[PATCH 10/11] nvmet-auth: implement support for augmented challenge

[Hannes Reinecke <hare@suse.de>]

Implement support for augmented challenge with FFDHE groups.
This patch adds a new configfs attribute 'dhchap_dhgroup' to
select the DH group to use.

Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/nvme/target/auth.c             | 241 ++++++++++++++++++++++++-
 drivers/nvme/target/configfs.c         |  31 ++++
 drivers/nvme/target/fabrics-cmd-auth.c |  14 +-
 3 files changed, 281 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/target/auth.c b/drivers/nvme/target/auth.c
index 00c7d051dfb1..cc7f12a7c8bf 100644
--- a/drivers/nvme/target/auth.c
+++ b/drivers/nvme/target/auth.c
@@ -58,11 +58,56 @@ int nvmet_auth_set_host_key(struct nvmet_host *host, const char *secret)
 
 int nvmet_setup_dhgroup(struct nvmet_ctrl *ctrl, int dhgroup_id)
 {
+	struct nvmet_host_link *p;
+	struct nvmet_host *host = NULL;
+	const char *dhgroup_kpp;
 	int ret = -ENOTSUPP;
 
 	if (dhgroup_id == NVME_AUTH_DHCHAP_DHGROUP_NULL)
 		return 0;
 
+	down_read(&nvmet_config_sem);
+	if (ctrl->subsys->type == NVME_NQN_DISC)
+		goto out_unlock;
+
+	list_for_each_entry(p, &ctrl->subsys->hosts, entry) {
+		if (strcmp(nvmet_host_name(p->host), ctrl->hostnqn))
+			continue;
+		host = p->host;
+		break;
+	}
+	if (!host) {
+		pr_debug("host %s not found\n", ctrl->hostnqn);
+		ret = -ENXIO;
+		goto out_unlock;
+	}
+
+	if (host->dhchap_dhgroup_id != dhgroup_id) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+	dhgroup_kpp = nvme_auth_dhgroup_kpp(dhgroup_id);
+	if (!dhgroup_kpp) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+	ctrl->dh_tfm = crypto_alloc_kpp(dhgroup_kpp, 0, 0);
+	if (IS_ERR(ctrl->dh_tfm)) {
+		pr_debug("failed to setup DH group %d, err %ld\n",
+			 dhgroup_id, PTR_ERR(ctrl->dh_tfm));
+		ret = PTR_ERR(ctrl->dh_tfm);
+		ctrl->dh_tfm = NULL;
+	} else {
+		ctrl->dh_gid = dhgroup_id;
+		ctrl->dh_keysize = nvme_auth_dhgroup_pubkey_size(dhgroup_id);
+		pr_debug("select DH group %d keysize %d\n",
+			 ctrl->dh_gid, ctrl->dh_keysize);
+		ret = 0;
+	}
+
+out_unlock:
+	up_read(&nvmet_config_sem);
+
 	return ret;
 }
 
@@ -192,6 +237,101 @@ bool nvmet_check_auth_status(struct nvmet_req *req)
 	return true;
 }
 
+static int nvmet_auth_hash_sesskey(struct nvmet_req *req, u8 *hashed_key)
+{
+	struct nvmet_ctrl *ctrl = req->sq->ctrl;
+	const char *hmac_name, *digest_name;
+	struct crypto_shash *tfm;
+	int hmac_id, ret;
+
+	if (!ctrl->shash_tfm) {
+		pr_debug("%s: hash alg not set\n", __func__);
+		return -EINVAL;
+	}
+	hmac_name = crypto_shash_alg_name(ctrl->shash_tfm);
+	hmac_id = nvme_auth_hmac_id(hmac_name);
+	if (hmac_id < 0) {
+		pr_debug("%s: unsupported hmac %s\n", __func__,
+			 hmac_name);
+		return -EINVAL;
+	}
+	digest_name = nvme_auth_digest_name(hmac_id);
+	if (!digest_name) {
+		pr_debug("%s: failed to get digest for %s\n", __func__,
+			 hmac_name);
+		return -EINVAL;
+	}
+	tfm = crypto_alloc_shash(digest_name, 0, 0);
+	if (IS_ERR(tfm))
+		return -ENOMEM;
+
+	ret = crypto_shash_tfm_digest(tfm, req->sq->dhchap_skey,
+				      req->sq->dhchap_skey_len, hashed_key);
+	if (ret < 0)
+		pr_debug("%s: Failed to hash digest len %d\n", __func__,
+			 req->sq->dhchap_skey_len);
+
+	crypto_free_shash(tfm);
+	return ret;
+}
+
+static int nvmet_auth_augmented_challenge(struct nvmet_req *req,
+					  u8 *challenge, u8 *aug)
+{
+	struct nvmet_ctrl *ctrl = req->sq->ctrl;
+	struct crypto_shash *tfm;
+	struct shash_desc *desc;
+	u8 *hashed_key;
+	const char *hash_name;
+	int hash_len = req->sq->dhchap_hash_len;
+	int ret;
+
+	hashed_key = kmalloc(hash_len, GFP_KERNEL);
+	if (!hashed_key)
+		return -ENOMEM;
+
+	ret = nvmet_auth_hash_sesskey(req, hashed_key);
+	if (ret < 0) {
+		pr_debug("failed to hash session key, err %d\n", ret);
+		kfree(hashed_key);
+		return ret;
+	}
+	hash_name = crypto_shash_alg_name(ctrl->shash_tfm);
+	if (!hash_name) {
+		pr_debug("Invalid hash algoritm\n");
+		return -EINVAL;
+	}
+	tfm = crypto_alloc_shash(hash_name, 0, 0);
+	if (IS_ERR(tfm)) {
+		ret = PTR_ERR(tfm);
+		goto out_free_key;
+	}
+	desc = kmalloc(sizeof(struct shash_desc) + crypto_shash_descsize(tfm),
+		       GFP_KERNEL);
+	if (!desc) {
+		ret = -ENOMEM;
+		goto out_free_hash;
+	}
+	desc->tfm = tfm;
+
+	ret = crypto_shash_setkey(tfm, hashed_key, hash_len);
+	if (ret)
+		goto out_free_desc;
+	ret = crypto_shash_init(desc);
+	if (ret)
+		goto out_free_desc;
+	crypto_shash_update(desc, challenge, hash_len);
+	crypto_shash_final(desc, aug);
+
+out_free_desc:
+	kfree_sensitive(desc);
+out_free_hash:
+	crypto_free_shash(tfm);
+out_free_key:
+	kfree(hashed_key);
+	return ret;
+}
+
 int nvmet_auth_host_hash(struct nvmet_req *req, u8 *response,
 			 unsigned int shash_len)
 {
@@ -202,8 +342,15 @@ int nvmet_auth_host_hash(struct nvmet_req *req, u8 *response,
 	int ret;
 
 	if (ctrl->dh_gid != NVME_AUTH_DHCHAP_DHGROUP_NULL) {
-		ret = -ENOTSUPP;
-		goto out;
+		challenge = kmalloc(shash_len, GFP_KERNEL);
+		if (!challenge) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		ret = nvmet_auth_augmented_challenge(req, req->sq->dhchap_c1,
+						     challenge);
+		if (ret)
+			goto out;
 	}
 
 	shash->tfm = ctrl->shash_tfm;
@@ -264,8 +411,15 @@ int nvmet_auth_ctrl_hash(struct nvmet_req *req, u8 *response,
 		 ctrl->cntlid, ctrl->hostnqn);
 
 	if (ctrl->dh_gid != NVME_AUTH_DHCHAP_DHGROUP_NULL) {
-		ret = -ENOTSUPP;
-		goto out;
+		challenge = kmalloc(shash_len, GFP_KERNEL);
+		if (!challenge) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		ret = nvmet_auth_augmented_challenge(req, req->sq->dhchap_c2,
+						     challenge);
+		if (ret)
+			goto out;
 	}
 
 	shash->tfm = ctrl->shash_tfm;
@@ -307,6 +461,85 @@ int nvmet_auth_ctrl_hash(struct nvmet_req *req, u8 *response,
 	return 0;
 }
 
+int nvmet_auth_ctrl_exponential(struct nvmet_req *req,
+				u8 *buf, int buf_size)
+{
+	struct nvmet_ctrl *ctrl = req->sq->ctrl;
+	struct kpp_request *kpp_req;
+	struct crypto_wait wait;
+	char *pkey;
+	struct scatterlist dst;
+	int ret, pkey_len;
+
+	if (ctrl->dh_gid == NVME_AUTH_DHCHAP_DHGROUP_2048 ||
+	    ctrl->dh_gid == NVME_AUTH_DHCHAP_DHGROUP_3072 ||
+	    ctrl->dh_gid == NVME_AUTH_DHCHAP_DHGROUP_4096 ||
+	    ctrl->dh_gid == NVME_AUTH_DHCHAP_DHGROUP_6144 ||
+	    ctrl->dh_gid == NVME_AUTH_DHCHAP_DHGROUP_8192) {
+		struct dh p = {0};
+		int bits = nvme_auth_dhgroup_pubkey_size(ctrl->dh_gid) << 3;
+
+		ret = crypto_ffdhe_params(&p, bits);
+		if (ret)
+			return ret;
+
+		p.key = ctrl->dhchap_key;
+		p.key_size = ctrl->dhchap_key_len;
+
+		pkey_len = crypto_dh_key_len(&p);
+		pkey = kmalloc(pkey_len, GFP_KERNEL);
+		if (!pkey)
+			return -ENOMEM;
+
+		get_random_bytes(pkey, pkey_len);
+		ret = crypto_dh_encode_key(pkey, pkey_len, &p);
+		if (ret) {
+			pr_debug("failed to encode private key, error %d\n",
+				 ret);
+			goto out;
+		}
+	} else {
+		pr_warn("invalid dh group %d\n", ctrl->dh_gid);
+		return -EINVAL;
+	}
+	ret = crypto_kpp_set_secret(ctrl->dh_tfm, pkey, pkey_len);
+	if (ret) {
+		pr_debug("failed to set private key, error %d\n", ret);
+		goto out;
+	}
+
+	kpp_req = kpp_request_alloc(ctrl->dh_tfm, GFP_KERNEL);
+	if (!kpp_req) {
+		pr_debug("cannot allocate kpp request\n");
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	crypto_init_wait(&wait);
+	kpp_request_set_input(kpp_req, NULL, 0);
+	sg_init_one(&dst, buf, buf_size);
+	kpp_request_set_output(kpp_req, &dst, buf_size);
+	kpp_request_set_callback(kpp_req, CRYPTO_TFM_REQ_MAY_BACKLOG,
+				 crypto_req_done, &wait);
+
+	ret = crypto_wait_req(crypto_kpp_generate_public_key(kpp_req), &wait);
+	kpp_request_free(kpp_req);
+	if (ret == -EOVERFLOW) {
+		pr_debug("public key buffer too small, need %d is %d\n",
+			 crypto_kpp_maxsize(ctrl->dh_tfm), buf_size);
+		ret = -ENOKEY;
+	} else if (ret) {
+		pr_debug("failed to generate public key, err %d\n", ret);
+		ret = -ENOKEY;
+	} else
+		pr_debug("%s: ctrl public key %*ph\n", __func__,
+			 (int)buf_size, buf);
+
+out:
+	kfree_sensitive(pkey);
+	return ret;
+}
+
 int nvmet_auth_ctrl_sesskey(struct nvmet_req *req,
 			    u8 *pkey, int pkey_size)
 {
diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index e0760911a761..e9b8884a83b0 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -1712,9 +1712,40 @@ static ssize_t nvmet_host_dhchap_hash_store(struct config_item *item,
 
 CONFIGFS_ATTR(nvmet_host_, dhchap_hash);
 
+static ssize_t nvmet_host_dhchap_dhgroup_show(struct config_item *item,
+		char *page)
+{
+	struct nvmet_host *host = to_host(item);
+	const char *dhgroup = nvme_auth_dhgroup_name(host->dhchap_dhgroup_id);
+
+	return sprintf(page, "%s\n", dhgroup ? dhgroup : "none");
+}
+
+static ssize_t nvmet_host_dhchap_dhgroup_store(struct config_item *item,
+		const char *page, size_t count)
+{
+	struct nvmet_host *host = to_host(item);
+	int dhgroup_id;
+
+	dhgroup_id = nvme_auth_dhgroup_id(page);
+	if (dhgroup_id < 0)
+		return -EINVAL;
+	if (dhgroup_id != NVME_AUTH_DHCHAP_DHGROUP_NULL) {
+		const char *kpp = nvme_auth_dhgroup_kpp(dhgroup_id);
+
+		if (!crypto_has_kpp(kpp, 0, 0))
+			return -EINVAL;
+	}
+	host->dhchap_dhgroup_id = dhgroup_id;
+	return count;
+}
+
+CONFIGFS_ATTR(nvmet_host_, dhchap_dhgroup);
+
 static struct configfs_attribute *nvmet_host_attrs[] = {
 	&nvmet_host_attr_dhchap_key,
 	&nvmet_host_attr_dhchap_hash,
+	&nvmet_host_attr_dhchap_dhgroup,
 	NULL,
 };
 #endif /* CONFIG_NVME_TARGET_AUTH */
diff --git a/drivers/nvme/target/fabrics-cmd-auth.c b/drivers/nvme/target/fabrics-cmd-auth.c
index 962f9f5e9d89..478ac351c645 100644
--- a/drivers/nvme/target/fabrics-cmd-auth.c
+++ b/drivers/nvme/target/fabrics-cmd-auth.c
@@ -98,7 +98,11 @@ static u16 nvmet_auth_reply(struct nvmet_req *req, void *d)
 		return NVME_AUTH_DHCHAP_FAILURE_INVALID_PAYLOAD;
 
 	if (data->dhvlen) {
-		return NVME_AUTH_DHCHAP_FAILURE_INVALID_PAYLOAD;
+		if (!ctrl->dh_tfm)
+			return NVME_AUTH_DHCHAP_FAILURE_INVALID_PAYLOAD;
+		if (nvmet_auth_ctrl_sesskey(req, data->rval + 2 * data->hl,
+					    data->dhvlen) < 0)
+			return NVME_AUTH_DHCHAP_FAILURE_DHGROUP_UNUSABLE;
 	}
 
 	response = kmalloc(data->hl, GFP_KERNEL);
@@ -299,6 +303,8 @@ static int nvmet_auth_challenge(struct nvmet_req *req, void *d, int al)
 	int ret = 0;
 	int data_size = sizeof(*d) + req->sq->dhchap_hash_len;
 
+	if (ctrl->dh_tfm)
+		data_size += ctrl->dh_keysize;
 	if (al < data_size) {
 		pr_debug("%s: buffer too small (al %d need %d)\n", __func__,
 			 al, data_size);
@@ -317,6 +323,12 @@ static int nvmet_auth_challenge(struct nvmet_req *req, void *d, int al)
 		return -ENOMEM;
 	get_random_bytes(req->sq->dhchap_c1, data->hl);
 	memcpy(data->cval, req->sq->dhchap_c1, data->hl);
+	if (ctrl->dh_tfm) {
+		data->dhgid = ctrl->dh_gid;
+		data->dhvlen = ctrl->dh_keysize;
+		ret = nvmet_auth_ctrl_exponential(req, data->cval + data->hl,
+						  data->dhvlen);
+	}
 	pr_debug("%s: ctrl %d qid %d seq %d transaction %d hl %d dhvlen %d\n",
 		 __func__, ctrl->cntlid, req->sq->qid, req->sq->dhchap_s1,
 		 req->sq->dhchap_tid, data->hl, data->dhvlen);
-- 
2.29.2