From: Stephan Mueller Subject: [PATCH v4 5/6] crypto: drbg - use Jitter RNG to obtain seed Date: Sun, 03 May 2015 17:35:08 +0200 Message-ID: <1825297.SoV8bN8ame@tachyon.chronox.de> References: <1626703.0h1HzJAx4d@tachyon.chronox.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: Paul Bolle , Andreas Steffen , tytso@mit.edu, Sandy Harris , linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org To: herbert@gondor.apana.org.au Return-path: Received: from mail.eperm.de ([89.247.134.16]:34659 "EHLO mail.eperm.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750905AbbECPhy (ORCPT ); Sun, 3 May 2015 11:37:54 -0400 In-Reply-To: <1626703.0h1HzJAx4d@tachyon.chronox.de> Sender: linux-crypto-owner@vger.kernel.org List-ID: 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 693dac4..6e2b272 100644 --- a/crypto/drbg.c +++ b/crypto/drbg.c @@ -1120,10 +1120,25 @@ 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); @@ -1148,7 +1163,7 @@ 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; /* @@ -1190,6 +1205,10 @@ 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; + } } /* @@ -1265,12 +1284,27 @@ 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; + 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 e4980a1..fabf102 100644 --- a/include/crypto/drbg.h +++ b/include/crypto/drbg.h @@ -122,6 +122,7 @@ struct drbg_state { struct random_work 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