diff options
Diffstat (limited to 'smtpd/unpack_dns.c')
| -rw-r--r-- | smtpd/unpack_dns.c | 300 |
1 files changed, 300 insertions, 0 deletions
diff --git a/smtpd/unpack_dns.c b/smtpd/unpack_dns.c new file mode 100644 index 00000000..974d5727 --- /dev/null +++ b/smtpd/unpack_dns.c @@ -0,0 +1,300 @@ +/* $OpenBSD: unpack_dns.c,v 1.1 2018/01/06 07:57:53 sunil Exp $ */ + +/* + * Copyright (c) 2011-2014 Eric Faurot <eric@faurot.net> + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ + +#include "includes.h" + +#ifdef HAVE_ARPA_NAMESER_COMPAT_H +#include <arpa/nameser_compat.h> +#endif +#include <arpa/inet.h> + +#include <string.h> + +#include "unpack_dns.h" + +static int unpack_data(struct unpack *, void *, size_t); +static int unpack_u16(struct unpack *, uint16_t *); +static int unpack_u32(struct unpack *, uint32_t *); +static int unpack_inaddr(struct unpack *, struct in_addr *); +static int unpack_in6addr(struct unpack *, struct in6_addr *); +static int unpack_dname(struct unpack *, char *, size_t); + +void +unpack_init(struct unpack *unpack, const char *buf, size_t len) +{ + unpack->buf = buf; + unpack->len = len; + unpack->offset = 0; + unpack->err = NULL; +} + +int +unpack_header(struct unpack *p, struct dns_header *h) +{ + if (unpack_data(p, h, HFIXEDSZ) == -1) + return (-1); + + h->flags = ntohs(h->flags); + h->qdcount = ntohs(h->qdcount); + h->ancount = ntohs(h->ancount); + h->nscount = ntohs(h->nscount); + h->arcount = ntohs(h->arcount); + + return (0); +} + +int +unpack_query(struct unpack *p, struct dns_query *q) +{ + unpack_dname(p, q->q_dname, sizeof(q->q_dname)); + unpack_u16(p, &q->q_type); + unpack_u16(p, &q->q_class); + + return (p->err) ? (-1) : (0); +} + +int +unpack_rr(struct unpack *p, struct dns_rr *rr) +{ + uint16_t rdlen; + size_t save_offset; + + unpack_dname(p, rr->rr_dname, sizeof(rr->rr_dname)); + unpack_u16(p, &rr->rr_type); + unpack_u16(p, &rr->rr_class); + unpack_u32(p, &rr->rr_ttl); + unpack_u16(p, &rdlen); + + if (p->err) + return (-1); + + if (p->len - p->offset < rdlen) { + p->err = "too short"; + return (-1); + } + + save_offset = p->offset; + + switch (rr->rr_type) { + + case T_CNAME: + unpack_dname(p, rr->rr.cname.cname, sizeof(rr->rr.cname.cname)); + break; + + case T_MX: + unpack_u16(p, &rr->rr.mx.preference); + unpack_dname(p, rr->rr.mx.exchange, sizeof(rr->rr.mx.exchange)); + break; + + case T_NS: + unpack_dname(p, rr->rr.ns.nsname, sizeof(rr->rr.ns.nsname)); + break; + + case T_PTR: + unpack_dname(p, rr->rr.ptr.ptrname, sizeof(rr->rr.ptr.ptrname)); + break; + + case T_SOA: + unpack_dname(p, rr->rr.soa.mname, sizeof(rr->rr.soa.mname)); + unpack_dname(p, rr->rr.soa.rname, sizeof(rr->rr.soa.rname)); + unpack_u32(p, &rr->rr.soa.serial); + unpack_u32(p, &rr->rr.soa.refresh); + unpack_u32(p, &rr->rr.soa.retry); + unpack_u32(p, &rr->rr.soa.expire); + unpack_u32(p, &rr->rr.soa.minimum); + break; + + case T_A: + if (rr->rr_class != C_IN) + goto other; + unpack_inaddr(p, &rr->rr.in_a.addr); + break; + + case T_AAAA: + if (rr->rr_class != C_IN) + goto other; + unpack_in6addr(p, &rr->rr.in_aaaa.addr6); + break; + default: + other: + rr->rr.other.rdata = p->buf + p->offset; + rr->rr.other.rdlen = rdlen; + p->offset += rdlen; + } + + if (p->err) + return (-1); + + /* make sure that the advertised rdlen is really ok */ + if (p->offset - save_offset != rdlen) + p->err = "bad dlen"; + + return (p->err) ? (-1) : (0); +} + +ssize_t +dname_expand(const unsigned char *data, size_t len, size_t offset, + size_t *newoffset, char *dst, size_t max) +{ + size_t n, count, end, ptr, start; + ssize_t res; + + if (offset >= len) + return (-1); + + res = 0; + end = start = offset; + + for (; (n = data[offset]); ) { + if ((n & 0xc0) == 0xc0) { + if (offset + 2 > len) + return (-1); + ptr = 256 * (n & ~0xc0) + data[offset + 1]; + if (ptr >= start) + return (-1); + if (end < offset + 2) + end = offset + 2; + offset = start = ptr; + continue; + } + if (offset + n + 1 > len) + return (-1); + + /* copy n + at offset+1 */ + if (dst != NULL && max != 0) { + count = (max < n + 1) ? (max) : (n + 1); + memmove(dst, data + offset, count); + dst += count; + max -= count; + } + res += n + 1; + offset += n + 1; + if (end < offset) + end = offset; + } + if (end < offset + 1) + end = offset + 1; + + if (dst != NULL && max != 0) + dst[0] = 0; + if (newoffset) + *newoffset = end; + return (res + 1); +} + +char * +print_dname(const char *_dname, char *buf, size_t max) +{ + const unsigned char *dname = _dname; + char *res; + size_t left, n, count; + + if (_dname[0] == 0) { + (void)strlcpy(buf, ".", max); + return buf; + } + + res = buf; + left = max - 1; + for (n = 0; dname[0] && left; n += dname[0]) { + count = (dname[0] < (left - 1)) ? dname[0] : (left - 1); + memmove(buf, dname + 1, count); + dname += dname[0] + 1; + left -= count; + buf += count; + if (left) { + left -= 1; + *buf++ = '.'; + } + } + buf[0] = 0; + + return (res); +} + +static int +unpack_data(struct unpack *p, void *data, size_t len) +{ + if (p->err) + return (-1); + + if (p->len - p->offset < len) { + p->err = "too short"; + return (-1); + } + + memmove(data, p->buf + p->offset, len); + p->offset += len; + + return (0); +} + +static int +unpack_u16(struct unpack *p, uint16_t *u16) +{ + if (unpack_data(p, u16, 2) == -1) + return (-1); + + *u16 = ntohs(*u16); + + return (0); +} + +static int +unpack_u32(struct unpack *p, uint32_t *u32) +{ + if (unpack_data(p, u32, 4) == -1) + return (-1); + + *u32 = ntohl(*u32); + + return (0); +} + +static int +unpack_inaddr(struct unpack *p, struct in_addr *a) +{ + return (unpack_data(p, a, 4)); +} + +static int +unpack_in6addr(struct unpack *p, struct in6_addr *a6) +{ + return (unpack_data(p, a6, 16)); +} + +static int +unpack_dname(struct unpack *p, char *dst, size_t max) +{ + ssize_t e; + + if (p->err) + return (-1); + + e = dname_expand(p->buf, p->len, p->offset, &p->offset, dst, max); + if (e == -1) { + p->err = "bad domain name"; + return (-1); + } + if (e < 0 || e > MAXDNAME) { + p->err = "domain name too long"; + return (-1); + } + + return (0); +} |