diff options
Diffstat (limited to 'usr.sbin/smtpd/dns.c')
| -rw-r--r-- | usr.sbin/smtpd/dns.c | 189 |
1 files changed, 189 insertions, 0 deletions
diff --git a/usr.sbin/smtpd/dns.c b/usr.sbin/smtpd/dns.c new file mode 100644 index 00000000000..08cabed9813 --- /dev/null +++ b/usr.sbin/smtpd/dns.c @@ -0,0 +1,189 @@ +/* + * Copyright (c) 2008 Gilles Chehade <gilles@openbsd.org> + * + * 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 <sys/types.h> +#include <sys/socket.h> +#include <sys/queue.h> +#include <sys/tree.h> +#include <sys/time.h> + +#include <netinet/in.h> +#include <arpa/inet.h> +#include <arpa/nameser.h> + +#include <err.h> +#include <event.h> +#include <netdb.h> +#include <resolv.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <sysexits.h> +#include <unistd.h> + +#include "smtpd.h" + +struct mxrecord { + char hostname[MAXHOSTNAMELEN]; + u_int16_t priority; +}; + +static void mxsort(struct mxrecord *, size_t); +size_t getmxbyname(char *, char ***); + + +/* bubble sort MX records by priority */ +static void +mxsort(struct mxrecord *array, size_t len) +{ + u_int32_t i; + u_int32_t j; + struct mxrecord store; + + for (i = j = 0; i < len - 1; ++i) { + for (j = i + 1; j < len; ++j) { + if (array[i].priority > array[j].priority) { + store = array[i]; + array[i] = array[j]; + array[j] = store; + } + } + } +} + +size_t +getmxbyname(char *name, char ***result) +{ + union { + u_int8_t bytes[PACKETSZ]; + HEADER header; + } answer; + u_int32_t i, j; + int ret; + u_int8_t *sp; + u_int8_t *endp; + u_int8_t *ptr; + u_int16_t qdcount; + u_int8_t expbuf[PACKETSZ]; + u_int16_t type; + u_int16_t n; + u_int16_t priority, tprio; + size_t mxnb; + struct mxrecord mxarray[MXARRAYSIZE]; + size_t chunklen; + + ret = res_query(name, C_IN, T_MX, (u_int8_t *)&answer.bytes, + sizeof answer); + if (ret == -1) + return 0; + + /* sp stores start of dns packet, + * endp stores end of dns packet, + */ + sp = (u_int8_t *)&answer.bytes; + endp = sp + ret; + + /* skip header */ + ptr = sp + HFIXEDSZ; + + for (qdcount = ntohs(answer.header.qdcount); + qdcount--; + ptr += ret + QFIXEDSZ) { + ret = dn_skipname(ptr, endp); + if (ret == -1) + return 0; + } + + mxnb = 0; + for (; ptr < endp;) { + memset(expbuf, 0, sizeof expbuf); + ret = dn_expand(sp, endp, ptr, expbuf, sizeof expbuf); + if (ret == -1) + break; + ptr += ret; + + GETSHORT(type, ptr); + ptr += sizeof(u_int16_t) + sizeof(u_int32_t); + GETSHORT(n, ptr); + + if (type != T_MX) { + ptr += n; + continue; + } + + GETSHORT(priority, ptr); + ret = dn_expand(sp, endp, ptr, expbuf, sizeof expbuf); + if (ret == -1) + return 0; + ptr += ret; + + if (mxnb < sizeof(mxarray) / sizeof(struct mxrecord)) { + if (strlcpy(mxarray[mxnb].hostname, expbuf, + MAXHOSTNAMELEN) >= MAXHOSTNAMELEN) + return 0; + mxarray[mxnb].priority = priority; + if (tprio < priority) + tprio = priority; + } + else { + for (i = j = 0; + i < sizeof(mxarray) / sizeof(struct mxrecord); + ++i) { + if (tprio < mxarray[i].priority) { + tprio = mxarray[i].priority; + j = i; + } + } + + if (mxarray[j].priority > priority) { + if (strlcpy(mxarray[j].hostname, expbuf, + MAXHOSTNAMELEN) >= MAXHOSTNAMELEN) + return 0; + mxarray[j].priority = priority; + } + } + ++mxnb; + } + + if (mxnb == 0) + return 0; + + if (mxnb > sizeof(mxarray) / sizeof(struct mxrecord)) + mxnb = sizeof(mxarray) / sizeof(struct mxrecord); + + /* Rearrange MX records by priority */ + mxsort((struct mxrecord *)&mxarray, mxnb); + + chunklen = 0; + for (i = 0; i < mxnb; ++i) + chunklen += strlen(mxarray[i].hostname) + 1; + chunklen += ((mxnb + 1) * sizeof(char *)); + + *result = calloc(1, chunklen); + if (*result == NULL) { + err(1, "calloc"); + } + + ptr = (u_int8_t *)*result + (mxnb + 1) * sizeof(char *); + for (i = 0; i < mxnb; ++i) { + strlcpy(ptr, mxarray[i].hostname, MAXHOSTNAMELEN); + (*result)[i] = ptr; + ptr += strlen(mxarray[i].hostname) + 1; + } + (*result)[i] = NULL; + + return mxnb; +} |