From patchwork Sat Mar 14 20:50:49 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 11438459 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3A68014DD for ; Sun, 15 Mar 2020 01:39:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 112BB2076A for ; Sun, 15 Mar 2020 01:39:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584236357; bh=943w3/kHzpv8yrJchxtX35647H3Fo4/Z9SzqhVIuE68=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=fy9S537oRrUcnNOg2G67kvo1OuMRLXNv0BjBU2ipa0tc2Nxm3m6c5P0gQP5JurK1A ceG1HxXKgN3MzzRHDzvYMlgjYatlWVEnLqotvZqoOo8MGCILbD9cq5AKX+WgCf6VHn +hYG1Mdr9DbW4DOynnvcbRQu/n9nZPKXMeogehWc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726909AbgCOBjO (ORCPT ); Sat, 14 Mar 2020 21:39:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:55080 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726652AbgCOBjN (ORCPT ); Sat, 14 Mar 2020 21:39:13 -0400 Received: from sol.hsd1.ca.comcast.net (c-107-3-166-239.hsd1.ca.comcast.net [107.3.166.239]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 472DF2078E; Sat, 14 Mar 2020 20:53:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584219193; bh=943w3/kHzpv8yrJchxtX35647H3Fo4/Z9SzqhVIuE68=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HVapudXhbuo9OogmK1ui9KLdqV2e4nBmN5fBn+vYYR7bQSr3ZwMSyR+S4y/cHMzYx 2J/hsST49r3l9UAXpuKu2ztTekxefBjJuGOV2ULdBdefahlCi7FQQptKuBz4GstZcD PvVaTCMrdpd/qH8GtocfWO+2zIcOkz0CxYv3LNAY= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org Subject: [PATCH 1/4] fscrypt: add FS_IOC_GET_ENCRYPTION_NONCE ioctl Date: Sat, 14 Mar 2020 13:50:49 -0700 Message-Id: <20200314205052.93294-2-ebiggers@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200314205052.93294-1-ebiggers@kernel.org> References: <20200314205052.93294-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Eric Biggers Add an ioctl FS_IOC_GET_ENCRYPTION_NONCE which retrieves the nonce from an encrypted file or directory. The nonce is the 16-byte random value stored in the inode's encryption xattr. It is normally used together with the master key to derive the inode's actual encryption key. The nonces are needed by automated tests that verify the correctness of the ciphertext on-disk. Except for the IV_INO_LBLK_64 case, there's no way to replicate a file's ciphertext without knowing that file's nonce. The nonces aren't secret, and the existing ciphertext verification tests in xfstests retrieve them from disk using debugfs or dump.f2fs. But in environments that lack these debugging tools, getting the nonces by manually parsing the filesystem structure would be very hard. To make this important type of testing much easier, let's just add an ioctl that retrieves the nonce. Signed-off-by: Eric Biggers Reviewed-by: Theodore Ts'o --- Documentation/filesystems/fscrypt.rst | 11 +++++++++++ fs/crypto/fscrypt_private.h | 20 ++++++++++++++++++++ fs/crypto/keysetup.c | 16 ++-------------- fs/crypto/policy.c | 21 ++++++++++++++++++++- include/linux/fscrypt.h | 6 ++++++ include/uapi/linux/fscrypt.h | 1 + 6 files changed, 60 insertions(+), 15 deletions(-) diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst index bd99323448049..aa072112cfff2 100644 --- a/Documentation/filesystems/fscrypt.rst +++ b/Documentation/filesystems/fscrypt.rst @@ -633,6 +633,17 @@ from a passphrase or other low-entropy user credential. FS_IOC_GET_ENCRYPTION_PWSALT is deprecated. Instead, prefer to generate and manage any needed salt(s) in userspace. +Getting a file's encryption nonce +--------------------------------- + +Since Linux v5.7, the ioctl FS_IOC_GET_ENCRYPTION_NONCE is supported. +On encrypted files and directories it gets the inode's 16-byte nonce. +On unencrypted files and directories, it fails with ENODATA. + +This ioctl can be useful for automated tests which verify that the +encryption is being done correctly. It is not needed for normal use +of fscrypt. + Adding keys ----------- diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index 9aae851409e55..dbced2937ec89 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -76,6 +76,26 @@ static inline int fscrypt_context_size(const union fscrypt_context *ctx) return 0; } +/* Check whether an fscrypt_context has a recognized version number and size */ +static inline bool fscrypt_context_is_valid(const union fscrypt_context *ctx, + int ctx_size) +{ + return ctx_size >= 1 && ctx_size == fscrypt_context_size(ctx); +} + +/* Retrieve the context's nonce, assuming the context was already validated */ +static inline const u8 *fscrypt_context_nonce(const union fscrypt_context *ctx) +{ + switch (ctx->version) { + case FSCRYPT_CONTEXT_V1: + return ctx->v1.nonce; + case FSCRYPT_CONTEXT_V2: + return ctx->v2.nonce; + } + WARN_ON(1); + return NULL; +} + #undef fscrypt_policy union fscrypt_policy { u8 version; diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c index 65cb09fa6ead9..cb2803844726d 100644 --- a/fs/crypto/keysetup.c +++ b/fs/crypto/keysetup.c @@ -425,20 +425,8 @@ int fscrypt_get_encryption_info(struct inode *inode) goto out; } - switch (ctx.version) { - case FSCRYPT_CONTEXT_V1: - memcpy(crypt_info->ci_nonce, ctx.v1.nonce, - FS_KEY_DERIVATION_NONCE_SIZE); - break; - case FSCRYPT_CONTEXT_V2: - memcpy(crypt_info->ci_nonce, ctx.v2.nonce, - FS_KEY_DERIVATION_NONCE_SIZE); - break; - default: - WARN_ON(1); - res = -EINVAL; - goto out; - } + memcpy(crypt_info->ci_nonce, fscrypt_context_nonce(&ctx), + FS_KEY_DERIVATION_NONCE_SIZE); if (!fscrypt_supported_policy(&crypt_info->ci_policy, inode)) { res = -EINVAL; diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c index cf2a9d26ef7da..10ccf945020ce 100644 --- a/fs/crypto/policy.c +++ b/fs/crypto/policy.c @@ -258,7 +258,7 @@ int fscrypt_policy_from_context(union fscrypt_policy *policy_u, { memset(policy_u, 0, sizeof(*policy_u)); - if (ctx_size <= 0 || ctx_size != fscrypt_context_size(ctx_u)) + if (!fscrypt_context_is_valid(ctx_u, ctx_size)) return -EINVAL; switch (ctx_u->version) { @@ -481,6 +481,25 @@ int fscrypt_ioctl_get_policy_ex(struct file *filp, void __user *uarg) } EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_policy_ex); +/* FS_IOC_GET_ENCRYPTION_NONCE: retrieve file's encryption nonce for testing */ +int fscrypt_ioctl_get_nonce(struct file *filp, void __user *arg) +{ + struct inode *inode = file_inode(filp); + union fscrypt_context ctx; + int ret; + + ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); + if (ret < 0) + return ret; + if (!fscrypt_context_is_valid(&ctx, ret)) + return -EINVAL; + if (copy_to_user(arg, fscrypt_context_nonce(&ctx), + FS_KEY_DERIVATION_NONCE_SIZE)) + return -EFAULT; + return 0; +} +EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_nonce); + /** * fscrypt_has_permitted_context() - is a file's encryption policy permitted * within its directory? diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index 556f4adf5dc58..e3c2d2a155250 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -139,6 +139,7 @@ extern void fscrypt_free_bounce_page(struct page *bounce_page); extern int fscrypt_ioctl_set_policy(struct file *, const void __user *); extern int fscrypt_ioctl_get_policy(struct file *, void __user *); extern int fscrypt_ioctl_get_policy_ex(struct file *, void __user *); +extern int fscrypt_ioctl_get_nonce(struct file *filp, void __user *arg); extern int fscrypt_has_permitted_context(struct inode *, struct inode *); extern int fscrypt_inherit_context(struct inode *, struct inode *, void *, bool); @@ -300,6 +301,11 @@ static inline int fscrypt_ioctl_get_policy_ex(struct file *filp, return -EOPNOTSUPP; } +static inline int fscrypt_ioctl_get_nonce(struct file *filp, void __user *arg) +{ + return -EOPNOTSUPP; +} + static inline int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) { diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h index 0d8a6f47711c3..a10e3cdc28394 100644 --- a/include/uapi/linux/fscrypt.h +++ b/include/uapi/linux/fscrypt.h @@ -163,6 +163,7 @@ struct fscrypt_get_key_status_arg { #define FS_IOC_REMOVE_ENCRYPTION_KEY _IOWR('f', 24, struct fscrypt_remove_key_arg) #define FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS _IOWR('f', 25, struct fscrypt_remove_key_arg) #define FS_IOC_GET_ENCRYPTION_KEY_STATUS _IOWR('f', 26, struct fscrypt_get_key_status_arg) +#define FS_IOC_GET_ENCRYPTION_NONCE _IOR('f', 27, __u8[16]) /**********************************************************************/