[PATCH 03/10] nvme: add nvme_auth_generate_digest()

Hannes Reinecke
2024-12-02T14:30:17Z

Add a function to calculate the PSK digest as specified in TP8018.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
---
drivers/nvme/common/auth.c | 139 +++++++++++++++++++++++++++++++++++++
include/linux/nvme-auth.h | 2 +
2 files changed, 141 insertions(+)

diff --git a/drivers/nvme/common/auth.c b/drivers/nvme/common/auth.c
index 32a12899d0ce..12ce9125693f 100644
--- a/drivers/nvme/common/auth.c
+++ b/drivers/nvme/common/auth.c
@@ -569,5 +569,144 @@ int nvme_auth_generate_psk(u8 hmac_id, u8 *skey, size_t skey_len,
}
EXPORT_SYMBOL_GPL(nvme_auth_generate_psk);

+/**
+ * nvme_auth_generate_digest - Generate TLS PSK digest
+ * @hmac_id: Hash function identifier
+ * @psk: Generated input PSK
+ * @psk_len: Lenght of @psk
+ * @subsysnqn: NQN of the subsystem
+ * @hostnqn: NQN of the host
+ * @ret_digest: Pointer to the returned digest
+ *
+ * Generate a TLS PSK digest as specified in TP8018 Section 3.6.1.3:
+ * TLS PSK and PSK identity Derivation
+ *
+ * The PSK digest shall be computed by encoding in Base64 (refer to RFC 4648)
+ * the result of the application of the HMAC function using the hash function
+ * specified in item 4 above (ie the hash function of the cipher suite associated
+ * with the PSK identity) with the PSK as HMAC key to the concatenation of:
+ * - the NQN of the host (i.e., NQNh) not including the null terminator;
+ * - a space character;
+ * - the NQN of the NVM subsystem (i.e., NQNc) not including the null terminator;
+ * - a space character; and
+ * - the seventeen ASCII characters "NVMe-over-Fabrics"
+ * (i.e., <PSK digest> = Base64(HMAC(PSK, NQNh || " " || NQNc || " " || "NVMe-over-Fabrics"))).
+ * The length of the PSK digest depends on the hash function used to compute
+ * it as follows:
+ * - If the SHA-256 hash function is used, the resulting PSK digest is 44 characters long; or
+ * - If the SHA-384 hash function is used, the resulting PSK digest is 64 characters long.
+ *
+ * Returns 0 on success with a valid digest pointer in @ret_digest, or a negative
+ * error number on failure.
+ */
+int nvme_auth_generate_digest(u8 hmac_id, u8 *psk, size_t psk_len,
+ char *subsysnqn, char *hostnqn, u8 **ret_digest)
+{
+ struct crypto_shash *tfm;
+ struct shash_desc *shash;
+ u8 *digest, *enc;
+ const char *hmac_name;
+ size_t digest_len, hmac_len;
+ int ret;
+
+ if (WARN_ON(!subsysnqn || !hostnqn))
+ return -EINVAL;
+
+ hmac_name = nvme_auth_hmac_name(hmac_id);
+ if (!hmac_name) {
+ pr_warn("%s: invalid hash algorithm %d\n",
+ __func__, hmac_id);
+ return -EINVAL;
+ }
+
+ switch (nvme_auth_hmac_hash_len(hmac_id)) {
+ case 32:
+ hmac_len = 44;
+ break;
+ case 48:
+ hmac_len = 64;
+ break;
+ default:
+ pr_warn("%s: invalid hash algorithm '%s'\n",
+ __func__, hmac_name);
+ return -EINVAL;
+ }
+
+ enc = kzalloc(hmac_len + 1, GFP_KERNEL);
+ if (!enc)
+ return -ENOMEM;
+
+ tfm = crypto_alloc_shash(hmac_name, 0, 0);
+ if (IS_ERR(tfm)) {
+ ret = PTR_ERR(tfm);
+ goto out_free_enc;
+ }
+
+ digest_len = crypto_shash_digestsize(tfm);
+ digest = kzalloc(digest_len, GFP_KERNEL);
+ if (!digest) {
+ ret = -ENOMEM;
+ goto out_free_tfm;
+ }
+
+ shash = kmalloc(sizeof(struct shash_desc) +
+ crypto_shash_descsize(tfm),
+ GFP_KERNEL);
+ if (!shash) {
+ ret = -ENOMEM;
+ goto out_free_digest;
+ }
+
+ shash->tfm = tfm;
+ ret = crypto_shash_setkey(tfm, psk, psk_len);
+ if (ret)
+ goto out_free_shash;
+
+ ret = crypto_shash_init(shash);
+ if (ret)
+ goto out_free_shash;
+
+ ret = crypto_shash_update(shash, hostnqn, strlen(hostnqn));
+ if (ret)
+ goto out_free_shash;
+
+ ret = crypto_shash_update(shash, " ", 1);
+ if (ret)
+ goto out_free_shash;
+
+ ret = crypto_shash_update(shash, subsysnqn, strlen(subsysnqn));
+ if (ret)
+ goto out_free_shash;
+
+ ret = crypto_shash_update(shash, " NVMe-over-Fabrics", 18);
+ if (ret)
+ goto out_free_shash;
+
+ ret = crypto_shash_final(shash, digest);
+ if (ret)
+ goto out_free_shash;
+
+ ret = base64_encode(digest, digest_len, enc);
+ if (ret < hmac_len)
+ ret = -ENOKEY;
+ else {
+ *ret_digest = enc;
+ ret = 0;
+ }
+
+out_free_shash:
+ kfree_sensitive(shash);
+out_free_digest:
+ kfree_sensitive(digest);
+out_free_tfm:
+ crypto_free_shash(tfm);
+out_free_enc:
+ if (ret)
+ kfree_sensitive(enc);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_generate_digest);
+
MODULE_DESCRIPTION("NVMe Authentication framework");
MODULE_LICENSE("GPL v2");
diff --git a/include/linux/nvme-auth.h b/include/linux/nvme-auth.h
index b13884b04dfd..998f06bf10fd 100644
--- a/include/linux/nvme-auth.h
+++ b/include/linux/nvme-auth.h
@@ -43,5 +43,7 @@ int nvme_auth_gen_shared_secret(struct crypto_kpp *dh_tfm,
int nvme_auth_generate_psk(u8 hmac_id, u8 *skey, size_t skey_len,
u8 *c1, u8 *c2, size_t hash_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);

#endif /* _NVME_AUTH_H */
--
2.35.3