KEYS: trusted: Add generic trusted keys framework

Current trusted keys framework is tightly coupled to use TPM device as
an underlying implementation which makes it difficult for implementations
like Trusted Execution Environment (TEE) etc. to provide trusted keys
support in case platform doesn't posses a TPM device.

Add a generic trusted keys framework where underlying implementations
can be easily plugged in. Create struct trusted_key_ops to achieve this,
which contains necessary functions of a backend.

Also, define a module parameter in order to select a particular trust
source in case a platform support multiple trust sources. In case its
not specified then implementation itetrates through trust sources list
starting with TPM and assign the first trust source as a backend which
has initiazed successfully during iteration.

Note that current implementation only supports a single trust source at
runtime which is either selectable at compile time or during boot via
aforementioned module parameter.
Suggested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

Documentation/admin-guide/kernel-parameters.txt

@@ -5462,6 +5462,18 @@
 			See Documentation/admin-guide/mm/transhuge.rst
 			for more details.
 
+	trusted.source=	[KEYS]
+			Format: <string>
+			This parameter identifies the trust source as a backend
+			for trusted keys implementation. Supported trust
+			sources:
+			- "tpm"
+			- "tee"
+			If not specified then it defaults to iterating through
+			the trust source list starting with TPM and assigns the
+			first trust source as a backend which is initialized
+			successfully during iteration.
+
 	tsc=		Disable clocksource stability checks for TSC.
 			Format: <string>
 			[x86] reliable: mark tsc clocksource as reliable, this

include/keys/trusted-type.h

@@ -11,6 +11,12 @@
 #include <linux/rcupdate.h>
 #include <linux/tpm.h>
 
+#ifdef pr_fmt
+#undef pr_fmt
+#endif
+
+#define pr_fmt(fmt) "trusted_key: " fmt
+
 #define MIN_KEY_SIZE			32
 #define MAX_KEY_SIZE			128
 #define MAX_BLOB_SIZE			512
@@ -42,6 +48,53 @@ struct trusted_key_options {
 	uint32_t policyhandle;
 };
 
+struct trusted_key_ops {
+	/*
+	 * flag to indicate if trusted key implementation supports migration
+	 * or not.
+	 */
+	unsigned char migratable;
+
+	/* Initialize key interface. */
+	int (*init)(void);
+
+	/* Seal a key. */
+	int (*seal)(struct trusted_key_payload *p, char *datablob);
+
+	/* Unseal a key. */
+	int (*unseal)(struct trusted_key_payload *p, char *datablob);
+
+	/* Get a randomized key. */
+	int (*get_random)(unsigned char *key, size_t key_len);
+
+	/* Exit key interface. */
+	void (*exit)(void);
+};
+
+struct trusted_key_source {
+	char *name;
+	struct trusted_key_ops *ops;
+};
+
 extern struct key_type key_type_trusted;
 
+#define TRUSTED_DEBUG 0
+
+#if TRUSTED_DEBUG
+static inline void dump_payload(struct trusted_key_payload *p)
+{
+	pr_info("key_len %d\n", p->key_len);
+	print_hex_dump(KERN_INFO, "key ", DUMP_PREFIX_NONE,
+		       16, 1, p->key, p->key_len, 0);
+	pr_info("bloblen %d\n", p->blob_len);
+	print_hex_dump(KERN_INFO, "blob ", DUMP_PREFIX_NONE,
+		       16, 1, p->blob, p->blob_len, 0);
+	pr_info("migratable %d\n", p->migratable);
+}
+#else
+static inline void dump_payload(struct trusted_key_payload *p)
+{
+}
+#endif
+
 #endif /* _KEYS_TRUSTED_TYPE_H */

include/keys/trusted_tpm.h

@@ -16,6 +16,8 @@
 #define LOAD32N(buffer, offset)	(*(uint32_t *)&buffer[offset])
 #define LOAD16(buffer, offset)	(ntohs(*(uint16_t *)&buffer[offset]))
 
+extern struct trusted_key_ops trusted_key_tpm_ops;
+
 struct osapsess {
 	uint32_t handle;
 	unsigned char secret[SHA1_DIGEST_SIZE];
@@ -52,30 +54,19 @@ int tpm2_unseal_trusted(struct tpm_chip *chip,
 #if TPM_DEBUG
 static inline void dump_options(struct trusted_key_options *o)
 {
-	pr_info("trusted_key: sealing key type %d\n", o->keytype);
-	pr_info("trusted_key: sealing key handle %0X\n", o->keyhandle);
-	pr_info("trusted_key: pcrlock %d\n", o->pcrlock);
-	pr_info("trusted_key: pcrinfo %d\n", o->pcrinfo_len);
+	pr_info("sealing key type %d\n", o->keytype);
+	pr_info("sealing key handle %0X\n", o->keyhandle);
+	pr_info("pcrlock %d\n", o->pcrlock);
+	pr_info("pcrinfo %d\n", o->pcrinfo_len);
 	print_hex_dump(KERN_INFO, "pcrinfo ", DUMP_PREFIX_NONE,
 		       16, 1, o->pcrinfo, o->pcrinfo_len, 0);
 }
 
-static inline void dump_payload(struct trusted_key_payload *p)
-{
-	pr_info("trusted_key: key_len %d\n", p->key_len);
-	print_hex_dump(KERN_INFO, "key ", DUMP_PREFIX_NONE,
-		       16, 1, p->key, p->key_len, 0);
-	pr_info("trusted_key: bloblen %d\n", p->blob_len);
-	print_hex_dump(KERN_INFO, "blob ", DUMP_PREFIX_NONE,
-		       16, 1, p->blob, p->blob_len, 0);
-	pr_info("trusted_key: migratable %d\n", p->migratable);
-}
-
 static inline void dump_sess(struct osapsess *s)
 {
 	print_hex_dump(KERN_INFO, "trusted-key: handle ", DUMP_PREFIX_NONE,
 		       16, 1, &s->handle, 4, 0);
-	pr_info("trusted-key: secret:\n");
+	pr_info("secret:\n");
 	print_hex_dump(KERN_INFO, "", DUMP_PREFIX_NONE,
 		       16, 1, &s->secret, SHA1_DIGEST_SIZE, 0);
 	pr_info("trusted-key: enonce:\n");
@@ -87,7 +78,7 @@ static inline void dump_tpm_buf(unsigned char *buf)
 {
 	int len;
 
-	pr_info("\ntrusted-key: tpm buffer\n");
+	pr_info("\ntpm buffer\n");
 	len = LOAD32(buf, TPM_SIZE_OFFSET);
 	print_hex_dump(KERN_INFO, "", DUMP_PREFIX_NONE, 16, 1, buf, len, 0);
 }
@@ -96,10 +87,6 @@ static inline void dump_options(struct trusted_key_options *o)
 {
 }
 
-static inline void dump_payload(struct trusted_key_payload *p)
-{
-}
-
 static inline void dump_sess(struct osapsess *s)
 {
 }

security/keys/trusted-keys/Makefile

@@ -4,6 +4,7 @@
 #
 
 obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
+trusted-y += trusted_core.o
 trusted-y += trusted_tpm1.o
 
 $(obj)/trusted_tpm2.o: $(obj)/tpm2key.asn1.h

security/keys/trusted-keys/trusted_core.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2010 IBM Corporation
+ * Copyright (c) 2019-2021, Linaro Limited
+ *
+ * See Documentation/security/keys/trusted-encrypted.rst
+ */
+
+#include <keys/user-type.h>
+#include <keys/trusted-type.h>
+#include <keys/trusted_tpm.h>
+#include <linux/capability.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/key-type.h>
+#include <linux/module.h>
+#include <linux/parser.h>
+#include <linux/rcupdate.h>
+#include <linux/slab.h>
+#include <linux/static_call.h>
+#include <linux/string.h>
+#include <linux/uaccess.h>
+
+static char *trusted_key_source;
+module_param_named(source, trusted_key_source, charp, 0);
+MODULE_PARM_DESC(source, "Select trusted keys source (tpm or tee)");
+
+static const struct trusted_key_source trusted_key_sources[] = {
+#if defined(CONFIG_TCG_TPM)
+	{ "tpm", &trusted_key_tpm_ops },
+#endif
+};
+
+DEFINE_STATIC_CALL_NULL(trusted_key_init, *trusted_key_sources[0].ops->init);
+DEFINE_STATIC_CALL_NULL(trusted_key_seal, *trusted_key_sources[0].ops->seal);
+DEFINE_STATIC_CALL_NULL(trusted_key_unseal,
+			*trusted_key_sources[0].ops->unseal);
+DEFINE_STATIC_CALL_NULL(trusted_key_get_random,
+			*trusted_key_sources[0].ops->get_random);
+DEFINE_STATIC_CALL_NULL(trusted_key_exit, *trusted_key_sources[0].ops->exit);
+static unsigned char migratable;
+
+enum {
+	Opt_err,
+	Opt_new, Opt_load, Opt_update,
+};
+
+static const match_table_t key_tokens = {
+	{Opt_new, "new"},
+	{Opt_load, "load"},
+	{Opt_update, "update"},
+	{Opt_err, NULL}
+};
+
+/*
+ * datablob_parse - parse the keyctl data and fill in the
+ *                  payload structure
+ *
+ * On success returns 0, otherwise -EINVAL.
+ */
+static int datablob_parse(char *datablob, struct trusted_key_payload *p)
+{
+	substring_t args[MAX_OPT_ARGS];
+	long keylen;
+	int ret = -EINVAL;
+	int key_cmd;
+	char *c;
+
+	/* main command */
+	c = strsep(&datablob, " \t");
+	if (!c)
+		return -EINVAL;
+	key_cmd = match_token(c, key_tokens, args);
+	switch (key_cmd) {
+	case Opt_new:
+		/* first argument is key size */
+		c = strsep(&datablob, " \t");
+		if (!c)
+			return -EINVAL;
+		ret = kstrtol(c, 10, &keylen);
+		if (ret < 0 || keylen < MIN_KEY_SIZE || keylen > MAX_KEY_SIZE)
+			return -EINVAL;
+		p->key_len = keylen;
+		ret = Opt_new;
+		break;
+	case Opt_load:
+		/* first argument is sealed blob */
+		c = strsep(&datablob, " \t");
+		if (!c)
+			return -EINVAL;
+		p->blob_len = strlen(c) / 2;
+		if (p->blob_len > MAX_BLOB_SIZE)
+			return -EINVAL;
+		ret = hex2bin(p->blob, c, p->blob_len);
+		if (ret < 0)
+			return -EINVAL;
+		ret = Opt_load;
+		break;
+	case Opt_update:
+		ret = Opt_update;
+		break;
+	case Opt_err:
+		return -EINVAL;
+	}
+	return ret;
+}
+
+static struct trusted_key_payload *trusted_payload_alloc(struct key *key)
+{
+	struct trusted_key_payload *p = NULL;
+	int ret;
+
+	ret = key_payload_reserve(key, sizeof(*p));
+	if (ret < 0)
+		return p;
+	p = kzalloc(sizeof(*p), GFP_KERNEL);
+
+	p->migratable = migratable;
+
+	return p;
+}
+
+/*
+ * trusted_instantiate - create a new trusted key
+ *
+ * Unseal an existing trusted blob or, for a new key, get a
+ * random key, then seal and create a trusted key-type key,
+ * adding it to the specified keyring.
+ *
+ * On success, return 0. Otherwise return errno.
+ */
+static int trusted_instantiate(struct key *key,
+			       struct key_preparsed_payload *prep)
+{
+	struct trusted_key_payload *payload = NULL;
+	size_t datalen = prep->datalen;
+	char *datablob;
+	int ret = 0;
+	int key_cmd;
+	size_t key_len;
+
+	if (datalen <= 0 || datalen > 32767 || !prep->data)
+		return -EINVAL;
+
+	datablob = kmalloc(datalen + 1, GFP_KERNEL);
+	if (!datablob)
+		return -ENOMEM;
+	memcpy(datablob, prep->data, datalen);
+	datablob[datalen] = '\0';
+
+	payload = trusted_payload_alloc(key);
+	if (!payload) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	key_cmd = datablob_parse(datablob, payload);
+	if (key_cmd < 0) {
+		ret = key_cmd;
+		goto out;
+	}
+
+	dump_payload(payload);
+
+	switch (key_cmd) {
+	case Opt_load:
+		ret = static_call(trusted_key_unseal)(payload, datablob);
+		dump_payload(payload);
+		if (ret < 0)
+			pr_info("key_unseal failed (%d)\n", ret);
+		break;
+	case Opt_new:
+		key_len = payload->key_len;
+		ret = static_call(trusted_key_get_random)(payload->key,
+							  key_len);
+		if (ret < 0)
+			goto out;
+
+		if (ret != key_len) {
+			pr_info("key_create failed (%d)\n", ret);
+			ret = -EIO;
+			goto out;
+		}
+
+		ret = static_call(trusted_key_seal)(payload, datablob);
+		if (ret < 0)
+			pr_info("key_seal failed (%d)\n", ret);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+out:
+	kfree_sensitive(datablob);
+	if (!ret)
+		rcu_assign_keypointer(key, payload);
+	else
+		kfree_sensitive(payload);
+	return ret;
+}
+
+static void trusted_rcu_free(struct rcu_head *rcu)
+{
+	struct trusted_key_payload *p;
+
+	p = container_of(rcu, struct trusted_key_payload, rcu);
+	kfree_sensitive(p);
+}
+
+/*
+ * trusted_update - reseal an existing key with new PCR values
+ */
+static int trusted_update(struct key *key, struct key_preparsed_payload *prep)
+{
+	struct trusted_key_payload *p;
+	struct trusted_key_payload *new_p;
+	size_t datalen = prep->datalen;
+	char *datablob;
+	int ret = 0;
+
+	if (key_is_negative(key))
+		return -ENOKEY;
+	p = key->payload.data[0];
+	if (!p->migratable)
+		return -EPERM;
+	if (datalen <= 0 || datalen > 32767 || !prep->data)
+		return -EINVAL;
+
+	datablob = kmalloc(datalen + 1, GFP_KERNEL);
+	if (!datablob)
+		return -ENOMEM;
+
+	new_p = trusted_payload_alloc(key);
+	if (!new_p) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	memcpy(datablob, prep->data, datalen);
+	datablob[datalen] = '\0';
+	ret = datablob_parse(datablob, new_p);
+	if (ret != Opt_update) {
+		ret = -EINVAL;
+		kfree_sensitive(new_p);
+		goto out;
+	}
+
+	/* copy old key values, and reseal with new pcrs */
+	new_p->migratable = p->migratable;
+	new_p->key_len = p->key_len;
+	memcpy(new_p->key, p->key, p->key_len);
+	dump_payload(p);
+	dump_payload(new_p);
+
+	ret = static_call(trusted_key_seal)(new_p, datablob);
+	if (ret < 0) {
+		pr_info("key_seal failed (%d)\n", ret);
+		kfree_sensitive(new_p);
+		goto out;
+	}
+
+	rcu_assign_keypointer(key, new_p);
+	call_rcu(&p->rcu, trusted_rcu_free);
+out:
+	kfree_sensitive(datablob);
+	return ret;
+}
+
+/*
+ * trusted_read - copy the sealed blob data to userspace in hex.
+ * On success, return to userspace the trusted key datablob size.
+ */
+static long trusted_read(const struct key *key, char *buffer,
+			 size_t buflen)
+{
+	const struct trusted_key_payload *p;
+	char *bufp;
+	int i;
+
+	p = dereference_key_locked(key);
+	if (!p)
+		return -EINVAL;
+
+	if (buffer && buflen >= 2 * p->blob_len) {
+		bufp = buffer;
+		for (i = 0; i < p->blob_len; i++)
+			bufp = hex_byte_pack(bufp, p->blob[i]);
+	}
+	return 2 * p->blob_len;
+}
+
+/*
+ * trusted_destroy - clear and free the key's payload
+ */
+static void trusted_destroy(struct key *key)
+{
+	kfree_sensitive(key->payload.data[0]);
+}
+
+struct key_type key_type_trusted = {
+	.name = "trusted",
+	.instantiate = trusted_instantiate,
+	.update = trusted_update,
+	.destroy = trusted_destroy,
+	.describe = user_describe,
+	.read = trusted_read,
+};
+EXPORT_SYMBOL_GPL(key_type_trusted);
+
+static int __init init_trusted(void)
+{
+	int i, ret = 0;
+
+	for (i = 0; i < ARRAY_SIZE(trusted_key_sources); i++) {
+		if (trusted_key_source &&
+		    strncmp(trusted_key_source, trusted_key_sources[i].name,
+			    strlen(trusted_key_sources[i].name)))
+			continue;
+
+		static_call_update(trusted_key_init,
+				   trusted_key_sources[i].ops->init);
+		static_call_update(trusted_key_seal,
+				   trusted_key_sources[i].ops->seal);
+		static_call_update(trusted_key_unseal,
+				   trusted_key_sources[i].ops->unseal);
+		static_call_update(trusted_key_get_random,
+				   trusted_key_sources[i].ops->get_random);
+		static_call_update(trusted_key_exit,
+				   trusted_key_sources[i].ops->exit);
+		migratable = trusted_key_sources[i].ops->migratable;
+
+		ret = static_call(trusted_key_init)();
+		if (!ret)
+			break;
+	}
+
+	/*
+	 * encrypted_keys.ko depends on successful load of this module even if
+	 * trusted key implementation is not found.
+	 */
+	if (ret == -ENODEV)
+		return 0;
+
+	return ret;
+}
+
+static void __exit cleanup_trusted(void)
+{
+	static_call(trusted_key_exit)();
+}
+
+late_initcall(init_trusted);
+module_exit(cleanup_trusted);
+
+MODULE_LICENSE("GPL");