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Re: [widgets] OMTP input to W3C Widget Requirements (1 of 2)

From: Marcos Caceres <marcosscaceres@gmail.com>
Date: Fri, 05 Sep 2008 13:30:12 +0000
Message-ID: <b21a10670809050629v41decd96k3682da57c63f6c49@mail.gmail.com>
To: "David Rogers" <david.rogers@omtp.org>, "Nick Allott" <nick.allott@omtp.org>, "Priestley, Mark, VF-Group" <Mark.Priestley@vodafone.com>, "Paddy Byers" <paddy@aplixcorp.com>
Cc: public-webapps-request@w3.org, art.barstow@nokia.com

Hi All,
I've now integrated the OMTP requirements into the Req spec. OMTP
crew, I'm made lots of edits (and dropped some of your requirements
with Mark's permission) so please check to see that your intent is
still conveyed (and that I haven't introduced any new typos, etc.).

Apologies to those who are still waiting for me to respond to your
comments, I'm going as fast as I can and will do my best to address
everyone's comments within the next week.

Kind regards,
Marcos
[1] http://dev.w3.org/2006/waf/widgets-reqs/
On Fri, Aug 1, 2008 at 12:30 PM, David Rogers <david.rogers@omtp.org> wrote:
> Dear Art, Marcos and all,
>
>
>
> Please find attached the OMTP BONDI input to the W3C Web Applications WG
> Widget Requirements last call. I've extracted the text of the input below.
> Please note this is the first of two sets of input. This first input
> contains comments to existing requirements and proposals for new
> requirements. The second document contains more general comments, applicable
> to the Widget Requirements and also the Packaging and Configuration work.
>
>
>
> Introduction
>
>
>
> OMTP is a forum backed by many of the largest mobile operators and has
> members from many hardware and software vendors across the value chain.
>
> It was set up with the aim of gathering and driving mobile terminal
> requirements to ensure consistent and secure implementations, thereby
> reducing fragmentation and simplifying the customer experience of mobile
> data services. OMTP recommendations benefit carriers, content providers,
> middleware vendors and handset manufacturers to develop open and compatible
> mobile devices.  OMTP have created their BONDI initiative to specifically
> address the problem of fragmentation in the evolution of the mobile web and
> to ensure the protection of the user from malicious web based services. The
> BONDI initiative will be delivering documentation throughout 2008 with the
> aim of driving activities in other appropriate standardisation and industry
> bodies such as W3C.
>
> Devices supporting some of the features of BONDI will become available in
> 2009.
>
> This document forms the input from BONDI relating to the security aspects of
> the W3C Widgets: 1.0 Requirements found at
> http://www.w3.org/TR/2008/WD-widgets-reqs-20080625/.
>
> The document is divided into two parts; the first part details proposed
> changes to existing W3C requirements, the second part proposes new
> requirements that for inclusion.
>
>
>
> Part I - Changes to Existing Requirements Proposed By BONDI
>
>
>
> R11. Digital Signature
>
> We suggest the following re-wording of the existing requirement so that it
> reads:
>
> "A conforming specification MUST specify a means to verify the authenticity
> and integrity of all resources in a widget resource, with the exception of
> any resources explicitly excluded by the specification. A conforming
> specification MUST provide this capability by specifying a processing model
> for generating and verifying a digital signature associated to a widget
> resource. The digital signature scheme MUST be compatible with existing
> Public Key Infrastructures (PKI), particularly X.509 digital certificates.
> In addition, the recommended digital signature format SHALL support the
> ability to include a certificate chain with a digital signature to enable
> the receiving device to build a certificate chain from the end entity
> certificate used to generate the signature to a locally stored root
> certificate. In addition, the recommended digital signature format SHOULD
> support the ability for a widget resource to be signed using multiple end
> entity keys (i.e. it SHOULD be possible to include multiple signatures and
> associated certificate chains)."
>
> The proposed changes attempt to tighten and clarify the use of digital
> signatures and certificate chains. In addition we suggest that the following
> text should be added to the existing requirement:
>
> "A conforming specification SHALL specify the expected behaviour when
> multiple signatures and certificate chains are provided. A conforming
> specification SHALL specify that if none of the signatures and certificate
> chains can be verified, e.g. because of missing root certificates or where
> any certificates in the chain have expired or are not yet valid, then the
> widget resource SHALL be treated as unsigned. A conforming specification
> SHALL specify that the widget environment SHALL not install or load a
> widget resource when it can determine that any certificate in the chain has
> been revoked."
>
> This addition is to ensure that there is a consistent behaviour when
> verifying signatures and certificate chains, especially in error cases in
> which the verification fails because of missing certificates and in which
> one of the certificates has been revoked.  We use the term load to cover the
> case in which a widget is not subject to an installation event.
>
>
>
> In addition, we suggest the following changes to the Rationale:
>
>
>
> "To provide a means to verify authenticity, check data integrity, and
> provide a means of non-repudiation for users." to "To provide a means to
> verify the authenticity, check the data integrity and provide persistent
> proof of origin of the widget resource."
>
> "a digital signature" to "are digitally signed"
>
> And the following addition:
>
>
>
> "The ability to provide certificate chains with signatures is vital,
> particularly in the mobile world, to allow end entity certificates to be
> chained to a locally installed root.
>
>
>
> The ability to include multiple signatures can help address the issue that
> target devices may have different root certificates installed. Equally there
> SHOULD be defined behaviour for what happens when a required root isn't
> available. Treating this case as an error case (and therefore not allowing
> the installation of the widget) has been seen to encourage developers not to
> get the applications signed whereas allowing this case but treating widgets
> as unsigned doesn't provide the same disincentive."
>
>
>
>
>
> R21. Security Declarations
>
> We suggest the addition of the following text to the existing requirement:
>
>
>
> "This SHALL include a means of declaring the APIs that a widget expects to
> access. A conforming specification SHALL provide a means to verify the
> authenticity and integrity of security declarations included in the widget
> resource."
>
>
>
> The reason for this suggested addition is to make it explicit that it must
> be possible to include required APIs in the security declarations. In
> addition, we suggest that the security declarations should be treated as a
> protected resource as the authenticity and integrity of this information is
> essential if it is to be used when making security decisions.
>
>
>
> These proposed modifications are based on the assumption that security
> declarations are included in the configuration document, which can be used
> independently of the widget resource, as stated in R.23. If this is not the
> case then an additional requirement is needed to ensure that the security
> declarations can be used independently of the widget resource.
>
>
>
>
>
> R38. Additional Digital Certificates
>
> We suggest that the requirement is re-worded along the following lines "A
> conforming specification SHOULD define mechanisms to enable end-users to
> install additional root certificates, provided this is compatible with the
> security policy of the widget processing environment."
>
> The reason for this proposal is that the existing requirement seems to
> suggest that the user should always be able to install additional root
> certificates on their device whereas in our opinion this capability should
> be controlled by the security policy of the device. In addition, we have
> removed the reference to standard root certificates as this implies a set of
> root certificates that are common across all devices.
>
> In addition, we suggest that following text is added to the rationale "using
> self-signed or test certificates, and install these test certificates on a
> device in order to test their widget on a real device." as this links more
> closely to the requirement.
>
>
>
>
>
> R43. Default Security Policy
>
> While we agree that it is a requirement to be able to specify a default
> security policy, and that this should err on the side of caution, we would
> like to seek clarification of this requirement?
>
>
>
> For example, is the intention to mandate static declarations of requested
> permissions or are programmatic requests also to be allowed?
>
>
>
> We would also like to indicate that BONDI are currently working on a policy
> framework and the definition of default or recommended policies and policy
> configurations and would like to co-ordinate this work with W3C.
>
>
>
>
>
> R44. Runtime Security Exceptions
>
> In the sentence "A conforming specification MUST specify runtime exceptions
> for when the API attempts to perform an action it is not authorized to
> perform." suggest that "API" is changed to "widget" as this seems to fit in
> better with the rationale?
>
> Normative references
>
> We suggest that the reference for X.509 is updated as follows:
>
>
>
> X.509
>
> RFC 3280: Internet X.509 Public Key Infrastructure Certificate and
> Certificate Revocation List (CRL) Profile, R. Housley. IETF, April 2002.
> Available at: http://www.ietf.org/rfc/rfc3280.txt
>
> Part II - New Requirements Proposed By BONDI
>
>
>
> The following text proposes new requirements, related specifically to
> security mechanisms that have been derived from ongoing work within BONDI.
>
>
>
>
>
> RXX. Signature Document Independence
>
> A conforming specification MUST specify the digital signature format in such
> a way that the signature value(s) and associated certificate chain(s) can be
> used independently of the widget resource that is covered by the digital
> signature. A conforming specification SHOULD provide guidelines for how the
> signature(s) and certificate chain(s) can be used separately from a widget
> resource. A conforming specification SHOULD specify a means to provide the
> independent signature document in conjunction with the independent
> configuration document (see R23).
>
> Motivation:
>
> Web and offline distribution, device independence current development
> practice or industry best-practices
>
>
>
> Rationale:
>
> To allow the signature information to be extracted and used by other
> applications (either on the server or on the client side) for different
> purposes. For example, a server may automatically extract the signature
> information from a widget resource and serve it upon request. The
> independent signature information may then be used, for instance, to provide
> the user with information about the source (signing entity) and associated
> trust level of the widget without needing to download the complete widget
> resource. Additionally, if combined with security declaration information,
> the signature information may allow a security decision to be made about
> whether or not the widget will run properly, enabling a further decision to
> be made as to whether to continue to download and install the widget. This
> may be particularly useful for users of widgets on mobile devices, where the
> cost of downloading data can sometimes be expensive.
>
>
>
> Comment:
>
> This is common practice in the mobile world with Java applications. The
> purpose of pre-verifying elements of the signature and certificate chain is
> to address the case in which a widget provided by a non-malicious developer
> fails to install because for example, the certificate is out of date or no
> revocation information is available. It also allows parallel OCSP round
> trips while downloading widget resource (as is done for Java apps in the
> mobile world)
>
>
>
>
>
> RXX. Independence of Non-Security Critical Information from Digital
> Signature
>
> A conforming specification SHOULD make it possible to change non-security
> critical information associated to the widget resource without having to
> re-sign the widget resource. The non-security critical information may or
> may not be included in the widget package. A conforming specification SHALL
> specify which information can be considered non-security critical. A
> conforming specification SHOULD specify a means to provide this non-security
> critical information in conjunction with the independent configuration
> document (see R23).
>
>
>
> Motivation:
>
> current development practice or industry best-practices
>
> Rationale:
>
>
>
> Some information associated to the widget resource might need to be changed
> during ingestion (e.g. version, provider, name etc.). This is common when a
> single developer provides the same content to a number of re-sellers. It may
> be that the same information needs to be provided with the configuration
> document.
>
>
>
>
>
> RXX. Signing Procedure Agnostic
>
> A conforming specification SHALL specify a mechanism for signing a widget
> resource that does not explicitly or implicitly impose any restrictions on
> the procedure for generating the signature. More specifically, a conforming
> specification SHALL allow the use of end entity keys stored in a secure
> module in a hosted environment. A conforming specification SHALL specify
> that implementations SHOULD be able to use end entity keys via a PKCS#11
> interface.
>
>
>
> In addition, the mechanism SHALL make it feasible for end entity keys to be
> used once and then securely deleted.
>
>
>
> Motivation:
>
> Security, current development practice or industry best-practices
>
> Rationale:
>
> To enable signing schemes to provide assurances that a high level of
> end-to-end security has been maintained around the signing process, in
> particular assurance that the signing key has not been compromised. PKCS#11
> is the most widely supported standard interface for hardware security
> modules.
>
>
>
>
>
> RXX. Support for Multiple Message Digest Algorithms
>
> A conforming specification SHALL specify that where the integrity of data is
> protected using a message digest, it SHALL be possible to use the SHA-1
> message digest algorithm and SHALL be possible to use the SHA-256 message
> digest algorithm.
>
>
>
> Motivation:
>
> Security
>
> Rationale:
>
> Due to known weaknesses in the SHA-1 algorithm and the expected lifetime of
> implementations it is prudent to strongly recommend support for SHA-256 to
> ensure that the overall security of the solution is maintained.
>
>
>
>
>
> RXX. Support for Multiple Signature Algorithms
>
> A conforming specification SHALL specify that where digital signatures are
> used it SHALL be possible to use the DSA signature algorithm and SHALL be
> possible to use the RSA signature algorithm.
>
>
>
> Motivation:
>
> Security
>
> Rationale:
>
> Security best practice: to support two algorithms to mitigate against the
> risk that weaknesses are found with a selected algorithm.
>
>
>
>
>
> RXX. Key Lengths
>
> A conforming spec SHALL specify that widget processing environments SHALL
> support RSA with key lengths up to at least 2048 bits and SHALL support DSA
> with key lengths up to at least 2048 bits (see NIST Recommendation). A
> conforming spec SHALL recommend that widget signing tools SHALL support and
> use RSA with key lengths of at least 2048 bits and DSA with key lengths of
> at least 2048 bits (see NIST Recommendation).
>
>
>
> Motivation:
>
> Security
>
> Rationale:
>
> To be in-line with current security recommendations and provide longevity of
> the system security. In some use cases it may be desirable to use key
> lengths of less than 2048 bits, e.g. where the impact on performance
> outweighs the additional security afforded.
>
>
>
>
>
> RXX. Key Usage Extension
>
> A conforming specification MUST specify the expected use of valid key usage
> extensions and when present (in end entity certs) MUST specify that
> implementations verify that the extension has the digitalSignature bit set.
>
>
>
> A conforming specification MUST specify that implementations recognize the
> extended key usage extension and when present (in end entity certs) verify
> that the extension contains the id-kp-codeSigning object identifier. A
> conforming specification MAY also define a new OID specifically for widget
> signing, and specify that implementations verify that the extended key usage
> extension in the end entity cert contains this new OID.
>
>
>
> Rationale:
>
> To maintain compliance to RFC 3280 (experience suggests that if this is not
> explicitly required then the RFC 3280 is not followed when it comes to key
> extension usage).
>
>
>
> Compliance ensures that only certificates intended to be used (issued for)
> code signing can be used to sign widget resources.
>
>
>
> Comments:
>
> Using the extended key usage extension "id-kp-codeSigning" would in theory
> allow the same end entity certificate to be used to sign any executables
> including widgets, Java applets and native executables. However, it should
> be possible to restrict the use of a particular end entity certificate so
> that it can only be used to sign certain a certain type (or types) of
> executables by associating a usage restriction with the root certificate to
> which the end entity certificate is chained.
>
>
>
>
>
> RXX. Inclusion of Revocation Information
>
> A conforming specification SHOULD specify a means of packaging up-to-date
> revocation information with digital signature and associated certificate
> chain (e.g. a CRL or OCSP response stating that certificate has not been
> revoked). In addition, a conforming specification SHOULD specify the
> behaviour in the case that the revocation information is not included or not
> complete. A conforming specification SHOULD specify that if the revocation
> information is present the widget processing environment MUST attempt to
> verify the revocation information. A conforming specification SHOULD specify
> the behaviour if revocation information is out of date or otherwise invalid.
>
>
>
> In addition, the mechanism specified SHALL not require the widget resource
> to be re-signed to include new revocation information.
>
>
>
> Rationale:
>
> To provide up-to-date revocation information, when it is needed by the
> widget engine, without requiring a query to an online CRL or OSCP server
> from each device. This is a lot more efficient and eases the load on CRL or
> OSCP servers.
>
>
>
>
>
>
>
>
>
> --------  END OF DOCUMENT  --------
>
>
>
>
>
>
>
>
>
> Many thanks,
>
>
>
>
>
> David.
>
>
>
> David Rogers
> OMTP Director of External Relations
> m: +44 (0) 7771 838197  david.rogers@omtp.org
> skype: dg.rogers
>
> linkedIn: http://www.linkedin.com/in/davidrogersuk
>
> OMTP Ltd.
> Marble Arch Tower
> 55 Bryanston Street
> London
> W1H 7AJ
>
> www.omtp.org
>
> P Please consider the environment  don't print this mail unless you really
> need to...
>
>



-- 
Marcos Caceres
http://datadriven.com.au
Received on Friday, 5 September 2008 13:37:19 GMT

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