/* $OpenBSD: atrun.c,v 1.15 2001/08/27 16:18:58 deraadt Exp $ */ /* * atrun.c - run jobs queued by at; run with root privileges. * Copyright (C) 1993, 1994 Thomas Koenig * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. The name of the author(s) may not be used to endorse or promote * products derived from this software without specific prior written * permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ /* System Headers */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* Local headers */ #define MAIN #include "privs.h" #include "pathnames.h" #include "atrun.h" /* File scope defines */ #if (MAXLOGNAME-1) > UT_NAMESIZE #define LOGNAMESIZE UT_NAMESIZE #else #define LOGNAMESIZE (MAXLOGNAME-1) #endif /* File scope variables */ static char *namep; static char rcsid[] = "$OpenBSD: atrun.c,v 1.15 2001/08/27 16:18:58 deraadt Exp $"; static int debug = 0; /* Local functions */ static void perr(a) const char *a; { if (debug) perror(a); else syslog(LOG_ERR, "%s: %m", a); exit(EXIT_FAILURE); } static void perr2(a, b) char *a, *b; { if (debug) { (void)fputs(a, stderr); perror(b); } else syslog(LOG_ERR, "%s%s: %m", a, b); exit(EXIT_FAILURE); } static int write_string(fd, a) int fd; const char *a; { return(write(fd, a, strlen(a))); } static void run_file(filename, uid, gid) const char *filename; uid_t uid; gid_t gid; { /* * Run a file by spawning off a process which redirects I/O, * spawns a subshell, then waits for it to complete and spawns another * process to send mail to the user. */ pid_t pid; int fd_out, fd_in; int queue; char mailbuf[LOGNAMESIZE + 1], *fmt; char *mailname = NULL; FILE *stream; int send_mail = 0; struct stat buf, lbuf; off_t size; struct passwd *pw; int fflags; uid_t nuid; gid_t ngid; login_cap_t *lc; PRIV_START if (chmod(filename, S_IRUSR) != 0) perr("Cannot change file permissions"); PRIV_END pid = fork(); if (pid == -1) perr("Cannot fork"); else if (pid != 0) return; /* * Let's see who we mail to. Hopefully, we can read it from the * command file; if not, send it to the owner, or, failing that, to * root. */ pw = getpwuid(uid); if (pw == NULL) { syslog(LOG_ERR,"Userid %u not found - aborting job %s", uid, filename); exit(EXIT_FAILURE); } PRIV_START stream = fopen(filename, "r"); PRIV_END if (pw->pw_expire && time(NULL) >= pw->pw_expire) { syslog(LOG_ERR, "Userid %u has expired - aborting job %s", uid, filename); exit(EXIT_FAILURE); } if (stream == NULL) perr("Cannot open input file"); if ((fd_in = dup(fileno(stream))) < 0) perr("Error duplicating input file descriptor"); if (fstat(fd_in, &buf) == -1) perr("Error in fstat of input file descriptor"); PRIV_START if (lstat(filename, &lbuf) == -1) perr("Error in lstat of input file"); PRIV_END if (S_ISLNK(lbuf.st_mode)) { syslog(LOG_ERR, "Symbolic link encountered in job %s - aborting", filename); exit(EXIT_FAILURE); } if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) || (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) || (lbuf.st_size!=buf.st_size)) { syslog(LOG_ERR, "Somebody changed files from under us for job %s - aborting", filename); exit(EXIT_FAILURE); } if (buf.st_nlink > 1) { syslog(LOG_ERR, "Somebody is trying to run a linked script for job %s", filename); exit(EXIT_FAILURE); } if ((fflags = fcntl(fd_in, F_GETFD)) < 0) perr("Error in fcntl"); (void)fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); (void) asprintf(&fmt, "#!/bin/sh\n# atrun uid=%%u gid=%%u\n# mail %%%ds %%d", LOGNAMESIZE); if (fmt == NULL) { syslog(LOG_ERR, "out of memory - aborting"); exit(EXIT_FAILURE); } if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) { syslog(LOG_ERR, "File %s is in wrong format - aborting", filename); free(fmt); exit(EXIT_FAILURE); } free(fmt); if (mailbuf[0] == '-') { syslog(LOG_ERR, "illegal mail name %s in %s", mailbuf, filename); exit(EXIT_FAILURE); } mailname = mailbuf; if (nuid != uid) { syslog(LOG_ERR, "Job %s - userid %u does not match file uid %u", filename, nuid, uid); exit(EXIT_FAILURE); } if (ngid != gid) { syslog(LOG_ERR, "Job %s - groupid %u does not match file gid %u", filename, ngid, gid); exit(EXIT_FAILURE); } (void)fclose(stream); PRIV_START if (chdir(_PATH_ATSPOOL) < 0) perr2("Cannot chdir to ", _PATH_ATSPOOL); /* * Create a file to hold the output of the job we are about to * run. Write the mail header. */ if ((fd_out = open(filename, O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0) perr("Cannot create output file"); PRIV_END write_string(fd_out, "To: "); write_string(fd_out, mailname); write_string(fd_out, "\nSubject: Output from your job "); write_string(fd_out, filename); write_string(fd_out, "\n\n"); if (fstat(fd_out, &buf) == -1) perr("Error in fstat of output file descriptor"); size = buf.st_size; (void)close(STDIN_FILENO); (void)close(STDOUT_FILENO); (void)close(STDERR_FILENO); pid = fork(); if (pid < 0) perr("Error in fork"); else if (pid == 0) { char *nul = NULL; char **nenvp = &nul; /* * Set up things for the child; we want standard input from * the input file, and standard output and error sent to * our output file. */ if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0) perr("Error in lseek"); if (dup(fd_in) != STDIN_FILENO) perr("Error in I/O redirection"); if (dup(fd_out) != STDOUT_FILENO) perr("Error in I/O redirection"); if (dup(fd_out) != STDERR_FILENO) perr("Error in I/O redirection"); (void)close(fd_in); (void)close(fd_out); PRIV_START if (chdir(_PATH_ATJOBS) < 0) perr2("Cannot chdir to ", _PATH_ATJOBS); if ((lc = login_getclass(pw->pw_class)) == NULL) perr("Cannot get login class"); if (setusercontext(lc, pw, pw->pw_uid, LOGIN_SETALL) < 0) perr("Cannot set user context"); if (auth_approval(NULL, lc, pw->pw_name, "at") <= 0) perr2("Approval failure for ", pw->pw_name); login_close(lc); if (chdir(pw->pw_dir) < 0) chdir("/"); /* First letter indicates requested job priority */ queue = tolower((unsigned char) *filename); if (queue > 'b') (void) setpriority(PRIO_PROCESS, 0, queue - 'b'); if (execle(_PATH_BSHELL, "sh", (char *)NULL, nenvp) != 0) perr("Exec failed for /bin/sh"); PRIV_END } /* We're the parent. Let's wait. */ (void)close(fd_in); (void)close(fd_out); waitpid(pid, (int *)NULL, 0); /* * Send mail. Unlink the output file first, so it is deleted * after the run. */ PRIV_START if (stat(filename, &buf) == -1) perr("Error in stat of output file"); if (open(filename, O_RDONLY) != STDIN_FILENO) perr("Open of jobfile failed"); (void)unlink(filename); PRIV_END if ((buf.st_size != size) || send_mail) { /* Fork off a child for sending mail */ PRIV_START if (setusercontext(0, pw, pw->pw_uid, LOGIN_SETALL) < 0) perr("Cannot set user context"); if (chdir(pw->pw_dir)) chdir("/"); execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", "-odi", "-oem", "-t", (char *)NULL); perr("Exec failed for mail command"); PRIV_END } exit(EXIT_SUCCESS); } /* Global functions */ int main(argc, argv) int argc; char *argv[]; { /* * Browse through _PATH_ATJOBS, checking all the jobfiles wether * they should be executed and or deleted. The queue is coded into * the first byte of the job filename, the date (in minutes since * Eon) as a hex number in the following eight bytes, followed by * a dot and a serial number. A file which has not been executed * yet is denoted by its execute - bit set. For those files which * are to be executed, run_file() is called, which forks off a * child which takes care of I/O redirection, forks off another * child for execution and yet another one, optionally, for sending * mail. Files which already have run are removed during the * next invocation. */ DIR *spool; struct dirent *dirent; struct stat buf; unsigned long ctm; int jobno; char queue; time_t now, run_time; char batch_name[] = "Z2345678901234"; uid_t batch_uid; gid_t batch_gid; int c; int run_batch; double la, load_avg = ATRUN_MAXLOAD; /* * We don't need root privileges all the time; running under uid * and gid nobody is fine except for priviledged operations. */ RELINQUISH_PRIVS_ROOT(NOBODY_UID, NOBODY_GID) openlog("atrun", LOG_PID, LOG_CRON); opterr = 0; errno = 0; while ((c = getopt(argc, argv, "dl:")) != -1) { switch (c) { case 'l': if (sscanf(optarg, "%lf", &load_avg) != 1) perr("garbled option -l"); if (load_avg <= 0.) load_avg = ATRUN_MAXLOAD; break; case 'd': debug++; break; case '?': perr("unknown option"); break; default: perr("idiotic option - aborted"); break; } } namep = argv[0]; PRIV_START if (chdir(_PATH_ATJOBS) != 0) perr2("Cannot change to ", _PATH_ATJOBS); /* * Main loop. Open spool directory for reading and look over all * the files in there. If the filename indicates that the job * should be run and the x bit is set, fork off a child which sets * its user and group id to that of the files and exec a /bin/sh * which executes the shell script. Unlink older files if they * should no longer be run. For deletion, their r bit has to be * turned on. * * Also, pick the oldest batch job to run, at most one per * invocation of atrun. */ if ((spool = opendir(".")) == NULL) perr2("Cannot read ", _PATH_ATJOBS); PRIV_END now = time(NULL); run_batch = 0; batch_uid = (uid_t) -1; batch_gid = (gid_t) -1; while ((dirent = readdir(spool)) != NULL) { PRIV_START if (stat(dirent->d_name, &buf) != 0) perr2("Cannot stat in ", _PATH_ATJOBS); PRIV_END /* We don't want directories */ if (!S_ISREG(buf.st_mode)) continue; if (sscanf(dirent->d_name, "%c%5x%8lx", &queue, &jobno, &ctm) != 3) continue; run_time = (time_t) ctm * 60; if ((S_IXUSR & buf.st_mode) && (run_time <= now)) { if (isupper(queue) && (strcmp(batch_name, dirent->d_name) > 0)) { run_batch = 1; (void)strncpy(batch_name, dirent->d_name, sizeof(batch_name)); batch_uid = buf.st_uid; batch_gid = buf.st_gid; } /* The file is executable and old enough */ if (islower(queue)) run_file(dirent->d_name, buf.st_uid, buf.st_gid); } /* Delete older files */ if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode)) { PRIV_START (void)unlink(dirent->d_name); PRIV_END } } /* Run the single batch file, if any */ if (run_batch && ((getloadavg(&la, 1) == 1) && la < load_avg)) run_file(batch_name, batch_uid, batch_gid); closelog(); exit(EXIT_SUCCESS); }