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/*
* 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 <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#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;
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);
}
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);
}
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