linux-kernel - Re: [PATCH RFC 0/4] Add firmware signature file check

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Date:	Tue, 6 Nov 2012 13:46:08 +0800
From:	lee joey <joeyli.kernel@...il.com>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	Takashi Iwai <tiwai@...e.de>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, joeyli <jlee@...e.com>,
	Jiri Kosina <jkosina@...e.cz>,
	David Howells <dhowells@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org
Subject: Re: [PATCH RFC 0/4] Add firmware signature file check

2012/11/6 Ming Lei <tom.leiming@...il.com>:
> On Tue, Nov 6, 2012 at 1:18 AM, Takashi Iwai <tiwai@...e.de> wrote:
>>
>> To be noted, it doesn't support the firmwares via udev but only the
>> direct loading, and the check for built-in firmware is missing, too.
>
> Generally, both direct loading and udev may request one same firmware
> image. And after check failed, current firmware load will fallback on udev
> to complete loading, so looks a check-failed firmware still can be loaded
> into kernel no matter if there is firmware signature check or not.
>
>
> Thanks,
> --
> Ming Lei
> --
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The udev direct write firmware through data attribute, maybe we can do
the same signature verification in firmware_data_write? The following
patch didn't test yet.


Thanks
Joey Lee

>From 035dde5fadc9e7f4b7811b18d3a5094ef88e8bbb Mon Sep 17 00:00:00 2001
From: Lee, Chun-Yi <jlee@...e.com>
Date: Tue, 6 Nov 2012 13:07:04 +0800
Subject: [PATCH] firmware: Add signature check to firmware_data_write

---
 drivers/base/firmware_class.c |   18 ++++++++++++++++++
 1 files changed, 18 insertions(+), 0 deletions(-)

diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index 8945f4e..40d8cc6 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -621,6 +621,7 @@ static ssize_t firmware_data_write(struct file
*filp, struct kobject *kobj,
        struct firmware_priv *fw_priv = to_firmware_priv(dev);
        struct firmware_buf *buf;
        ssize_t retval;
+       bool success = false;

        if (!capable(CAP_SYS_RAWIO))
                return -EPERM;
@@ -655,6 +656,23 @@ static ssize_t firmware_data_write(struct file
*filp, struct kobject *kobj,
        }

        buf->size = max_t(size_t, offset, buf->size);
+
+#ifdef CONFIG_FIRMWARE_SIG
+       for (i = 0; i < ARRAY_SIZE(fw_path); i++) {
+               snprintf(path, PATH_MAX, "%s/%s.sig", fw_path[i], buf->fw_id);
+               if (verify_signature(buf, path))
+                       success = true;
+       }
+       if (!success) {
+               pr_err("Invalid signature file %s\n", path);
+               if (sig_enforce) {
+                       vfree(buf->data);
+                       buf->data = NULL;
+                       buf->size = 0;
+               }
+               retval = -ENOENT;
+       }
+#endif /* CONFIG_FIRMWARE_SIG */
 out:
        mutex_unlock(&fw_lock);
        return retval;
-- 
1.6.4.2
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