IOU tools
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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# To use python v2.7 change the first line to:
#!/usr/bin/env python
# Copyright (C) 2015 Bernhard Ehlers
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
# This utility is a stripped down version of dynamips' nvram_export,
# ported from C to Python, see https://github.com/GNS3/dynamips
# nvram_export is (c) 2013 Flávio J. Saraiva
"""
iou_export exports startup/private configuration from IOU NVRAM file.
usage: iou_export [-h] NVRAM startup-config [private-config]
positional arguments:
NVRAM NVRAM file
startup-config startup configuration
private-config private configuration
optional arguments:
-h, --help show this help message and exit
"""
import struct
# Uncompress data in LZC format, .Z file format
# LZC uses the LZW compression algorithm with a variable dictionary size
# For LZW see https://en.wikipedia.org/wiki/Lempel–Ziv–Welch
# Performance: about 1 MByte/sec, 15-50 times slower than C implementation
def uncompress_LZC(data):
LZC_NUM_BITS_MIN = 9
LZC_NUM_BITS_MAX = 16
in_data = bytearray(data)
in_len = len(in_data)
out_data = bytearray()
if in_len == 0:
return out_data
if in_len < 3:
raise ValueError('invalid length')
if in_data[0] != 0x1F or in_data[1] != 0x9D:
raise ValueError('invalid header')
max_bits = in_data[2] & 0x1F
if max_bits < LZC_NUM_BITS_MIN or max_bits > LZC_NUM_BITS_MAX:
raise ValueError('not supported')
num_items = 1 << max_bits
blockmode = (in_data[2] & 0x80) != 0
in_pos = 3
start_pos = in_pos
num_bits = LZC_NUM_BITS_MIN
dict_size = 1 << num_bits
head = 256
if blockmode:
head += 1
first_sym = True
# initialize dictionary
comp_dict = [None] * num_items
for i in range(0, 256):
comp_dict[i] = bytes(bytearray([i]))
buf = buf_bits = 0
while in_pos < in_len:
# get next symbol
try:
while buf_bits < num_bits:
buf |= in_data[in_pos] << buf_bits
buf_bits += 8
in_pos += 1
buf, symbol = divmod(buf, dict_size)
buf_bits -= num_bits
except IndexError:
raise ValueError('invalid data')
# re-initialize dictionary
if blockmode and symbol == 256:
# skip to next buffer boundary
buf = buf_bits = 0
in_pos += (start_pos - in_pos) % num_bits
# reset to LZC_NUM_BITS_MIN
head = 257
num_bits = LZC_NUM_BITS_MIN
dict_size = 1 << num_bits
start_pos = in_pos
first_sym = True
continue
# first symbol
if first_sym:
first_sym = False
if symbol >= 256:
raise ValueError('invalid data')
prev = symbol
out_data.extend(comp_dict[symbol])
continue
# dictionary full
if head >= num_items:
out_data.extend(comp_dict[symbol])
continue
# update compression dictionary
if symbol < head:
comp_dict[head] = comp_dict[prev] + comp_dict[symbol][0:1]
elif symbol == head:
comp_dict[head] = comp_dict[prev] + comp_dict[prev][0:1]
else:
raise ValueError('invalid data')
prev = symbol
# output symbol
out_data.extend(comp_dict[symbol])
# update head, check for num_bits change
head += 1
if head >= dict_size and num_bits < max_bits:
num_bits += 1
dict_size = 1 << num_bits
start_pos = in_pos
return out_data
# export IOU NVRAM
# NVRAM format: https://github.com/ehlers/IOUtools/blob/master/NVRAM.md
def nvram_export(nvram):
nvram = bytearray(nvram)
offset = 0
# extract startup config
try:
(magic, data_format, _, _, _, _, length, _, _, _, _, _) = \
struct.unpack_from('>HHHHIIIIIHHI', nvram, offset=offset)
offset += 36
if magic != 0xABCD:
raise ValueError('no startup config')
if len(nvram) < offset+length:
raise ValueError('invalid length')
startup = nvram[offset:offset+length]
except struct.error:
raise ValueError('invalid length')
# uncompress startup config
if data_format == 2:
try:
startup = uncompress_LZC(startup)
except ValueError as err:
raise ValueError('uncompress startup: ' + str(err))
private = None
try:
# calculate offset of private header
length += (4 - length % 4) % 4 # alignment to multiple of 4
offset += length
# check for additonal offset of 4
(magic, data_format) = struct.unpack_from('>HH', nvram, offset=offset+4)
if magic == 0xFEDC and data_format == 1:
offset += 4
# extract private config
(magic, data_format, _, _, length) = \
struct.unpack_from('>HHIII', nvram, offset=offset)
offset += 16
if magic == 0xFEDC and data_format == 1:
if len(nvram) < offset+length:
raise ValueError('invalid length')
private = nvram[offset:offset+length]
# missing private header is not an error
except struct.error:
pass
return (startup, private)
if __name__ == '__main__':
# Main program
import argparse
import sys
parser = argparse.ArgumentParser(description='%(prog)s exports startup/private configuration from IOU NVRAM file.')
parser.add_argument('nvram', metavar='NVRAM',
help='NVRAM file')
parser.add_argument('startup', metavar='startup-config',
help='startup configuration')
parser.add_argument('private', metavar='private-config', nargs='?',
help='private configuration')
args = parser.parse_args()
try:
fd = open(args.nvram, 'rb')
nvram = fd.read()
fd.close()
except (IOError, OSError) as err:
sys.stderr.write("Error reading file: {}\n".format(err))
sys.exit(1)
try:
startup, private = nvram_export(nvram)
except ValueError as err:
sys.stderr.write("nvram_export: {}\n".format(err))
sys.exit(3)
try:
fd = open(args.startup, 'wb')
fd.write(startup)
fd.close()
if args.private is not None:
if private is None:
sys.stderr.write("Warning: No private config\n")
else:
fd = open(args.private, 'wb')
fd.write(private)
fd.close()
except (IOError, OSError) as err:
sys.stderr.write("Error writing file: {}\n".format(err))
sys.exit(1)