lttng-sessiond/utils.c

   1 /*
   2  * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
   3  *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License as published by the Free
   7  * Software Foundation; only version 2 of the License.
   8  *
   9  * This program is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  12  * more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along with
  15  * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
  16  * Place - Suite 330, Boston, MA  02111-1307, USA.
  17  */
  18
  19 #define _GNU_SOURCE
  20 #include <errno.h>
  21 #include <limits.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <sys/wait.h>
  26 #include <sys/types.h>
  27 #include <sys/stat.h>
  28 #include <unistd.h>
  29
  30 #include <lttngerr.h>
  31
  32 #include "utils.h"
  33
  34 /*
  35  * Write to writable pipe used to notify a thread.
  36  */
  37 int notify_thread_pipe(int wpipe)
  38 {
  39         int ret;
  40
  41         ret = write(wpipe, "!", 1);
  42         if (ret < 0) {
  43                 PERROR("write poll pipe");
  44         }
  45
  46         return ret;
  47 }
  48
  49 /*
  50  * Return pointer to home directory path using the env variable HOME.
  51  *
  52  * No home, NULL is returned.
  53  */
  54 const char *get_home_dir(void)
  55 {
  56         return ((const char *) getenv("HOME"));
  57 }
  58
  59 /*
  60  * Create recursively directory using the FULL path.
  61  */
  62 static
  63 int _mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
  64 {
  65         int ret;
  66         char *p, tmp[PATH_MAX];
  67         size_t len;
  68         mode_t old_umask;
  69
  70         ret = snprintf(tmp, sizeof(tmp), "%s", path);
  71         if (ret < 0) {
  72                 PERROR("snprintf mkdir");
  73                 goto error;
  74         }
  75
  76         len = ret;
  77         if (tmp[len - 1] == '/') {
  78                 tmp[len - 1] = 0;
  79         }
  80
  81         old_umask = umask(0);
  82         for (p = tmp + 1; *p; p++) {
  83                 if (*p == '/') {
  84                         *p = 0;
  85                         ret = mkdir(tmp, mode);
  86                         if (ret < 0) {
  87                                 if (!(errno == EEXIST)) {
  88                                         PERROR("mkdir recursive");
  89                                         ret = -errno;
  90                                         goto umask_error;
  91                                 }
  92                         }
  93                         *p = '/';
  94                 }
  95         }
  96
  97         ret = mkdir(tmp, mode);
  98         if (ret < 0) {
  99                 if (!(errno == EEXIST)) {
 100                         PERROR("mkdir recursive last piece");
 101                         ret = -errno;
 102                 } else {
 103                         ret = 0;
 104                 }
 105         }
 106
 107 umask_error:
 108         umask(old_umask);
 109 error:
 110         return ret;
 111 }
 112
 113 static
 114 int run_as(int (*cmd)(const char *path, mode_t mode, uid_t uid, gid_t gid),
 115         const char *path, mode_t mode, uid_t uid, gid_t gid)
 116 {
 117         int ret = 0;
 118         pid_t pid;
 119
 120         /*
 121          * If we are non-root, we can only deal with our own uid.
 122          */
 123         if (geteuid() != 0) {
 124                 if (uid != geteuid()) {
 125                         ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)",
 126                                 uid, geteuid());
 127                         return -EPERM;
 128                 }
 129                 return (*cmd)(path, mode, uid, gid);
 130         }
 131
 132         pid = fork();
 133         if (pid > 0) {
 134                 int status;
 135
 136                 /*
 137                  * Parent: wait for child to return, in which case the
 138                  * shared memory map will have been created.
 139                  */
 140                 pid = wait(&status);
 141                 if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 142                         ret = -1;
 143                         goto end;
 144                 }
 145                 goto end;
 146         } else if (pid == 0) {
 147                 /* Child */
 148                 setegid(gid);
 149                 if (ret < 0) {
 150                         perror("setegid");
 151                         exit(EXIT_FAILURE);
 152                 }
 153                 ret = seteuid(uid);
 154                 if (ret < 0) {
 155                         perror("seteuid");
 156                         exit(EXIT_FAILURE);
 157                 }
 158                 ret = (*cmd)(path, mode, uid, gid);
 159                 if (!ret)
 160                         exit(EXIT_SUCCESS);
 161                 else
 162                         exit(EXIT_FAILURE);
 163         } else {
 164                 return -1;
 165         }
 166 end:
 167         return ret;
 168 }
 169
 170 int mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
 171 {
 172         DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d",
 173                         path, mode, uid, gid);
 174         return run_as(_mkdir_recursive, path, mode, uid, gid);
 175 }