OPENSSL GOST ENGINE

An implementation of Russian cryptography standards for OpenSSL.

Since v.0.9.6 OpenSSL provides facilities for creating external dynamically
loaded cryptographic engines (OpenSSL should be built with dynamic engine
support to be able to use it). Since v 1.0 it became possible to provide
digital signature algorithms via engines.

This engine provides an implementation of various Russian cryptographic
algorithms, known generally as GOST cryptographic algorithms (see detailed list
below). These algorithms can be used both via OpenSSL command line tools and
via high-level libopenssl calls.

OpenSSL GOST Engine also includes 'gostsum' and 'gost12sum' command line tools
for generating and checking GOST R34.11-94 and GOST R34.11-2012 hashsums.
They have the same purposes and behavior as the well-known sha1sum and md5sum
utilities. These utilities can be used independently from OpenSSL.

ALGORITHMS SUPPORTED

GOST R 34.10-2001 and GOST R 34.10-2012 - digital signature algorithms.
   Also support key exchange based on public keys. See RFC 4357 for
   details of VKO key exchange algorithm. These algorithms use
   256 bit private keys for GOST 2001, 256/512 bits for GOST 2012. 
	 Public keys are 512 bit for GOST 2001 and 512/1024 for GOST 2012. 
	 Key exchange algorithms (VKO R 34.10) are supported on these keys too.
  
GOST R 34.11-94  Message digest algorithm. 256-bit hash value.

GOST R 34.11-2012  Message digest algorithm. 256- and 512-bit hash values.

GOST 28147-89 - Symmetric cipher with 256-bit key. Various modes are
   defined in the standard, but only CBC, CFB and CNT modes are implemented
   in the engine. To make statistical analysis more difficult, key
   meshing is supported (see RFC 4357).

GOST 28147-89 MAC mode. Message authentication code. While a lot of MAC
  algorithms out there are based on hash functions using HMAC algorithm, 
	this algoritm is based on symmetric cipher. 
	It has 256-bit symmetric key and 8-64 (default 32) bits of MAC value
	(while HMAC has same key size and value size). 
	It is implemented as combination of EVP_PKEY type and EVP_MD type.

GOST R 34.13–2015 - Symmetric cypher Grasshopper ("Kuznechik")

USAGE OF GOST ALGORITHMS

This engine is designed to allow usage of this algorithms in the high-level
openssl functions, such as PKI, S/MIME and TLS. All the necessary constants are
added to the main source tree of OpenSSL.

See RFC 4490 for S/MIME with GOST algorithms and RFC 4491 for PKI.  TLS support
is implemented according IETF draft-chudov-cryptopro-cptls-03.txt and is
compatible with CryptoPro CSP 3.0+.

To use the engine you have to load it via openssl configuration
file. Applications should read openssl configuration file or provide
their own means to load engines. Also, applications which operate with
private keys, should use generic EVP_PKEY API instead of using RSA or
other algorithm-specific API.

USAGE WITH COMMAND LINE openssl UTILITY

1. Generation of private key

	openssl genpkey -algorithm gost2001 -pkeyopt paramset:A -out seckey.pem

  Use -algorithm option to specify algorithm.
  Use -pkeyopt option to pass paramset to algorithm. The following paramsets
  are supported by 
	gost2001:     0,A,B,C,XA,XB
	gost2012_256: 0,A,B,C,XA,XB,TCA,TCB,TCC,TCD
	gost2012_512:   A,B,C
  You can also use numeric representation of OID as to destinate
  paramset.

  Paramsets starting with X are intended to use for key exchange keys.
  Paramsets without X are for digital signature keys.

  Paramset for both algorithms 0 is the test paramset which should be used
  only for test purposes.

There are no algorithm-specific things with generation of certificate
request once you have a private key.

2. Generation of certificate request along with private/public keypar

   openssl req -newkey gost2001 -pkeyopt paramset:A

   Syntax of -pkeyopt parameter is identical with genpkey command.

   You can also use oldstyle syntax -newkey gost2001:paramfile, but in
   this case you should create parameter file first. 

   It can be created with

   openssl genpkey -genparam -algorithm gost2001 -pkeyopt paramset:A\
      -out paramfile.

3. S/MIME operations

If you want to send encrypted mail using GOST algorithms, don't forget
to specify -gost89 as encryption algorithm for OpenSSL smime command.
While OpenSSL is clever enough to find out that GOST R 34.11-94 digest
must be used for digital signing with GOST private key, it have no way
to derive symmetric encryption algorithm from key exchange keys.

4. TLS operations

OpenSSL supports all four ciphersuites defined in the IETF draft.
Once you've loaded GOST key and certificate into your TLS server,
ciphersuites which use GOST 28147-89 encryption are enabled.

Ciphersuites with NULL encryption should be enabled explicitely if
needed.

GOST2001-GOST89-GOST89 Uses GOST R 34.10-2001 for auth and key exchange,
		GOST 28147-89 for encryption and GOST 28147-89 MAC
GOST2001-NULL-GOST94 Uses GOST R 34.10-2001 for auth and key exchange,
    no encryption and HMAC, based on GOST R 34.11-94
GOST2012-GOST8912-GOST8912 Uses GOST R 34.10-2001 or 2012 for auth and key exchange,
		GOST 28147-89 with paramset Z for encryption and GOST 28147-89 MAC with paramset Z
GOST2012-NULL-GOST1 Uses GOST R 34.10-2001 or 2012 for auth and key exchange,
    no encryption and HMAC, based on GOST R 34.11-2012 256-bit.

RSA, DSA and EC keys can be used simultaneously with GOST keys, if
server implementation supports loading more than two private
key/certificate pairs. In this case ciphersuites which use any of loaded
keys would be supported and clients can negotiate ones they wish.

This allows creation of TLS servers which use GOST ciphersuites for
Russian clients and RSA/DSA ciphersuites for foreign clients.

5. Calculation of digests and symmetric encryption
 OpenSSL provides specific commands (like sha1, aes etc) for calculation
 of digests and symmetric encryption. Since such commands cannot be
 added dynamically, no such commands are provided for GOST algorithms.
 Use generic commands 'dgst' and 'enc'.

 Calculation of GOST R 34.11-94 message digest

 openssl dgst -md_gost94 datafile

 Note that GOST R 34.11-94 specifies that digest value should be
 interpreted as little-endian number, but OpenSSL outputs just hex dump
 of digest value.

 So, to obtain correct digest value, such as produced by gostsum utility
 included in the engine distribution, bytes of output should be
 reversed.
 
 Calculation of HMAC based on GOST R 34.11-94

 openssl dgst -md_gost94 -mac hmac -macopt key:<32 bytes of key> datafile
  
  (or use hexkey if key contain NUL bytes)
 Calculation of GOST 28147 MAC

 openssl dgst -mac gost-mac -macopt key:<32 bytes of key> datafile

 Note absence of an option that specifies digest algorithm. gost-mac
 algorithm supports only one digest (which is actually part of
 implementation of this mac) and OpenSSL is clever enough to find out
 this.

 Following mac options are supported:

 key:(32 bytes of key)

 hexkey:(64 hexadecimal digits of key)

 Engine support calculation of mac with size different from default 32
 bits. You can set mac size to any value from 1 to 8 bytes using

 -sigopt size:(number from 1 to 8 - mac size in bytes)

 (dgst command uses different EVP_PKEY_CTX for initialization and for
  finalization of MAC. Option of first are set via -macopt, and for
  second via -sigopt. Key should be set during initialization and size
  during finalization. If you use API functions
  EVP_DigestSignInit/EVP_DigestSignFinal, you can set both options at
  the same time).

 Encryption with GOST 28147 CFB mode
 openssl enc -gost89 -out encrypted-file -in plain-text-file -k <passphrase>  
 Encryption with GOST 28147 CNT mode
 openssl enc -gost89-cnt -out encrypted-file -in plain-text-file -k <passphrase>
 Encryption with GOST 28147 CBC mode
 openssl enc -gost89-cbc -out encrypted-file -in plain-text-file -k <passphrase>

6. Encrypting private keys and PKCS12

To produce PKCS12 files compatible with MagPro CSP, you need to use
GOST algorithm for encryption of PKCS12 file and also GOST R 34.11-94
hash to derive key from password.

openssl pksc12 -export -inkey gost.pem -in gost_cert.pem -keypbe gost89\
   -certpbe gost89 -macalg md_gost94
 
7. Testing speed of symmetric ciphers.
   
To test performance of GOST symmetric ciphers you should use -evp switch
of the openssl speed command. Engine-provided ciphers couldn't be
accessed by cipher-specific functions, only via generic evp interface

 openssl speed -evp gost89
 openssl speed -evp gost89-cnt
 openssl speed -evp gost89-cbc


PROGRAMMING INTERFACES DETAILS

Applications never should access engine directly. They only use provided
EVP_PKEY API. But there are some details, which should be taken into
account.

EVP provides two kinds of API for key exchange:

1. EVP_PKEY_encrypt/EVP_PKEY_decrypt functions, intended to use with
	RSA-like public key encryption algorithms

2. EVP_PKEY_derive, intended to use with Diffie-Hellman-like shared key
computing algorithms.

Although VKO R 34.10 algorithms, described in the RFC 4357 are
definitely second case, engine provides BOTH API for GOST R 34.10 keys.

EVP_PKEY_derive just invokes appropriate VKO algorithm and computes
256 bit shared key. VKO R 34.10-2001 requires 64 bits of random user key
material (UKM). This UKM should be transmitted to other party, so it is
not generated inside derive function.

It should be set by EVP_PKEY_CTX_ctrl function using
EVP_PKEY_CTRL_SET_IV command after call of EVP_PKEY_derive_init, but
before EVP_PKEY_derive.
	unsigned char ukm[8];
	RAND_bytes(ukm,8);
   EVP_PKEY_CTX_ctrl(ctx, -1, EVP_PKEY_OP_DERIVE, 8, ukm)

EVP_PKEY_encrypt encrypts provided session key with VKO shared key and
packs it into GOST key transport structure, described in the RFC 4490.

It typically uses ephemeral key pair to compute shared key and packs its
public part along with encrypted key. So, for most cases use of 
EVP_PKEY_encrypt/EVP_PKEY_decrypt with GOST keys is almost same as with
RSA.

However, if peerkey field in the EVP_PKEY_CTX structure is set (using
EVP_PKEY_derive_set_peerkey function) to EVP_PKEY structure which has private
key and uses same parameters as the public key from which this EVP_PKEY_CTX is
created, EVP_PKEY_encrypt will use this private key to compute shared key and
set ephemeral key in the GOST_key_transport structure to NULL. In this case
pkey and peerkey fields in the EVP_PKEY_CTX are used upside-down.

If EVP_PKEY_decrypt encounters GOST_key_transport structure with NULL
public key field, it tries to use peerkey field from the context to
compute shared key. In this case peerkey field should really contain
peer public key.

Encrypt operation supports EVP_PKEY_CTRL_SET_IV operation as well.
It can be used when some specific restriction on UKM are imposed by
higher level protocol. For instance, description of GOST ciphersuites
requires UKM to be derived from shared secret. 

If UKM is not set by this control command, encrypt operation would
generate random UKM.
