5944def9ab
These programs parse ND6 Router Advertisement messages; rtsold(8) has required an SA, SA-14:20.rtsold, for a bug in this code. Thus, they are good candidates for sandboxing. The approach taken is to run the main executable in capability mode and use Casper services to provide functionality that cannot be implemented within the sandbox. In particular, several custom services were required. - A Casper service is used to send Router Solicitation messages on a raw ICMP6 socket. Initially I took the approach of creating a socket for each interface upon startup, and connect(2)ing it to the all-routers multicast group for the interface. This permits the use of sendmsg(2) in capability mode, but only works if the interface's link is up when rtsol(d) starts. So, instead, the rtsold.sendmsg service is used to transmit RS messages on behalf of the main process. One could alternately define a service which simply creates and connects a socket for each destination address, and returns the socket to the sandboxed process. However, to implement rtsold's -m option we also need to read the ND6 default router list, and this cannot be done in capability mode. - rtsold may execute resolvconf(8) in response to RDNSS and DNSSL options in received RA messages. A Casper service is used to fork and exec resolvconf(8), and to reap the child process. - A service is used to determine whether a given interface's link-local address is useable (i.e., not duplicated or undergoing DAD). This information is supplied by getifaddrs(3), which reads a sysctl not available in capability mode. The SIOCGIFCONF socket ioctl provides equivalent information and can be used in capability mode, but I decided against it for now because of some limitations of that interface. In addition to these new services, cap_syslog(3) is used to send messages to syslogd. Reviewed by: oshogbo Tested by: bz (previous versions) MFC after: 2 months Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D17572
158 lines
4.3 KiB
C
158 lines
4.3 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause
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*
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* Copyright (c) 2018 The FreeBSD Foundation
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*
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* This software was developed by Mark Johnston under sponsorship from
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* the FreeBSD Foundation.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/types.h>
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#include <sys/dnv.h>
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#include <sys/ioctl.h>
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#include <sys/nv.h>
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#include <sys/queue.h>
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#include <net/if.h>
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#include <netinet/in.h>
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#include <netinet6/in6_var.h>
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#include <errno.h>
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#include <ifaddrs.h>
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#include <string.h>
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#include <libcasper.h>
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#include <libcasper_service.h>
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#include "rtsold.h"
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/*
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* A service to fetch the flags for the link-local IPv6 address on the specified
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* interface. This cannot easily be done in capability mode because we need to
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* use the routing socket sysctl API to find the link-local address of a
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* particular interface. The SIOCGIFCONF ioctl is one other option, but as
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* currently implemented it is less flexible (it cannot report the required
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* buffer length), and hard-codes a buffer length limit.
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*/
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static int
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llflags_get(const char *ifname, int *flagsp)
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{
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struct in6_ifreq ifr6;
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struct ifaddrs *ifap, *ifa;
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struct sockaddr_in6 *sin6;
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int error, s;
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s = socket(PF_INET6, SOCK_DGRAM, 0);
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if (s < 0)
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return (-1);
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if (getifaddrs(&ifap) != 0)
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return (-1);
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error = -1;
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for (ifa = ifap; ifa != NULL; ifa = ifa->ifa_next) {
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if (strcmp(ifa->ifa_name, ifname) != 0)
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continue;
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if (ifa->ifa_addr->sa_family != AF_INET6)
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continue;
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sin6 = (struct sockaddr_in6 *)(void *)ifa->ifa_addr;
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if (!IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr))
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continue;
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memset(&ifr6, 0, sizeof(ifr6));
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if (strlcpy(ifr6.ifr_name, ifname, sizeof(ifr6.ifr_name)) >=
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sizeof(ifr6.ifr_name)) {
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freeifaddrs(ifap);
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errno = EINVAL;
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return (-1);
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}
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memcpy(&ifr6.ifr_ifru.ifru_addr, sin6, sin6->sin6_len);
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if (ioctl(s, SIOCGIFAFLAG_IN6, &ifr6) < 0) {
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error = errno;
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freeifaddrs(ifap);
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errno = error;
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return (-1);
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}
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*flagsp = ifr6.ifr_ifru.ifru_flags6;
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error = 0;
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break;
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}
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(void)close(s);
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freeifaddrs(ifap);
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if (error == -1)
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errno = ENOENT;
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return (error);
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}
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int
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cap_llflags_get(cap_channel_t *cap, const char *ifname, int *flagsp)
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{
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#ifdef WITH_CASPER
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nvlist_t *nvl;
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int error;
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nvl = nvlist_create(0);
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nvlist_add_string(nvl, "cmd", "get");
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nvlist_add_string(nvl, "ifname", ifname);
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nvl = cap_xfer_nvlist(cap, nvl);
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if (nvl == NULL)
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return (-1);
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error = (int)dnvlist_get_number(nvl, "error", 0);
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if (error == 0)
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*flagsp = (int)nvlist_get_number(nvl, "flags");
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nvlist_destroy(nvl);
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if (error != 0)
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errno = error;
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return (error == 0 ? 0 : -1);
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#else
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(void)cap;
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return (llflags_get(ifname, flagsp));
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#endif
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}
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#ifdef WITH_CASPER
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static int
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llflags_command(const char *cmd, const nvlist_t *limits __unused,
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nvlist_t *nvlin, nvlist_t *nvlout)
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{
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const char *ifname;
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int flags;
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if (strcmp(cmd, "get") != 0)
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return (EINVAL);
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ifname = nvlist_get_string(nvlin, "ifname");
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if (llflags_get(ifname, &flags) != 0)
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return (errno);
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nvlist_add_number(nvlout, "flags", flags);
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return (0);
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}
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CREATE_SERVICE("rtsold.llflags", NULL, llflags_command, 0);
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#endif /* WITH_CASPER */
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