RE: [EXTERNAL] RE: DH_compute_key () - replacement in 3.0
From: Narayana, Sunil Kumar
Sent: Thursday, December 17, 2020 8:17 AM
To: Sands, Daniel ; openssl-users@openssl.org
Subject: [EXTERNAL] RE: DH_compute_key () - replacement in 3.0
Hi,
For the equivalent replacement of DH_compute_key in 3.0, we
tried to perform the steps suggested in earlier mail below
Our steps are as follows, but we see EVP_PKEY_derive fails to perform. please
suggest if any steps are wrong or missing here.
//input - BIGNUM - pubkey, privkey, p ,
//output - sharedsecret
Evp_compute_key(unsigned char* sharedSecret, unsigned int len, BIGNUM *pubkey,
BIGNUM *privkey, BIGNUM* dh_p)
{
OSSL_PARAM params[5];
unsigned char* p_str = BN_bn2dec (dh_p);
unsigned char* pub_str = BN_bn2dec (pubkey);
unsigned char* priv_str = BN_bn2dec (privkey);
params[0] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_FFC_P, p_str,
strlen(p_str));
params[1] = OSSL_PARAM_construct_uint(OSSL_PKEY_PARAM_FFC_G, &g);
params[2] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_PUB_KEY, pub_str,
strlen(pub_str));
params[3] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_PRIV_KEY, priv_str,
strlen(priv_str));
params[4] = OSSL_PARAM_construct_end();
gctx = EVP_PKEY_CTX_new_from_name(NULL, "DH", NULL);
EVP_PKEY_derive_init(gctx)
EVP_PKEY_CTX_set_params(gctx, params)
/* Determine buffer length */
EVP_PKEY_derive(gctx, NULL, &skeylen)
EVP_PKEY_derive(gctx, sharedSecret, &skeylen)
}
Note - EVP_PKEY_derive -- call fails what is wrong in the steps can you please g
To derive a shared secret, you also need your peer’s public key. It will also
be presented as an EVP_PKEY structure.
RE: [EXTERNAL] RE: DH_compute_key () - replacement in 3.0
Hi Daniel, Thanks we will try it out. One more doubt regarding DH_generate_key, as per earlier suggestion we tried following changes to replicate the generate key, but we observe that the out put key is not matching with the one that is obtained by DH_generate_key() of older version. Note that the inputs are same in both scenario. The generated key should be random. So unless you seed your PRNG with a constant value, you should always generate a different public/private keypair. Between OpenSSL versions, the PRNG may have changed, so I would not depend on them to output the same value even with the same PRNG seed.
RE: [EXTERNAL] RE: DH_compute_key () - replacement in 3.0
Hi Daniel, Thanks we will try it out. One more doubt regarding DH_generate_key, as per earlier suggestion we tried following changes to replicate the generate key, but we observe that the out put key is not matching with the one that is obtained by DH_generate_key() of older version. Note that the inputs are same in both scenario. Inputs to both EVP version & DH_generate_key are same as below… BIGNUM P input: C90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A4 BIGNUM G input: 2 (Code suggested to replace DH_generate_key ) …. EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_from_name(NULL, "DH", NULL); OSSL_PARAM_BLD *tmpl = NULL; OSSL_PARAM *params = NULL; EVP_PKEY *param_key = NULL; if (pctx == NULL || !EVP_PKEY_key_fromdata_init(pctx)) goto err; if ((tmpl = OSSL_PARAM_BLD_new()) == NULL || !OSSL_PARAM_BLD_push_BN(tmpl, OSSL_PKEY_PARAM_FFC_P, p) || !OSSL_PARAM_BLD_push_uint(tmpl, OSSL_PKEY_PARAM_FFC_G, 2)) goto err; params = OSSL_PARAM_BLD_to_param(tmpl); if (params == NULL || !EVP_PKEY_fromdata(pctx, ¶m_key, params)) EVP_PKEY *key = NULL; EVP_PKEY_CTX *gctx = EVP_PKEY_CTX_new_from_pkey(NULL, param_key, NULL); EVP_PKEY_keygen_init(gctx); EVP_PKEY_gen(gctx, &key); Post this we obtained DH from the key and printed dh->p, dh->g, dh->priv, dh->pub using below API dh = EVP_PKEY_get0_DH(pkey); DH_get0_key(dh, &dh_pubkey,&dh_privkey); DH_get0_pqg(dh, &dhp, &dhq, &dhg); BN_print_fp(dhfp, dh_pubkey);.. etc Note : post fetching DH from pkey, the input params (P,G) are matching properly. But pub/priv keys are not matching with the DH_generate_key output. Please suggest. Regards, Sunil From: Sands, Daniel Sent: 16 December 2020 05:00 To: Narayana, Sunil Kumar ; openssl-users@openssl.org Subject: RE: [EXTERNAL] RE: DH_compute_key () - replacement in 3.0 NOTICE: This email was received from an EXTERNAL sender We do have generated the key using EVP_PKEY_gen as suggested in earlier emails, but since this was a non-ephemeral and we wanted to store the key in "raw" octet bytes, so we did extracted the whole DH priv/pub key pair out from the key generated via EVP_PKEY_gen ( using as suggested… EVP_PKEY_get_raw_public_key (pkey, pub, &len) ) Now, at a later stage in application we have to compute the Secret key using the stored key’s (in above step). As of now, these keys are in uchar format, but are converted to BIGNUM and given to DH_compute_key as below. BIGNUM *bn_publicKey; dh->priv_key = BN_bin2bn(privateKey, octet_len, NULL); bn_publicKey = BN_bin2bn(publicKey, octet_len, NULL); rv = DH_compute_key(sharedSecret, bn_publicKey, dh); So in order to keep the existing frame work in place and just replace the DH_compute_key, we should be using the dh->priv_key/ bn_publicKey to compute shared secret key. So we require to convert the BIGNUM key types to EVP_KEY types to use in EVP_PKEY_derive_init, EVP_PKEY_derive_set_peer, and EVP_PKEY_derive to get shared secret Please suggest… Is it possible to change the format of your raw blob? If so, you can use i2d_PrivateKey or friends to output the entire private key to your raw data blob, and use d2i_PrivateKey et al to read it back into a working EVP_PKEY in a single call. Otherwise, one shortcut you can do to avoid all the params work is to create a static array since you should already know how many params you need. But you need the public key, the private key, the generator (g), and the prime modulus (p). The following (untested) code ought to work. OSSL_PARAM params[5]; params[0] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_FFC_P, , ); params[1] = OSSL_PARAM_construct_uint(OSSL_PKEY_PARAM_FFC_G, ); params[2] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_PUB_KEY, , ); params[3] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_PRIV_KEY, , ); params[4] = OSSL_PARAM_construct_end(); my_key_ctx = EVP_PKEY_CTX_new_from_name(NULL, “DH”, NULL); EVP_PKEY_derive_init(my_key_ctx); EVP_PKEY_CTX_set_params(my_key_ctx, params); … --- Notice: This e-mail together with any attachments may contain information of Ribbon Communications Inc. that is confidential and/or proprietary for the sole use of the intended recipient. Any review, disclosure, reliance or distribution by others or forwarding without express permission is strictly prohibited. If you are not the intended recipient, please notify the sender immediately and then delete all copies, including any attachments. ---
RE: [EXTERNAL] RE: DH_compute_key () - replacement in 3.0
We do have generated the key using EVP_PKEY_gen as suggested in earlier emails, but since this was a non-ephemeral and we wanted to store the key in "raw" octet bytes, so we did extracted the whole DH priv/pub key pair out from the key generated via EVP_PKEY_gen ( using as suggested… EVP_PKEY_get_raw_public_key (pkey, pub, &len) ) Now, at a later stage in application we have to compute the Secret key using the stored key’s (in above step). As of now, these keys are in uchar format, but are converted to BIGNUM and given to DH_compute_key as below. BIGNUM *bn_publicKey; dh->priv_key = BN_bin2bn(privateKey, octet_len, NULL); bn_publicKey = BN_bin2bn(publicKey, octet_len, NULL); rv = DH_compute_key(sharedSecret, bn_publicKey, dh); So in order to keep the existing frame work in place and just replace the DH_compute_key, we should be using the dh->priv_key/ bn_publicKey to compute shared secret key. So we require to convert the BIGNUM key types to EVP_KEY types to use in EVP_PKEY_derive_init, EVP_PKEY_derive_set_peer, and EVP_PKEY_derive to get shared secret Please suggest… Is it possible to change the format of your raw blob? If so, you can use i2d_PrivateKey or friends to output the entire private key to your raw data blob, and use d2i_PrivateKey et al to read it back into a working EVP_PKEY in a single call. Otherwise, one shortcut you can do to avoid all the params work is to create a static array since you should already know how many params you need. But you need the public key, the private key, the generator (g), and the prime modulus (p). The following (untested) code ought to work. OSSL_PARAM params[5]; params[0] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_FFC_P, , ); params[1] = OSSL_PARAM_construct_uint(OSSL_PKEY_PARAM_FFC_G, ); params[2] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_PUB_KEY, , ); params[3] = OSSL_PARAM_construct_BN(OSSL_PKEY_PARAM_PRIV_KEY, , ); params[4] = OSSL_PARAM_construct_end(); my_key_ctx = EVP_PKEY_CTX_new_from_name(NULL, “DH”, NULL); EVP_PKEY_derive_init(my_key_ctx); EVP_PKEY_CTX_set_params(my_key_ctx, params); …
