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Fix IPv4 address in replies to A or NS queries (github issue #38)
The destination field in struct query was changed from in_addr_t to struct sockaddr_storage, wihtout updating the functions sending it in src/dns.c. Only add extra A answer for NS queries if destination refers to an IPv4 address, and fail if trying to encode a reply to an A query if destination is not IPv4. This means NS requests received over IPv6 will not contain an address and A requests will be ignored, unless the -n option is used, or the www subdomain is requested which sets a fixed address (127.0.0.1).
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parent
d09c3e4f0b
commit
ec6a1ac308
53
src/dns.c
53
src/dns.c
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@ -299,21 +299,25 @@ int dns_encode_ns_response(char *buf, size_t buflen, struct query *q,
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putbyte(&p, 's');
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putshort(&p, topname); /* Name Server */
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/* Additional data (A-record of NS server) */
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CHECKLEN(12);
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putshort(&p, nsname); /* Name Server */
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putshort(&p, T_A); /* Type */
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putshort(&p, C_IN); /* Class */
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putlong(&p, 3600); /* TTL */
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putshort(&p, 4); /* Data length */
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/* Do we have an IPv4 address to send? */
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if (q->destination.ss_family == AF_INET) {
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struct sockaddr_in *dest = (struct sockaddr_in *) &q->destination;
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/* Additional data (A-record of NS server) */
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CHECKLEN(12);
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putshort(&p, nsname); /* Name Server */
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putshort(&p, T_A); /* Type */
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putshort(&p, C_IN); /* Class */
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putlong(&p, 3600); /* TTL */
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putshort(&p, 4); /* Data length */
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/* ugly hack to output IP address */
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ipp = (char *) &q->destination;
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CHECKLEN(4);
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putbyte(&p, *(ipp++));
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putbyte(&p, *(ipp++));
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putbyte(&p, *(ipp++));
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putbyte(&p, *ipp);
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/* ugly hack to output IP address */
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ipp = (char *) &dest->sin_addr.s_addr;
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CHECKLEN(4);
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putbyte(&p, *(ipp++));
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putbyte(&p, *(ipp++));
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putbyte(&p, *(ipp++));
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putbyte(&p, *ipp);
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}
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len = p - buf;
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return len;
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@ -323,12 +327,17 @@ int dns_encode_ns_response(char *buf, size_t buflen, struct query *q,
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* www.topdomain . Mostly same as dns_encode_ns_response() above */
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int dns_encode_a_response(char *buf, size_t buflen, struct query *q)
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{
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struct sockaddr_in *dest = (struct sockaddr_in *) &q->destination;
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HEADER *header;
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int len;
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short name;
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char *ipp;
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char *p;
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/* Check if we have an IPv4 address to send */
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if (q->destination.ss_family != AF_INET)
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return -1;
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if (buflen < sizeof(HEADER))
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return 0;
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@ -355,19 +364,19 @@ int dns_encode_a_response(char *buf, size_t buflen, struct query *q)
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/* Query section */
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putname(&p, buflen - (p - buf), q->name); /* Name */
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CHECKLEN(4);
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putshort(&p, q->type); /* Type */
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putshort(&p, C_IN); /* Class */
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putshort(&p, q->type); /* Type */
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putshort(&p, C_IN); /* Class */
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/* Answer section */
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CHECKLEN(12);
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putshort(&p, name); /* Name */
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putshort(&p, q->type); /* Type */
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putshort(&p, C_IN); /* Class */
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putlong(&p, 3600); /* TTL */
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putshort(&p, 4); /* Data length */
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putshort(&p, name); /* Name */
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putshort(&p, q->type); /* Type */
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putshort(&p, C_IN); /* Class */
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putlong(&p, 3600); /* TTL */
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putshort(&p, 4); /* Data length */
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/* ugly hack to output IP address */
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ipp = (char *) &q->destination;
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ipp = (char *) &dest->sin_addr.s_addr;
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CHECKLEN(4);
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putbyte(&p, *(ipp++));
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putbyte(&p, *(ipp++));
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@ -1549,7 +1549,9 @@ handle_ns_request(int dns_fd, struct query *q)
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/* If ns_ip set, overwrite destination addr with it.
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* Destination addr will be sent as additional record (A, IN) */
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struct sockaddr_in *addr = (struct sockaddr_in *) &q->destination;
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addr->sin_family = AF_INET;
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memcpy(&addr->sin_addr, &ns_ip, sizeof(ns_ip));
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q->dest_len = sizeof(*addr);
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}
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len = dns_encode_ns_response(buf, sizeof(buf), q, topdomain);
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@ -1577,15 +1579,23 @@ handle_a_request(int dns_fd, struct query *q, int fakeip)
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if (fakeip) {
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in_addr_t ip = inet_addr("127.0.0.1");
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struct sockaddr_in *addr = (struct sockaddr_in *) &q->destination;
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addr->sin_family = AF_INET;
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memcpy(&addr->sin_addr, &ip, sizeof(ip));
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q->dest_len = sizeof(*addr);
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} else if (ns_ip != INADDR_ANY) {
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/* If ns_ip set, overwrite destination addr with it.
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* Destination addr will be sent as additional record (A, IN) */
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struct sockaddr_in *addr = (struct sockaddr_in *) &q->destination;
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addr->sin_family = AF_INET;
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memcpy(&addr->sin_addr, &ns_ip, sizeof(ns_ip));
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q->dest_len = sizeof(*addr);
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}
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/* Give up if no IPv4 address known (when A request received over IPv6
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* and destination was not overwritten above) */
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if (q->destination.ss_family != AF_INET)
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return;
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len = dns_encode_a_response(buf, sizeof(buf), q);
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if (len < 1) {
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warnx("dns_encode_a_response doesn't fit");
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