nvme: implement In-Band authentication

Implement NVMe-oF In-Band authentication according to NVMe TPAR 8006.
This patch adds two new fabric options 'dhchap_secret' to specify the
pre-shared key (in ASCII respresentation according to NVMe 2.0 section
8.13.5.8 'Secret representation') and 'dhchap_ctrl_secret' to specify
the pre-shared controller key for bi-directional authentication of both
the host and the controller.
Re-authentication can be triggered by writing the PSK into the new
controller sysfs attribute 'dhchap_secret' or 'dhchap_ctrl_secret'.

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

3 files changed, 334 insertions, 0 deletions

diff --git a/drivers/nvme/common/Kconfig b/drivers/nvme/common/Kconfig
new file mode 100644
index 000000000000..4514f44362dd
--- /dev/null
+++ b/drivers/nvme/common/Kconfig
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+config NVME_COMMON
+       tristate
diff --git a/drivers/nvme/common/Makefile b/drivers/nvme/common/Makefile
new file mode 100644
index 000000000000..720c625b8a52
--- /dev/null
+++ b/drivers/nvme/common/Makefile
@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0
+
+ccflags-y			+= -I$(src)
+
+obj-$(CONFIG_NVME_COMMON)	+= nvme-common.o
+
+nvme-common-y			+= auth.o
diff --git a/drivers/nvme/common/auth.c b/drivers/nvme/common/auth.c
new file mode 100644
index 000000000000..adb43d341ffb
--- /dev/null
+++ b/drivers/nvme/common/auth.c
@@ -0,0 +1,323 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2020 Hannes Reinecke, SUSE Linux
+ */
+
+#include <linux/module.h>
+#include <linux/crc32.h>
+#include <linux/base64.h>
+#include <linux/prandom.h>
+#include <linux/scatterlist.h>
+#include <asm/unaligned.h>
+#include <crypto/hash.h>
+#include <crypto/dh.h>
+#include <linux/nvme.h>
+#include <linux/nvme-auth.h>
+
+static u32 nvme_dhchap_seqnum;
+static DEFINE_MUTEX(nvme_dhchap_mutex);
+
+u32 nvme_auth_get_seqnum(void)
+{
+	u32 seqnum;
+
+	mutex_lock(&nvme_dhchap_mutex);
+	if (!nvme_dhchap_seqnum)
+		nvme_dhchap_seqnum = prandom_u32();
+	else {
+		nvme_dhchap_seqnum++;
+		if (!nvme_dhchap_seqnum)
+			nvme_dhchap_seqnum++;
+	}
+	seqnum = nvme_dhchap_seqnum;
+	mutex_unlock(&nvme_dhchap_mutex);
+	return seqnum;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_get_seqnum);
+
+static struct nvme_auth_dhgroup_map {
+	const char name[16];
+	const char kpp[16];
+} dhgroup_map[] = {
+	[NVME_AUTH_DHGROUP_NULL] = {
+		.name = "null", .kpp = "null" },
+	[NVME_AUTH_DHGROUP_2048] = {
+		.name = "ffdhe2048", .kpp = "ffdhe2048(dh)" },
+	[NVME_AUTH_DHGROUP_3072] = {
+		.name = "ffdhe3072", .kpp = "ffdhe3072(dh)" },
+	[NVME_AUTH_DHGROUP_4096] = {
+		.name = "ffdhe4096", .kpp = "ffdhe4096(dh)" },
+	[NVME_AUTH_DHGROUP_6144] = {
+		.name = "ffdhe6144", .kpp = "ffdhe6144(dh)" },
+	[NVME_AUTH_DHGROUP_8192] = {
+		.name = "ffdhe8192", .kpp = "ffdhe8192(dh)" },
+};
+
+const char *nvme_auth_dhgroup_name(u8 dhgroup_id)
+{
+	if (dhgroup_id > ARRAY_SIZE(dhgroup_map))
+		return NULL;
+	return dhgroup_map[dhgroup_id].name;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_dhgroup_name);
+
+const char *nvme_auth_dhgroup_kpp(u8 dhgroup_id)
+{
+	if (dhgroup_id > ARRAY_SIZE(dhgroup_map))
+		return NULL;
+	return dhgroup_map[dhgroup_id].kpp;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_dhgroup_kpp);
+
+u8 nvme_auth_dhgroup_id(const char *dhgroup_name)
+{
+	int i;
+
+	if (!dhgroup_name || !strlen(dhgroup_name))
+		return NVME_AUTH_DHGROUP_INVALID;
+	for (i = 0; i < ARRAY_SIZE(dhgroup_map); i++) {
+		if (!strlen(dhgroup_map[i].name))
+			continue;
+		if (!strncmp(dhgroup_map[i].name, dhgroup_name,
+			     strlen(dhgroup_map[i].name)))
+			return i;
+	}
+	return NVME_AUTH_DHGROUP_INVALID;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_dhgroup_id);
+
+static struct nvme_dhchap_hash_map {
+	int len;
+	const char hmac[15];
+	const char digest[8];
+} hash_map[] = {
+	[NVME_AUTH_HASH_SHA256] = {
+		.len = 32,
+		.hmac = "hmac(sha256)",
+		.digest = "sha256",
+	},
+	[NVME_AUTH_HASH_SHA384] = {
+		.len = 48,
+		.hmac = "hmac(sha384)",
+		.digest = "sha384",
+	},
+	[NVME_AUTH_HASH_SHA512] = {
+		.len = 64,
+		.hmac = "hmac(sha512)",
+		.digest = "sha512",
+	},
+};
+
+const char *nvme_auth_hmac_name(u8 hmac_id)
+{
+	if (hmac_id > ARRAY_SIZE(hash_map))
+		return NULL;
+	return hash_map[hmac_id].hmac;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_hmac_name);
+
+const char *nvme_auth_digest_name(u8 hmac_id)
+{
+	if (hmac_id > ARRAY_SIZE(hash_map))
+		return NULL;
+	return hash_map[hmac_id].digest;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_digest_name);
+
+u8 nvme_auth_hmac_id(const char *hmac_name)
+{
+	int i;
+
+	if (!hmac_name || !strlen(hmac_name))
+		return NVME_AUTH_HASH_INVALID;
+
+	for (i = 0; i < ARRAY_SIZE(hash_map); i++) {
+		if (!strlen(hash_map[i].hmac))
+			continue;
+		if (!strncmp(hash_map[i].hmac, hmac_name,
+			     strlen(hash_map[i].hmac)))
+			return i;
+	}
+	return NVME_AUTH_HASH_INVALID;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_hmac_id);
+
+size_t nvme_auth_hmac_hash_len(u8 hmac_id)
+{
+	if (hmac_id > ARRAY_SIZE(hash_map))
+		return 0;
+	return hash_map[hmac_id].len;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_hmac_hash_len);
+
+struct nvme_dhchap_key *nvme_auth_extract_key(unsigned char *secret,
+					      u8 key_hash)
+{
+	struct nvme_dhchap_key *key;
+	unsigned char *p;
+	u32 crc;
+	int ret, key_len;
+	size_t allocated_len = strlen(secret);
+
+	/* Secret might be affixed with a ':' */
+	p = strrchr(secret, ':');
+	if (p)
+		allocated_len = p - secret;
+	key = kzalloc(sizeof(*key), GFP_KERNEL);
+	if (!key)
+		return ERR_PTR(-ENOMEM);
+	key->key = kzalloc(allocated_len, GFP_KERNEL);
+	if (!key->key) {
+		ret = -ENOMEM;
+		goto out_free_key;
+	}
+
+	key_len = base64_decode(secret, allocated_len, key->key);
+	if (key_len < 0) {
+		pr_debug("base64 key decoding error %d\n",
+			 key_len);
+		ret = key_len;
+		goto out_free_secret;
+	}
+
+	if (key_len != 36 && key_len != 52 &&
+	    key_len != 68) {
+		pr_err("Invalid key len %d\n", key_len);
+		ret = -EINVAL;
+		goto out_free_secret;
+	}
+
+	if (key_hash > 0 &&
+	    (key_len - 4) != nvme_auth_hmac_hash_len(key_hash)) {
+		pr_err("Mismatched key len %d for %s\n", key_len,
+		       nvme_auth_hmac_name(key_hash));
+		ret = -EINVAL;
+		goto out_free_secret;
+	}
+
+	/* The last four bytes is the CRC in little-endian format */
+	key_len -= 4;
+	/*
+	 * The linux implementation doesn't do pre- and post-increments,
+	 * so we have to do it manually.
+	 */
+	crc = ~crc32(~0, key->key, key_len);
+
+	if (get_unaligned_le32(key->key + key_len) != crc) {
+		pr_err("key crc mismatch (key %08x, crc %08x)\n",
+		       get_unaligned_le32(key->key + key_len), crc);
+		ret = -EKEYREJECTED;
+		goto out_free_secret;
+	}
+	key->len = key_len;
+	key->hash = key_hash;
+	return key;
+out_free_secret:
+	kfree_sensitive(key->key);
+out_free_key:
+	kfree(key);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(nvme_auth_extract_key);
+
+void nvme_auth_free_key(struct nvme_dhchap_key *key)
+{
+	if (!key)
+		return;
+	kfree_sensitive(key->key);
+	kfree(key);
+}
+EXPORT_SYMBOL_GPL(nvme_auth_free_key);
+
+u8 *nvme_auth_transform_key(struct nvme_dhchap_key *key, char *nqn)
+{
+	const char *hmac_name;
+	struct crypto_shash *key_tfm;
+	struct shash_desc *shash;
+	u8 *transformed_key;
+	int ret;
+
+	if (!key || !key->key) {
+		pr_warn("No key specified\n");
+		return ERR_PTR(-ENOKEY);
+	}
+	if (key->hash == 0) {
+		transformed_key = kmemdup(key->key, key->len, GFP_KERNEL);
+		return transformed_key ? transformed_key : ERR_PTR(-ENOMEM);
+	}
+	hmac_name = nvme_auth_hmac_name(key->hash);
+	if (!hmac_name) {
+		pr_warn("Invalid key hash id %d\n", key->hash);
+		return ERR_PTR(-EINVAL);
+	}
+
+	key_tfm = crypto_alloc_shash(hmac_name, 0, 0);
+	if (IS_ERR(key_tfm))
+		return (u8 *)key_tfm;
+
+	shash = kmalloc(sizeof(struct shash_desc) +
+			crypto_shash_descsize(key_tfm),
+			GFP_KERNEL);
+	if (!shash) {
+		ret = -ENOMEM;
+		goto out_free_key;
+	}
+
+	transformed_key = kzalloc(crypto_shash_digestsize(key_tfm), GFP_KERNEL);
+	if (!transformed_key) {
+		ret = -ENOMEM;
+		goto out_free_shash;
+	}
+
+	shash->tfm = key_tfm;
+	ret = crypto_shash_setkey(key_tfm, key->key, key->len);
+	if (ret < 0)
+		goto out_free_shash;
+	ret = crypto_shash_init(shash);
+	if (ret < 0)
+		goto out_free_shash;
+	ret = crypto_shash_update(shash, nqn, strlen(nqn));
+	if (ret < 0)
+		goto out_free_shash;
+	ret = crypto_shash_update(shash, "NVMe-over-Fabrics", 17);
+	if (ret < 0)
+		goto out_free_shash;
+	ret = crypto_shash_final(shash, transformed_key);
+out_free_shash:
+	kfree(shash);
+out_free_key:
+	crypto_free_shash(key_tfm);
+	if (ret < 0) {
+		kfree_sensitive(transformed_key);
+		return ERR_PTR(ret);
+	}
+	return transformed_key;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_transform_key);
+
+int nvme_auth_generate_key(u8 *secret, struct nvme_dhchap_key **ret_key)
+{
+	struct nvme_dhchap_key *key;
+	u8 key_hash;
+
+	if (!secret) {
+		*ret_key = NULL;
+		return 0;
+	}
+
+	if (sscanf(secret, "DHHC-1:%hhd:%*s:", &key_hash) != 1)
+		return -EINVAL;
+
+	/* Pass in the secret without the 'DHHC-1:XX:' prefix */
+	key = nvme_auth_extract_key(secret + 10, key_hash);
+	if (IS_ERR(key)) {
+		*ret_key = NULL;
+		return PTR_ERR(key);
+	}
+
+	*ret_key = key;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_generate_key);
+
+MODULE_LICENSE("GPL v2");