1 /* $NetBSD: atrun.c,v 1.4 1997/10/07 10:49:16 mrg Exp $ */ 2 3 /* 4 * atrun.c - run jobs queued by at; run with root privileges. 5 * Copyright (c) 1993 by Thomas Koenig 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. The name of the author(s) may not be used to endorse or promote 14 * products derived from this software without specific prior written 15 * permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 /* System Headers */ 30 31 #include <sys/types.h> 32 #include <sys/fcntl.h> 33 #include <sys/stat.h> 34 #include <sys/wait.h> 35 #include <dirent.h> 36 #include <errno.h> 37 #include <pwd.h> 38 #include <signal.h> 39 #include <stddef.h> 40 #include <stdio.h> 41 #include <stdlib.h> 42 #include <string.h> 43 #include <time.h> 44 #include <unistd.h> 45 #include <syslog.h> 46 47 #include <paths.h> 48 49 /* Local headers */ 50 51 #define MAIN 52 #include "privs.h" 53 #include "pathnames.h" 54 #include "atrun.h" 55 56 static void perr __P((const char *)); 57 static int write_string __P((int, const char *)); 58 static void run_file __P((const char *, uid_t)); 59 int main __P((int, char *[])); 60 61 /* File scope variables */ 62 63 static char *namep; 64 #ifndef lint 65 __RCSID("$NetBSD: atrun.c,v 1.4 1997/10/07 10:49:16 mrg Exp $"); 66 #endif 67 68 /* Local functions */ 69 static void 70 perr(a) 71 const char *a; 72 { 73 syslog(LOG_ERR, "%s: %m", a); 74 exit(EXIT_FAILURE); 75 } 76 77 static int 78 write_string(fd, a) 79 int fd; 80 const char *a; 81 { 82 return write(fd, a, strlen(a)); 83 } 84 85 static void 86 run_file(filename, uid) 87 const char *filename; 88 uid_t uid; 89 { 90 /* 91 * Run a file by by spawning off a process which redirects I/O, 92 * spawns a subshell, then waits for it to complete and spawns another 93 * process to send mail to the user. 94 */ 95 pid_t pid; 96 int fd_out, fd_in; 97 int queue; 98 char mailbuf[9]; 99 char *mailname = NULL; 100 FILE *stream; 101 int send_mail = 0; 102 struct stat buf; 103 off_t size; 104 struct passwd *pentry; 105 int fflags; 106 107 pid = fork(); 108 if (pid == -1) 109 perr("Cannot fork"); 110 else if (pid > 0) 111 return; 112 113 /* 114 * Let's see who we mail to. Hopefully, we can read it from the 115 * command file; if not, send it to the owner, or, failing that, to 116 * root. 117 */ 118 119 PRIV_START 120 121 stream = fopen(filename, "r"); 122 123 PRIV_END 124 125 pentry = getpwuid(uid); 126 if (pentry == NULL) 127 perr("UID not in password file!"); 128 129 if (stream == NULL) 130 perr("Cannot open input file"); 131 132 if ((fd_in = dup(fileno(stream))) < 0) 133 perr("Error duplicating input file descriptor"); 134 135 if ((fflags = fcntl(fd_in, F_GETFD)) < 0) 136 perr("Error in fcntl"); 137 138 fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); 139 140 if (fscanf(stream, "#! /bin/sh\n# mail %8s %d", mailbuf, &send_mail) == 2) { 141 mailname = mailbuf; 142 } else { 143 mailname = pentry->pw_name; 144 } 145 fclose(stream); 146 if (chdir(_PATH_ATSPOOL) < 0) 147 perr("Cannot chdir to " _PATH_ATSPOOL); 148 149 /* 150 * Create a file to hold the output of the job we are about to 151 * run. Write the mail header. 152 */ 153 if ((fd_out = open(filename, 154 O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0) 155 perr("Cannot create output file"); 156 157 write_string(fd_out, "Subject: Output from your job "); 158 write_string(fd_out, filename); 159 write_string(fd_out, "\n\n"); 160 fstat(fd_out, &buf); 161 size = buf.st_size; 162 163 close(STDIN_FILENO); 164 close(STDOUT_FILENO); 165 close(STDERR_FILENO); 166 167 pid = fork(); 168 if (pid < 0) 169 perr("Error in fork"); 170 else if (pid == 0) { 171 char *nul = NULL; 172 char **nenvp = &nul; 173 174 /* 175 * Set up things for the child; we want standard input from 176 * the input file, and standard output and error sent to 177 * our output file. 178 */ 179 180 if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0) 181 perr("Error in lseek"); 182 183 if (dup(fd_in) != STDIN_FILENO) 184 perr("Error in I/O redirection"); 185 186 if (dup(fd_out) != STDOUT_FILENO) 187 perr("Error in I/O redirection"); 188 189 if (dup(fd_out) != STDERR_FILENO) 190 perr("Error in I/O redirection"); 191 192 close(fd_in); 193 close(fd_out); 194 if (chdir(_PATH_ATJOBS) < 0) 195 perr("Cannot chdir to " _PATH_ATJOBS); 196 197 queue = *filename; 198 199 PRIV_START 200 201 if (queue > 'b') 202 nice(queue - 'b'); 203 204 if (initgroups(pentry->pw_name, pentry->pw_gid) < 0) 205 perr("Cannot init group list"); 206 207 if (setgid(pentry->pw_gid) < 0) 208 perr("Cannot change primary group"); 209 210 if (setuid(uid) < 0) 211 perr("Cannot set user id"); 212 213 chdir("/"); 214 215 if (execle("/bin/sh", "sh", (char *) NULL, nenvp) != 0) 216 perr("Exec failed"); 217 218 PRIV_END 219 } 220 /* We're the parent. Let's wait. */ 221 close(fd_in); 222 close(fd_out); 223 waitpid(pid, (int *) NULL, 0); 224 225 stat(filename, &buf); 226 if ((buf.st_size != size) || send_mail) { 227 /* Fork off a child for sending mail */ 228 pid = fork(); 229 if (pid < 0) 230 perr("Fork failed"); 231 else if (pid == 0) { 232 if (open(filename, O_RDONLY) != STDIN_FILENO) 233 perr("Cannot reopen output file"); 234 235 execl(_PATH_SENDMAIL, _PATH_SENDMAIL, mailname, 236 (char *) NULL); 237 perr("Exec failed"); 238 } 239 waitpid(pid, (int *) NULL, 0); 240 } 241 unlink(filename); 242 exit(EXIT_SUCCESS); 243 } 244 245 /* Global functions */ 246 247 int 248 main(argc, argv) 249 int argc; 250 char *argv[]; 251 { 252 /* 253 * Browse through _PATH_ATJOBS, checking all the jobfiles wether 254 * they should be executed and or deleted. The queue is coded into 255 * the first byte of the job filename, the date (in minutes since 256 * Eon) as a hex number in the following eight bytes, followed by 257 * a dot and a serial number. A file which has not been executed 258 * yet is denoted by its execute - bit set. For those files which 259 * are to be executed, run_file() is called, which forks off a 260 * child which takes care of I/O redirection, forks off another 261 * child for execution and yet another one, optionally, for sending 262 * mail. Files which already have run are removed during the 263 * next invocation. 264 */ 265 DIR *spool; 266 struct dirent *dirent; 267 struct stat buf; 268 int older; 269 unsigned long ctm; 270 char queue; 271 272 /* 273 * We don't need root privileges all the time; running under uid 274 * and gid daemon is fine. 275 */ 276 277 RELINQUISH_PRIVS_ROOT(0) /* it's setuid root */ 278 openlog("atrun", LOG_PID, LOG_CRON); 279 280 namep = argv[0]; 281 if (chdir(_PATH_ATJOBS) != 0) 282 perr("Cannot change to " _PATH_ATJOBS); 283 284 /* 285 * Main loop. Open spool directory for reading and look over all 286 * the files in there. If the filename indicates that the job 287 * should be run and the x bit is set, fork off a child which sets 288 * its user and group id to that of the files and exec a /bin/sh 289 * which executes the shell script. Unlink older files if they 290 * should no longer be run. For deletion, their r bit has to be 291 * turned on. 292 */ 293 if ((spool = opendir(".")) == NULL) 294 perr("Cannot read " _PATH_ATJOBS); 295 296 while ((dirent = readdir(spool)) != NULL) { 297 double la; 298 299 if (stat(dirent->d_name, &buf) != 0) 300 perr("Cannot stat in " _PATH_ATJOBS); 301 302 /* We don't want directories */ 303 if (!S_ISREG(buf.st_mode)) 304 continue; 305 306 if (sscanf(dirent->d_name, "%c%8lx", &queue, &ctm) != 2) 307 continue; 308 309 if ((queue == 'b') && ((getloadavg(&la, 1) != 1) || 310 (la > ATRUN_MAXLOAD))) 311 continue; 312 313 older = (time_t) ctm *60 <= time(NULL); 314 315 /* The file is executable and old enough */ 316 if (older && (S_IXUSR & buf.st_mode)) { 317 /* 318 * Now we know we want to run the file, we can turn 319 * off the execute bit 320 */ 321 322 PRIV_START 323 324 if (chmod(dirent->d_name, S_IRUSR) != 0) 325 perr("Cannot change file permissions"); 326 327 PRIV_END 328 329 run_file(dirent->d_name, buf.st_uid); 330 } 331 /* Delete older files */ 332 if (older && !(S_IXUSR & buf.st_mode) && 333 (S_IRUSR & buf.st_mode)) 334 unlink(dirent->d_name); 335 } 336 closelog(); 337 exit(EXIT_SUCCESS); 338 } 339