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-rw-r--r--lib/dns/ssu_external.c260
1 files changed, 260 insertions, 0 deletions
diff --git a/lib/dns/ssu_external.c b/lib/dns/ssu_external.c
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+++ b/lib/dns/ssu_external.c
@@ -0,0 +1,260 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+/*
+ * This implements external update-policy rules. This allows permission
+ * to update a zone to be checked by consulting an external daemon (e.g.,
+ * kerberos).
+ */
+
+#include <errno.h>
+#include <inttypes.h>
+#include <stdbool.h>
+#include <unistd.h>
+
+#ifdef ISC_PLATFORM_HAVESYSUNH
+#include <sys/socket.h>
+#include <sys/un.h>
+#endif /* ifdef ISC_PLATFORM_HAVESYSUNH */
+
+#include <isc/magic.h>
+#include <isc/mem.h>
+#include <isc/netaddr.h>
+#include <isc/print.h>
+#include <isc/result.h>
+#include <isc/strerr.h>
+#include <isc/string.h>
+#include <isc/util.h>
+
+#include <dns/fixedname.h>
+#include <dns/log.h>
+#include <dns/name.h>
+#include <dns/rdatatype.h>
+#include <dns/ssu.h>
+
+#include <dst/dst.h>
+
+static void
+ssu_e_log(int level, const char *fmt, ...) {
+ va_list ap;
+
+ va_start(ap, fmt);
+ isc_log_vwrite(dns_lctx, DNS_LOGCATEGORY_SECURITY, DNS_LOGMODULE_ZONE,
+ ISC_LOG_DEBUG(level), fmt, ap);
+ va_end(ap);
+}
+
+/*
+ * Connect to a UNIX domain socket.
+ */
+static int
+ux_socket_connect(const char *path) {
+ int fd = -1;
+#ifdef ISC_PLATFORM_HAVESYSUNH
+ struct sockaddr_un addr;
+
+ REQUIRE(path != NULL);
+
+ if (strlen(path) > sizeof(addr.sun_path)) {
+ ssu_e_log(3,
+ "ssu_external: socket path '%s' "
+ "longer than system maximum %zu",
+ path, sizeof(addr.sun_path));
+ return (-1);
+ }
+
+ memset(&addr, 0, sizeof(addr));
+ addr.sun_family = AF_UNIX;
+ strlcpy(addr.sun_path, path, sizeof(addr.sun_path));
+
+ fd = socket(AF_UNIX, SOCK_STREAM, 0);
+ if (fd == -1) {
+ char strbuf[ISC_STRERRORSIZE];
+ strerror_r(errno, strbuf, sizeof(strbuf));
+ ssu_e_log(3, "ssu_external: unable to create socket - %s",
+ strbuf);
+ return (-1);
+ }
+
+ if (connect(fd, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
+ char strbuf[ISC_STRERRORSIZE];
+ strerror_r(errno, strbuf, sizeof(strbuf));
+ ssu_e_log(3,
+ "ssu_external: unable to connect to "
+ "socket '%s' - %s",
+ path, strbuf);
+ close(fd);
+ return (-1);
+ }
+#endif /* ifdef ISC_PLATFORM_HAVESYSUNH */
+ return (fd);
+}
+
+/* Change this version if you update the format of the request */
+#define SSU_EXTERNAL_VERSION 1
+
+/*
+ * Perform an update-policy rule check against an external application
+ * over a socket.
+ *
+ * This currently only supports local: for unix domain datagram sockets.
+ *
+ * Note that by using a datagram socket and creating a new socket each
+ * time we avoid the need for locking and allow for parallel access to
+ * the authorization server.
+ */
+bool
+dns_ssu_external_match(const dns_name_t *identity, const dns_name_t *signer,
+ const dns_name_t *name, const isc_netaddr_t *tcpaddr,
+ dns_rdatatype_t type, const dst_key_t *key,
+ isc_mem_t *mctx) {
+ char b_identity[DNS_NAME_FORMATSIZE];
+ char b_signer[DNS_NAME_FORMATSIZE];
+ char b_name[DNS_NAME_FORMATSIZE];
+ char b_addr[ISC_NETADDR_FORMATSIZE];
+ char b_type[DNS_RDATATYPE_FORMATSIZE];
+ char b_key[DST_KEY_FORMATSIZE];
+ isc_buffer_t *tkey_token = NULL;
+ int fd;
+ const char *sock_path;
+ unsigned int req_len;
+ isc_region_t token_region = { NULL, 0 };
+ unsigned char *data;
+ isc_buffer_t buf;
+ uint32_t token_len = 0;
+ uint32_t reply;
+ ssize_t ret;
+
+ /* The identity contains local:/path/to/socket */
+ dns_name_format(identity, b_identity, sizeof(b_identity));
+
+ /* For now only local: is supported */
+ if (strncmp(b_identity, "local:", 6) != 0) {
+ ssu_e_log(3, "ssu_external: invalid socket path '%s'",
+ b_identity);
+ return (false);
+ }
+ sock_path = &b_identity[6];
+
+ fd = ux_socket_connect(sock_path);
+ if (fd == -1) {
+ return (false);
+ }
+
+ if (key != NULL) {
+ dst_key_format(key, b_key, sizeof(b_key));
+ tkey_token = dst_key_tkeytoken(key);
+ } else {
+ b_key[0] = 0;
+ }
+
+ if (tkey_token != NULL) {
+ isc_buffer_region(tkey_token, &token_region);
+ token_len = token_region.length;
+ }
+
+ /* Format the request elements */
+ if (signer != NULL) {
+ dns_name_format(signer, b_signer, sizeof(b_signer));
+ } else {
+ b_signer[0] = 0;
+ }
+
+ dns_name_format(name, b_name, sizeof(b_name));
+
+ if (tcpaddr != NULL) {
+ isc_netaddr_format(tcpaddr, b_addr, sizeof(b_addr));
+ } else {
+ b_addr[0] = 0;
+ }
+
+ dns_rdatatype_format(type, b_type, sizeof(b_type));
+
+ /* Work out how big the request will be */
+ req_len = sizeof(uint32_t) + /* Format version */
+ sizeof(uint32_t) + /* Length */
+ strlen(b_signer) + 1 + /* Signer */
+ strlen(b_name) + 1 + /* Name */
+ strlen(b_addr) + 1 + /* Address */
+ strlen(b_type) + 1 + /* Type */
+ strlen(b_key) + 1 + /* Key */
+ sizeof(uint32_t) + /* tkey_token length */
+ token_len; /* tkey_token */
+
+ /* format the buffer */
+ data = isc_mem_allocate(mctx, req_len);
+
+ isc_buffer_init(&buf, data, req_len);
+ isc_buffer_putuint32(&buf, SSU_EXTERNAL_VERSION);
+ isc_buffer_putuint32(&buf, req_len);
+
+ /* Strings must be null-terminated */
+ isc_buffer_putstr(&buf, b_signer);
+ isc_buffer_putuint8(&buf, 0);
+ isc_buffer_putstr(&buf, b_name);
+ isc_buffer_putuint8(&buf, 0);
+ isc_buffer_putstr(&buf, b_addr);
+ isc_buffer_putuint8(&buf, 0);
+ isc_buffer_putstr(&buf, b_type);
+ isc_buffer_putuint8(&buf, 0);
+ isc_buffer_putstr(&buf, b_key);
+ isc_buffer_putuint8(&buf, 0);
+
+ isc_buffer_putuint32(&buf, token_len);
+ if (tkey_token && token_len != 0) {
+ isc_buffer_putmem(&buf, token_region.base, token_len);
+ }
+
+ ENSURE(isc_buffer_availablelength(&buf) == 0);
+
+ /* Send the request */
+ ret = write(fd, data, req_len);
+ isc_mem_free(mctx, data);
+ if (ret != (ssize_t)req_len) {
+ char strbuf[ISC_STRERRORSIZE];
+ strerror_r(errno, strbuf, sizeof(strbuf));
+ ssu_e_log(3, "ssu_external: unable to send request - %s",
+ strbuf);
+ close(fd);
+ return (false);
+ }
+
+ /* Receive the reply */
+ ret = read(fd, &reply, sizeof(uint32_t));
+ if (ret != (ssize_t)sizeof(uint32_t)) {
+ char strbuf[ISC_STRERRORSIZE];
+ strerror_r(errno, strbuf, sizeof(strbuf));
+ ssu_e_log(3, "ssu_external: unable to receive reply - %s",
+ strbuf);
+ close(fd);
+ return (false);
+ }
+
+ close(fd);
+
+ reply = ntohl(reply);
+
+ if (reply == 0) {
+ ssu_e_log(3, "ssu_external: denied external auth for '%s'",
+ b_name);
+ return (false);
+ } else if (reply == 1) {
+ ssu_e_log(3, "ssu_external: allowed external auth for '%s'",
+ b_name);
+ return (true);
+ }
+
+ ssu_e_log(3, "ssu_external: invalid reply 0x%08x", reply);
+
+ return (false);
+}