usr.sbin/pflogd/privsep.c

   1 /*      $OpenBSD: privsep.c,v 1.16 2006/10/25 20:55:04 moritz Exp $     */
   2
   3 /*
   4  * Copyright (c) 2003 Can Erkin Acar
   5  * Copyright (c) 2003 Anil Madhavapeddy <anil@recoil.org>
   6  *
   7  * Permission to use, copy, modify, and distribute this software for any
   8  * purpose with or without fee is hereby granted, provided that the above
   9  * copyright notice and this permission notice appear in all copies.
  10  *
  11  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  12  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  13  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  14  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  15  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  16  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  17  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  18  */
  19 #include <sys/types.h>
  20 #include <sys/time.h>
  21 #include <sys/socket.h>
  22 #include <sys/ioctl.h>
  23
  24 #include <net/if.h>
  25 #include <net/bpf.h>
  26
  27 #include <err.h>
  28 #include <errno.h>
  29 #include <fcntl.h>
  30 #include <limits.h>
  31 #include <pwd.h>
  32 #include <signal.h>
  33 #include <stdio.h>
  34 #include <stdlib.h>
  35 #include <string.h>
  36 #include <pcap.h>
  37 #include <pcap-int.h>
  38 #include <syslog.h>
  39 #include <unistd.h>
  40 #include "pflogd.h"
  41
  42 enum cmd_types {
  43         PRIV_SET_SNAPLEN,       /* set the snaplength */
  44         PRIV_MOVE_LOG,          /* move logfile away */
  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 static int  move_log(const char *name);
  60
  61 extern char *filename;
  62 extern pcap_t *hpcap;
  63
  64 /* based on syslogd privsep */
  65 int
  66 priv_init(void)
  67 {
  68         int i, fd, socks[2], cmd;
  69         int snaplen, ret, olderrno;
  70         struct passwd *pw;
  71
  72         for (i = 1; i < NSIG; i++)
  73                 signal(i, SIG_DFL);
  74
  75         /* Create sockets */
  76         if (socketpair(AF_LOCAL, SOCK_STREAM, PF_UNSPEC, socks) == -1)
  77                 err(1, "socketpair() failed");
  78
  79         pw = getpwnam("_pflogd");
  80         if (pw == NULL)
  81                 errx(1, "unknown user _pflogd");
  82         endpwent();
  83
  84         child_pid = fork();
  85         if (child_pid < 0)
  86                 err(1, "fork() failed");
  87
  88         if (!child_pid) {
  89                 gid_t gidset[1];
  90
  91                 /* Child - drop privileges and return */
  92                 if (chroot(pw->pw_dir) != 0)
  93                         err(1, "unable to chroot");
  94                 if (chdir("/") != 0)
  95                         err(1, "unable to chdir");
  96
  97                 gidset[0] = pw->pw_gid;
  98                 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1)
  99                         err(1, "setresgid() failed");
 100                 if (setgroups(1, gidset) == -1)
 101                         err(1, "setgroups() failed");
 102                 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1)
 103                         err(1, "setresuid() failed");
 104                 close(socks[0]);
 105                 priv_fd = socks[1];
 106                 return 0;
 107         }
 108
 109         /* Father */
 110         /* Pass ALRM/TERM/HUP/INT/QUIT through to child, and accept CHLD */
 111         signal(SIGALRM, sig_pass_to_chld);
 112         signal(SIGTERM, sig_pass_to_chld);
 113         signal(SIGHUP,  sig_pass_to_chld);
 114         signal(SIGINT,  sig_pass_to_chld);
 115         signal(SIGQUIT,  sig_pass_to_chld);
 116         signal(SIGCHLD, sig_chld);
 117
 118         setproctitle("[priv]");
 119         close(socks[1]);
 120
 121         while (!gotsig_chld) {
 122                 if (may_read(socks[0], &cmd, sizeof(int)))
 123                         break;
 124                 switch (cmd) {
 125                 case PRIV_SET_SNAPLEN:
 126                         logmsg(LOG_DEBUG,
 127                             "[priv]: msg PRIV_SET_SNAPLENGTH received");
 128                         must_read(socks[0], &snaplen, sizeof(int));
 129
 130                         ret = set_snaplen(snaplen);
 131                         if (ret) {
 132                                 logmsg(LOG_NOTICE,
 133                                    "[priv]: set_snaplen failed for snaplen %d",
 134                                    snaplen);
 135                         }
 136
 137                         must_write(socks[0], &ret, sizeof(int));
 138                         break;
 139
 140                 case PRIV_OPEN_LOG:
 141                         logmsg(LOG_DEBUG,
 142                             "[priv]: msg PRIV_OPEN_LOG received");
 143                         /* create or append logs but do not follow symlinks */
 144                         fd = open(filename,
 145                             O_RDWR|O_CREAT|O_APPEND|O_NONBLOCK|O_NOFOLLOW,
 146                             0600);
 147                         olderrno = errno;
 148                         send_fd(socks[0], fd);
 149                         if (fd < 0)
 150                                 logmsg(LOG_NOTICE,
 151                                     "[priv]: failed to open %s: %s",
 152                                     filename, strerror(olderrno));
 153                         else
 154                                 close(fd);
 155                         break;
 156
 157                 case PRIV_MOVE_LOG:
 158                         logmsg(LOG_DEBUG,
 159                             "[priv]: msg PRIV_MOVE_LOG received");
 160                         ret = move_log(filename);
 161                         must_write(socks[0], &ret, sizeof(int));
 162                         break;
 163
 164                 default:
 165                         logmsg(LOG_ERR, "[priv]: unknown command %d", cmd);
 166                         _exit(1);
 167                         /* NOTREACHED */
 168                 }
 169         }
 170
 171         _exit(1);
 172 }
 173
 174 /* this is called from parent */
 175 static int
 176 set_snaplen(int snap)
 177 {
 178         if (hpcap == NULL)
 179                 return (1);
 180
 181         hpcap->snapshot = snap;
 182         set_pcap_filter();
 183
 184         return 0;
 185 }
 186
 187 static int
 188 move_log(const char *name)
 189 {
 190         char ren[PATH_MAX];
 191         u_int32_t len;
 192
 193         for (;;) {
 194                 int fd;
 195
 196                 len = snprintf(ren, sizeof(ren), "%s.bad.%08x",
 197                     name, arc4random());
 198                 if (len >= sizeof(ren)) {
 199                         logmsg(LOG_ERR, "[priv] new name too long");
 200                         return (1);
 201                 }
 202
 203                 /* lock destinanion */
 204                 fd = open(ren, O_CREAT|O_EXCL, 0);
 205                 if (fd >= 0) {
 206                         close(fd);
 207                         break;
 208                 }
 209                 /* if file exists, try another name */
 210                 if (errno != EEXIST && errno != EINTR) {
 211                         logmsg(LOG_ERR, "[priv] failed to create new name: %s",
 212                             strerror(errno));
 213                         return (1);
 214                 }
 215         }
 216
 217         if (rename(name, ren)) {
 218                 logmsg(LOG_ERR, "[priv] failed to rename %s to %s: %s",
 219                     name, ren, strerror(errno));
 220                 return (1);
 221         }
 222
 223         logmsg(LOG_NOTICE,
 224                "[priv]: log file %s moved to %s", name, ren);
 225
 226         return (0);
 227 }
 228
 229 /*
 230  * send the snaplength to privileged process
 231  */
 232 int
 233 priv_set_snaplen(int snaplen)
 234 {
 235         int cmd, ret;
 236
 237         if (priv_fd < 0)
 238                 errx(1, "%s: called from privileged portion", __func__);
 239
 240         cmd = PRIV_SET_SNAPLEN;
 241
 242         must_write(priv_fd, &cmd, sizeof(int));
 243         must_write(priv_fd, &snaplen, sizeof(int));
 244
 245         must_read(priv_fd, &ret, sizeof(int));
 246
 247         /* also set hpcap->snapshot in child */
 248         if (ret == 0)
 249                 hpcap->snapshot = snaplen;
 250
 251         return (ret);
 252 }
 253
 254 /* Open log-file */
 255 int
 256 priv_open_log(void)
 257 {
 258         int cmd, fd;
 259
 260         if (priv_fd < 0)
 261                 errx(1, "%s: called from privileged portion", __func__);
 262
 263         cmd = PRIV_OPEN_LOG;
 264         must_write(priv_fd, &cmd, sizeof(int));
 265         fd = receive_fd(priv_fd);
 266
 267         return (fd);
 268 }
 269 /* Move-away and reopen log-file */
 270 int
 271 priv_move_log(void)
 272 {
 273         int cmd, ret;
 274
 275         if (priv_fd < 0)
 276                 errx(1, "%s: called from privileged portion\n", __func__);
 277
 278         cmd = PRIV_MOVE_LOG;
 279         must_write(priv_fd, &cmd, sizeof(int));
 280         must_read(priv_fd, &ret, sizeof(int));
 281
 282         return (ret);
 283 }
 284
 285 /* If priv parent gets a TERM or HUP, pass it through to child instead */
 286 static void
 287 sig_pass_to_chld(int sig)
 288 {
 289         int oerrno = errno;
 290
 291         if (child_pid != -1)
 292                 kill(child_pid, sig);
 293         errno = oerrno;
 294 }
 295
 296 /* if parent gets a SIGCHLD, it will exit */
 297 static void
 298 sig_chld(int sig __unused)
 299 {
 300         gotsig_chld = 1;
 301 }
 302
 303 /* Read all data or return 1 for error.  */
 304 static int
 305 may_read(int fd, void *buf, size_t n)
 306 {
 307         char *s = buf;
 308         ssize_t res;
 309         size_t pos = 0;
 310
 311         while (n > pos) {
 312                 res = read(fd, s + pos, n - pos);
 313                 switch (res) {
 314                 case -1:
 315                         if (errno == EINTR || errno == EAGAIN)
 316                                 continue;
 317                 case 0:
 318                         return (1);
 319                 default:
 320                         pos += res;
 321                 }
 322         }
 323         return (0);
 324 }
 325
 326 /* Read data with the assertion that it all must come through, or
 327  * else abort the process.  Based on atomicio() from openssh. */
 328 static void
 329 must_read(int fd, void *buf, size_t n)
 330 {
 331         char *s = buf;
 332         ssize_t res;
 333         size_t pos = 0;
 334
 335         while (n > pos) {
 336                 res = read(fd, s + pos, n - pos);
 337                 switch (res) {
 338                 case -1:
 339                         if (errno == EINTR || errno == EAGAIN)
 340                                 continue;
 341                 case 0:
 342                         _exit(0);
 343                 default:
 344                         pos += res;
 345                 }
 346         }
 347 }
 348
 349 /* Write data with the assertion that it all has to be written, or
 350  * else abort the process.  Based on atomicio() from openssh. */
 351 static void
 352 must_write(int fd, void *buf, size_t n)
 353 {
 354         char *s = buf;
 355         ssize_t res;
 356         size_t pos = 0;
 357
 358         while (n > pos) {
 359                 res = write(fd, s + pos, n - pos);
 360                 switch (res) {
 361                 case -1:
 362                         if (errno == EINTR || errno == EAGAIN)
 363                                 continue;
 364                 case 0:
 365                         _exit(0);
 366                 default:
 367                         pos += res;
 368                 }
 369         }
 370 }