Messages in this thread | | | From | Kees Cook <> | Date | Tue, 8 May 2018 16:14:25 -0700 | Subject | Re: [PATCH v3 1/3] big key: get rid of stack array allocation |
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On Tue, Apr 24, 2018 at 1:26 PM, Tycho Andersen <tycho@tycho.ws> wrote: > We're interested in getting rid of all of the stack allocated arrays in the > kernel [1]. This patch simply hardcodes the iv length to match that of the > hardcoded cipher. > > [1]: https://lkml.org/lkml/2018/3/7/621 > > v2: hardcode the length of the nonce to be the GCM AES IV length, and do a > sanity check in init(), Eric Biggers > v3: * remember to free big_key_aead when sanity check fails > * define a constant for big key IV size so it can be changed along side > the algorithm in the code > > Signed-off-by: Tycho Andersen <tycho@tycho.ws> > CC: David Howells <dhowells@redhat.com> > CC: James Morris <jmorris@namei.org> > CC: "Serge E. Hallyn" <serge@hallyn.com> > CC: Jason A. Donenfeld <Jason@zx2c4.com> > CC: Eric Biggers <ebiggers3@gmail.com>
Please consider this and patches 2 and 3:
Reviewed-by: Kees Cook <keescook@chromium.org>
James, are these something you can take into your tree?
Thanks!
-Kees
> --- > security/keys/big_key.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/security/keys/big_key.c b/security/keys/big_key.c > index 933623784ccd..2806e70d7f8f 100644 > --- a/security/keys/big_key.c > +++ b/security/keys/big_key.c > @@ -22,6 +22,7 @@ > #include <keys/user-type.h> > #include <keys/big_key-type.h> > #include <crypto/aead.h> > +#include <crypto/gcm.h> > > struct big_key_buf { > unsigned int nr_pages; > @@ -85,6 +86,7 @@ struct key_type key_type_big_key = { > * Crypto names for big_key data authenticated encryption > */ > static const char big_key_alg_name[] = "gcm(aes)"; > +#define BIG_KEY_IV_SIZE GCM_AES_IV_SIZE > > /* > * Crypto algorithms for big_key data authenticated encryption > @@ -109,7 +111,7 @@ static int big_key_crypt(enum big_key_op op, struct big_key_buf *buf, size_t dat > * an .update function, so there's no chance we'll wind up reusing the > * key to encrypt updated data. Simply put: one key, one encryption. > */ > - u8 zero_nonce[crypto_aead_ivsize(big_key_aead)]; > + u8 zero_nonce[BIG_KEY_IV_SIZE]; > > aead_req = aead_request_alloc(big_key_aead, GFP_KERNEL); > if (!aead_req) > @@ -425,6 +427,13 @@ static int __init big_key_init(void) > pr_err("Can't alloc crypto: %d\n", ret); > return ret; > } > + > + if (unlikely(crypto_aead_ivsize(big_key_aead) != BIG_KEY_IV_SIZE)) { > + WARN(1, "big key algorithm changed?"); > + ret = -EINVAL; > + goto free_aead; > + } > + > ret = crypto_aead_setauthsize(big_key_aead, ENC_AUTHTAG_SIZE); > if (ret < 0) { > pr_err("Can't set crypto auth tag len: %d\n", ret); > -- > 2.17.0 >
-- Kees Cook Pixel Security
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