From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 4EDC01AB807; Mon, 5 Feb 2024 21:18:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707167885; cv=none; b=NXr3hwdCHpzIW+fj6a1pQ1myxallHAiuK7AYuVvi0Gk2kXxaQPCdC7QzLCTDiFKhMDHUn91kctFgJCpTL2BH4Hi3U6yOz7uU/EFk7976CtlYEol28YuNCmHiGbjdTDXquPCVS/uUIN7qwaxmM++GMl3PIy/+eym2oj0x1P+Dzu8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707167885; c=relaxed/simple; bh=/Enu6bwQmdx49axHA/1lmJJgKYU6G8zyTZPbq9OH+ck=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=CH7Uxpf3Cez8k7ZdIDuPUiiMg1kLZg5cecEHRLfRZ7OEIDG4p/8d5BYOvoOxnO9ebiuiBCez4yzN0H7+C9rP2x9koyqw/0Iz5sRxCbwgnXPwMryetGmJ1XlScJNKjJx/WDTPlDZTPff+sbwZ7Xn7w5VdP6NWOFKbwJOqid+IFX0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=W8TAC/No; arc=none smtp.client-ip=13.77.154.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="W8TAC/No" Received: from [10.137.106.151] (unknown [131.107.8.87]) by linux.microsoft.com (Postfix) with ESMTPSA id B65FB20B2000; Mon, 5 Feb 2024 13:18:03 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com B65FB20B2000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1707167883; bh=H595nLqKN1iU7O92UiJT9PEuwtk7Rd1yCbWBC1ZA8Dk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=W8TAC/No1VdGRZqMNpbRyarbJ0N1ksbo6q9VDwms6JAikfNWLiPh8pBpJItN4CS23 IfusA0S7VmJXlzwz6fInL7nOKKj4xPLnLwKrHbC0DxeKFY9uDlKLJYrmJTNL3IsRxQ NhwWoikC1Q5N62rvYtOFqHGPmfxebEyKNmpVRN1s= Message-ID: <13daca32-ee3f-46f5-a6ca-66bb02726e5c@linux.microsoft.com> Date: Mon, 5 Feb 2024 13:18:03 -0800 Precedence: bulk X-Mailing-List: audit@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v12 5/20] initramfs|security: Add security hook to initramfs unpack To: Paul Moore , corbet@lwn.net, zohar@linux.ibm.com, jmorris@namei.org, serge@hallyn.com, tytso@mit.edu, ebiggers@kernel.org, axboe@kernel.dk, agk@redhat.com, snitzer@kernel.org, eparis@redhat.com Cc: linux-doc@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, linux-fscrypt@vger.kernel.org, linux-block@vger.kernel.org, dm-devel@lists.linux.dev, audit@vger.kernel.org, linux-kernel@vger.kernel.org References: <1706654228-17180-6-git-send-email-wufan@linux.microsoft.com> Content-Language: en-US From: Fan Wu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/3/2024 2:25 PM, Paul Moore wrote: > On Jan 30, 2024 Fan Wu wrote: >> >> This patch introduces a new hook to notify security system that the >> content of initramfs has been unpacked into the rootfs. >> >> Upon receiving this notification, the security system can activate >> a policy to allow only files that originated from the initramfs to >> execute or load into kernel during the early stages of booting. >> >> This approach is crucial for minimizing the attack surface by >> ensuring that only trusted files from the initramfs are operational >> in the critical boot phase. >> >> Signed-off-by: Fan Wu >> --- >> v1-v11: >> + Not present >> >> v12: >> + Introduced >> --- >> include/linux/lsm_hook_defs.h | 4 ++++ >> include/linux/security.h | 10 ++++++++++ >> init/initramfs.c | 3 +++ >> security/security.c | 12 ++++++++++++ >> 4 files changed, 29 insertions(+) >> >> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h >> index 185924c56378..b247388786a9 100644 >> --- a/include/linux/lsm_hook_defs.h >> +++ b/include/linux/lsm_hook_defs.h >> @@ -425,3 +425,7 @@ LSM_HOOK(int, 0, uring_override_creds, const struct cred *new) >> LSM_HOOK(int, 0, uring_sqpoll, void) >> LSM_HOOK(int, 0, uring_cmd, struct io_uring_cmd *ioucmd) >> #endif /* CONFIG_IO_URING */ >> + >> +#ifdef CONFIG_BLK_DEV_INITRD >> +LSM_HOOK(void, LSM_RET_VOID, unpack_initramfs_security, void) >> +#endif /* CONFIG_BLK_DEV_INITRD */ > > Let's just call it "unpack_initramfs", the "_security" part is somewhat > implied since we are talking about a LSM hook ;) > >> diff --git a/init/initramfs.c b/init/initramfs.c >> index 76deb48c38cb..075a5794cde5 100644 >> --- a/init/initramfs.c >> +++ b/init/initramfs.c >> @@ -18,6 +18,7 @@ >> #include >> #include >> #include >> +#include >> >> static __initdata bool csum_present; >> static __initdata u32 io_csum; >> @@ -720,6 +721,8 @@ static void __init do_populate_rootfs(void *unused, async_cookie_t cookie) >> #endif >> } >> >> + security_unpack_initramfs(); > > Given the caller, what do you think of changing the hook name to > "security_initramfs_populated()"? I think this not only matches up > better with the caller, "do_populate_rootfs()", but since in using the > past tense we help indicate that this hook happens *after* the rootfs > is populated with the initramfs data. > Yeah, I agree this sounds better. I will update this part. -Fan >> done: >> /* >> * If the initrd region is overlapped with crashkernel reserved region, >> diff --git a/security/security.c b/security/security.c >> index ddf2e69cf8f2..2a527d4c69bc 100644 >> --- a/security/security.c >> +++ b/security/security.c >> @@ -5581,3 +5581,15 @@ int security_uring_cmd(struct io_uring_cmd *ioucmd) >> return call_int_hook(uring_cmd, 0, ioucmd); >> } >> #endif /* CONFIG_IO_URING */ >> + >> +#ifdef CONFIG_BLK_DEV_INITRD >> +/** >> + * security_unpack_initramfs() - Notify LSM that initramfs has been loaded >> + * >> + * Tells the LSM the initramfs has been unpacked into the rootfs. >> + */ >> +void security_unpack_initramfs(void) >> +{ >> + call_void_hook(unpack_initramfs_security); >> +} >> +#endif /* CONFIG_BLK_DEV_INITRD */ >> -- >> 2.43.0 > > -- > paul-moore.com