[kernel-hardening] Re: Remaining crypto API regressions with CONFIG_VMAP_STACK

[Eric Biggers <ebiggers3@gmail.com>]

On Sun, Dec 11, 2016 at 11:13:55AM -0800, Andy Lutomirski wrote:
> On Fri, Dec 9, 2016 at 3:08 PM, Eric Biggers <ebiggers3@gmail.com> wrote:
> > In the 4.9 kernel, virtually-mapped stacks will be supported and enabled by
> > default on x86_64.  This has been exposing a number of problems in which
> > on-stack buffers are being passed into the crypto API, which to support crypto
> > accelerators operates on 'struct page' rather than on virtual memory.
> >
> 
> >         fs/cifs/smbencrypt.c:96
> 
> This should use crypto_cipher_encrypt_one(), I think.
> 
> --Andy

Yes, I believe that's correct.  It encrypts 8 bytes with ecb(des) which is
equivalent to simply encrypting one block with DES.  Maybe try the following
(untested):

static int
smbhash(unsigned char *out, const unsigned char *in, unsigned char *key)
{
	unsigned char key2[8];
	struct crypto_cipher *cipher;

	str_to_key(key, key2);

	cipher = crypto_alloc_cipher("des", 0, 0);
	if (IS_ERR(cipher)) {
		cifs_dbg(VFS, "could not allocate des cipher\n");
		return PTR_ERR(cipher);
	}

	crypto_cipher_setkey(cipher, key2, 8);

	crypto_cipher_encrypt_one(cipher, out, in);

	crypto_free_cipher(cipher);
	return 0;
}

- Eric