linux-kernel - [PATCH RFC] crypto/hkdf: Skip tests with keys too short in FIPS mode

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Message-ID: <20251205113136.17920-1-litian@redhat.com>
Date: Fri,  5 Dec 2025 19:31:36 +0800
From: Li Tian <litian@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-crypto@...r.kernel.org,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Eric Biggers <ebiggers@...nel.org>,
	"David S . Miller" <davem@...emloft.net>,
	Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: [PATCH RFC] crypto/hkdf: Skip tests with keys too short in FIPS mode

FIPS mode mandates the keys to _setkey should be longer than 14 bytes.
It's up to the callers to not use keys too short.

Signed-off-by: Li Tian <litian@...hat.com>
---
 crypto/hkdf.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/crypto/hkdf.c b/crypto/hkdf.c
index 82d1b32ca6ce..73d318f3f677 100644
--- a/crypto/hkdf.c
+++ b/crypto/hkdf.c
@@ -10,6 +10,7 @@
 #include <crypto/internal/hash.h>
 #include <crypto/sha2.h>
 #include <crypto/hkdf.h>
+#include <linux/fips.h>
 #include <linux/module.h>
 
 /*
@@ -462,7 +463,12 @@ static const struct hkdf_testvec hkdf_sha512_tv[] = {
 };
 
 static int hkdf_test(const char *shash, const struct hkdf_testvec *tv)
-{	struct crypto_shash *tfm = NULL;
+{
+	/* Skip the tests with keys too short in FIPS mode */
+	if (fips_enabled && (tv->salt_size < 112 / 8))
+		return 0;
+
+	struct crypto_shash *tfm = NULL;
 	u8 *prk = NULL, *okm = NULL;
 	unsigned int prk_size;
 	const char *driver;
-- 
2.50.0