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Subject: Re: [PATCH 10/11] nvmet-auth: implement support for augmented
 challenge
To:     =?UTF-8?Q?Stephan_M=c3=bcller?= <smueller@chronox.de>,
        Christoph Hellwig <hch@lst.de>
Cc:     Sagi Grimberg <sagi@grimberg.me>,
        Keith Busch <keith.busch@wdc.com>,
        linux-nvme@lists.infradead.org,
        Herbert Xu <herbert@gondor.apana.org.au>,
        "David S . Miller" <davem@davemloft.net>,
        linux-crypto@vger.kernel.org
References: <20210716110428.9727-1-hare@suse.de>
 <20210716110428.9727-11-hare@suse.de>
 <2653184.5eqXJjyf2G@positron.chronox.de>
From:   Hannes Reinecke <hare@suse.de>
Message-ID: <3cb2aefa-5320-81b4-f8c7-196161d73a77@suse.de>
Date:   Sun, 18 Jul 2021 14:25:57 +0200
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On 7/17/21 6:49 PM, Stephan Müller wrote:
> Am Freitag, 16. Juli 2021, 13:04:27 CEST schrieb Hannes Reinecke:
> 
> Hi Hannes,
> 
>> 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);
> 
> Alignment?
> 

With what?
And why?

>> +		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);
> 
> dto.

dto.

>> +		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;
>> +}
> 
> In general: the target/host authentication code looks very similar. Is there
> no way to have a common code base?

That is the plan, but I would need to rework the parameter passing for 
the target code to also use a 'dhchap' authentication block like the 
host code does.
But Sagi is not entirely happy with it, so I'll rework the code once we 
have consensus there.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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