[SR-Users] decode_mime_type error
Daniel-Constantin Mierla
miconda at gmail.com
Fri Aug 19 12:54:39 CEST 2011
Hello,
On 8/19/11 2:09 AM, Bucur Marius wrote:
> Hi Jijo,
>
>
> In my opinion, decode_mime_type is broken, and parse_accept_body does not work as expected.
> For example, this is a valid accept header:
>
> accept: text/plain;param=",some value".
>
> but the parse_accept_body will return -1 because the first return value of decode_mime_type is ",some value\"". The second invocation will think "some value\"" is a mime type, which obviously isn't.
>
> I must say I never saw such an accept header, but the standard permits it.
> Indeed, a quick fix would be to ignore the return code when comma is found.
> This must be done for other functions that call decode_mime_type like has_body(mime) in textops.
>
> This is just my opinion, but I think this solution is a bit hackish since the convention, the "promise" that decode_mime_type should respect is to return a non-NULL, non-end pointer ONLY when there are more mime types in the body. And it doesn't.
> A lot of functions that call it rely on this. I think it is easier/more elegant to fix the bug in the decode_mime_type then to change the function convention in all callers.
> Also, this might work for most callers, but parse_accept_body will still be buggy, as I explained in the example above.
this has to be fixed, the safest way not to forget about this is to open
an issue on bug tracker.
Cheers,
Daniel
>
> Cheers,
> Marius
>
> ________________________________
> From: Jijo<realjijo at gmail.com>
> To: Bucur Marius<bucur_marius_ovidiu at yahoo.com>
> Sent: Thursday, August 18, 2011 10:48 AM
> Subject: Re: [SR-Users] decode_mime_type error
>
>
> Hi Marius,
>
> Right, the same function is used for Accept and Content-Type.
>
> I don't think there is any change required for parsing Accept. In case of Accept the function decode_mime_type is called in a loop until it find all the media types. On the returning from decode_mime_type(), the main function parse_accept_xxx() checks the pointer is 'comma' or not. if its comma, then the function decode_mime_type called again and find the remaining media types. So i think the existing implementation for Parsing Accept is fine.
>
> The only change required here is not return error for comma while parsing the Content-Type.
>
> Thanks
> Jijo
>
>
> On Thu, Aug 18, 2011 at 12:32 PM, Bucur Marius<bucur_marius_ovidiu at yahoo.com> wrote:
>
> Hello Jijo,
>> You are right, multiple mime-types are not allowed. But it seems like decode_mime_type had the purpose of also parsing the Accept header:
>>
>> Accept: text/html, image/jpeg, multipart
>>
>> hence the search for commas :).
>> The only function that uses this feature and calls decode_mime_type in a loop is parse_accept_body. The other functions that call decode_mime_type just fail when returning ret != end, and since multiple mime types in content-type are not allowed the behavior is fine.
>> The bad thing is the Accept header can have mime parameters too (which can contain comma).
>>
>> Accept = "Accept" HCOLON [ accept-range *(COMMA accept-range) ]
>> accept-range = media-range *(SEMI accept-param)
>> media-range = ( "*/*" / ( m-type SLASH "*" ) / ( m-type SLASH m-subtype ) ) *( SEMI m-parameter )
>>
>> So I think the best thing would be to change decode_mime_type so that it does a more thorough parsing (e.g. check for parameter) hence a parameter value can contain commas (only if quoted).
>>
>>
>> Cheers,
>>
>> Marius
>> ________________________________
>> From: Jijo<realjijo at gmail.com>
>> To: Bucur Marius<bucur_marius_ovidiu at yahoo.com>; SIP Router - Kamailio (OpenSER) and SIP Express Router (SER) - Users Mailing List<sr-users at lists.sip-router.org>
>> Sent: Thursday, August 18, 2011 8:04 AM
>> Subject: Re: [SR-Users] decode_mime_type error
>>
>>
>>
>> Hi Marius,
>>
>> Thanks for the response.. I checked the other functions, but they don't have the check for ret !=end, but they check the pointer and if it is comma then loop through again until it find all the media types.
>>
>> As per the RFC3261 multiple media-types are not supoorted in the Content-Type. So I'm not sure why the author used comma to determine multiple media types . Probably just followed like Route or Record-Route headers..??
>>
>> Content-Type = ( "Content-Type" / "c" ) HCOLON media-type
>> media-type = m-type SLASH m-subtype *(SEMI m-parameter)
>> m-type = discrete-type / composite-type
>> discrete-type = "text" / "image" / "audio" / "video"
>> / "application" / extension-token
>> composite-type = "message" / "multipart" / extension-token
>>
>> Record-Route = "Record-Route" HCOLON rec-route *(COMMA rec-route)
>>
>> Thanks
>> Jijo
>>
>>
>>
>> On Thu, Aug 18, 2011 at 2:23 AM, Bucur Marius<bucur_marius_ovidiu at yahoo.com> wrote:
>>
>> Hello Jijo,
>>> It seems like the decode_mime_type is a somehow broken. The comma is very well allowed in boundary, as you said. The BNF specified in RFC2046 permits it.
>>> But, the decode_mime_type function ignores everything coming after comma. More than that, it notifies the function caller that this content type has multiple mime types.
>>> I think the author of the function thought of something like:
>>>
>>> Content-Type: text/html, image/jpeg // very weird, though
>>>
>>> This is wrong, hence the comma can be in a parameter (like in your case).
>>> I think the best fix, as you said is to remove that check, hence a non-NULL return value doesn't mean anything (that the content type has multiple mime types).
>>> Another fix is to write a "good" decode_mime_type, that checks if the comma is inside a parameter. I don't know if effort is worth it.
>>>
>>> One thing we need to do is to check if there are any functions in Kamailio that call decode_mime_type and also perform this check (ret != end).
>>>
>>> Cheers,
>>> Marius
>>>
>>>
>>> ________________________________
>>> From: Jijo<realjijo at gmail.com>
>>> To: sr-users at lists.sip-router.org; sr-dev at lists.sip-router.org
>>> Sent: Wednesday, August 17, 2011 10:54 AM
>>> Subject: [SR-Users] decode_mime_type error
>>>
>>>
>>>
>>> Hi All,
>>>
>>> The function parse_content_type_hdr() is failing in decode_mime_type() when Content-Type parameter "boundary" has value comma as below. The error message is "ERROR:parse_content_type_hdr: CONTENT_TYPE hdr contains "
>>> "more then one mime type :-(!
>>>
>>> Content Type Header is as below, It works fine if the boundary value is without comma.
>>>
>>> Content-Type: multipart/mixed;boundary=",AW"
>>>
>>> The parse_content_type_hdr() is failing in the following code,
>>>
>>> ret = decode_mime_type(msg->content_type->body.s, end ,&mime);
>>> if (ret==0)
>>> goto error;
>>> if (ret!=end) {
>>>
>>> LOG(L_INFO,"ERROR:parse_content_type_hdr: CONTENT_TYPE hdr contains "
>>> "more then one mime type :-(!\n");
>>> goto error ;
>>> }
>>>
>>> I thought of fixing this issue by commenting the code for condition ret !=end. I'm not sure why we we need that check, as mime variable has the information to process the content.
>>>
>>> Please let me know if you see any impact.
>>>
>>> Thanks
>>> Jijo
>>>
>>>
>>>
>>>
>>>
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>
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--
Daniel-Constantin Mierla -- http://www.asipto.com
Kamailio Advanced Training, Oct 10-13, Berlin: http://asipto.com/u/kat
http://linkedin.com/in/miconda -- http://twitter.com/miconda
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