crypto: skcipher - prevent using skciphers without setting key

Similar to what was done for the hash API, update the skcipher API to
track whether each transform has been keyed, and reject
encryption/decryption if a key is needed but one hasn't been set.

This isn't as important as the equivalent fix for the hash API because
symmetric ciphers almost always require a key (the "null cipher" is the
only exception), so are unlikely to be used without one.  Still,
tracking the key will prevent accidental unkeyed use.  algif_skcipher
also had to track the key anyway, so the new flag replaces that and
simplifies the algif_skcipher implementation.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

2 files changed, 39 insertions, 50 deletions

diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index c5c47b680152..c88e5e4cd6a6 100644
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -38,11 +38,6 @@
 #include <linux/net.h>
 #include <net/sock.h>
 
-struct skcipher_tfm {
-        struct crypto_skcipher *skcipher;
-        bool has_key;
-};
-
 static int skcipher_sendmsg(struct socket *sock, struct msghdr *msg,
                             size_t size)
 {
@@ -50,8 +45,7 @@ static int skcipher_sendmsg(struct socket *sock, struct msghdr *msg,
         struct alg_sock *ask = alg_sk(sk);
         struct sock *psk = ask->parent;
         struct alg_sock *pask = alg_sk(psk);
-        struct skcipher_tfm *skc = pask->private;
-        struct crypto_skcipher *tfm = skc->skcipher;
+        struct crypto_skcipher *tfm = pask->private;
         unsigned ivsize = crypto_skcipher_ivsize(tfm);
 
         return af_alg_sendmsg(sock, msg, size, ivsize);
@@ -65,8 +59,7 @@ static int _skcipher_recvmsg(struct socket *sock, struct msghdr *msg,
         struct sock *psk = ask->parent;
         struct alg_sock *pask = alg_sk(psk);
         struct af_alg_ctx *ctx = ask->private;
-        struct skcipher_tfm *skc = pask->private;
-        struct crypto_skcipher *tfm = skc->skcipher;
+        struct crypto_skcipher *tfm = pask->private;
         unsigned int bs = crypto_skcipher_blocksize(tfm);
         struct af_alg_async_req *areq;
         int err = 0;
@@ -221,7 +214,7 @@ static int skcipher_check_key(struct socket *sock)
         int err = 0;
         struct sock *psk;
         struct alg_sock *pask;
-        struct skcipher_tfm *tfm;
+        struct crypto_skcipher *tfm;
         struct sock *sk = sock->sk;
         struct alg_sock *ask = alg_sk(sk);
 
@@ -235,7 +228,7 @@ static int skcipher_check_key(struct socket *sock)
 
         err = -ENOKEY;
         lock_sock_nested(psk, SINGLE_DEPTH_NESTING);
-        if (!tfm->has_key)
+        if (crypto_skcipher_get_flags(tfm) & CRYPTO_TFM_NEED_KEY)
                 goto unlock;
 
         if (!pask->refcnt++)
@@ -314,41 +307,17 @@ static struct proto_ops algif_skcipher_ops_nokey = {
 
 static void *skcipher_bind(const char *name, u32 type, u32 mask)
 {
-        struct skcipher_tfm *tfm;
-        struct crypto_skcipher *skcipher;
-
-        tfm = kzalloc(sizeof(*tfm), GFP_KERNEL);
-        if (!tfm)
-                return ERR_PTR(-ENOMEM);
-
-        skcipher = crypto_alloc_skcipher(name, type, mask);
-        if (IS_ERR(skcipher)) {
-                kfree(tfm);
-                return ERR_CAST(skcipher);
-        }
-
-        tfm->skcipher = skcipher;
-
-        return tfm;
+        return crypto_alloc_skcipher(name, type, mask);
 }
 
 static void skcipher_release(void *private)
 {
-        struct skcipher_tfm *tfm = private;
-
-        crypto_free_skcipher(tfm->skcipher);
-        kfree(tfm);
+        crypto_free_skcipher(private);
 }
 
 static int skcipher_setkey(void *private, const u8 *key, unsigned int keylen)
 {
-        struct skcipher_tfm *tfm = private;
-        int err;
-
-        err = crypto_skcipher_setkey(tfm->skcipher, key, keylen);
-        tfm->has_key = !err;
-
-        return err;
+        return crypto_skcipher_setkey(private, key, keylen);
 }
 
 static void skcipher_sock_destruct(struct sock *sk)
@@ -357,8 +326,7 @@ static void skcipher_sock_destruct(struct sock *sk)
         struct af_alg_ctx *ctx = ask->private;
         struct sock *psk = ask->parent;
         struct alg_sock *pask = alg_sk(psk);
-        struct skcipher_tfm *skc = pask->private;
-        struct crypto_skcipher *tfm = skc->skcipher;
+        struct crypto_skcipher *tfm = pask->private;
 
         af_alg_pull_tsgl(sk, ctx->used, NULL, 0);
         sock_kzfree_s(sk, ctx->iv, crypto_skcipher_ivsize(tfm));
@@ -370,22 +338,21 @@ static int skcipher_accept_parent_nokey(void *private, struct sock *sk)
 {
         struct af_alg_ctx *ctx;
         struct alg_sock *ask = alg_sk(sk);
-        struct skcipher_tfm *tfm = private;
-        struct crypto_skcipher *skcipher = tfm->skcipher;
+        struct crypto_skcipher *tfm = private;
         unsigned int len = sizeof(*ctx);
 
         ctx = sock_kmalloc(sk, len, GFP_KERNEL);
         if (!ctx)
                 return -ENOMEM;
 
-        ctx->iv = sock_kmalloc(sk, crypto_skcipher_ivsize(skcipher),
+        ctx->iv = sock_kmalloc(sk, crypto_skcipher_ivsize(tfm),
                                GFP_KERNEL);
         if (!ctx->iv) {
                 sock_kfree_s(sk, ctx, len);
                 return -ENOMEM;
         }
 
-        memset(ctx->iv, 0, crypto_skcipher_ivsize(skcipher));
+        memset(ctx->iv, 0, crypto_skcipher_ivsize(tfm));
 
         INIT_LIST_HEAD(&ctx->tsgl_list);
         ctx->len = len;
@@ -405,9 +372,9 @@ static int skcipher_accept_parent_nokey(void *private, struct sock *sk)
 
 static int skcipher_accept_parent(void *private, struct sock *sk)
 {
-        struct skcipher_tfm *tfm = private;
+        struct crypto_skcipher *tfm = private;
 
-        if (!tfm->has_key && crypto_skcipher_has_setkey(tfm->skcipher))
+        if (crypto_skcipher_get_flags(tfm) & CRYPTO_TFM_NEED_KEY)
                 return -ENOKEY;
 
         return skcipher_accept_parent_nokey(private, sk);
diff --git a/crypto/skcipher.c b/crypto/skcipher.c
index 11af5fd6a443..0fe2a2923ad0 100644
--- a/crypto/skcipher.c
+++ b/crypto/skcipher.c
@@ -598,8 +598,11 @@ static int skcipher_setkey_blkcipher(struct crypto_skcipher *tfm,
         err = crypto_blkcipher_setkey(blkcipher, key, keylen);
         crypto_skcipher_set_flags(tfm, crypto_blkcipher_get_flags(blkcipher) &
                                        CRYPTO_TFM_RES_MASK);
+        if (err)
+                return err;
 
-        return err;
+        crypto_skcipher_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);
+        return 0;
 }
 
 static int skcipher_crypt_blkcipher(struct skcipher_request *req,
@@ -674,6 +677,9 @@ static int crypto_init_skcipher_ops_blkcipher(struct crypto_tfm *tfm)
         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);
+
         return 0;
 }
 
@@ -692,8 +698,11 @@ static int skcipher_setkey_ablkcipher(struct crypto_skcipher *tfm,
         crypto_skcipher_set_flags(tfm,
                                   crypto_ablkcipher_get_flags(ablkcipher) &
                                   CRYPTO_TFM_RES_MASK);
+        if (err)
+                return err;
 
-        return err;
+        crypto_skcipher_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);
+        return 0;
 }
 
 static int skcipher_crypt_ablkcipher(struct skcipher_request *req,
@@ -767,6 +776,9 @@ static int crypto_init_skcipher_ops_ablkcipher(struct crypto_tfm *tfm)
                             sizeof(struct ablkcipher_request);
         skcipher->keysize = calg->cra_ablkcipher.max_keysize;
 
+        if (skcipher->keysize)
+                crypto_skcipher_set_flags(skcipher, CRYPTO_TFM_NEED_KEY);
+
         return 0;
 }
 
@@ -796,6 +808,7 @@ static int skcipher_setkey(struct crypto_skcipher *tfm, const u8 *key,
 {
         struct skcipher_alg *cipher = crypto_skcipher_alg(tfm);
         unsigned long alignmask = crypto_skcipher_alignmask(tfm);
+        int err;
 
         if (keylen < cipher->min_keysize || keylen > cipher->max_keysize) {
                 crypto_skcipher_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
@@ -803,9 +816,15 @@ static int skcipher_setkey(struct crypto_skcipher *tfm, const u8 *key,
         }
 
         if ((unsigned long)key & alignmask)
-                return skcipher_setkey_unaligned(tfm, key, keylen);
+                err = skcipher_setkey_unaligned(tfm, key, keylen);
+        else
+                err = cipher->setkey(tfm, key, keylen);
+
+        if (err)
+                return err;
 
-        return cipher->setkey(tfm, key, keylen);
+        crypto_skcipher_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);
+        return 0;
 }
 
 static void crypto_skcipher_exit_tfm(struct crypto_tfm *tfm)
@@ -834,6 +853,9 @@ static int crypto_skcipher_init_tfm(struct crypto_tfm *tfm)
         skcipher->ivsize = alg->ivsize;
         skcipher->keysize = alg->max_keysize;
 
+        if (skcipher->keysize)
+                crypto_skcipher_set_flags(skcipher, CRYPTO_TFM_NEED_KEY);
+
         if (alg->exit)
                 skcipher->base.exit = crypto_skcipher_exit_tfm;