[PATCH 06/21] nvme-auth: common: explicitly verify psk_len == hash_len

[Eric Biggers <ebiggers@kernel.org>]

nvme_auth_derive_tls_psk() is always called with psk_len == hash_len.
And based on the comments above nvme_auth_generate_psk() and
nvme_auth_derive_tls_psk(), this isn't an implementation choice but
rather just the length the spec uses.  Add a check which makes this
explicit, so that when cleaning up nvme_auth_derive_tls_psk() we don't
have to retain support for arbitrary values of psk_len.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
 drivers/nvme/common/auth.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/nvme/common/auth.c b/drivers/nvme/common/auth.c
index 2f83c9ddea5ec..9e33fc02cf51a 100644
--- a/drivers/nvme/common/auth.c
+++ b/drivers/nvme/common/auth.c
@@ -786,10 +786,15 @@ int nvme_auth_derive_tls_psk(int hmac_id, const u8 *psk, size_t psk_len,
 		pr_warn("%s: unsupported hash algorithm %s\n",
 			__func__, hmac_name);
 		return -EINVAL;
 	}
 
+	if (psk_len != nvme_auth_hmac_hash_len(hmac_id)) {
+		pr_warn("%s: unexpected psk_len %zu\n", __func__, psk_len);
+		return -EINVAL;
+	}
+
 	hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0);
 	if (IS_ERR(hmac_tfm))
 		return PTR_ERR(hmac_tfm);
 
 	prk_len = crypto_shash_digestsize(hmac_tfm);
-- 
2.53.0