linux-kernel - [PATCH 4.19 130/280] crypto: skcipher - set CRYPTO_TFM_NEED

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Date:   Fri, 22 Mar 2019 12:14:43 +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, Eric Biggers <ebiggers@...gle.com>,
        Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH 4.19 130/280] crypto: skcipher - set CRYPTO_TFM_NEED_KEY if ->setkey() fails

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

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

From: Eric Biggers <ebiggers@...gle.com>

commit b1f6b4bf416b49f00f3abc49c639371cdecaaad1 upstream.

Some algorithms have a ->setkey() method that is not atomic, in the
sense that setting a key can fail after changes were already made to the
tfm context.  In this case, if a key was already set the tfm can end up
in a state that corresponds to neither the old key nor the new key.

For example, in lrw.c, if gf128mul_init_64k_bbe() fails due to lack of
memory, then priv::table will be left NULL.  After that, encryption with
that tfm will cause a NULL pointer dereference.

It's not feasible to make all ->setkey() methods atomic, especially ones
that have to key multiple sub-tfms.  Therefore, make the crypto API set
CRYPTO_TFM_NEED_KEY if ->setkey() fails and the algorithm requires a
key, to prevent the tfm from being used until a new key is set.

[Cc stable mainly because when introducing the NEED_KEY flag I changed
 AF_ALG to rely on it; and unlike in-kernel crypto API users, AF_ALG
 previously didn't have this problem.  So these "incompletely keyed"
 states became theoretically accessible via AF_ALG -- though, the
 opportunities for causing real mischief seem pretty limited.]

Fixes: f8d33fac8480 ("crypto: skcipher - prevent using skciphers without setting key")
Cc: <stable@...r.kernel.org> # v4.16+
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 crypto/skcipher.c |   27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

--- a/crypto/skcipher.c
+++ b/crypto/skcipher.c
@@ -584,6 +584,12 @@ static unsigned int crypto_skcipher_exts
 	return crypto_alg_extsize(alg);
 }
 
+static void skcipher_set_needkey(struct crypto_skcipher *tfm)
+{
+	if (tfm->keysize)
+		crypto_skcipher_set_flags(tfm, CRYPTO_TFM_NEED_KEY);
+}
+
 static int skcipher_setkey_blkcipher(struct crypto_skcipher *tfm,
 				     const u8 *key, unsigned int keylen)
 {
@@ -597,8 +603,10 @@ static int skcipher_setkey_blkcipher(str
 	err = crypto_blkcipher_setkey(blkcipher, key, keylen);
 	crypto_skcipher_set_flags(tfm, crypto_blkcipher_get_flags(blkcipher) &
 				       CRYPTO_TFM_RES_MASK);
-	if (err)
+	if (unlikely(err)) {
+		skcipher_set_needkey(tfm);
 		return err;
+	}
 
 	crypto_skcipher_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);
 	return 0;
@@ -676,8 +684,7 @@ static int crypto_init_skcipher_ops_blkc
 	skcipher->ivsize = crypto_blkcipher_ivsize(blkcipher);
 	skcipher->keysize = calg->cra_blkcipher.max_keysize;
 
-	if (skcipher->keysize)
-		crypto_skcipher_set_flags(skcipher, CRYPTO_TFM_NEED_KEY);
+	skcipher_set_needkey(skcipher);
 
 	return 0;
 }
@@ -697,8 +704,10 @@ static int skcipher_setkey_ablkcipher(st
 	crypto_skcipher_set_flags(tfm,
 				  crypto_ablkcipher_get_flags(ablkcipher) &
 				  CRYPTO_TFM_RES_MASK);
-	if (err)
+	if (unlikely(err)) {
+		skcipher_set_needkey(tfm);
 		return err;
+	}
 
 	crypto_skcipher_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);
 	return 0;
@@ -775,8 +784,7 @@ static int crypto_init_skcipher_ops_ablk
 			    sizeof(struct ablkcipher_request);
 	skcipher->keysize = calg->cra_ablkcipher.max_keysize;
 
-	if (skcipher->keysize)
-		crypto_skcipher_set_flags(skcipher, CRYPTO_TFM_NEED_KEY);
+	skcipher_set_needkey(skcipher);
 
 	return 0;
 }
@@ -819,8 +827,10 @@ static int skcipher_setkey(struct crypto
 	else
 		err = cipher->setkey(tfm, key, keylen);
 
-	if (err)
+	if (unlikely(err)) {
+		skcipher_set_needkey(tfm);
 		return err;
+	}
 
 	crypto_skcipher_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);
 	return 0;
@@ -852,8 +862,7 @@ static int crypto_skcipher_init_tfm(stru
 	skcipher->ivsize = alg->ivsize;
 	skcipher->keysize = alg->max_keysize;
 
-	if (skcipher->keysize)
-		crypto_skcipher_set_flags(skcipher, CRYPTO_TFM_NEED_KEY);
+	skcipher_set_needkey(skcipher);
 
 	if (alg->exit)
 		skcipher->base.exit = crypto_skcipher_exit_tfm;