From aac59c116456f8ce617d5b218e7ee4f044f56e6c Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 17 Dec 2014 14:40:35 -0500 Subject: add basic dns record parsing functions MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit based on patch by Timo Teräs, with some corrections to bounds checking code and other minor changes. while they are borderline scope creep, the functions added are fairly small and are roughly the minimum code needed to use the results of the res_query API without re-implementing error-prone DNS packet parsing, and they are used in practice by some kerberos related software and possibly other things. at this time there is no intent to implement further nameser.h API functions. --- src/network/ns_parse.c | 171 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 171 insertions(+) create mode 100644 src/network/ns_parse.c (limited to 'src') diff --git a/src/network/ns_parse.c b/src/network/ns_parse.c new file mode 100644 index 00000000..3ff33a87 --- /dev/null +++ b/src/network/ns_parse.c @@ -0,0 +1,171 @@ +#define _BSD_SOURCE +#include +#include +#include +#include + +const struct _ns_flagdata _ns_flagdata[16] = { + { 0x8000, 15 }, + { 0x7800, 11 }, + { 0x0400, 10 }, + { 0x0200, 9 }, + { 0x0100, 8 }, + { 0x0080, 7 }, + { 0x0040, 6 }, + { 0x0020, 5 }, + { 0x0010, 4 }, + { 0x000f, 0 }, + { 0x0000, 0 }, + { 0x0000, 0 }, + { 0x0000, 0 }, + { 0x0000, 0 }, + { 0x0000, 0 }, + { 0x0000, 0 }, +}; + +unsigned ns_get16(const unsigned char *cp) +{ + return cp[0]<<8 | cp[1]; +} + +unsigned long ns_get32(const unsigned char *cp) +{ + return (unsigned)cp[0]<<24 | cp[1]<<16 | cp[2]<<8 | cp[3]; +} + +void ns_put16(unsigned s, unsigned char *cp) +{ + *cp++ = s>>8; + *cp++ = s; +} + +void ns_put32(unsigned long l, unsigned char *cp) +{ + *cp++ = l>>24; + *cp++ = l>>16; + *cp++ = l>>8; + *cp++ = l; +} + +int ns_initparse(const unsigned char *msg, int msglen, ns_msg *handle) +{ + int i, r; + + handle->_msg = msg; + handle->_eom = msg + msglen; + if (msglen < (2 + ns_s_max) * NS_INT16SZ) goto bad; + NS_GET16(handle->_id, msg); + NS_GET16(handle->_flags, msg); + for (i = 0; i < ns_s_max; i++) NS_GET16(handle->_counts[i], msg); + for (i = 0; i < ns_s_max; i++) { + if (handle->_counts[i]) { + handle->_sections[i] = msg; + r = ns_skiprr(msg, handle->_eom, i, handle->_counts[i]); + if (r < 0) return -1; + msg += r; + } else { + handle->_sections[i] = NULL; + } + } + if (msg != handle->_eom) goto bad; + handle->_sect = ns_s_max; + handle->_rrnum = -1; + handle->_msg_ptr = NULL; + return 0; +bad: + errno = EMSGSIZE; + return -1; +} + +int ns_skiprr(const unsigned char *ptr, const unsigned char *eom, ns_sect section, int count) +{ + const unsigned char *p = ptr; + int r; + + while (count--) { + r = dn_skipname(p, eom); + if (r < 0) goto bad; + if (r + 2 * NS_INT16SZ > eom - p) goto bad; + p += r + 2 * NS_INT16SZ; + if (section != ns_s_qd) { + if (NS_INT32SZ + NS_INT16SZ > eom - p) goto bad; + p += NS_INT32SZ; + NS_GET16(r, p); + if (r > eom - p) goto bad; + p += r; + } + } + return ptr - p; +bad: + errno = EMSGSIZE; + return -1; +} + +int ns_parserr(ns_msg *handle, ns_sect section, int rrnum, ns_rr *rr) +{ + int r; + + if (section < 0 || section >= ns_s_max) goto bad; + if (section != handle->_sect) { + handle->_sect = section; + handle->_rrnum = 0; + handle->_msg_ptr = handle->_sections[section]; + } + if (rrnum == -1) rrnum = handle->_rrnum; + if (rrnum < 0 || rrnum >= handle->_counts[section]) goto bad; + if (rrnum < handle->_rrnum) { + handle->_rrnum = 0; + handle->_msg_ptr = handle->_sections[section]; + } + if (rrnum > handle->_rrnum) { + r = ns_skiprr(handle->_msg_ptr, handle->_eom, section, rrnum - handle->_rrnum); + if (r < 0) return -1; + handle->_msg_ptr += r; + handle->_rrnum = rrnum; + } + r = ns_name_uncompress(handle->_msg, handle->_eom, handle->_msg_ptr, rr->name, NS_MAXDNAME); + if (r < 0) return -1; + handle->_msg_ptr += r; + if (2 * NS_INT16SZ > handle->_eom - handle->_msg_ptr) goto size; + NS_GET16(rr->type, handle->_msg_ptr); + NS_GET16(rr->rr_class, handle->_msg_ptr); + if (section != ns_s_qd) { + if (NS_INT32SZ + NS_INT16SZ > handle->_eom - handle->_msg_ptr) goto size; + NS_GET32(rr->ttl, handle->_msg_ptr); + NS_GET16(rr->rdlength, handle->_msg_ptr); + if (rr->rdlength > handle->_eom - handle->_msg_ptr) goto size; + rr->rdata = handle->_msg_ptr; + handle->_msg_ptr += rr->rdlength; + } else { + rr->ttl = 0; + rr->rdlength = 0; + rr->rdata = NULL; + } + handle->_rrnum++; + if (handle->_rrnum > handle->_counts[section]) { + handle->_sect = section + 1; + if (handle->_sect == ns_s_max) { + handle->_rrnum = -1; + handle->_msg_ptr = NULL; + } else { + handle->_rrnum = 0; + } + } + return 0; +bad: + errno = ENODEV; + return -1; +size: + errno = EMSGSIZE; + return -1; +} + +int ns_name_uncompress(const unsigned char *msg, const unsigned char *eom, + const unsigned char *src, char *dst, size_t dstsiz) +{ + int r; + r = dn_expand(msg, eom, src, dst, dstsiz); + if (r < 0) errno = EMSGSIZE; + return r; +} + -- cgit v1.2.1