Re: Apache HTTPD: Read POST request body and set response header

[harshil fadia <hartz_2004@xxxxxxxxxxxxxxxxxxxxx>]

@Eric,

Let me read that what you have suggested. My problem is, the POST request coming is not a login form but it is un-parsable JSON string (application/x-ndjson). I am using some C string function to extract that part from request and setting it in the response header as part of my C code. But as is said, actual response body is lost by using SetHandler.

@Anthony,

You are right, that is just typo on my post Anthony. Actual code/config is good and compiled successfully. I am also able to set response header but my problem is that I am using SetHandler directive and that way I am getting actual response from server. Probably request is getting hijacked by SetHandler directive.

So what should be right way to trigger my C code which can set response header but also continue its routine flow to go to backend server and get actual response body, is the question.

*Thank you for responses*

Regards

Harshil

On Monday, 11 May, 2020, 02:19:34 pm GMT-4, Antony G <agiatr@xxxxxxxxx.invalid> wrote:

Hello Harshil Fadia,

 

Just to be sure that the below are just typing errors.

 

1) In the util_read  procedure, the statement return rc; is outside the brackets

 

And

 

2) You have different name in the MODULE DEFINITION (regiter_hooks) and in the name of the procedure (register_hooks)

 

module AP_MODULE_DECLARE_DATA readbody_module = { 

    STANDARD20_MODULE_STUFF,

    NULL, /*Per-directory configuration handler */

    NULL, /*Merge handler for per-directory configurations */

    NULL, /*Per-server configuration handler */

    NULL, /*Merge handler for per-server configurations */

    NULL,

    regiter_hooks /*Our hook registering function */

};

static void register_hooks(apr_pool_t *pool)

 

Regards

 

From: harshil fadia <hartz_2004@xxxxxxxxx.INVALID>
Sent: Monday, May 11, 2020 8:30 PM
To: users@xxxxxxxxxxxxxxxx
Subject: [users@httpd] Apache HTTPD: Read POST request body and set response header

 

How do I implement below requirement? Please help..

 

Read POST request body >> Take out some data from request body >> Set particular response header attribute based on request attribute >> Send response back to client

 

 

What I have tried to do so far is wrote Apache module in C, read the Post body and set response header. I am calling my custom module using SetHandler so I am losing the original server response and response becomes null. Where as, what I want to have is the actual server response to be sent to client and additionally I append one more parameter in response header.

 

1. httpd.conf

LoadModule example_module    /usr/lib64/httpd/modules/mycustommodule.so

 

<VirtualHost HOSTNAME:80>

  <Location /elasticsearch/_msearch>

        SetHandler readbody-handler #calling my custom module

  </Location>

  

  #My KIBANA application is running on 5601 on same machine

  ProxyPass        / http://localhost:5601/ 

  ProxyPassReverse / http://localhost:5601/

 

</VirtualHost>

 

 

2. My custom C module 

module AP_MODULE_DECLARE_DATA readbody_module = { 

    STANDARD20_MODULE_STUFF,

    NULL, /*Per-directory configuration handler */

    NULL, /*Merge handler for per-directory configurations */

    NULL, /*Per-server configuration handler */

    NULL, /*Merge handler for per-server configurations */

    NULL,

    regiter_hooks /*Our hook registering function */

};

static void register_hooks(apr_pool_t *pool)

{

    ap_hook_handler(readbody_handler, NULL, NULL, -10);

}

static int readbody_handler(request_rec *r)

{

    const char *buffer;

    if (!r->handler || strcmp(r->handler, "readbody-handler")) return (DECLINED);

    if (util_read(r, &buffer) == OK) //reading the body and assigning it into buffer

    {

        char s[2] = ":";

        char s2[2] = "\"";

        char *indexname;

        indexname = strtok(buffer, s);

        indexname = strtok(NULL, s);

        indexname = strtok(indexname, s2);

        indexname = strtok(NULL, s2);

        apr_table_setn(r->headers_out, "IndexPattern", indexname); //setting up response header

    }

    return OK;

}

static int util_read(request_rec *r, const char **rbuf)

{

    int rc;

    if ((rc = ap_setup_client_block(r, REQUEST_CHUNKED_ERROR)) != OK)

    {

        return rc;

    }

    if (ap_should_client_block(r))

    {

        char argsbuffer[HUGE_STRING_LEN];

        int rsize, len_read, rpos = 0;

        long length = r->remaining;

        *rbuf = apr_pcalloc(r->pool, length + 1);

        while ((len_read = ap_get_client_block(r, argsbuffer, sizeof(argsbuffer))) > 0)

        {

            if ((rpos + len_read) > length)

            {

                rsize = length - rpos;

            }

            else

            {

                rsize = len_read;

            }

            memcpy((char*) *rbuf + rpos, argsbuffer, rsize);

            rpos += rsize;

        }

    }

}

    return rc;

 

Regards,

Harshil Fadia