#!/usr/bin/env python """ Securely back up private keys from one Cryptech HSM to another. This works by having the destination HSM (the one importing keys) create an RSA keypair (the "KEKEK"), the public key of which can then be imported into the source HSM (the one exporting keys) and used to encrypt AES key encryption keys (KEKs) which in turn can be used to wrap the private keys being transfered. Transfers are encoded in JSON; the underlying ASN.1 formats are SubjectPublicKeyInfo (KEKEK public key) and PKCS #8 EncryptedPrivateKeyInfo (everything else). NOTE WELL: while this process makes it POSSIBLE to back up keys securely, it is not sufficient by itself: the operator MUST make sure only to export keys using a KEKEK known to have been generated by the target HSM. See the unit tests in the source repository for an example of how to fake this in a few lines of Python. We also implement a software-based variant on this backup mechanism, for cases where there is no second HSM. The protocol is much the same, but the KEKEK is generated in software and encrypted using a symmetric key derived from a passphrase using PBKDF2. This requires the PyCrypto library, and is only as secure as memory on the machine where you're running it (so it's theoretically vulnerable to root or anybody with access to /dev/mem). Don't use this mode unless you understand the risks, and see the "NOTE WELL" above. YOU HAVE BEEN WARNED. Be careful out there. """ # Diagram of the trivial protocol we're using: # # SOURCE HSM DESTINATION HSM # # Generate and export KEKEK: # hal_rpc_pkey_generate_rsa() # hal_rpc_pkey_get_public_key() # # Load KEKEK public <--------- Export KEKEK public # hal_rpc_pkey_load() # hal_rpc_pkey_export() # # Export PKCS #8 and KEK ----------> Load PKCS #8 and KEK, import key # hal_rpc_pkey_import() import sys import json import uuid import atexit import getpass import argparse from cryptech.libhal import * def main(): parser = argparse.ArgumentParser( formatter_class = argparse.RawDescriptionHelpFormatter, description = __doc__) subparsers = parser.add_subparsers( title = "Commands (use \"--help\" after command name for help with individual commands)", metavar = "") setup_parser = defcmd(subparsers, cmd_setup) export_parser = defcmd(subparsers, cmd_export) import_parser = defcmd(subparsers, cmd_import) setup_mutex_group = setup_parser.add_mutually_exclusive_group() parser.add_argument( "-p", "--pin", help = "wheel PIN") setup_mutex_group.add_argument( "-n", "--new", action = "store_true", help = "force creation of new KEKEK") setup_mutex_group.add_argument( "-u", "--uuid", help = "UUID of existing KEKEK to use") setup_mutex_group.add_argument( "-s", "--soft-backup", action = "store_true", help = "software-based backup, see warnings") setup_parser.add_argument( "-k", "--keylen", type = int, default = 2048, help = "length of new KEKEK if we need to create one") setup_parser.add_argument( "-o", "--output", type = argparse.FileType("w"), default = "-", help = "output file") export_parser.add_argument( "-i", "--input", type = argparse.FileType("r"), default = "-", help = "input file") export_parser.add_argument( "-o", "--output", type = argparse.FileType("w"), default = "-", help = "output file") import_parser.add_argument( "-i", "--input", type = argparse.FileType("r"), default = "-", help = "input file") args = parser.parse_args() hsm = HSM() try: hsm.login(HAL_USER_WHEEL, args.pin or getpass.getpass("Wheel PIN: ")) except HALError as e: sys.exit("Couldn't log into HSM: {}".format(e)) try: sys.exit(args.func(args, hsm)) finally: hsm.logout() def defcmd(subparsers, func): assert func.__name__.startswith("cmd_") subparser = subparsers.add_parser(func.__name__[4:], description = func.__doc__, help = func.__doc__.strip().splitlines()[0]) subparser.set_defaults(func = func) return subparser def b64(bytes): return bytes.encode("base64").splitlines() def b64join(lines): return "".join(lines).decode("base64") def cmd_setup(args, hsm): """ Set up backup HSM for subsequent import. Generates an RSA keypair with appropriate usage settings to use as a key-encryption-key-encryption-key (KEKEK), and writes the KEKEK to
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INC	= ../hal.h
LIB	= ../libhal.a
BIN	= eim_peek_poke cores

CFLAGS	= -g3 -Wall -fPIC -std=c99 -I..

all: ${BIN}

clean:
	rm -f *.o ${BIN}

${BIN}: %: %.o ${LIB}
	${CC} ${CFLAGS} -o $@ $^ ${LDFLAGS}

%.o: %.c ${INC}
	${CC} ${CFLAGS} -c -o $@ $<
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-22 20:04:45 +0000
tions, prf = lambda p, s: HMAC.new(p, s, SHA256).digest())) @classmethod def is_soft_key(cls, db): return all(k in db for k in ("kekek_pkcs8", "kekek_salt")) @classmethod def generate(cls, args, result): from Crypto.PublicKey import RSA self = cls() k = RSA.generate(args.keylen) salt = self.gen_salt() spki = k.publickey().exportKey(format = "DER") pkcs8 = self.encode_EncryptedPrivateKeyInfo(self.wrapper(salt).wrap( k.exportKey(format = "DER", pkcs = 8))) result.update(kekek_salt = b64(salt), kekek_pkcs8 = b64(pkcs8), kekek_pubkey = b64(spki)) @classmethod def recover(cls, db): self = cls() return self.wrapper(b64join(db["kekek_salt"])).unwrap( self.parse_EncryptedPrivateKeyInfo(b64join(db["kekek_pkcs8"]))) if __name__ == "__main__": main()