LXR qemu/hw/tpm/tpm

   1/*
   2 * TPM utility functions
   3 *
   4 *  Copyright (c) 2010 - 2015 IBM Corporation
   5 *  Authors:
   6 *    Stefan Berger <stefanb@us.ibm.com>
   7 *
   8 * This library is free software; you can redistribute it and/or
   9 * modify it under the terms of the GNU Lesser General Public
  10 * License as published by the Free Software Foundation; either
  11 * version 2 of the License, or (at your option) any later version.
  12 *
  13 * This library is distributed in the hope that it will be useful,
  14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16 * Lesser General Public License for more details.
  17 *
  18 * You should have received a copy of the GNU Lesser General Public
  19 * License along with this library; if not, see <http://www.gnu.org/licenses/>
  20 */
  21
  22#include "qemu/osdep.h"
  23#include "tpm_util.h"
  24#include "tpm_int.h"
  25
  26/*
  27 * A basic test of a TPM device. We expect a well formatted response header
  28 * (error response is fine) within one second.
  29 */
  30static int tpm_util_test(int fd,
  31                         unsigned char *request,
  32                         size_t requestlen,
  33                         uint16_t *return_tag)
  34{
  35    struct tpm_resp_hdr *resp;
  36    fd_set readfds;
  37    int n;
  38    struct timeval tv = {
  39        .tv_sec = 1,
  40        .tv_usec = 0,
  41    };
  42    unsigned char buf[1024];
  43
  44    n = write(fd, request, requestlen);
  45    if (n < 0) {
  46        return errno;
  47    }
  48    if (n != requestlen) {
  49        return EFAULT;
  50    }
  51
  52    FD_ZERO(&readfds);
  53    FD_SET(fd, &readfds);
  54
  55    /* wait for a second */
  56    n = select(fd + 1, &readfds, NULL, NULL, &tv);
  57    if (n != 1) {
  58        return errno;
  59    }
  60
  61    n = read(fd, &buf, sizeof(buf));
  62    if (n < sizeof(struct tpm_resp_hdr)) {
  63        return EFAULT;
  64    }
  65
  66    resp = (struct tpm_resp_hdr *)buf;
  67    /* check the header */
  68    if (be32_to_cpu(resp->len) != n) {
  69        return EBADMSG;
  70    }
  71
  72    *return_tag = be16_to_cpu(resp->tag);
  73
  74    return 0;
  75}
  76
  77/*
  78 * Probe for the TPM device in the back
  79 * Returns 0 on success with the version of the probed TPM set, 1 on failure.
  80 */
  81int tpm_util_test_tpmdev(int tpm_fd, TPMVersion *tpm_version)
  82{
  83    /*
  84     * Sending a TPM1.2 command to a TPM2 should return a TPM1.2
  85     * header (tag = 0xc4) and error code (TPM_BADTAG = 0x1e)
  86     *
  87     * Sending a TPM2 command to a TPM 2 will give a TPM 2 tag in the
  88     * header.
  89     * Sending a TPM2 command to a TPM 1.2 will give a TPM 1.2 tag
  90     * in the header and an error code.
  91     */
  92    const struct tpm_req_hdr test_req = {
  93        .tag = cpu_to_be16(TPM_TAG_RQU_COMMAND),
  94        .len = cpu_to_be32(sizeof(test_req)),
  95        .ordinal = cpu_to_be32(TPM_ORD_GetTicks),
  96    };
  97
  98    const struct tpm_req_hdr test_req_tpm2 = {
  99        .tag = cpu_to_be16(TPM2_ST_NO_SESSIONS),
 100        .len = cpu_to_be32(sizeof(test_req_tpm2)),
 101        .ordinal = cpu_to_be32(TPM2_CC_ReadClock),
 102    };
 103    uint16_t return_tag;
 104    int ret;
 105
 106    /* Send TPM 2 command */
 107    ret = tpm_util_test(tpm_fd, (unsigned char *)&test_req_tpm2,
 108                        sizeof(test_req_tpm2), &return_tag);
 109    /* TPM 2 would respond with a tag of TPM2_ST_NO_SESSIONS */
 110    if (!ret && return_tag == TPM2_ST_NO_SESSIONS) {
 111        *tpm_version = TPM_VERSION_2_0;
 112        return 0;
 113    }
 114
 115    /* Send TPM 1.2 command */
 116    ret = tpm_util_test(tpm_fd, (unsigned char *)&test_req,
 117                        sizeof(test_req), &return_tag);
 118    if (!ret && return_tag == TPM_TAG_RSP_COMMAND) {
 119        *tpm_version = TPM_VERSION_1_2;
 120        /* this is a TPM 1.2 */
 121        return 0;
 122    }
 123
 124    *tpm_version = TPM_VERSION_UNSPEC;
 125
 126    return 1;
 127}
 128