Re: [PATCH v7 3/5] crypto: tpm2_key: Introduce a TPM2 key type
From: Stefan Berger
Date: Thu May 30 2024 - 20:36:18 EST
On 5/28/24 17:08, Jarkko Sakkinen wrote:
TPM2 ASN.1 format is required for trusted keys and asymmetric keys. Move it
to crypto in order to make it available for both. Implement validation with
coverage of all TPMT_PUBLIC shared fields. Key type specific fields must be
covered by the different subsystems using this.
A Kconfig option CRYPTO_TPM2_KEY can be used to select the feature, which
depends only crypto subsystem itself and ASN.1 parser.
Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
---
v6:
* Relocate to crypto. Validate the shared part and provide
accessor functions. Use a fixed buffer size.
v2:
* Do not allocate blob twice. Use the one inside struct tpm2_key.
---
crypto/Kconfig | 7 ++
crypto/Makefile | 6 +
crypto/tpm2_key.asn1 | 11 ++
crypto/tpm2_key.c | 134 ++++++++++++++++++++
include/crypto/tpm2_key.h | 46 +++++++
security/keys/trusted-keys/Kconfig | 2 +-
security/keys/trusted-keys/Makefile | 2 -
security/keys/trusted-keys/tpm2key.asn1 | 11 --
security/keys/trusted-keys/trusted_tpm2.c | 141 +++++-----------------
9 files changed, 235 insertions(+), 125 deletions(-)
create mode 100644 crypto/tpm2_key.asn1
create mode 100644 crypto/tpm2_key.c
create mode 100644 include/crypto/tpm2_key.h
delete mode 100644 security/keys/trusted-keys/tpm2key.asn1
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.
I am not sure what the last sentence means.
+ *
+ * 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);
tpm2_key_decode seems simple enough that it only returns key, -ENOMEM or
EBADMSG.
+
+ /* 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.
sentence seems incomplete: ... for the old one. OR ... for the old format.
+ */
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)