[PATCHv2 25/59] keys/mktme: Preparse the MKTME key payload

Kirill A. Shutemov
2019-07-31T15:09:17Z

From: Alison Schofield <alison.schofield@intel.com>

It is a requirement of the Kernel Keys subsystem to provide a
preparse method that validates payloads before key instantiate
methods are called.

Verify that userspace provides valid MKTME options and prepare
the payload for use at key instantiate time.

Create a method to free the preparsed payload. The Kernel Key
subsystem will that to clean up after the key is instantiated.

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
include/keys/mktme-type.h | 31 +++++++++
security/keys/mktme_keys.c | 134 +++++++++++++++++++++++++++++++++++++
2 files changed, 165 insertions(+)
create mode 100644 include/keys/mktme-type.h

diff --git a/include/keys/mktme-type.h b/include/keys/mktme-type.h
new file mode 100644
index 000000000000..9dad92f17179
--- /dev/null
+++ b/include/keys/mktme-type.h
@@ -0,0 +1,31 @@
+/* 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>
+
+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_CPU,
+ MKTME_TYPE_NO_ENCRYPT,
+};
+
+const char *const mktme_type_names[] = {
+ [MKTME_TYPE_CPU] = "cpu",
+ [MKTME_TYPE_NO_ENCRYPT] = "no-encrypt",
+};
+
+extern struct key_type key_type_mktme;
+
+#endif /* _KEYS_MKTME_TYPE_H */
diff --git a/security/keys/mktme_keys.c b/security/keys/mktme_keys.c
index d262e0f348e4..fe119a155235 100644
--- a/security/keys/mktme_keys.c
+++ b/security/keys/mktme_keys.c
@@ -6,6 +6,10 @@
#include <linux/key.h>
#include <linux/key-type.h>
#include <linux/mm.h>
+#include <linux/parser.h>
+#include <linux/string.h>
+#include <asm/intel_pconfig.h>
+#include <keys/mktme-type.h>
#include <keys/user-type.h>

#include "internal.h"
@@ -27,8 +31,138 @@ struct mktme_mapping {

static struct mktme_mapping *mktme_map;

+enum mktme_opt_id {
+ OPT_ERROR,
+ OPT_TYPE,
+ OPT_ALGORITHM,
+};
+
+static const match_table_t mktme_token = {
+ {OPT_TYPE, "type=%s"},
+ {OPT_ALGORITHM, "algorithm=%s"},
+ {OPT_ERROR, NULL}
+};
+
+/* Make sure arguments are correct for the TYPE of key requested */
+static int mktme_check_options(u32 *payload, unsigned long token_mask,
+ enum mktme_type type, enum mktme_alg alg)
+{
+ if (!token_mask)
+ return -EINVAL;
+
+ switch (type) {
+ case MKTME_TYPE_CPU:
+ if (test_bit(OPT_ALGORITHM, &token_mask))
+ *payload |= (1 << alg) << 8;
+ else
+ return -EINVAL;
+
+ *payload |= MKTME_KEYID_SET_KEY_RANDOM;
+ break;
+
+ case MKTME_TYPE_NO_ENCRYPT:
+ *payload |= 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, u32 *payload)
+{
+ enum mktme_alg alg = MKTME_ALG_AES_XTS_128;
+ enum mktme_type type = MKTME_TYPE_ERROR;
+ substring_t args[MAX_OPT_ARGS];
+ unsigned long token_mask = 0;
+ char *p = options;
+ int token;
+
+ while ((p = strsep(&options, " \t"))) {
+ if (*p == '\0' || *p == ' ' || *p == '\t')
+ continue;
+ token = match_token(p, mktme_token, args);
+ if (token == OPT_ERROR)
+ return -EINVAL;
+ if (test_and_set_bit(token, &token_mask))
+ return -EINVAL;
+
+ switch (token) {
+ 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:
+ /* Algorithm must be generally supported */
+ alg = match_string(mktme_alg_names,
+ ARRAY_SIZE(mktme_alg_names),
+ args[0].from);
+ if (alg < 0)
+ return -EINVAL;
+
+ /* Algorithm must be activated on this platform */
+ if (!(mktme_algs & (1 << alg)))
+ return -EINVAL;
+ break;
+
+ default:
+ return -EINVAL;
+ }
+ }
+ return mktme_check_options(payload, token_mask, type, alg);
+}
+
+void mktme_free_preparsed_payload(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 the instantiate method.
+ */
+int mktme_preparse_payload(struct key_preparsed_payload *prep)
+{
+ size_t datalen = prep->datalen;
+ u32 *mktme_payload;
+ char *options;
+ int ret;
+
+ if (datalen <= 0 || datalen > 1024 || !prep->data)
+ return -EINVAL;
+
+ options = kmemdup_nul(prep->data, datalen, GFP_KERNEL);
+ if (!options)
+ return -ENOMEM;
+
+ 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) {
+ kzfree(mktme_payload);
+ 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_payload,
+ .free_preparse = mktme_free_preparsed_payload,
.describe = user_describe,
};

--
2.21.0