Add a script to import meter information from a Kamstrup KEM file

utils/kem-import.py

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+# A Python script to decrypt the content of Kamstrup KEM file.
+#
+# The KEM file is a (sometimes zipped) xml file that contains xml-encrypted data using 
+# the xml-enc standard (http://www.w3.org/2001/04/xmlenc). The password needed to decrypt 
+# the xml-encrypted data can either be the CustomerId or something else selected by the 
+# person that created the KEM file using Kamstrup software.
+#
+# This script takes the encrypted KEM file and decrypts its content. The result is also 
+# a XML file with a list of meters. The script prints the information about each meter to
+# the console and populates wmbusmeters' config folder with corresponding meter files. 
+# Optionally, decrypted KEM file content can be saved to a file (option -o).
+#
+# Usage: python kem-decryptor.py [options] <kem_file> <password>
+# kem_file ... the name of the KEM file to decrypt (you need to unzip the the KEM file first, if it is zipped)
+# password ... original password used to encrypt the content (16 characters maximum)
+# options  ... use -h switch to get a list of options with their descriptions
+#
+# The script is Python2/Python3 compatible.
+#
+
+from __future__ import print_function
+import os
+import sys
+import errno
+import argparse
+import base64
+import Crypto.Cipher.AES as AES
+from xml.dom import minidom
+
+help_prog = "Decrypts Kamstrup KEM file and imports meter information into wmbusmeters' config folder."
+help_epilog = ""
+help_kem = "The name of the KEM file to decrypt (you need to unzip the the KEM file first, if it is zipped)."
+help_pwd = "The original password used to encrypt the KEM file content (16 characters maximum)."
+help_cfg = """Location of config files for wmbusmeters (default location is the current working directory). This option has the same meaning as --useconfig option of the wmbusmeters daemon, i.e. --useconfig=/ will populate /etc/wmbusmeters.d folder (must be run with sudo) and --useconfig=. (the default) populates ./etc/wmbusmeters.d folder. If the destination folder does not exist, it will be created; existing meter files will be overwritten."""
+help_dry = "No meter files will be created, only the info will be printed on the console."
+help_out = "Save the decrypted KEM file content into a given file."
+
+argparser = argparse.ArgumentParser(description=help_prog, epilog=help_epilog)
+argparser.add_argument('kem_file', help=help_kem)
+argparser.add_argument('password', help=help_pwd)
+argparser.add_argument("-c", "--useconfig", type=str, action='store', dest='config', default=os.getcwd(), help=help_cfg)
+argparser.add_argument("-n", "--dryrun", action='store_true', dest='dryrun', help=help_dry)
+argparser.add_argument("-o", "--output", type=str, action='store', dest='output', help=help_out)
+
+args = argparser.parse_args()
+
+# adjust the config folder location to full target path
+args.config = args.config.strip(os.path.sep) + '/etc/wmbusmeters.d/'
+
+
+# read and parse KEM file and extract its encrypted content
+# (KEM file is a a XML file formated according to http://www.w3.org/2001/04/xmlenc)
+xmldoc = minidom.parse(args.kem_file)
+encrypedtext = xmldoc.getElementsByTagName('CipherValue')[0].firstChild.nodeValue
+encrypeddata = base64.b64decode(encrypedtext)
+
+# KEM file data is encrypted with AES-128-CBC cipher and decryption
+# requires a 128bit key and 128bit initialization vector. In the case of KEM file, 
+# the initialization vector is the same as the key. If password length is less 
+# than 16 characters (128 bits), we pad the key with zeros up to its full length.
+key = bytes(str(args.password).encode("utf-8"))
+if (len(key) < 16): key += (16-len(key)) * b"\0"
+
+# content decryption
+aes = AES.new(key, AES.MODE_CBC, IV=key)
+decryptedtext = aes.decrypt(encrypeddata)
+
+# save decrypted XML file if requested
+if (args.output):
+    f = open(args.output, 'w')
+    f.write(decryptedtext)
+    f.close()
+#end if
+
+
+# create the folder for meter files if it does not exists
+if (not args.dryrun) and (not os.path.exists(args.config)):
+    print("Creating target folder:", args.config)
+    try:
+        os.makedirs(args.config)
+    except OSError as e:
+        if (e.errno in [errno.EPERM, errno.EACCES]): 
+            print(e)
+            print("You may need to use 'sudo' to access the target config folder.")
+            sys.exit(1)
+        else:
+            raise
+#end if
+
+
+# parse the decrypted KEM file content and create corresponding meter files in 
+# wmbusmeters' config folder for each meter found in the XML file
+xmldoc = minidom.parseString(decryptedtext)
+for e in xmldoc.getElementsByTagName('Meter'):
+    # read information from source XML file 
+    meterName   = e.getElementsByTagName('MeterName')[0].firstChild.nodeValue
+    meterType   = e.getElementsByTagName('ConsumptionType')[0].firstChild.nodeValue
+    meterNum    = e.getElementsByTagName('MeterNo')[0].firstChild.nodeValue
+    meterSerial = e.getElementsByTagName('SerialNo')[0].firstChild.nodeValue
+    meterVendor = e.getElementsByTagName('VendorId')[0].firstChild.nodeValue
+    meterConfig = e.getElementsByTagName('ConfigNo')[0].firstChild.nodeValue
+    meterModel  = e.getElementsByTagName('TypeNo')[0].firstChild.nodeValue
+    meterKey    = e.getElementsByTagName('DEK')[0].firstChild.nodeValue
+    
+    # meter model identification
+    # CONTRIBUTING NOTE: additional meter types supported by wmbusmeters can be put here 
+    # if their identification in KEM file is known
+    if (meterName == 'MC302') and (meterModel.startswith('302T')): 
+        wmbusmeters_driver = 'multical302'
+    elif (meterName == 'MC21') and (meterModel.startswith('021')): 
+        wmbusmeters_driver = 'multical21'
+    else:
+        wmbusmeters_driver = None
+    
+    # print info to console
+    print('Found meter', meterName, '('+meterModel+')')
+    print('    number :', meterNum)
+    print('    serial :', meterSerial)
+    print('    type   :', meterType)
+    print('    driver :', wmbusmeters_driver)
+    print('    config :', meterConfig)
+    print('    key    :', meterKey)
+    
+    if (not args.dryrun):
+        # save meter file in config folder if meter is supported by wmbusmeters
+        if (wmbusmeters_driver is not None):
+            try:
+                f = open(args.config+meterSerial, 'w')
+                f.write("name=%s\n" % (meterNum))
+                f.write("type=%s\n" % (wmbusmeters_driver))
+                f.write("id=%s\n" % (meterSerial))
+                f.write("key=%s\n" % (meterKey))
+                f.close()
+                print('    meter file:', args.config+meterSerial)
+            except (IOError, OSError) as e:
+                if (e.errno in [errno.EPERM, errno.EACCES]): 
+                    print(e)
+                    print("You may need to use 'sudo' to access the target config folder.")
+                    sys.exit(1)
+                else:
+                    print('XX',e)
+                    raise
+        else:
+            print('    !! unknow meter type, meter file has not been created')
+    #end if
+#end for
+
+