linux-kernel - [PATCH 4.14 74/89] dm crypt: wipe kernel key copy after IV initialization

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Date:   Mon, 22 Jan 2018 09:45:54 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ondrej Kozina <okozina@...hat.com>,
        Milan Broz <gmazyland@...il.com>,
        Mike Snitzer <snitzer@...hat.com>
Subject: [PATCH 4.14 74/89] dm crypt: wipe kernel key copy after IV initialization

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ondrej Kozina <okozina@...hat.com>

commit dc94902bde1e158cd19c4deab208e5d6eb382a44 upstream.

Loading key via kernel keyring service erases the internal
key copy immediately after we pass it in crypto layer. This is
wrong because IV is initialized later and we use wrong key
for the initialization (instead of real key there's just zeroed
block).

The bug may cause data corruption if key is loaded via kernel keyring
service first and later same crypt device is reactivated using exactly
same key in hexbyte representation, or vice versa. The bug (and fix)
affects only ciphers using following IVs: essiv, lmk and tcw.

Fixes: c538f6ec9f56 ("dm crypt: add ability to use keys from the kernel key retention service")
Signed-off-by: Ondrej Kozina <okozina@...hat.com>
Reviewed-by: Milan Broz <gmazyland@...il.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/dm-crypt.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -2058,9 +2058,6 @@ static int crypt_set_keyring_key(struct
 
 	ret = crypt_setkey(cc);
 
-	/* wipe the kernel key payload copy in each case */
-	memset(cc->key, 0, cc->key_size * sizeof(u8));
-
 	if (!ret) {
 		set_bit(DM_CRYPT_KEY_VALID, &cc->flags);
 		kzfree(cc->key_string);
@@ -2528,6 +2525,10 @@ static int crypt_ctr_cipher(struct dm_ta
 		}
 	}
 
+	/* wipe the kernel key payload copy */
+	if (cc->key_string)
+		memset(cc->key, 0, cc->key_size * sizeof(u8));
+
 	return ret;
 }
 
@@ -2966,6 +2967,9 @@ static int crypt_message(struct dm_targe
 				return ret;
 			if (cc->iv_gen_ops && cc->iv_gen_ops->init)
 				ret = cc->iv_gen_ops->init(cc);
+			/* wipe the kernel key payload copy */
+			if (cc->key_string)
+				memset(cc->key, 0, cc->key_size * sizeof(u8));
 			return ret;
 		}
 		if (argc == 2 && !strcasecmp(argv[1], "wipe")) {
@@ -3012,7 +3016,7 @@ static void crypt_io_hints(struct dm_tar
 
 static struct target_type crypt_target = {
 	.name   = "crypt",
-	.version = {1, 18, 0},
+	.version = {1, 18, 1},
 	.module = THIS_MODULE,
 	.ctr    = crypt_ctr,
 	.dtr    = crypt_dtr,