__all__ = ['MAC','DigestError']
class MAC(Digest):
- """
- This object represents MAC context. It is quite simular
- to digest algorithm. It is simular to hmac objects provided
- by standard library
- """
- def __init__(self,algorithm,key,digest=None,**kwargs):
- """
- Constructor has to obligatory arguments:
-
- @param algorithm - which is name of MAC algorithm i.e 'hmac' or
- 'gost-mac' or equivalent Oid object
- @param key - byte buffer with key.
+ """
+ This object represents MAC context. It is quite simular
+ to digest algorithm. It is simular to hmac objects provided
+ by standard library
+ """
+ def __init__(self,algorithm,key,digest=None,**kwargs):
+ """
+ Constructor has to obligatory arguments:
+
+ @param algorithm - which is name of MAC algorithm i.e 'hmac' or
+ 'gost-mac' or equivalent Oid object
+ @param key - byte buffer with key.
- Optional parameters are:
- digest - Oid or name of the digest algorithm to use. If none
- specified, OpenSSL will try to derive one from the MAC
- algorithm (or if algorithm is hmac, we'll substititute md5
- for compatibility with standard hmac module
+ Optional parameters are:
+ digest - Oid or name of the digest algorithm to use. If none
+ specified, OpenSSL will try to derive one from the MAC
+ algorithm (or if algorithm is hmac, we'll substititute md5
+ for compatibility with standard hmac module
- any other keyword argument is passed to EVP_PKEY_CTX as string
- option.
+ any other keyword argument is passed to EVP_PKEY_CTX as string
+ option.
- """
- if isinstance(algorithm,str):
- self.algorithm=Oid(algorithm)
- elif isinstance(algorithm,Oid):
- self.algorithm=algorithm
- else:
- raise TypeError("Algorthm must be string or Oid")
- if self.algorithm==Oid('hmac') and digest is None:
- digest='md5'
- self.name=self.algorithm.shortname().lower()
- if digest is not None:
- self.digest_type=DigestType(digest)
- self.name+='-'+self.digest_type.digest_name
- d=self.digest_type.digest
- else:
- self.digest_type=None
- d=None
- self.key=libcrypto.EVP_PKEY_new_mac_key(self.algorithm.nid,None,key,len(key))
- if self.key is None:
- raise DigestError("EVP_PKEY_new_mac_key")
- pctx=c_void_p()
- self.ctx = libcrypto.EVP_MD_CTX_create()
- if self.ctx == 0:
- raise DigestError("Unable to create digest context")
- if libcrypto.EVP_DigestSignInit(self.ctx,pointer(pctx),d,None,self.key) <= 0:
- raise DigestError("Unable to intialize digest context")
- self.digest_finalized=False
- if self.digest_type is None:
- self.digest_type=DigestType(Oid(libcrypto.EVP_MD_type(libcrypto.EVP_MD_CTX_md(self.ctx))))
- for (name,val) in kwargs.items():
- if EVP_PKEY_CTX_ctrl_str(ctx,name,val)<=0:
- raise DigestError("Unable to set mac parameter")
- self.digest_size = self.digest_type.digest_size()
- self.block_size = self.digest_type.block_size()
- def digest(self,data=None):
- """
- Method digest is redefined to return keyed MAC value instead of
- just digest.
- """
- if data is not None:
- self.update(data)
- b=create_string_buffer(256)
- size=c_size_t(256)
- if libcrypto.EVP_DigestSignFinal(self.ctx,b,pointer(size))<=0:
- raise DigestError('SignFinal')
- self.digest_finalized=True
- return b.raw[:size.value]
+ """
+ if isinstance(algorithm,str):
+ self.algorithm=Oid(algorithm)
+ elif isinstance(algorithm,Oid):
+ self.algorithm=algorithm
+ else:
+ raise TypeError("Algorthm must be string or Oid")
+ if self.algorithm==Oid('hmac') and digest is None:
+ digest='md5'
+ self.name=self.algorithm.shortname().lower()
+ if digest is not None:
+ self.digest_type=DigestType(digest)
+ self.name+='-'+self.digest_type.digest_name
+ d=self.digest_type.digest
+ else:
+ self.digest_type=None
+ d=None
+ self.key=libcrypto.EVP_PKEY_new_mac_key(self.algorithm.nid,None,key,len(key))
+ if self.key is None:
+ raise DigestError("EVP_PKEY_new_mac_key")
+ pctx=c_void_p()
+ self.ctx = self.newctx()
+ if self.ctx == 0:
+ raise DigestError("Unable to create digest context")
+ if libcrypto.EVP_DigestSignInit(self.ctx,pointer(pctx),d,None,self.key) <= 0:
+ raise DigestError("Unable to intialize digest context")
+ self.digest_finalized=False
+ if self.digest_type is None:
+ self.digest_type=DigestType(Oid(libcrypto.EVP_MD_type(libcrypto.EVP_MD_CTX_md(self.ctx))))
+ for (name,val) in kwargs.items():
+ if libcrypto.EVP_PKEY_CTX_ctrl_str(pctx,name,val)<=0:
+ raise DigestError("Unable to set mac parameter")
+ self.digest_size = self.digest_type.digest_size
+ self.block_size = self.digest_type.block_size
+ def digest(self,data=None):
+ """
+ Method digest is redefined to return keyed MAC value instead of
+ just digest.
+ """
+ if data is not None:
+ self.update(data)
+ b=create_string_buffer(256)
+ size=c_size_t(256)
+ if libcrypto.EVP_DigestSignFinal(self.ctx,b,pointer(size))<=0:
+ raise DigestError('SignFinal')
+ self.digest_finalized=True
+ return b.raw[:size.value]
libcrypto.EVP_DigestSignFinal.argtypes=(c_void_p,c_char_p,POINTER(c_size_t))
libcrypto.EVP_DigestSignFinal.restype=c_int
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