/* * Copyright 1995-2019 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the Apache License 2.0 (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy * in the file LICENSE in the source distribution or at * https://www.openssl.org/source/license.html */ #include #include "internal/cryptlib.h" #include "dh_local.h" #include "crypto/bn.h" static int generate_key(DH *dh); static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh); static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx); static int dh_init(DH *dh); static int dh_finish(DH *dh); int DH_generate_key(DH *dh) { return dh->meth->generate_key(dh); } int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) { return dh->meth->compute_key(key, pub_key, dh); } int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh) { int rv, pad; rv = dh->meth->compute_key(key, pub_key, dh); if (rv <= 0) return rv; pad = BN_num_bytes(dh->p) - rv; if (pad > 0) { memmove(key + pad, key, rv); memset(key, 0, pad); } return rv + pad; } static DH_METHOD dh_ossl = { "OpenSSL DH Method", generate_key, compute_key, dh_bn_mod_exp, dh_init, dh_finish, DH_FLAG_FIPS_METHOD, NULL, NULL }; static const DH_METHOD *default_DH_method = &dh_ossl; const DH_METHOD *DH_OpenSSL(void) { return &dh_ossl; } void DH_set_default_method(const DH_METHOD *meth) { default_DH_method = meth; } const DH_METHOD *DH_get_default_method(void) { return default_DH_method; } static int generate_key(DH *dh) { int ok = 0; int generate_new_key = 0; unsigned l; BN_CTX *ctx = NULL; BN_MONT_CTX *mont = NULL; BIGNUM *pub_key = NULL, *priv_key = NULL; if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { DHerr(DH_F_GENERATE_KEY, DH_R_MODULUS_TOO_LARGE); return 0; } if (BN_num_bits(dh->p) < DH_MIN_MODULUS_BITS) { DHerr(DH_F_GENERATE_KEY, DH_R_MODULUS_TOO_SMALL); return 0; } ctx = BN_CTX_new(); if (ctx == NULL) goto err; if (dh->priv_key == NULL) { priv_key = BN_secure_new(); if (priv_key == NULL) goto err; generate_new_key = 1; } else priv_key = dh->priv_key; if (dh->pub_key == NULL) { pub_key = BN_new(); if (pub_key == NULL) goto err; } else pub_key = dh->pub_key; if (dh->flags & DH_FLAG_CACHE_MONT_P) { mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, dh->lock, dh->p, ctx); if (!mont) goto err; } if (generate_new_key) { if (dh->q) { do { if (!BN_priv_rand_range(priv_key, dh->q)) goto err; } while (BN_is_zero(priv_key) || BN_is_one(priv_key)); } else { /* secret exponent length */ l = dh->length ? dh->length : BN_num_bits(dh->p) - 1; if (!BN_priv_rand(priv_key, l, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY)) goto err; /* * We handle just one known case where g is a quadratic non-residue: * for g = 2: p % 8 == 3 */ if (BN_is_word(dh->g, DH_GENERATOR_2) && !BN_is_bit_set(dh->p, 2)) { /* clear bit 0, since it won't be a secret anyway */ if (!BN_clear_bit(priv_key, 0)) goto err; } } } { BIGNUM *prk = BN_new(); if (prk == NULL) goto err; BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME); if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) { BN_clear_free(prk); goto err; } /* We MUST free prk before any further use of priv_key */ BN_clear_free(prk); } dh->pub_key = pub_key; dh->priv_key = priv_key; dh->dirty_cnt++; ok = 1; err: if (ok != 1) DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB); if (pub_key != dh->pub_key) BN_free(pub_key); if (priv_key != dh->priv_key) BN_free(priv_key); BN_CTX_free(ctx); return ok; } static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) { BN_CTX *ctx = NULL; BN_MONT_CTX *mont = NULL; BIGNUM *tmp; int ret = -1; int check_result; if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE); goto err; } if (BN_num_bits(dh->p) < DH_MIN_MODULUS_BITS) { DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_SMALL); return 0; } ctx = BN_CTX_new(); if (ctx == NULL) goto err; BN_CTX_start(ctx); tmp = BN_CTX_get(ctx); if (tmp == NULL) goto err; if (dh->priv_key == NULL) { DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE); goto err; } if (dh->flags & DH_FLAG_CACHE_MONT_P) { mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, dh->lock, dh->p, ctx); BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME); if (!mont) goto err; } if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) { DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY); goto err; } if (!dh-> meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, mont)) { DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB); goto err; } ret = BN_bn2bin(tmp, key); err: BN_CTX_end(ctx); BN_CTX_free(ctx); return ret; } static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx) { return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx); } static int dh_init(DH *dh) { dh->flags |= DH_FLAG_CACHE_MONT_P; return 1; } static int dh_finish(DH *dh) { BN_MONT_CTX_free(dh->method_mont_p); return 1; } int dh_buf2key(DH *dh, const unsigned char *buf, size_t len) { int err_reason = DH_R_BN_ERROR; BIGNUM *pubkey = NULL; const BIGNUM *p; size_t p_size; if ((pubkey = BN_bin2bn(buf, len, NULL)) == NULL) goto err; DH_get0_pqg(dh, &p, NULL, NULL); if (p == NULL || (p_size = BN_num_bytes(p)) == 0) { err_reason = DH_R_NO_PARAMETERS_SET; goto err; } /* * As per Section 4.2.8.1 of RFC 8446 fail if DHE's * public key is of size not equal to size of p */ if (BN_is_zero(pubkey) || p_size != len) { err_reason = DH_R_INVALID_PUBKEY; goto err; } if (DH_set0_key(dh, pubkey, NULL) != 1) goto err; return 1; err: DHerr(DH_F_DH_BUF2KEY, err_reason); BN_free(pubkey); return 0; } size_t dh_key2buf(const DH *dh, unsigned char **pbuf_out) { const BIGNUM *pubkey; unsigned char *pbuf; const BIGNUM *p; int p_size; DH_get0_pqg(dh, &p, NULL, NULL); DH_get0_key(dh, &pubkey, NULL); if (p == NULL || pubkey == NULL || (p_size = BN_num_bytes(p)) == 0 || BN_num_bytes(pubkey) == 0) { DHerr(DH_F_DH_KEY2BUF, DH_R_INVALID_PUBKEY); return 0; } if ((pbuf = OPENSSL_malloc(p_size)) == NULL) { DHerr(DH_F_DH_KEY2BUF, ERR_R_MALLOC_FAILURE); return 0; } /* * As per Section 4.2.8.1 of RFC 8446 left pad public * key with zeros to the size of p */ if (BN_bn2binpad(pubkey, pbuf, p_size) < 0) { OPENSSL_free(pbuf); DHerr(DH_F_DH_KEY2BUF, DH_R_BN_ERROR); return 0; } *pbuf_out = pbuf; return p_size; }