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KEYS: asym_tpm: Implement the decrypt operation [ver #2]

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This patch implements the pkey_decrypt operation using the private key
blob.  The blob is first loaded into the TPM via tpm_loadkey2.  Once the
handle is obtained, tpm_unbind operation is used to decrypt the data on
the TPM and the result is returned.  The key loaded by tpm_loadkey2 is
then evicted via tpm_flushspecific operation.

This patch assumes that the SRK authorization is a well known 20-byte of
zeros and the same holds for the key authorization of the provided key.

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>
This commit is contained in:
Denis Kenzior 2018-10-09 17:49:13 +01:00 committed by James Morris
parent f884fe5a15
commit a335974ae0
1 changed files with 57 additions and 1 deletions
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58
crypto/asymmetric_keys/asym_tpm.c
View file

@ -341,7 +341,8 @@ static int tpm_key_query(const struct kernel_pkey_params *params,
info->max_enc_size = len;
info->max_dec_size = tk->key_len / 8;
info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT;
info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT |
KEYCTL_SUPPORTS_DECRYPT;
ret = 0;
error_free_tfm:
@ -410,6 +411,58 @@ error_free_tfm:
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;
}
/*
* Do encryption, decryption and signing ops.
*/
@ -424,6 +477,9 @@ static int tpm_key_eds_op(struct kernel_pkey_params *params,
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;
default:
BUG();
}