[PATCH 07/21] nvme-auth: common: add HMAC helper functions

Eric Biggers
2026-03-02T08:01:28Z

Add some helper functions for computing HMAC-SHA256, HMAC-SHA384, or
HMAC-SHA512 values using the crypto library instead of crypto_shash.
These will enable some significant simplifications and performance
improvements in nvme-auth.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
drivers/nvme/common/Kconfig | 2 ++
drivers/nvme/common/auth.c | 66 +++++++++++++++++++++++++++++++++++++
include/linux/nvme-auth.h | 14 ++++++++
3 files changed, 82 insertions(+)

diff --git a/drivers/nvme/common/Kconfig b/drivers/nvme/common/Kconfig
index d19988c13af5f..1ec507d1f9b5f 100644
--- a/drivers/nvme/common/Kconfig
+++ b/drivers/nvme/common/Kconfig
@@ -11,10 +11,12 @@ config NVME_AUTH
select CRYPTO_SHA256
select CRYPTO_SHA512
select CRYPTO_DH
select CRYPTO_DH_RFC7919_GROUPS
select CRYPTO_HKDF
+ select CRYPTO_LIB_SHA256
+ select CRYPTO_LIB_SHA512

config NVME_AUTH_KUNIT_TEST
tristate "KUnit tests for NVMe authentication" if !KUNIT_ALL_TESTS
depends on KUNIT && NVME_AUTH
default KUNIT_ALL_TESTS
diff --git a/drivers/nvme/common/auth.c b/drivers/nvme/common/auth.c
index 9e33fc02cf51a..00f21176181f6 100644
--- a/drivers/nvme/common/auth.c
+++ b/drivers/nvme/common/auth.c
@@ -10,10 +10,11 @@
#include <linux/scatterlist.h>
#include <linux/unaligned.h>
#include <crypto/hash.h>
#include <crypto/dh.h>
#include <crypto/hkdf.h>
+#include <crypto/sha2.h>
#include <linux/nvme.h>
#include <linux/nvme-auth.h>

static u32 nvme_dhchap_seqnum;
static DEFINE_MUTEX(nvme_dhchap_mutex);
@@ -232,10 +233,75 @@ void nvme_auth_free_key(struct nvme_dhchap_key *key)
return;
kfree_sensitive(key);
}
EXPORT_SYMBOL_GPL(nvme_auth_free_key);

+/*
+ * Start computing an HMAC value, given the algorithm ID and raw key.
+ *
+ * The context should be zeroized at the end of its lifetime. The caller can do
+ * that implicitly by calling nvme_auth_hmac_final(), or explicitly (needed when
+ * a context is abandoned without finalizing it) by calling memzero_explicit().
+ */
+int nvme_auth_hmac_init(struct nvme_auth_hmac_ctx *hmac, u8 hmac_id,
+ const u8 *key, size_t key_len)
+{
+ hmac->hmac_id = hmac_id;
+ switch (hmac_id) {
+ case NVME_AUTH_HASH_SHA256:
+ hmac_sha256_init_usingrawkey(&hmac->sha256, key, key_len);
+ return 0;
+ case NVME_AUTH_HASH_SHA384:
+ hmac_sha384_init_usingrawkey(&hmac->sha384, key, key_len);
+ return 0;
+ case NVME_AUTH_HASH_SHA512:
+ hmac_sha512_init_usingrawkey(&hmac->sha512, key, key_len);
+ return 0;
+ }
+ pr_warn("%s: invalid hash algorithm %d\n", __func__, hmac_id);
+ return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_hmac_init);
+
+void nvme_auth_hmac_update(struct nvme_auth_hmac_ctx *hmac, const u8 *data,
+ size_t data_len)
+{
+ switch (hmac->hmac_id) {
+ case NVME_AUTH_HASH_SHA256:
+ hmac_sha256_update(&hmac->sha256, data, data_len);
+ return;
+ case NVME_AUTH_HASH_SHA384:
+ hmac_sha384_update(&hmac->sha384, data, data_len);
+ return;
+ case NVME_AUTH_HASH_SHA512:
+ hmac_sha512_update(&hmac->sha512, data, data_len);
+ return;
+ }
+ /* Unreachable because nvme_auth_hmac_init() validated hmac_id */
+ WARN_ON_ONCE(1);
+}
+EXPORT_SYMBOL_GPL(nvme_auth_hmac_update);
+
+/* Finish computing an HMAC value. Note that this zeroizes the HMAC context. */
+void nvme_auth_hmac_final(struct nvme_auth_hmac_ctx *hmac, u8 *out)
+{
+ switch (hmac->hmac_id) {
+ case NVME_AUTH_HASH_SHA256:
+ hmac_sha256_final(&hmac->sha256, out);
+ return;
+ case NVME_AUTH_HASH_SHA384:
+ hmac_sha384_final(&hmac->sha384, out);
+ return;
+ case NVME_AUTH_HASH_SHA512:
+ hmac_sha512_final(&hmac->sha512, out);
+ return;
+ }
+ /* Unreachable because nvme_auth_hmac_init() validated hmac_id */
+ WARN_ON_ONCE(1);
+}
+EXPORT_SYMBOL_GPL(nvme_auth_hmac_final);
+
struct nvme_dhchap_key *nvme_auth_transform_key(
const struct nvme_dhchap_key *key, const char *nqn)
{
const char *hmac_name;
struct crypto_shash *key_tfm;
diff --git a/include/linux/nvme-auth.h b/include/linux/nvme-auth.h
index 02ca9a7162565..940d0703eb1df 100644
--- a/include/linux/nvme-auth.h
+++ b/include/linux/nvme-auth.h
@@ -5,10 +5,11 @@

#ifndef _NVME_AUTH_H
#define _NVME_AUTH_H

#include <crypto/kpp.h>
+#include <crypto/sha2.h>

struct nvme_dhchap_key {
size_t len;
u8 hash;
u8 key[];
@@ -21,10 +22,23 @@ u8 nvme_auth_dhgroup_id(const char *dhgroup_name);

const char *nvme_auth_hmac_name(u8 hmac_id);
const char *nvme_auth_digest_name(u8 hmac_id);
size_t nvme_auth_hmac_hash_len(u8 hmac_id);
u8 nvme_auth_hmac_id(const char *hmac_name);
+struct nvme_auth_hmac_ctx {
+ u8 hmac_id;
+ union {
+ struct hmac_sha256_ctx sha256;
+ struct hmac_sha384_ctx sha384;
+ struct hmac_sha512_ctx sha512;
+ };
+};
+int nvme_auth_hmac_init(struct nvme_auth_hmac_ctx *hmac, u8 hmac_id,
+ const u8 *key, size_t key_len);
+void nvme_auth_hmac_update(struct nvme_auth_hmac_ctx *hmac, const u8 *data,
+ size_t data_len);
+void nvme_auth_hmac_final(struct nvme_auth_hmac_ctx *hmac, u8 *out);

u32 nvme_auth_key_struct_size(u32 key_len);
struct nvme_dhchap_key *nvme_auth_extract_key(const char *secret, u8 key_hash);
void nvme_auth_free_key(struct nvme_dhchap_key *key);
struct nvme_dhchap_key *nvme_auth_alloc_key(u32 len, u8 hash);
--
2.53.0