[v6,4/6] crypto: tpm2_key: Introduce a TPM2 key type

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 5688d42a59c2..c8989bc71f57 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -5,6 +5,13 @@ 
 config XOR_BLOCKS
 	tristate
 
+config CRYPTO_TPM2_KEY
+	bool
+	depends on CRYPTO
+	select ASN1
+	select OID_REGISTRY
+	default n
+
 #
 # async_tx api: hardware offloaded memory transfer/transform support
 #
diff --git a/crypto/Makefile b/crypto/Makefile
index edbbaa3ffef5..d932fdb72319 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -216,3 +216,9 @@  obj-$(CONFIG_CRYPTO_SIMD) += crypto_simd.o
 # Key derivation function
 #
 obj-$(CONFIG_CRYPTO_KDF800108_CTR) += kdf_sp800108.o
+
+ifdef CONFIG_CRYPTO_TPM2_KEY
+$(obj)/tpm2_key.asn1.o: $(obj)/tpm2_key.asn1.h $(obj)/tpm2_key.asn1.c
+$(obj)/tpm2_key.o: $(obj)/tpm2_key.asn1.h
+obj-y += tpm2_key.o tpm2_key.asn1.o
+endif
diff --git a/crypto/tpm2_key.asn1 b/crypto/tpm2_key.asn1
new file mode 100644
index 000000000000..b235d02ab78e
--- /dev/null
+++ b/crypto/tpm2_key.asn1
@@ -0,0 +1,11 @@ 
+---
+--- ASN.1 for TPM 2.0 keys
+---
+
+TPMKey ::= SEQUENCE {
+	type		OBJECT IDENTIFIER ({tpm2_key_get_type}),
+	emptyAuth	[0] EXPLICIT BOOLEAN OPTIONAL,
+	parent		INTEGER ({tpm2_key_get_parent}),
+	pubkey		OCTET STRING ({tpm2_get_public}),
+	privkey		OCTET STRING ({tpm2_get_private})
+	}
diff --git a/crypto/tpm2_key.c b/crypto/tpm2_key.c
new file mode 100644
index 000000000000..78f55478d046
--- /dev/null
+++ b/crypto/tpm2_key.c
@@ -0,0 +1,134 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <crypto/tpm2_key.h>
+#include <linux/oid_registry.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <asm/unaligned.h>
+#include "tpm2_key.asn1.h"
+
+#undef pr_fmt
+#define pr_fmt(fmt) "tpm2_key: "fmt
+
+struct tpm2_key_decoder_context {
+	u32 parent;
+	const u8 *pub;
+	u32 pub_len;
+	const u8 *priv;
+	u32 priv_len;
+	enum OID oid;
+};
+
+int tpm2_key_get_parent(void *context, size_t hdrlen,
+			unsigned char tag,
+			const void *value, size_t vlen)
+{
+	struct tpm2_key_decoder_context *decoder = context;
+	const u8 *v = value;
+	int i;
+
+	decoder->parent = 0;
+	for (i = 0; i < vlen; i++) {
+		decoder->parent <<= 8;
+		decoder->parent |= v[i];
+	}
+
+	return 0;
+}
+
+int tpm2_key_get_type(void *context, size_t hdrlen,
+		      unsigned char tag,
+		      const void *value, size_t vlen)
+{
+	struct tpm2_key_decoder_context *decoder = context;
+
+	decoder->oid = look_up_OID(value, vlen);
+	return 0;
+}
+
+static inline bool tpm2_key_is_valid(const void *value, size_t vlen)
+{
+	if (vlen < 2 || vlen > TPM2_KEY_BYTES_MAX)
+		return false;
+
+	if (get_unaligned_be16(value) != vlen - 2)
+		return false;
+
+	return true;
+}
+
+int tpm2_get_public(void *context, size_t hdrlen, unsigned char tag,
+		    const void *value, size_t vlen)
+{
+	struct tpm2_key_decoder_context *decoder = context;
+
+	if (!tpm2_key_is_valid(value, vlen))
+		return -EBADMSG;
+
+	if (sizeof(struct tpm2_key_desc) > vlen - 2)
+		return -EBADMSG;
+
+	decoder->pub = value;
+	decoder->pub_len = vlen;
+	return 0;
+}
+
+int tpm2_get_private(void *context, size_t hdrlen, unsigned char tag,
+		     const void *value, size_t vlen)
+{
+	struct tpm2_key_decoder_context *decoder = context;
+
+	if (!tpm2_key_is_valid(value, vlen))
+		return -EBADMSG;
+
+	decoder->priv = value;
+	decoder->priv_len = vlen;
+	return 0;
+}
+
+/**
+ * tpm_key_decode() - Decode TPM2 ASN.1 key
+ * @src:	ASN.1 source.
+ * @src_len:	ASN.1 source length.
+ *
+ * Decodes the TPM2 ASN.1 key and validates that the public key data has all
+ * the shared fields of TPMT_PUBLIC. This is full coverage of the memory that
+ * can be validated before doing any key type specific validation.
+ *
+ * Return:
+ * - TPM2 ASN.1 key on success.
+ * - -EBADMSG when decoding fails.
+ * - -ENOMEM when OOM while allocating struct tpm2_key.
+ */
+struct tpm2_key *tpm2_key_decode(const u8 *src, u32 src_len)
+{
+	struct tpm2_key_decoder_context decoder;
+	struct tpm2_key *key;
+	u8 *data;
+	int ret;
+
+	memset(&decoder, 0, sizeof(decoder));
+	ret = asn1_ber_decoder(&tpm2_key_decoder, &decoder, src, src_len);
+	if (ret < 0) {
+		if (ret != -EBADMSG)
+			pr_info("Decoder error %d\n", ret);
+
+		return ERR_PTR(-EBADMSG);
+	}
+
+	key = kzalloc(sizeof(*key), GFP_KERNEL);
+	if (!key)
+		return ERR_PTR(-ENOMEM);
+
+	data = &key->data[0];
+	memcpy(&data[0], decoder.priv, decoder.priv_len);
+	memcpy(&data[decoder.priv_len], decoder.pub, decoder.pub_len);
+
+	key->oid = decoder.oid;
+	key->priv_len = decoder.priv_len;
+	key->pub_len = decoder.pub_len;
+	key->parent = decoder.parent;
+	key->desc = (struct tpm2_key_desc *)&data[decoder.priv_len + 2];
+	return key;
+}
+EXPORT_SYMBOL_GPL(tpm2_key_decode);
diff --git a/include/crypto/tpm2_key.h b/include/crypto/tpm2_key.h
new file mode 100644
index 000000000000..74debaf707bf
--- /dev/null
+++ b/include/crypto/tpm2_key.h
@@ -0,0 +1,46 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __LINUX_TPM2_KEY_H__
+#define __LINUX_TPM2_KEY_H__
+
+#include <linux/oid_registry.h>
+#include <linux/slab.h>
+
+#define TPM2_KEY_BYTES_MAX 1024
+
+/*  TPM2 Structures 12.2.4: TPMT_PUBLIC */
+struct tpm2_key_desc {
+	__be16 type;
+	__be16 name_alg;
+	__be32 object_attributes;
+	__be16 policy_size;
+} __packed;
+
+/* Decoded TPM2 ASN.1 key. */
+struct tpm2_key {
+	u8 data[2 * TPM2_KEY_BYTES_MAX];
+	struct tpm2_key_desc *desc;
+	u16 priv_len;
+	u16 pub_len;
+	u32 parent;
+	enum OID oid;
+	char oid_str[64];
+};
+
+struct tpm2_key *tpm2_key_decode(const u8 *src, u32 src_len);
+
+static inline const void *tpm2_key_data(const struct tpm2_key *key)
+{
+	return &key->data[0];
+}
+
+static inline u16 tpm2_key_type(const struct tpm2_key *key)
+{
+	return be16_to_cpu(key->desc->type);
+}
+
+static inline int tpm2_key_policy_size(const struct tpm2_key *key)
+{
+	return be16_to_cpu(key->desc->policy_size);
+}
+
+#endif /* __LINUX_TPM2_KEY_H__ */
diff --git a/security/keys/trusted-keys/Kconfig b/security/keys/trusted-keys/Kconfig
index 1fb8aa001995..00d9489384ac 100644
--- a/security/keys/trusted-keys/Kconfig
+++ b/security/keys/trusted-keys/Kconfig
@@ -9,9 +9,9 @@  config TRUSTED_KEYS_TPM
 	select CRYPTO_HMAC
 	select CRYPTO_SHA1
 	select CRYPTO_HASH_INFO
+	select CRYPTO_TPM2_KEY
 	select ASN1_ENCODER
 	select OID_REGISTRY
-	select ASN1
 	select HAVE_TRUSTED_KEYS
 	help
 	  Enable use of the Trusted Platform Module (TPM) as trusted key
diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
index f0f3b27f688b..2674d5c10fc9 100644
--- a/security/keys/trusted-keys/Makefile
+++ b/security/keys/trusted-keys/Makefile
@@ -7,9 +7,7 @@  obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
 trusted-y += trusted_core.o
 trusted-$(CONFIG_TRUSTED_KEYS_TPM) += trusted_tpm1.o
 
-$(obj)/trusted_tpm2.o: $(obj)/tpm2key.asn1.h
 trusted-$(CONFIG_TRUSTED_KEYS_TPM) += trusted_tpm2.o
-trusted-$(CONFIG_TRUSTED_KEYS_TPM) += tpm2key.asn1.o
 
 trusted-$(CONFIG_TRUSTED_KEYS_TEE) += trusted_tee.o
 
diff --git a/security/keys/trusted-keys/tpm2key.asn1 b/security/keys/trusted-keys/tpm2key.asn1
deleted file mode 100644
index f57f869ad600..000000000000
--- a/security/keys/trusted-keys/tpm2key.asn1
+++ /dev/null
@@ -1,11 +0,0 @@ 
----
---- ASN.1 for TPM 2.0 keys
----
-
-TPMKey ::= SEQUENCE {
-	type		OBJECT IDENTIFIER ({tpm2_key_type}),
-	emptyAuth	[0] EXPLICIT BOOLEAN OPTIONAL,
-	parent		INTEGER ({tpm2_key_parent}),
-	pubkey		OCTET STRING ({tpm2_key_pub}),
-	privkey		OCTET STRING ({tpm2_key_priv})
-	}
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 06c8fa7b21ae..b9e505e99e8c 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -13,11 +13,10 @@ 
 
 #include <keys/trusted-type.h>
 #include <keys/trusted_tpm.h>
+#include <crypto/tpm2_key.h>
 
 #include <asm/unaligned.h>
 
-#include "tpm2key.asn1.h"
-
 static struct tpm2_hash tpm2_hash_map[] = {
 	{HASH_ALGO_SHA1, TPM_ALG_SHA1},
 	{HASH_ALGO_SHA256, TPM_ALG_SHA256},
@@ -98,106 +97,6 @@  static int tpm2_key_encode(struct trusted_key_payload *payload,
 	return ret;
 }
 
-struct tpm2_key_context {
-	u32 parent;
-	const u8 *pub;
-	u32 pub_len;
-	const u8 *priv;
-	u32 priv_len;
-};
-
-static int tpm2_key_decode(struct trusted_key_payload *payload,
-			   struct trusted_key_options *options,
-			   u8 **buf)
-{
-	int ret;
-	struct tpm2_key_context ctx;
-	u8 *blob;
-
-	memset(&ctx, 0, sizeof(ctx));
-
-	ret = asn1_ber_decoder(&tpm2key_decoder, &ctx, payload->blob,
-			       payload->blob_len);
-	if (ret < 0)
-		return ret;
-
-	if (ctx.priv_len + ctx.pub_len > MAX_BLOB_SIZE)
-		return -E2BIG;
-
-	blob = kmalloc(ctx.priv_len + ctx.pub_len + 4, GFP_KERNEL);
-	if (!blob)
-		return -ENOMEM;
-
-	*buf = blob;
-	options->keyhandle = ctx.parent;
-
-	memcpy(blob, ctx.priv, ctx.priv_len);
-	blob += ctx.priv_len;
-
-	memcpy(blob, ctx.pub, ctx.pub_len);
-
-	return 0;
-}
-
-int tpm2_key_parent(void *context, size_t hdrlen,
-		  unsigned char tag,
-		  const void *value, size_t vlen)
-{
-	struct tpm2_key_context *ctx = context;
-	const u8 *v = value;
-	int i;
-
-	ctx->parent = 0;
-	for (i = 0; i < vlen; i++) {
-		ctx->parent <<= 8;
-		ctx->parent |= v[i];
-	}
-
-	return 0;
-}
-
-int tpm2_key_type(void *context, size_t hdrlen,
-		unsigned char tag,
-		const void *value, size_t vlen)
-{
-	enum OID oid = look_up_OID(value, vlen);
-
-	if (oid != OID_TPMSealedData) {
-		char buffer[50];
-
-		sprint_oid(value, vlen, buffer, sizeof(buffer));
-		pr_debug("OID is \"%s\" which is not TPMSealedData\n",
-			 buffer);
-		return -EINVAL;
-	}
-
-	return 0;
-}
-
-int tpm2_key_pub(void *context, size_t hdrlen,
-	       unsigned char tag,
-	       const void *value, size_t vlen)
-{
-	struct tpm2_key_context *ctx = context;
-
-	ctx->pub = value;
-	ctx->pub_len = vlen;
-
-	return 0;
-}
-
-int tpm2_key_priv(void *context, size_t hdrlen,
-		unsigned char tag,
-		const void *value, size_t vlen)
-{
-	struct tpm2_key_context *ctx = context;
-
-	ctx->priv = value;
-	ctx->priv_len = vlen;
-
-	return 0;
-}
-
 /**
  * tpm2_buf_append_auth() - append TPMS_AUTH_COMMAND to the buffer.
  *
@@ -387,22 +286,43 @@  static int tpm2_load_cmd(struct tpm_chip *chip,
 			 struct trusted_key_options *options,
 			 u32 *blob_handle)
 {
-	struct tpm_buf buf;
 	unsigned int private_len;
 	unsigned int public_len;
 	unsigned int blob_len;
-	u8 *blob, *pub;
-	int rc;
+	struct tpm2_key *key;
+	const u8 *blob, *pub;
+	struct tpm_buf buf;
 	u32 attrs;
+	int rc;
 
-	rc = tpm2_key_decode(payload, options, &blob);
-	if (rc) {
-		/* old form */
+	key = tpm2_key_decode(payload->blob, payload->blob_len);
+	if (IS_ERR(key)) {
+		/* Get the error code and reset the pointer to the key: */
+		rc = PTR_ERR(key);
+		key = NULL;
+
+		if (rc == -ENOMEM)
+			return -ENOMEM;
+
+		/* A sanity check, as only -EBADMSG or -ENOMEM are expected: */
+		if (rc != -EBADMSG)
+			pr_err("tpm2_key_decode(): spurious error code %d\n", rc);
+
+		/* Fallback to the legacy format: */
 		blob = payload->blob;
 		payload->old_format = 1;
+	} else {
+		blob = tpm2_key_data(key);
+		if (key->oid != OID_TPMSealedData) {
+			kfree(key);
+			return -EBADMSG;
+		}
 	}
 
-	/* new format carries keyhandle but old format doesn't */
+	/*
+	 * Must be non-zero here, either extracted from the ASN.1 for the new
+	 * format or specified on the command line for the old.
+	 */
 	if (!options->keyhandle)
 		return -EINVAL;
 
@@ -464,8 +384,7 @@  static int tpm2_load_cmd(struct tpm_chip *chip,
 			(__be32 *) &buf.data[TPM_HEADER_SIZE]);
 
 out:
-	if (blob != payload->blob)
-		kfree(blob);
+	kfree(key);
 	tpm_buf_destroy(&buf);
 
 	if (rc > 0)