Code review request, 8020842 IDN do not throw IAE when hostname ends with a trailing dot

[Xuelei Fan]

Please review the new update:

http://cr.openjdk.java.net./~xuelei/8020842/webrev.01/

With this update, "com." is valid (return "com."); "." and
"example..com" are invalid.  And IAE will be thrown for invalid IDN.

Thanks,
Xuelei

On 8/7/2013 10:18 PM, Michael McMahon wrote:
> On 07/08/13 15:13, Xuelei Fan wrote:
>> On 8/7/2013 10:05 PM, Michael McMahon wrote:
>>> Resolvers seem to accept queries using trailing dots.
>>>
>>> eg nslookup www.oracle.com.
>>>
>>> or InetAddress.getByName("www.oracle.com.");
>>>
>>> The part of RFC3490 quoted below seems to me to be saying
>>> that the empty label implied by the trailing dot is not regarded
>>> as a label so that you don't end up calling toAscii() or toUnicode()
>>> with an empty string. I don't think it's saying the trailing dot can't
>>> be there.
>>>
>> It makes sense.
>>
>> What's your preference to return for IDN.toASCII("www.oracle.com."),
>> "www.oracle.com." or "www.oracle.com"? The current returned value is
>> "www.oracle.com".  I would like to reserve the behavior in this update.
> 
> My opinion is to keep it as at present ie. "www.oracle.com."
> 
> Michael
> 
>> I think we are on same page soon.
>>
>> Thanks,
>> Xuelei
>>
>>> Michael
>>>
>>> On 07/08/13 13:44, Xuelei Fan wrote:
>>>> On 8/7/2013 12:06 AM, Matthew Hall wrote:
>>>>> Trailing dots are allowed in plain DNS (thus almost surely in IDN),
>>>>> and the single dot represents the root zone. So you have to be
>>>>> careful making this sort of change to check the DNS RFCs first.
>>>> That's the first question we need to answer, whether IDN allow tailling
>>>> dots ("com."), zero-length root label ("."), and zero-length label ("",
>>>> for example ""example..com")?
>>>>
>>>> Per the specification of IDN.toASCII():
>>>> =======================================
>>>> "ToASCII operation can fail. ToASCII fails if any step of it fails. If
>>>> ToASCII operation fails, an IllegalArgumentException will be thrown. In
>>>> this case, the input string should not be used in an internationalized
>>>> domain name.
>>>>
>>>> A label is an individual part of a domain name. The original ToASCII
>>>> operation, as defined in RFC 3490, only operates on a single label.
>>>> This
>>>> method can handle both label and entire domain name, by assuming that
>>>> labels in a domain name are always separated by dots. ...
>>>>
>>>> Throws IllegalArgumentException - if the input string doesn't
>>>> conform to
>>>> RFC 3490 specification"
>>>>
>>>> Per the specification of RFC 3490:
>>>> ==================================
>>>> [section 2]
>>>> "A label is an individual part of a domain name.  Labels are usually
>>>>    shown separated by dots; for example, the domain name
>>>>    "www.example.com" is composed of three labels: "www", "example", and
>>>>    "com".  (The zero-length root label described in [STD13], which can
>>>>    be explicit as in "www.example.com." or implicit as in
>>>>    "www.example.com", is not considered a label in this
>>>> specification.)"
>>>>
>>>> "An "internationalized label" is a label to which the ToASCII
>>>>    operation (see section 4) can be applied without failing (with the
>>>>    UseSTD3ASCIIRules flag unset).  ...
>>>>    Although most Unicode characters can appear in
>>>>    internationalized labels, ToASCII will fail for some input strings,
>>>>    and such strings are not valid internationalized labels."
>>>>
>>>> "An "internationalized domain name" (IDN) is a domain name in which
>>>>    every label is an internationalized label."
>>>>
>>>> [Section 4.1]
>>>> "ToASCII consists of the following steps:
>>>>
>>>>    ...
>>>>
>>>>    8. Verify that the number of code points is in the range 1 to 63
>>>>         inclusive."
>>>>
>>>>
>>>> Here are the questions:
>>>> 1. whether "example..com" is an valid IDN?
>>>>      As dot is used as label separators, there are three labels,
>>>> "example", "", "com".  Per RFC 3490, "" is not a valid label. Hence,
>>>> "example..com" is not a valid IDN.
>>>>
>>>>      We need to address the issue in IDN.
>>>>
>>>> 2. whether "xyz." is an valid IDN?
>>>>      It's an gray area, I think. We can treat the trailing "." as root
>>>> label, or a label separator.
>>>>      If the trailing "." is treated as label separator, "xyz." is
>>>> invalid
>>>> per RFC 3490.
>>>>      if the trailing "." is treated as root label, what's the expected
>>>> return value of IDN.toASCII("xyz.")?  I think the return value can be
>>>> either "xyz." or "xyz".  The current implementation returns "xyz".
>>>>
>>>>      We may need not to update the implementation if tailing "." is
>>>> treated as root label.
>>>>
>>>> 3. whether "." is an valid IDN?
>>>>      It's an gray area again, I think.
>>>>      As above, if the trailing "." is treated as root label, I think
>>>> the
>>>> return value can be either "." or "".  The current implementation
>>>> throws
>>>> a StringIndexOutOfBoundsException.
>>>>
>>>>      However, what empty domain name ("") really means?  I would
>>>> prefer to
>>>> return "." for "." instead.
>>>>
>>>>      We need to address the issue in IDN.
>>>>
>>>>
>>>> Here comes the solution, the IDN.toASCII() returns:
>>>> 1. "." for ".";
>>>> 2. "xyz" for "xyz.";
>>>> 3. IAE for "example..com".
>>>>
>>>> Does it make sense?
>>>>
>>>> Thanks,
>>>> Xuelei
>>>>
>>>>
>>>> On 8/7/2013 1:35 AM, Michael McMahon wrote:
>>>>> I don't really understand the reason for the restriction in
>>>>> SNIHostName
>>>>> But, I guess that is where it should be enforced if it is required.
>>>>>
>>>>> Michael.
>>>>>
>>>>> On 06/08/13 17:43, Dmitry Samersoff wrote:
>>>>>> Xuelei,
>>>>>>
>>>>>> . (dot) is perfectly valid domain name and it means root domain so
>>>>>> com.
>>>>>> is valid domain name as well.
>>>>>>
>>>>>> It thinks to me that in context of methods your change we should
>>>>>> ignore
>>>>>> trailing dots, rather than throw exception.
>>>>>>
>>>>>> -Dmitry
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 2013-08-06 15:44, Xuelei Fan wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> Please review the bug fix to strict the illegal input checking in
>>>>>>> IDN.
>>>>>>>
>>>>>>> webrev: http://cr.openjdk.java.net./~xuelei/8020842/webrev.00/
>>>>>>>
>>>>>>> Here is two test cases, which are expected to get IAE.
>>>>>>>
>>>>>>> Case 1:
>>>>>>> String host = IDN.toASCII(".", IDN.USE_STD3_ASCII_RULES);
>>>>>>> Exception in thread "main"
>>>>>>> java.lang.StringIndexOutOfBoundsException:
>>>>>>> String index out of range: 0
>>>>>>>            at java.lang.StringBuffer.charAt(StringBuffer.java:204)
>>>>>>>            at java.net.IDN.toASCIIInternal(IDN.java:279)
>>>>>>>            at java.net.IDN.toASCII(IDN.java:118)
>>>>>>>
>>>>>>> Case 2:
>>>>>>> String host = IDN.toASCII("com.", IDN.USE_STD3_ASCII_RULES);
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Xuelei
>>>>>>>
>