[PATCH 04/10] nvme: add nvme_auth_derive_tls_psk()

Hannes Reinecke
2024-12-03T11:15:02Z

Add a function to derive the TLS PSK as specified TP8018.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
---
drivers/nvme/common/Kconfig | 1 +
drivers/nvme/common/auth.c | 111 ++++++++++++++++++++++++++++++++++++
include/linux/nvme-auth.h | 2 +
3 files changed, 114 insertions(+)

diff --git a/drivers/nvme/common/Kconfig b/drivers/nvme/common/Kconfig
index 244432e0b73d..da963e4f3f1f 100644
--- a/drivers/nvme/common/Kconfig
+++ b/drivers/nvme/common/Kconfig
@@ -12,3 +12,4 @@ config NVME_AUTH
select CRYPTO_SHA512
select CRYPTO_DH
select CRYPTO_DH_RFC7919_GROUPS
+ select CRYPTO_HKDF
diff --git a/drivers/nvme/common/auth.c b/drivers/nvme/common/auth.c
index 12ce9125693f..9ea8b4aab739 100644
--- a/drivers/nvme/common/auth.c
+++ b/drivers/nvme/common/auth.c
@@ -15,6 +15,8 @@
#include <linux/nvme.h>
#include <linux/nvme-auth.h>

+#define HKDF_MAX_HASHLEN 64
+
static u32 nvme_dhchap_seqnum;
static DEFINE_MUTEX(nvme_dhchap_mutex);

@@ -708,5 +710,114 @@ int nvme_auth_generate_digest(u8 hmac_id, u8 *psk, size_t psk_len,
}
EXPORT_SYMBOL_GPL(nvme_auth_generate_digest);

+/**
+ * nvme_auth_derive_tls_psk - Derive TLS PSK
+ * @hmac_id: Hash function identifier
+ * @psk: generated input PSK
+ * @psk_len: size of @psk
+ * @psk_digest: TLS PSK digest
+ * @ret_psk: Pointer to the resulting TLS PSK
+ *
+ * Derive a TLS PSK as specified in TP8018 Section 3.6.1.3:
+ * TLS PSK and PSK identity Derivation
+ *
+ * The TLS PSK shall be derived as follows from an input PSK
+ * (i.e., either a retained PSK or a generated PSK) and a PSK
+ * identity using the HKDF-Extract and HKDF-Expand-Label operations
+ * (refer to RFC 5869 and RFC 8446) where the hash function is the
+ * one specified by the hash specifier of the PSK identity:
+ * 1. PRK = HKDF-Extract(0, Input PSK); and
+ * 2. TLS PSK = HKDF-Expand-Label(PRK, "nvme-tls-psk", PskIdentityContext, L),
+ * where PskIdentityContext is the hash identifier indicated in
+ * the PSK identity concatenated to a space character and to the
+ * Base64 PSK digest (i.e., "<hash> <PSK digest>") and L is the
+ * output size in bytes of the hash function (i.e., 32 for SHA-256
+ * and 48 for SHA-384).
+ *
+ * Returns 0 on success with a valid psk pointer in @ret_psk or a negative
+ * error number otherwise.
+ */
+int nvme_auth_derive_tls_psk(int hmac_id, u8 *psk, size_t psk_len,
+ u8 *psk_digest, u8 **ret_psk)
+{
+ struct crypto_shash *hmac_tfm;
+ const char *hmac_name;
+ const char *psk_prefix = "tls13 nvme-tls-psk";
+ static const char default_salt[HKDF_MAX_HASHLEN];
+ size_t info_len, prk_len;
+ char *info;
+ unsigned char *prk, *tls_key;
+ int ret;
+
+ hmac_name = nvme_auth_hmac_name(hmac_id);
+ if (!hmac_name) {
+ pr_warn("%s: invalid hash algorithm %d\n",
+ __func__, hmac_id);
+ return -EINVAL;
+ }
+ if (hmac_id == NVME_AUTH_HASH_SHA512) {
+ pr_warn("%s: unsupported hash algorithm %s\n",
+ __func__, hmac_name);
+ 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);
+ prk = kzalloc(prk_len, GFP_KERNEL);
+ if (!prk) {
+ ret = -ENOMEM;
+ goto out_free_shash;
+ }
+
+ if (WARN_ON(prk_len > HKDF_MAX_HASHLEN)) {
+ ret = -EINVAL;
+ goto out_free_prk;
+ }
+ ret = hkdf_extract(hmac_tfm, psk, psk_len,
+ default_salt, prk_len, prk);
+ if (ret)
+ goto out_free_prk;
+
+ ret = crypto_shash_setkey(hmac_tfm, prk, prk_len);
+ if (ret)
+ goto out_free_prk;
+
+ info_len = strlen(psk_digest) + strlen(psk_prefix) + 5;
+ info = kzalloc(info_len, GFP_KERNEL);
+ if (!info) {
+ ret = -ENOMEM;
+ goto out_free_prk;
+ }
+
+ put_unaligned_be16(psk_len, info);
+ memcpy(info + 2, psk_prefix, strlen(psk_prefix));
+ sprintf(info + 2 + strlen(psk_prefix), "%02d %s", hmac_id, psk_digest);
+
+ tls_key = kzalloc(psk_len, GFP_KERNEL);
+ if (!tls_key) {
+ ret = -ENOMEM;
+ goto out_free_info;
+ }
+ ret = hkdf_expand(hmac_tfm, info, strlen(info), tls_key, psk_len);
+ if (ret) {
+ kfree(tls_key);
+ goto out_free_info;
+ }
+ *ret_psk = tls_key;
+
+out_free_info:
+ kfree(info);
+out_free_prk:
+ kfree(prk);
+out_free_shash:
+ crypto_free_shash(hmac_tfm);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_derive_tls_psk);
+
MODULE_DESCRIPTION("NVMe Authentication framework");
MODULE_LICENSE("GPL v2");
diff --git a/include/linux/nvme-auth.h b/include/linux/nvme-auth.h
index 998f06bf10fd..60e069a6757f 100644
--- a/include/linux/nvme-auth.h
+++ b/include/linux/nvme-auth.h
@@ -45,5 +45,7 @@ int nvme_auth_generate_psk(u8 hmac_id, u8 *skey, size_t skey_len,
u8 **ret_psk, size_t *ret_len);
int nvme_auth_generate_digest(u8 hmac_id, u8 *psk, size_t psk_len,
char *subsysnqn, char *hostnqn, u8 **ret_digest);
+int nvme_auth_derive_tls_psk(int hmac_id, u8 *psk, size_t psk_len,
+ u8 *psk_digest, u8 **ret_psk);

#endif /* _NVME_AUTH_H */
--
2.35.3