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137 lines
7.1 KiB
137 lines
7.1 KiB
6 years ago
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#define _BSD_SOURCE
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#include <errno.h>
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#include <stddef.h>
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#include <resolv.h>
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#include <arpa/nameser.h>
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static unsigned long ns_get32(const unsigned char *cp)
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{
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return (unsigned)cp[0]<<24 | cp[1]<<16 | cp[2]<<8 | cp[3];
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}
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static void ns_put16(unsigned s, unsigned char *cp)
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{
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*cp++ = s>>8;
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*cp++ = s;
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}
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static void ns_put32(unsigned long l, unsigned char *cp)
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{
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*cp++ = l>>24;
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*cp++ = l>>16;
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*cp++ = l>>8;
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*cp++ = l;
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}
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static int dn_skipname(const unsigned char *s, const unsigned char *end) { const unsigned char *p; for (p=s; p<end; p++) if (!*p) return p-s+1; else if (*p>=192) if (p+1<end) return p-s+2; else break; return -1; }
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static int ns_skiprr(const unsigned char *ptr, const unsigned char *eom, ns_sect section, int count) {
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const unsigned char *p = ptr; int r;
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while (count--) {
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r = dn_skipname(p, eom); if (r < 0) goto bad;
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if (r + 2 * NS_INT16SZ > eom - p) goto bad; p += r + 2 * NS_INT16SZ; if (section != ns_s_qd) {
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if (NS_INT32SZ + NS_INT16SZ > eom - p) goto bad;
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p += NS_INT32SZ;
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NS_GET16(r, p);
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if (r > eom - p) goto bad; p += r;
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}
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}
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return p - ptr;
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bad: errno = EMSGSIZE; return -1;
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}
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static int ns_initparse(const unsigned char *msg, int msglen, ns_msg *handle)
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{
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int i, r;
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handle->_msg = msg;
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handle->_eom = msg + msglen;
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if (msglen < (2 + ns_s_max) * NS_INT16SZ) goto bad;
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NS_GET16(handle->_id, msg);
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NS_GET16(handle->_flags, msg);
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for (i = 0; i < ns_s_max; i++) NS_GET16(handle->_counts[i], msg);
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for (i = 0; i < ns_s_max; i++) {
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if (handle->_counts[i]) {
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handle->_sections[i] = msg;
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r = ns_skiprr(msg, handle->_eom, i, handle->_counts[i]);
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if (r < 0) return -1;
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msg += r;
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} else {
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handle->_sections[i] = NULL;
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}
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}
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if (msg != handle->_eom) goto bad;
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handle->_sect = ns_s_max;
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handle->_rrnum = -1;
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handle->_msg_ptr = NULL;
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return 0;
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bad:
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errno = EMSGSIZE;
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return -1;
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}
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static int ns_name_uncompress(const unsigned char *msg, const unsigned char *eom,
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const unsigned char *src, char *dst, size_t dstsiz)
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{
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int r;
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r = dn_expand(msg, eom, src, dst, dstsiz);
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if (r < 0) errno = EMSGSIZE;
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return r;
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}
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static int ns_parserr(ns_msg *handle, ns_sect section, int rrnum, ns_rr *rr)
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{
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int r;
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if (section < 0 || section >= ns_s_max) goto bad;
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if (section != handle->_sect) {
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handle->_sect = section;
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handle->_rrnum = 0;
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handle->_msg_ptr = handle->_sections[section];
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}
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if (rrnum == -1) rrnum = handle->_rrnum;
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if (rrnum < 0 || rrnum >= handle->_counts[section]) goto bad;
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if (rrnum < handle->_rrnum) {
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handle->_rrnum = 0;
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handle->_msg_ptr = handle->_sections[section];
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}
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if (rrnum > handle->_rrnum) {
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r = ns_skiprr(handle->_msg_ptr, handle->_eom, section, rrnum - handle->_rrnum);
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if (r < 0) return -1;
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handle->_msg_ptr += r;
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handle->_rrnum = rrnum;
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}
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r = ns_name_uncompress(handle->_msg, handle->_eom, handle->_msg_ptr, rr->name, NS_MAXDNAME);
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if (r < 0) return -1;
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handle->_msg_ptr += r;
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if (2 * NS_INT16SZ > handle->_eom - handle->_msg_ptr) goto size;
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NS_GET16(rr->type, handle->_msg_ptr);
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NS_GET16(rr->rr_class, handle->_msg_ptr);
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if (section != ns_s_qd) {
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if (NS_INT32SZ + NS_INT16SZ > handle->_eom - handle->_msg_ptr) goto size;
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NS_GET32(rr->ttl, handle->_msg_ptr);
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NS_GET16(rr->rdlength, handle->_msg_ptr);
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if (rr->rdlength > handle->_eom - handle->_msg_ptr) goto size;
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rr->rdata = handle->_msg_ptr;
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handle->_msg_ptr += rr->rdlength;
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} else {
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rr->ttl = 0;
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rr->rdlength = 0;
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rr->rdata = NULL;
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}
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handle->_rrnum++;
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if (handle->_rrnum > handle->_counts[section]) {
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handle->_sect = section + 1;
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if (handle->_sect == ns_s_max) {
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handle->_rrnum = -1;
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handle->_msg_ptr = NULL;
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} else {
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handle->_rrnum = 0;
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}
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}
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return 0;
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bad:
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errno = ENODEV;
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return -1;
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size:
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errno = EMSGSIZE;
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return -1;
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}
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