From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965284AbbEMT55 (ORCPT ); Wed, 13 May 2015 15:57:57 -0400 Received: from mail.eperm.de ([89.247.134.16]:34772 "EHLO mail.eperm.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964909AbbEMT5y (ORCPT ); Wed, 13 May 2015 15:57:54 -0400 From: Stephan Mueller To: herbert@gondor.apana.org.au Cc: pebolle@tiscali.nl, andreas.steffen@strongswan.org, tytso@mit.edu, sandyinchina@gmail.com, linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org Subject: [PATCH v6 4/5] crypto: drbg - use Jitter RNG to obtain seed Date: Wed, 13 May 2015 21:56:03 +0200 Message-ID: <2505598.oYHGFO1cAV@tachyon.chronox.de> User-Agent: KMail/4.14.7 (Linux/3.19.5-200.fc21.x86_64; KDE/4.14.7; x86_64; ; ) In-Reply-To: <1921857.OvxEu6y28S@tachyon.chronox.de> References: <1921857.OvxEu6y28S@tachyon.chronox.de> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org During initialization, the DRBG now tries to allocate a handle of the Jitter RNG. If such a Jitter RNG is available during seeding, the DRBG pulls the required entropy/nonce string from get_random_bytes and concatenates it with a string of equal size from the Jitter RNG. That combined string is now the seed for the DRBG. Written differently, the initial seed of the DRBG is now: get_random_bytes(entropy/nonce) || jitterentropy (entropy/nonce) If the Jitter RNG is not available, the DRBG only seeds from get_random_bytes. CC: Andreas Steffen CC: Theodore Ts'o CC: Sandy Harris Signed-off-by: Stephan Mueller --- crypto/drbg.c | 46 ++++++++++++++++++++++++++++++++++++++++------ include/crypto/drbg.h | 1 + 2 files changed, 41 insertions(+), 6 deletions(-) diff --git a/crypto/drbg.c b/crypto/drbg.c index 2b2738e..1224c0c 100644 --- a/crypto/drbg.c +++ b/crypto/drbg.c @@ -1104,10 +1104,25 @@ static int drbg_seed(struct drbg_state *drbg, struct drbg_string *pers, drbg->test_data.len); pr_devel("DRBG: using test entropy\n"); } else { - pr_devel("DRBG: (re)seeding with %zu bytes of entropy\n", - drbg->seed_buf_len); + /* Get seed from in-kernel /dev/urandom */ get_random_bytes(drbg->seed_buf, drbg->seed_buf_len); - drbg_string_fill(&data1, drbg->seed_buf, drbg->seed_buf_len); + + /* Get seed from Jitter RNG */ + if (!drbg->jent || + crypto_rng_get_bytes(drbg->jent, + drbg->seed_buf + drbg->seed_buf_len, + drbg->seed_buf_len)) { + pr_info("DRBG: could not obtain random data from Jitter RNG\n"); + drbg_string_fill(&data1, drbg->seed_buf, + drbg->seed_buf_len); + pr_devel("DRBG: (re)seeding with %zu bytes of entropy\n", + drbg->seed_buf_len); + } else { + drbg_string_fill(&data1, drbg->seed_buf, + drbg->seed_buf_len * 2); + pr_devel("DRBG: (re)seeding with %zu bytes of entropy\n", + drbg->seed_buf_len * 2); + } } list_add_tail(&data1.list, &seedlist); @@ -1132,7 +1147,7 @@ static int drbg_seed(struct drbg_state *drbg, struct drbg_string *pers, * Clear the initial entropy buffer as the async call may not overwrite * that buffer for quite some time. */ - memzero_explicit(drbg->seed_buf, drbg->seed_buf_len); + memzero_explicit(drbg->seed_buf, drbg->seed_buf_len * 2); if (ret) goto out; /* @@ -1173,6 +1188,10 @@ static inline void drbg_dealloc_state(struct drbg_state *drbg) #endif kzfree(drbg->seed_buf); drbg->seed_buf = NULL; + if (drbg->jent) { + crypto_free_rng(drbg->jent); + drbg->jent = NULL; + } } /* @@ -1248,14 +1267,29 @@ static inline int drbg_alloc_state(struct drbg_state *drbg) ret = -EFAULT; goto err; } - /* ensure we have sufficient buffer space for initial seed */ + /* + * Ensure we have sufficient buffer space for initial seed which + * consists of the seed from get_random_bytes and the Jitter RNG. + */ drbg->seed_buf_len = ((drbg->seed_buf_len + 1) / 2) * 3; - drbg->seed_buf = kzalloc(drbg->seed_buf_len, GFP_KERNEL); + drbg->seed_buf = kzalloc(drbg->seed_buf_len * 2, GFP_KERNEL); if (!drbg->seed_buf) goto err; INIT_WORK(&drbg->seed_work, drbg_async_seed); + drbg->jent = crypto_alloc_rng("jitterentropy_rng", 0, 0); + if(IS_ERR(drbg->jent)) + { + pr_info("DRBG: could not allocate Jitter RNG handle for seeding\n"); + /* + * As the Jitter RNG is a module that may not be present, we + * continue with the operation and do not fully tie the DRBG + * to the Jitter RNG. + */ + drbg->jent = NULL; + } + return 0; err: diff --git a/include/crypto/drbg.h b/include/crypto/drbg.h index 46994b2..c3f208d 100644 --- a/include/crypto/drbg.h +++ b/include/crypto/drbg.h @@ -123,6 +123,7 @@ struct drbg_state { struct work_struct seed_work; /* asynchronous seeding support */ u8 *seed_buf; /* buffer holding the seed */ size_t seed_buf_len; + struct crypto_rng *jent; const struct drbg_state_ops *d_ops; const struct drbg_core *core; struct drbg_string test_data; -- 2.1.0