hid_linux.c

/*
 * Copyright (c) 2019 Yubico AB. All rights reserved.
 * Use of this source code is governed by a BSD-style
 * license that can be found in the LICENSE file.
 */

#include <sys/types.h>

#include <sys/ioctl.h>
#include <linux/hidraw.h>
#include <linux/input.h>

#include <errno.h>
#include <fcntl.h>
#include <libudev.h>
#include <poll.h>
#include <string.h>
#include <unistd.h>

#include "fido.h"

struct hid_linux {
	int	fd;
	size_t	report_in_len;
	size_t	report_out_len;
};

static int
get_key_len(uint8_t tag, uint8_t *key, size_t *key_len)
{
	*key = tag & 0xfc;
	if ((*key & 0xf0) == 0xf0) {
		fido_log_debug("%s: *key=0x%02x", __func__, *key);
		return (-1);
	}

	*key_len = tag & 0x3;
	if (*key_len == 3) {
		*key_len = 4;
	}

	return (0);
}

static int
get_key_val(const void *body, size_t key_len, uint32_t *val)
{
	const uint8_t *ptr = body;

	switch (key_len) {
	case 0:
		*val = 0;
		break;
	case 1:
		*val = ptr[0];
		break;
	case 2:
		*val = (uint32_t)((ptr[1] << 8) | ptr[0]);
		break;
	default:
		fido_log_debug("%s: key_len=%zu", __func__, key_len);
		return (-1);
	}

	return (0);
}

static int
get_usage_info(const struct hidraw_report_descriptor *hrd, uint32_t *usage_page,
    uint32_t *usage)
{
	const uint8_t	*ptr = hrd->value;
	size_t		 len = hrd->size;

	while (len > 0) {
		const uint8_t tag = ptr[0];
		ptr++;
		len--;

		uint8_t  key;
		size_t   key_len;
		uint32_t key_val;

		if (get_key_len(tag, &key, &key_len) < 0 || key_len > len ||
		    get_key_val(ptr, key_len, &key_val) < 0) {
			return (-1);
		}

		if (key == 0x4) {
			*usage_page = key_val;
		} else if (key == 0x8) {
			*usage = key_val;
		}

		ptr += key_len;
		len -= key_len;
	}

	return (0);
}

static int
get_report_sizes(const struct hidraw_report_descriptor *hrd,
    size_t *report_in_len, size_t *report_out_len)
{
	const uint8_t	*ptr = hrd->value;
	size_t		 len = hrd->size;
	uint32_t	 report_size = 0;

	while (len > 0) {
		const uint8_t tag = ptr[0];
		ptr++;
		len--;

		uint8_t  key;
		size_t   key_len;
		uint32_t key_val;

		if (get_key_len(tag, &key, &key_len) < 0 || key_len > len ||
		    get_key_val(ptr, key_len, &key_val) < 0) {
			return (-1);
		}

		if (key == 0x94) {
			report_size = key_val;
		} else if (key == 0x80) {
			*report_in_len = (size_t)report_size;
		} else if (key == 0x90) {
			*report_out_len = (size_t)report_size;
		}

		ptr += key_len;
		len -= key_len;
	}

	return (0);
}

static int
get_report_descriptor(int fd, struct hidraw_report_descriptor *hrd)
{
	int s = -1;

	if (ioctl(fd, HIDIOCGRDESCSIZE, &s) < 0 || s < 0 ||
	    (unsigned)s > HID_MAX_DESCRIPTOR_SIZE) {
		fido_log_debug("%s: ioctl HIDIOCGRDESCSIZE", __func__);
		return (-1);
	}

	hrd->size = (unsigned)s;

	if (ioctl(fd, HIDIOCGRDESC, hrd) < 0) {
		fido_log_debug("%s: ioctl HIDIOCGRDESC", __func__);
		return (-1);
	}

	return (0);
}

static bool
is_fido(const char *path)
{
	int				fd;
	uint32_t			usage = 0;
	uint32_t			usage_page = 0;
	struct hidraw_report_descriptor	hrd;

	memset(&hrd, 0, sizeof(hrd));

	if ((fd = open(path, O_RDONLY)) == -1) {
		fido_log_debug("%s: open", __func__);
		return (false);
	}

	if (get_report_descriptor(fd, &hrd) < 0 ||
	    get_usage_info(&hrd, &usage_page, &usage) < 0) {
		close(fd);
		return (false);
	}

	close(fd);

	return (usage_page == 0xf1d0);
}

static int
parse_uevent(const char *uevent, int *bus, int16_t *vendor_id,
    int16_t *product_id)
{
	char			*cp;
	char			*p;
	char			*s;
	int			 ok = -1;
	short unsigned int	 x;
	short unsigned int	 y;
	short unsigned int	 z;

	if ((s = cp = strdup(uevent)) == NULL)
		return (-1);

	while ((p = strsep(&cp, "\n")) != NULL && *p != '\0') {
		if (strncmp(p, "HID_ID=", 7) == 0) {
			if (sscanf(p + 7, "%hx:%hx:%hx", &x, &y, &z) == 3) {
				*bus = (int)x;
				*vendor_id = (int16_t)y;
				*product_id = (int16_t)z;
				ok = 0;
				break;
			}
		}
	}

	free(s);

	return (ok);
}

static char *
get_parent_attr(struct udev_device *dev, const char *subsystem,
    const char *devtype, const char *attr)
{
	struct udev_device	*parent;
	const char		*value;

	if ((parent = udev_device_get_parent_with_subsystem_devtype(dev,
	    subsystem, devtype)) == NULL || (value =
	    udev_device_get_sysattr_value(parent, attr)) == NULL)
		return (NULL);

	return (strdup(value));
}

static char *
get_usb_attr(struct udev_device *dev, const char *attr)
{
	return (get_parent_attr(dev, "usb", "usb_device", attr));
}

static int
copy_info(fido_dev_info_t *di, struct udev *udev,
    struct udev_list_entry *udev_entry)
{
	const char		*name;
	const char		*path;
	char			*uevent = NULL;
	struct udev_device	*dev = NULL;
	int			 bus = 0;
	int			 ok = -1;

	memset(di, 0, sizeof(*di));

	if ((name = udev_list_entry_get_name(udev_entry)) == NULL ||
	    (dev = udev_device_new_from_syspath(udev, name)) == NULL ||
	    (path = udev_device_get_devnode(dev)) == NULL ||
	    is_fido(path) == 0)
		goto fail;

	if ((uevent = get_parent_attr(dev, "hid", NULL, "uevent")) == NULL ||
	    parse_uevent(uevent, &bus, &di->vendor_id, &di->product_id) < 0) {
		fido_log_debug("%s: uevent", __func__);
		goto fail;
	}

#ifndef FIDO_HID_ANY
	if (bus != BUS_USB) {
		fido_log_debug("%s: bus", __func__);
		goto fail;
	}
#endif

	di->path = strdup(path);
	di->manufacturer = get_usb_attr(dev, "manufacturer");
	di->product = get_usb_attr(dev, "product");

	if (di->path == NULL || di->manufacturer == NULL || di->product == NULL)
		goto fail;

	ok = 0;
fail:
	if (dev != NULL)
		udev_device_unref(dev);

	free(uevent);

	if (ok < 0) {
		free(di->path);
		free(di->manufacturer);
		free(di->product);
		explicit_bzero(di, sizeof(*di));
	}

	return (ok);
}

int
fido_hid_manifest(fido_dev_info_t *devlist, size_t ilen, size_t *olen)
{
	struct udev		*udev = NULL;
	struct udev_enumerate	*udev_enum = NULL;
	struct udev_list_entry	*udev_list;
	struct udev_list_entry	*udev_entry;
	int			 r = FIDO_ERR_INTERNAL;

	*olen = 0;

	if (ilen == 0)
		return (FIDO_OK); /* nothing to do */

	if (devlist == NULL)
		return (FIDO_ERR_INVALID_ARGUMENT);

	if ((udev = udev_new()) == NULL ||
	    (udev_enum = udev_enumerate_new(udev)) == NULL)
		goto fail;

	if (udev_enumerate_add_match_subsystem(udev_enum, "hidraw") < 0 ||
	    udev_enumerate_scan_devices(udev_enum) < 0)
		goto fail;

	if ((udev_list = udev_enumerate_get_list_entry(udev_enum)) == NULL) {
		r = FIDO_OK; /* zero hidraw devices */
		goto fail;
	}

	udev_list_entry_foreach(udev_entry, udev_list) {
		if (copy_info(&devlist[*olen], udev, udev_entry) == 0) {
			devlist[*olen].io = (fido_dev_io_t) {
				fido_hid_open,
				fido_hid_close,
				fido_hid_read,
				fido_hid_write,
			};
			if (++(*olen) == ilen)
				break;
		}
	}

	r = FIDO_OK;
fail:
	if (udev_enum != NULL)
		udev_enumerate_unref(udev_enum);
	if (udev != NULL)
		udev_unref(udev);

	return (r);
}

void *
fido_hid_open(const char *path)
{
	struct hid_linux		*ctx;
	struct hidraw_report_descriptor	 hrd;

	if ((ctx = calloc(1, sizeof(*ctx))) == NULL)
		return (NULL);

	if ((ctx->fd = open(path, O_RDWR)) < 0) {
		free(ctx);
		return (NULL);
	}

	if (get_report_descriptor(ctx->fd, &hrd) < 0 || get_report_sizes(&hrd,
	    &ctx->report_in_len, &ctx->report_out_len) < 0 ||
	    ctx->report_in_len == 0 || ctx->report_out_len == 0) {
		fido_log_debug("%s: using default report sizes", __func__);
		ctx->report_in_len = CTAP_MAX_REPORT_LEN;
		ctx->report_out_len = CTAP_MAX_REPORT_LEN;
	}

	return (ctx);
}

void
fido_hid_close(void *handle)
{
	struct hid_linux *ctx = handle;

	close(ctx->fd);
	free(ctx);
}

static int
timespec_to_ms(const struct timespec *ts, int upper_bound)
{
	int64_t x;
	int64_t y;

	if (ts->tv_sec < 0 || ts->tv_sec > INT64_MAX / 1000LL ||
	    ts->tv_nsec < 0 || ts->tv_nsec / 1000000LL > INT64_MAX)
		return (upper_bound);

	x = ts->tv_sec * 1000LL;
	y = ts->tv_nsec / 1000000LL;

	if (INT64_MAX - x < y || x + y > upper_bound)
		return (upper_bound);

	return (int)(x + y);
}

static int
waitfd(int fd, int ms)
{
	struct timespec	ts_start;
	struct timespec	ts_now;
	struct timespec	ts_delta;
	struct pollfd	pfd;
	int		ms_remain;
	int		r;

	if (ms < 0)
		return (0);

	memset(&pfd, 0, sizeof(pfd));
	pfd.events = POLLIN;
	pfd.fd = fd;

	if (clock_gettime(CLOCK_MONOTONIC, &ts_start) != 0) {
		fido_log_debug("%s: clock_gettime: %s", __func__,
		    strerror(errno));
		return (-1);
	}

	for (ms_remain = ms; ms_remain > 0;) {
		if ((r = poll(&pfd, 1, ms_remain)) > 0)
			return (0);
		else if (r == 0)
			break;
		else if (errno != EINTR) {
			fido_log_debug("%s: poll: %s", __func__,
			    strerror(errno));
			return (-1);
		}
		/* poll interrupted - subtract time already waited */
		if (clock_gettime(CLOCK_MONOTONIC, &ts_now) != 0) {
			fido_log_debug("%s: clock_gettime: %s", __func__,
			    strerror(errno));
			return (-1);
		}
		timespecsub(&ts_now, &ts_start, &ts_delta);
		ms_remain = ms - timespec_to_ms(&ts_delta, ms);
	}

	return (-1);
}

int
fido_hid_read(void *handle, unsigned char *buf, size_t len, int ms)
{
	struct hid_linux	*ctx = handle;
	ssize_t			 r;

	if (len != ctx->report_in_len) {
		fido_log_debug("%s: len %zu", __func__, len);
		return (-1);
	}

	if (waitfd(ctx->fd, ms) < 0) {
		fido_log_debug("%s: fd not ready", __func__);
		return (-1);
	}

	if ((r = read(ctx->fd, buf, len)) < 0 || (size_t)r != len) {
		fido_log_debug("%s: read", __func__);
		return (-1);
	}

	return ((int)r);
}

int
fido_hid_write(void *handle, const unsigned char *buf, size_t len)
{
	struct hid_linux	*ctx = handle;
	ssize_t			 r;

	if (len != ctx->report_out_len + 1) {
		fido_log_debug("%s: len %zu", __func__, len);
		return (-1);
	}

	if ((r = write(ctx->fd, buf, len)) < 0 || (size_t)r != len) {
		fido_log_debug("%s: write", __func__);
		return (-1);
	}

	return ((int)r);
}

size_t
fido_hid_report_in_len(void *handle)
{
	struct hid_linux *ctx = handle;

	return (ctx->report_in_len);
}

size_t
fido_hid_report_out_len(void *handle)
{
	struct hid_linux *ctx = handle;

	return (ctx->report_out_len);
}