[netmod] escapes - WAS: [Netconf] [Technical Errata Reported] RFC6536 (3862)

On 10 Jan 2014, at 14:58, Jernej Tuljak <jernej.tuljak@mg-soft.si> wrote:

> If this is true, then it is RFC6020 that needs a clarification on this. Namely, that the "special character" which follows a backslash need not be special and that it does not represent an escape sequence in such a case.
> 
>   Within a double-quoted string (enclosed within " "), a backslash
>   character introduces a special character, which depends on the
>   character that immediately follows the backslash:
> 
>    \n      new line
>    \t      a tab character
>    \"      a double quote
>    \\      a single backslash
> 
> My reading is that a backslash starts a YANG escape sequence and may therefore be removed during string dequoting. A "\*" ends up as *, which is not equivalent to '\*’.

In XSD regular expressions, which are also used by YANG, it is an error if a backslash plus something is not defined as an escape sequence. So I think YANG should behave the same for double-quoted string, i.e. a backslash followed by something else than the four characters listed above should be flagged as an error (“illegal escape”).

Lada

> 
> Please move this discussion over to NETMOD it that's the case.
> 
> Jernej
> 
> Dne 10.1.2014 14:40, piše Martin Bjorklund:
>> Hi,
>> 
>> This errata should be rejected.  "\*" is equvalent to '\*'.  \* in a
>> double quoted string is not an escape sequence, which means that the
>> characters are interpreted literally, i.e. the two characters \
>> followed by *.
>> 
>> The same goes for errata 3863.
>> 
>> /martin
>> 
>> RFC Errata System <rfc-editor@rfc-editor.org> wrote:
>>> The following errata report has been submitted for RFC6536,
>>> "Network Configuration Protocol (NETCONF) Access Control Model".
>>> 
>>> --------------------------------------
>>> You may review the report below and at:
>>> http://www.rfc-editor.org/errata_search.php?rfc=6536&eid=3862
>>> 
>>> --------------------------------------
>>> Type: Technical
>>> Reported by: Jernej Tuljak <jernej.tuljak@mg-soft.com>
>>> 
>>> Section: 3.5.2.
>>> 
>>> Original Text
>>> -------------
>>>      typedef matchall-string-type {
>>>        type string {
>>>          pattern "\*";
>>>        }
>>>        description
>>>          "The string containing a single asterisk '*' is used
>>>           to conceptually represent all possible values
>>>           for the particular leaf using this data type.";
>>>      }
>>> 
>>> Corrected Text
>>> --------------
>>>      typedef matchall-string-type {
>>>        type string {
>>>          pattern '\*';
>>>        }
>>>        description
>>>          "The string containing a single asterisk '*' is used
>>>           to conceptually represent all possible values
>>>           for the particular leaf using this data type.";
>>>      }
>>> 
>>> Notes
>>> -----
>>> As per RFC6020, Section 6.1.3., a backslash within a double-quoted
>>> string introduces a special character. The only valid escape sequences
>>> inside a double-quoted YANG string are: \n, \t, \" and \. As \* is not
>>> a valid escape sequence, a single quoted string should be used to
>>> specify the offending pattern statement's argument. The quotes could
>>> also be omitted.
>>> 
>>> Instructions:
>>> -------------
>>> This errata is currently posted as "Reported". If necessary, please
>>> use "Reply All" to discuss whether it should be verified or
>>> rejected. When a decision is reached, the verifying party (IESG)
>>> can log in to change the status and edit the report, if necessary.
>>> 
>>> --------------------------------------
>>> RFC6536 (draft-ietf-netconf-access-control-07)
>>> --------------------------------------
>>> Title : Network Configuration Protocol (NETCONF) Access Control Model
>>> Publication Date    : March 2012
>>> Author(s)           : A. Bierman, M. Bjorklund
>>> Category            : PROPOSED STANDARD
>>> Source              : Network Configuration
>>> Area                : Operations and Management
>>> Stream              : IETF
>>> Verifying Party     : IESG
>>> 
> 
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