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Use PBKDF2HMAC() from cryptography for vault keys.

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When stretching the key for vault files, use PBKDF2HMAC() from the
cryptography package instead of pycrypto. This will speed up the opening
of vault files by ~10x.

The problem is here in lib/ansible/utils/vault.py:

    hash_function = SHA256

    # make two keys and one iv
    pbkdf2_prf = lambda p, s: HMAC.new(p, s, hash_function).digest()

    derivedkey = PBKDF2(password, salt, dkLen=(2 * keylength) + ivlength,
                        count=10000, prf=pbkdf2_prf)

`PBKDF2()` calls a Python callback function (`pbkdf2_pr()`) 10000 times.
If one has several vault files, this will cause excessive start times
with `ansible` or `ansible-playbook` (we experience ~15 second startup
times).

Testing the original implementation in 1.9.2 with a vault file:

In [2]: %timeit v.decrypt(encrypted_data)
1 loops, best of 3: 265 ms per loop

Having a recent OpenSSL version and using the vault.py changes in this commit:

In [2]: %timeit v.decrypt(encrypted_data)
10 loops, best of 3: 23.2 ms per loop
This commit is contained in:
Vilmos Nebehaj 2015-07-22 19:52:42 +02:00
parent e505a1b7c4
commit 58cccce384
1 changed files with 34 additions and 8 deletions
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42
lib/ansible/parsing/vault/__init__.py
View file

@ -81,6 +81,18 @@ try:
except ImportError:
HAS_AES = False
# OpenSSL pbkdf2_hmac
HAS_PBKDF2HMAC = False
try:
from cryptography.hazmat.primitives.hashes import SHA256 as c_SHA256
from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
from cryptography.hazmat.backends import default_backend
HAS_PBKDF2HMAC = True
except ImportError:
pass
HAS_ANY_PBKDF2HMAC = HAS_PBKDF2 or HAS_PBKDF2HMAC
CRYPTO_UPGRADE = "ansible-vault requires a newer version of pycrypto than the one installed on your platform. You may fix this with OS-specific commands such as: yum install python-devel; rpm -e --nodeps python-crypto; pip install pycrypto"
HEADER=u'$ANSIBLE_VAULT'
@ -89,7 +101,7 @@ CIPHER_WHITELIST=['AES', 'AES256']
def check_prereqs():
if not HAS_AES or not HAS_COUNTER or not HAS_PBKDF2 or not HAS_HASH:
if not HAS_AES or not HAS_COUNTER or not HAS_ANY_PBKDF2HMAC or not HAS_HASH:
raise AnsibleError(CRYPTO_UPGRADE)
class VaultLib(object):
@ -551,13 +563,7 @@ class VaultAES256(object):
check_prereqs()
def gen_key_initctr(self, password, salt):
# 16 for AES 128, 32 for AES256
keylength = 32
# match the size used for counter.new to avoid extra work
ivlength = 16
def create_key(self, password, salt, keylength, ivlength):
hash_function = SHA256
# make two keys and one iv
@ -566,6 +572,26 @@ class VaultAES256(object):
derivedkey = PBKDF2(password, salt, dkLen=(2 * keylength) + ivlength,
count=10000, prf=pbkdf2_prf)
return derivedkey
def gen_key_initctr(self, password, salt):
# 16 for AES 128, 32 for AES256
keylength = 32
# match the size used for counter.new to avoid extra work
ivlength = 16
if HAS_PBKDF2HMAC:
backend = default_backend()
kdf = PBKDF2HMAC(
algorithm=c_SHA256(),
length=2 * keylength + ivlength,
salt=salt,
iterations=10000,
backend=backend)
derivedkey = kdf.derive(password)
else:
derivedkey = self.create_key(password, salt, keylength, ivlength)
key1 = derivedkey[:keylength]
key2 = derivedkey[keylength:(keylength * 2)]