crypto: ecdh - explicitly zeroize private_key

From: Joachim Vandersmissen <[email protected]>

commit 73e5984e540a76a2ee1868b91590c922da8c24c9 upstream.

private_key is overwritten with the key parameter passed in by the caller (if present), or alternatively a newly generated private key. However, it is possible that the caller provides a key (or the newly generated key) which is shorter than the previous key. In that scenario, some key material from the previous key would not be overwritten. The easiest solution is to explicitly zeroize the entire private_key array first.

Note that this patch slightly changes the behavior of this function:
previously, if the ecc_gen_privkey failed, the old private_key would remain. Now, the private_key is always zeroized. This behavior is consistent with the case where params.key is set and ecc_is_key_valid fails.

Signed-off-by Joachim Vandersmissen <[email protected]>

Signed-off-by Herbert Xu <[email protected]>

[ Roman: The zeroing is performed before ecdh_supported_curve() which is not present in upstream but this does not change the fix's logic. ]

Signed-off-by Roman Demidov <[email protected]>

---
Backport fix for BDU:2025-00987

 crypto/ecdh.c | 2 ++
 1 file changed, 2 insertions(+)

crypto/ecdh.c +2 -0

index 96f80c8f8e30..2e7acfc42155 100644
@@ -43,6 +43,8 @@ static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
 	    params.key_size > sizeof(ctx->private_key))
 		return -EINVAL;
 
+	memset(ctx->private_key, 0, sizeof(ctx->private_key));
+
 	ndigits = ecdh_supported_curve(params.curve_id);
 	if (!ndigits)
 		return -EINVAL;

Signature · 1 line

2.53.0