Hello Ard,
Quoting Ard Biesheuvel (2020-06-25 09:18:16)
> The skcipher API dynamically instantiates the transformation object
> on request that implements the requested algorithm optimally on the
> given platform. This notion of optimality only matters for cases like
> bulk network or disk encryption, where performance can be a bottleneck,
> or in cases where the algorithm itself is not known at compile time.
>
> In the mscc case, we are dealing with AES encryption of a single
> block, and so neither concern applies, and we are better off using
> the AES library interface, which is lightweight and safe for this
> kind of use.
>
> Note that the scatterlist API does not permit references to buffers
> that are located on the stack, so the existing code is incorrect in
> any case, but avoiding the skcipher and scatterlist APIs entirely is
> the most straight-forward approach to fixing this.
>
> Cc: Antoine Tenart <antoine.tenart@xxxxxxxxxxx>
> Cc: Andrew Lunn <andrew@xxxxxxx>
> Cc: Florian Fainelli <f.fainelli@xxxxxxxxx>
> Cc: Heiner Kallweit <hkallweit1@xxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Fixes: 28c5107aa904e ("net: phy: mscc: macsec support")
> Reviewed-by: Eric Biggers <ebiggers@xxxxxxxxxx>
> Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Tested-by: Antoine Tenart <antoine.tenart@xxxxxxxxxxx>
That improves and simplifies a lot the code, thank you!
Antoine
> ---
> v2:
> - select CRYPTO_LIB_AES only if MACSEC is enabled
> - add Eric's R-b
>
> drivers/net/phy/Kconfig | 3 +-
> drivers/net/phy/mscc/mscc_macsec.c | 40 +++++---------------
> 2 files changed, 10 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
> index f25702386d83..e351d65533aa 100644
> --- a/drivers/net/phy/Kconfig
> +++ b/drivers/net/phy/Kconfig
> @@ -480,8 +480,7 @@ config MICROCHIP_T1_PHY
> config MICROSEMI_PHY
> tristate "Microsemi PHYs"
> depends on MACSEC || MACSEC=n
> - select CRYPTO_AES
> - select CRYPTO_ECB
> + select CRYPTO_LIB_AES if MACSEC
> help
> Currently supports VSC8514, VSC8530, VSC8531, VSC8540 and VSC8541 PHYs
>
> diff --git a/drivers/net/phy/mscc/mscc_macsec.c b/drivers/net/phy/mscc/mscc_macsec.c
> index b4d3dc4068e2..d53ca884b5c9 100644
> --- a/drivers/net/phy/mscc/mscc_macsec.c
> +++ b/drivers/net/phy/mscc/mscc_macsec.c
> @@ -10,7 +10,7 @@
> #include <linux/phy.h>
> #include <dt-bindings/net/mscc-phy-vsc8531.h>
>
> -#include <crypto/skcipher.h>
> +#include <crypto/aes.h>
>
> #include <net/macsec.h>
>
> @@ -500,39 +500,17 @@ static u32 vsc8584_macsec_flow_context_id(struct macsec_flow *flow)
> static int vsc8584_macsec_derive_key(const u8 key[MACSEC_KEYID_LEN],
> u16 key_len, u8 hkey[16])
> {
> - struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
> - struct skcipher_request *req = NULL;
> - struct scatterlist src, dst;
> - DECLARE_CRYPTO_WAIT(wait);
> - u32 input[4] = {0};
> + const u8 input[AES_BLOCK_SIZE] = {0};
> + struct crypto_aes_ctx ctx;
> int ret;
>
> - if (IS_ERR(tfm))
> - return PTR_ERR(tfm);
> -
> - req = skcipher_request_alloc(tfm, GFP_KERNEL);
> - if (!req) {
> - ret = -ENOMEM;
> - goto out;
> - }
> -
> - skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
> - CRYPTO_TFM_REQ_MAY_SLEEP, crypto_req_done,
> - &wait);
> - ret = crypto_skcipher_setkey(tfm, key, key_len);
> - if (ret < 0)
> - goto out;
> -
> - sg_init_one(&src, input, 16);
> - sg_init_one(&dst, hkey, 16);
> - skcipher_request_set_crypt(req, &src, &dst, 16, NULL);
> -
> - ret = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
> + ret = aes_expandkey(&ctx, key, key_len);
> + if (ret)
> + return ret;
>
> -out:
> - skcipher_request_free(req);
> - crypto_free_skcipher(tfm);
> - return ret;
> + aes_encrypt(&ctx, hkey, input);
> + memzero_explicit(&ctx, sizeof(ctx));
> + return 0;
> }
>
> static int vsc8584_macsec_transformation(struct phy_device *phydev,
> --
> 2.27.0
>
--
Antoine Ténart, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
