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Check DNS reply source in udpresolve

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This commit is contained in:
Vladimir Dubrovin 2026-08-12 15:32:30 +03:00
parent 75021a2003
commit a43c95023d
1 changed files with 42 additions and 12 deletions
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54
src/resolve.c
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@ -3,6 +3,19 @@
struct nserver nservers[MAXNSERVERS] = {{{0},0}, {{0},0}, {{0},0}, {{0},0}, {{0},0}};
struct nserver authnserver;
static int dnsqmatch(const unsigned char *a, const unsigned char *b, int len){
int i;
for(i = 0; i < len; i++){
unsigned char c1 = a[i], c2 = b[i];
if(c1 >= 'A' && c1 <= 'Z') c1 += 'a' - 'A';
if(c2 >= 'A' && c2 <= 'Z') c2 += 'a' - 'A';
if(c1 != c2) return 1;
}
return 0;
}
uint32_t udpresolve(int af, unsigned char * name, unsigned char * value, uint32_t *retttl, struct clientparam* param, int makeauth){
@ -23,9 +36,12 @@ uint32_t udpresolve(int af, unsigned char * name, unsigned char * value, uint32_
SOCKET sock;
uint32_t ttl;
PROXYSOCKADDRTYPE addr;
PROXYSOCKADDRTYPE from;
PROXYSOCKADDRTYPE *sinsr, *sinsl;
int usetcp = 0;
unsigned short serial = 1;
unsigned char qbuf[300];
int qlen;
buf = b+2;
@ -92,6 +108,9 @@ uint32_t udpresolve(int af, unsigned char * name, unsigned char * value, uint32_
buf[len++] = (makeauth == 1)? 0x0c : (af==AF_INET6? 0x1c:0x01);/* PTR:host address */
buf[len++] = 0;
buf[len++] = 1; /* INET */
qlen = len - 12;
memcpy(qbuf, buf + 12, qlen);
if(usetcp){
buf-=2;
*(unsigned short*)buf = htons(len);
@ -104,30 +123,41 @@ uint32_t udpresolve(int af, unsigned char * name, unsigned char * value, uint32_
continue;
}
if(param) param->statscli64 += len;
len = sockrecvfrom(NULL, sock, (struct sockaddr *)sinsr, buf, 4096, conf.timeouts[DNS_TO]*1000);
len = sockrecvfrom(NULL, sock, (struct sockaddr *)&from, buf, 4096, conf.timeouts[DNS_TO]*1000);
if(len > 13 && usetcp){
unsigned short us;
us = ntohs(*(unsigned short*)buf);
len-=2;
buf+=2;
if(us > 4096 || us < len) len = 0;
else if(us > len){
if(sockrecvfrom(NULL, sock, (struct sockaddr *)&from, buf+len, us-len, conf.timeouts[DNS_TO]*1000) != us-len) len = 0;
else len = us;
}
}
so._shutdown(so.state, sock, SHUT_RDWR);
so._closesocket(so.state, sock);
if(len <= 13) {
continue;
}
if(param) param->statssrv64 += len;
if(usetcp){
unsigned short us;
us = ntohs(*(unsigned short*)buf);
len-=2;
buf+=2;
if(us > 4096 || us < len || (us > len && sockrecvfrom(NULL, sock, (struct sockaddr *)sinsr, buf+len, us-len, conf.timeouts[DNS_TO]*1000) != us-len)) {
continue;
}
if(!usetcp && (*SAFAMILY(&from) != *SAFAMILY(sinsr) ||
memcmp(SAADDR(&from), SAADDR(sinsr), SAADDRLEN(sinsr)) ||
*SAPORT(&from) != *SAPORT(sinsr))) {
continue; /* not from the server we asked */
}
if(*(unsigned short *)buf != serial)continue;
if((na = buf[7] + (((unsigned short)buf[6])<<8)) < 1) {
return 0;
}
if(!(buf[2] & 0x80)) continue; /* not a response */
nq = buf[5] + (((unsigned short)buf[4])<<8);
if (nq != 1) {
continue; /* we did only 1 request */
}
if(len < 12 + qlen || dnsqmatch(buf + 12, qbuf, qlen)) {
continue; /* question does not match the query */
}
if((na = buf[7] + (((unsigned short)buf[6])<<8)) < 1) {
return 0;
}
for(k = 13; k<len && buf[k]; k++) {
}
k++;