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from __future__ import absolute_import
from __future__ import print_function
import argparse
import sys
import nss.nss as nss
import nss.error as nss_error
print(sys.path)
import six
#-------------------------------------------------------------------------------
options = None
#-------------------------------------------------------------------------------
def fmt_info(label, item, level=0, hex_data=False):
fmt_tuples = nss.make_line_fmt_tuples(level, label+':')
if hex_data:
fmt_tuples.extend(nss.make_line_fmt_tuples(level+1,
nss.data_to_hex(item, 16)))
elif isinstance(item, six.string_types):
fmt_tuples.extend(nss.make_line_fmt_tuples(level+1, str(item)))
else:
fmt_tuples.extend(item.format_lines(level=level+1))
return nss.indented_format(fmt_tuples)
def generate_key():
# The AlgorithmID bundles up all the parameters used to
# generate a symmetric key
#
# Note, the defaults for create_pbev2_algorithm_id() are
# usually correct for most uses, thus one can call
# create_pbev2_algorithm_id() with no parameters.
# The parameters are only specified here because this is
# an example script people can play with.
alg_id = nss.create_pbev2_algorithm_id(options.pbe_alg,
options.cipher_alg,
options.prf_alg,
options.key_length,
options.iterations,
options.salt)
if not options.quiet:
print(fmt_info("create_pbev2_algorithm_id returned()", alg_id))
print()
# Pick a PK11 Slot to operate in, we'll use the internal slot
slot = nss.get_internal_slot()
# Generate the symmetric key
sym_key = slot.pbe_key_gen(alg_id, options.password)
if not options.quiet:
print(fmt_info("Using password", options.password))
print()
print(fmt_info("pbe_key_gen() returned sym_key", sym_key))
print()
return alg_id, sym_key
def get_encryption_context(alg_id, sym_key):
# In order for NSS to encrypt and decrypt data it needs an
# encryption context to perform the operation in. The cipher used
# for the encryption context is specified with a PK11 mechanism.
# The cipher likely also needs additional parameters (i.e. an
# Initialization Vector (IV) and possibly other values.
# The get_pbe_crypto_mechanism() call computes the mechanism
# and parameters for the PBE symmetric key we're using.
#
# Because the decryption context needs the same params used in
# the encryption context we save the param block returned by
# get_pbe_crypto_mechanism(). So that it can be passed to
# create_context_by_sym_key() when creating the decryption context.
# It's often the case the decryption is performed by a separate
# process so in this example we illustrate exchanging the param
# as base64 data.
mechanism, params = alg_id.get_pbe_crypto_mechanism(sym_key)
# Format the params binary data into a base64 string. The zero
# passed for the chars_per_line parameter indicates we want the
# base64 data as one single string as opposed to a list of wrapped
# strings.
params_base64 = params.to_base64(0)
if not options.quiet:
print(fmt_info("get_pbe_crypto_mechanism (encrypting) returned mechanism:",
nss.key_mechanism_type_name(mechanism)))
print(fmt_info("get_pbe_crypto_mechanism (encrypting) returned params:",
params))
print()
# Now we have enough information to create an encrypting context
# and decrypting the data.
encrypt_ctx = nss.create_context_by_sym_key(mechanism, nss.CKA_ENCRYPT,
sym_key, params)
# Return the encrypting context and it's parameter block so that the
# decryption context can use the same parameter block.
return encrypt_ctx, params_base64
def get_decryption_context(alg_id, sym_key, params_base64):
# Build a decryption context using the same parameters used
# when the encryption context was created.
# Do NOT use the params returned by get_pbe_crypto_mechanism()
# because the params often include an IV (Initialization Vector)
# created with random data, therefore the params used in the
# encryption context will not match the params needed for the
# decryption context. Instead use the params used in the
# encryption context. For interoperability reasons we exchange the
# params as base64 encoded binary data.
mechanism, params = alg_id.get_pbe_crypto_mechanism(sym_key)
# Recreate the params used during encryption by initializing a
# SecItem from base64 text data (indicated by ascii=True)
params = nss.SecItem(params_base64, ascii=True)
if not options.quiet:
print(fmt_info("get_pbe_crypto_mechanism (decrypting) returned mechanism:",
nss.key_mechanism_type_name(mechanism)))
print()
# Now we have enough information to create a decrypting context
decrypt_ctx = nss.create_context_by_sym_key(mechanism, nss.CKA_DECRYPT,
sym_key, params)
return decrypt_ctx
def do_pbkdf2():
# Generate a symmetric key
alg_id, sym_key = generate_key()
# Get encryption contexts to encrypt
encrypt_ctx, params_base64 = get_encryption_context(alg_id, sym_key)
# First encrypt the plain text input
print(fmt_info("Plain Text", options.plain_text))
print()
# Encode the plain text by feeding it to cipher_op getting cipher text back.
# Append the final bit of cipher text by calling digest_final
cipher_text = encrypt_ctx.cipher_op(options.plain_text.encode('utf-8'))
cipher_text += encrypt_ctx.digest_final()
print(fmt_info("Cipher Text", cipher_text, hex_data=True))
print()
# Get decryption contexts to decrypt
decrypt_ctx = get_decryption_context(alg_id, sym_key, params_base64)
# Decode the cipher text by feeding it to cipher_op getting plain text back.
# Append the final bit of plain text by calling digest_final
decoded_text = decrypt_ctx.cipher_op(cipher_text)
decoded_text += decrypt_ctx.digest_final()
decoded_text = decoded_text.decode('utf-8')
print(fmt_info("Decoded Text", decoded_text))
print()
#-------------------------------------------------------------------------------
def main():
global options
parser = argparse.ArgumentParser(description='Password Based Encryption Example')
parser.add_argument('-q', '--quiet', action='store_true',
help='stiffle chatty output')
# === NSS Database Group ===
group = parser.add_argument_group('PBKDF2',
'Specify the PBKDF2 parameters')
group.add_argument('--pbe-alg',
help='password based encryption algorithm')
group.add_argument('--cipher-alg',
help='cipher algorithm')
group.add_argument('--prf-alg',
help='pseudo-random function algorithm')
group.add_argument('-l', '--key-length',
help='number of octets in derived key')
group.add_argument('-s', '--salt',
help='salt as a string, if none then use random data')
group = parser.add_argument_group('Encryption',
'Specify the encryption parameters')
group.add_argument('-p', '--password',
help='PBE password')
group.add_argument('-t', '--plain-text',
help='string to encrypt')
parser.set_defaults(pbe_alg = 'SEC_OID_PKCS5_PBKDF2',
cipher_alg = 'SEC_OID_AES_256_CBC',
prf_alg = 'SEC_OID_HMAC_SHA1',
iterations = 100,
key_length = 0,
salt = None,
password = 'password',
plain_text = 'Black holes are where God divided by zero - Steven Wright',
)
options = parser.parse_args()
# Initialize NSS.
nss.nss_init_nodb()
do_pbkdf2()
#-------------------------------------------------------------------------------
if __name__ == "__main__":
sys.exit(main())
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