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/*
* TPM utility functions
*
* Copyright (c) 2010 - 2015 IBM Corporation
* Authors:
* Stefan Berger <stefanb@us.ibm.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>
*/
#include "tpm_util.h"
#include "tpm_int.h"
/*
* A basic test of a TPM device. We expect a well formatted response header
* (error response is fine) within one second.
*/
static int tpm_util_test(int fd,
unsigned char *request,
size_t requestlen,
uint16_t *return_tag)
{
struct tpm_resp_hdr *resp;
fd_set readfds;
int n;
struct timeval tv = {
.tv_sec = 1,
.tv_usec = 0,
};
unsigned char buf[1024];
n = write(fd, request, requestlen);
if (n < 0) {
return errno;
}
if (n != requestlen) {
return EFAULT;
}
FD_ZERO(&readfds);
FD_SET(fd, &readfds);
/* wait for a second */
n = select(fd + 1, &readfds, NULL, NULL, &tv);
if (n != 1) {
return errno;
}
n = read(fd, &buf, sizeof(buf));
if (n < sizeof(struct tpm_resp_hdr)) {
return EFAULT;
}
resp = (struct tpm_resp_hdr *)buf;
/* check the header */
if (be32_to_cpu(resp->len) != n) {
return EBADMSG;
}
*return_tag = be16_to_cpu(resp->tag);
return 0;
}
/*
* Probe for the TPM device in the back
* Returns 0 on success with the version of the probed TPM set, 1 on failure.
*/
int tpm_util_test_tpmdev(int tpm_fd, TPMVersion *tpm_version)
{
/*
* Sending a TPM1.2 command to a TPM2 should return a TPM1.2
* header (tag = 0xc4) and error code (TPM_BADTAG = 0x1e)
*
* Sending a TPM2 command to a TPM 2 will give a TPM 2 tag in the
* header.
* Sending a TPM2 command to a TPM 1.2 will give a TPM 1.2 tag
* in the header and an error code.
*/
const struct tpm_req_hdr test_req = {
.tag = cpu_to_be16(TPM_TAG_RQU_COMMAND),
.len = cpu_to_be32(sizeof(test_req)),
.ordinal = cpu_to_be32(TPM_ORD_GetTicks),
};
const struct tpm_req_hdr test_req_tpm2 = {
.tag = cpu_to_be16(TPM2_ST_NO_SESSIONS),
.len = cpu_to_be32(sizeof(test_req_tpm2)),
.ordinal = cpu_to_be32(TPM2_CC_ReadClock),
};
uint16_t return_tag;
int ret;
/* Send TPM 2 command */
ret = tpm_util_test(tpm_fd, (unsigned char *)&test_req_tpm2,
sizeof(test_req_tpm2), &return_tag);
/* TPM 2 would respond with a tag of TPM2_ST_NO_SESSIONS */
if (!ret && return_tag == TPM2_ST_NO_SESSIONS) {
*tpm_version = TPM_VERSION_2_0;
return 0;
}
/* Send TPM 1.2 command */
ret = tpm_util_test(tpm_fd, (unsigned char *)&test_req,
sizeof(test_req), &return_tag);
if (!ret && return_tag == TPM_TAG_RSP_COMMAND) {
*tpm_version = TPM_VERSION_1_2;
/* this is a TPM 1.2 */
return 0;
}
*tpm_version = TPM_VERSION_UNSPEC;
return 1;
}
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