os.c

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#ifdef HAVE_LINUXTHREADS
	mainpid = getpid();
#endif

	if (setsid() == -1) {
		isc__strerror(errno, strbuf, sizeof(strbuf));
		ns_main_earlyfatal("setsid(): %s", strbuf);
	}

	/*
	 * Try to set stdin, stdout, and stderr to /dev/null, but press
	 * on even if it fails.
	 *
	 * XXXMLG The close() calls here are unneeded on all but NetBSD, but
	 * are harmless to include everywhere.  dup2() is supposed to close
	 * the FD if it is in use, but unproven-pthreads-0.16 is broken
	 * and will end up closing the wrong FD.  This will be fixed eventually,
	 * and these calls will be removed.
	 */
	if (devnullfd != -1) {
		if (devnullfd != STDIN_FILENO) {
			(void)close(STDIN_FILENO);
			(void)dup2(devnullfd, STDIN_FILENO);
		}
		if (devnullfd != STDOUT_FILENO) {
			(void)close(STDOUT_FILENO);
			(void)dup2(devnullfd, STDOUT_FILENO);
		}
		if (devnullfd != STDERR_FILENO) {
			(void)close(STDERR_FILENO);
			(void)dup2(devnullfd, STDERR_FILENO);
		}
	}
}

void
ns_os_started(void) {
	char buf = 0;

	/*
	 * Signal to the parent that we stated successfully.
	 */
	if (dfd[0] != -1 && dfd[1] != -1) {
		write(dfd[1], &buf, 1);
		close(dfd[1]);
		dfd[0] = dfd[1] = -1;
	}
}

void
ns_os_opendevnull(void) {
	devnullfd = open("/dev/null", O_RDWR, 0);
}

void
ns_os_closedevnull(void) {
	if (devnullfd != STDIN_FILENO &&
	    devnullfd != STDOUT_FILENO &&
	    devnullfd != STDERR_FILENO) {
		close(devnullfd);
		devnullfd = -1;
	}
}

static isc_boolean_t
all_digits(const char *s) {
	if (*s == '\0')
		return (ISC_FALSE);
	while (*s != '\0') {
		if (!isdigit((*s)&0xff))
			return (ISC_FALSE);
		s++;
	}
	return (ISC_TRUE);
}

void
ns_os_chroot(const char *root) {
	char strbuf[ISC_STRERRORSIZE];
#ifdef HAVE_LIBSCF
	ns_smf_chroot = 0;
#endif
	if (root != NULL) {
		if (chroot(root) < 0) {
			isc__strerror(errno, strbuf, sizeof(strbuf));
			ns_main_earlyfatal("chroot(): %s", strbuf);
		}
		if (chdir("/") < 0) {
			isc__strerror(errno, strbuf, sizeof(strbuf));
			ns_main_earlyfatal("chdir(/): %s", strbuf);
		}
#ifdef HAVE_LIBSCF
		/* Set ns_smf_chroot flag on successful chroot. */
		ns_smf_chroot = 1;
#endif
	}
}

void
ns_os_inituserinfo(const char *username) {
	char strbuf[ISC_STRERRORSIZE];
	if (username == NULL)
		return;

	if (all_digits(username))
		runas_pw = getpwuid((uid_t)atoi(username));
	else
		runas_pw = getpwnam(username);
	endpwent();

	if (runas_pw == NULL)
		ns_main_earlyfatal("user '%s' unknown", username);

	if (getuid() == 0) {
		if (initgroups(runas_pw->pw_name, runas_pw->pw_gid) < 0) {
			isc__strerror(errno, strbuf, sizeof(strbuf));
			ns_main_earlyfatal("initgroups(): %s", strbuf);
		}
	}

}

void
ns_os_changeuser(void) {
	char strbuf[ISC_STRERRORSIZE];
	if (runas_pw == NULL || done_setuid)
		return;

	done_setuid = ISC_TRUE;

#ifdef HAVE_LINUXTHREADS
#ifdef HAVE_LINUX_CAPABILITY_H
	if (!non_root_caps)
		ns_main_earlyfatal("-u with Linux threads not supported: "
				   "requires kernel support for "
				   "prctl(PR_SET_KEEPCAPS)");
#else
	ns_main_earlyfatal("-u with Linux threads not supported: "
			   "no capabilities support or capabilities "
			   "disabled at build time");
#endif
#endif

	if (setgid(runas_pw->pw_gid) < 0) {
		isc__strerror(errno, strbuf, sizeof(strbuf));
		ns_main_earlyfatal("setgid(): %s", strbuf);
	}

	if (setuid(runas_pw->pw_uid) < 0) {
		isc__strerror(errno, strbuf, sizeof(strbuf));
		ns_main_earlyfatal("setuid(): %s", strbuf);
	}

#if defined(HAVE_LINUX_CAPABILITY_H) && !defined(HAVE_LINUXTHREADS)
	linux_minprivs();
#endif
}

void
ns_os_minprivs(void) {
#ifdef HAVE_SYS_PRCTL_H
	linux_keepcaps();
#endif

#ifdef HAVE_LINUXTHREADS
	ns_os_changeuser(); /* Call setuid() before threads are started */
#endif

#if defined(HAVE_LINUX_CAPABILITY_H) && defined(HAVE_LINUXTHREADS)
	linux_minprivs();
#endif
}

static int
safe_open(const char *filename, isc_boolean_t append) {
	int fd;
	struct stat sb;

	if (stat(filename, &sb) == -1) {
		if (errno != ENOENT)
			return (-1);
	} else if ((sb.st_mode & S_IFREG) == 0) {
		errno = EOPNOTSUPP;
		return (-1);
	}

	if (append)
		fd = open(filename, O_WRONLY|O_CREAT|O_APPEND,
			  S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH);
	else {
		(void)unlink(filename);
		fd = open(filename, O_WRONLY|O_CREAT|O_EXCL,
			  S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH);
	}
	return (fd);
}

static void
cleanup_pidfile(void) {
	if (pidfile != NULL) {
		(void)unlink(pidfile);
		free(pidfile);
	}
	pidfile = NULL;
}

void
ns_os_writepidfile(const char *filename, isc_boolean_t first_time) {
	int fd;
	FILE *lockfile;
	size_t len;
	pid_t pid;
	char strbuf[ISC_STRERRORSIZE];
	void (*report)(const char *, ...);

	/*
	 * The caller must ensure any required synchronization.
	 */

	report = first_time ? ns_main_earlyfatal : ns_main_earlywarning;

	cleanup_pidfile();

	if (filename == NULL)
		return;

	len = strlen(filename);
	pidfile = malloc(len + 1);
	if (pidfile == NULL) {
		isc__strerror(errno, strbuf, sizeof(strbuf));
		(*report)("couldn't malloc '%s': %s", filename, strbuf);
		return;
	}
	/* This is safe. */
	strcpy(pidfile, filename);

	fd = safe_open(filename, ISC_FALSE);
	if (fd < 0) {
		isc__strerror(errno, strbuf, sizeof(strbuf));
		(*report)("couldn't open pid file '%s': %s", filename, strbuf);
		free(pidfile);
		pidfile = NULL;
		return;
	}
	lockfile = fdopen(fd, "w");
	if (lockfile == NULL) {
		isc__strerror(errno, strbuf, sizeof(strbuf));
		(*report)("could not fdopen() pid file '%s': %s",
			  filename, strbuf);
		(void)close(fd);
		cleanup_pidfile();
		return;
	}
#ifdef HAVE_LINUXTHREADS
	pid = mainpid;
#else
	pid = getpid();
#endif
	if (fprintf(lockfile, "%ld\n", (long)pid) < 0) {
		(*report)("fprintf() to pid file '%s' failed", filename);
		(void)fclose(lockfile);
		cleanup_pidfile();
		return;
	}
	if (fflush(lockfile) == EOF) {
		(*report)("fflush() to pid file '%s' failed", filename);
		(void)fclose(lockfile);
		cleanup_pidfile();
		return;
	}
	(void)fclose(lockfile);
}

void
ns_os_shutdown(void) {
	closelog();
	cleanup_pidfile();
}

isc_result_t
ns_os_gethostname(char *buf, size_t len) {
	int n;

	n = gethostname(buf, len);
	return ((n == 0) ? ISC_R_SUCCESS : ISC_R_FAILURE);
}

static char *
next_token(char **stringp, const char *delim) {
	char *res;

	do {
		res = strsep(stringp, delim);
		if (res == NULL)
			break;
	} while (*res == '\0');
	return (res);
}

void
ns_os_shutdownmsg(char *command, isc_buffer_t *text) {
	char *input, *ptr;
	unsigned int n;
	pid_t pid;

	input = command;

	/* Skip the command name. */
	ptr = next_token(&input, " \t");
	if (ptr == NULL)
		return;

	ptr = next_token(&input, " \t");
	if (ptr == NULL)
		return;
	
	if (strcmp(ptr, "-p") != 0)
		return;

#ifdef HAVE_LINUXTHREADS
	pid = mainpid;
#else
	pid = getpid();
#endif

	n = snprintf((char *)isc_buffer_used(text),
		     isc_buffer_availablelength(text),
		     "pid: %ld", (long)pid);
	/* Only send a message if it is complete. */
	if (n < isc_buffer_availablelength(text))
		isc_buffer_add(text, n);
}

void
ns_os_tzset(void) {
#ifdef HAVE_TZSET
	tzset();
#endif
}