From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 45AF81F37BC for ; Tue, 11 Feb 2025 10:25:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739269534; cv=none; b=GfbNnnr0k4iNzNtNYoxmxYg3LBqi1bC0gsA5b1Ro6HVCwRSEwIuHIt1SpqUvUZPdt/U4l5Zp+a8MiHydt+BP7oxAg07vZdBmGtdsHODf449Ol5oJdqFvpZFvIMigp2iAJ1g0m7N1yiUQvgLxmMZmUAjhiVywz2qEhDooBIcLupQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739269534; c=relaxed/simple; bh=08cnuYWYO85ahhezqBhL3nR0inzgRgnhwVMg3pK2IQk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZUZ2B6O1q/f8DhDb4fKK1EvVm52j1cVWNjb8QY+KIEQVG/6TfY2Tq3DGfHeht51/7QapkEbsWnx6asTBT3ElSWJlXSG5CWOsivcL9ITXgE+gOAsVriLVg1R7EImcgvUZ6KXqxO6N5u+21y735hnirqPz/OL8CvBSPPqGOun0CDI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=OSD0BXIE; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="OSD0BXIE" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1739269531; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ju4/C2MmdqFBt3EZ3dGeQXInbmS7DyAXI6nPulqtCKU=; b=OSD0BXIEvlnWpcL+yHCBzKtzAtY5xqj4ckRGi8q/R9sM1pYrzOBa+pNWNOi4KgUKyj7vro SfwlDH1R8iHaUDyifOiTqkXZQXNgUvs75qyWHE+Q6OT7Ev36fmx2I6LsfhbW7DALHjJsX2 uuJJ8CpOC9j5NH9LiOCd1Uf2rTnlyeQ= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-427-R6GSeaoCNOmgc-aeMH9sTw-1; Tue, 11 Feb 2025 05:25:27 -0500 X-MC-Unique: R6GSeaoCNOmgc-aeMH9sTw-1 X-Mimecast-MFC-AGG-ID: R6GSeaoCNOmgc-aeMH9sTw Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id CF8E81800879; Tue, 11 Feb 2025 10:25:25 +0000 (UTC) Received: from localhost (unknown [10.72.112.8]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2AB9A1956094; Tue, 11 Feb 2025 10:25:23 +0000 (UTC) Date: Tue, 11 Feb 2025 18:25:18 +0800 From: Baoquan He To: Coiby Xu Cc: akpm@linux-foundation.org, kexec@lists.infradead.org, Ondrej Kozina , Milan Broz , Thomas Staudt , Daniel P =?iso-8859-1?Q?=2E_Berrang=E9?= , Kairui Song , Pingfan Liu , Dave Young , linux-kernel@vger.kernel.org, x86@kernel.org, Dave Hansen , Vitaly Kuznetsov Subject: Re: [PATCH v8 0/7] Support kdump with LUKS encryption by reusing LUKS volume keys Message-ID: References: <20250207080818.129165-1-coxu@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250207080818.129165-1-coxu@redhat.com> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 On 02/07/25 at 04:08pm, Coiby Xu wrote: > LUKS is the standard for Linux disk encryption, widely adopted by users, > and in some cases, such as Confidential VMs, it is a requirement. With > kdump enabled, when the first kernel crashes, the system can boot into > the kdump/crash kernel to dump the memory image (i.e., /proc/vmcore) > to a specified target. However, there are two challenges when dumping > vmcore to a LUKS-encrypted device: > > - Kdump kernel may not be able to decrypt the LUKS partition. For some > machines, a system administrator may not have a chance to enter the > password to decrypt the device in kdump initramfs after the 1st kernel > crashes; For cloud confidential VMs, depending on the policy the > kdump kernel may not be able to unseal the keys with TPM and the > console virtual keyboard is untrusted. > > - LUKS2 by default use the memory-hard Argon2 key derivation function > which is quite memory-consuming compared to the limited memory reserved > for kdump. Take Fedora example, by default, only 256M is reserved for > systems having memory between 4G-64G. With LUKS enabled, ~1300M needs > to be reserved for kdump. Note if the memory reserved for kdump can't > be used by 1st kernel i.e. an user sees ~1300M memory missing in the > 1st kernel. > > Besides users (at least for Fedora) usually expect kdump to work out of > the box i.e. no manual password input or custom crashkernel value is > needed. And it doesn't make sense to derivate the keys again in kdump > kernel which seems to be redundant work. > > This patch set addresses the above issues by making the LUKS volume keys > persistent for kdump kernel with the help of cryptsetup's new APIs > (--link-vk-to-keyring/--volume-key-keyring). Here is the life cycle of > the kdump copies of LUKS volume keys, > > 1. After the 1st kernel loads the initramfs during boot, systemd > use an user-input passphrase to de-crypt the LUKS volume keys > or TPM-sealed key and then save the volume keys to specified keyring > (using the --link-vk-to-keyring API) and the key will expire within > specified time. > > 2. A user space tool (kdump initramfs loader like kdump-utils) create > key items inside /sys/kernel/config/crash_dm_crypt_keys to inform > the 1st kernel which keys are needed. > > 3. When the kdump initramfs is loaded by the kexec_file_load > syscall, the 1st kernel will iterate created key items, save the > keys to kdump reserved memory. > > 4. When the 1st kernel crashes and the kdump initramfs is booted, the > kdump initramfs asks the kdump kernel to create a user key using the > key stored in kdump reserved memory by writing yes to > /sys/kernel/crash_dm_crypt_keys/restore. Then the LUKS encrypted > device is unlocked with libcryptsetup's --volume-key-keyring API. > > 5. The system gets rebooted to the 1st kernel after dumping vmcore to > the LUKS encrypted device is finished > > After libcryptsetup saving the LUKS volume keys to specified keyring, > whoever takes this should be responsible for the safety of these copies > of keys. The keys will be saved in the memory area exclusively reserved > for kdump where even the 1st kernel has no direct access. And further > more, two additional protections are added, > - save the copy randomly in kdump reserved memory as suggested by Jan > - clear the _PAGE_PRESENT flag of the page that stores the copy as > suggested by Pingfan > > This patch set only supports x86. There will be patches to support other > architectures once this patch set gets merged. This v8 looks good to me, thanks for the great effort, Coiby. Acked-by: Baoquan He