server/usergroup.c

   1 /* nbdkit
   2  * Copyright (C) 2019 Red Hat Inc.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *
  11  * * Redistributions in binary form must reproduce the above copyright
  12  * notice, this list of conditions and the following disclaimer in the
  13  * documentation and/or other materials provided with the distribution.
  14  *
  15  * * Neither the name of Red Hat nor the names of its contributors may be
  16  * used to endorse or promote products derived from this software without
  17  * specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  22  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  26  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  27  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <config.h>
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <stdarg.h>
  38 #include <string.h>
  39 #include <unistd.h>
  40 #include <pwd.h>
  41 #include <grp.h>
  42 #include <errno.h>
  43 #include <sys/types.h>
  44
  45 #include "internal.h"
  46
  47 static uid_t parseuser (const char *);
  48 static gid_t parsegroup (const char *);
  49
  50 /* Handle the -u and -g options.  If user and group are non-NULL
  51  * then this parses them to work out the UID/GID and changes
  52  * user and group.
  53  */
  54 void
  55 change_user (void)
  56 {
  57   if (group) {
  58     gid_t gid = parsegroup (group);
  59
  60     if (setgid (gid) == -1) {
  61       perror ("setgid");
  62       exit (EXIT_FAILURE);
  63     }
  64
  65     /* Kill supplemental groups from parent process. */
  66     if (setgroups (1, &gid) == -1) {
  67       perror ("setgroups");
  68       exit (EXIT_FAILURE);
  69     }
  70
  71     debug ("changed group to %s", group);
  72   }
  73
  74   if (user) {
  75     uid_t uid = parseuser (user);
  76
  77     if (setuid (uid) == -1) {
  78       perror ("setuid");
  79       exit (EXIT_FAILURE);
  80     }
  81
  82     debug ("changed user to %s", user);
  83   }
  84 }
  85
  86 static uid_t
  87 parseuser (const char *id)
  88 {
  89   struct passwd *pwd;
  90   int saved_errno;
  91
  92   errno = 0;
  93   pwd = getpwnam (id);
  94
  95   if (NULL == pwd) {
  96     int val;
  97
  98     saved_errno = errno;
  99
 100     if (nbdkit_parse_int ("parseuser", id, &val) == 0)
 101       return val;
 102
 103     fprintf (stderr, "%s: -u option: %s is not a valid user name or uid",
 104              program_name, id);
 105     if (saved_errno != 0)
 106       fprintf (stderr, " (getpwnam error: %s)", strerror (saved_errno));
 107     fprintf (stderr, "\n");
 108     exit (EXIT_FAILURE);
 109   }
 110
 111   return pwd->pw_uid;
 112 }
 113
 114 static gid_t
 115 parsegroup (const char *id)
 116 {
 117   struct group *grp;
 118   int saved_errno;
 119
 120   errno = 0;
 121   grp = getgrnam (id);
 122
 123   if (NULL == grp) {
 124     int val;
 125
 126     saved_errno = errno;
 127
 128     if (nbdkit_parse_int ("parsegroup", id, &val) == 0)
 129       return val;
 130
 131     fprintf (stderr, "%s: -g option: %s is not a valid group name or gid",
 132              program_name, id);
 133     if (saved_errno != 0)
 134       fprintf (stderr, " (getgrnam error: %s)", strerror (saved_errno));
 135     fprintf (stderr, "\n");
 136     exit (EXIT_FAILURE);
 137   }
 138
 139   return grp->gr_gid;
 140 }