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Review - Web Services Security: SOAP Message Security (1 of 3)

From: Marc Hadley <Marc.Hadley@Sun.COM>
Date: Wed, 24 Sep 2003 11:27:35 -0400
To: xml-dist-app@w3.org
Message-id: <9F54E0DA-EEA3-11D7-80D5-0003937568DC@sun.com>

In partial fulfillment of my action item from last week's telcon, the  
following is my initial review of the first part of the Web Services  
Security committee specification for consideration by the XMLP WG.  
Reviews of the other two parts will follow as time allows.

Regards,
Marc.

Web Services Security - W3C XMLP WG Review
------------------------------------------

This review refers to Web Services Security: SOAP Message Security  
located at

http://www.oasis-open.org/committees/download.php/3281/WSS- 
SOAPMessageSecurity-17-082703-merged.pdf

linked from the WSS TC homepage at:

http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=wss

The comments follow document order, I have indicated the sections of  
the document and line numbers where appropriate. Significant/serious  
issues are called out with ***, other issues are mainly editorial in  
nature.


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Web Services Security: SOAP Message Security
--------------------------------------------

General
Needs a good proof reading session. There are numerous grammatical and  
punctuation errors, some of which are noted below. A pass needs to be  
made through the spec to ensure all the text uses consistent  
terminology, e.g. SOAP header and SOAP header block are used  
interchangeably thoughout the document. Suggest adopting the SOAP 1.2  
Recommendation terminology for clarity and consistency. Despite  
referring to SOAP 1.2, most, if not all, of the examples and namespace  
URIs are taken from previous versions of SOAP or early drafts of the  
SOAP 1.2 Recommendation - a pass through the document to ensure  
alignment with the SOAP 1.2 Recommendation is required.

Status
The TC home page describes documents that have achieved committee spec  
status. However the link points to a document whose status section  
indicates it is an 'interim draft'. Shouldn't the status section  
reflect the committee spec status ?

Abstract
"No specific type of security token is required the specification is  
designed to be extensible (e.g. support multiple security token  
formats).": insert a comma after 'required', change 'e.g.' to 'i.e. to'.

1. Introduction

*** The introduction talks about SOAP extensions. For consistency with  
SOAP 1.2, it should instead use the SOAP 1.2 terminology of features  
and modules. See section 3 of SOAP 1.2 Part 1.

110 "This specification provides three main mechanisms: ability to send  
security token as part...": 'a security token' or 'security tokens'.

1.1.1 Requirements

139, looks like this should be part of the bulletted list rather than a  
standalone paragraph.

2. Notational Conventions
Throughout the document certain words and phrases are highlighted in  
blue or red. E.g. the word SOAP is often highlighted in blue. There is  
no mention of any notational convention applicable to this coloring so  
its not clear if it has any particular meaning or intent. When printed  
in black and white its unlikely that such color information will be  
visible so it would be better to use some other typographic convention,  
e.g. italics or bold. On further reading it seems that blue coloring is  
intended to convey a bibiographic citation - a better means of  
indicating this is required.

Lines 150-155 seem to be in a different font though the reason for this  
is unclear.

2.2 Namespaces

*** 170, 171: Its surprising to see the WSS namespace URIs using the  
xmlsoap.org domain. This domain is the property of Microsoft Corp and  
they maintain control over what such namespace URI resolve to. For an  
OASIS standard one would expect namespace URIs to use the  
oasis-open.org domain instead.

175: Update the soap namespace to use the one from the SOAP 1.2  
Recommendation.

2.3 Terminology

*** 185 "End-To-End Message Level Security - End-to-end message level  
security is established when a message that traverses multiple  
applications within...": Should 'applications' be 'SOAP intermediaries'  
? SOAP 1.2 defines the SOAP message path as "The set of SOAP nodes  
through which a single SOAP message passes. This includes the initial  
SOAP sender, zero or more SOAP intermediaries, and an ultimate SOAP  
receiver." A single SOAP message doesn't traverse multiple applications  
unless they are SOAP intermediaries, if they are not then each  
application-application interaction is effectively a separate SOAP  
message exchange.

*** For clarity, adoption of the SOAP 1.2 terminology (Part 1, section  
1.3 Terminology) is recommended.

3.2 Message Protection

252 "This document defines syntax and semantics of signatures within  
<wsse:Security> element.": 'a ... element' or 'the ... element'.
253 "This document does not specify any signature appearing outside of  
<wsse:Security> element.": 'a ... element' or 'the ... element'.

*** SOAP 1.2 is XML Infoset based, should the SOAP Message Security  
spec also be based on Infoset ? Specifically, is SOAP Message Security  
applicable to non-XML 1.0 serializations or is it tightly bound to XML  
1.0 syntax ? If the former, then reference to elements, attributes etc  
should be replaced with the Infoset equivalents (element information  
item etc) and the relationship between the infoset and the octet stream  
used as input to cryptographic operations shoudl be clarified. If the  
latter then this restriction must be explicitly noted as its likely  
that future SOAP 1.2 bindings may choose alternate SOAP message  
serialization formats.

3.3 Invalid or Missing Claims

255 "The message recipient SHOULD reject a message with an invalid  
signature, a message that is missing necessary claims and a message  
whose claims have unacceptable values as such messages are unauthorized  
(or malformed) message..": Bad grammar, replace with something like "A  
message recipient SHOULD reject messages containing invalid signatures,  
messages missing necessary claims or messages whose claims have  
unacceptable values. Such messages are unauthorized (or malformed)."

3.4 Example

Example uses a SOAP 1.1 envelope, change to use SOAP 1.2.

5 Security Header

400 "The <wsse:Security> header block provides a mechanism for  
attaching security-related information targeted at a specific recipient  
in a form of a SOAP role.": change 'in a form of a' to 'in the form of  
a'.

*** 406 "a message MAY have multiple <wsse:Security> header blocks if  
they are targeted for separate recipients." why can't a message contain  
multiple wsse:Security header blocks targetted at the same recipient,  
this seems like an uneccessary/arbitrary restriction.

*** 410 "The <wsse:Security> header block without a specified S:role  
MAY be consumed by anyone, but MUST NOT be removed prior to the final  
destination or endpoint." What does 'consumed' mean. SOAP 1.2 makes it  
clear that SOAP headers without a role attribute are equivalent to  
those with a role of  
"http://www.w3.org/2003/05/soap-envelope/role/ultimateReceiver". In  
both cases the ultimate receiver of the message is the target of the  
header block.

*** 450 "All compliant implementations MUST declare which profiles they  
support": how must they declare this ? This seems like an untestable  
assertion and should probably be dropped.

*** 455 "The optional mustUnderstand SOAP attribute on Security header  
simply means you are aware of the Web Services Security: SOAP Message  
Security specification, and there are no implied semantics.": No ! The  
mustUnderstand attribute has the semantics as defined by the SOAP 1.2  
specification. All SOAP nodes MUST abide by the SOAP processing model  
including generation of mustUnderstand faults if the header block is  
not understood. SOAP modules and features cannot override these  
semantics.

6.2 Username Token

495 "This is an extensibility mechanism to allow additional attributes,  
based on schemas, to be the <wsse:Username> element.": change 'to be  
the' to 'to be added to the'.

*** 503 "All compliant implementations MUST be able to process a  
<wsse:UsernameToken> element." The element is extensible, what should  
compliant implementations do with extensions they don't understand -  
ignore them, fault, ... Such extensibility semantics must be defined  
for all extensible elements, just making things extensible isn't  
sufficient.

506 Change example to use SOAP 1.2 envelope instead of SOAP 1.1.

6.3 Binary Security Tokens

545 "This attribute is extensible using XML namespaces.": Confusing,  
the attribute isn't extensible in itself, but its value could be said  
to be extensible though really just saying the attributes type is a XML  
qualified name is probably sufficient.

*** 548 /wsse:BinarySecurityToken/@EncodingType: this seems to be  
reinventing XML schema to a certain extent. Wouldn't it be better to  
allow child elements of BinarySecurityToken, one per type of encoding,  
that way a schema processor can verify the contents on behalf of the  
wsse processor.

*** Also, why use qualified names instead of URIs for identifying  
encoding types. URIs don't have the problem of maintaining namespace  
prefixes that demands the ns declaration location requirements outlined  
in this section. Use of qualified names in element and attribute values  
complicates things...

*** 558 "All compliant implementations MUST be able to process a  
<wsse:BinarySecurityToken> element.": same comment as for  
UsernameToken, what should an implementation do with a token of unknown  
type or one containing an extension that is not understood.

6.4 XML Tokens

*** 578 "This section presents the basic principles and framework for  
using XML-based security tokens." Is this section complete ? There's no  
trace of any principles or a framework.

7.1 SecurityTokenReference Element

*** Same comment as for BinarySecurityToken re extensibility semantics  
and requiring all implementations to be able to process the element.

8.1 Algorithms

*** Surprised that there is no mention of SOAP Message Normalization  
(sop12-n11n) here:  
http://www.w3.org/TR/2003/NOTE-soap12-n11n-20030328/. How does SOAP  
Message Security cope with the variations that soap12-n11n aims to  
removes from messages ?

*** 832 "Finally, if a sender wishes to sign a message before  
encryption, they should alter the order of the signature and encryption  
elements inside of the <wsse:Security> header.": alter in what way,  
this needs to be more specific.

839 "care MUST be taken in creating a signing policy that requires
signing of parts of the message that might legitimately be altered in  
transit.": shouldn't this say "care MUST be taken not to create a  
signing policy that requires signing of parts of the message that might  
legitimately be altered in transit." ?

841 "SOAP applications MUST satisfy the following conditions: The  
application MUST be capable of processing the required elements defined  
in the XML Signature specification.": SOAP applications or WSS  
implementation ? The latter is used elsewhere in the specification.

*** 855 "If overall message processing is to remain robust,  
intermediaries must exercise care that their transformations do not  
affect of a digitally signed component.": again a reference to  
soap12-n11n would seem to be in order here. Intermediaries are allowed  
to perform certain transformations, rather than implying the need for  
additional restrictions on intermediaires it seems more realistic to  
require normalization of the effects of such legal transformations.

9 Encryption

1026 "The combined process of encrypting portion(s) of a message and  
adding one of these a sub-elements is called an encryption step  
hereafter.": remove the 'a' between 'these' and 'sub-elements'.

9.3.1 Encryption

*** The suggested process for performing encryption would only include  
the data from the original message that was encrypted. All other data  
would be ommitted, suggest adding an additional step to copy in all the  
non-encrypted data.

*** 1166 "Parts of a SOAP message may be encrypted in such a way that  
they can be decrypted by an intermediary that is targeted by one of the  
SOAP headers. Consequently, the exact behavior of intermediaries with  
respect to encrypted data is undefined and requires an out-of-band  
agreement.": more detail required, why is the behaviour undefined ?  
Surely the intermediary would decrypt the parts as instructed by the  
corresponding header block ?

12 Error Handling

*** The specification should define the values of the  
Fault/Reason/Text, Fault/Code/Value and Fault/Code/Subcode/Value EIIs.  
Presumably the defined codes are the allowable values of the  
Fault/Code/Subcode/Value EIIs ? What values should be used for each  
code in the corresponding Fault/Reason/Text, Fault/Code/Value EIIs ?

16 References

1545 [SOAP12] W3C Working Draft, 26 June 2002: This should be updated  
to point to the SOAP 1.2 Recomendation.

--
Marc Hadley <marc.hadley@sun.com>
Web Technologies and Standards, Sun Microsystems.
Received on Wednesday, 24 September 2003 11:27:52 GMT

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