[PATCH] crypto: nx: Fix memcpy() over-reading in nonce

[PATCH] crypto: nx: Fix memcpy() over-reading in nonce

[Kees Cook]

Fix typo in memcpy() where size should be CTR_RFC3686_NONCE_SIZE.

Fixes: 030f4e968741 ("crypto: nx - Fix reentrancy bugs")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/crypto/nx/nx-aes-ctr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/crypto/nx/nx-aes-ctr.c b/drivers/crypto/nx/nx-aes-ctr.c
index 13f518802343..6120e350ff71 100644
--- a/drivers/crypto/nx/nx-aes-ctr.c
+++ b/drivers/crypto/nx/nx-aes-ctr.c
@@ -118,7 +118,7 @@ static int ctr3686_aes_nx_crypt(struct skcipher_request *req)
 	struct nx_crypto_ctx *nx_ctx = crypto_skcipher_ctx(tfm);
 	u8 iv[16];
 
-	memcpy(iv, nx_ctx->priv.ctr.nonce, CTR_RFC3686_IV_SIZE);
+	memcpy(iv, nx_ctx->priv.ctr.nonce, CTR_RFC3686_NONCE_SIZE);
 	memcpy(iv + CTR_RFC3686_NONCE_SIZE, req->iv, CTR_RFC3686_IV_SIZE);
 	iv[12] = iv[13] = iv[14] = 0;
 	iv[15] = 1;
-- 
2.25.1

Re: [PATCH] crypto: nx: Fix memcpy() over-reading in nonce

[Michael Ellerman]

Kees Cook <keescook@chromium.org> writes:
> Fix typo in memcpy() where size should be CTR_RFC3686_NONCE_SIZE.
>
> Fixes: 030f4e968741 ("crypto: nx - Fix reentrancy bugs")
> Cc: stable@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Thanks.

> ---
>  drivers/crypto/nx/nx-aes-ctr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/crypto/nx/nx-aes-ctr.c b/drivers/crypto/nx/nx-aes-ctr.c
> index 13f518802343..6120e350ff71 100644
> --- a/drivers/crypto/nx/nx-aes-ctr.c
> +++ b/drivers/crypto/nx/nx-aes-ctr.c
> @@ -118,7 +118,7 @@ static int ctr3686_aes_nx_crypt(struct skcipher_request *req)
>  	struct nx_crypto_ctx *nx_ctx = crypto_skcipher_ctx(tfm);
>  	u8 iv[16];
>  
> -	memcpy(iv, nx_ctx->priv.ctr.nonce, CTR_RFC3686_IV_SIZE);
> +	memcpy(iv, nx_ctx->priv.ctr.nonce, CTR_RFC3686_NONCE_SIZE);
>  	memcpy(iv + CTR_RFC3686_NONCE_SIZE, req->iv, CTR_RFC3686_IV_SIZE);
>  	iv[12] = iv[13] = iv[14] = 0;
>  	iv[15] = 1;

Where IV_SIZE is 8 and NONCE_SIZE is 4.

And iv is 16 bytes, so it's not a buffer overflow.

But priv.ctr.nonce is 4 bytes, and at the end of the struct, so it reads
4 bytes past the end of the nx_crypto_ctx, which is not good.

But then immediately overwrites whatever it read with req->iv.

So seems pretty harmless in practice?

cheers

Re: [PATCH] crypto: nx: Fix memcpy() over-reading in nonce

[Kees Cook]

On Thu, Jun 17, 2021 at 04:08:15PM +1000, Michael Ellerman wrote:
> Kees Cook <keescook@chromium.org> writes:
> > Fix typo in memcpy() where size should be CTR_RFC3686_NONCE_SIZE.
> >
> > Fixes: 030f4e968741 ("crypto: nx - Fix reentrancy bugs")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> 
> Thanks.
> 
> > ---
> >  drivers/crypto/nx/nx-aes-ctr.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/crypto/nx/nx-aes-ctr.c b/drivers/crypto/nx/nx-aes-ctr.c
> > index 13f518802343..6120e350ff71 100644
> > --- a/drivers/crypto/nx/nx-aes-ctr.c
> > +++ b/drivers/crypto/nx/nx-aes-ctr.c
> > @@ -118,7 +118,7 @@ static int ctr3686_aes_nx_crypt(struct skcipher_request *req)
> >  	struct nx_crypto_ctx *nx_ctx = crypto_skcipher_ctx(tfm);
> >  	u8 iv[16];
> >  
> > -	memcpy(iv, nx_ctx->priv.ctr.nonce, CTR_RFC3686_IV_SIZE);
> > +	memcpy(iv, nx_ctx->priv.ctr.nonce, CTR_RFC3686_NONCE_SIZE);
> >  	memcpy(iv + CTR_RFC3686_NONCE_SIZE, req->iv, CTR_RFC3686_IV_SIZE);
> >  	iv[12] = iv[13] = iv[14] = 0;
> >  	iv[15] = 1;
> 
> Where IV_SIZE is 8 and NONCE_SIZE is 4.
> 
> And iv is 16 bytes, so it's not a buffer overflow.
> 
> But priv.ctr.nonce is 4 bytes, and at the end of the struct, so it reads
> 4 bytes past the end of the nx_crypto_ctx, which is not good.
> 
> But then immediately overwrites whatever it read with req->iv.
> 
> So seems pretty harmless in practice?

Right -- there's no damage done, but future memcpy() FORTIFY work alerts
on this, so I'm going through cleaning all of these up. :)

-- 
Kees Cook

Re: [PATCH] crypto: nx: Fix memcpy() over-reading in nonce

[Herbert Xu]

On Wed, Jun 16, 2021 at 01:34:59PM -0700, Kees Cook wrote:
> Fix typo in memcpy() where size should be CTR_RFC3686_NONCE_SIZE.
> 
> Fixes: 030f4e968741 ("crypto: nx - Fix reentrancy bugs")
> Cc: stable@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  drivers/crypto/nx/nx-aes-ctr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt