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Re: [saag] i18n requirements (was: Re: NF* (Re: PKCS#11 URI slot attributes & last call))

2015-01-04 08:54:13
On Sun, 4 Jan 2015, Jaroslav Imrich wrote:

Hello Jan,

the text mentions "NFC" but I was unable to find any pointer or reference
to its definition. I was not familiar with the term before so I think
reference in the text would be helpful.

        hi Jaroslav, it's defined in the Unicode standard which I can 
reference directly but you would still need to search for the term 
rather than read the whole standard.

        please google "unicode NFC", all first hits lead to the right 
information.

        Jan.


Regards, Jaroslav


On Sun, Jan 4, 2015 at 6:58 AM, Jan Pechanec 
<jan(_dot_)pechanec(_at_)oracle(_dot_)com>
wrote:

On Thu, 1 Jan 2015, Nico Williams wrote:

        Nico, many thanks for the drafted text and also to Patrik and
John for discussing it.

        I've updated the draft in sections on URI matching guidelines,
URI comparision, added a new section on I18n, and added a new paragraph
to the Security considerations.  Individial diffs inline, a draft for
new draft 18 attached (draft-pechanec-pkcs11uri-18-v1.txt).

I think we could use some text like this:

  PKCS#11 does not specify a canonical from for UTF-8 string slots in
  the API.  This presents the usual false negative and false positive
  (aliasing) concerns that arise when dealing with unnormalized
  strings.  Because all PKCS#11 items are local and local security is
  assumed, these concerns are mainly about usability.

  In order to improve the user experience, applications that create
  PKCS#11 objects or otherwise label tokens, SHOULD normalize labels to
  NFC.  For the same reason PKCS#11 libraries, slots (token readers),
  and tokens SHOULD normalize their names to NFC.  When listing
  libraries, slots, tokens, or objects, an application SHOULD normalize
  their names to NFC.  When matching PKCS#11 URIs to libraries, slots,
  tokens, and/or objects, applications may use form-insensitive Unicode
  string comparison for matching, as the objects might pre-date these
  recommendations).

        I've created "Internationalization Considerations" section and
put the text above there after I slightly modified it.  I wanted to
mention CK_UTF8CHAR type so that it's clear what is discussed.

768     6.  Internationalization Considerations

770        The PKCS#11 specification does not specify a canonical form for
771        strings of characters of the CK_UTF8CHAR type.  This presents
the
772        usual false negative and false positive (aliasing) concerns that
773        arise when dealing with unnormalized strings.  Because all
PKCS#11
774        items are local and local security is assumed, these concerns
are
775        mainly about usability.

777        In order to improve the user experience, applications that
create
778        PKCS#11 objects or label tokens, SHOULD normalize labels to
NFC.  For
779        the same reason PKCS#11 libraries, slots (token readers), and
tokens
780        SHOULD normalize their names to NFC.  When listing PKCS#11
libraries,
781        slots, tokens, and/or objects, an application SHOULD normalize
their
782        names to NFC.  When matching PKCS#11 URIs to libraries, slots,
783        tokens, and/or objects, applications MAY use form-insensitive
Unicode
784        string comparison for matching, as those might pre-date these
785        recommendations.  See also Section 3.5.

        in section 3.5 on URI Matching Guidelines, I've added the
following as the last paragraph of the section (it was based on John's
note from his last email).  This paragraph might not be necessary there
and the first part could be moved to the I18N section but I think it's
good to put it to where attribute matching is discussed so that it is
not easily overlooked.

513        As noted in Section 6, the PKCS#11 specification is not clear
about
514        how to normalize UTF-8 encoded Unicode characters [RFC2279].
Those
515        who discover a need to use characters outside the ASCII
repertoire
516        should be cautious, conservative, and expend extra effort to be
sure
517        they know what they are doing and that failure to do so may
create
518        both operational and security risks.  It means that when
matching
519        UTF-8 string based attributes (see Table 1) with such
characters,
520        normalizing all UTF-8 strings before string comparison may be
the
521        only safe approach.  For example, for objects (keys) it means
that
522        PKCS#11 attribute search template would only contain attributes
that
523        are not UTF-8 strings and another pass through returned objects
is
524        then needed for UTF-8 string comparison after the normalization
is
525        applied.

Then later in the security considerations section, add something like:

  PKCS#11 does not authenticate devices to users; PKCS#11 only
  authenticates users to tokens.  Instead, local and physical security
  are demanded: the user must be in possession of their tokens, and
  system into whose slots the users' tokens are inserted must be
  secure.  As a result, the usual security considerations regarding
  normalization do not arise.  For the same reason, confusable script
  issues also do not arise.  Nonetheless, it is best to normalize to
  NFC all strings appearing in PKCS#11 API elements.

        I've added the following to the Security Considerations
section (again, slightly modified, I'd rather not use "PKCS#11" as
an alias for the specification):

807        The PKCS#11 specification does not provide means to authenticate
808        devices to users; it only allows to authenticate users to
tokens.
809        Instead, local and physical security are demanded: the user
must be
810        in possession of their tokens, and system into whose slots the
users'
811        tokens are inserted must be secure.  As a result, the usual
security
812        considerations regarding normalization do not arise.  For the
same
813        reason, confusable script issues also do not arise.
Nonetheless, it
814        is best to normalize to NFC all strings appearing in PKCS#11 API
815        elements.  See also Section 6.

        on top of that, I've added the following sentence to 3.6. PKCS#11
URI
Comparison section:

532        strictly avoiding false positives.  When working with UTF-8
strings
533        with characters outside the ASCII character sets, see important
534        caveats in Section 3.5 and Section 6.

        the attribute Table 1 now also states which attributes are
UTF-8 strings so that it's clear without consulting the spec.

        thank you, Jan.

--
Jan Pechanec <jan(_dot_)pechanec(_at_)oracle(_dot_)com>
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-- 
Jan Pechanec <jan(_dot_)pechanec(_at_)oracle(_dot_)com>