Mailing List Archive

On 3/2/23 7:21 PM, Christophe JAILLET wrote:
> Le 02/03/2023 à 16:10, ylavic@apache.org a écrit :
>> Author: ylavic
>> Date: Thu Mar  2 15:10:30 2023
>> New Revision: 1907980
>>
>> URL: http://svn.apache.org/viewvc?rev=1907980&view=rev
>> Log:
>> mod_proxy_uwsgi: Stricter backend HTTP response parsing/validation
>>
>>
>> Added:
>>      httpd/httpd/trunk/changes-entries/proxy_uwsgi_response_validation.txt
>> Modified:
>>      httpd/httpd/trunk/modules/proxy/mod_proxy_uwsgi.c
>>
>> Added: httpd/httpd/trunk/changes-entries/proxy_uwsgi_response_validation.txt
>> URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/changes-entries/proxy_uwsgi_response_validation.txt?rev=1907980&view=auto
>> ==============================================================================
>> --- httpd/httpd/trunk/changes-entries/proxy_uwsgi_response_validation.txt (added)
>> +++ httpd/httpd/trunk/changes-entries/proxy_uwsgi_response_validation.txt Thu Mar  2 15:10:30 2023
>> @@ -0,0 +1,2 @@
>> +  *) mod_proxy_uwsgi: Stricter backend HTTP response parsing/validation.
>> +     [Yann Ylavic]
>>
>> Modified: httpd/httpd/trunk/modules/proxy/mod_proxy_uwsgi.c
>> URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/modules/proxy/mod_proxy_uwsgi.c?rev=1907980&r1=1907979&r2=1907980&view=diff
>> ==============================================================================
>> --- httpd/httpd/trunk/modules/proxy/mod_proxy_uwsgi.c (original)
>> +++ httpd/httpd/trunk/modules/proxy/mod_proxy_uwsgi.c Thu Mar  2 15:10:30 2023
>> @@ -313,18 +313,16 @@ static int uwsgi_response(request_rec *r
>>       pass_bb = apr_brigade_create(r->pool, c->bucket_alloc);
>>         len = ap_getline(buffer, sizeof(buffer), rp, 1);
>> -
>>       if (len <= 0) {
>> -        /* oops */
>> +        /* invalid or empty */
>>           return HTTP_INTERNAL_SERVER_ERROR;
>>       }
>> -
>>       backend->worker->s->read += len;
>> -
>> -    if (len >= sizeof(buffer) - 1) {
>> -        /* oops */
>> +    if ((apr_size_t)len >= sizeof(buffer)) {
>
> Hi Yann,
>
> Why removing the -1?
>
> My understading is that it is there in case of:
>   uwsgi_response()
>     ap_getline()
>       ap_rgetline()
>         ap_fgetline_core()
>           code around cleanup:
>
> In this path, IIUC, sizeof(buffer) - 1 is returned.
> Can this happen?

I think ap_fgetline_core can only return a len of sizeof(buffer) - 1 when:

1. The line is really that long.
2. The line is longer, but then rv != APR_SUCCESS.

In case 1. all is fine and we should proceed the result.
In case 2. ap_getline will return sizeof(buffer).

Hence I think the change is correct.

Regards

Rüdiger

On Thu, Mar 2, 2023 at 8:22 PM Ruediger Pluem <rpluem@apache.org> wrote:
>
> On 3/2/23 7:21 PM, Christophe JAILLET wrote:
> > Le 02/03/2023 à 16:10, ylavic@apache.org a écrit :
> >> @@ -313,18 +313,16 @@ static int uwsgi_response(request_rec *r
> >> pass_bb = apr_brigade_create(r->pool, c->bucket_alloc);
> >> len = ap_getline(buffer, sizeof(buffer), rp, 1);
> >> -
> >> if (len <= 0) {
> >> - /* oops */
> >> + /* invalid or empty */
> >> return HTTP_INTERNAL_SERVER_ERROR;
> >> }
> >> -
> >> backend->worker->s->read += len;
> >> -
> >> - if (len >= sizeof(buffer) - 1) {
> >> - /* oops */
> >> + if ((apr_size_t)len >= sizeof(buffer)) {
> >
> > Hi Yann,
> >
> > Why removing the -1?
> >
> > My understading is that it is there in case of:
> > uwsgi_response()
> > ap_getline()
> > ap_rgetline()
> > ap_fgetline_core()
> > code around cleanup:
> >
> > In this path, IIUC, sizeof(buffer) - 1 is returned.
> > Can this happen?
>
> I think ap_fgetline_core can only return a len of sizeof(buffer) - 1 when:
>
> 1. The line is really that long.
> 2. The line is longer, but then rv != APR_SUCCESS.
>
> In case 1. all is fine and we should proceed the result.
> In case 2. ap_getline will return sizeof(buffer).
>
> Hence I think the change is correct.

Yes exactly, ap_fgetline_core() returns APR_ENOSPC if the buffer is
truncated, and ap_getline() returns sizeof(buffer).
This change avoids failing unnecessarily for a valid response line of
exactly sizeof(buffer)-1 bytes length.

Regards;
Yann.

>
> Regards
>
> Rüdiger
>