/*- * atrun.c - run jobs queued by at; run with root privileges. * * SPDX-License-Identifier: BSD-2-Clause * * 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. */ #ifndef lint static const char rcsid[] = "$FreeBSD$"; #endif /* not lint */ /* System Headers */ #include #include #include #include #ifdef __FreeBSD__ #include #endif #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef __FreeBSD__ #include #else #include #endif #ifdef LOGIN_CAP #include #endif #ifdef PAM #include #include #endif /* Local headers */ #include "gloadavg.h" #define MAIN #include "privs.h" /* Macros */ #ifndef ATJOB_DIR #define ATJOB_DIR "/usr/spool/atjobs/" #endif #ifndef ATSPOOL_DIR #define ATSPOOL_DIR "/usr/spool/atspool/" #endif #ifndef LOADAVG_MX #define LOADAVG_MX 1.5 #endif /* File scope variables */ static const char * const atrun = "atrun"; /* service name for syslog etc. */ static int debug = 0; void perr(const char *fmt, ...); void perrx(const char *fmt, ...); static void usage(void) __dead2; /* Local functions */ static int write_string(int fd, const char* a) { return write(fd, a, strlen(a)); } #undef DEBUG_FORK #ifdef DEBUG_FORK static pid_t myfork(void) { pid_t res; res = fork(); if (res == 0) kill(getpid(),SIGSTOP); return res; } #define fork myfork #endif static void run_file(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 sends * mail to the user. */ pid_t pid; int fd_out, fd_in; int queue; char mailbuf[MAXLOGNAME], fmt[64]; char *mailname = NULL; FILE *stream; int send_mail = 0; struct stat buf, lbuf; off_t size; struct passwd *pentry; int fflags; long nuid; long ngid; #ifdef PAM pam_handle_t *pamh = NULL; int pam_err; struct pam_conv pamc = { .conv = openpam_nullconv, .appdata_ptr = NULL }; #endif 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. */ pentry = getpwuid(uid); if (pentry == NULL) perrx("Userid %lu not found - aborting job %s", (unsigned long) uid, filename); #ifdef PAM PRIV_START pam_err = pam_start(atrun, pentry->pw_name, &pamc, &pamh); if (pam_err != PAM_SUCCESS) perrx("cannot start PAM: %s", pam_strerror(pamh, pam_err)); pam_err = pam_acct_mgmt(pamh, PAM_SILENT); /* Expired password shouldn't prevent the job from running. */ if (pam_err != PAM_SUCCESS && pam_err != PAM_NEW_AUTHTOK_REQD) perrx("Account %s (userid %lu) unavailable for job %s: %s", pentry->pw_name, (unsigned long)uid, filename, pam_strerror(pamh, pam_err)); pam_end(pamh, pam_err); PRIV_END #endif /* PAM */ PRIV_START stream=fopen(filename, "r"); PRIV_END if (stream == NULL) perr("cannot open input file %s", filename); 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"); if (lstat(filename, &lbuf) == -1) perr("error in fstat of input file"); if (S_ISLNK(lbuf.st_mode)) perrx("Symbolic link encountered in job %s - aborting", filename); 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)) perrx("Somebody changed files from under us for job %s - aborting", filename); if (buf.st_nlink > 1) perrx("Somebody is trying to run a linked script for job %s", filename); if ((fflags = fcntl(fd_in, F_GETFD)) <0) perr("error in fcntl"); fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC); snprintf(fmt, sizeof(fmt), "#!/bin/sh\n# atrun uid=%%ld gid=%%ld\n# mail %%%ds %%d", MAXLOGNAME - 1); if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4) perrx("File %s is in wrong format - aborting", filename); if (mailbuf[0] == '-') perrx("Illegal mail name %s in %s", mailbuf, filename); mailname = mailbuf; if (nuid != uid) perrx("Job %s - userid %ld does not match file uid %lu", filename, nuid, (unsigned long)uid); if (ngid != gid) perrx("Job %s - groupid %ld does not match file gid %lu", filename, ngid, (unsigned long)gid); fclose(stream); if (chdir(ATSPOOL_DIR) < 0) perr("cannot chdir to %s", ATSPOOL_DIR); /* 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"); write_string(fd_out, "Subject: Output from your job "); write_string(fd_out, filename); write_string(fd_out, "\n\n"); fstat(fd_out, &buf); size = buf.st_size; close(STDIN_FILENO); close(STDOUT_FILENO); 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"); close(fd_in); close(fd_out); if (chdir(ATJOB_DIR) < 0) perr("cannot chdir to %s", ATJOB_DIR); queue = *filename; PRIV_START nice(tolower(queue) - 'a'); #ifdef LOGIN_CAP /* * For simplicity and safety, set all aspects of the user context * except for a selected subset: Don't set priority, which was * set based on the queue file name according to the tradition. * Don't bother to set environment, including path vars, either * because it will be discarded anyway. Although the job file * should set umask, preset it here just in case. */ if (setusercontext(NULL, pentry, uid, LOGIN_SETALL & ~(LOGIN_SETPRIORITY | LOGIN_SETPATH | LOGIN_SETENV)) != 0) exit(EXIT_FAILURE); /* setusercontext() logged the error */ #else /* LOGIN_CAP */ if (initgroups(pentry->pw_name,pentry->pw_gid)) perr("cannot init group access list"); if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0) perr("cannot change group"); if (setlogin(pentry->pw_name)) perr("cannot set login name"); if (setuid(uid) < 0 || seteuid(uid) < 0) perr("cannot set user id"); #endif /* LOGIN_CAP */ if (chdir(pentry->pw_dir)) chdir("/"); if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0) perr("exec failed for /bin/sh"); PRIV_END } /* We're the parent. Let's wait. */ close(fd_in); close(fd_out); waitpid(pid, (int *) NULL, 0); /* Send mail. Unlink the output file first, so it is deleted after * the run. */ stat(filename, &buf); if (open(filename, O_RDONLY) != STDIN_FILENO) perr("open of jobfile failed"); unlink(filename); if ((buf.st_size != size) || send_mail) { PRIV_START #ifdef LOGIN_CAP /* * This time set full context to run the mailer. */ if (setusercontext(NULL, pentry, uid, LOGIN_SETALL) != 0) exit(EXIT_FAILURE); /* setusercontext() logged the error */ #else /* LOGIN_CAP */ if (initgroups(pentry->pw_name,pentry->pw_gid)) perr("cannot init group access list"); if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0) perr("cannot change group"); if (setlogin(pentry->pw_name)) perr("cannot set login name"); if (setuid(uid) < 0 || seteuid(uid) < 0) perr("cannot set user id"); #endif /* LOGIN_CAP */ if (chdir(pentry->pw_dir)) chdir("/"); #ifdef __FreeBSD__ execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service", "-odi", "-oem", mailname, (char *) NULL); #else execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL); #endif perr("exec failed for mail command"); PRIV_END } exit(EXIT_SUCCESS); } /* Global functions */ /* Needed in gloadavg.c */ void perr(const char *fmt, ...) { const char * const fmtadd = ": %m"; char nfmt[strlen(fmt) + strlen(fmtadd) + 1]; va_list ap; va_start(ap, fmt); if (debug) { vwarn(fmt, ap); } else { snprintf(nfmt, sizeof(nfmt), "%s%s", fmt, fmtadd); vsyslog(LOG_ERR, nfmt, ap); } va_end(ap); exit(EXIT_FAILURE); } void perrx(const char *fmt, ...) { va_list ap; va_start(ap, fmt); if (debug) vwarnx(fmt, ap); else vsyslog(LOG_ERR, fmt, ap); va_end(ap); exit(EXIT_FAILURE); } int main(int argc, char *argv[]) { /* Browse through ATJOB_DIR, 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; unsigned long 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; #ifdef __FreeBSD__ size_t ncpusz; double load_avg = -1; int ncpu; #else double load_avg = LOADAVG_MX; #endif /* We don't need root privileges all the time; running under uid and gid daemon * is fine. */ RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID) openlog(atrun, LOG_PID, LOG_CRON); opterr = 0; while((c=getopt(argc, argv, "dl:"))!= -1) { switch (c) { case 'l': if (sscanf(optarg, "%lf", &load_avg) != 1) perr("garbled option -l"); #ifndef __FreeBSD__ if (load_avg <= 0.) load_avg = LOADAVG_MX; #endif break; case 'd': debug ++; break; case '?': default: usage(); } } if (chdir(ATJOB_DIR) != 0) perr("cannot change to %s", ATJOB_DIR); #ifdef __FreeBSD__ if (load_avg <= 0.) { ncpusz = sizeof(size_t); if (sysctlbyname("hw.ncpu", &ncpu, &ncpusz, NULL, 0) < 0) ncpu = 1; load_avg = LOADAVG_MX * ncpu; } #endif /* 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) perr("cannot read %s", ATJOB_DIR); if (flock(dirfd(spool), LOCK_EX) == -1) perr("cannot lock %s", ATJOB_DIR); now = time(NULL); run_batch = 0; batch_uid = (uid_t) -1; batch_gid = (gid_t) -1; while ((dirent = readdir(spool)) != NULL) { if (stat(dirent->d_name,&buf) != 0) perr("cannot stat in %s", ATJOB_DIR); /* We don't want directories */ if (!S_ISREG(buf.st_mode)) continue; if (sscanf(dirent->d_name,"%c%5lx%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; strlcpy(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)) unlink(dirent->d_name); } /* run the single batch file, if any */ if (run_batch && (gloadavg() < load_avg)) run_file(batch_name, batch_uid, batch_gid); if (flock(dirfd(spool), LOCK_UN) == -1) perr("cannot unlock %s", ATJOB_DIR); if (closedir(spool) == -1) perr("cannot closedir %s", ATJOB_DIR); closelog(); exit(EXIT_SUCCESS); } static void usage(void) { if (debug) fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n"); else syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]"); exit(EXIT_FAILURE); }