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From: Mimi Zohar <zohar@linux.ibm.com>
To: Kees Cook <keescook@chromium.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Scott Branden <scott.branden@broadcom.com>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Takashi Iwai <tiwai@suse.de>, Jessica Yu <jeyu@kernel.org>,
	SeongJae Park <sjpark@amazon.de>, KP Singh <kpsingh@chromium.org>,
	linux-efi@vger.kernel.org, linux-security-module@vger.kernel.org,
	linux-integrity@vger.kernel.org, selinux@vger.kernel.org,
	linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 10/17] firmware_loader: Use security_post_load_data()
Date: Thu, 06 Aug 2020 18:07:35 -0400
Message-ID: <6be709297b60260faf9fb8b741799d130a663d52.camel@linux.ibm.com> (raw)
In-Reply-To: <20200729175845.1745471-11-keescook@chromium.org>

On Wed, 2020-07-29 at 10:58 -0700, Kees Cook wrote:
> Now that security_post_load_data() is wired up, use it instead
> of the NULL file argument style of security_post_read_file(),
> and update the security_kernel_load_data() call to indicate that a
> security_kernel_post_load_data() call is expected.
> 
> Wire up the IMA check to match earlier logic. Perhaps a generalized
> change to ima_post_load_data() might look something like this:
> 
>     return process_buffer_measurement(buf, size,
>                                       kernel_load_data_id_str(load_id),
>                                       read_idmap[load_id] ?: FILE_CHECK,
>                                       0, NULL);
> 
> Signed-off-by: Kees Cook <keescook@chromium.org>

Other than one change and one question below, it looks good.

Reviewed-by:  Mimi Zohar <zohar@linux.ibm.com>

<snip>

> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 85000dc8595c..1a7bc4c7437d 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c

> @@ -706,7 +697,7 @@ int ima_load_data(enum kernel_load_data_id id, bool contents)
>  		}
>  		break;
>  	case LOADING_FIRMWARE:
> -		if (ima_enforce && (ima_appraise & IMA_APPRAISE_FIRMWARE)) {
> +		if (ima_enforce && (ima_appraise & IMA_APPRAISE_FIRMWARE) && !contents) {
>  			pr_err("Prevent firmware sysfs fallback loading.\n");

Appended signatures are limited to kernel modules and, more recently,
to the kexec kernel image, not firmware.  Without a file descriptor,
file signatures stored as an xattrs are not applicable either.  We
might as well fail earlier, rather than later.  Adding "!contents" is
unnecessary.

>  			return -EACCES;	/* INTEGRITY_UNKNOWN */
>  		}
> @@ -739,6 +730,15 @@ int ima_load_data(enum kernel_load_data_id id, bool contents)
>   */
>  int ima_post_load_data(char *buf, loff_t size, enum kernel_load_data_id load_id)
>  {
> +	if (load_id == LOADING_FIRMWARE) {
> +		if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
> +		    (ima_appraise & IMA_APPRAISE_ENFORCE)) {
> +			pr_err("Prevent firmware loading_store.\n");
> +			return -EACCES; /* INTEGRITY_UNKNOWN */
> +		}
> +		return 0;
> +	}

Even with failing LOADING_FIRMWARE early in ima_load_data(), is this
still needed for fw_sysfs_loading()?

thanks,

Mimi

> +
>  	return 0;
>  }
>  


  reply index

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-29 17:58 [PATCH v4 00/17] Introduce partial kernel_read_file() support Kees Cook
2020-07-29 17:58 ` [PATCH v4 01/17] test_firmware: Test platform fw loading on non-EFI systems Kees Cook
2020-07-29 17:58 ` [PATCH v4 02/17] fs/kernel_read_file: Remove FIRMWARE_PREALLOC_BUFFER enum Kees Cook
2020-07-29 17:58 ` [PATCH v4 03/17] fs/kernel_read_file: Remove FIRMWARE_EFI_EMBEDDED enum Kees Cook
2020-07-29 17:58 ` [PATCH v4 04/17] fs/kernel_read_file: Split into separate include file Kees Cook
2020-07-30  2:22   ` James Morris
2020-07-29 17:58 ` [PATCH v4 05/17] fs/kernel_read_file: Split into separate source file Kees Cook
2020-07-29 17:58 ` [PATCH v4 06/17] fs/kernel_read_file: Remove redundant size argument Kees Cook
2020-07-30  2:25   ` James Morris
2020-07-29 17:58 ` [PATCH v4 07/17] fs/kernel_read_file: Switch buffer size arg to size_t Kees Cook
2020-07-30  2:25   ` James Morris
2020-07-29 17:58 ` [PATCH v4 08/17] fs/kernel_read_file: Add file_size output argument Kees Cook
2020-07-30  2:26   ` James Morris
2020-07-29 17:58 ` [PATCH v4 09/17] LSM: Introduce kernel_post_load_data() hook Kees Cook
2020-08-06 21:59   ` Mimi Zohar
2020-08-07  0:21   ` KP Singh
2020-07-29 17:58 ` [PATCH v4 10/17] firmware_loader: Use security_post_load_data() Kees Cook
2020-08-06 22:07   ` Mimi Zohar [this message]
2020-07-29 17:58 ` [PATCH v4 11/17] module: Call security_kernel_post_load_data() Kees Cook
2020-08-05 14:53   ` Jessica Yu
2020-08-07  0:22     ` KP Singh
2020-07-29 17:58 ` [PATCH v4 12/17] LSM: Add "contents" flag to kernel_read_file hook Kees Cook
2020-08-07  0:23   ` Mimi Zohar
2020-07-29 17:58 ` [PATCH v4 13/17] IMA: Add support for file reads without contents Kees Cook
2020-07-29 17:58 ` [PATCH v4 14/17] fs/kernel_file_read: Add "offset" arg for partial reads Kees Cook
2020-07-29 17:58 ` [PATCH v4 15/17] firmware: Store opt_flags in fw_priv Kees Cook
2020-07-29 17:58 ` [PATCH v4 16/17] firmware: Add request_partial_firmware_into_buf() Kees Cook
2020-07-29 17:58 ` [PATCH v4 17/17] test_firmware: Test partial read support Kees Cook

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