[PATCH 11/12] nvmet-auth: Diffie-Hellman key exchange support

Hannes Reinecke
2021-11-12T12:59:42Z

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>
---
drivers/nvme/target/Kconfig | 1 +
drivers/nvme/target/auth.c | 152 ++++++++++++++++++++++++-
drivers/nvme/target/configfs.c | 31 +++++
drivers/nvme/target/fabrics-cmd-auth.c | 19 +++-
drivers/nvme/target/nvmet.h | 8 ++
5 files changed, 203 insertions(+), 8 deletions(-)

diff --git a/drivers/nvme/target/Kconfig b/drivers/nvme/target/Kconfig
index 70f3c385fc9f..2e41d70fd881 100644
--- a/drivers/nvme/target/Kconfig
+++ b/drivers/nvme/target/Kconfig
@@ -90,6 +90,7 @@ config NVME_TARGET_AUTH
select CRYPTO_HMAC
select CRYPTO_SHA256
select CRYPTO_SHA512
+ select CRYPTO_FFDHE
help
This enables support for NVMe over Fabrics In-band Authentication

diff --git a/drivers/nvme/target/auth.c b/drivers/nvme/target/auth.c
index e63d12a0f446..7486077ca33e 100644
--- a/drivers/nvme/target/auth.c
+++ b/drivers/nvme/target/auth.c
@@ -69,6 +69,71 @@ int nvmet_auth_set_ctrl_key(struct nvmet_host *host, const char *secret)
return host->dhchap_ctrl_secret ? 0 : -ENOMEM;
}

+int nvmet_setup_dhgroup(struct nvmet_ctrl *ctrl, int dhgroup_id)
+{
+ const char *dhgroup_kpp;
+ int ret = 0;
+
+ pr_debug("%s: ctrl %d selecting dhgroup %d\n",
+ __func__, ctrl->cntlid, dhgroup_id);
+
+ if (ctrl->dh_tfm) {
+ if (ctrl->dh_gid == dhgroup_id) {
+ pr_debug("%s: ctrl %d reuse existing DH group %d\n",
+ __func__, ctrl->cntlid, dhgroup_id);
+ return 0;
+ }
+ crypto_free_kpp(ctrl->dh_tfm);
+ ctrl->dh_tfm = NULL;
+ ctrl->dh_gid = 0;
+ }
+
+ if (dhgroup_id == NVME_AUTH_DHCHAP_DHGROUP_NULL)
+ return 0;
+
+ dhgroup_kpp = nvme_auth_dhgroup_kpp(dhgroup_id);
+ if (!dhgroup_kpp) {
+ pr_debug("%s: ctrl %d invalid DH group %d\n",
+ __func__, ctrl->cntlid, dhgroup_id);
+ return -EINVAL;
+ }
+ ctrl->dh_tfm = crypto_alloc_kpp(dhgroup_kpp, 0, 0);
+ if (IS_ERR(ctrl->dh_tfm)) {
+ pr_debug("%s: ctrl %d failed to setup DH group %d, err %ld\n",
+ __func__, ctrl->cntlid, dhgroup_id,
+ PTR_ERR(ctrl->dh_tfm));
+ ret = PTR_ERR(ctrl->dh_tfm);
+ ctrl->dh_tfm = NULL;
+ ctrl->dh_gid = 0;
+ } else {
+ ctrl->dh_gid = dhgroup_id;
+ ctrl->dh_keysize = nvme_auth_dhgroup_pubkey_size(dhgroup_id);
+ pr_debug("%s: ctrl %d setup DH group %d\n",
+ __func__, ctrl->cntlid, ctrl->dh_gid);
+ ret = nvme_auth_gen_privkey(ctrl->dh_tfm, ctrl->dh_gid);
+ if (ret < 0)
+ pr_debug("%s: ctrl %d failed to generate private key, err %d\n",
+ __func__, ctrl->cntlid, ret);
+ kfree_sensitive(ctrl->dh_key);
+ ctrl->dh_key = kzalloc(ctrl->dh_keysize, GFP_KERNEL);
+ if (!ctrl->dh_key) {
+ pr_warn("ctrl %d failed to allocate public key\n",
+ ctrl->cntlid);
+ return -ENOMEM;
+ }
+ ret = nvme_auth_gen_pubkey(ctrl->dh_tfm, ctrl->dh_key,
+ ctrl->dh_keysize);
+ if (ret < 0) {
+ pr_warn("ctrl %d failed to generate public key\n",
+ ctrl->cntlid);
+ kfree(ctrl->dh_key);
+ ctrl->dh_key = NULL;
+ }
+ }
+
+ return ret;
+}
+
int nvmet_setup_auth(struct nvmet_ctrl *ctrl)
{
int ret = 0;
@@ -96,6 +161,10 @@ int nvmet_setup_auth(struct nvmet_ctrl *ctrl)
goto out_unlock;
}

+ ret = nvmet_setup_dhgroup(ctrl, host->dhchap_dhgroup_id);
+ if (ret < 0)
+ pr_warn("Failed to setup DH group");
+
if (!host->dhchap_secret) {
pr_debug("No authentication provided\n");
goto out_unlock;
@@ -180,6 +249,13 @@ void nvmet_destroy_auth(struct nvmet_ctrl *ctrl)
{
ctrl->shash_id = 0;

+ if (ctrl->dh_tfm) {
+ crypto_free_kpp(ctrl->dh_tfm);
+ ctrl->dh_tfm = NULL;
+ ctrl->dh_gid = 0;
+ }
+ kfree_sensitive(ctrl->dh_key);
+ ctrl->dh_key = NULL;
kfree_sensitive(ctrl->dhchap_key);
ctrl->dhchap_key = NULL;
kfree_sensitive(ctrl->dhchap_ctrl_key);
@@ -239,8 +315,18 @@ int nvmet_auth_host_hash(struct nvmet_req *req, u8 *response,
goto out_free_response;

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_free_response;
+ }
+ ret = nvme_auth_augmented_challenge(ctrl->shash_id,
+ req->sq->dhchap_skey,
+ req->sq->dhchap_skey_len,
+ req->sq->dhchap_c1,
+ challenge, shash_len);
+ if (ret)
+ goto out_free_response;
}

pr_debug("ctrl %d qid %d host response seq %d transaction %d\n",
@@ -343,8 +429,18 @@ int nvmet_auth_ctrl_hash(struct nvmet_req *req, u8 *response,
goto out_free_response;

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_free_response;
+ }
+ ret = nvme_auth_augmented_challenge(ctrl->shash_id,
+ req->sq->dhchap_skey,
+ req->sq->dhchap_skey_len,
+ req->sq->dhchap_c2,
+ challenge, shash_len);
+ if (ret)
+ goto out_free_response;
}

shash = kzalloc(sizeof(*shash) + crypto_shash_descsize(shash_tfm),
@@ -397,3 +493,51 @@ int nvmet_auth_ctrl_hash(struct nvmet_req *req, u8 *response,
crypto_free_shash(shash_tfm);
return 0;
}
+
+int nvmet_auth_ctrl_exponential(struct nvmet_req *req,
+ u8 *buf, int buf_size)
+{
+ struct nvmet_ctrl *ctrl = req->sq->ctrl;
+ int ret = 0;
+
+ if (!ctrl->dh_key) {
+ pr_warn("ctrl %d no DH public key!\n", ctrl->cntlid);
+ return -ENOKEY;
+ }
+ if (buf_size != ctrl->dh_keysize) {
+ pr_debug("%s: ctrl %d public key buffer size mismatch, need %d is %d\n",
+ __func__, ctrl->cntlid, ctrl->dh_keysize, buf_size);
+ ret = -EINVAL;
+ } else {
+ memcpy(buf, ctrl->dh_key, buf_size);
+ pr_debug("%s: ctrl %d public key %*ph\n", __func__,
+ ctrl->cntlid, (int)buf_size, buf);
+ }
+
+ return ret;
+}
+
+int nvmet_auth_ctrl_sesskey(struct nvmet_req *req,
+ u8 *pkey, int pkey_size)
+{
+ struct nvmet_ctrl *ctrl = req->sq->ctrl;
+ int ret;
+
+ req->sq->dhchap_skey_len =
+ nvme_auth_dhgroup_privkey_size(ctrl->dh_gid);
+ req->sq->dhchap_skey = kzalloc(req->sq->dhchap_skey_len, GFP_KERNEL);
+ if (!req->sq->dhchap_skey)
+ return -ENOMEM;
+ ret = nvme_auth_gen_shared_secret(ctrl->dh_tfm,
+ pkey, pkey_size,
+ req->sq->dhchap_skey,
+ req->sq->dhchap_skey_len);
+ if (ret)
+ pr_debug("failed to compute shared secred, err %d\n", ret);
+ else
+ pr_debug("%s: shared secret %*ph\n", __func__,
+ (int)req->sq->dhchap_skey_len,
+ req->sq->dhchap_skey);
+
+ return ret;
+}
diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index 38bafbc69714..1e272d0760ce 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -1784,10 +1784,41 @@ 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_ctrl_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 b5f46cdb97fe..51955fbc6c55 100644
--- a/drivers/nvme/target/fabrics-cmd-auth.c
+++ b/drivers/nvme/target/fabrics-cmd-auth.c
@@ -61,7 +61,7 @@ static u16 nvmet_auth_negotiate(struct nvmet_req *req, void *d)
data->auth_protocol[0].dhchap.dhlen; i++) {
int tmp_dhgid = data->auth_protocol[0].dhchap.idlist[i];

- if (tmp_dhgid == NVME_AUTH_DHCHAP_DHGROUP_NULL) {
+ if (tmp_dhgid != ctrl->dh_gid) {
dhgid = tmp_dhgid;
break;
}
@@ -71,7 +71,6 @@ static u16 nvmet_auth_negotiate(struct nvmet_req *req, void *d)
__func__, ctrl->cntlid, req->sq->qid);
return NVME_AUTH_DHCHAP_FAILURE_DHGROUP_UNUSABLE;
}
- ctrl->dh_gid = dhgid;
pr_debug("%s: ctrl %d qid %d: selected DH group %s (%d)\n",
__func__, ctrl->cntlid, req->sq->qid,
nvme_auth_dhgroup_name(ctrl->dh_gid), ctrl->dh_gid);
@@ -90,7 +89,11 @@ 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);
@@ -318,6 +321,8 @@ 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);
@@ -336,9 +341,15 @@ 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);
+ if (ctrl->dh_tfm) {
+ data->dhgid = ctrl->dh_gid;
+ data->dhvlen = cpu_to_le32(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 %d\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;
}

diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index ef1e7f7649c7..e2864310a048 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -230,7 +230,10 @@ struct nvmet_ctrl {
size_t dhchap_ctrl_key_len;
u8 dhchap_ctrl_key_hash;
u8 shash_id;
+ struct crypto_kpp *dh_tfm;
u32 dh_gid;
+ u8 *dh_key;
+ u32 dh_keysize;
#endif
};

@@ -705,6 +708,7 @@ int nvmet_setup_auth(struct nvmet_ctrl *ctrl);
void nvmet_init_auth(struct nvmet_ctrl *ctrl, struct nvmet_req *req);
void nvmet_destroy_auth(struct nvmet_ctrl *ctrl);
void nvmet_auth_sq_free(struct nvmet_sq *sq);
+int nvmet_setup_dhgroup(struct nvmet_ctrl *ctrl, int dhgroup_id);
bool nvmet_check_auth_status(struct nvmet_req *req);
int nvmet_auth_host_hash(struct nvmet_req *req, u8 *response,
unsigned int hash_len);
@@ -714,6 +718,10 @@ static inline bool nvmet_has_auth(struct nvmet_ctrl *ctrl)
{
return ctrl->dhchap_key != NULL;
}
+int nvmet_auth_ctrl_exponential(struct nvmet_req *req,
+ u8 *buf, int buf_size);
+int nvmet_auth_ctrl_sesskey(struct nvmet_req *req,
+ u8 *buf, int buf_size);
#else
static inline int nvmet_setup_auth(struct nvmet_ctrl *ctrl)
{
--
2.29.2