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Add API to control audio device parameters exposed by sndiod.

The API exposes controls of modern audio hardware and sndiod software
volume knobs in a uniform way.  Hardware knobs are exposed through
sndiod.  Multiple programs may use the controls at the same time
without the need to continuously scan the controls.

For now sndiod exposes only its own controls and the master output and
input volumes of the underlying hardware (if any), i.e. those
typically exposed by acpi volume keys.

ok deraadt

/*	$OpenBSD: sndiod.c,v 1.38 2020/02/26 13:53:58 ratchov Exp $	*/
/*
 * Copyright (c) 2008-2012 Alexandre Ratchov <alex@caoua.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/resource.h>
#include <sys/socket.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <limits.h>
#include <pwd.h>
#include <signal.h>
#include <sndio.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "amsg.h"
#include "defs.h"
#include "dev.h"
#include "fdpass.h"
#include "file.h"
#include "listen.h"
#include "midi.h"
#include "opt.h"
#include "sock.h"
#include "utils.h"

/*
 * unprivileged user name
 */
#ifndef SNDIO_USER
#define SNDIO_USER	"_sndio"
#endif

/*
 * privileged user name
 */
#ifndef SNDIO_PRIV_USER
#define SNDIO_PRIV_USER	"_sndiop"
#endif

/*
 * priority when run as root
 */
#ifndef SNDIO_PRIO
#define SNDIO_PRIO	(-20)
#endif

/*
 * sample rate if no ``-r'' is used
 */
#ifndef DEFAULT_RATE
#define DEFAULT_RATE	48000
#endif

/*
 * block size if neither ``-z'' nor ``-b'' is used
 */
#ifndef DEFAULT_ROUND
#define DEFAULT_ROUND	480
#endif

/*
 * buffer size if neither ``-z'' nor ``-b'' is used
 */
#ifndef DEFAULT_BUFSZ
#define DEFAULT_BUFSZ	7680
#endif

/*
 * default device in server mode
 */
#ifndef DEFAULT_DEV
#define DEFAULT_DEV "rsnd/0"
#endif

void sigint(int);
void sighup(int);
void opt_ch(int *, int *);
void opt_enc(struct aparams *);
int opt_mmc(void);
int opt_onoff(void);
int getword(char *, char **);
unsigned int opt_mode(void);
void getbasepath(char *);
void setsig(void);
void unsetsig(void);
struct dev *mkdev(char *, struct aparams *,
    int, int, int, int, int, int);
struct port *mkport(char *, int);
struct opt *mkopt(char *, struct dev *,
    int, int, int, int, int, int, int, int);

unsigned int log_level = 0;
volatile sig_atomic_t quit_flag = 0, reopen_flag = 0;

char usagestr[] = "usage: sndiod [-d] [-a flag] [-b nframes] "
    "[-C min:max] [-c min:max]\n\t"
    "[-e enc] [-F device] [-f device] [-j flag] [-L addr] [-m mode]\n\t"
    "[-Q port] [-q port] [-r rate] [-s name] [-t mode] [-U unit]\n\t"
    "[-v volume] [-w flag] [-z nframes]\n";

/*
 * SIGINT handler, it raises the quit flag. If the flag is already set,
 * that means that the last SIGINT was not handled, because the process
 * is blocked somewhere, so exit.
 */
void
sigint(int s)
{
	if (quit_flag)
		_exit(1);
	quit_flag = 1;
}

/*
 * SIGHUP handler, it raises the reopen flag, which requests devices
 * to be reopened.
 */
void
sighup(int s)
{
	reopen_flag = 1;
}

void
opt_ch(int *rcmin, int *rcmax)
{
	char *next, *end;
	long cmin, cmax;

	errno = 0;
	cmin = strtol(optarg, &next, 10);
	if (next == optarg || *next != ':')
		goto failed;
	cmax = strtol(++next, &end, 10);
	if (end == next || *end != '\0')
		goto failed;
	if (cmin < 0 || cmax < cmin || cmax >= NCHAN_MAX)
		goto failed;
	*rcmin = cmin;
	*rcmax = cmax;
	return;
failed:
	errx(1, "%s: bad channel range", optarg);
}

void
opt_enc(struct aparams *par)
{
	int len;

	len = aparams_strtoenc(par, optarg);
	if (len == 0 || optarg[len] != '\0')
		errx(1, "%s: bad encoding", optarg);
}

int
opt_mmc(void)
{
	if (strcmp("off", optarg) == 0)
		return 0;
	if (strcmp("slave", optarg) == 0)
		return 1;
	errx(1, "%s: off/slave expected", optarg);
}

int
opt_onoff(void)
{
	if (strcmp("off", optarg) == 0)
		return 0;
	if (strcmp("on", optarg) == 0)
		return 1;
	errx(1, "%s: on/off expected", optarg);
}

int
getword(char *word, char **str)
{
	char *p = *str;

	for (;;) {
		if (*word == '\0')
			break;
		if (*word++ != *p++)
			return 0;
	}
	if (*p == ',' || *p == '\0') {
		*str = p;
		return 1;
	}
	return 0;
}

unsigned int
opt_mode(void)
{
	unsigned int mode = 0;
	char *p = optarg;

	for (;;) {
		if (getword("play", &p)) {
			mode |= MODE_PLAY;
		} else if (getword("rec", &p)) {
			mode |= MODE_REC;
		} else if (getword("mon", &p)) {
			mode |= MODE_MON;
		} else if (getword("midi", &p)) {
			mode |= MODE_MIDIMASK;
		} else
			errx(1, "%s: bad mode", optarg);
		if (*p == '\0')
			break;
		p++;
	}
	if (mode == 0)
		errx(1, "empty mode");
	return mode;
}

void
setsig(void)
{
	struct sigaction sa;

	quit_flag = 0;
	reopen_flag = 0;
	sigfillset(&sa.sa_mask);
	sa.sa_flags = SA_RESTART;
	sa.sa_handler = sigint;
	if (sigaction(SIGINT, &sa, NULL) == -1)
		err(1, "sigaction(int) failed");
	if (sigaction(SIGTERM, &sa, NULL) == -1)
		err(1, "sigaction(term) failed");
	sa.sa_handler = sighup;
	if (sigaction(SIGHUP, &sa, NULL) == -1)
		err(1, "sigaction(hup) failed");
}

void
unsetsig(void)
{
	struct sigaction sa;

	sigfillset(&sa.sa_mask);
	sa.sa_flags = SA_RESTART;
	sa.sa_handler = SIG_DFL;
	if (sigaction(SIGHUP, &sa, NULL) == -1)
		err(1, "unsetsig(hup): sigaction failed");
	if (sigaction(SIGTERM, &sa, NULL) == -1)
		err(1, "unsetsig(term): sigaction failed");
	if (sigaction(SIGINT, &sa, NULL) == -1)
		err(1, "unsetsig(int): sigaction failed");
}

void
getbasepath(char *base)
{
	uid_t uid;
	struct stat sb;
	mode_t mask, omask;

	uid = geteuid();
	if (uid == 0) {
		mask = 022;
		snprintf(base, SOCKPATH_MAX, SOCKPATH_DIR);
	} else {
		mask = 077;
		snprintf(base, SOCKPATH_MAX, SOCKPATH_DIR "-%u", uid);
	}
	omask = umask(mask);
	if (mkdir(base, 0777) == -1) {
		if (errno != EEXIST)
			err(1, "mkdir(\"%s\")", base);
	}
	umask(omask);
	if (stat(base, &sb) == -1)
		err(1, "stat(\"%s\")", base);
	if (!S_ISDIR(sb.st_mode))
		errx(1, "%s is not a directory", base);
	if (sb.st_uid != uid || (sb.st_mode & mask) != 0)
		errx(1, "%s has wrong permissions", base);
}

struct dev *
mkdev(char *path, struct aparams *par,
    int mode, int bufsz, int round, int rate, int hold, int autovol)
{
	struct dev *d;

	for (d = dev_list; d != NULL; d = d->next) {
		if (d->path_list->next == NULL &&
		    strcmp(d->path_list->str, path) == 0)
			return d;
	}
	if (!bufsz && !round) {
		round = DEFAULT_ROUND;
		bufsz = DEFAULT_BUFSZ;
	} else if (!bufsz) {
		bufsz = round * 2;
	} else if (!round)
		round = bufsz / 2;
	d = dev_new(path, par, mode, bufsz, round, rate, hold, autovol);
	if (d == NULL)
		exit(1);
	return d;
}

struct port *
mkport(char *path, int hold)
{
	struct port *c;

	for (c = port_list; c != NULL; c = c->next) {
		if (c->path_list->next == NULL &&
		    strcmp(c->path_list->str, path) == 0)
			return c;
	}
	c = port_new(path, MODE_MIDIMASK, hold);
	if (c == NULL)
		exit(1);
	return c;
}

struct opt *
mkopt(char *path, struct dev *d,
    int pmin, int pmax, int rmin, int rmax,
    int mode, int vol, int mmc, int dup)
{
	struct opt *o;

	o = opt_new(d, path, pmin, pmax, rmin, rmax,
	    MIDI_TO_ADATA(vol), mmc, dup, mode);
	if (o == NULL)
		return NULL;
	dev_adjpar(d, o->mode, o->pmax, o->rmax);
	return o;
}

static void
dounveil(char *name, char *prefix, char *path_prefix)
{
	size_t prefix_len;
	char path[PATH_MAX];

	prefix_len = strlen(prefix);

	if (strncmp(name, prefix, prefix_len) != 0)
		errx(1, "%s: unsupported device or port format", name);
	snprintf(path, sizeof(path), "%s%s", path_prefix, name + prefix_len);
	if (unveil(path, "rw") == -1)
		err(1, "unveil");
}

static int
start_helper(int background)
{
	struct dev *d;
	struct port *p;
	struct passwd *pw;
	struct name *n;
	int s[2];
	pid_t pid;

	if (geteuid() == 0) {
		if ((pw = getpwnam(SNDIO_PRIV_USER)) == NULL)
			errx(1, "unknown user %s", SNDIO_PRIV_USER);
	} else
		pw = NULL;
	if (socketpair(AF_UNIX, SOCK_STREAM, 0, s) == -1) {
		perror("socketpair");
		return 0;
	}
	pid = fork();
	if (pid	== -1) {
		log_puts("can't fork\n");
		return 0;
	}
	if (pid == 0) {
		setproctitle("helper");
		close(s[0]);
		if (fdpass_new(s[1], &helper_fileops) == NULL)
			return 0;
		if (background) {
			log_flush();
			log_level = 0;
			if (daemon(0, 0) == -1)
				err(1, "daemon");
		}
		if (pw != NULL) {
			if (setgroups(1, &pw->pw_gid) ||
			    setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) ||
			    setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid))
				err(1, "cannot drop privileges");
		}
		for (d = dev_list; d != NULL; d = d->next) {
			for (n = d->path_list; n != NULL; n = n->next) {
				dounveil(n->str, "rsnd/", "/dev/audio");
				dounveil(n->str, "rsnd/", "/dev/audioctl");
			}
		}
		for (p = port_list; p != NULL; p = p->next) {
			for (n = p->path_list; n != NULL; n = n->next)
				dounveil(n->str, "rmidi/", "/dev/rmidi");
		}
		if (pledge("stdio sendfd rpath wpath", NULL) == -1)
			err(1, "pledge");
		while (file_poll())
			; /* nothing */
		exit(0);
	} else {
		close(s[1]);
		if (fdpass_new(s[0], &worker_fileops) == NULL)
			return 0;
	}
	return 1;
}

static void
stop_helper(void)
{
	if (fdpass_peer)
		fdpass_close(fdpass_peer);
}

int
main(int argc, char **argv)
{
	int c, background, unit;
	int pmin, pmax, rmin, rmax;
	char base[SOCKPATH_MAX], path[SOCKPATH_MAX];
	unsigned int mode, dup, mmc, vol;
	unsigned int hold, autovol, bufsz, round, rate;
	const char *str;
	struct aparams par;
	struct dev *d;
	struct port *p;
	struct listen *l;
	struct passwd *pw;
	struct tcpaddr {
		char *host;
		struct tcpaddr *next;
	} *tcpaddr_list, *ta;

	atexit(log_flush);

	/*
	 * global options defaults
	 */
	vol = 118;
	dup = 1;
	mmc = 0;
	hold = 0;
	autovol = 1;
	bufsz = 0;
	round = 0;
	rate = DEFAULT_RATE;
	unit = 0;
	background = 1;
	pmin = 0;
	pmax = 1;
	rmin = 0;
	rmax = 1;
	aparams_init(&par);
	mode = MODE_PLAY | MODE_REC;
	tcpaddr_list = NULL;

	while ((c = getopt(argc, argv,
	    "a:b:c:C:de:F:f:j:L:m:Q:q:r:s:t:U:v:w:x:z:")) != -1) {
		switch (c) {
		case 'd':
			log_level++;
			background = 0;
			break;
		case 'U':
			unit = strtonum(optarg, 0, 15, &str);
			if (str)
				errx(1, "%s: unit number is %s", optarg, str);
			break;
		case 'L':
			ta = xmalloc(sizeof(struct tcpaddr));
			ta->host = optarg;
			ta->next = tcpaddr_list;
			tcpaddr_list = ta;
			break;
		case 'm':
			mode = opt_mode();
			break;
		case 'j':
			dup = opt_onoff();
			break;
		case 't':
			mmc = opt_mmc();
			break;
		case 'c':
			opt_ch(&pmin, &pmax);
			break;
		case 'C':
			opt_ch(&rmin, &rmax);
			break;
		case 'e':
			opt_enc(&par);
			break;
		case 'r':
			rate = strtonum(optarg, RATE_MIN, RATE_MAX, &str);
			if (str)
				errx(1, "%s: rate is %s", optarg, str);
			break;
		case 'v':
			vol = strtonum(optarg, 0, MIDI_MAXCTL, &str);
			if (str)
				errx(1, "%s: volume is %s", optarg, str);
			break;
		case 's':
			if ((d = dev_list) == NULL) {
				d = mkdev(DEFAULT_DEV, &par, 0, bufsz, round,
				    rate, hold, autovol);
			}
			if (mkopt(optarg, d, pmin, pmax, rmin, rmax,
				mode, vol, mmc, dup) == NULL)
				return 1;
			break;
		case 'q':
			mkport(optarg, hold);
			break;
		case 'Q':
			if (port_list == NULL)
				errx(1, "-Q %s: no ports defined", optarg);
			namelist_add(&port_list->path_list, optarg);
			break;
		case 'a':
			hold = opt_onoff();
			break;
		case 'w':
			autovol = opt_onoff();
			break;
		case 'b':
			bufsz = strtonum(optarg, 1, RATE_MAX, &str);
			if (str)
				errx(1, "%s: buffer size is %s", optarg, str);
			break;
		case 'z':
			round = strtonum(optarg, 1, SHRT_MAX, &str);
			if (str)
				errx(1, "%s: block size is %s", optarg, str);
			break;
		case 'f':
			mkdev(optarg, &par, 0, bufsz, round,
			    rate, hold, autovol);
			break;
		case 'F':
			if (dev_list == NULL)
				errx(1, "-F %s: no devices defined", optarg);
			namelist_add(&dev_list->path_list, optarg);
			break;
		default:
			fputs(usagestr, stderr);
			return 1;
		}
	}
	argc -= optind;
	argv += optind;
	if (argc > 0) {
		fputs(usagestr, stderr);
		return 1;
	}
	if (dev_list == NULL)
		mkdev(DEFAULT_DEV, &par, 0, bufsz, round, rate, hold, autovol);
	for (d = dev_list; d != NULL; d = d->next) {
		if (opt_byname(d, "default"))
			continue;
		if (mkopt("default", d, pmin, pmax, rmin, rmax,
			mode, vol, mmc, dup) == NULL)
			return 1;
	}

	setsig();
	filelist_init();

	if (!start_helper(background))
		return 1;

	if (geteuid() == 0) {
		if ((pw = getpwnam(SNDIO_USER)) == NULL)
			errx(1, "unknown user %s", SNDIO_USER);
	} else
		pw = NULL;
	getbasepath(base);
	snprintf(path, SOCKPATH_MAX, "%s/" SOCKPATH_FILE "%u", base, unit);
	if (!listen_new_un(path))
		return 1;
	for (ta = tcpaddr_list; ta != NULL; ta = ta->next) {
		if (!listen_new_tcp(ta->host, AUCAT_PORT + unit))
			return 1;
	}
	for (l = listen_list; l != NULL; l = l->next) {
		if (!listen_init(l))
			return 1;
	}
	midi_init();
	for (p = port_list; p != NULL; p = p->next) {
		if (!port_init(p))
			return 1;
	}
	for (d = dev_list; d != NULL; d = d->next) {
		if (!dev_init(d))
			return 1;
	}
	if (background) {
		log_flush();
		log_level = 0;
		if (daemon(0, 0) == -1)
			err(1, "daemon");
	}
	if (pw != NULL) {
		if (setpriority(PRIO_PROCESS, 0, SNDIO_PRIO) == -1)
			err(1, "setpriority");
		if (chroot(pw->pw_dir) == -1 || chdir("/") == -1)
			err(1, "cannot chroot to %s", pw->pw_dir);
		if (setgroups(1, &pw->pw_gid) == -1 ||
		    setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1 ||
		    setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1 )
			err(1, "cannot drop privileges");
	}
	if (tcpaddr_list) {
		if (pledge("stdio audio recvfd unix inet", NULL) == -1)
			err(1, "pledge");
	} else {
		if (pledge("stdio audio recvfd unix", NULL) == -1)
			err(1, "pledge");
	}
	for (;;) {
		if (quit_flag)
			break;
		if (reopen_flag) {
			reopen_flag = 0;
			for (d = dev_list; d != NULL; d = d->next)
				dev_reopen(d);
			for (p = port_list; p != NULL; p = p->next)
				port_reopen(p);
		}
		if (!fdpass_peer)
			break;
		if (!file_poll())
			break;
	}
	stop_helper();
	while (listen_list != NULL)
		listen_close(listen_list);
	while (sock_list != NULL)
		sock_close(sock_list);
	for (d = dev_list; d != NULL; d = d->next)
		dev_done(d);
	for (p = port_list; p != NULL; p = p->next)
		port_done(p);
	while (file_poll())
		; /* nothing */
	midi_done();

	while (dev_list)
		dev_del(dev_list);
	while (port_list)
		port_del(port_list);
	while (tcpaddr_list) {
		ta = tcpaddr_list;
		tcpaddr_list = ta->next;
		xfree(ta);
	}
	filelist_done();
	unsetsig();
	return 0;
}