nginx - get value of the header - x_forwarded_for in Nginx module (Naxsi)

[Marcin Kozlowski]

Still have few questions. Help would be great

Beginner in writing NGINX modules

Have this question

1) How do I create array, add element to it and than create a hashtable
from it.

Below I try to achieve it:

NX_LOG_DEBUG(_debug_whitelist_heavy,
NGX_LOG_EMERG, cf, 0,
               "finalizing hashtables array %i",  dlc->pass_rules->nelts);

headers_ar = ngx_array_create(cf->pool, dlc->pass_rules->nelts,
sizeof(ngx_hash_key_t));



if (headers_ar) {
    NX_LOG_DEBUG(_debug_readconf,  NGX_LOG_EMERG, cf, 0,
               "headers array %i",headers_ar->nelts);

2) Why headers_ar has 0 elemets

nginx: [emerg] finalizing hashtables array 6 in /etc/nginx/nginx.conf:124
nginx: [emerg] headers array 0 in /etc/nginx/nginx.conf:124



3) I later want to build hashtable based on this array:

    dlc->passr_headers_hash =  (ngx_hash_t*) ngx_pcalloc(cf->pool,
sizeof(ngx_hash_t));
    hash_init.hash = dlc->passr_headers_hash;
    hash_init.name = "passr_headers_hash";



    if (ngx_hash_init(&hash_init, (ngx_hash_key_t*) headers_ar->elts,
                      headers_ar->nelts) != NGX_OK) {
      ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "$HEADERS hashtable init
failed"); /* LCOV_EXCL_LINE */
      return (NGX_ERROR); /* LCOV_EXCL_LINE */
    }

    else {
      NX_LOG_DEBUG(_debug_whitelist, NGX_LOG_EMERG, cf, 0, "$HEADERS
hashtable init successed %d !",
                         dlc->passr_headers_hash->size);
    }



4) Can somebody post simple code that

a) creates array
b) pushes one IP
c) create hashtable from it

Thanks,


On Sat, Dec 28, 2019 at 3:36 PM Marcin Kozlowski <marcinguy at gmail.com>
wrote:

> Ignore my last post.
>
> My error.
>
> Thanks,
>
> On Fri, Dec 27, 2019 at 11:42 PM Marcin Kozlowski <marcinguy at gmail.com>
> wrote:
>
>> Thanks. Almost got my modifications to NAXSI ready.
>>
>> But currently have a blocker with getting just the X-Forwarded-for IP
>>
>> The code below:
>>
>> ngx_uint_t n;
>> ngx_table_elt_t **h;
>> ngx_array_t a;
>> a = req->headers_in.x_forwarded_for;
>> n = a.nelts;
>> h = a.elts;
>>
>>
>> for (i = 0; i<n; i++) {
>>    ngx_log_error(NGX_LOG_ERR, req->connection->log,
>>               0, "x_forwarded_for: %s", h[i]->value.data);
>> }
>>
>> gets a String with several IP (i.e client, server, request etc)
>>
>> Tried to parse the string using strtok(), interating through it .... but
>> it segfaults. I guess I am missing some NGINX module knowledge.
>>
>> How to properly get first string up to first "," from the
>> h[i]->value.data using NGINX functions/types or other correct way to do it.
>>
>> Thanks,
>>
>>
>>
>>
>>
>> On Wed, Dec 25, 2019 at 12:17 PM Ruslan Ermilov <ru at nginx.com> wrote:
>>
>>> On Tue, Dec 24, 2019 at 08:00:26PM +0100, Marcin Kozlowski wrote:
>>> > Thanks.
>>> >
>>> > Works. For the reference, this is the code I used:
>>> >
>>> >   ngx_uint_t n;
>>> >   ngx_table_elt_t **h;
>>> >   ngx_array_t a;
>>> >   a = req->headers_in.x_forwarded_for;
>>> >   n = a.nelts;
>>> >   h = a.elts;
>>> >
>>> >
>>> >   for (i = 0; i<n; i++) {
>>> >     ngx_log_error(NGX_LOG_ERR, req->connection->log,
>>> >               0, "x_forwarded_for: %s", h[i]->value.data);
>>> >   }
>>> >
>>> > BTW What would be the best practice in NGINX NASIX module or any other
>>> > module to load a file with hundreds entries of IPs (hashmap, or what
>>> > structure would be best?) which should be whitelisted later for
>>> comparison
>>> > in NASIX module logic. Those IP should never be blocked by NAXSI.
>>> >
>>> > When should I load this file in memory, in which component
>>> > /module/function/step?
>>> >
>>> > Links to some guides/sample code would be also appreciated.
>>> >
>>> > Thanks,
>>>
>>> http://nginx.org/en/docs/http/ngx_http_geo_module.html
>>> _______________________________________________
>>> nginx-devel mailing list
>>> nginx-devel at nginx.org
>>> http://mailman.nginx.org/mailman/listinfo/nginx-devel
>>>
>>
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