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-rw-r--r--smtpd/dns.c379
1 files changed, 379 insertions, 0 deletions
diff --git a/smtpd/dns.c b/smtpd/dns.c
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index 00000000..a3107e89
--- /dev/null
+++ b/smtpd/dns.c
@@ -0,0 +1,379 @@
+/* $OpenBSD: dns.c,v 1.89 2019/09/18 11:26:30 eric Exp $ */
+
+/*
+ * Copyright (c) 2008 Gilles Chehade <gilles@poolp.org>
+ * Copyright (c) 2009 Jacek Masiulaniec <jacekm@dobremiasto.net>
+ * 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"
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/tree.h>
+#include <sys/queue.h>
+#include <sys/uio.h>
+
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <arpa/nameser.h>
+#ifdef HAVE_ARPA_NAMESER_COMPAT_H
+#include <arpa/nameser_compat.h>
+#endif
+#include <netdb.h>
+
+#include <asr.h>
+#include <event.h>
+#include <netdb.h>
+#include <resolv.h>
+#include <imsg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <limits.h>
+
+#include "smtpd.h"
+#include "log.h"
+#include "unpack_dns.h"
+
+/* On OpenBSD, this function is not needed because we don't free addrinfo */
+#if defined(NOOP_ASR_FREEADDRINFO)
+#define asr_freeaddrinfo(x) do { } while(0);
+#endif
+
+struct dns_lookup {
+ struct dns_session *session;
+ char *host;
+ int preference;
+};
+
+struct dns_session {
+ struct mproc *p;
+ uint64_t reqid;
+ int type;
+ char name[HOST_NAME_MAX+1];
+ size_t mxfound;
+ int error;
+ int refcount;
+};
+
+static void dns_lookup_host(struct dns_session *, const char *, int);
+static void dns_dispatch_host(struct asr_result *, void *);
+static void dns_dispatch_mx(struct asr_result *, void *);
+static void dns_dispatch_mx_preference(struct asr_result *, void *);
+
+static int
+domainname_is_addr(const char *s, struct sockaddr *sa, socklen_t *sl)
+{
+ struct addrinfo hints, *res;
+ socklen_t sl2;
+ size_t l;
+ char buf[SMTPD_MAXDOMAINPARTSIZE];
+ int i6, error;
+
+ if (*s != '[')
+ return (0);
+
+ i6 = (strncasecmp("[IPv6:", s, 6) == 0);
+ s += i6 ? 6 : 1;
+
+ l = strlcpy(buf, s, sizeof(buf));
+ if (l >= sizeof(buf) || l == 0 || buf[l - 1] != ']')
+ return (0);
+
+ buf[l - 1] = '\0';
+ memset(&hints, 0, sizeof(hints));
+ hints.ai_flags = AI_NUMERICHOST;
+ hints.ai_socktype = SOCK_STREAM;
+ if (i6)
+ hints.ai_family = AF_INET6;
+
+ res = NULL;
+ if ((error = getaddrinfo(buf, NULL, &hints, &res))) {
+ log_warnx("getaddrinfo: %s", gai_strerror(error));
+ }
+
+ if (!res)
+ return (0);
+
+ if (sa && sl) {
+ sl2 = *sl;
+ if (sl2 > res->ai_addrlen)
+ sl2 = res->ai_addrlen;
+ memmove(sa, res->ai_addr, sl2);
+ *sl = res->ai_addrlen;
+ }
+
+ freeaddrinfo(res);
+ return (1);
+}
+
+void
+dns_imsg(struct mproc *p, struct imsg *imsg)
+{
+ struct sockaddr_storage ss;
+ struct dns_session *s;
+ struct sockaddr *sa;
+ struct asr_query *as;
+ struct msg m;
+ const char *domain, *mx, *host;
+ socklen_t sl;
+
+ s = xcalloc(1, sizeof *s);
+ s->type = imsg->hdr.type;
+ s->p = p;
+
+ m_msg(&m, imsg);
+ m_get_id(&m, &s->reqid);
+
+ switch (s->type) {
+
+ case IMSG_MTA_DNS_HOST:
+ m_get_string(&m, &host);
+ m_end(&m);
+ dns_lookup_host(s, host, -1);
+ return;
+
+ case IMSG_MTA_DNS_MX:
+ m_get_string(&m, &domain);
+ m_end(&m);
+ (void)strlcpy(s->name, domain, sizeof(s->name));
+
+ sa = (struct sockaddr *)&ss;
+ sl = sizeof(ss);
+
+ if (domainname_is_addr(domain, sa, &sl)) {
+ m_create(s->p, IMSG_MTA_DNS_HOST, 0, 0, -1);
+ m_add_id(s->p, s->reqid);
+ m_add_string(s->p, sockaddr_to_text(sa));
+ m_add_sockaddr(s->p, sa);
+ m_add_int(s->p, -1);
+ m_close(s->p);
+
+ m_create(s->p, IMSG_MTA_DNS_HOST_END, 0, 0, -1);
+ m_add_id(s->p, s->reqid);
+ m_add_int(s->p, DNS_OK);
+ m_close(s->p);
+ free(s);
+ return;
+ }
+
+ as = res_query_async(s->name, C_IN, T_MX, NULL);
+ if (as == NULL) {
+ log_warn("warn: res_query_async: %s", s->name);
+ m_create(s->p, IMSG_MTA_DNS_HOST_END, 0, 0, -1);
+ m_add_id(s->p, s->reqid);
+ m_add_int(s->p, DNS_EINVAL);
+ m_close(s->p);
+ free(s);
+ return;
+ }
+
+ event_asr_run(as, dns_dispatch_mx, s);
+ return;
+
+ case IMSG_MTA_DNS_MX_PREFERENCE:
+ m_get_string(&m, &domain);
+ m_get_string(&m, &mx);
+ m_end(&m);
+ (void)strlcpy(s->name, mx, sizeof(s->name));
+
+ as = res_query_async(domain, C_IN, T_MX, NULL);
+ if (as == NULL) {
+ m_create(s->p, IMSG_MTA_DNS_MX_PREFERENCE, 0, 0, -1);
+ m_add_id(s->p, s->reqid);
+ m_add_int(s->p, DNS_ENOTFOUND);
+ m_close(s->p);
+ free(s);
+ return;
+ }
+
+ event_asr_run(as, dns_dispatch_mx_preference, s);
+ return;
+
+ default:
+ log_warnx("warn: bad dns request %d", s->type);
+ fatal(NULL);
+ }
+}
+
+static void
+dns_dispatch_host(struct asr_result *ar, void *arg)
+{
+ struct dns_session *s;
+ struct dns_lookup *lookup = arg;
+ struct addrinfo *ai;
+
+ s = lookup->session;
+
+ for (ai = ar->ar_addrinfo; ai; ai = ai->ai_next) {
+ s->mxfound++;
+ m_create(s->p, IMSG_MTA_DNS_HOST, 0, 0, -1);
+ m_add_id(s->p, s->reqid);
+ m_add_string(s->p, lookup->host);
+ m_add_sockaddr(s->p, ai->ai_addr);
+ m_add_int(s->p, lookup->preference);
+ m_close(s->p);
+ }
+ free(lookup->host);
+ free(lookup);
+ if (ar->ar_addrinfo)
+ asr_freeaddrinfo(ar->ar_addrinfo);
+
+ if (ar->ar_gai_errno)
+ s->error = ar->ar_gai_errno;
+
+ if (--s->refcount)
+ return;
+
+ m_create(s->p, IMSG_MTA_DNS_HOST_END, 0, 0, -1);
+ m_add_id(s->p, s->reqid);
+ m_add_int(s->p, s->mxfound ? DNS_OK : DNS_ENOTFOUND);
+ m_close(s->p);
+ free(s);
+}
+
+static void
+dns_dispatch_mx(struct asr_result *ar, void *arg)
+{
+ struct dns_session *s = arg;
+ struct unpack pack;
+ struct dns_header h;
+ struct dns_query q;
+ struct dns_rr rr;
+ char buf[512];
+ size_t found;
+
+ if (ar->ar_h_errno && ar->ar_h_errno != NO_DATA &&
+ ar->ar_h_errno != NOTIMP) {
+
+ m_create(s->p, IMSG_MTA_DNS_HOST_END, 0, 0, -1);
+ m_add_id(s->p, s->reqid);
+ if (ar->ar_rcode == NXDOMAIN)
+ m_add_int(s->p, DNS_ENONAME);
+ else if (ar->ar_h_errno == NO_RECOVERY)
+ m_add_int(s->p, DNS_EINVAL);
+ else
+ m_add_int(s->p, DNS_RETRY);
+ m_close(s->p);
+ free(s);
+ free(ar->ar_data);
+ return;
+ }
+
+ unpack_init(&pack, ar->ar_data, ar->ar_datalen);
+ unpack_header(&pack, &h);
+ unpack_query(&pack, &q);
+
+ found = 0;
+ for (; h.ancount; h.ancount--) {
+ unpack_rr(&pack, &rr);
+ if (rr.rr_type != T_MX)
+ continue;
+ print_dname(rr.rr.mx.exchange, buf, sizeof(buf));
+ buf[strlen(buf) - 1] = '\0';
+ dns_lookup_host(s, buf, rr.rr.mx.preference);
+ found++;
+ }
+ free(ar->ar_data);
+
+ /* fallback to host if no MX is found. */
+ if (found == 0)
+ dns_lookup_host(s, s->name, 0);
+}
+
+static void
+dns_dispatch_mx_preference(struct asr_result *ar, void *arg)
+{
+ struct dns_session *s = arg;
+ struct unpack pack;
+ struct dns_header h;
+ struct dns_query q;
+ struct dns_rr rr;
+ char buf[512];
+ int error;
+
+ if (ar->ar_h_errno) {
+ if (ar->ar_rcode == NXDOMAIN)
+ error = DNS_ENONAME;
+ else if (ar->ar_h_errno == NO_RECOVERY
+ || ar->ar_h_errno == NO_DATA)
+ error = DNS_EINVAL;
+ else
+ error = DNS_RETRY;
+ }
+ else {
+ error = DNS_ENOTFOUND;
+ unpack_init(&pack, ar->ar_data, ar->ar_datalen);
+ unpack_header(&pack, &h);
+ unpack_query(&pack, &q);
+ for (; h.ancount; h.ancount--) {
+ unpack_rr(&pack, &rr);
+ if (rr.rr_type != T_MX)
+ continue;
+ print_dname(rr.rr.mx.exchange, buf, sizeof(buf));
+ buf[strlen(buf) - 1] = '\0';
+ if (!strcasecmp(s->name, buf)) {
+ error = DNS_OK;
+ break;
+ }
+ }
+ }
+
+ free(ar->ar_data);
+
+ m_create(s->p, IMSG_MTA_DNS_MX_PREFERENCE, 0, 0, -1);
+ m_add_id(s->p, s->reqid);
+ m_add_int(s->p, error);
+ if (error == DNS_OK)
+ m_add_int(s->p, rr.rr.mx.preference);
+ m_close(s->p);
+ free(s);
+}
+
+static void
+dns_lookup_host(struct dns_session *s, const char *host, int preference)
+{
+ struct dns_lookup *lookup;
+ struct addrinfo hints;
+ char hostcopy[HOST_NAME_MAX+1];
+ char *p;
+ void *as;
+
+ lookup = xcalloc(1, sizeof *lookup);
+ lookup->preference = preference;
+ lookup->host = xstrdup(host);
+ lookup->session = s;
+ s->refcount++;
+
+ if (*host == '[') {
+ if (strncasecmp("[IPv6:", host, 6) == 0)
+ host += 6;
+ else
+ host += 1;
+ (void)strlcpy(hostcopy, host, sizeof hostcopy);
+ p = strchr(hostcopy, ']');
+ if (p)
+ *p = 0;
+ host = hostcopy;
+ }
+
+ memset(&hints, 0, sizeof(hints));
+ hints.ai_flags = AI_ADDRCONFIG;
+ hints.ai_family = PF_UNSPEC;
+ hints.ai_socktype = SOCK_STREAM;
+ as = getaddrinfo_async(host, NULL, &hints, NULL);
+ event_asr_run(as, dns_dispatch_host, lookup);
+}
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.