| Network Working Group | S. Smyshlyaev, Ed. |
| Internet-Draft | CryptoPro |
| Intended status: Informational | D. Belyavsky |
| Expires: December 31, 2018 | Cryptocom |
| M. Saarinen | |
| Independent Consultant | |
| June 29, 2018 |
GOST Cipher Suites for TLS 1.2
draft-smyshlyaev-tls12-gost-suites-01
This document specifies a set of cipher suites for the Transport Layer Security (TLS) protocol Version 1.2 to support the Russian cryptographic standard algorithms.
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This document specifies three new cipher suites for the Transport Layer Security (TLS) Protocol Version 1.2 [RFC5246] to support the set of Russian cryptographic standard algorithms (called GOST algorithms). All of them use the GOST R 34.11-2012 [GOST3411-2012] hash algorithm (the English version can be found in [RFC6986]) and the GOST R 34.10-2012 [GOST3410-2012] signature algorithm (the English version can be found in [RFC7091]) but use different encryption algorithms, so they are divided into two types: the CTR_OMAC cipher suites and the CNT_IMIT cipher suite.
The CTR_OMAC cipher suites use the GOST R 34.12-2015 [GOST3412-2015] block ciphers (the English version can be found in [RFC7801]):
The CNT_IMIT cipher suites use the GOST 28147-89 [GOST28147-89] block cipher (the English version can be found in [RFC5830]):
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
This document uses the following terms and definitions for the sets and operations on the elements of these sets:
All of the cipher suites described in this document MUST use the stream cipher (see Section 4.3.3) to protect records. The TLSCiphertext structure for the CTR_OMAC and CNT_IMIT cipher suits is specified in accordance with the GenericStreamCipher case (see Section 6.2.3.1 of [RFC5246]):
struct {
ContentType type;
ProtocolVersion version;
uint16 length;
GenericStreamCipher fragment;
} TLSCiphertext;
Here TLSCiphertext.fragment is generated as described in Section 4.1.1 and Section 4.1.2.
The connection key material consists of the sender_write_key (either the client_write_key or the server_write_key), the sender_write_MAC_key (either the client_write_MAC_key or the server_write_MAC_key) and the sender_write_IV (either the client_write_IV or the server_write_IV) parameters that are generated according to section 6.3 of [RFC5246].
In case of the CTR_OMAC cipher_suites there is a certain key material which is used by the peer to protect a record that corresponds to the seqnum sequence number (in the following simply record key material) and consist of K_ENC_seqnum, K_MAC_seqnum and IV_seqnum values that are calculated using the TLSTREE function defined in Section 5.1 and the connection key material:
The TLSCiphertext.fragment that corresponds to the seqnum sequence number is equal to the ENCValue_seqnum value that is calculated as follows:
1. The MAC value (MACValue_seqnum) is generated by the MAC algorithm (see Section 4.3.2) similar to Section 6.2.3.1 of [RFC5246] except the used MAC key: the sender_write_MAC_key is replaced by the K^seqnum_MAC key:
where type_seqnum, version_seqnum, length_seqnum, fragment_seqnum are the TLSCompressed.type, the TLSCompressed.version, the TLSCompressed.length and the TLSCompressed.fragment values of the record with the seqnum sequence number.
2. The stream cipher ENC (see Section 4.3.3) encrypts the entire data with the MACValue as follows:
In case of the CNT_IMIT cipher_suites the TLSCiphertext.fragment that corresponds to the seqnum sequence number is equal to the ENCValue_seqnum value that is calculated as follows:
1. The MAC value (MACValue_seqnum) is generated by the MAC algorithm (see Section 4.3.2) as follows:
where type_i, version_i, length_i, fragment_i are the TLSCompressed.type, the TLSCompressed.version, the TLSCompressed.length and the TLSCompressed.fragment values of the record with the i sequence number.
2. The stream cipher ENC (see Section 4.3.3) encrypts the entire data ENCData_i with the MACValue_i that correspond to the record sequence number i with the MACValue as follows:
All of the cipher suites described in this document use ECDH to compute the TLS premaster secret.
Client Server
ClientHello -------->
ServerHello
Certificate
CertificateRequest*
<-------- ServerHelloDone
Certificate*
ClientKeyExchange
CertificateVerify*
[ChangeCipherSpec]
Finished -------->
[ChangeCipherSpec]
<-------- Finished
Application Data <-------> Application Data
* message is not sent unless client authentication is desired
Figure 1 shows all messages involved in the TLS key establishment protocol (aka full handshake). A ServerKeyExchange MUST NOT be sent (the server's certificate contains all the necessary keying information required by the client to arrive at the premaster secret).
The key exchange process consists of the following steps:
The server side of the channel is always authenticated; the client side is optionally authenticated. The server is authenticated using it's long term private key from the certificate and proving that it knows a shared secret. The client is authenticated when the server is checking its signature.
The proposed cipher suites has direct impact only on the ClientHello, the ServerHello, the CertificateRequest, the ClientKeyExchange and the CertificateVerify handshake messages, that are described bellow in greater detail in terms of the content and processing of these messages.
The ClientHello message must meet the following requirements:
The ServerHello message must meet the following requirements:
Note: If the extended_master_secret extension is agreed, then the master secret value MUST be calculated in accordance with [RFC7627].
The signature_algorithms extension is described in Section 7.4.1.4.1 of (see [RFC5246]) and is specified as follows.
SignatureAndHashAlgorithm
supported_signature_algorithms<2..2^16-2>;
struct {
HashAlgorithm hash;
SignatureAlgorithm signature;
} SignatureAndHashAlgorithm;
The set of supported hash algorithms is specified as follows:
enum {
gostr34112012_256(238),
gostr34112012_512(239), (255)
} HashAlgorithm;
where gostr34112012_256 and gostr34112012_512 values correspond to the GOST R 34.11-2012 [GOST3411-2012] hash algorithm with 32-byte (256-bit) and 64-byte (512-bit) hash code respectively.
The set of supported signature algorithms is specified as follows:
enum {
gostr34102012_256(238),
gostr34102012_512(239), (255)
} SignatureAlgorithm;
where gostr34102012_256 and gostr34102012_512 values correspond to the GOST R 34.10-2012 [GOST3410-2012] signature algorithm with 32-byte (256-bit) and 64-byte (512-bit) key length respectively.
When this message is sent: this message is sent when requesting client authentication.
Meaning of this message: the server uses this message to suggest acceptable certificates.
The TLS CertificateRequest message is extended as follows.
struct {
ClientCertificateType certificate_types<1..2^8-1>;
SignatureAndHashAlgorithm
supported_signature_algorithms<2..2^16-2>;
DistinguishedName certificate_authorities<0..2^16-1>;
} CertificateRequest;
where the SignatureAndHashAlgorithm structure is specified in Section 4.2.1.1, the ClientCertificateType and the DistinguishedName structures are specified as follows.
enum {
gostr34102012_256(238),
gostr34102012_512(239), (255)
} ClientCertificateType;
opaque DistinguishedName<1..2^16-1>;
The ClientKeyExchange structure is defined as follows.
enum { vko_kdf_gost, vko_gost } KeyExchangeAlgorithm;
struct {
select (KeyExchangeAlgorithm) {
case vko_kdf_gost: PSKeyTransport;
case vko_gost: TLSGostKeyTransportBlob;
} exchange_keys;
} ClientKeyExchange;
The PSKeyTransport structure corresponds to the CTR_OMAC cipher suites and is described in Section 4.2.3.1 and the TLSGostKeyTransportBlob corresponds to CNT_IMIT cipher suite and is described in Section 4.2.3.2.
The CTR_OMAC cipher suites use the KExp15 and the KImp15 algorithms defined in Section 5.2 for key wrapping.
The export representation of the PS value is calculated as follows.
1. The client generates the keys K^EXP_MAC and K^EXP_ENC using the KEG function described in Section 5.3:
2. The client generates export representation of the premaster secret value PS:
3. The client creates the PSKeyTransport structure that is defined as follows:
PSKeyTransport ::= SEQUENCE {
PSEXP OCTET STRING,
ephemeralPublicKey SubjectPublicKeyInfo
}
SubjectPublicKeyInfo ::= SEQUENCE {
algorithm AlgorithmIdentifier,
subjectPublicKey BITSTRING
}
AlgorithmIdentifier ::= SEQUENCE {
algorithm OBJECT IDENTIFIER,
parameters ANY OPTIONAL
}
Here the PSEXP field contains the PSExp value and the ephemeralPublicKey field contains the Q_eph value.
After receiving the ClientKeyExchange message the server process it as follows.
1. Checks the next three conditions fulfilling and terminates the connection with fatal error if not.
2. Generates the keys K^EXP_MAC and K^EXP_ENC using the KEG function described in Section 5.3:
3. Extracts the common secret PS from the export representation PSExp:
The client generates the key KEK using the VKO function. VKO is one of the functions VKO_GOSTR3410_2012_256 or VKO_GOSTR3410_2012_512 described in [RFC7836]. The particular function depends on the elliptic curve used in the server certificate. The KEK calculation is made as follow
Generates the diversified key KEK(UKM) using the function CryptoPro KEK Diversification Algorithm defined in [RFC4357]
Generates export representation of the common secret PS:
The TLSGostKeyTransportBlob is defined as
TLSGostKeyTransportBlob ::= SEQUENCE {
keyBlob GostR3410-KeyTransport,
}
GostR3410-KeyTransport ::=
SEQUENCE {
sessionEncryptedKey Gost28147-89-EncryptedKey,
transportParameters [0] IMPLICIT GostR3410-TransportParameters
}
Gost28147-89-EncryptedKey ::=
SEQUENCE {
encryptedKey Gost28147-89-Key,
macKey Gost28147-89-MAC
}
GostR3410-TransportParameters ::=
SEQUENCE {
encryptionParamSet OBJECT IDENTIFIER,
ephemeralPublicKey [0] IMPLICIT SubjectPublicKeyInfo,
ukm OCTET STRING
}
The Gost28147-89-EncryptedKey.encryptedKey value contais CEK_ENC value, the Gost28147-89-EncryptedKey.macKey contains CEK_MAC, and GostR3410-TransportParameters.ukm contains the UKM value.
There MUST be a keyBlob.transportParameters.ephemeralPublicKey field containing the client ephemeral public key Q_eph.
After receiving ClientKeyExchange message server process it as follows
The TLS CertificateVerify message is extended as follows.
struct {
SignatureAndHashAlgorithm algorithm;
opaque signature<0..2^16-1>;
} CertificateVerify;
where SignatureAndHashAlgorithm structure is specified in Section 4.2.1.1.
The CertificateVerify.signature field is specified as follows.
CertificateVerify.signature = SIGN_{k_C}(handshake_messages) = Str_l(r) | Str_l(s)
where SIGN_{k_C} is the GOST R 34.10-2012 [GOST3410-2012] signature algorithm, k_C is a client long-term private key that corresponds to the client long-term public key Q_C from the client's certificate, l = 32 for gostr34102012_256 signature algorithm and l = 64 for gostr34102012_512 signature algorithm.
The cipher suite TLS_GOSTR341112_256_WITH_KUZNYECHIK_CTR_OMAC MUST use Kuznyechik [RFC7801] as a base block cipher for the encryption and MAC algorithm. The block length for this suite is 16 bytes and the key length is 32 bytes. The cipher suite TLS_GOSTR341112_256_WITH_MAGMA_CTR_OMAC MUST use Magma [GOST3412-2015] as a base block cipher for the encryption and MAC algorithm. The block length for this suite is 8 bytes and the key length is 32 bytes.
The cipher suite TLS_GOSTR341112_256_WITH_28147_CNT_IMIT MUST use GOST 28147-89 as a base block cipher [RFC5830] with the set of parameters id-tc26-gost-28147-param-Z defined in [RFC7836]. The block length for this suite is 8 bytes and the key length is 32 bytes.
The CTR_OMAC cipher suites use the OMAC message authentication code construction defined in [GOST3413-2015], which can be considered as the CMAC mode defined in [RFC4493] where Kuznyechik or Magma block cipher (see Section 4.3.1) are used instead of AES block cipher (see [IK2003] for more detail) as the MAC function.
The CNT_IMIT cipher suite uses the message authentication code function gostIMIT28147 defined in Section 5.4 with the initialization vector IV = IV0, where IV0 in B_8 is a string of all zeros, with the CryptoPro Key Meshing algorithm defined in [RFC4357].
The CTR_OMAC cipher suites use the block cipher in CTR-ACPKM encryption mode defined in [DraftRekeying] as the ENC encryption algorithm. The section size N is 4 KB for TLS_GOSTR341112_256_WITH_KUZNYECHIK_CTR_OMAC cipher suite and 1 KB for TLS_GOSTR341112_256_WITH_MAGMA_CTR_OMAC cipher suite. The initial counter nonce is defined as in Section 4.1.
The CNT_IMIT cipher suite uses use the block cipher in counter encryption mode (CNT) defined in Section 6 of [RFC5830] with the CryptoPro Key Meshing algorithm defined in [RFC4357] as the ENC encryption algorithm.
The SNMAX parameter defines the maximal amount of messages that can be send during one TLS 1.2 connection. For TLS_GOSTR341112_256_WITH_KUZNYECHIK_CTR_OMAC cipher suite this amount is 2^64 - 1 messages and for TLS_GOSTR341112_256_WITH_MAGMA_CTR_OMAC is 2^32 - 1 messages.
The pseudorandom function (PRF) for all the cipher suites defined in this document is the PRF_TLS_GOSTR3411_2012_256 function described in [RFC7836].
The hash function Hash for all the cipher suites defined in this document is the GOST R 34.11-2012 [GOST3411-2012] hash algorithm with 32-byte (256-bit) hash code.
The TLSTREE function is defined as follows:
where
The CTR_OMAC cipher suites use the TLSTREE function for the re-keying approach. The constants for it are defined as in the table below.
Key tree constants
| CipherSuites | C_1, C_2, C_3 |
|---|---|
| TLS_GOSTR341112_256_WITH_KUZNYECHIK_CTR_OMAC | C_1=0xFFFFFFFF00000000, C_2=0xFFFFFFFFFFF80000, C_3=0xFFFFFFFFFFFFFFC0 |
| TLS_GOSTR341112_256_WITH_MAGMA_CTR_OMAC | C_1=0xFFFFFFC000000000, C_2=0xFFFFFFFFFE000000, C_3=0xFFFFFFFFFFFFF000 |
Algorithms KExp15 and KImp15 are keywrap algorithms those provide confidentiality and integrity of keys. These algorithms use the block cipher defined by the particular cipher suite.
The inputs of Kexp15 key export algorithm are
The keys K^Exp_MAC and K^Exp_ENC MUST be independent. The export representation of the key K is computed as follows
The import of key K via KImp15 algorithm is restoring the key K from export representation KEXP with keys K^Exp_MAC and K^Exp_ENC from B_k and value IV from B_{n/2}. This is performed as follows
During the use of one keypair (K^Exp_ENC, K^Exp_MAC) the IV values MUST be unique. For the import of key K with the KImp15 algorithm every IV value MUST be sent with the export key representation or be a preshared value.
The KEG algorithm of export key elaboration takes on input private key d, public key Q and string h from B_32. Then it returns the string from B_64.
The KEG algorithm is defined by two distinct ways depending on the private key length.
If the length of private key d is 64 bytes the KEG algorithm is defined as follows:
KEG(d, Q, h) = VKO_512(d, Q, UKM),
where VKO_512 is the VKO_GOSTR3410_2012_512 function defined in [RFC7836] and the UKM parameter is equal to r = Int_32(h[1..16]) if r is not equal to 0 and is equal to 1 otherwise.
If the length of private key d is 32 bytes the KEG algorithm is defined as follows:
KEG(d, Q, h) = KDFTREE_256(K_EXP, "kdf tree", seed, 1),
where KDFTREE_256 is the KDF_TREE_GOSTR3411_2012_256 function defined in [RFC7836] and the parameters K_EXP and seed are defined as
where VKO_256 is the function VKO_GOSTR3410_2012_256 defined in [RFC7836].
gost28147IMIT (IV, K, M) IV in B_8, K in B_32, M in B* is a MAC computation algorithm with 4 bytes output that proceed as follow
IANA has added the following entries in the TLS Cipher Suite Registry: TODO