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Thu, 21 Sep 2023 13:49:57 +0200 (CEST) From: Stephan =?iso-8859-1?q?M=FCller?= To: herbert@gondor.apana.org.au Cc: linux-crypto@vger.kernel.org, "Ospan, Abylay" Subject: [PATCH 3/3] crypto: jitter - Allow configuration of oversampling rate Date: Thu, 21 Sep 2023 13:48:59 +0200 Message-ID: <4835498.GXAFRqVoOG@positron.chronox.de> In-Reply-To: <2700818.mvXUDI8C0e@positron.chronox.de> References: <2700818.mvXUDI8C0e@positron.chronox.de> MIME-Version: 1.0 Autocrypt: addr=smueller@chronox.de; keydata= mQENBFqo+vgBCACp9hezmvJ4eeZv4PkyoMxGpXHN4Ox2+aofXxMv/yQ6oyZ69xu0U0yFcEcSWbe 4qhxB+nlOvSBRJ8ohEU3hlGLrAKJwltHVzeO6nCby/T57b6SITCbcnZGIgKwX4CrJYmfQ4svvMG NDOORPk6SFkK7hhe1cWJb+Gc5czw3wy7By5c1OtlnbmGB4k5+p7Mbi+rui/vLTKv7FKY5t2CpQo OxptxFc/yq9sMdBnsjvhcCHcl1kpnQPTMppztWMj4Nkkd+Trvpym0WZ1px6+3kxhMn6LNYytHTC mf/qyf1+1/PIpyEXvx66hxeN+fN/7R+0iYCisv3JTtfNkCV3QjGdKqT3ABEBAAG0HVN0ZXBoYW4 gTXVlbGxlciA8c21AZXBlcm0uZGU+iQFOBBMBCAA4FiEEO8xD1NLIfReEtp7kQh7pNjJqwVsFAl qo/M8CGwMFCwkIBwIGFQoJCAsCBBYCAwECHgECF4AACgkQQh7pNjJqwVsV8gf+OcAaiSqhn0mYk fC7Fe48n9InAkHiSQ/T7eN+wWYLYMWGG0N2z5gBnNfdc4oFVL+ngye4C3bm98Iu7WnSl0CTOe1p KGFJg3Y7YzSa5/FzS9nKsg6iXpNWL5nSYyz8T9Q0KGKNlAiyQEGkt8y05m8hNsvqkgDb923/RFf UYX4mTUXJ1vk/6SFCA/72JQN7PpwMgGir7FNybuuDUuDLDgQ+BZHhJlW91XE2nwxUo9IrJ2FeT8 GgFKzX8A//peRZTSSeatJBr0HRKfTrKYw3lf897sddUjyQU1nDYv9EMLBvkzuE+gwUakt2rOcpR +4Fn5jkQbN4vpfGPnybMAMMxW6GIrQfU3RlcGhhbiBNdWVsbGVyIDxzbUBjaHJvbm94LmRlPokB TgQTAQgAOBYhBDvMQ9TSyH0XhLae5EIe6TYyasFbBQJaqPzEAhsDBQsJCAcCBhUKCQgLAgQWAgM BAh4BAheAAAoJEEIe6TYyasFbsqUH/2euuyRj8b1xuapmrNUuU4atn9FN6XE1cGzXYPHNEUGBiM kInPwZ/PFurrni7S22cMN+IuqmQzLo40izSjXhRJAa165GoJSrtf7S6iwry/k1S9nY2Vc/dxW6q nFq7mJLAs0JWHOfhRe1caMb7P95B+O5B35023zYr9ApdQ4+Lyk+xx1+i++EOxbTJVqLZEF1EGmO Wh3ERcGyT05+1LQ84yDSCUxZVZFrbA2Mtg8cdyvu68urvKiOCHzDH/xRRhFxUz0+dCOGBFSgSfK I9cgS009BdH3Zyg795QV6wfhNas4PaNPN5ArMAvgPH1BxtkgyMjUSyLQQDrmuqHnLzExEQfG0JV N0ZXBoYW4gTXVlbGxlciA8c211ZWxsZXJAY2hyb25veC5kZT6JAU4EEwEIADgWIQQ7zEPU0sh9F 4S2nuRCHuk2MmrBWwUCWqj6+AIbAwULCQgHAgYVCgkICwIEFgIDAQIeAQIXgAAKCRBCHuk2MmrB WxVrB/wKYSuURgwKs2pJ2kmLIp34StoreNqe6cdIF7f7e8o7NaT528hFAVuDSTUyjXO+idbC0P+ zu9y2SZfQhc4xbD+Zf0QngX7/sqIWVeiXJa6uR/qrtJF7OBEvlGkxcAwkC0d/Ts68ps4QbZ7s5q WBJJY4LmnytqvXGb63/fOTwImYiY3tKCOSCM2YQRFt6BO71t8tu/4NLk0KSW9OHa9nfcDqI18aV ylGMu5zNjYqjJpT/be1UpyZo6I/7p0yAQfGJ5YBiN4S264mdFN7jOvxZE3NKXhL4QMt34hOSWPO pW8ZGEo1hKjEdHFvYowPpcoOFicP+zvxdpMtUTEkppREN2a+uQENBFqo+vgBCACiLHsDAX7C0l0 sB8DhVvTDpC2CyaeuNW9GZ1Qqkenh3Y5KnYnh5Gg5b0jubSkauJ75YEOsOeClWuebL3i76kARC8 Gfo727wSLvfIAcWhO1ws6j1Utc8s1HNO0+vcGC9EEkn7LzO5piEUPkentjrSF7clPsXziW4IJq/ z3DYZQkVPk7PSw6r0jXWR/p6sj4aXxslIiDgFJZyopki7Sl2805JYcvKKC6OWTyPHJMlnu9dNxJ viAentAUwzHxNqmvYjlkqBr/sFnjC9kydElecVm4YQh3TC6yt5h49AslAVlFYfwQwcio1LNWySc lWHbDZhcVZJZZi4++gpFmmg1AjyfLABEBAAGJATYEGAEIACAWIQQ7zEPU0sh9F4S2nuRCHuk2Mm rBWwUCWqj6+AIbIAAKCRBCHuk2MmrBWxPCCACQGQu5eOcH9qsqSOO64n+xUX7PG96S8s2JolN3F t2YWKUzjVHLu5jxznmDwx+GJ3P7thrzW+V5XdDcXgSAXW793TaJ/XMM0jEG+jgvuhE65JfWCK+8 sumrO24M1KnVQigxrMpG5FT7ndpBRGbs059QSqoMVN4x2dvaP81/+u0sQQ2EGrhPFB2aOA3s7bb Wy8xGVIPLcCqByPLbxbHzaU/dkiutSaYqmzdgrTdcuESSbK4qEv3g1i2Bw5kdqeY9mM96SUL8cG UokqFtVP7b2mSfm51iNqlO3nsfwpRnl/IlRPThWLhM7/qr49GdWYfQsK4hbw0fo09QFCXN53MPL hLwuQENBFqo+vgBCAClaPqyK/PUbf7wxTfu3ZBAgaszL98Uf1UHTekRNdYO7FP1dWWT4SebIgL8 wwtWZEqI1pydyvk6DoNF6CfRFq1lCo9QA4Rms7Qx3cdXu1G47ZtQvOqxvO4SPvi7lg3PgnuiHDU STwo5a8+ojxbLzs5xExbx4RDGtykBoaOoLYeenn92AQ//gN6wCDjEjwP2u39xkWXlokZGrwn3yt FE20rUTNCSLxdmoCr1faHzKmvql95wmA7ahg5s2vM9/95W4G71lJhy2crkZIAH0fx3iOUbDmlZ3 T3UvoLuyMToUyaQv5lo0lV2KJOBGhjnAfmykHsxQu0RygiNwvO3TGjpaeB5ABEBAAGJATYEGAEI ACAWIQQ7zEPU0sh9F4S2nuRCHuk2MmrBWwUCWqj6+AIbDAAKCRBCHuk2MmrBW5Y4B/oCLcRZyN0 ETep2JK5CplZHHRN27DhL4KfnahZv872vq3c83hXDDIkCm/0/uDElso+cavceg5pIsoP2bvEeSJ jGMJ5PVdCYOx6r/Fv/tkr46muOvaLdgnphv/CIA+IRykwyzXe3bsucHC4a1fnSoTMnV1XhsIh8z WTINVVO8+qdNEv3ix2nP5yArexUGzmJV0HIkKm59wCLz4FpWR+QZru0i8kJNuFrdnDIP0wxDjiV BifPhiegBv+/z2DOj8D9EI48KagdQP7MY7q/u1n3+pGTwa+F1hoGo5IOU5MnwVv7UHiW1MSNQ2/ kBFBHm+xdudNab2U0OpfqrWerOw3WcGd2 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org The oversampling rate used by the Jitter RNG allows the configuration of the heuristically implied entropy in one timing measurement. This entropy rate is (1 / OSR) bits of entropy per time stamp. Considering that the Jitter RNG now support APT/RCT health tests for different OSRs, allow this value to be configured at compile time to support systems with limited amount of entropy in their timer. The allowed range of OSR values complies with the APT/RCT cutoff health test values which range from 1 through 15. The default value of the OSR selection support is left at 1 which is the current default. Thus, the addition of the configuration support does not alter the default Jitter RNG behavior. Signed-off-by: Stephan Mueller --- crypto/Kconfig | 17 +++++++++++++++++ crypto/jitterentropy-kcapi.c | 6 ++++-- 2 files changed, 21 insertions(+), 2 deletions(-) diff --git a/crypto/Kconfig b/crypto/Kconfig index 00c827d9f0d2..ed931ddea644 100644 --- a/crypto/Kconfig +++ b/crypto/Kconfig @@ -1339,6 +1339,23 @@ config CRYPTO_JITTERENTROPY_MEMORY_BLOCKSIZE default 1024 if CRYPTO_JITTERENTROPY_MEMSIZE_1024 default 2048 if CRYPTO_JITTERENTROPY_MEMSIZE_8192 +config CRYPTO_JITTERENTROPY_OSR + int "CPU Jitter RNG Oversampling Rate" + range 1 15 + default 1 + depends on CRYPTO_JITTERENTROPY + help + The Jitter RNG allows the specification of an oversampling rate (OSR). + The Jitter RNG operation requires a fixed amount of timing + measurements to produce one output block of random numbers. The + OSR value is multiplied with the amount of timing measurements to + generate one output block. Thus, the timing measurement is oversampled + by the OSR factor. The oversampling allows the Jitter RNG to operate + on hardware whose timers deliver limited amount of entropy (e.g. + the timer is coarse) by setting the OSR to a higher value. The + trade-off, however, is that the Jitter RNG now requires more time + to generate random numbers. + config CRYPTO_JITTERENTROPY_TESTINTERFACE bool "CPU Jitter RNG Test Interface" depends on CRYPTO_JITTERENTROPY diff --git a/crypto/jitterentropy-kcapi.c b/crypto/jitterentropy-kcapi.c index a8e7bbd28c6e..0c6752221451 100644 --- a/crypto/jitterentropy-kcapi.c +++ b/crypto/jitterentropy-kcapi.c @@ -256,7 +256,9 @@ static int jent_kcapi_init(struct crypto_tfm *tfm) crypto_shash_init(sdesc); rng->sdesc = sdesc; - rng->entropy_collector = jent_entropy_collector_alloc(0, 0, sdesc); + rng->entropy_collector = + jent_entropy_collector_alloc(CONFIG_CRYPTO_JITTERENTROPY_OSR, 0, + sdesc); if (!rng->entropy_collector) { ret = -ENOMEM; goto err; @@ -345,7 +347,7 @@ static int __init jent_mod_init(void) desc->tfm = tfm; crypto_shash_init(desc); - ret = jent_entropy_init(0, 0, desc); + ret = jent_entropy_init(CONFIG_CRYPTO_JITTERENTROPY_OSR, 0, desc); shash_desc_zero(desc); crypto_free_shash(tfm); if (ret) {