nvme-auth: common: add HMAC helper functions

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.

Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Keith Busch <kbusch@kernel.org>

2 files changed, 68 insertions, 0 deletions

diff --git a/drivers/nvme/common/Kconfig b/drivers/nvme/common/Kconfig
index d19988c13af5..1ec507d1f9b5 100644
--- a/drivers/nvme/common/Kconfig
+++ b/drivers/nvme/common/Kconfig
@@ -13,6 +13,8 @@ config NVME_AUTH
 	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
diff --git a/drivers/nvme/common/auth.c b/drivers/nvme/common/auth.c
index 9e33fc02cf51..00f21176181f 100644
--- a/drivers/nvme/common/auth.c
+++ b/drivers/nvme/common/auth.c
@@ -12,6 +12,7 @@
 #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>
 
@@ -234,6 +235,71 @@ void nvme_auth_free_key(struct nvme_dhchap_key *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)
 {