From mboxrd@z Thu Jan 1 00:00:00 1970 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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 CB143C433E0 for ; Tue, 7 Jul 2020 17:14:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AA055206F6 for ; Tue, 7 Jul 2020 17:14:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=broadcom.com header.i=@broadcom.com header.b="dzipK/c+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728385AbgGGROB (ORCPT ); Tue, 7 Jul 2020 13:14:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49890 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728362AbgGGRN7 (ORCPT ); Tue, 7 Jul 2020 13:13:59 -0400 Received: from mail-pf1-x441.google.com (mail-pf1-x441.google.com [IPv6:2607:f8b0:4864:20::441]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 957C2C08C5E3 for ; Tue, 7 Jul 2020 10:13:59 -0700 (PDT) Received: by mail-pf1-x441.google.com with SMTP id x72so9265210pfc.6 for ; Tue, 07 Jul 2020 10:13:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding:content-language; bh=HtwXtpph2OoeeE3uD1Wi+DXJnoAVgPcW38Mw9B+yPaE=; b=dzipK/c+2ZtFsuqwsrTcL/d1Yv8zQfVpnmVDF5jdaKLo4l/L0jd2RP/hL4s3Yr7L39 jwBA+QtRbToqLcum6mDVLTCl2kTLhyzMXa5bQLsbtwSfa8Ypv7iELew2HUxgzxRYGmGZ naco+TSnJERTyBinS1dUilsIYM1AfRFHFx/sk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=HtwXtpph2OoeeE3uD1Wi+DXJnoAVgPcW38Mw9B+yPaE=; b=sjatDLF6NhY/D6Jnh0xd8JZfchnx0btWTOLX+xr71Ap8YCZim1bbfH6pesEnolIMkY FQE+q2dT5v3EmROz6+W/bkdhGqqOgTkcoDQqEijOuv0V7oX60TePon17Jw3tDnLuapoH N18UJk3TWNdJwIMLq8/6LESGuTyQ2NmUDUHlmwpDkJ06WzRYQ1uoFRl9Uvc8bpwiOMKD ZPX7ZQftPQaFNj+dQVUS/Jel27H3nE5dk1xaqXtSIsOn49BhF95kiVjLH6gJ6WeAb4ao 9H1UpBqs7DQCpe6jY41l/zI77RTIVimcOTDM3Lpu/6UGhobXflIkuEKdypr/ZUXoWxtP DBDw== X-Gm-Message-State: AOAM532j7PEM3PcZNyKcwiBTtBHVPoXFv146R95x2OGcf4N40xE80F3d yIzcfKAy4g5jt44D4dD8PUqhBA== X-Google-Smtp-Source: ABdhPJyeSq0J8hJSh8EyLFyNDGaXMs3fPXkpyq9VbmAPXqtEFkmdoQuH8aOIqAG0WttuGA3gnpzq7w== X-Received: by 2002:a62:8782:: with SMTP id i124mr49547162pfe.267.1594142038788; Tue, 07 Jul 2020 10:13:58 -0700 (PDT) Received: from [10.136.13.65] ([192.19.228.250]) by smtp.gmail.com with ESMTPSA id j70sm23482082pfd.208.2020.07.07.10.13.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 07 Jul 2020 10:13:58 -0700 (PDT) Subject: Re: [PATCH v10 9/9] ima: add FIRMWARE_PARTIAL_READ support To: Kees Cook Cc: Luis Chamberlain , Wolfram Sang , Greg Kroah-Hartman , David Brown , Alexander Viro , Shuah Khan , bjorn.andersson@linaro.org, Shuah Khan , Arnd Bergmann , Mimi Zohar , "Rafael J . Wysocki" , linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-fsdevel@vger.kernel.org, BCM Kernel Feedback , Olof Johansson , Andrew Morton , Dan Carpenter , Colin Ian King , Takashi Iwai , linux-kselftest@vger.kernel.org, Andy Gross , linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org References: <20200706232309.12010-1-scott.branden@broadcom.com> <20200706232309.12010-10-scott.branden@broadcom.com> <202007061950.F6B3D9E6A@keescook> From: Scott Branden Message-ID: Date: Tue, 7 Jul 2020 10:13:42 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <202007061950.F6B3D9E6A@keescook> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Hi Kees, You and others are certainly more experts in the filesystem and security infrastructure of the kernel. What I am trying to accomplish is a simple operation: request part of a file into a buffer rather than the whole file. If someone could add such support I would be more than happy to use it. This has now bubbled into many other designs issues in the existing codebase. I will need more details on your comments - see below. On 2020-07-06 8:08 p.m., Kees Cook wrote: > On Mon, Jul 06, 2020 at 04:23:09PM -0700, Scott Branden wrote: >> Add FIRMWARE_PARTIAL_READ support for integrity >> measurement on partial reads of firmware files. > Hi, > > Several versions ago I'd suggested that the LSM infrastructure handle > the "full read" semantics so that individual LSMs don't need to each > duplicate the same efforts. As it happens, only IMA is impacted (SELinux > ignores everything except modules, and LoadPin only cares about origin > not contents). Does your patch series "Fix misused kernel_read_file() enums" handle this because this suggestion is outside the scope of my change? > > Next is the problem that enum kernel_read_file_id is an object > TYPE enum, not a HOW enum. (And it seems I missed the addition of > READING_FIRMWARE_PREALLOC_BUFFER, which may share a similar problem.) > That it's a partial read doesn't change _what_ you're reading: that's an > internal API detail. What happens when I attempt to do a partial read of > a kexec image? It does not appear there is any user of partial reads of kexec images? I have been informed by Greg K-H to not add apis that are not used so such support doesn't make sense to add at this time. > I'll use kernel_pread_file() and pass READING_KEXEC_IMAGE, > but the LSMs will have no idea it's a partial read. The addition I am adding is for request_partial_firmware_into_buf. In order to do so it adds internal support for partial reads of firmware files, not kexec image. The above seems outside the scope of my patch? > > Finally, what keeps the contents of the file from changing between the > first call (which IMA will read the entire file for) and the next reads > which will bypass IMA? The request is for a partial read.  IMA ensures the whole file integrity even though I only do a partial read. The next partial read will re-read and check integrity of file. > I'd suggested that the open file must have writes > disabled on it (as execve() does). The file will be reopened and integrity checked on the next partial read (if there is one). So I don't think there is any change to be made here. If writes aren't already disabled for a whole file read then that is something that needs to be fixed in the existing code. > > So, please redesign this: > - do not add an enum I used existing infrastructure provided by Mimi but now looks like it will have to fit with your patches from yesterday. > - make the file unwritable for the life of having the handle open It's no different than a full file read so no change to be made here. > - make the "full read" happen as part of the first partial read so the > LSMs don't have to reimplement everything Each partial read is an individual operation so I think a "full read" is performed every time if your security IMA is enabled.  If someone wants to add a file lock and then partial reads in the kernel then that would be different than what is needed by the kernel driver. > > -Kees > Regards, Scott