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Miller" , Kukjin Kim , linux-crypto@vger.kernel.org, linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org Cc: =?UTF-8?q?=C5=81ukasz=20Stelmach?= , m.szyprowski@samsung.com, b.zolnierkie@samsung.com Subject: [PATCH 3/3] crypto: exynos - Reseed PRNG after generating 2^16 random bytes Date: Tue, 05 Dec 2017 13:35:58 +0100 Message-id: <20171205123558.31087-4-l.stelmach@samsung.com> X-Mailer: git-send-email 2.11.0 In-reply-to: <20171205123558.31087-1-l.stelmach@samsung.com> Organization: Samsung R&D Institute Poland X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrDKsWRmVeSWpSXmKPExsWy7djPc7pbJqlFGTx/J2WxccZ6Vos551tY LLpfyVj0P37NbHH+/AZ2i5uHVjBa3L/3k8ni8q45bBYzzu9jslh75C67ReveI+wWU0+vZXHg 8fh05QqTx5aVN5k8th1Q9di0qpPNo2/LKkaPz5vkAtiiuGxSUnMyy1KL9O0SuDI2bvjOWrBT sGLlrF2MDYy/ebsYOTkkBEwkGl/PYoGwxSQu3FvP1sXIxSEksJRR4v+zbYwQzmdGid8bpzB1 MXKAdZx54QARX8YoceFqExNIN6+AoMSPyfdYQGqYBeQljlzKBgkzC2hKbN29nh2i/gujxN5P /8C2sQk4SvQvPcEKkhAR2Msk8ebsXhaIjlKJs/NuM4MMEhYIkzjVnQMSZhFQlbh1vQ1ql7XE 7yNLmSCulpfY1XaRFcTmFLCRWHh2BhuIzS+gJbGm6ToLyHwJgf9sEm0nL0E1uEh8mzqLEcIW lnh1fAs7hC0j0dlxkAmioZ9R4vD871CJKYwSixc6QNjWEn9WTWSDOJRPYtK26cyQUOGV6GgT gijxkGh/+pMNwnaUeHl/CQvE90AzZz5rY5rAKD8LKcBmIQJsFlKALWBkXsUoklpanJueWmys V5yYW1yal66XnJ+7iRGYhk7/O/5pB+PXE1aHGAU4GJV4eBu8VaOEWBPLiitzDzFKcDArifAy 96tFCfGmJFZWpRblxxeV5qQWH2KU5mBREue1jWqLFBJITyxJzU5NLUgtgskycXBKNTAyJq58 7DX3kIF4jo2l26nQgHuzMowFdXL8TXrYriyf27ku+yr3Lr6tSu1NEW8fuW/jiNSzZ+40vDzJ WLijW8ljs6G7+8SDB1gzZ51cEn6m6+7upR0fXsVrsWQp7xf9//Xr9+MF8iuVv1w58desSrio 4OJZ7ZZ13JeVFjlennCypE539RPD3i4lluKMREMt5qLiRACEQMiwPwMAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrPLMWRmVeSWpSXmKPExsVy+t/xq7qbJ6lFGax+bG2xccZ6Vos551tY LLpfyVj0P37NbHH+/AZ2i5uHVjBa3L/3k8ni8q45bBYzzu9jslh75C67ReveI+wWU0+vZXHg 8fh05QqTx5aVN5k8th1Q9di0qpPNo2/LKkaPz5vkAtiiuGxSUnMyy1KL9O0SuDI2bvjOWrBT sGLlrF2MDYy/ebsYOTgkBEwkzrxw6GLkBDLFJC7cW8/WxcjFISSwhFHi1cUFTCAJXgFBiR+T 77GA1DMLyEscuZQNEmYWUJeYNG8RM4gtJPCNUWL7YysQm03AUaJ/6QlWkDkiAvuZJF6c+MQI 0VAq0T/zBRuILSwQJtF3aQNYM4uAqsSt621Qu6wlfh9ZygRxkLzErraLrCA2p4CNxMKzM9hA bhACqjk9ORokzC+gJbGm6TrLBEbBWUgunYVw6Swkly5gZF7FKJJaWpybnltsqFecmFtcmpeu l5yfu4kRGC3bjv3cvIPx0sbgQ4wCHIxKPLwN3qpRQqyJZcWVuYcYJTiYlUR4mfvVooR4UxIr q1KL8uOLSnNSiw8xSnOwKInz9u5ZHSkkkJ5YkpqdmlqQWgSTZeLglGpg5HiudDezeIN19p6L K81vzNhxdTl3xZ1mz718fB77hNjK3vpuF6rvPbj0b0xXBEs3g8LEQlG5Q9xbmnVvezdq5Zj9 cp/essaxmmuSyIf7V2bMt5UQZ64RMmtfY/47eE9S+8/YCHW+LWyuNxb23mKQMXiyfF9e3e3i VkvlzrivhhP6jvWV9LsqsRRnJBpqMRcVJwIA+tFgdJICAAA= X-CMS-MailID: 20171205123604eucas1p2a6a2738e3cf1f9c300e8d128362429ed X-Msg-Generator: CA CMS-TYPE: 201P X-CMS-RootMailID: 20171205123604eucas1p2a6a2738e3cf1f9c300e8d128362429ed X-RootMTR: 20171205123604eucas1p2a6a2738e3cf1f9c300e8d128362429ed References: <20171205123558.31087-1-l.stelmach@samsung.com> Sender: linux-crypto-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Reseed PRNG after reading 65 kB of randomness. Although this may reduce performance, in most casese the loss is not noticable. Signed-off-by: Łukasz Stelmach Reviewed-by: Stephan Mueller --- drivers/crypto/exynos-rng.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/drivers/crypto/exynos-rng.c b/drivers/crypto/exynos-rng.c index 002e9d2a83cc..0bf07a655813 100644 --- a/drivers/crypto/exynos-rng.c +++ b/drivers/crypto/exynos-rng.c @@ -54,12 +54,15 @@ enum exynos_prng_type { }; /* - * Driver re-seeds itself with generated random numbers to increase - * the randomness. + * Driver re-seeds itself with generated random numbers to hinder + * backtracking of the original seed. * * Time for next re-seed in ms. */ -#define EXYNOS_RNG_RESEED_TIME 100 +#define EXYNOS_RNG_RESEED_TIME 1000 +#define EXYNOS_RNG_RESEED_BYTES 65536 + + /* * In polling mode, do not wait infinitely for the engine to finish the work. */ @@ -81,6 +84,8 @@ struct exynos_rng_dev { unsigned int seed_save_len; /* Time of last seeding in jiffies */ unsigned long last_seeding; + /* Bytes generated since last seeding */ + unsigned long bytes_seeding; }; static struct exynos_rng_dev *exynos_rng_dev; @@ -125,6 +130,7 @@ static int exynos_rng_set_seed(struct exynos_rng_dev *rng, } rng->last_seeding = jiffies; + rng->bytes_seeding = 0; return 0; } @@ -166,6 +172,8 @@ static int exynos_rng_get_random(struct exynos_rng_dev *rng, memcpy_fromio(dst, rng->mem + EXYNOS_RNG_OUT_BASE, *read); return 0; + + } /* Re-seed itself from time to time */ @@ -177,7 +185,8 @@ static void exynos_rng_reseed(struct exynos_rng_dev *rng) unsigned int read = 0; u8 seed[EXYNOS_RNG_SEED_SIZE]; - if (time_before(now, next_seeding)) + if (time_before(now, next_seeding) && + rng->bytes_seeding < EXYNOS_RNG_RESEED_BYTES) return; if (exynos_rng_get_random(rng, seed, sizeof(seed), &read)) @@ -206,6 +215,7 @@ static int exynos_rng_generate(struct crypto_rng *tfm, dlen -= read; dst += read; + rng->bytes_seeding += read; exynos_rng_reseed(rng); } while (dlen > 0);