Re: squid rewriter in reverse proxy mode

Great!

Note of warning: strncat is not a very friendly function.. the count
does NOT include the terminating \0 added after the last copied
character.

  strncat(buf, "123456789ABCDEF", 8);

will write 9 bytes to the end of buf.. The 8 characters 1-9 and then
the terminating \0.

So your code will overwrite 1 byte after the buffer with \0 if log_url
+ tag > MAX_URL.

The person who specified the C functions strncpy and strncat must have
been high on some strange mushroms or something.. The way these two
functions is specified is a almost 100% guarantee they will be used
wrongly at all times as their behaviour is nowhere near what is
expected by most programmers..

Regards
Henrik

On Wednesday 23 October 2002 10.41, KRATKY, Andrej wrote:
> Hello Henrik,
>
> thank You for the help. Adjustment seems to be working now:
>
> ##############################################################
> # client_side.c - clientRedirectDone
> ##############################################################
>
> static void
> clientRedirectDone(void *data, char *result)
> {
> char new_log_uri[MAX_URL];
> clientHttpRequest *http = data;
> request_t *new_request = NULL;
> request_t *old_request = http->request;
> debug(33, 5) ("clientRedirectDone: '%s' result=%s\n",
> http->uri, result ? result : "NULL");
> assert(http->redirect_state == REDIRECT_PENDING);
> http->redirect_state = REDIRECT_DONE;
> if (result) {
> http_status status = atoi(result);
> if (status == 301 || status == 302) {
> char *t = result;
> if ((t = strchr(result, ':')) != NULL) {
> http->redirect.status = status;
> http->redirect.location = xstrdup(t + 1);
> } else {
> debug(33, 1) ("clientRedirectDone: bad input:
> %s\n", result); }
> }
> // Hack to keep URL note in log not in outgoing URL
> if (NULL!=strstr(result,"|")) {
> strncpy(new_log_uri,http->log_uri,MAX_URL);
>
> strncat(new_log_uri,strstr(result,"|"),MAX_URL-strlen(new_log_uri))
>; *strstr(result,"|")='\0';
> safe_free(http->log_uri);
> http->log_uri = xstrdup(new_log_uri);
> }
> // Hack END [Andrej 23.10.2002]
> if (strcmp(result, http->uri))
> new_request = urlParse(old_request->method, result);
> }
>
> Regards
>
> Andrej
>
> -----Original Message-----
> From: Henrik Nordström [mailto:hno@squid-cache.org]
> Sent: Tuesday, October 22, 2002 8:07 PM
> To: KRATKY, Andrej
> Cc: Squid Dev
> Subject: Re: squid rewriter in reverse proxy mode
>
>
> Signal 6 is segmentation violation. Most likely you are overwriting
> memory.
>
> Yep.. you do not ensure there is sufficient space in log_uri. This
> is allocated just large enought to fit the logged URL with no extra
> headroom for later modifications of the string. Also you have
> broken the if (valid) code flow.. (missing curly brakets)
>
> The correct code for updating http->log_uri while processing a
> request reads
>
> safe_free(http->log_uri);
> http->log_uri = xstrdup(the_new_url);
>
> And should be done in clientRedirectDone (client_side.c) where all
> the other parsing of redirector results take place.
>
> Regards
> Henrik
>
> KRATKY, Andrej wrote:
> > Hello Henrik,
> >
> > as seen in devel.squid-cache.org, you are responsible for reverse
> > proxy functionality enhancements. I am using squid in reverse
> > proxy mode with own rewriter and need an enhancement which would
> > add an info into access log from external rewriter program. So I
> > would like to ask you kindly for a help.
> >
> > Example:
> > - input URL (to externel rewriter):
> > http://www.something.com/abcd.cgi?ab=1 - output URL (from
> > externel rewriter):
> > http://www2.something.com/abcd.cgi?ab=1|my_additional_info
> >
> > The part starting from '|' should be together with input URL
> > written into access log and output URL without part behind '|'
> > should be requested from the given server (www2). The adjustment
> > I added into redirector.c is coloured in added source.
> >
> > It seems to be working, but after few requests squid goes down
> > with signal 6: Oct 22 16:48:50 ev2 squid[15893]: Squid Parent:
> > child process 15895 exited due to signal 6 Oct 22 16:48:53 ev2
> > squid[15893]: Squid Parent: child process 15934 started
> >
> > Would you have a minute to help me resolve this problem?
> >
> > Thanx for a reply
> >
> > With Best Regards
> >
> > Andrej Kratky
> >
> >
> >
> > ##############################################################
> > # redirect.c - redirectHandleReply()
> > ##############################################################
> >
> > static void
> > redirectHandleReply(void *data, char *reply)
> > {
> > redirectStateData *r = data;
> > int valid;
> > char *t;
> > debug(29, 5) ("redirectHandleRead: {%s}\n", reply ? reply :
> > "<NULL>"); if (reply) {
> > if ((t = strchr(reply, ' ')))
> > *t = '\0';
> > if (*reply == '\0')
> > reply = NULL;
> > }
> > valid = cbdataValid(r->data);
> > cbdataUnlock(r->data);
> >
> > if (valid)
> > // Hack to keep URL note in log not in outgoing URL
> > if (NULL!=strstr(reply,"|")) {
> > strncat(((clientHttpRequest
> > *)(r->data))->log_uri,strstr(reply,"|"),(MAX_URL-5-strlen(((clien
> >tHttpReque st *)(r->data))->log_uri))); *strstr(reply,"|")='\0';
> > }
> > // Hack END [Andrej 21.10.2002]
> > r->handler(r->data, reply);
> > redirectStateFree(r);
> > }
Received on Wed Oct 23 2002 - 15:58:41 MDT