sbin/mount_portal/pt_file.c

   1 /*      $NetBSD: pt_file.c,v 1.16 2005/02/09 13:57:57 xtraeme Exp $     */
   2
   3 /*
   4  * Copyright (c) 1992, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software donated to Berkeley by
   8  * Jan-Simon Pendry.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  *
  34  *      from: Id: pt_file.c,v 1.1 1992/05/25 21:43:09 jsp Exp
  35  *      @(#)pt_file.c   8.3 (Berkeley) 7/3/94
  36  */
  37
  38 #include <sys/cdefs.h>
  39 #ifndef lint
  40 __RCSID("$NetBSD: pt_file.c,v 1.16 2005/02/09 13:57:57 xtraeme Exp $");
  41 #endif /* not lint */
  42
  43 #include <stdio.h>
  44 #include <unistd.h>
  45 #include <stdlib.h>
  46 #include <string.h>
  47 #include <errno.h>
  48 #include <fcntl.h>
  49 #include <sys/types.h>
  50 #include <sys/param.h>
  51 #include <sys/syslog.h>
  52
  53 #include "portald.h"
  54
  55 #ifdef DEBUG
  56 #define DEBUG_SYSLOG    syslog
  57 #else
  58 /*
  59  * The "if (0) ..." will be optimized away by the compiler if
  60  * DEBUG is not defined.
  61  */
  62 #define DEBUG_SYSLOG    if (0) syslog
  63 #endif
  64
  65 int
  66 lose_credentials(struct portal_cred *pcr)
  67 {
  68         /*
  69          * If we are root, then switch into the caller's credentials.
  70          * By the way, we _always_ log failures, to make
  71          * sure questionable activity is noticed.
  72          */
  73         if (getuid() == 0) {
  74                 /* Set groups first ... */
  75                 if (setgroups(pcr->pcr_ngroups, pcr->pcr_groups) < 0) {
  76                         syslog(LOG_WARNING,
  77                             "lose_credentials: setgroups() failed (%m)");
  78                         return (errno);
  79                 }
  80                 /* ... then gid ... */
  81                 if (setgid(pcr->pcr_gid) < 0) {
  82                         syslog(LOG_WARNING,
  83                                 "lose_credentials: setgid(%d) failed (%m)",
  84                                 pcr->pcr_gid);
  85                 }
  86                 /*
  87                  * ... and now do the setuid() where we lose all special
  88                  * powers (both real and effective userid).
  89                  */
  90                 if (setuid(pcr->pcr_uid) < 0) {
  91                         syslog(LOG_WARNING,
  92                                 "lose_credentials: setuid(%d) failed (%m)",
  93                                 pcr->pcr_uid);
  94                 }
  95                 /* The credential change was successful! */
  96                 DEBUG_SYSLOG(LOG_DEBUG, "Root-owned mount process lowered credentials -- returning successfully!\n");
  97                 return 0;
  98         }
  99         DEBUG_SYSLOG(LOG_DEBUG, "Actual/effective/caller's creds are:");
 100         DEBUG_SYSLOG(LOG_DEBUG, "%d/%d %d/%d %d/%d", getuid(),
 101             getgid(), geteuid(), getegid(), pcr->pcr_uid, pcr->pcr_gid);
 102         /*
 103          * Else, fail if the uid is neither actual or effective
 104          * uid of mount process...
 105          */
 106         if ((getuid() != pcr->pcr_uid) && (geteuid() != pcr->pcr_uid)) {
 107                 syslog(LOG_WARNING,
 108                     "lose_credentials: uid %d != uid %d, or euid %d != uid %d",
 109                     getuid(), pcr->pcr_uid, geteuid(), pcr->pcr_uid);
 110                 return EPERM;
 111         }
 112         /*
 113          * ... or the gid is neither the actual or effective
 114          * gid of the mount process.
 115          */
 116         if ((getgid() != pcr->pcr_gid) && (getegid() != pcr->pcr_gid)) {
 117                 syslog(LOG_WARNING,
 118                     "lose_credentials: gid %d != gid %d, or egid %d != gid %d",
 119                     getgid(), pcr->pcr_gid, getegid(), pcr->pcr_gid);
 120                 return EPERM;
 121         }
 122         /*
 123          * If we make it here, we have a uid _and_ gid match! Allow the
 124          * access.
 125          */
 126         DEBUG_SYSLOG(LOG_DEBUG, "Returning successfully!\n");
 127         return 0;
 128 }
 129
 130 int
 131 portal_file(struct portal_cred *pcr, char *key, char **v, int *fdp)
 132 {
 133         int     fd;
 134         char    pbuf[MAXPATHLEN];
 135         int     error;
 136         int     origuid, origgid;
 137
 138         origuid = getuid();
 139         origgid = getgid();
 140         pbuf[0] = '/';
 141         strlcpy(pbuf + 1, key + (v[1] ? strlen(v[1]) : 0), sizeof(pbuf) - 1);
 142         DEBUG_SYSLOG(LOG_DEBUG, "path = %s, uid = %d, gid = %d",
 143             pbuf, pcr->pcr_uid, pcr->pcr_gid);
 144
 145         if ((error = lose_credentials(pcr)) != 0) {
 146                 DEBUG_SYSLOG(LOG_DEBUG, "portal_file: Credential err %d", error);
 147                 return error;
 148         }
 149         error = 0;
 150         /*
 151          * Be careful -- only set error to errno if there is an error.
 152          * errno could hold an old, uncaught value, from a routine
 153          * called long before now.
 154          */
 155         fd = open(pbuf, O_RDWR | O_CREAT, 0666);
 156         if (fd < 0) {
 157                 error = errno;
 158                 if (error == EACCES) {
 159                         DEBUG_SYSLOG(LOG_DEBUG, "Error:  could not open '%s' "
 160                             "read/write with create flag.  "
 161                             "Trying read-only open...", pbuf);
 162                         /* Try opening read-only. */
 163                         fd = open(pbuf, O_RDONLY, 0);
 164                         if (fd < 0) {
 165                                 error = errno;
 166                                 DEBUG_SYSLOG(LOG_DEBUG, "That failed too!  %m");
 167                         } else {
 168                                 /* Clear the error indicator. */
 169                                 error = 0;
 170                         }
 171                 } else {
 172                         DEBUG_SYSLOG(LOG_DEBUG, "Error:  could not open '%s': %m", pbuf);
 173                 }
 174
 175         }
 176         if (seteuid((uid_t) origuid) < 0) {     /* XXX - should reset gidset
 177                                                  * too */
 178                 error = errno;
 179                 syslog(LOG_WARNING, "setcred: %m");
 180                 if (fd >= 0) {
 181                         (void) close(fd);
 182                         fd = -1;
 183                 }
 184         }
 185         if (error == 0)
 186                 *fdp = fd;
 187
 188         DEBUG_SYSLOG(LOG_DEBUG, "pt_file returns *fdp = %d, error = %d", *fdp,
 189             error);
 190         return (error);
 191 }