAP Message Security specification) to combat replay attacks. (Side note: Shouldn't we add a general <wsu:Nonce> element as a header which can be used by *all* types of tokens?) * The <ds:KeyInfo> element of the signature will use a <wsse:SecurityTokenReference> to the Username token. * The "key" associated with that token will be generated based on the mutually shared secret password (or equivalent) using a standard PBE algorithm. It seems to me that the user interaction in this scenario will still look the same: Need a username and password. But, that the processing model is now a lot more consistent with the other kinds of security tokens we expect to see. Basically, while I don't believe we have come right out and said so, I think *all* of the token types we have considered can be thought of as "Key Holders" ... either a key is explicitly embedded in the token (ala, X.509 certificates), or a key is somehow implicitly represented or can be generated. Am I way off base here? That's about it. Thanks for playing! - Gene Thurston - AmberPoint, Inc. -----Original Message----- From: Anthony Nadalin [mailto:drsecure@us.ibm.com] Sent: Tuesday, January 28, 2003 6:33 AM To: Web Services Security Subject: [wss] Web Services Security Username Token Profile Here is the UsernameToken update that Phil created it was edited to be in line with the WSS-Core-09 update. (See attached file: WSS-Username-11.pdf) Anthony Nadalin | work 512.436.9568 | cell 512.289.4122 ---------------------------------------------------------------- To subscribe or unsubscribe from this elist use the subscription manager: <http://lists.oasis-open.org/ob/adm.pl>
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