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# Copyright 2016 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Implements raw HID interface on Linux using SysFS and device files."""
from __future__ import division
import os
import struct
from pyu2f import errors
from pyu2f.hid import base
REPORT_DESCRIPTOR_KEY_MASK = 0xfc
LONG_ITEM_ENCODING = 0xfe
OUTPUT_ITEM = 0x90
INPUT_ITEM = 0x80
COLLECTION_ITEM = 0xa0
REPORT_COUNT = 0x94
REPORT_SIZE = 0x74
USAGE_PAGE = 0x04
USAGE = 0x08
def GetValueLength(rd, pos):
"""Get value length for a key in rd.
For a key at position pos in the Report Descriptor rd, return the length
of the associated value. This supports both short and long format
values.
Args:
rd: Report Descriptor
pos: The position of the key in rd.
Returns:
(key_size, data_len) where key_size is the number of bytes occupied by
the key and data_len is the length of the value associated by the key.
"""
rd = bytearray(rd)
key = rd[pos]
if key == LONG_ITEM_ENCODING:
# If the key is tagged as a long item (0xfe), then the format is
# [key (1 byte)] [data len (1 byte)] [item tag (1 byte)] [data (n # bytes)].
# Thus, the entire key record is 3 bytes long.
if pos + 1 < len(rd):
return (3, rd[pos + 1])
else:
raise errors.HidError('Malformed report descriptor')
else:
# If the key is tagged as a short item, then the item tag and data len are
# packed into one byte. The format is thus:
# [tag (high 4 bits)] [type (2 bits)] [size code (2 bits)] [data (n bytes)].
# The size code specifies 1,2, or 4 bytes (0x03 means 4 bytes).
code = key & 0x03
if code <= 0x02:
return (1, code)
elif code == 0x03:
return (1, 4)
raise errors.HidError('Cannot happen')
def ReadLsbBytes(rd, offset, value_size):
"""Reads value_size bytes from rd at offset, least signifcant byte first."""
encoding = None
if value_size == 1:
encoding = '<B'
elif value_size == 2:
encoding = '<H'
elif value_size == 4:
encoding = '<L'
else:
raise errors.HidError('Invalid value size specified')
ret, = struct.unpack(encoding, rd[offset:offset + value_size])
return ret
class NoReportCountFound(Exception):
pass
def ParseReportDescriptor(rd, desc):
"""Parse the binary report descriptor.
Parse the binary report descriptor into a DeviceDescriptor object.
Args:
rd: The binary report descriptor
desc: The DeviceDescriptor object to update with the results
from parsing the descriptor.
Returns:
None
"""
rd = bytearray(rd)
pos = 0
report_count = None
report_size = None
usage_page = None
usage = None
while pos < len(rd):
key = rd[pos]
# First step, determine the value encoding (either long or short).
key_size, value_length = GetValueLength(rd, pos)
if key & REPORT_DESCRIPTOR_KEY_MASK == INPUT_ITEM:
if report_count and report_size:
byte_length = (report_count * report_size) // 8
desc.internal_max_in_report_len = max(
desc.internal_max_in_report_len, byte_length)
report_count = None
report_size = None
elif key & REPORT_DESCRIPTOR_KEY_MASK == OUTPUT_ITEM:
if report_count and report_size:
byte_length = (report_count * report_size) // 8
desc.internal_max_out_report_len = max(
desc.internal_max_out_report_len, byte_length)
report_count = None
report_size = None
elif key & REPORT_DESCRIPTOR_KEY_MASK == COLLECTION_ITEM:
if usage_page:
desc.usage_page = usage_page
if usage:
desc.usage = usage
elif key & REPORT_DESCRIPTOR_KEY_MASK == REPORT_COUNT:
if len(rd) >= pos + 1 + value_length:
report_count = ReadLsbBytes(rd, pos + 1, value_length)
elif key & REPORT_DESCRIPTOR_KEY_MASK == REPORT_SIZE:
if len(rd) >= pos + 1 + value_length:
report_size = ReadLsbBytes(rd, pos + 1, value_length)
elif key & REPORT_DESCRIPTOR_KEY_MASK == USAGE_PAGE:
if len(rd) >= pos + 1 + value_length:
usage_page = ReadLsbBytes(rd, pos + 1, value_length)
elif key & REPORT_DESCRIPTOR_KEY_MASK == USAGE:
if len(rd) >= pos + 1 + value_length:
usage = ReadLsbBytes(rd, pos + 1, value_length)
pos += value_length + key_size
return desc
def ParseUevent(uevent, desc):
lines = uevent.split(b'\n')
for line in lines:
line = line.strip()
if not line:
continue
k, v = line.split(b'=')
if k == b'HID_NAME':
desc.product_string = v.decode('utf8')
elif k == b'HID_ID':
_, vid, pid = v.split(b':')
desc.vendor_id = int(vid, 16)
desc.product_id = int(pid, 16)
class LinuxHidDevice(base.HidDevice):
"""Implementation of HID device for linux.
Implementation of HID device interface for linux that uses block
devices to interact with the device and sysfs to enumerate/discover
device metadata.
"""
@staticmethod
def Enumerate():
for hidraw in os.listdir('/sys/class/hidraw'):
rd_path = (
os.path.join(
'/sys/class/hidraw', hidraw,
'device/report_descriptor'))
uevent_path = os.path.join('/sys/class/hidraw', hidraw, 'device/uevent')
rd_file = open(rd_path, 'rb')
uevent_file = open(uevent_path, 'rb')
desc = base.DeviceDescriptor()
desc.path = os.path.join('/dev/', hidraw)
ParseReportDescriptor(rd_file.read(), desc)
ParseUevent(uevent_file.read(), desc)
rd_file.close()
uevent_file.close()
yield desc.ToPublicDict()
def __init__(self, path):
base.HidDevice.__init__(self, path)
self.dev = os.open(path, os.O_RDWR)
self.desc = base.DeviceDescriptor()
self.desc.path = path
rd_file = open(os.path.join('/sys/class/hidraw',
os.path.basename(path),
'device/report_descriptor'), 'rb')
ParseReportDescriptor(rd_file.read(), self.desc)
rd_file.close()
def GetInReportDataLength(self):
"""See base class."""
return self.desc.internal_max_in_report_len
def GetOutReportDataLength(self):
"""See base class."""
return self.desc.internal_max_out_report_len
def Write(self, packet):
"""See base class."""
out = bytearray([0] + packet) # Prepend the zero-byte (report ID)
os.write(self.dev, out)
def Read(self):
"""See base class."""
raw_in = os.read(self.dev, self.GetInReportDataLength())
decoded_in = list(bytearray(raw_in))
return decoded_in
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