On 11/12/2014 08:05 AM, Stephan Mueller wrote:
This patch adds the random number generator support for AF_ALG.
A random number generator's purpose is to generate data without
requiring the caller to provide any data. Therefore, the AF_ALG
interface handler for RNGs only implements a callback handler for
recvmsg.
...
+static int rng_recvmsg(struct kiocb *unused, struct socket *sock,
+ struct msghdr *msg, size_t len, int flags)
+{
+ struct sock *sk = sock->sk;
+ struct alg_sock *ask = alg_sk(sk);
+ struct rng_ctx *ctx = ask->private;
+ int err = -EFAULT;
+
+ if (0 == len)
if (len == 0)
...
[And also other places.]
We don't use Yoda condition style in the kernel.
+ return 0;
+ if (MAXSIZE < len)
+ len = MAXSIZE;
+
+ lock_sock(sk);
+ len = crypto_rng_get_bytes(ctx->drng, ctx->result, len);
+ if (0 > len)
+ goto unlock;
+
+ err = memcpy_toiovec(msg->msg_iov, ctx->result, len);
+ memset(ctx->result, 0, err);
+
This looks buggy.
If copy_to_user() fails from within memcpy_toiovec(), we call memset()
with a negative return value which is interpreted as size_t and thus
causes a buffer overflow writing beyond ctx->result, no?
If it succeeds, we call memset(ctx->result, 0, 0) .....
+unlock:
+ release_sock(sk);
+
+ return err ? err : len;
+}
+
+static struct proto_ops algif_rng_ops = {
+ .family = PF_ALG,
+
+ .connect = sock_no_connect,
+ .socketpair = sock_no_socketpair,
+ .getname = sock_no_getname,
+ .ioctl = sock_no_ioctl,
+ .listen = sock_no_listen,
+ .shutdown = sock_no_shutdown,
+ .getsockopt = sock_no_getsockopt,
+ .mmap = sock_no_mmap,
+ .bind = sock_no_bind,
+ .accept = sock_no_accept,
+ .setsockopt = sock_no_setsockopt,
+ .poll = sock_no_poll,
+ .sendmsg = sock_no_sendmsg,
+ .sendpage = sock_no_sendpage,
+
+ .release = af_alg_release,
+ .recvmsg = rng_recvmsg,
+};
+
+static void *rng_bind(const char *name, u32 type, u32 mask)
+{
+ return crypto_alloc_rng(name, type, mask);
+}
+
+static void rng_release(void *private)
+{
+ crypto_free_rng(private);
+}
+
+static void rng_sock_destruct(struct sock *sk)
+{
+ struct alg_sock *ask = alg_sk(sk);
+ struct rng_ctx *ctx = ask->private;
+
+ memset(ctx->result, 0, MAXSIZE);
memset(ctx->result, 0, sizeof(ctx->result));
+ sock_kfree_s(sk, ctx, ctx->len);
+ af_alg_release_parent(sk);
+}
+
+static int rng_accept_parent(void *private, struct sock *sk)
+{
+ struct rng_ctx *ctx;
+ struct alg_sock *ask = alg_sk(sk);
+ unsigned int len = sizeof(*ctx);
+ int seedsize = crypto_rng_seedsize(private);
+ int ret = -ENOMEM;
+
+ ctx = sock_kmalloc(sk, len, GFP_KERNEL);
+ if (!ctx)
+ return -ENOMEM;
+ memset(ctx->result, 0, MAXSIZE);
Ditto...
+ ctx->len = len;
+
+ if (seedsize) {
+ u8 *buf = kmalloc(seedsize, GFP_KERNEL);
+ if (!buf)
+ goto err;
+ get_random_bytes(buf, seedsize);
+ ret = crypto_rng_reset(private, buf, len);
+ kzfree(buf);
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