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add private _int_to_bn method to openssl backend

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This commit is contained in:
Paul Kehrer 2014-02-20 17:59:03 -06:00
parent 5a2496b03e
commit 83274d581e
1 changed files with 15 additions and 5 deletions
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20
cryptography/hazmat/backends/openssl/backend.py
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@ -274,6 +274,20 @@ class Backend(object):
self._lib.OPENSSL_free(hex_cdata)
return int(hex_str, 16)
def _int_to_bn(self, num):
"""
Converts a python integer to a BIGNUM. The returned BIGNUM will not
be garbage collected (to support adding them to structs that take
ownership of the object). Be sure to register it for GC if it will
be discarded after use.
"""
hex_num = hex(num).rstrip("L").lstrip("0x") or "0"
bn_ptr = self._ffi.new("BIGNUM **")
res = self._lib.BN_hex2bn(bn_ptr, hex_num)
assert res != 0
assert bn_ptr[0] != self._ffi.NULL
return bn_ptr[0]
def generate_rsa_private_key(self, public_exponent, key_size):
if public_exponent < 3:
raise ValueError("public_exponent must be >= 3")
@ -288,13 +302,9 @@ class Backend(object):
assert ctx != self._ffi.NULL
ctx = self._ffi.gc(ctx, self._lib.RSA_free)
bn = self._lib.BN_new()
assert bn != self._ffi.NULL
bn = self._int_to_bn(public_exponent)
bn = self._ffi.gc(bn, self._lib.BN_free)
res = self._lib.BN_set_word(bn, public_exponent)
assert res == 1
res = self._lib.RSA_generate_key_ex(
ctx, key_size, bn, self._ffi.NULL
)