From patchwork Fri Apr 15 20:56:43 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Ahmad Fatoum X-Patchwork-Id: 12815305 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A63E0C433F5 for ; Fri, 15 Apr 2022 20:58:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353178AbiDOVAg (ORCPT ); Fri, 15 Apr 2022 17:00:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58170 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352922AbiDOVAf (ORCPT ); Fri, 15 Apr 2022 17:00:35 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 844228AE5C for ; Fri, 15 Apr 2022 13:57:50 -0700 (PDT) Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1nfT0A-0002iG-Vn; Fri, 15 Apr 2022 22:57:11 +0200 Received: from [2a0a:edc0:0:1101:1d::ac] (helo=dude04.red.stw.pengutronix.de) by drehscheibe.grey.stw.pengutronix.de with esmtp (Exim 4.94.2) (envelope-from ) id 1nfT0A-003FIr-9q; Fri, 15 Apr 2022 22:57:08 +0200 Received: from afa by dude04.red.stw.pengutronix.de with local (Exim 4.94.2) (envelope-from ) id 1nfT07-000C07-Fa; Fri, 15 Apr 2022 22:57:07 +0200 From: Ahmad Fatoum To: James Bottomley , Jarkko Sakkinen , Mimi Zohar , David Howells Cc: kernel@pengutronix.de, Sumit Garg , Pankaj Gupta , David Gstir , Ahmad Fatoum , James Morris , "Serge E. Hallyn" , =?utf-8?q?Horia_Geant=C4=83?= , Herbert Xu , "David S. Miller" , Jan Luebbe , Eric Biggers , Richard Weinberger , Franck LENORMAND , Matthias Schiffer , keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org Subject: [PATCH v7 2/6] KEYS: trusted: allow use of kernel RNG for key material Date: Fri, 15 Apr 2022 22:56:43 +0200 Message-Id: <20220415205647.46056-3-a.fatoum@pengutronix.de> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220415205647.46056-1-a.fatoum@pengutronix.de> References: <20220415205647.46056-1-a.fatoum@pengutronix.de> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: afa@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-security-module@vger.kernel.org Precedence: bulk List-ID: The two existing trusted key sources don't make use of the kernel RNG, but instead let the hardware doing the sealing/unsealing also generate the random key material. However, both users and future backends may want to place less trust into the quality of the trust source's random number generator and instead reuse the kernel entropy pool, which can be seeded from multiple entropy sources. Make this possible by adding a new trusted.rng parameter, that will force use of the kernel RNG. In its absence, it's up to the trust source to decide, which random numbers to use, maintaining the existing behavior. Suggested-by: Jarkko Sakkinen Acked-by: Sumit Garg Acked-by: Pankaj Gupta Reviewed-by: David Gstir Reviewed-by: Pankaj Gupta Reviewed-by: Jarkko Sakkinen Signed-off-by: Ahmad Fatoum --- v6 -> v7: - No changes v5 -> v6: - Squash with follow-up patch enabling trust sources to use kernel RNG if they don't define their own .get_random - Collected Jarkko's Reviewed-by v4 -> v5: - Changed trusted.kernel_rng bool option into a string trusted.rng option (Jarkko) - Typo fix in commit message (Jarkko) v3 -> v4: - Collected Acked-by's, Reviewed-by's and Tested-by v2 -> v3: - No change v1 -> v2: - Allow users to force use of kernel RNG (Jarkko) To: James Bottomley To: Jarkko Sakkinen To: Mimi Zohar To: David Howells Cc: James Morris Cc: "Serge E. Hallyn" Cc: "Horia Geantă" Cc: Pankaj Gupta Cc: Herbert Xu Cc: "David S. Miller" Cc: Jan Luebbe Cc: Eric Biggers Cc: David Gstir Cc: Richard Weinberger Cc: Franck LENORMAND Cc: Sumit Garg Cc: Matthias Schiffer Cc: keyrings@vger.kernel.org Cc: linux-crypto@vger.kernel.org Cc: linux-integrity@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-security-module@vger.kernel.org --- .../admin-guide/kernel-parameters.txt | 10 ++++++ .../security/keys/trusted-encrypted.rst | 20 ++++++----- include/keys/trusted-type.h | 2 +- security/keys/trusted-keys/trusted_core.c | 35 ++++++++++++++++++- 4 files changed, 57 insertions(+), 10 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 3f1cc5e317ed..4deed1908a75 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5963,6 +5963,16 @@ first trust source as a backend which is initialized successfully during iteration. + trusted.rng= [KEYS] + Format: + The RNG used to generate key material for trusted keys. + Can be one of: + - "kernel" + - the same value as trusted.source: "tpm" or "tee" + - "default" + If not specified, "default" is used. In this case, + the RNG's choice is left to each individual trust source. + tsc= Disable clocksource stability checks for TSC. Format: [x86] reliable: mark tsc clocksource as reliable, this diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst index f614dad7de12..2fe6fd1a2bbd 100644 --- a/Documentation/security/keys/trusted-encrypted.rst +++ b/Documentation/security/keys/trusted-encrypted.rst @@ -87,22 +87,26 @@ Key Generation Trusted Keys ------------ -New keys are created from random numbers generated in the trust source. They -are encrypted/decrypted using a child key in the storage key hierarchy. -Encryption and decryption of the child key must be protected by a strong -access control policy within the trust source. +New keys are created from random numbers. They are encrypted/decrypted using +a child key in the storage key hierarchy. Encryption and decryption of the +child key must be protected by a strong access control policy within the +trust source. The random number generator in use differs according to the +selected trust source: - * TPM (hardware device) based RNG + * TPM: hardware device based RNG - Strength of random numbers may vary from one device manufacturer to - another. + Keys are generated within the TPM. Strength of random numbers may vary + from one device manufacturer to another. - * TEE (OP-TEE based on Arm TrustZone) based RNG + * TEE: OP-TEE based on Arm TrustZone based RNG RNG is customizable as per platform needs. It can either be direct output from platform specific hardware RNG or a software based Fortuna CSPRNG which can be seeded via multiple entropy sources. +Users may override this by specifying ``trusted.rng=kernel`` on the kernel +command-line to override the used RNG with the kernel's random number pool. + Encrypted Keys -------------- diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h index d89fa2579ac0..4eb64548a74f 100644 --- a/include/keys/trusted-type.h +++ b/include/keys/trusted-type.h @@ -64,7 +64,7 @@ struct trusted_key_ops { /* Unseal a key. */ int (*unseal)(struct trusted_key_payload *p, char *datablob); - /* Get a randomized key. */ + /* Optional: Get a randomized key. */ int (*get_random)(unsigned char *key, size_t key_len); /* Exit key interface. */ diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c index 7cdbd16aed30..9235fb7d0ec9 100644 --- a/security/keys/trusted-keys/trusted_core.c +++ b/security/keys/trusted-keys/trusted_core.c @@ -16,12 +16,17 @@ #include #include #include +#include #include #include #include #include #include +static char *trusted_rng = "default"; +module_param_named(rng, trusted_rng, charp, 0); +MODULE_PARM_DESC(rng, "Select trusted key RNG"); + static char *trusted_key_source; module_param_named(source, trusted_key_source, charp, 0); MODULE_PARM_DESC(source, "Select trusted keys source (tpm or tee)"); @@ -312,8 +317,14 @@ struct key_type key_type_trusted = { }; EXPORT_SYMBOL_GPL(key_type_trusted); +static int kernel_get_random(unsigned char *key, size_t key_len) +{ + return get_random_bytes_wait(key, key_len) ?: key_len; +} + static int __init init_trusted(void) { + int (*get_random)(unsigned char *key, size_t key_len); int i, ret = 0; for (i = 0; i < ARRAY_SIZE(trusted_key_sources); i++) { @@ -322,6 +333,28 @@ static int __init init_trusted(void) strlen(trusted_key_sources[i].name))) continue; + /* + * We always support trusted.rng="kernel" and "default" as + * well as trusted.rng=$trusted.source if the trust source + * defines its own get_random callback. + */ + get_random = trusted_key_sources[i].ops->get_random; + if (trusted_rng && strcmp(trusted_rng, "default")) { + if (!strcmp(trusted_rng, "kernel")) { + get_random = kernel_get_random; + } else if (strcmp(trusted_rng, trusted_key_sources[i].name) || + !get_random) { + pr_warn("Unsupported RNG. Supported: kernel"); + if (get_random) + pr_cont(", %s", trusted_key_sources[i].name); + pr_cont(", default\n"); + return -EINVAL; + } + } + + if (!get_random) + get_random = kernel_get_random; + static_call_update(trusted_key_init, trusted_key_sources[i].ops->init); static_call_update(trusted_key_seal, @@ -329,7 +362,7 @@ static int __init init_trusted(void) static_call_update(trusted_key_unseal, trusted_key_sources[i].ops->unseal); static_call_update(trusted_key_get_random, - trusted_key_sources[i].ops->get_random); + get_random); static_call_update(trusted_key_exit, trusted_key_sources[i].ops->exit); migratable = trusted_key_sources[i].ops->migratable;