diff options
Diffstat (limited to 'util.c')
| -rw-r--r-- | util.c | 315 |
1 files changed, 315 insertions, 0 deletions
@@ -37,6 +37,10 @@ #include <sys/ioctl.h> #include <linux/vt.h> #include <linux/tiocl.h> +#include <termios.h> +#include <stdarg.h> +#include <sys/inotify.h> +#include <sys/poll.h> #include "macro.h" #include "util.h" @@ -164,11 +168,14 @@ int close_nointr(int fd) { } void close_nointr_nofail(int fd) { + int saved_errno = errno; /* like close_nointr() but cannot fail, and guarantees errno * is unchanged */ assert_se(close_nointr(fd) == 0); + + errno = saved_errno; } int parse_boolean(const char *v) { @@ -1322,6 +1329,314 @@ int chvt(int vt) { return r; } +int read_one_char(FILE *f, char *ret, bool *need_nl) { + struct termios old_termios, new_termios; + char c; + char line[1024]; + + assert(f); + assert(ret); + + if (tcgetattr(fileno(f), &old_termios) >= 0) { + new_termios = old_termios; + + new_termios.c_lflag &= ~ICANON; + new_termios.c_cc[VMIN] = 1; + new_termios.c_cc[VTIME] = 0; + + if (tcsetattr(fileno(f), TCSADRAIN, &new_termios) >= 0) { + size_t k; + + k = fread(&c, 1, 1, f); + + tcsetattr(fileno(f), TCSADRAIN, &old_termios); + + if (k <= 0) + return -EIO; + + if (need_nl) + *need_nl = c != '\n'; + + *ret = c; + return 0; + } + } + + if (!(fgets(line, sizeof(line), f))) + return -EIO; + + truncate_nl(line); + + if (strlen(line) != 1) + return -EBADMSG; + + if (need_nl) + *need_nl = false; + + *ret = line[0]; + return 0; +} + +int ask(char *ret, const char *replies, const char *text, ...) { + assert(ret); + assert(replies); + assert(text); + + for (;;) { + va_list ap; + char c; + int r; + bool need_nl = true; + + va_start(ap, text); + vprintf(text, ap); + va_end(ap); + + fflush(stdout); + + if ((r = read_one_char(stdin, &c, &need_nl)) < 0) { + + if (r == -EBADMSG) { + puts("Bad input, please try again."); + continue; + } + + putchar('\n'); + return r; + } + + if (need_nl) + putchar('\n'); + + if (strchr(replies, c)) { + *ret = c; + return 0; + } + + puts("Read unexpected character, please try again."); + } +} + +int reset_terminal(int fd) { + struct termios termios; + int r = 0; + + assert(fd >= 0); + + /* Set terminal up for job control */ + + if (tcgetattr(fd, &termios) < 0) { + r = -errno; + goto finish; + } + + termios.c_iflag &= ~(IGNBRK | BRKINT); + termios.c_iflag |= ICRNL | IMAXBEL | IUTF8; + termios.c_oflag |= ONLCR; + termios.c_cflag |= CREAD; + termios.c_lflag = ISIG | ICANON | IEXTEN | ECHO | ECHOE | ECHOK | ECHOCTL | ECHOPRT | ECHOKE; + + termios.c_cc[VINTR] = 03; /* ^C */ + termios.c_cc[VQUIT] = 034; /* ^\ */ + termios.c_cc[VERASE] = 0177; + termios.c_cc[VKILL] = 025; /* ^X */ + termios.c_cc[VEOF] = 04; /* ^D */ + termios.c_cc[VSTART] = 021; /* ^Q */ + termios.c_cc[VSTOP] = 023; /* ^S */ + termios.c_cc[VSUSP] = 032; /* ^Z */ + termios.c_cc[VLNEXT] = 026; /* ^V */ + termios.c_cc[VWERASE] = 027; /* ^W */ + termios.c_cc[VREPRINT] = 022; /* ^R */ + + termios.c_cc[VTIME] = 0; + termios.c_cc[VMIN] = 1; + + if (tcsetattr(fd, TCSANOW, &termios) < 0) + r = -errno; + +finish: + /* Just in case, flush all crap out */ + tcflush(fd, TCIOFLUSH); + + return r; +} + +int open_terminal(const char *name, int mode) { + int fd, r; + + if ((fd = open(name, mode)) < 0) + return -errno; + + if ((r = isatty(fd)) < 0) { + close_nointr_nofail(fd); + return -errno; + } + + if (!r) { + close_nointr_nofail(fd); + return -ENOTTY; + } + + return fd; +} + +int flush_fd(int fd) { + struct pollfd pollfd; + + zero(pollfd); + pollfd.fd = fd; + pollfd.events = POLLIN; + + for (;;) { + char buf[1024]; + ssize_t l; + int r; + + if ((r = poll(&pollfd, 1, 0)) < 0) { + + if (errno == EINTR) + continue; + + return -errno; + } + + if (r == 0) + return 0; + + if ((l = read(fd, buf, sizeof(buf))) < 0) { + + if (errno == EINTR) + continue; + + if (errno == EAGAIN) + return 0; + + return -errno; + } + + if (l <= 0) + return 0; + } +} + +int acquire_terminal(const char *name, bool fail, bool force) { + int fd = -1, notify = -1, r, wd; + + assert(name); + + /* We use inotify to be notified when the tty is closed. We + * create the watch before checking if we can actually acquire + * it, so that we don't lose any event. + * + * Note: strictly speaking this actually watches for the + * device being closed, it does *not* really watch whether a + * tty loses its controlling process. However, unless some + * rogue process uses TIOCNOTTY on /dev/tty *after* closing + * its tty otherwise this will not become a problem. As long + * as the administrator makes sure not configure any service + * on the same tty as an untrusted user this should not be a + * problem. (Which he probably should not do anyway.) */ + + if (!fail && !force) { + if ((notify = inotify_init1(IN_CLOEXEC)) < 0) { + r = -errno; + goto fail; + } + + if ((wd = inotify_add_watch(notify, name, IN_CLOSE)) < 0) { + r = -errno; + goto fail; + } + } + + for (;;) { + if ((r = flush_fd(notify)) < 0) + goto fail; + + /* We pass here O_NOCTTY only so that we can check the return + * value TIOCSCTTY and have a reliable way to figure out if we + * successfully became the controlling process of the tty */ + if ((fd = open_terminal(name, O_RDWR|O_NOCTTY)) < 0) + return -errno; + + /* First, try to get the tty */ + if ((r = ioctl(fd, TIOCSCTTY, force)) < 0 && + (force || fail || errno != EPERM)) { + r = -errno; + goto fail; + } + + if (r >= 0) + break; + + assert(!fail); + assert(!force); + assert(notify >= 0); + + for (;;) { + struct inotify_event e; + ssize_t l; + + if ((l = read(notify, &e, sizeof(e))) != sizeof(e)) { + + if (l < 0) { + + if (errno == EINTR) + continue; + + r = -errno; + } else + r = -EIO; + + goto fail; + } + + if (e.wd != wd || !(e.mask & IN_CLOSE)) { + r = -errno; + goto fail; + } + + break; + } + + /* We close the tty fd here since if the old session + * ended our handle will be dead. It's important that + * we do this after sleeping, so that we don't enter + * an endless loop. */ + close_nointr_nofail(fd); + } + + if (notify >= 0) + close_nointr(notify); + + if ((r = reset_terminal(fd)) < 0) + log_warning("Failed to reset terminal: %s", strerror(-r)); + + return fd; + +fail: + if (fd >= 0) + close_nointr(fd); + + if (notify >= 0) + close_nointr(notify); + + return r; +} + +int release_terminal(void) { + int r = 0, fd; + + if ((fd = open("/dev/tty", O_RDWR)) < 0) + return -errno; + + if (ioctl(fd, TIOCNOTTY) < 0) + r = -errno; + + close_nointr_nofail(fd); + return r; +} + static const char *const ioprio_class_table[] = { [IOPRIO_CLASS_NONE] = "none", [IOPRIO_CLASS_RT] = "realtime", |