[PATCH] crypto: atmel-ecc - reject hardware ECDH without a public key

[Thorsten Blum <thorsten.blum@linux.dev>]

The hardware ECDH path in atmel_ecdh_compute_shared_secret() uses the
private key stored in the device. However, the public key is cached only
after atmel_ecdh_set_secret() successfully generated that private key
for the current tfm.

atmel_ecdh_generate_public_key() already rejects requests when no public
key is cached. Add the same check to atmel_ecdh_compute_shared_secret()
to prevent the device from using a private key that was not generated
for the current tfm.

Fixes: 11105693fa05 ("crypto: atmel-ecc - introduce Microchip / Atmel ECC driver")
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 drivers/crypto/atmel-ecc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/crypto/atmel-ecc.c b/drivers/crypto/atmel-ecc.c
index 93f219558c2f..542c8cc13a0f 100644
--- a/drivers/crypto/atmel-ecc.c
+++ b/drivers/crypto/atmel-ecc.c
@@ -173,6 +173,9 @@ static int atmel_ecdh_compute_shared_secret(struct kpp_request *req)
 		return crypto_kpp_compute_shared_secret(req);
 	}
 
+	if (!ctx->public_key)
+		return -EINVAL;
+
 	/* must have exactly two points to be on the curve */
 	if (req->src_len != ATMEL_ECC_PUBKEY_SIZE)
 		return -EINVAL;