From patchwork Mon Jul 12 06:12:53 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 473814 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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, 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, USER_AGENT_GIT 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 20471C11F99 for ; Mon, 12 Jul 2021 07:29:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0EB1C611C2 for ; Mon, 12 Jul 2021 07:29:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344670AbhGLHcA (ORCPT ); Mon, 12 Jul 2021 03:32:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:43378 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345314AbhGLH3n (ORCPT ); Mon, 12 Jul 2021 03:29:43 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id D559D61606; Mon, 12 Jul 2021 07:26:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626074767; bh=JiV23D7s319bQuMgVN3/RSbx9xSUP3/IuO9DjcHrKo4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FteVkYvvVo0pvE1IgGlK/f/PPtYM+J7mwW9+9VnHp0go2sZRgZVBsq7xMHa4xRp64 ICRol6fZb7NURg04otbwKOOLc2H0si63JbjdBpKr0B7DrIb2XZyuXEkQG4HQY43lYv trOopjmmPsbe1m6MzZqeRB6s3z2NQtBb0G49RS+w= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Biggers Subject: [PATCH 5.12 690/700] fscrypt: fix derivation of SipHash keys on big endian CPUs Date: Mon, 12 Jul 2021 08:12:53 +0200 Message-Id: <20210712061049.371634809@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210712060924.797321836@linuxfoundation.org> References: <20210712060924.797321836@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Eric Biggers commit 2fc2b430f559fdf32d5d1dd5ceaa40e12fb77bdf upstream. Typically, the cryptographic APIs that fscrypt uses take keys as byte arrays, which avoids endianness issues. However, siphash_key_t is an exception. It is defined as 'u64 key[2];', i.e. the 128-bit key is expected to be given directly as two 64-bit words in CPU endianness. fscrypt_derive_dirhash_key() and fscrypt_setup_iv_ino_lblk_32_key() forgot to take this into account. Therefore, the SipHash keys used to index encrypted+casefolded directories differ on big endian vs. little endian platforms, as do the SipHash keys used to hash inode numbers for IV_INO_LBLK_32-encrypted directories. This makes such directories non-portable between these platforms. Fix this by always using the little endian order. This is a breaking change for big endian platforms, but this should be fine in practice since these features (encrypt+casefold support, and the IV_INO_LBLK_32 flag) aren't known to actually be used on any big endian platforms yet. Fixes: aa408f835d02 ("fscrypt: derive dirhash key for casefolded directories") Fixes: e3b1078bedd3 ("fscrypt: add support for IV_INO_LBLK_32 policies") Cc: # v5.6+ Link: https://lore.kernel.org/r/20210605075033.54424-1-ebiggers@kernel.org Signed-off-by: Eric Biggers Signed-off-by: Greg Kroah-Hartman --- fs/crypto/keysetup.c | 40 ++++++++++++++++++++++++++++++++-------- 1 file changed, 32 insertions(+), 8 deletions(-) --- a/fs/crypto/keysetup.c +++ b/fs/crypto/keysetup.c @@ -210,15 +210,40 @@ out_unlock: return err; } +/* + * Derive a SipHash key from the given fscrypt master key and the given + * application-specific information string. + * + * Note that the KDF produces a byte array, but the SipHash APIs expect the key + * as a pair of 64-bit words. Therefore, on big endian CPUs we have to do an + * endianness swap in order to get the same results as on little endian CPUs. + */ +static int fscrypt_derive_siphash_key(const struct fscrypt_master_key *mk, + u8 context, const u8 *info, + unsigned int infolen, siphash_key_t *key) +{ + int err; + + err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, context, info, infolen, + (u8 *)key, sizeof(*key)); + if (err) + return err; + + BUILD_BUG_ON(sizeof(*key) != 16); + BUILD_BUG_ON(ARRAY_SIZE(key->key) != 2); + le64_to_cpus(&key->key[0]); + le64_to_cpus(&key->key[1]); + return 0; +} + int fscrypt_derive_dirhash_key(struct fscrypt_info *ci, const struct fscrypt_master_key *mk) { int err; - err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, HKDF_CONTEXT_DIRHASH_KEY, - ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, - (u8 *)&ci->ci_dirhash_key, - sizeof(ci->ci_dirhash_key)); + err = fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_DIRHASH_KEY, + ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, + &ci->ci_dirhash_key); if (err) return err; ci->ci_dirhash_key_initialized = true; @@ -253,10 +278,9 @@ static int fscrypt_setup_iv_ino_lblk_32_ if (mk->mk_ino_hash_key_initialized) goto unlock; - err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, - HKDF_CONTEXT_INODE_HASH_KEY, NULL, 0, - (u8 *)&mk->mk_ino_hash_key, - sizeof(mk->mk_ino_hash_key)); + err = fscrypt_derive_siphash_key(mk, + HKDF_CONTEXT_INODE_HASH_KEY, + NULL, 0, &mk->mk_ino_hash_key); if (err) goto unlock; /* pairs with smp_load_acquire() above */