[Oisf-devel] libhtp - Normalization of query string

[Ivan Ristić]

On 19/06/2013 11:35, Anoop Saldanha wrote:
> On Wed, Jun 19, 2013 at 3:45 PM, Ivan Ristic <ivan.ristic at gmail.com> wrote:
>> On Tue, Jun 18, 2013 at 2:12 PM, Anoop Saldanha <anoopsaldanha at gmail.com> wrote:
>>> On Mon, Jun 17, 2013 at 6:40 PM, Ivan Ristic <ivan.ristic at gmail.com> wrote:
>>>> On Mon, Jun 17, 2013 at 9:18 AM, Anoop Saldanha <anoopsaldanha at gmail.com> wrote:
>>>>> While producing the normalized uri, what is the right way to
>>>>> generate the normalized query string? Can see 2 solutions -
>>>>>
>>>>>     1. Duplicate this code section from htp_unparse_uri_noencode( ) -
>>>>>
>>>>>         if (uri->query != NULL) {
>>>>>             bstr *query = bstr_dup(uri->query);
>>>>>             htp_uriencoding_normalize_inplace(query);
>>>>>             bstr_add_c_noex(r, "?");
>>>>>             bstr_add_noex(r, query);
>>>>>             bstr_free(query);
>>>>>         }
>>>>
>>>> I think this one is a better approach, although it may depend on
>>>> exactly how you define normalization.
>>>
>>> With htp_uriencoding_normalize_inplace( ) if it sees a %2d it would
>>> translate it as a '-'(hypen) using x2c, and then checks if it's a
>>> reserved character and post confirmation leaves it undecoded.  Is this
>>> the right behaviour?
>>
>> It depends. It's ambiguous in the spec, and some argue one way, some
>> another. Unfortunately, I didn't document my reasoning and so I will
>> need to go back and double-check.
>>
> 
> okay.
> 
> As an example, I have uris with query strings where %2d is not decoded
> if I use htp_uriencoding_normalize_inplace().  We are also using this
> function to decode username, password, fragment and hostname, so will
> have to check if we face the same issue with these.
> 
>>
>>> I would have preferred to use htp_decode_urlencoded_inplace(), but
>>> it's private and duplication would be a nuisance with all the
>>> reference to cfg.
>>
>> I don't think you can avoid the reference to cfg, because there are
>> many settings that control exactly how the decoding is done.
> 
> Right, which should also count as the reason why we can't use
> htp_uriencoding_normalize_inplace() for query decoding.
> 
>> There
>> isn't any one true way. I could create a public function removing the
>> reference to tx -- would you like that?
> 
> Yes, that would be helpful.
> 
> Before you push the commit for this, can I have a look at it to make
> sure that's what I want?

How about:

    htp_urldecode_inplace_ex(
        htp_decoder_cfg_t *cfg,
        bstr *input,
        uint64_t flags)?


>>> Btw the cfg associated with HTP_DECODER_URL_PATH applicable to both
>>> the path and the query part of the uri?
>>
>> HTP_DECODER_URL_PATH will be used for the path only,
>> HTP_DECODER_URLENCODED for parameters, either in the query string or
>> in the body. (I've just found one place when the incorrect cfg is
>> used. Will fix it now.)
>>
> 
> FYI, htp_uriencoding_normalize_inplace() has reference to
> HTP_DEOCER_URL_PATH cfg, and query decoding code calls
> htp_uriencoding_normalize_inplace().

You probably mean htp_decode_urlencoded_inplace()? I fixed that the
other day.

https://github.com/ironbee/libhtp/commit/c88d0a59bb00fc343747872b2be73692107f2b60


>>
>>>>
>>>>
>>>>>     2. Register htp_config_register_urlencoded_parser( ), and then
>>>>>           use the below code -
>>>>>
>>>>>         if (uri->query != NULL) {
>>>>>             bstr_add_c_noex(r, "?");
>>>>>             size_t tsize = htp_table_size(tx->request_params);
>>>>>             size_t i;
>>>>>             for (i = 0; i < tsize; i++) {
>>>>>                 htp_param_t *p =
>>>>>                     htp_table_get_index(tx->request_params, i, NULL);
>>>>>                 if (p == NULL || p->source != HTP_SOURCE_QUERY_STRING)
>>>>>                     continue;
>>>>>                 bstr_add_noex(r, p->name);
>>>>>                 if (bstr_len(p->value) != 0) {
>>>>>                     bstr_add_c_noex(r, "=");
>>>>>                     bstr_add_noex(r, p->value);
>>>>>                 }
>>>>>                 if (i != (tsize - 1))
>>>>>                     bstr_add_c_noex(r, "&");
>>>>>         }
>>>>>
>>>>>     Which of these 2 is the right solution?
>>>>>
> 
> 


-- 
Ivan