From patchwork Wed Jul 14 05:45:22 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stephan Mueller X-Patchwork-Id: 477571 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 529DBC07E9C for ; Wed, 14 Jul 2021 05:52:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3B05F613BF for ; Wed, 14 Jul 2021 05:52:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238049AbhGNFzP (ORCPT ); Wed, 14 Jul 2021 01:55:15 -0400 Received: from mo4-p04-ob.smtp.rzone.de ([85.215.255.121]:33704 "EHLO mo4-p04-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237960AbhGNFzA (ORCPT ); Wed, 14 Jul 2021 01:55:00 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; t=1626241858; s=strato-dkim-0002; d=chronox.de; h=References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From:Cc:Date: From:Subject:Sender; bh=X378qQdSxBYvlYM61lwkLudIP+ZUjtLb2NOspEk7d2s=; b=I7RjSIzowu7APpSru6OJtWG2xO9liO8KQlDhVKbSnq8iip83dzjilGlEPRhlAhvmmN 8mH1SdHWD/YUQxlXSH0Su60p1lOG7TwwEqZ15XFMwsa9ZY+6yYA3eUzYRdwbZmAKF7e0 kELKInTU73CYTZZvJbZvvWtv01iUfs82acumGZf66id3pZzmGMfdebdcKwG6kEp34rFw GDMdLjr+g9vd17MOcQGI2SaOPdb4tDUwagw6rWWvQJhcNy0zx6NOdDEXL432QaZFkSCI 34z6FIUyM5oQNjOdmx9g8XHkSpcnJczzvtCdZCZUdbOSgcSU+FdhicUKo2Svuzm3o3U3 DWIA== Authentication-Results: strato.com; dkim=none X-RZG-AUTH: ":P2ERcEykfu11Y98lp/T7+hdri+uKZK8TKWEqNyiHySGSa9k9xmwdNnzHHXPSI/SaRQ==" X-RZG-CLASS-ID: mo00 Received: from positron.chronox.de by smtp.strato.de (RZmta 47.28.1 DYNA|AUTH) with ESMTPSA id N0753fx6E5ovwyb (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256 bits)) (Client did not present a certificate); Wed, 14 Jul 2021 07:50:57 +0200 (CEST) From: Stephan =?iso-8859-1?q?M=FCller?= To: Tso Ted , linux-crypto@vger.kernel.org Cc: Willy Tarreau , Nicolai Stange , LKML , Arnd Bergmann , Greg Kroah-Hartman , "Eric W. Biederman" , "Alexander E. Patrakov" , "Ahmed S. Darwish" , Matthew Garrett , Vito Caputo , Andreas Dilger , Jan Kara , Ray Strode , William Jon McCann , zhangjs , Andy Lutomirski , Florian Weimer , Lennart Poettering , Peter Matthias , Marcelo Henrique Cerri , Neil Horman , Randy Dunlap , Julia Lawall , Dan Carpenter , Andy Lavr , Eric Biggers , "Jason A. Donenfeld" , Petr Tesarik , John Haxby , Alexander Lobakin Subject: [PATCH v41 04/13] LRNG - add switchable DRNG support Date: Wed, 14 Jul 2021 07:45:22 +0200 Message-ID: <5750762.BcOUJiyQPM@positron.chronox.de> In-Reply-To: <7822794.ITf6fX9eNu@positron.chronox.de> References: <7822794.ITf6fX9eNu@positron.chronox.de> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org The DRNG switch support allows replacing the DRNG mechanism of the LRNG. The switching support rests on the interface definition of include/linux/lrng.h. A new DRNG is implemented by filling in the interface defined in this header file. In addition to the DRNG, the extension also has to provide a hash implementation that is used to hash the entropy pool for random number extraction. Note: It is permissible to implement a DRNG whose operations may sleep. However, the hash function must not sleep. The switchable DRNG support allows replacing the DRNG at runtime. However, only one DRNG extension is allowed to be loaded at any given time. Before replacing it with another DRNG implementation, the possibly existing DRNG extension must be unloaded. The switchable DRNG extension activates the new DRNG during load time. It is expected, however, that such a DRNG switch would be done only once by an administrator to load the intended DRNG implementation. It is permissible to compile DRNG extensions either as kernel modules or statically. The initialization of the DRNG extension should be performed with a late_initcall to ensure the extension is available when user space starts but after all other initialization completed. The initialization is performed by registering the function call data structure with the lrng_set_drng_cb function. In order to unload the DRNG extension, lrng_set_drng_cb must be invoked with the NULL parameter. The DRNG extension should always provide a security strength that is at least as strong as LRNG_DRNG_SECURITY_STRENGTH_BITS. The hash extension must not sleep and must not maintain a separate state. CC: Torsten Duwe CC: "Eric W. Biederman" CC: "Alexander E. Patrakov" CC: "Ahmed S. Darwish" CC: "Theodore Y. Ts'o" CC: Willy Tarreau CC: Matthew Garrett CC: Vito Caputo CC: Andreas Dilger CC: Jan Kara CC: Ray Strode CC: William Jon McCann CC: zhangjs CC: Andy Lutomirski CC: Florian Weimer CC: Lennart Poettering CC: Nicolai Stange CC: Alexander Lobakin Reviewed-by: Marcelo Henrique Cerri Reviewed-by: Roman Drahtmueller Tested-by: Marcelo Henrique Cerri Tested-by: Neil Horman Signed-off-by: Stephan Mueller --- drivers/char/lrng/Kconfig | 7 + drivers/char/lrng/Makefile | 1 + drivers/char/lrng/lrng_switch.c | 231 ++++++++++++++++++++++++++++++++ 3 files changed, 239 insertions(+) create mode 100644 drivers/char/lrng/lrng_switch.c diff --git a/drivers/char/lrng/Kconfig b/drivers/char/lrng/Kconfig index 1cb2f55666ac..c10a0c3f2015 100644 --- a/drivers/char/lrng/Kconfig +++ b/drivers/char/lrng/Kconfig @@ -202,4 +202,11 @@ config LRNG_CPU_ENTROPY_RATE endmenu # "Entropy Source Configuration" +menuconfig LRNG_DRNG_SWITCH + bool "Support DRNG runtime switching" + help + The Linux RNG per default uses a ChaCha20 DRNG that is + accessible via the external interfaces. With this configuration + option other DRNGs can be selected and loaded at runtime. + endif # LRNG diff --git a/drivers/char/lrng/Makefile b/drivers/char/lrng/Makefile index ac97f0b11cb7..0eb4a6849c88 100644 --- a/drivers/char/lrng/Makefile +++ b/drivers/char/lrng/Makefile @@ -10,3 +10,4 @@ obj-y += lrng_pool.o lrng_aux.o \ obj-$(CONFIG_NUMA) += lrng_numa.o obj-$(CONFIG_SYSCTL) += lrng_proc.o +obj-$(CONFIG_LRNG_DRNG_SWITCH) += lrng_switch.o diff --git a/drivers/char/lrng/lrng_switch.c b/drivers/char/lrng/lrng_switch.c new file mode 100644 index 000000000000..23390674012b --- /dev/null +++ b/drivers/char/lrng/lrng_switch.c @@ -0,0 +1,231 @@ +// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause +/* + * LRNG DRNG switching support + * + * Copyright (C) 2016 - 2021, Stephan Mueller + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include + +#include "lrng_internal.h" + +static int lrng_drng_switch(struct lrng_drng *drng_store, + const struct lrng_crypto_cb *cb, int node) +{ + const struct lrng_crypto_cb *old_cb; + unsigned long flags = 0, flags2 = 0; + int ret; + u8 seed[LRNG_DRNG_SECURITY_STRENGTH_BYTES]; + void *new_drng = cb->lrng_drng_alloc(LRNG_DRNG_SECURITY_STRENGTH_BYTES); + void *old_drng, *new_hash, *old_hash; + u32 current_security_strength; + bool sl = false, reset_drng = !lrng_get_available(); + + if (IS_ERR(new_drng)) { + pr_warn("could not allocate new DRNG for NUMA node %d (%ld)\n", + node, PTR_ERR(new_drng)); + return PTR_ERR(new_drng); + } + + new_hash = cb->lrng_hash_alloc(); + if (IS_ERR(new_hash)) { + pr_warn("could not allocate new LRNG pool hash (%ld)\n", + PTR_ERR(new_hash)); + cb->lrng_drng_dealloc(new_drng); + return PTR_ERR(new_hash); + } + + if (cb->lrng_hash_digestsize(new_hash) > LRNG_MAX_DIGESTSIZE) { + pr_warn("digest size of newly requested hash too large\n"); + cb->lrng_hash_dealloc(new_hash); + cb->lrng_drng_dealloc(new_drng); + return -EINVAL; + } + + current_security_strength = lrng_security_strength(); + lrng_drng_lock(drng_store, &flags); + + /* + * Pull from existing DRNG to seed new DRNG regardless of seed status + * of old DRNG -- the entropy state for the DRNG is left unchanged which + * implies that als the new DRNG is reseeded when deemed necessary. This + * seeding of the new DRNG shall only ensure that the new DRNG has the + * same entropy as the old DRNG. + */ + ret = drng_store->crypto_cb->lrng_drng_generate_helper( + drng_store->drng, seed, sizeof(seed)); + lrng_drng_unlock(drng_store, &flags); + + if (ret < 0) { + reset_drng = true; + pr_warn("getting random data from DRNG failed for NUMA node %d (%d)\n", + node, ret); + } else { + /* seed new DRNG with data */ + ret = cb->lrng_drng_seed_helper(new_drng, seed, ret); + memzero_explicit(seed, sizeof(seed)); + if (ret < 0) { + reset_drng = true; + pr_warn("seeding of new DRNG failed for NUMA node %d (%d)\n", + node, ret); + } else { + pr_debug("seeded new DRNG of NUMA node %d instance from old DRNG instance\n", + node); + } + } + + mutex_lock(&drng_store->lock); + write_lock_irqsave(&drng_store->hash_lock, flags2); + /* + * If we switch the DRNG from the initial ChaCha20 DRNG to something + * else, there is a lock transition from spin lock to mutex (see + * lrng_drng_is_atomic and how the lock is taken in lrng_drng_lock). + * Thus, we need to take both locks during the transition phase. + */ + if (lrng_drng_is_atomic(drng_store)) { + spin_lock_irqsave(&drng_store->spin_lock, flags); + sl = true; + } else { + __acquire(&drng_store->spin_lock); + } + + /* Trigger the switch of the aux entropy pool for current node. */ + if (drng_store == lrng_drng_init_instance()) { + ret = lrng_aux_switch_hash(cb, new_hash, drng_store->crypto_cb); + if (ret) + goto err; + } + + /* Trigger the switch of the per-CPU entropy pools for current node. */ + ret = lrng_pcpu_switch_hash(node, cb, new_hash, drng_store->crypto_cb); + if (ret) { + /* Switch the crypto operation back to be consistent */ + WARN_ON(lrng_aux_switch_hash(drng_store->crypto_cb, + drng_store->hash, cb)); + } else { + if (reset_drng) + lrng_drng_reset(drng_store); + + old_drng = drng_store->drng; + old_cb = drng_store->crypto_cb; + drng_store->drng = new_drng; + drng_store->crypto_cb = cb; + + old_hash = drng_store->hash; + drng_store->hash = new_hash; + pr_info("Entropy pool read-hash allocated for DRNG for NUMA node %d\n", + node); + + if (lrng_state_min_seeded()) + lrng_set_entropy_thresh(lrng_get_seed_entropy_osr()); + + /* Reseed if previous LRNG security strength was insufficient */ + if (current_security_strength < lrng_security_strength()) + drng_store->force_reseed = true; + + /* Force oversampling seeding as we initialize DRNG */ + if (IS_ENABLED(CONFIG_LRNG_OVERSAMPLE_ENTROPY_SOURCES)) { + drng_store->force_reseed = true; + drng_store->fully_seeded = false; + + /* Block output interfaces until again fully seeded */ + if (drng_store == lrng_drng_init_instance()) + lrng_unset_operational(); + } + + /* ChaCha20 serves as atomic instance left untouched. */ + if (old_drng != &chacha20) { + old_cb->lrng_drng_dealloc(old_drng); + old_cb->lrng_hash_dealloc(old_hash); + } + + pr_info("DRNG of NUMA node %d switched\n", node); + } + +err: + if (sl) + spin_unlock_irqrestore(&drng_store->spin_lock, flags); + else + __release(&drng_store->spin_lock); + write_unlock_irqrestore(&drng_store->hash_lock, flags2); + mutex_unlock(&drng_store->lock); + + return ret; +} + +/* + * Switch the existing DRNG instances with new using the new crypto callbacks. + * The caller must hold the lrng_crypto_cb_update lock. + */ +static int lrng_drngs_switch(const struct lrng_crypto_cb *cb) +{ + struct lrng_drng **lrng_drng = lrng_drng_instances(); + struct lrng_drng *lrng_drng_init = lrng_drng_init_instance(); + int ret = 0; + + /* Update DRNG */ + if (lrng_drng) { + u32 node; + + for_each_online_node(node) { + if (lrng_drng[node]) + ret = lrng_drng_switch(lrng_drng[node], cb, + node); + } + } else { + ret = lrng_drng_switch(lrng_drng_init, cb, 0); + } + + if (!ret) + lrng_set_available(); + + return 0; +} + +/** + * lrng_set_drng_cb - Register new cryptographic callback functions for DRNG + * The registering implies that all old DRNG states are replaced with new + * DRNG states. + * + * @cb: Callback functions to be registered -- if NULL, use the default + * callbacks pointing to the ChaCha20 DRNG. + * + * Return: + * * 0 on success + * * < 0 on error + */ +int lrng_set_drng_cb(const struct lrng_crypto_cb *cb) +{ + struct lrng_drng *lrng_drng_init = lrng_drng_init_instance(); + int ret; + + if (!cb) + cb = &lrng_cc20_crypto_cb; + + mutex_lock(&lrng_crypto_cb_update); + + /* + * If a callback other than the default is set, allow it only to be + * set back to the default callback. This ensures that multiple + * different callbacks can be registered at the same time. If a + * callback different from the current callback and the default + * callback shall be set, the current callback must be deregistered + * (e.g. the kernel module providing it must be unloaded) and the new + * implementation can be registered. + */ + if ((cb != &lrng_cc20_crypto_cb) && + (lrng_drng_init->crypto_cb != &lrng_cc20_crypto_cb)) { + pr_warn("disallow setting new cipher callbacks, unload the old callbacks first!\n"); + ret = -EINVAL; + goto out; + } + + ret = lrng_drngs_switch(cb); + +out: + mutex_unlock(&lrng_crypto_cb_update); + return ret; +} +EXPORT_SYMBOL(lrng_set_drng_cb);