nvmet-auth: Diffie-Hellman key exchange support

Implement Diffie-Hellman key exchange using FFDHE groups for NVMe
In-Band Authentication.
This patch adds a new host configfs attribute 'dhchap_dhgroup' to
select the FFDHE group to use.

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>

1 files changed, 33 insertions, 8 deletions

diff --git a/drivers/nvme/target/fabrics-cmd-auth.c b/drivers/nvme/target/fabrics-cmd-auth.c
index 776073a10e04..5b1be7e607e2 100644
--- a/drivers/nvme/target/fabrics-cmd-auth.c
+++ b/drivers/nvme/target/fabrics-cmd-auth.c
@@ -27,7 +27,7 @@ static u16 nvmet_auth_negotiate(struct nvmet_req *req, void *d)
 {
 	struct nvmet_ctrl *ctrl = req->sq->ctrl;
 	struct nvmf_auth_dhchap_negotiate_data *data = d;
-	int i, hash_id = 0, fallback_hash_id = 0, dhgid;
+	int i, hash_id = 0, fallback_hash_id = 0, dhgid, fallback_dhgid;
 
 	pr_debug("%s: ctrl %d qid %d: data sc_d %d napd %d authid %d halen %d dhlen %d\n",
 		 __func__, ctrl->cntlid, req->sq->qid,
@@ -69,22 +69,35 @@ static u16 nvmet_auth_negotiate(struct nvmet_req *req, void *d)
 	}
 
 	dhgid = -1;
+	fallback_dhgid = -1;
 	for (i = 0; i < data->auth_protocol[0].dhchap.dhlen; i++) {
 		int tmp_dhgid = data->auth_protocol[0].dhchap.idlist[i + 30];
 
-		if (tmp_dhgid == NVME_AUTH_DHGROUP_NULL) {
+		if (tmp_dhgid != ctrl->dh_gid) {
 			dhgid = tmp_dhgid;
 			break;
 		}
+		if (fallback_dhgid < 0) {
+			const char *kpp = nvme_auth_dhgroup_kpp(tmp_dhgid);
+
+			if (crypto_has_kpp(kpp, 0, 0))
+				fallback_dhgid = tmp_dhgid;
+		}
 	}
 	if (dhgid < 0) {
-		pr_debug("%s: ctrl %d qid %d: no usable DH group found\n",
+		if (fallback_dhgid < 0) {
+			pr_debug("%s: ctrl %d qid %d: no usable DH group found\n",
 				 __func__, ctrl->cntlid, req->sq->qid);
-		return NVME_AUTH_DHCHAP_FAILURE_DHGROUP_UNUSABLE;
+			return NVME_AUTH_DHCHAP_FAILURE_DHGROUP_UNUSABLE;
+		}
+		pr_debug("%s: ctrl %d qid %d: configured DH group %s not found\n",
+			 __func__, ctrl->cntlid, req->sq->qid,
+			 nvme_auth_dhgroup_name(fallback_dhgid));
+		ctrl->dh_gid = fallback_dhgid;
 	}
 	pr_debug("%s: ctrl %d qid %d: selected DH group %s (%d)\n",
 		 __func__, ctrl->cntlid, req->sq->qid,
-		 nvme_auth_dhgroup_name(dhgid), dhgid);
+		 nvme_auth_dhgroup_name(ctrl->dh_gid), ctrl->dh_gid);
 	return 0;
 }
 
@@ -100,7 +113,11 @@ static u16 nvmet_auth_reply(struct nvmet_req *req, void *d)
 		 data->hl, data->cvalid, dhvlen);
 
 	if (dhvlen) {
-		return NVME_AUTH_DHCHAP_FAILURE_INCORRECT_PAYLOAD;
+		if (!ctrl->dh_tfm)
+			return NVME_AUTH_DHCHAP_FAILURE_INCORRECT_PAYLOAD;
+		if (nvmet_auth_ctrl_sesskey(req, data->rval + 2 * data->hl,
+					    dhvlen) < 0)
+			return NVME_AUTH_DHCHAP_FAILURE_DHGROUP_UNUSABLE;
 	}
 
 	response = kmalloc(data->hl, GFP_KERNEL);
@@ -332,6 +349,8 @@ static int nvmet_auth_challenge(struct nvmet_req *req, void *d, int al)
 	int hash_len = nvme_auth_hmac_hash_len(ctrl->shash_id);
 	int data_size = sizeof(*d) + 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);
@@ -350,9 +369,15 @@ 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);
-	pr_debug("%s: ctrl %d qid %d seq %u transaction %d hl %d dhvlen %u\n",
+	if (ctrl->dh_tfm) {
+		data->dhgid = ctrl->dh_gid;
+		data->dhvlen = cpu_to_le16(ctrl->dh_keysize);
+		ret = nvmet_auth_ctrl_exponential(req, data->cval + data->hl,
+						  ctrl->dh_keysize);
+	}
+	pr_debug("%s: ctrl %d qid %d seq %d transaction %d hl %d dhvlen %zu\n",
 		 __func__, ctrl->cntlid, req->sq->qid, req->sq->dhchap_s1,
-		 req->sq->dhchap_tid, data->hl, 0);
+		 req->sq->dhchap_tid, data->hl, ctrl->dh_keysize);
 	return ret;
 }