crypto: algif_hash - Handle NULL hashes correctly

Right now attempting to read an empty hash simply returns zeroed
bytes, this patch corrects this by calling the digest function
using an empty input.

Reported-by: Russell King - ARM Linux <linux@armlinux.org.uk>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c
index 68a5ceaa04c81072f453a7b2ca2605bed39bd5a1..2d8466f9e49b8632527ed1e2f35617ff02f5fac1 100644 (file)
--- a/crypto/algif_hash.c
+++ b/crypto/algif_hash.c
@@ -39,6 +39,37 @@ struct algif_hash_tfm {
        bool has_key;
 };
 
+static int hash_alloc_result(struct sock *sk, struct hash_ctx *ctx)
+{
+       unsigned ds;
+
+       if (ctx->result)
+               return 0;
+
+       ds = crypto_ahash_digestsize(crypto_ahash_reqtfm(&ctx->req));
+
+       ctx->result = sock_kmalloc(sk, ds, GFP_KERNEL);
+       if (!ctx->result)
+               return -ENOMEM;
+
+       memset(ctx->result, 0, ds);
+
+       return 0;
+}
+
+static void hash_free_result(struct sock *sk, struct hash_ctx *ctx)
+{
+       unsigned ds;
+
+       if (!ctx->result)
+               return;
+
+       ds = crypto_ahash_digestsize(crypto_ahash_reqtfm(&ctx->req));
+
+       sock_kzfree_s(sk, ctx->result, ds);
+       ctx->result = NULL;
+}
+
 static int hash_sendmsg(struct socket *sock, struct msghdr *msg,
                        size_t ignored)
 {
@@ -54,6 +85,9 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,
 
        lock_sock(sk);
        if (!ctx->more) {
+               if ((msg->msg_flags & MSG_MORE))
+                       hash_free_result(sk, ctx);
+
                err = af_alg_wait_for_completion(crypto_ahash_init(&ctx->req),
                                                &ctx->completion);
                if (err)
@@ -90,6 +124,10 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,
 
        ctx->more = msg->msg_flags & MSG_MORE;
        if (!ctx->more) {
+               err = hash_alloc_result(sk, ctx);
+               if (err)
+                       goto unlock;
+
                ahash_request_set_crypt(&ctx->req, NULL, ctx->result, 0);
                err = af_alg_wait_for_completion(crypto_ahash_final(&ctx->req),
                                                 &ctx->completion);
@@ -116,6 +154,13 @@ static ssize_t hash_sendpage(struct socket *sock, struct page *page,
        sg_init_table(ctx->sgl.sg, 1);
        sg_set_page(ctx->sgl.sg, page, size, offset);
 
+       if (!(flags & MSG_MORE)) {
+               err = hash_alloc_result(sk, ctx);
+               if (err)
+                       goto unlock;
+       } else if (!ctx->more)
+               hash_free_result(sk, ctx);
+
        ahash_request_set_crypt(&ctx->req, ctx->sgl.sg, ctx->result, size);
 
        if (!(flags & MSG_MORE)) {
@@ -153,6 +198,7 @@ static int hash_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
        struct alg_sock *ask = alg_sk(sk);
        struct hash_ctx *ctx = ask->private;
        unsigned ds = crypto_ahash_digestsize(crypto_ahash_reqtfm(&ctx->req));
+       bool result;
        int err;
 
        if (len > ds)
@@ -161,17 +207,29 @@ static int hash_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
                msg->msg_flags |= MSG_TRUNC;
 
        lock_sock(sk);
+       result = ctx->result;
+       err = hash_alloc_result(sk, ctx);
+       if (err)
+               goto unlock;
+
+       ahash_request_set_crypt(&ctx->req, NULL, ctx->result, 0);
+
        if (ctx->more) {
                ctx->more = 0;
-               ahash_request_set_crypt(&ctx->req, NULL, ctx->result, 0);
                err = af_alg_wait_for_completion(crypto_ahash_final(&ctx->req),
                                                 &ctx->completion);
                if (err)
                        goto unlock;
+       } else if (!result) {
+               err = af_alg_wait_for_completion(
+                               crypto_ahash_digest(&ctx->req),
+                               &ctx->completion);
        }
 
        err = memcpy_to_msg(msg, ctx->result, len);
 
+       hash_free_result(sk, ctx);
+
 unlock:
        release_sock(sk);
 
@@ -394,8 +452,7 @@ static void hash_sock_destruct(struct sock *sk)
        struct alg_sock *ask = alg_sk(sk);
        struct hash_ctx *ctx = ask->private;
 
-       sock_kzfree_s(sk, ctx->result,
-                     crypto_ahash_digestsize(crypto_ahash_reqtfm(&ctx->req)));
+       hash_free_result(sk, ctx);
        sock_kfree_s(sk, ctx, ctx->len);
        af_alg_release_parent(sk);
 }
@@ -407,20 +464,12 @@ static int hash_accept_parent_nokey(void *private, struct sock *sk)
        struct algif_hash_tfm *tfm = private;
        struct crypto_ahash *hash = tfm->hash;
        unsigned len = sizeof(*ctx) + crypto_ahash_reqsize(hash);
-       unsigned ds = crypto_ahash_digestsize(hash);
 
        ctx = sock_kmalloc(sk, len, GFP_KERNEL);
        if (!ctx)
                return -ENOMEM;
 
-       ctx->result = sock_kmalloc(sk, ds, GFP_KERNEL);
-       if (!ctx->result) {
-               sock_kfree_s(sk, ctx, len);
-               return -ENOMEM;
-       }
-
-       memset(ctx->result, 0, ds);
-
+       ctx->result = NULL;
        ctx->len = len;
        ctx->more = 0;
        af_alg_init_completion(&ctx->completion);