nvmet: implement basic In-Band Authentication

Implement NVMe-oF In-Band authentication according to NVMe TPAR 8006.
This patch adds three additional configfs entries 'dhchap_key',
'dhchap_ctrl_key', and 'dhchap_hash' to the 'host' configfs directory.
The 'dhchap_key' and 'dhchap_ctrl_key' entries need to be in the ASCII
format as specified in NVMe Base Specification v2.0 section 8.13.5.8
'Secret representation'.
'dhchap_hash' defaults to 'hmac(sha256)', and can be written to to
switch to a different HMAC algorithm.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/nvme/target/configfs.c

@@ -11,6 +11,11 @@
 #include <linux/ctype.h>
 #include <linux/pci.h>
 #include <linux/pci-p2pdma.h>
+#ifdef CONFIG_NVME_TARGET_AUTH
+#include <linux/nvme-auth.h>
+#endif
+#include <crypto/hash.h>
+#include <crypto/kpp.h>
 
 #include "nvmet.h"
 
@@ -1680,10 +1685,102 @@ static const struct config_item_type nvmet_ports_type = {
 static struct config_group nvmet_subsystems_group;
 static struct config_group nvmet_ports_group;
 
+#ifdef CONFIG_NVME_TARGET_AUTH
+static ssize_t nvmet_host_dhchap_key_show(struct config_item *item,
+		char *page)
+{
+	u8 *dhchap_secret = to_host(item)->dhchap_secret;
+
+	if (!dhchap_secret)
+		return sprintf(page, "\n");
+	return sprintf(page, "%s\n", dhchap_secret);
+}
+
+static ssize_t nvmet_host_dhchap_key_store(struct config_item *item,
+		const char *page, size_t count)
+{
+	struct nvmet_host *host = to_host(item);
+	int ret;
+
+	ret = nvmet_auth_set_key(host, page, false);
+	/*
+	 * Re-authentication is a soft state, so keep the
+	 * current authentication valid until the host
+	 * requests re-authentication.
+	 */
+	return ret < 0 ? ret : count;
+}
+
+CONFIGFS_ATTR(nvmet_host_, dhchap_key);
+
+static ssize_t nvmet_host_dhchap_ctrl_key_show(struct config_item *item,
+		char *page)
+{
+	u8 *dhchap_secret = to_host(item)->dhchap_ctrl_secret;
+
+	if (!dhchap_secret)
+		return sprintf(page, "\n");
+	return sprintf(page, "%s\n", dhchap_secret);
+}
+
+static ssize_t nvmet_host_dhchap_ctrl_key_store(struct config_item *item,
+		const char *page, size_t count)
+{
+	struct nvmet_host *host = to_host(item);
+	int ret;
+
+	ret = nvmet_auth_set_key(host, page, true);
+	/*
+	 * Re-authentication is a soft state, so keep the
+	 * current authentication valid until the host
+	 * requests re-authentication.
+	 */
+	return ret < 0 ? ret : count;
+}
+
+CONFIGFS_ATTR(nvmet_host_, dhchap_ctrl_key);
+
+static ssize_t nvmet_host_dhchap_hash_show(struct config_item *item,
+		char *page)
+{
+	struct nvmet_host *host = to_host(item);
+	const char *hash_name = nvme_auth_hmac_name(host->dhchap_hash_id);
+
+	return sprintf(page, "%s\n", hash_name ? hash_name : "none");
+}
+
+static ssize_t nvmet_host_dhchap_hash_store(struct config_item *item,
+		const char *page, size_t count)
+{
+	struct nvmet_host *host = to_host(item);
+	u8 hmac_id;
+
+	hmac_id = nvme_auth_hmac_id(page);
+	if (hmac_id == NVME_AUTH_HASH_INVALID)
+		return -EINVAL;
+	if (!crypto_has_shash(nvme_auth_hmac_name(hmac_id), 0, 0))
+		return -ENOTSUPP;
+	host->dhchap_hash_id = hmac_id;
+	return count;
+}
+
+CONFIGFS_ATTR(nvmet_host_, dhchap_hash);
+
+static struct configfs_attribute *nvmet_host_attrs[] = {
+	&nvmet_host_attr_dhchap_key,
+	&nvmet_host_attr_dhchap_ctrl_key,
+	&nvmet_host_attr_dhchap_hash,
+	NULL,
+};
+#endif /* CONFIG_NVME_TARGET_AUTH */
+
 static void nvmet_host_release(struct config_item *item)
 {
 	struct nvmet_host *host = to_host(item);
-
+#ifdef CONFIG_NVME_TARGET_AUTH
+	if (host->dhchap_secret)
+		kfree(host->dhchap_secret);
+#endif
 	kfree(host);
 }
 
@@ -1693,6 +1790,9 @@ static struct configfs_item_operations nvmet_host_item_ops = {
 
 static const struct config_item_type nvmet_host_type = {
 	.ct_item_ops		= &nvmet_host_item_ops,
+#ifdef CONFIG_NVME_TARGET_AUTH
+	.ct_attrs		= nvmet_host_attrs,
+#endif
 	.ct_owner		= THIS_MODULE,
 };
 
@@ -1705,6 +1805,11 @@ static struct config_group *nvmet_hosts_make_group(struct config_group *group,
 	if (!host)
 		return ERR_PTR(-ENOMEM);
 
+#ifdef CONFIG_NVME_TARGET_AUTH
+	/* Default to SHA256 */
+	host->dhchap_hash_id = NVME_AUTH_HASH_SHA256;
+#endif
+
 	config_group_init_type_name(&host->group, name, &nvmet_host_type);
 
 	return &host->group;