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authorJames Bottomley <James.Bottomley@HansenPartnership.com>2021-01-27 11:06:16 -0800
committerJarkko Sakkinen <jarkko@kernel.org>2021-04-14 16:30:30 +0300
commitf2219745250f388edacabe6cca73654131c67d0a (patch)
tree051936ef02a33f9a08ab24994178b7cff3d6b946
parentde66514d934d70ce73c302ce0644b54970fc7196 (diff)
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security: keys: trusted: use ASN.1 TPM2 key format for the blobs
Modify the TPM2 key format blob output to export and import in the ASN.1 form for TPM2 sealed object keys. For compatibility with prior trusted keys, the importer will also accept two TPM2B quantities representing the public and private parts of the key. However, the export via keyctl pipe will only output the ASN.1 format. The benefit of the ASN.1 format is that it's a standard and thus the exported key can be used by userspace tools (openssl_tpm2_engine, openconnect and tpm2-tss-engine). The format includes policy specifications, thus it gets us out of having to construct policy handles in userspace and the format includes the parent meaning you don't have to keep passing it in each time. This patch only implements basic handling for the ASN.1 format, so keys with passwords but no policy. Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com> Tested-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
-rw-r--r--Documentation/security/keys/trusted-encrypted.rst58
-rw-r--r--include/keys/trusted-type.h1
-rw-r--r--security/keys/Kconfig3
-rw-r--r--security/keys/trusted-keys/Makefile3
-rw-r--r--security/keys/trusted-keys/tpm2key.asn111
-rw-r--r--security/keys/trusted-keys/trusted_tpm1.c2
-rw-r--r--security/keys/trusted-keys/trusted_tpm2.c210
7 files changed, 280 insertions, 8 deletions
diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index 1da879a68640..549aa1308949 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -207,3 +207,61 @@ about the usage can be found in the file
Another new format 'enc32' has been defined in order to support encrypted keys
with payload size of 32 bytes. This will initially be used for nvdimm security
but may expand to other usages that require 32 bytes payload.
+
+
+TPM 2.0 ASN.1 Key Format
+------------------------
+
+The TPM 2.0 ASN.1 key format is designed to be easily recognisable,
+even in binary form (fixing a problem we had with the TPM 1.2 ASN.1
+format) and to be extensible for additions like importable keys and
+policy::
+
+ TPMKey ::= SEQUENCE {
+ type OBJECT IDENTIFIER
+ emptyAuth [0] EXPLICIT BOOLEAN OPTIONAL
+ parent INTEGER
+ pubkey OCTET STRING
+ privkey OCTET STRING
+ }
+
+type is what distinguishes the key even in binary form since the OID
+is provided by the TCG to be unique and thus forms a recognizable
+binary pattern at offset 3 in the key. The OIDs currently made
+available are::
+
+ 2.23.133.10.1.3 TPM Loadable key. This is an asymmetric key (Usually
+ RSA2048 or Elliptic Curve) which can be imported by a
+ TPM2_Load() operation.
+
+ 2.23.133.10.1.4 TPM Importable Key. This is an asymmetric key (Usually
+ RSA2048 or Elliptic Curve) which can be imported by a
+ TPM2_Import() operation.
+
+ 2.23.133.10.1.5 TPM Sealed Data. This is a set of data (up to 128
+ bytes) which is sealed by the TPM. It usually
+ represents a symmetric key and must be unsealed before
+ use.
+
+The trusted key code only uses the TPM Sealed Data OID.
+
+emptyAuth is true if the key has well known authorization "". If it
+is false or not present, the key requires an explicit authorization
+phrase. This is used by most user space consumers to decide whether
+to prompt for a password.
+
+parent represents the parent key handle, either in the 0x81 MSO space,
+like 0x81000001 for the RSA primary storage key. Userspace programmes
+also support specifying the primary handle in the 0x40 MSO space. If
+this happens the Elliptic Curve variant of the primary key using the
+TCG defined template will be generated on the fly into a volatile
+object and used as the parent. The current kernel code only supports
+the 0x81 MSO form.
+
+pubkey is the binary representation of TPM2B_PRIVATE excluding the
+initial TPM2B header, which can be reconstructed from the ASN.1 octet
+string length.
+
+privkey is the binary representation of TPM2B_PUBLIC excluding the
+initial TPM2B header which can be reconstructed from the ASN.1 octed
+string length.
diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index b2ed3481c6a0..b2d87ad21714 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -22,6 +22,7 @@ struct trusted_key_payload {
unsigned int key_len;
unsigned int blob_len;
unsigned char migratable;
+ unsigned char old_format;
unsigned char key[MAX_KEY_SIZE + 1];
unsigned char blob[MAX_BLOB_SIZE];
};
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index c161642a8484..64b81abd087e 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -75,6 +75,9 @@ config TRUSTED_KEYS
select CRYPTO_HMAC
select CRYPTO_SHA1
select CRYPTO_HASH_INFO
+ select ASN1_ENCODER
+ select OID_REGISTRY
+ select ASN1
help
This option provides support for creating, sealing, and unsealing
keys in the kernel. Trusted keys are random number symmetric keys,
diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
index 7b73cebbb378..1e17ab7bf3c5 100644
--- a/security/keys/trusted-keys/Makefile
+++ b/security/keys/trusted-keys/Makefile
@@ -5,4 +5,7 @@
obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
trusted-y += trusted_tpm1.o
+
+$(obj)/trusted_tpm2.o: $(obj)/tpm2key.asn1.h
trusted-y += trusted_tpm2.o
+trusted-y += tpm2key.asn1.o
diff --git a/security/keys/trusted-keys/tpm2key.asn1 b/security/keys/trusted-keys/tpm2key.asn1
new file mode 100644
index 000000000000..f57f869ad600
--- /dev/null
+++ b/security/keys/trusted-keys/tpm2key.asn1
@@ -0,0 +1,11 @@
+---
+--- 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_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index 1e13c9f7ea8c..713b79576840 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -1021,7 +1021,7 @@ static int trusted_instantiate(struct key *key,
goto out;
}
- if (!options->keyhandle) {
+ if (!options->keyhandle && !tpm2) {
ret = -EINVAL;
goto out;
}
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index ac361aa7f3f1..68249db98a4c 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -4,6 +4,8 @@
* Copyright (C) 2014 Intel Corporation
*/
+#include <linux/asn1_encoder.h>
+#include <linux/oid_registry.h>
#include <linux/string.h>
#include <linux/err.h>
#include <linux/tpm.h>
@@ -12,6 +14,10 @@
#include <keys/trusted-type.h>
#include <keys/trusted_tpm.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},
@@ -20,6 +26,165 @@ static struct tpm2_hash tpm2_hash_map[] = {
{HASH_ALGO_SM3_256, TPM_ALG_SM3_256},
};
+static u32 tpm2key_oid[] = { 2, 23, 133, 10, 1, 5 };
+
+static int tpm2_key_encode(struct trusted_key_payload *payload,
+ struct trusted_key_options *options,
+ u8 *src, u32 len)
+{
+ const int SCRATCH_SIZE = PAGE_SIZE;
+ u8 *scratch = kmalloc(SCRATCH_SIZE, GFP_KERNEL);
+ u8 *work = scratch, *work1;
+ u8 *end_work = scratch + SCRATCH_SIZE;
+ u8 *priv, *pub;
+ u16 priv_len, pub_len;
+
+ priv_len = get_unaligned_be16(src) + 2;
+ priv = src;
+
+ src += priv_len;
+
+ pub_len = get_unaligned_be16(src) + 2;
+ pub = src;
+
+ if (!scratch)
+ return -ENOMEM;
+
+ work = asn1_encode_oid(work, end_work, tpm2key_oid,
+ asn1_oid_len(tpm2key_oid));
+
+ if (options->blobauth_len == 0) {
+ unsigned char bool[3], *w = bool;
+ /* tag 0 is emptyAuth */
+ w = asn1_encode_boolean(w, w + sizeof(bool), true);
+ if (WARN(IS_ERR(w), "BUG: Boolean failed to encode"))
+ return PTR_ERR(w);
+ work = asn1_encode_tag(work, end_work, 0, bool, w - bool);
+ }
+
+ /*
+ * Assume both octet strings will encode to a 2 byte definite length
+ *
+ * Note: For a well behaved TPM, this warning should never
+ * trigger, so if it does there's something nefarious going on
+ */
+ if (WARN(work - scratch + pub_len + priv_len + 14 > SCRATCH_SIZE,
+ "BUG: scratch buffer is too small"))
+ return -EINVAL;
+
+ work = asn1_encode_integer(work, end_work, options->keyhandle);
+ work = asn1_encode_octet_string(work, end_work, pub, pub_len);
+ work = asn1_encode_octet_string(work, end_work, priv, priv_len);
+
+ work1 = payload->blob;
+ work1 = asn1_encode_sequence(work1, work1 + sizeof(payload->blob),
+ scratch, work - scratch);
+ if (WARN(IS_ERR(work1), "BUG: ASN.1 encoder failed"))
+ return PTR_ERR(work1);
+
+ return work1 - payload->blob;
+}
+
+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 -EINVAL;
+
+ 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;
+}
+
/**
* tpm_buf_append_auth() - append TPMS_AUTH_COMMAND to the buffer.
*
@@ -63,7 +228,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
struct trusted_key_payload *payload,
struct trusted_key_options *options)
{
- unsigned int blob_len;
+ int blob_len = 0;
struct tpm_buf buf;
u32 hash;
int i;
@@ -79,6 +244,9 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
if (i == ARRAY_SIZE(tpm2_hash_map))
return -EINVAL;
+ if (!options->keyhandle)
+ return -EINVAL;
+
rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
if (rc)
return rc;
@@ -152,8 +320,9 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
goto out;
}
- memcpy(payload->blob, &buf.data[TPM_HEADER_SIZE + 4], blob_len);
- payload->blob_len = blob_len;
+ blob_len = tpm2_key_encode(payload, options,
+ &buf.data[TPM_HEADER_SIZE + 4],
+ blob_len);
out:
tpm_buf_destroy(&buf);
@@ -164,6 +333,10 @@ out:
else
rc = -EPERM;
}
+ if (blob_len < 0)
+ return blob_len;
+
+ payload->blob_len = blob_len;
tpm_put_ops(chip);
return rc;
@@ -191,13 +364,34 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
unsigned int private_len;
unsigned int public_len;
unsigned int blob_len;
+ u8 *blob;
int rc;
- private_len = be16_to_cpup((__be16 *) &payload->blob[0]);
- if (private_len > (payload->blob_len - 2))
+ rc = tpm2_key_decode(payload, options, &blob);
+ if (rc) {
+ /* old form */
+ blob = payload->blob;
+ payload->old_format = 1;
+ }
+
+ /* new format carries keyhandle but old format doesn't */
+ if (!options->keyhandle)
+ return -EINVAL;
+
+ /* must be big enough for at least the two be16 size counts */
+ if (payload->blob_len < 4)
+ return -EINVAL;
+
+ private_len = get_unaligned_be16(blob);
+
+ /* must be big enough for following public_len */
+ if (private_len + 2 + 2 > (payload->blob_len))
+ return -E2BIG;
+
+ public_len = get_unaligned_be16(blob + 2 + private_len);
+ if (private_len + 2 + public_len + 2 > payload->blob_len)
return -E2BIG;
- public_len = be16_to_cpup((__be16 *) &payload->blob[2 + private_len]);
blob_len = private_len + public_len + 4;
if (blob_len > payload->blob_len)
return -E2BIG;
@@ -213,7 +407,7 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
options->keyauth /* hmac */,
TPM_DIGEST_SIZE);
- tpm_buf_append(&buf, payload->blob, blob_len);
+ tpm_buf_append(&buf, blob, blob_len);
if (buf.flags & TPM_BUF_OVERFLOW) {
rc = -E2BIG;
@@ -226,6 +420,8 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
(__be32 *) &buf.data[TPM_HEADER_SIZE]);
out:
+ if (blob != payload->blob)
+ kfree(blob);
tpm_buf_destroy(&buf);
if (rc > 0)