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nfqws2: support uncompressed names in DNS answers

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bol-van
2026-02-23 09:32:45 +03:00
parent 59b3734643
commit d985bb316f
3 changed files with 51 additions and 21 deletions
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64
nfq2/desync.c
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@@ -1679,52 +1679,82 @@ static bool feed_dns_response(const uint8_t *a, size_t len)
if (!params.cache_hostname) return true;
// check of minimum header length and response flag
uint16_t k, off, dlen, qcount = a[4]<<8 | a[5], acount = a[6]<<8 | a[7];
uint16_t k, typ, off, dlen, qcount = a[4]<<8 | a[5], acount = a[6]<<8 | a[7];
char s_ip[INET6_ADDRSTRLEN];
const uint8_t *b = a, *p;
const uint8_t *e = b + len;
size_t nl;
char name[256] = "";
if (len<12 || !(a[2]&0x80)) return false;
if (!qcount || !acount || len<12 || !(a[2]&0x80)) return false;
a+=12; len-=12;
for(k=0;k<qcount;k++)
for(k=0,*name = 0 ; k<qcount ; k++)
{
if (*name) return false; // we do not support multiple queries with names
// remember original query name
if (!(p = dns_extract_name(a, b, e, name, sizeof(name)))) return false;
len -= p-a;
if ((len<4) || p[2] || p[3]!=1) return false;
typ = pntoh16(p);
// must be A or AAAA query. others are not interesting
if ((len<4) || p[0] || p[1]!=1 && p[1]!=28 || p[2] || p[3]!=1) return false;
if (typ!=1 && typ!=28)
{
DLOG("skipping DNS query type %u for '%s'\n", typ, name);
return false;
}
else
{
DLOG("DNS query type %u for '%s'\n", typ, name);
}
// skip type, class
a=p+4; len-=4;
}
if (!*name) return false;
for(k=0;k<acount;k++)
{
if (len<12) return false;
// 11 higher bits indicate pointer
if (len<12 || (*a & 0xC0)!=0xC0) return false;
dlen = a[10]<<8 | a[11];
if (len<(dlen+12)) return false;
if (a[4]==0 && a[5]==1 && a[2]==0) // IN class and higher byte of type = 0
if ((*a & 0xC0)==0xC0)
{
switch(a[3])
a+=2; len-=2;
}
else
{
// skip full name
while(*a)
{
// we do not support mixed names
if ((*a & 0xC0)==0xC0 || len<(*a + 11)) return false;
len-=*a+1;
a+=*a+1;
}
a++; len--;
}
dlen = a[8]<<8 | a[9];
if (len<(dlen+10)) return false;
if (a[2]==0 && a[3]==1) // IN class
{
typ = pntoh16(a);
switch(typ)
{
case 1: // A
if (dlen!=4) break;
if (params.debug && inet_ntop(AF_INET, a+12, s_ip, sizeof(s_ip)))
DLOG("DNS response : %s\n", s_ip);
ipcache_put_hostname((struct in_addr *)(a+12), NULL, name, false);
if (params.debug && inet_ntop(AF_INET, a+10, s_ip, sizeof(s_ip)))
DLOG("DNS response type %u : %s\n", typ, s_ip);
ipcache_put_hostname((struct in_addr *)(a+10), NULL, name, false);
break;
case 28: // AAAA
if (dlen!=16) break;
if (params.debug && inet_ntop(AF_INET6, a+12, s_ip, sizeof(s_ip)))
DLOG("DNS response : %s\n", s_ip);
ipcache_put_hostname(NULL, (struct in6_addr *)(a+12), name, false);
if (params.debug && inet_ntop(AF_INET6, a+10, s_ip, sizeof(s_ip)))
DLOG("DNS response type %u : %s\n", typ, s_ip);
ipcache_put_hostname(NULL, (struct in6_addr *)(a+10), name, false);
break;
default:
DLOG("skipping DNS response type %u\n", typ);
}
}
len -= 12+dlen; a += 12+dlen;
len -= 10+dlen; a += 10+dlen;
}
return true;
}