[RFC v2 10/13] keys/mktme: Add the MKTME Key Service type for memory encryption
Sakkinen, Jarkko
jarkko.sakkinen at intel.com
Thu Dec 6 08:51:36 UTC 2018
On Mon, 2018-12-03 at 23:39 -0800, Alison Schofield wrote:
> MKTME (Multi-Key Total Memory Encryption) is a technology that allows
> transparent memory encryption in upcoming Intel platforms. MKTME will
> support mulitple encryption domains, each having their own key. The main
> use case for the feature is virtual machine isolation. The API needs the
> flexibility to work for a wide range of uses.
Some, maybe brutal, honesty (apologies)...
Have never really got the grip why either SME or TME would make
isolation any better. If you can break into hypervisor, you'll
have these tools availabe:
1. Read page (in encrypted form).
2. Write page (for example replay as pages are not versioned).
with all the side-channel possibilities of course since you can
control the VMs (in which core they execute etc.).
I've seen now SME presentation three times and it always leaves
me an empty feeling. This feels the same same.
> The MKTME key service type manages the addition and removal of the memory
> encryption keys. It maps Userspace Keys to hardware KeyIDs. It programs
> the hardware with the user requested encryption options.
>
> The only supported encryption algorithm is AES-XTS 128.
>
> The MKTME key service is half of the MKTME API level solution. It pairs
> with a new memory encryption system call: encrypt_mprotect() that uses
> the keys to encrypt memory.
>
> See Documentation/x86/mktme/mktme.rst
>
> Change-Id: Idda4af2beabb739c77719897affff183ee9fa716
> Signed-off-by: Alison Schofield <alison.schofield at intel.com>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov at linux.intel.com>
> ---
> arch/x86/Kconfig | 1 +
> include/keys/mktme-type.h | 41 ++++++
> security/keys/Kconfig | 11 ++
> security/keys/Makefile | 1 +
> security/keys/mktme_keys.c | 339
> +++++++++++++++++++++++++++++++++++++++++++++
> 5 files changed, 393 insertions(+)
> create mode 100644 include/keys/mktme-type.h
> create mode 100644 security/keys/mktme_keys.c
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 7ac78e2856c7..c2e3bb5af077 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1531,6 +1531,7 @@ config X86_INTEL_MKTME
> bool "Intel Multi-Key Total Memory Encryption"
> select DYNAMIC_PHYSICAL_MASK
> select PAGE_EXTENSION
> + select MKTME_KEYS
> depends on X86_64 && CPU_SUP_INTEL
> ---help---
> Say yes to enable support for Multi-Key Total Memory Encryption.
> diff --git a/include/keys/mktme-type.h b/include/keys/mktme-type.h
> new file mode 100644
> index 000000000000..c63c6568087f
> --- /dev/null
> +++ b/include/keys/mktme-type.h
> @@ -0,0 +1,41 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +/* Key service for Multi-KEY Total Memory Encryption */
> +
> +#ifndef _KEYS_MKTME_TYPE_H
> +#define _KEYS_MKTME_TYPE_H
> +
> +#include <linux/key.h>
> +
> +/*
> + * The AES-XTS 128 encryption algorithm requires 128 bits for each
> + * user supplied data key and tweak key.
> + */
> +#define MKTME_AES_XTS_SIZE 16 /* 16 bytes, 128 bits */
> +
> +enum mktme_alg {
> + MKTME_ALG_AES_XTS_128,
> +};
> +
> +const char *const mktme_alg_names[] = {
> + [MKTME_ALG_AES_XTS_128] = "aes-xts-128",
> +};
> +
> +enum mktme_type {
> + MKTME_TYPE_ERROR = -1,
> + MKTME_TYPE_USER,
> + MKTME_TYPE_CPU,
> + MKTME_TYPE_CLEAR,
> + MKTME_TYPE_NO_ENCRYPT,
> +};
> +
> +const char *const mktme_type_names[] = {
> + [MKTME_TYPE_USER] = "user",
> + [MKTME_TYPE_CPU] = "cpu",
> + [MKTME_TYPE_CLEAR] = "clear",
> + [MKTME_TYPE_NO_ENCRYPT] = "no-encrypt",
> +};
> +
> +extern struct key_type key_type_mktme;
> +
> +#endif /* _KEYS_MKTME_TYPE_H */
> diff --git a/security/keys/Kconfig b/security/keys/Kconfig
> index 6462e6654ccf..c36972113e67 100644
> --- a/security/keys/Kconfig
> +++ b/security/keys/Kconfig
> @@ -101,3 +101,14 @@ config KEY_DH_OPERATIONS
> in the kernel.
>
> If you are unsure as to whether this is required, answer N.
> +
> +config MKTME_KEYS
> + bool "Multi-Key Total Memory Encryption Keys"
> + depends on KEYS && X86_INTEL_MKTME
> + help
> + This option provides support for Multi-Key Total Memory
> + Encryption (MKTME) on Intel platforms offering the feature.
> + MKTME allows userspace to manage the hardware encryption
> + keys through the kernel key services.
> +
> + If you are unsure as to whether this is required, answer N.
> diff --git a/security/keys/Makefile b/security/keys/Makefile
> index 9cef54064f60..94c84f10a857 100644
> --- a/security/keys/Makefile
> +++ b/security/keys/Makefile
> @@ -30,3 +30,4 @@ obj-$(CONFIG_ASYMMETRIC_KEY_TYPE) += keyctl_pkey.o
> obj-$(CONFIG_BIG_KEYS) += big_key.o
> obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
> obj-$(CONFIG_ENCRYPTED_KEYS) += encrypted-keys/
> +obj-$(CONFIG_MKTME_KEYS) += mktme_keys.o
> diff --git a/security/keys/mktme_keys.c b/security/keys/mktme_keys.c
> new file mode 100644
> index 000000000000..e615eb58e600
> --- /dev/null
> +++ b/security/keys/mktme_keys.c
> @@ -0,0 +1,339 @@
> +// SPDX-License-Identifier: GPL-3.0
> +
> +/* Documentation/x86/mktme/mktme_keys.rst */
> +
> +#include <linux/cred.h>
> +#include <linux/cpu.h>
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/key.h>
> +#include <linux/key-type.h>
> +#include <linux/init.h>
> +#include <linux/parser.h>
> +#include <linux/random.h>
> +#include <linux/slab.h>
> +#include <linux/string.h>
> +#include <asm/intel_pconfig.h>
> +#include <asm/mktme.h>
> +#include <keys/mktme-type.h>
> +#include <keys/user-type.h>
> +
> +#include "internal.h"
> +
> +struct kmem_cache *mktme_prog_cache; /* Hardware programming cache */
> +
> +static const char * const mktme_program_err[] = {
> + "KeyID was successfully programmed", /* 0 */
> + "Invalid KeyID programming command", /* 1 */
> + "Insufficient entropy", /* 2 */
> + "KeyID not valid", /* 3 */
> + "Invalid encryption algorithm chosen", /* 4 */
> + "Failure to access key table", /* 5 */
> +};
> +
> +enum mktme_opt_id {
> + OPT_ERROR = -1,
> + OPT_TYPE,
> + OPT_KEY,
> + OPT_TWEAK,
> + OPT_ALGORITHM,
> +};
> +
> +static const match_table_t mktme_token = {
> + {OPT_TYPE, "type=%s"},
> + {OPT_KEY, "key=%s"},
> + {OPT_TWEAK, "tweak=%s"},
> + {OPT_ALGORITHM, "algorithm=%s"},
> + {OPT_ERROR, NULL}
> +};
> +
> +struct mktme_payload {
> + u32 keyid_ctrl; /* Command & Encryption Algorithm */
> + u8 data_key[MKTME_AES_XTS_SIZE];
> + u8 tweak_key[MKTME_AES_XTS_SIZE];
> +};
> +
> +/* Key Service Method called when Key is garbage collected. */
> +static void mktme_destroy_key(struct key *key)
> +{
> + key_put_encrypt_ref(mktme_map_keyid_from_key(key));
> +}
> +
> +/* Copy the payload to the HW programming structure and program this KeyID */
> +static int mktme_program_keyid(int keyid, struct mktme_payload *payload)
> +{
> + struct mktme_key_program *kprog = NULL;
> + u8 kern_entropy[MKTME_AES_XTS_SIZE];
> + int i, ret;
> +
> + kprog = kmem_cache_zalloc(mktme_prog_cache, GFP_KERNEL);
> + if (!kprog)
> + return -ENOMEM;
> +
> + /* Hardware programming requires cached aligned struct */
> + kprog->keyid = keyid;
> + kprog->keyid_ctrl = payload->keyid_ctrl;
> + memcpy(kprog->key_field_1, payload->data_key, MKTME_AES_XTS_SIZE);
> + memcpy(kprog->key_field_2, payload->tweak_key, MKTME_AES_XTS_SIZE);
> +
> + /* Strengthen the entropy fields for CPU generated keys */
> + if ((payload->keyid_ctrl & 0xff) == MKTME_KEYID_SET_KEY_RANDOM) {
> + get_random_bytes(&kern_entropy, sizeof(kern_entropy));
> + for (i = 0; i < (MKTME_AES_XTS_SIZE); i++) {
> + kprog->key_field_1[i] ^= kern_entropy[i];
> + kprog->key_field_2[i] ^= kern_entropy[i];
> + }
> + }
> + ret = mktme_key_program(kprog);
> + kmem_cache_free(mktme_prog_cache, kprog);
> + return ret;
> +}
> +
> +/* Key Service Method to update an existing key. */
> +static int mktme_update_key(struct key *key,
> + struct key_preparsed_payload *prep)
> +{
> + struct mktme_payload *payload = prep->payload.data[0];
> + int keyid, ref_count;
> + int ret;
> +
> + mktme_map_lock();
> + keyid = mktme_map_keyid_from_key(key);
> + if (keyid <= 0)
> + return -EINVAL;
> + /*
> + * ref_count will be at least one when we get here because the
> + * key already exists. If ref_count is not > 1, it is safe to
> + * update the key while holding the mktme_map_lock.
> + */
> + ref_count = mktme_read_encrypt_ref(keyid);
> + if (ref_count > 1) {
> + pr_debug("mktme not updating keyid[%d] encrypt_count[%d]\n",
> + keyid, ref_count);
> + return -EBUSY;
> + }
> + ret = mktme_program_keyid(keyid, payload);
> + if (ret != MKTME_PROG_SUCCESS) {
> + pr_debug("%s: %s\n", __func__, mktme_program_err[ret]);
> + ret = -ENOKEY;
> + }
> + mktme_map_unlock();
> + return ret;
> +}
> +
> +/* Key Service Method to create a new key. Payload is preparsed. */
> +int mktme_instantiate_key(struct key *key, struct key_preparsed_payload
> *prep)
> +{
> + struct mktme_payload *payload = prep->payload.data[0];
> + int keyid, ret;
> +
> + mktme_map_lock();
> + keyid = mktme_map_get_free_keyid();
> + if (keyid == 0) {
> + ret = -ENOKEY;
> + goto out;
> + }
> + ret = mktme_program_keyid(keyid, payload);
> + if (ret != MKTME_PROG_SUCCESS) {
> + pr_debug("%s: %s\n", __func__, mktme_program_err[ret]);
> + ret = -ENOKEY;
> + goto out;
> + }
> + mktme_map_set_keyid(keyid, key);
> + key_get_encrypt_ref(keyid);
> +out:
> + mktme_map_unlock();
> + return ret;
> +}
> +
> +/* Verify the user provided the needed arguments for the TYPE of Key */
> +static int mktme_check_options(struct mktme_payload *payload,
> + unsigned long token_mask, enum mktme_type type)
> +{
> + if (!token_mask)
> + return -EINVAL;
> +
> + switch (type) {
> + case MKTME_TYPE_USER:
> + if (test_bit(OPT_ALGORITHM, &token_mask))
> + payload->keyid_ctrl |= MKTME_AES_XTS_128;
> + else
> + return -EINVAL;
> +
> + if ((test_bit(OPT_KEY, &token_mask)) &&
> + (test_bit(OPT_TWEAK, &token_mask)))
> + payload->keyid_ctrl |= MKTME_KEYID_SET_KEY_DIRECT;
> + else
> + return -EINVAL;
> + break;
> +
> + case MKTME_TYPE_CPU:
> + if (test_bit(OPT_ALGORITHM, &token_mask))
> + payload->keyid_ctrl |= MKTME_AES_XTS_128;
> + else
> + return -EINVAL;
> +
> + payload->keyid_ctrl |= MKTME_KEYID_SET_KEY_RANDOM;
> + break;
> +
> + case MKTME_TYPE_CLEAR:
> + payload->keyid_ctrl |= MKTME_KEYID_CLEAR_KEY;
> + break;
> +
> + case MKTME_TYPE_NO_ENCRYPT:
> + payload->keyid_ctrl |= MKTME_KEYID_NO_ENCRYPT;
> + break;
> +
> + default:
> + return -EINVAL;
> + }
> + return 0;
> +}
> +
> +/* Parse the options and store the key programming data in the payload. */
> +static int mktme_get_options(char *options, struct mktme_payload *payload)
> +{
> + enum mktme_type type = MKTME_TYPE_ERROR;
> + substring_t args[MAX_OPT_ARGS];
> + unsigned long token_mask = 0;
> + char *p = options;
> + int ret, token;
> +
> + while ((p = strsep(&options, " \t"))) {
> + if (*p == '\0' || *p == ' ' || *p == '\t')
> + continue;
> + token = match_token(p, mktme_token, args);
> + if (test_and_set_bit(token, &token_mask))
> + return -EINVAL;
> +
> + switch (token) {
> + case OPT_KEY:
> + ret = hex2bin(payload->data_key, args[0].from,
> + MKTME_AES_XTS_SIZE);
> + if (ret < 0)
> + return -EINVAL;
> + break;
> +
> + case OPT_TWEAK:
> + ret = hex2bin(payload->tweak_key, args[0].from,
> + MKTME_AES_XTS_SIZE);
> + if (ret < 0)
> + return -EINVAL;
> + break;
> +
> + case OPT_TYPE:
> + type = match_string(mktme_type_names,
> + ARRAY_SIZE(mktme_type_names),
> + args[0].from);
> + if (type < 0)
> + return -EINVAL;
> + break;
> +
> + case OPT_ALGORITHM:
> + ret = match_string(mktme_alg_names,
> + ARRAY_SIZE(mktme_alg_names),
> + args[0].from);
> + if (ret < 0)
> + return -EINVAL;
> + break;
> +
> + default:
> + return -EINVAL;
> + }
> + }
> + return mktme_check_options(payload, token_mask, type);
> +}
> +
> +void mktme_free_preparsed_key(struct key_preparsed_payload *prep)
> +{
> + kzfree(prep->payload.data[0]);
> +}
> +
> +/*
> + * Key Service Method to preparse a payload before a key is created.
> + * Check permissions and the options. Load the proposed key field
> + * data into the payload for use by instantiate and update methods.
> + */
> +int mktme_preparse_key(struct key_preparsed_payload *prep)
> +{
> + struct mktme_payload *mktme_payload;
> + size_t datalen = prep->datalen;
> + char *options;
> + int ret;
> +
> + if (!capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
> + return -EACCES;
> +
> + if (datalen <= 0 || datalen > 1024 || !prep->data)
> + return -EINVAL;
> +
> + options = kmemdup(prep->data, datalen + 1, GFP_KERNEL);
> + if (!options)
> + return -ENOMEM;
> +
> + options[datalen] = '\0';
> +
> + mktme_payload = kzalloc(sizeof(*mktme_payload), GFP_KERNEL);
> + if (!mktme_payload) {
> + ret = -ENOMEM;
> + goto out;
> + }
> + ret = mktme_get_options(options, mktme_payload);
> + if (ret < 0)
> + goto out;
> +
> + prep->quotalen = sizeof(mktme_payload);
> + prep->payload.data[0] = mktme_payload;
> +out:
> + kzfree(options);
> + return ret;
> +}
> +
> +struct key_type key_type_mktme = {
> + .name = "mktme",
> + .preparse = mktme_preparse_key,
> + .free_preparse = mktme_free_preparsed_key,
> + .instantiate = mktme_instantiate_key,
> + .update = mktme_update_key,
> + .describe = user_describe,
> + .destroy = mktme_destroy_key,
> +};
> +
> +/*
> + * Allocate the global mktme_map structure based on the available keyids.
> + * Create a cache for the hardware structure. Initialize the encrypt_count
> + * array to track * VMA's per keyid. Once all that succeeds, register the
> + * 'mktme' key type.
> + */
> +static int __init init_mktme(void)
> +{
> + int ret;
> +
> + /* Verify keys are present */
> + if (!(mktme_nr_keyids > 0))
> + return -EINVAL;
> +
> + if (!mktme_map_alloc())
> + return -ENOMEM;
> +
> + mktme_prog_cache = KMEM_CACHE(mktme_key_program, SLAB_PANIC);
> + if (!mktme_prog_cache)
> + goto free_map;
> +
> + if (mktme_alloc_encrypt_array() < 0)
> + goto free_cache;
> +
> + ret = register_key_type(&key_type_mktme);
> + if (!ret)
> + return ret; /* SUCCESS */
> +
> + mktme_free_encrypt_array();
> +free_cache:
> + kmem_cache_destroy(mktme_prog_cache);
> +free_map:
Maybe err_free_cache and err_map (more than cosmetic)?
> + mktme_map_free();
> +
> + return -ENOMEM;
> +}
> +
> +late_initcall(init_mktme);
As for code change. Overally, it looks good! But before using time
for detailed review or testing (once I get a chance to acquire
something to test it) lets go through the documentation discussion.
Clearly there is bunch of stuff that can be cut...
/Jarkko
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