usr.sbin/pflogd/privsep.c

   1 /*      $OpenBSD: privsep.c,v 1.8 2004/03/14 19:17:05 otto Exp $        */
   2 /*      $DragonFly: src/usr.sbin/pflogd/privsep.c,v 1.1 2004/09/21 21:25:28 joerg Exp $ */
   3
   4 /*
   5  * Copyright (c) 2003 Can Erkin Acar
   6  * Copyright (c) 2003 Anil Madhavapeddy <anil@recoil.org>
   7  *
   8  * Permission to use, copy, modify, and distribute this software for any
   9  * purpose with or without fee is hereby granted, provided that the above
  10  * copyright notice and this permission notice appear in all copies.
  11  *
  12  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  13  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  14  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  15  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  16  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  17  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  18  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  19  */
  20 #include <sys/ioctl.h>
  21 #include <sys/types.h>
  22 #include <sys/time.h>
  23 #include <sys/socket.h>
  24 #include <sys/ioctl.h>
  25
  26 #include <net/if.h>
  27 #include <net/bpf.h>
  28
  29 #include <err.h>
  30 #include <errno.h>
  31 #include <fcntl.h>
  32 #include <pwd.h>
  33 #include <signal.h>
  34 #include <stdio.h>
  35 #include <stdlib.h>
  36 #include <string.h>
  37 #include <pcap.h>
  38 #include <pcap-int.h>
  39 #include <syslog.h>
  40 #include <unistd.h>
  41 #include "pflogd.h"
  42
  43 enum cmd_types {
  44         PRIV_SET_SNAPLEN,       /* set the snaplength */
  45         PRIV_OPEN_LOG           /* open logfile for appending */
  46 };
  47
  48 static int priv_fd = -1;
  49 static volatile pid_t child_pid = -1;
  50
  51 volatile sig_atomic_t gotsig_chld = 0;
  52
  53 static void sig_pass_to_chld(int);
  54 static void sig_chld(int);
  55 static int  may_read(int, void *, size_t);
  56 static void must_read(int, void *, size_t);
  57 static void must_write(int, void *, size_t);
  58 static int  set_snaplen(int snap);
  59
  60 /* bpf filter expression common to parent and child */
  61 extern char *filter;
  62 extern char *errbuf;
  63 extern char *filename;
  64 extern pcap_t *hpcap;
  65
  66 /* based on syslogd privsep */
  67 int
  68 priv_init(void)
  69 {
  70         int i, fd, socks[2], cmd;
  71         int snaplen, ret;
  72         struct passwd *pw;
  73
  74         for (i = 1; i < NSIG; i++)
  75                 signal(i, SIG_DFL);
  76
  77         /* Create sockets */
  78         if (socketpair(AF_LOCAL, SOCK_STREAM, PF_UNSPEC, socks) == -1)
  79                 err(1, "socketpair() failed");
  80
  81         pw = getpwnam("_pflogd");
  82         if (pw == NULL)
  83                 errx(1, "unknown user _pflogd");
  84         endpwent();
  85
  86         child_pid = fork();
  87         if (child_pid < 0)
  88                 err(1, "fork() failed");
  89
  90         if (!child_pid) {
  91                 gid_t gidset[1];
  92
  93                 /* Child - drop privileges and return */
  94                 if (chroot(pw->pw_dir) != 0)
  95                         err(1, "unable to chroot");
  96                 if (chdir("/") != 0)
  97                         err(1, "unable to chdir");
  98
  99                 gidset[0] = pw->pw_gid;
 100                 if (setgroups(1, gidset) == -1)
 101                         err(1, "setgroups() failed");
 102                 if (setegid(pw->pw_gid) == -1)
 103                         err(1, "setegid() failed");
 104                 if (setgid(pw->pw_gid) == -1)
 105                         err(1, "setgid() failed");
 106                 if (seteuid(pw->pw_uid) == -1)
 107                         err(1, "seteuid() failed");
 108                 if (setuid(pw->pw_uid) == -1)
 109                         err(1, "setuid() failed");
 110                 close(socks[0]);
 111                 priv_fd = socks[1];
 112                 return 0;
 113         }
 114
 115         /* Father */
 116         /* Pass ALRM/TERM/HUP through to child, and accept CHLD */
 117         signal(SIGALRM, sig_pass_to_chld);
 118         signal(SIGTERM, sig_pass_to_chld);
 119         signal(SIGHUP,  sig_pass_to_chld);
 120         signal(SIGCHLD, sig_chld);
 121
 122         setproctitle("[priv]");
 123         close(socks[1]);
 124
 125         while (!gotsig_chld) {
 126                 if (may_read(socks[0], &cmd, sizeof(int)))
 127                         break;
 128                 switch (cmd) {
 129                 case PRIV_SET_SNAPLEN:
 130                         logmsg(LOG_DEBUG,
 131                             "[priv]: msg PRIV_SET_SNAPLENGTH received");
 132                         must_read(socks[0], &snaplen, sizeof(int));
 133
 134                         ret = set_snaplen(snaplen);
 135                         if (ret) {
 136                                 logmsg(LOG_NOTICE,
 137                                    "[priv]: set_snaplen failed for snaplen %d",
 138                                    snaplen);
 139                         }
 140
 141                         must_write(socks[0], &ret, sizeof(int));
 142                         break;
 143
 144                 case PRIV_OPEN_LOG:
 145                         logmsg(LOG_DEBUG,
 146                             "[priv]: msg PRIV_OPEN_LOG received");
 147                         /* create or append logs but do not follow symlinks */
 148                         fd = open(filename,
 149                             O_RDWR|O_CREAT|O_APPEND|O_NONBLOCK|O_NOFOLLOW,
 150                             0600);
 151                         if (fd < 0)
 152                                 logmsg(LOG_NOTICE,
 153                                     "[priv]: failed to open %s: %s",
 154                                     filename, strerror(errno));
 155                         send_fd(socks[0], fd);
 156                         close(fd);
 157                         break;
 158
 159                 default:
 160                         logmsg(LOG_ERR, "[priv]: unknown command %d", cmd);
 161                         _exit(1);
 162                         /* NOTREACHED */
 163                 }
 164         }
 165
 166         _exit(1);
 167 }
 168
 169 /* this is called from parent */
 170 static int
 171 set_snaplen(int snap)
 172 {
 173         if (hpcap == NULL)
 174                 return (1);
 175
 176         hpcap->snapshot = snap;
 177         set_pcap_filter();
 178
 179         return 0;
 180 }
 181
 182
 183 /*
 184  * send the snaplength to privileged process
 185  */
 186 int
 187 priv_set_snaplen(int snaplen)
 188 {
 189         int cmd, ret;
 190
 191         if (priv_fd < 0)
 192                 errx(1, "%s: called from privileged portion", __func__);
 193
 194         cmd = PRIV_SET_SNAPLEN;
 195
 196         must_write(priv_fd, &cmd, sizeof(int));
 197         must_write(priv_fd, &snaplen, sizeof(int));
 198
 199         must_read(priv_fd, &ret, sizeof(int));
 200
 201         /* also set hpcap->snapshot in child */
 202         if (ret == 0)
 203                 hpcap->snapshot = snaplen;
 204
 205         return (ret);
 206 }
 207
 208 /* Open log-file */
 209 int
 210 priv_open_log(void)
 211 {
 212         int cmd, fd;
 213
 214         if (priv_fd < 0)
 215                 errx(1, "%s: called from privileged portion\n", __func__);
 216
 217         cmd = PRIV_OPEN_LOG;
 218         must_write(priv_fd, &cmd, sizeof(int));
 219         fd = receive_fd(priv_fd);
 220
 221         return (fd);
 222 }
 223
 224 /* If priv parent gets a TERM or HUP, pass it through to child instead */
 225 static void
 226 sig_pass_to_chld(int sig)
 227 {
 228         int oerrno = errno;
 229
 230         if (child_pid != -1)
 231                 kill(child_pid, sig);
 232         errno = oerrno;
 233 }
 234
 235 /* if parent gets a SIGCHLD, it will exit */
 236 static void
 237 sig_chld(int sig __unused)
 238 {
 239         gotsig_chld = 1;
 240 }
 241
 242 /* Read all data or return 1 for error.  */
 243 static int
 244 may_read(int fd, void *buf, size_t n)
 245 {
 246         char *s = buf;
 247         ssize_t res;
 248         size_t pos = 0;
 249
 250         while (n > pos) {
 251                 res = read(fd, s + pos, n - pos);
 252                 switch (res) {
 253                 case -1:
 254                         if (errno == EINTR || errno == EAGAIN)
 255                                 continue;
 256                 case 0:
 257                         return (1);
 258                 default:
 259                         pos += res;
 260                 }
 261         }
 262         return (0);
 263 }
 264
 265 /* Read data with the assertion that it all must come through, or
 266  * else abort the process.  Based on atomicio() from openssh. */
 267 static void
 268 must_read(int fd, void *buf, size_t n)
 269 {
 270         char *s = buf;
 271         ssize_t res;
 272         size_t pos = 0;
 273
 274         while (n > pos) {
 275                 res = read(fd, s + pos, n - pos);
 276                 switch (res) {
 277                 case -1:
 278                         if (errno == EINTR || errno == EAGAIN)
 279                                 continue;
 280                 case 0:
 281                         _exit(0);
 282                 default:
 283                         pos += res;
 284                 }
 285         }
 286 }
 287
 288 /* Write data with the assertion that it all has to be written, or
 289  * else abort the process.  Based on atomicio() from openssh. */
 290 static void
 291 must_write(int fd, void *buf, size_t n)
 292 {
 293         char *s = buf;
 294         ssize_t res;
 295         size_t pos = 0;
 296
 297         while (n > pos) {
 298                 res = write(fd, s + pos, n - pos);
 299                 switch (res) {
 300                 case -1:
 301                         if (errno == EINTR || errno == EAGAIN)
 302                                 continue;
 303                 case 0:
 304                         _exit(0);
 305                 default:
 306                         pos += res;
 307                 }
 308         }
 309 }