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dns.c
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/* ------------------------------------------------------------------------------------------------------------------ */
/* NS-Warp - DNS responder/proxy */
/* ------------------------------------------------------------------------------------------------------------------ */
/*
* Copyright (c) 2021-2024, Mikhail Zakharov <zmey20000@yahoo.com>
*
* Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
* following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following
* disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and
* the following disclaimer in the documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/* -- DNS ----------------------------------------------------------------------------------------------------------- */
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include "dns.h"
#include "logfile.h"
#include "ns-warp.h"
#include "network.h"
/* ------------------------------------------------------------------------------------------------------------------ */
struct sockaddr_storage rev_addr(struct sockaddr_storage ip) {
/* Reverse sinX_addr to be used in PTR DNS lookups, e.g. 127.0.0.1 -> 1.0.0.127 */
struct sockaddr_storage sa;
uint32_t ipv6_quad;
if (SA_FAMILY(sa) == AF_INET)
((struct sockaddr_in *)&sa)->sin_addr.s_addr = htonl(((struct sockaddr_in *)&ip)->sin_addr.s_addr);
else {
#if defined(linux)
ipv6_quad = htonl(((struct sockaddr_in6 *)&ip)->sin6_addr.__in6_u.__u6_addr32[3]);
((struct sockaddr_in6 *)&sa)->sin6_addr.__in6_u.__u6_addr32[3] =
htonl(((struct sockaddr_in6 *)&ip)->sin6_addr.__in6_u.__u6_addr32[0]);
((struct sockaddr_in6 *)&sa)->sin6_addr.__in6_u.__u6_addr32[0] = ipv6_quad;
ipv6_quad = htonl(((struct sockaddr_in6 *)&ip)->sin6_addr.__in6_u.__u6_addr32[2]);
((struct sockaddr_in6 *)&sa)->sin6_addr.__in6_u.__u6_addr32[2] =
htonl(((struct sockaddr_in6 *)&ip)->sin6_addr.__in6_u.__u6_addr32[1]);
((struct sockaddr_in6 *)&sa)->sin6_addr.__in6_u.__u6_addr32[1] = ipv6_quad;
#else
ipv6_quad = htonl(((struct sockaddr_in6 *)&ip)->sin6_addr.__u6_addr.__u6_addr32[3]);
((struct sockaddr_in6 *)&sa)->sin6_addr.__u6_addr.__u6_addr32[3] =
htonl(((struct sockaddr_in6 *)&ip)->sin6_addr.__u6_addr.__u6_addr32[0]);
((struct sockaddr_in6 *)&sa)->sin6_addr.__u6_addr.__u6_addr32[0] = ipv6_quad;
ipv6_quad = htonl(((struct sockaddr_in6 *)&ip)->sin6_addr.__u6_addr.__u6_addr32[2]);
((struct sockaddr_in6 *)&sa)->sin6_addr.__u6_addr.__u6_addr32[2] =
htonl(((struct sockaddr_in6 *)&ip)->sin6_addr.__u6_addr.__u6_addr32[1]);
((struct sockaddr_in6 *)&sa)->sin6_addr.__u6_addr.__u6_addr32[1] = ipv6_quad;
#endif
}
return sa;
}
/* ------------------------------------------------------------------------------------------------------------------ */
char *reverse_ip(struct sockaddr_storage *ip, char *rev_ip) {
/* Reverse an IP address to be used as used as reverse lookup in PTR queries */
const char *rev_d = DNS_REV_LOOKUP_SUFFIX_IPV4;
struct sockaddr_storage sa;
if (!rev_ip) return NULL;
sa = rev_addr(*ip);
if (SA_FAMILY(sa) == AF_INET6) rev_d = DNS_REV_LOOKUP_SUFFIX_IPV6;
inet2str(&sa, rev_ip);
strcat(rev_ip, rev_d);
printl(LOG_VERB, "Reverse IP: [%s]", rev_ip);
return rev_ip;
}
/* ------------------------------------------------------------------------------------------------------------------ */
struct sockaddr_storage forward_ip(char *rev_ip) {
/* Make normal forward IP address from a reversed one */
char *suff = NULL;
struct sockaddr_storage sa;
char buf[HOST_NAME_MAX] = {0};
memset(&sa, 0, sizeof(sa));
SA_FAMILY(sa) = AF_INET;
((struct sockaddr_in *)&sa)->sin_addr.s_addr = INADDR_BROADCAST;
if (rev_ip) {
if ((suff = strstr(rev_ip, DNS_REV_LOOKUP_SUFFIX_IPV4))) {
strncpy(buf, rev_ip, suff - rev_ip);
if (!inet_pton(AF_INET, buf, &((struct sockaddr_in *)&sa)->sin_addr)) {
printl(LOG_VERB, "Corrupted IPv4 address: [%s]", buf);
}
} else {
if ((suff = strstr(rev_ip, DNS_REV_LOOKUP_SUFFIX_IPV6))) {
strncpy(buf, rev_ip, suff - rev_ip);
if (!inet_pton(AF_INET6, buf, &((struct sockaddr_in6 *)&sa)->sin6_addr))
printl(LOG_VERB, "Corrupted IPv6 address: [%s]", buf);
} else {
printl(LOG_VERB, "Corrupted IP address: [%s]", buf);
}
}
}
sa = rev_addr(sa);
printl(LOG_VERB, "Forward IP: [%s]", inet2str(&sa, buf));
return sa;
}
/* ------------------------------------------------------------------------------------------------------------------ */
int dns_reply_a(unsigned int id, unsigned char *dnsq_raw, int dnsq_siz, struct sockaddr_storage *ip, unsigned char *rbuf) {
/* Prepare both A and AAAA replies in *rbuf based on input data */
dns_header *dnsh;
dns_answer_ref *dnsa;
if (SA_FAMILY(*ip) != AF_INET && SA_FAMILY(*ip) != AF_INET6) {
printl(LOG_WARN, "dns_reply_a(): Skipping answer: Unknown address family: [%d] in reply IP", SA_FAMILY(*ip));
return 0;
}
/* Fill in the header */
dnsh = (dns_header *)rbuf;
dnsh->id = id;
dnsh->flags = 0x8085; /* Standard query response, No error */
dnsh->qdcount = 0x0100;
dnsh->ancount = 0x0100;
dnsh->nscount = 0x0000;
dnsh->arcount = 0x0000;
/* Add the query part */
memcpy(rbuf + sizeof(dns_header), dnsq_raw, dnsq_siz);
/* Add answer part */
dnsa = (dns_answer_ref *)(rbuf + sizeof(dns_header) + dnsq_siz);
dnsa->name_ref = 0x0CC0;
dnsa->type = SA_FAMILY(*ip) == AF_INET ? 0x0100 : 0x1C00;
dnsa->classr = 0x0100;
dnsa->ttl = 0x00000000;
dnsa->rdlength = 0x0400;
if (SA_FAMILY(*ip) == AF_INET) {
in_addr_t *rdata = (in_addr_t *)(rbuf + sizeof(dns_header) + dnsq_siz + sizeof(dns_answer_ref));
*rdata = S4_ADDR(*ip);
return sizeof(dns_header) + dnsq_siz + sizeof(dns_answer_ref) + sizeof(*rdata);
} else {
char *rdata = (char *)(rbuf + sizeof(dns_header) + dnsq_siz + sizeof(dns_answer_ref));
memcpy(rdata, S6_ADDR(*ip), 16);
return sizeof(dns_header) + dnsq_siz + sizeof(dns_answer_ref) + sizeof(*rdata);
}
return 0;
}
/* ------------------------------------------------------------------------------------------------------------------ */
int dns_reply_ptr(unsigned int id, unsigned char *dnsq_raw, int dnsq_siz, char *q_name, unsigned char *rbuf) {
dns_header *dnsh;
dns_answer_ref *dnsa;
char *s;
int sl = 0;
/* Fill in the header */
dnsh = (dns_header *)rbuf;
dnsh->id = id;
dnsh->flags = 0x8085; /* Standard query response, No error */
dnsh->qdcount = 0x0100;
dnsh->ancount = 0x0100;
dnsh->nscount = 0x0000;
dnsh->arcount = 0x0000;
/* Add the query part */
memcpy(rbuf + sizeof(dns_header), dnsq_raw, dnsq_siz);
/* Add answer part */
dnsa = (dns_answer_ref *)(rbuf + sizeof(dns_header) + dnsq_siz);
dnsa->name_ref = 0x0CC0;
dnsa->type = 0x0C00; /* PTR */
dnsa->classr = 0x0100;
dnsa->ttl = 0x00000000;
dnsa->rdlength = 0x0100; /* Count the final NULL, terminating rdata */
char *rdata = (char *)(rbuf + sizeof(dns_header) + dnsq_siz + sizeof(dns_answer_ref));
while ((s = strsep(&q_name, "."))) {
sl = strlen(s);
*rdata = sl;
rdata++;
strcpy(rdata, s);
rdata += sl;
dnsa->rdlength += htons(sl + 1);
}
return sizeof(dns_header) + dnsq_siz + sizeof(dns_answer_ref) + ntohs(dnsa->rdlength) + 1;
}
/* ------------------------------------------------------------------------------------------------------------------ */
int dns_reply_nfound(unsigned int id, unsigned int typ, unsigned char *dnsq_raw, int dnsq_siz, unsigned char *rbuf) {
/* Reply the name is not found */
dns_header *dnsh;
/* Fill in the header */
dnsh = (dns_header *)rbuf;
dnsh->id = id;
dnsh->flags = 0x8385; /* Standard query response, No such name */
dnsh->qdcount = 0x0100;
dnsh->ancount = 0x0000;
dnsh->nscount = 0x0000;
dnsh->arcount = 0x0000;
/* Add the query part */
memcpy(rbuf + sizeof(dns_header), dnsq_raw, dnsq_siz);
return sizeof(dns_header) + dnsq_siz;
}