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BUG: maxfwd module incorrectly decrements header twice if the max-forwards… #3511

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BUG: maxfwd module incorrectly decrements header twice if the max-forwards… #3511

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22 changes: 11 additions & 11 deletions modules/maxfwd/maxfwd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -138,33 +138,33 @@ static int w_process_maxfwd_header(struct sip_msg* msg, int* mval)
int val;
str mf_value;

val=is_maxfwd_present(msg, &mf_value);
val = is_maxfwd_present(msg, &mf_value);
switch (val) {
/* header not found */
case -1:
if (add_maxfwd_header( msg, *mval)!=0)
goto error;
if (add_maxfwd_header(msg, *mval) !=0)
return -2;
return 2;
/* error */
case -2:
goto error;
/* found */
return -2;
/* found but zero */
case 0:
return -1;
/* found and greater than zero */
default:
if (val>max_limit){
if (val > max_limit) {
LM_DBG("value %d decreased to %d\n", val, max_limit);
val = max_limit+1;
val = max_limit + 1;
}
if ( decrement_maxfwd(msg, val, &mf_value)!=0 ) {

if (decrement_maxfwd(msg, val, &mf_value) != 0) {
LM_ERR("decrement failed!\n");
goto error;
return -2;
}
}

return 1;
error:
return -2;
}


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59 changes: 32 additions & 27 deletions modules/maxfwd/mf_funcs.c
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Renamed the macros from MAXWD to MAXFWD also some of the changes here are whitespace changes to be consistent

Original file line number Diff line number Diff line change
Expand Up @@ -38,63 +38,68 @@
#define MF_HDR "Max-Forwards: "
#define MF_HDR_LEN (sizeof(MF_HDR) - 1)

/* do a tricky thing and keep the parsed value of MAXFWD hdr incremented
* by one in order to make difference between 0 (not set)
* and 0 (zero value) - bogdan */
#define IS_MAXWD_STORED(_msg_) \
#define IS_MAXFWD_STORED(_msg_) \
((_msg_)->maxforwards->parsed)
#define STORE_MAXWD_VAL(_msg_,_val_) \
(_msg_)->maxforwards->parsed = ((void*)(long)((_val_)+1))
#define FETCH_MAXWD_VAL(_msg_) \
(((int)(long)(_msg_)->maxforwards->parsed)-1)
#define STORE_MAXFWD_VAL(_msg_,_val_) \
(_msg_)->maxforwards->parsed = ((void*)(long)((_val_)))
#define FETCH_MAXFWD_VAL(_msg_) \
(((int)(long)(_msg_)->maxforwards->parsed))

/* looks for the MAX FORWARDS header
returns the its value, -1 if is not present or -2 for error */
int is_maxfwd_present( struct sip_msg* msg , str *foo)
returns the its value, -1 if is not present or -2 for error or 0 for present */
int is_maxfwd_present(struct sip_msg* msg, str *mf_value)
{
int x, err;
int parsed_val, err;

/* lookup into the message for MAX FORWARDS header*/
if ( !msg->maxforwards ) {
if ( parse_headers( msg , HDR_MAXFORWARDS_F, 0 )==-1 ){
LM_ERR("parsing MAX_FORWARD header failed!\n");
if (!msg->maxforwards) {
if (parse_headers(msg , HDR_MAXFORWARDS_F, 0) == -1){
LM_ERR("parsing Max-Forwards header failed!\n");
return -2;
}

if (!msg->maxforwards) {
LM_DBG("max_forwards header not found!\n");
LM_DBG("Max-Forwards header not found!\n");
return -1;
}
} else if (IS_MAXWD_STORED(msg)) {
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The else/if is removed here in favour of an if after this is so that we can do the trimlen in one place just before checking if IS_MAXFWD_STORED which it will be when using sipmsg_validate assuming it is non zero value so we trim and then check and retrieve the value

trim_len( foo->len , foo->s , msg->maxforwards->body );
return FETCH_MAXWD_VAL(msg);
}

/* if header is present, trim to get only the string containing numbers */
trim_len( foo->len , foo->s , msg->maxforwards->body );
trim_len(mf_value->len , mf_value->s, msg->maxforwards->body);

/* even if the parsed is 0 because it's a null pointer or a zero value
* it doesn't matter and we can assume it's not stored and just parse the body
*/
if (IS_MAXFWD_STORED(msg)) {
return FETCH_MAXFWD_VAL(msg);
}

/* convert from string to number */
x = str2s( foo->s,foo->len,&err);
if (err){
LM_ERR("unable to parse the max forwards number\n");
parsed_val = str2s(mf_value->s, mf_value->len, &err);
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Assume in this scenario that IS_MAXFWD_STORED failed because either we don't have a value in the parsed field because maxfwds module is the first instance of setting this value or that sipmsgops has not validated the SIP headers so we parse the body, we can only get here if the header has been parsed and if it is actually zero we can just return it

if (err) {
LM_ERR("unable to parse the Max-Forwards value\n");

return -2;
}

/* store the parsed values */
STORE_MAXWD_VAL(msg, x);
LM_DBG("value = %d \n",x);
return x;
STORE_MAXFWD_VAL(msg, parsed_val);
LM_DBG("value = %d \n", parsed_val);

return parsed_val;
}



int decrement_maxfwd( struct sip_msg* msg , int x, str *s)
int decrement_maxfwd( struct sip_msg* msg, int x, str *s)
{
int i;

/* decrement the value */
x--;

/* update the stored value */
STORE_MAXWD_VAL(msg, x);
STORE_MAXFWD_VAL(msg, x);

/* rewriting the max-fwd value in the message (buf and orig) */
for(i = s->len - 1; i >= 0; i--) {
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