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linux-stable/crypto/asymmetric_keys/asym_tpm.c
Denis Kenzior 64ae16dfee KEYS: asym_tpm: Add support for the sign operation [ver #2] 
The sign operation can operate in a non-hashed mode by running the RSA
sign operation directly on the input.  This assumes that the input is
less than key_size_in_bytes - 11.  Since the TPM performs its own PKCS1
padding, it isn't possible to support 'raw' mode, only 'pkcs1'.

Alternatively, a hashed version is also possible.  In this variant the
input is hashed (by userspace) via the selected hash function first.
Then this implementation takes care of converting the hash to ASN.1
format and the sign operation is performed on the result.  This is
similar to the implementation inside crypto/rsa-pkcs1pad.c.

ASN1 templates were copied from crypto/rsa-pkcs1pad.c.  There seems to
be no easy way to expose that functionality, but likely the templates
should be shared somehow.

The sign operation is implemented via TPM_Sign operation on the TPM.
It is assumed that the TPM wrapped key provided uses
TPM_SS_RSASSAPKCS1v15_DER signature scheme.  This allows the TPM_Sign
operation to work on data up to key_len_in_bytes - 11 bytes long.

In theory, we could also use TPM_Unbind instead of TPM_Sign, but we would
have to manually pkcs1 pad the digest first.

Signed-off-by: Denis Kenzior <denkenz@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Marcel Holtmann <marcel@holtmann.org>
Reviewed-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: James Morris <james.morris@microsoft.com>
2018-10-26 09:30:47 +01:00

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// SPDX-License-Identifier: GPL-2.0
#define pr_fmt(fmt) "ASYM-TPM: "fmt
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/seq_file.h>
#include <linux/scatterlist.h>
#include <linux/tpm.h>
#include <linux/tpm_command.h>
#include <crypto/akcipher.h>
#include <crypto/hash.h>
#include <crypto/sha.h>
#include <asm/unaligned.h>
#include <keys/asymmetric-subtype.h>
#include <keys/trusted.h>
#include <crypto/asym_tpm_subtype.h>
#include <crypto/public_key.h>
#define TPM_ORD_FLUSHSPECIFIC 186
#define TPM_ORD_LOADKEY2 65
#define TPM_ORD_UNBIND 30
#define TPM_ORD_SIGN 60
#define TPM_LOADKEY2_SIZE 59
#define TPM_FLUSHSPECIFIC_SIZE 18
#define TPM_UNBIND_SIZE 63
#define TPM_SIGN_SIZE 63
#define TPM_RT_KEY 0x00000001
/*
* Load a TPM key from the blob provided by userspace
*/
static int tpm_loadkey2(struct tpm_buf *tb,
uint32_t keyhandle, unsigned char *keyauth,
const unsigned char *keyblob, int keybloblen,
uint32_t *newhandle)
{
unsigned char nonceodd[TPM_NONCE_SIZE];
unsigned char enonce[TPM_NONCE_SIZE];
unsigned char authdata[SHA1_DIGEST_SIZE];
uint32_t authhandle = 0;
unsigned char cont = 0;
uint32_t ordinal;
int ret;
ordinal = htonl(TPM_ORD_LOADKEY2);
/* session for loading the key */
ret = oiap(tb, &authhandle, enonce);
if (ret < 0) {
pr_info("oiap failed (%d)\n", ret);
return ret;
}
/* generate odd nonce */
ret = tpm_get_random(NULL, nonceodd, TPM_NONCE_SIZE);
if (ret < 0) {
pr_info("tpm_get_random failed (%d)\n", ret);
return ret;
}
/* calculate authorization HMAC value */
ret = TSS_authhmac(authdata, keyauth, SHA1_DIGEST_SIZE, enonce,
nonceodd, cont, sizeof(uint32_t), &ordinal,
keybloblen, keyblob, 0, 0);
if (ret < 0)
return ret;
/* build the request buffer */
INIT_BUF(tb);
store16(tb, TPM_TAG_RQU_AUTH1_COMMAND);
store32(tb, TPM_LOADKEY2_SIZE + keybloblen);
store32(tb, TPM_ORD_LOADKEY2);
store32(tb, keyhandle);
storebytes(tb, keyblob, keybloblen);
store32(tb, authhandle);
storebytes(tb, nonceodd, TPM_NONCE_SIZE);
store8(tb, cont);
storebytes(tb, authdata, SHA1_DIGEST_SIZE);
ret = trusted_tpm_send(tb->data, MAX_BUF_SIZE);
if (ret < 0) {
pr_info("authhmac failed (%d)\n", ret);
return ret;
}
ret = TSS_checkhmac1(tb->data, ordinal, nonceodd, keyauth,
SHA1_DIGEST_SIZE, 0, 0);
if (ret < 0) {
pr_info("TSS_checkhmac1 failed (%d)\n", ret);
return ret;
}
*newhandle = LOAD32(tb->data, TPM_DATA_OFFSET);
return 0;
}
/*
* Execute the FlushSpecific TPM command
*/
static int tpm_flushspecific(struct tpm_buf *tb, uint32_t handle)
{
INIT_BUF(tb);
store16(tb, TPM_TAG_RQU_COMMAND);
store32(tb, TPM_FLUSHSPECIFIC_SIZE);
store32(tb, TPM_ORD_FLUSHSPECIFIC);
store32(tb, handle);
store32(tb, TPM_RT_KEY);
return trusted_tpm_send(tb->data, MAX_BUF_SIZE);
}
/*
* Decrypt a blob provided by userspace using a specific key handle.
* The handle is a well known handle or previously loaded by e.g. LoadKey2
*/
static int tpm_unbind(struct tpm_buf *tb,
uint32_t keyhandle, unsigned char *keyauth,
const unsigned char *blob, uint32_t bloblen,
void *out, uint32_t outlen)
{
unsigned char nonceodd[TPM_NONCE_SIZE];
unsigned char enonce[TPM_NONCE_SIZE];
unsigned char authdata[SHA1_DIGEST_SIZE];
uint32_t authhandle = 0;
unsigned char cont = 0;
uint32_t ordinal;
uint32_t datalen;
int ret;
ordinal = htonl(TPM_ORD_UNBIND);
datalen = htonl(bloblen);
/* session for loading the key */
ret = oiap(tb, &authhandle, enonce);
if (ret < 0) {
pr_info("oiap failed (%d)\n", ret);
return ret;
}
/* generate odd nonce */
ret = tpm_get_random(NULL, nonceodd, TPM_NONCE_SIZE);
if (ret < 0) {
pr_info("tpm_get_random failed (%d)\n", ret);
return ret;
}
/* calculate authorization HMAC value */
ret = TSS_authhmac(authdata, keyauth, SHA1_DIGEST_SIZE, enonce,
nonceodd, cont, sizeof(uint32_t), &ordinal,
sizeof(uint32_t), &datalen,
bloblen, blob, 0, 0);
if (ret < 0)
return ret;
/* build the request buffer */
INIT_BUF(tb);
store16(tb, TPM_TAG_RQU_AUTH1_COMMAND);
store32(tb, TPM_UNBIND_SIZE + bloblen);
store32(tb, TPM_ORD_UNBIND);
store32(tb, keyhandle);
store32(tb, bloblen);
storebytes(tb, blob, bloblen);
store32(tb, authhandle);
storebytes(tb, nonceodd, TPM_NONCE_SIZE);
store8(tb, cont);
storebytes(tb, authdata, SHA1_DIGEST_SIZE);
ret = trusted_tpm_send(tb->data, MAX_BUF_SIZE);
if (ret < 0) {
pr_info("authhmac failed (%d)\n", ret);
return ret;
}
datalen = LOAD32(tb->data, TPM_DATA_OFFSET);
ret = TSS_checkhmac1(tb->data, ordinal, nonceodd,
keyauth, SHA1_DIGEST_SIZE,
sizeof(uint32_t), TPM_DATA_OFFSET,
datalen, TPM_DATA_OFFSET + sizeof(uint32_t),
0, 0);
if (ret < 0) {
pr_info("TSS_checkhmac1 failed (%d)\n", ret);
return ret;
}
memcpy(out, tb->data + TPM_DATA_OFFSET + sizeof(uint32_t),
min(outlen, datalen));
return datalen;
}
/*
* Sign a blob provided by userspace (that has had the hash function applied)
* using a specific key handle. The handle is assumed to have been previously
* loaded by e.g. LoadKey2.
*
* Note that the key signature scheme of the used key should be set to
* TPM_SS_RSASSAPKCS1v15_DER. This allows the hashed input to be of any size
* up to key_length_in_bytes - 11 and not be limited to size 20 like the
* TPM_SS_RSASSAPKCS1v15_SHA1 signature scheme.
*/
static int tpm_sign(struct tpm_buf *tb,
uint32_t keyhandle, unsigned char *keyauth,
const unsigned char *blob, uint32_t bloblen,
void *out, uint32_t outlen)
{
unsigned char nonceodd[TPM_NONCE_SIZE];
unsigned char enonce[TPM_NONCE_SIZE];
unsigned char authdata[SHA1_DIGEST_SIZE];
uint32_t authhandle = 0;
unsigned char cont = 0;
uint32_t ordinal;
uint32_t datalen;
int ret;
ordinal = htonl(TPM_ORD_SIGN);
datalen = htonl(bloblen);
/* session for loading the key */
ret = oiap(tb, &authhandle, enonce);
if (ret < 0) {
pr_info("oiap failed (%d)\n", ret);
return ret;
}
/* generate odd nonce */
ret = tpm_get_random(NULL, nonceodd, TPM_NONCE_SIZE);
if (ret < 0) {
pr_info("tpm_get_random failed (%d)\n", ret);
return ret;
}
/* calculate authorization HMAC value */
ret = TSS_authhmac(authdata, keyauth, SHA1_DIGEST_SIZE, enonce,
nonceodd, cont, sizeof(uint32_t), &ordinal,
sizeof(uint32_t), &datalen,
bloblen, blob, 0, 0);
if (ret < 0)
return ret;
/* build the request buffer */
INIT_BUF(tb);
store16(tb, TPM_TAG_RQU_AUTH1_COMMAND);
store32(tb, TPM_SIGN_SIZE + bloblen);
store32(tb, TPM_ORD_SIGN);
store32(tb, keyhandle);
store32(tb, bloblen);
storebytes(tb, blob, bloblen);
store32(tb, authhandle);
storebytes(tb, nonceodd, TPM_NONCE_SIZE);
store8(tb, cont);
storebytes(tb, authdata, SHA1_DIGEST_SIZE);
ret = trusted_tpm_send(tb->data, MAX_BUF_SIZE);
if (ret < 0) {
pr_info("authhmac failed (%d)\n", ret);
return ret;
}
datalen = LOAD32(tb->data, TPM_DATA_OFFSET);
ret = TSS_checkhmac1(tb->data, ordinal, nonceodd,
keyauth, SHA1_DIGEST_SIZE,
sizeof(uint32_t), TPM_DATA_OFFSET,
datalen, TPM_DATA_OFFSET + sizeof(uint32_t),
0, 0);
if (ret < 0) {
pr_info("TSS_checkhmac1 failed (%d)\n", ret);
return ret;
}
memcpy(out, tb->data + TPM_DATA_OFFSET + sizeof(uint32_t),
min(datalen, outlen));
return datalen;
}
/*
* Maximum buffer size for the BER/DER encoded public key. The public key
* is of the form SEQUENCE { INTEGER n, INTEGER e } where n is a maximum 2048
* bit key and e is usually 65537
* The encoding overhead is:
* - max 4 bytes for SEQUENCE
* - max 4 bytes for INTEGER n type/length
* - 257 bytes of n
* - max 2 bytes for INTEGER e type/length
* - 3 bytes of e
*/
#define PUB_KEY_BUF_SIZE (4 + 4 + 257 + 2 + 3)
/*
* Provide a part of a description of the key for /proc/keys.
*/
static void asym_tpm_describe(const struct key *asymmetric_key,
struct seq_file *m)
{
struct tpm_key *tk = asymmetric_key->payload.data[asym_crypto];
if (!tk)
return;
seq_printf(m, "TPM1.2/Blob");
}
static void asym_tpm_destroy(void *payload0, void *payload3)
{
struct tpm_key *tk = payload0;
if (!tk)
return;
kfree(tk->blob);
tk->blob_len = 0;
kfree(tk);
}
/* How many bytes will it take to encode the length */
static inline uint32_t definite_length(uint32_t len)
{
if (len <= 127)
return 1;
if (len <= 255)
return 2;
return 3;
}
static inline uint8_t *encode_tag_length(uint8_t *buf, uint8_t tag,
uint32_t len)
{
*buf++ = tag;
if (len <= 127) {
buf[0] = len;
return buf + 1;
}
if (len <= 255) {
buf[0] = 0x81;
buf[1] = len;
return buf + 2;
}
buf[0] = 0x82;
put_unaligned_be16(len, buf + 1);
return buf + 3;
}
static uint32_t derive_pub_key(const void *pub_key, uint32_t len, uint8_t *buf)
{
uint8_t *cur = buf;
uint32_t n_len = definite_length(len) + 1 + len + 1;
uint32_t e_len = definite_length(3) + 1 + 3;
uint8_t e[3] = { 0x01, 0x00, 0x01 };
/* SEQUENCE */
cur = encode_tag_length(cur, 0x30, n_len + e_len);
/* INTEGER n */
cur = encode_tag_length(cur, 0x02, len + 1);
cur[0] = 0x00;
memcpy(cur + 1, pub_key, len);
cur += len + 1;
cur = encode_tag_length(cur, 0x02, sizeof(e));
memcpy(cur, e, sizeof(e));
cur += sizeof(e);
return cur - buf;
}
/*
* Determine the crypto algorithm name.
*/
static int determine_akcipher(const char *encoding, const char *hash_algo,
char alg_name[CRYPTO_MAX_ALG_NAME])
{
if (strcmp(encoding, "pkcs1") == 0) {
if (!hash_algo) {
strcpy(alg_name, "pkcs1pad(rsa)");
return 0;
}
if (snprintf(alg_name, CRYPTO_MAX_ALG_NAME, "pkcs1pad(rsa,%s)",
hash_algo) >= CRYPTO_MAX_ALG_NAME)
return -EINVAL;
return 0;
}
if (strcmp(encoding, "raw") == 0) {
strcpy(alg_name, "rsa");
return 0;
}
return -ENOPKG;
}
/*
* Query information about a key.
*/
static int tpm_key_query(const struct kernel_pkey_params *params,
struct kernel_pkey_query *info)
{
struct tpm_key *tk = params->key->payload.data[asym_crypto];
int ret;
char alg_name[CRYPTO_MAX_ALG_NAME];
struct crypto_akcipher *tfm;
uint8_t der_pub_key[PUB_KEY_BUF_SIZE];
uint32_t der_pub_key_len;
int len;
/* TPM only works on private keys, public keys still done in software */
ret = determine_akcipher(params->encoding, params->hash_algo, alg_name);
if (ret < 0)
return ret;
tfm = crypto_alloc_akcipher(alg_name, 0, 0);
if (IS_ERR(tfm))
return PTR_ERR(tfm);
der_pub_key_len = derive_pub_key(tk->pub_key, tk->pub_key_len,
der_pub_key);
ret = crypto_akcipher_set_pub_key(tfm, der_pub_key, der_pub_key_len);
if (ret < 0)
goto error_free_tfm;
len = crypto_akcipher_maxsize(tfm);
info->key_size = tk->key_len;
info->max_data_size = tk->key_len / 8;
info->max_sig_size = len;
info->max_enc_size = len;
info->max_dec_size = tk->key_len / 8;
info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT |
KEYCTL_SUPPORTS_DECRYPT |
KEYCTL_SUPPORTS_VERIFY |
KEYCTL_SUPPORTS_SIGN;
ret = 0;
error_free_tfm:
crypto_free_akcipher(tfm);
pr_devel("<==%s() = %d\n", __func__, ret);
return ret;
}
/*
* Encryption operation is performed with the public key. Hence it is done
* in software
*/
static int tpm_key_encrypt(struct tpm_key *tk,
struct kernel_pkey_params *params,
const void *in, void *out)
{
char alg_name[CRYPTO_MAX_ALG_NAME];
struct crypto_akcipher *tfm;
struct akcipher_request *req;
struct crypto_wait cwait;
struct scatterlist in_sg, out_sg;
uint8_t der_pub_key[PUB_KEY_BUF_SIZE];
uint32_t der_pub_key_len;
int ret;
pr_devel("==>%s()\n", __func__);
ret = determine_akcipher(params->encoding, params->hash_algo, alg_name);
if (ret < 0)
return ret;
tfm = crypto_alloc_akcipher(alg_name, 0, 0);
if (IS_ERR(tfm))
return PTR_ERR(tfm);
der_pub_key_len = derive_pub_key(tk->pub_key, tk->pub_key_len,
der_pub_key);
ret = crypto_akcipher_set_pub_key(tfm, der_pub_key, der_pub_key_len);
if (ret < 0)
goto error_free_tfm;
req = akcipher_request_alloc(tfm, GFP_KERNEL);
if (!req)
goto error_free_tfm;
sg_init_one(&in_sg, in, params->in_len);
sg_init_one(&out_sg, out, params->out_len);
akcipher_request_set_crypt(req, &in_sg, &out_sg, params->in_len,
params->out_len);
crypto_init_wait(&cwait);
akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
CRYPTO_TFM_REQ_MAY_SLEEP,
crypto_req_done, &cwait);
ret = crypto_akcipher_encrypt(req);
ret = crypto_wait_req(ret, &cwait);
if (ret == 0)
ret = req->dst_len;
akcipher_request_free(req);
error_free_tfm:
crypto_free_akcipher(tfm);
pr_devel("<==%s() = %d\n", __func__, ret);
return ret;
}
/*
* Decryption operation is performed with the private key in the TPM.
*/
static int tpm_key_decrypt(struct tpm_key *tk,
struct kernel_pkey_params *params,
const void *in, void *out)
{
struct tpm_buf *tb;
uint32_t keyhandle;
uint8_t srkauth[SHA1_DIGEST_SIZE];
uint8_t keyauth[SHA1_DIGEST_SIZE];
int r;
pr_devel("==>%s()\n", __func__);
if (params->hash_algo)
return -ENOPKG;
if (strcmp(params->encoding, "pkcs1"))
return -ENOPKG;
tb = kzalloc(sizeof(*tb), GFP_KERNEL);
if (!tb)
return -ENOMEM;
/* TODO: Handle a non-all zero SRK authorization */
memset(srkauth, 0, sizeof(srkauth));
r = tpm_loadkey2(tb, SRKHANDLE, srkauth,
tk->blob, tk->blob_len, &keyhandle);
if (r < 0) {
pr_devel("loadkey2 failed (%d)\n", r);
goto error;
}
/* TODO: Handle a non-all zero key authorization */
memset(keyauth, 0, sizeof(keyauth));
r = tpm_unbind(tb, keyhandle, keyauth,
in, params->in_len, out, params->out_len);
if (r < 0)
pr_devel("tpm_unbind failed (%d)\n", r);
if (tpm_flushspecific(tb, keyhandle) < 0)
pr_devel("flushspecific failed (%d)\n", r);
error:
kzfree(tb);
pr_devel("<==%s() = %d\n", __func__, r);
return r;
}
/*
* Hash algorithm OIDs plus ASN.1 DER wrappings [RFC4880 sec 5.2.2].
*/
static const u8 digest_info_md5[] = {
0x30, 0x20, 0x30, 0x0c, 0x06, 0x08,
0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x02, 0x05, /* OID */
0x05, 0x00, 0x04, 0x10
};
static const u8 digest_info_sha1[] = {
0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
0x2b, 0x0e, 0x03, 0x02, 0x1a,
0x05, 0x00, 0x04, 0x14
};
static const u8 digest_info_rmd160[] = {
0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
0x2b, 0x24, 0x03, 0x02, 0x01,
0x05, 0x00, 0x04, 0x14
};
static const u8 digest_info_sha224[] = {
0x30, 0x2d, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04,
0x05, 0x00, 0x04, 0x1c
};
static const u8 digest_info_sha256[] = {
0x30, 0x31, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01,
0x05, 0x00, 0x04, 0x20
};
static const u8 digest_info_sha384[] = {
0x30, 0x41, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02,
0x05, 0x00, 0x04, 0x30
};
static const u8 digest_info_sha512[] = {
0x30, 0x51, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03,
0x05, 0x00, 0x04, 0x40
};
static const struct asn1_template {
const char *name;
const u8 *data;
size_t size;
} asn1_templates[] = {
#define _(X) { #X, digest_info_##X, sizeof(digest_info_##X) }
_(md5),
_(sha1),
_(rmd160),
_(sha256),
_(sha384),
_(sha512),
_(sha224),
{ NULL }
#undef _
};
static const struct asn1_template *lookup_asn1(const char *name)
{
const struct asn1_template *p;
for (p = asn1_templates; p->name; p++)
if (strcmp(name, p->name) == 0)
return p;
return NULL;
}
/*
* Sign operation is performed with the private key in the TPM.
*/
static int tpm_key_sign(struct tpm_key *tk,
struct kernel_pkey_params *params,
const void *in, void *out)
{
struct tpm_buf *tb;
uint32_t keyhandle;
uint8_t srkauth[SHA1_DIGEST_SIZE];
uint8_t keyauth[SHA1_DIGEST_SIZE];
void *asn1_wrapped = NULL;
uint32_t in_len = params->in_len;
int r;
pr_devel("==>%s()\n", __func__);
if (strcmp(params->encoding, "pkcs1"))
return -ENOPKG;
if (params->hash_algo) {
const struct asn1_template *asn1 =
lookup_asn1(params->hash_algo);
if (!asn1)
return -ENOPKG;
/* request enough space for the ASN.1 template + input hash */
asn1_wrapped = kzalloc(in_len + asn1->size, GFP_KERNEL);
if (!asn1_wrapped)
return -ENOMEM;
/* Copy ASN.1 template, then the input */
memcpy(asn1_wrapped, asn1->data, asn1->size);
memcpy(asn1_wrapped + asn1->size, in, in_len);
in = asn1_wrapped;
in_len += asn1->size;
}
if (in_len > tk->key_len / 8 - 11) {
r = -EOVERFLOW;
goto error_free_asn1_wrapped;
}
r = -ENOMEM;
tb = kzalloc(sizeof(*tb), GFP_KERNEL);
if (!tb)
goto error_free_asn1_wrapped;
/* TODO: Handle a non-all zero SRK authorization */
memset(srkauth, 0, sizeof(srkauth));
r = tpm_loadkey2(tb, SRKHANDLE, srkauth,
tk->blob, tk->blob_len, &keyhandle);
if (r < 0) {
pr_devel("loadkey2 failed (%d)\n", r);
goto error_free_tb;
}
/* TODO: Handle a non-all zero key authorization */
memset(keyauth, 0, sizeof(keyauth));
r = tpm_sign(tb, keyhandle, keyauth, in, in_len, out, params->out_len);
if (r < 0)
pr_devel("tpm_sign failed (%d)\n", r);
if (tpm_flushspecific(tb, keyhandle) < 0)
pr_devel("flushspecific failed (%d)\n", r);
error_free_tb:
kzfree(tb);
error_free_asn1_wrapped:
kfree(asn1_wrapped);
pr_devel("<==%s() = %d\n", __func__, r);
return r;
}
/*
* Do encryption, decryption and signing ops.
*/
static int tpm_key_eds_op(struct kernel_pkey_params *params,
const void *in, void *out)
{
struct tpm_key *tk = params->key->payload.data[asym_crypto];
int ret = -EOPNOTSUPP;
/* Perform the encryption calculation. */
switch (params->op) {
case kernel_pkey_encrypt:
ret = tpm_key_encrypt(tk, params, in, out);
break;
case kernel_pkey_decrypt:
ret = tpm_key_decrypt(tk, params, in, out);
break;
case kernel_pkey_sign:
ret = tpm_key_sign(tk, params, in, out);
break;
default:
BUG();
}
return ret;
}
/*
* Verify a signature using a public key.
*/
static int tpm_key_verify_signature(const struct key *key,
const struct public_key_signature *sig)
{
const struct tpm_key *tk = key->payload.data[asym_crypto];
struct crypto_wait cwait;
struct crypto_akcipher *tfm;
struct akcipher_request *req;
struct scatterlist sig_sg, digest_sg;
char alg_name[CRYPTO_MAX_ALG_NAME];
uint8_t der_pub_key[PUB_KEY_BUF_SIZE];
uint32_t der_pub_key_len;
void *output;
unsigned int outlen;
int ret;
pr_devel("==>%s()\n", __func__);
BUG_ON(!tk);
BUG_ON(!sig);
BUG_ON(!sig->s);
if (!sig->digest)
return -ENOPKG;
ret = determine_akcipher(sig->encoding, sig->hash_algo, alg_name);
if (ret < 0)
return ret;
tfm = crypto_alloc_akcipher(alg_name, 0, 0);
if (IS_ERR(tfm))
return PTR_ERR(tfm);
der_pub_key_len = derive_pub_key(tk->pub_key, tk->pub_key_len,
der_pub_key);
ret = crypto_akcipher_set_pub_key(tfm, der_pub_key, der_pub_key_len);
if (ret < 0)
goto error_free_tfm;
ret = -ENOMEM;
req = akcipher_request_alloc(tfm, GFP_KERNEL);
if (!req)
goto error_free_tfm;
ret = -ENOMEM;
outlen = crypto_akcipher_maxsize(tfm);
output = kmalloc(outlen, GFP_KERNEL);
if (!output)
goto error_free_req;
sg_init_one(&sig_sg, sig->s, sig->s_size);
sg_init_one(&digest_sg, output, outlen);
akcipher_request_set_crypt(req, &sig_sg, &digest_sg, sig->s_size,
outlen);
crypto_init_wait(&cwait);
akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
CRYPTO_TFM_REQ_MAY_SLEEP,
crypto_req_done, &cwait);
/* Perform the verification calculation. This doesn't actually do the
* verification, but rather calculates the hash expected by the
* signature and returns that to us.
*/
ret = crypto_wait_req(crypto_akcipher_verify(req), &cwait);
if (ret)
goto out_free_output;
/* Do the actual verification step. */
if (req->dst_len != sig->digest_size ||
memcmp(sig->digest, output, sig->digest_size) != 0)
ret = -EKEYREJECTED;
out_free_output:
kfree(output);
error_free_req:
akcipher_request_free(req);
error_free_tfm:
crypto_free_akcipher(tfm);
pr_devel("<==%s() = %d\n", __func__, ret);
if (WARN_ON_ONCE(ret > 0))
ret = -EINVAL;
return ret;
}
/*
* Parse enough information out of TPM_KEY structure:
* TPM_STRUCT_VER -> 4 bytes
* TPM_KEY_USAGE -> 2 bytes
* TPM_KEY_FLAGS -> 4 bytes
* TPM_AUTH_DATA_USAGE -> 1 byte
* TPM_KEY_PARMS -> variable
* UINT32 PCRInfoSize -> 4 bytes
* BYTE* -> PCRInfoSize bytes
* TPM_STORE_PUBKEY
* UINT32 encDataSize;
* BYTE* -> encDataSize;
*
* TPM_KEY_PARMS:
* TPM_ALGORITHM_ID -> 4 bytes
* TPM_ENC_SCHEME -> 2 bytes
* TPM_SIG_SCHEME -> 2 bytes
* UINT32 parmSize -> 4 bytes
* BYTE* -> variable
*/
static int extract_key_parameters(struct tpm_key *tk)
{
const void *cur = tk->blob;
uint32_t len = tk->blob_len;
const void *pub_key;
uint32_t sz;
uint32_t key_len;
if (len < 11)
return -EBADMSG;
/* Ensure this is a legacy key */
if (get_unaligned_be16(cur + 4) != 0x0015)
return -EBADMSG;
/* Skip to TPM_KEY_PARMS */
cur += 11;
len -= 11;
if (len < 12)
return -EBADMSG;
/* Make sure this is an RSA key */
if (get_unaligned_be32(cur) != 0x00000001)
return -EBADMSG;
/* Make sure this is TPM_ES_RSAESPKCSv15 encoding scheme */
if (get_unaligned_be16(cur + 4) != 0x0002)
return -EBADMSG;
/* Make sure this is TPM_SS_RSASSAPKCS1v15_DER signature scheme */
if (get_unaligned_be16(cur + 6) != 0x0003)
return -EBADMSG;
sz = get_unaligned_be32(cur + 8);
if (len < sz + 12)
return -EBADMSG;
/* Move to TPM_RSA_KEY_PARMS */
len -= 12;
cur += 12;
/* Grab the RSA key length */
key_len = get_unaligned_be32(cur);
switch (key_len) {
case 512:
case 1024:
case 1536:
case 2048:
break;
default:
return -EINVAL;
}
/* Move just past TPM_KEY_PARMS */
cur += sz;
len -= sz;
if (len < 4)
return -EBADMSG;
sz = get_unaligned_be32(cur);
if (len < 4 + sz)
return -EBADMSG;
/* Move to TPM_STORE_PUBKEY */
cur += 4 + sz;
len -= 4 + sz;
/* Grab the size of the public key, it should jive with the key size */
sz = get_unaligned_be32(cur);
if (sz > 256)
return -EINVAL;
pub_key = cur + 4;
tk->key_len = key_len;
tk->pub_key = pub_key;
tk->pub_key_len = sz;
return 0;
}
/* Given the blob, parse it and load it into the TPM */
struct tpm_key *tpm_key_create(const void *blob, uint32_t blob_len)
{
int r;
struct tpm_key *tk;
r = tpm_is_tpm2(NULL);
if (r < 0)
goto error;
/* We don't support TPM2 yet */
if (r > 0) {
r = -ENODEV;
goto error;
}
r = -ENOMEM;
tk = kzalloc(sizeof(struct tpm_key), GFP_KERNEL);
if (!tk)
goto error;
tk->blob = kmemdup(blob, blob_len, GFP_KERNEL);
if (!tk->blob)
goto error_memdup;
tk->blob_len = blob_len;
r = extract_key_parameters(tk);
if (r < 0)
goto error_extract;
return tk;
error_extract:
kfree(tk->blob);
tk->blob_len = 0;
error_memdup:
kfree(tk);
error:
return ERR_PTR(r);
}
EXPORT_SYMBOL_GPL(tpm_key_create);
/*
* TPM-based asymmetric key subtype
*/
struct asymmetric_key_subtype asym_tpm_subtype = {
.owner = THIS_MODULE,
.name = "asym_tpm",
.name_len = sizeof("asym_tpm") - 1,
.describe = asym_tpm_describe,
.destroy = asym_tpm_destroy,
.query = tpm_key_query,
.eds_op = tpm_key_eds_op,
.verify_signature = tpm_key_verify_signature,
};
EXPORT_SYMBOL_GPL(asym_tpm_subtype);
MODULE_DESCRIPTION("TPM based asymmetric key subtype");
MODULE_AUTHOR("Intel Corporation");
MODULE_LICENSE("GPL v2");
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