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#include "exec/memory.h"
  26
  27/*
  28 * Write an error message in the given output buffer.
  29 */
  30void tpm_util_write_fatal_error_response(uint8_t *out, uint32_t out_len)
  31{
  32    if (out_len >= sizeof(struct tpm_resp_hdr)) {
  33        struct tpm_resp_hdr *resp = (struct tpm_resp_hdr *)out;
  34
  35        resp->tag = cpu_to_be16(TPM_TAG_RSP_COMMAND);
  36        resp->len = cpu_to_be32(sizeof(struct tpm_resp_hdr));
  37        resp->errcode = cpu_to_be32(TPM_FAIL);
  38    }
  39}
  40
  41bool tpm_util_is_selftest(const uint8_t *in, uint32_t in_len)
  42{
  43    struct tpm_req_hdr *hdr = (struct tpm_req_hdr *)in;
  44
  45    if (in_len >= sizeof(*hdr)) {
  46        return (be32_to_cpu(hdr->ordinal) == TPM_ORD_ContinueSelfTest);
  47    }
  48
  49    return false;
  50}
  51
  52/*
  53 * A basic test of a TPM device. We expect a well formatted response header
  54 * (error response is fine) within one second.
  55 */
  56static int tpm_util_test(int fd,
  57                         unsigned char *request,
  58                         size_t requestlen,
  59                         uint16_t *return_tag)
  60{
  61    struct tpm_resp_hdr *resp;
  62    fd_set readfds;
  63    int n;
  64    struct timeval tv = {
  65        .tv_sec = 1,
  66        .tv_usec = 0,
  67    };
  68    unsigned char buf[1024];
  69
  70    n = write(fd, request, requestlen);
  71    if (n < 0) {
  72        return -errno;
  73    }
  74    if (n != requestlen) {
  75        return -EFAULT;
  76    }
  77
  78    FD_ZERO(&readfds);
  79    FD_SET(fd, &readfds);
  80
  81    /* wait for a second */
  82    n = select(fd + 1, &readfds, NULL, NULL, &tv);
  83    if (n != 1) {
  84        return -errno;
  85    }
  86
  87    n = read(fd, &buf, sizeof(buf));
  88    if (n < sizeof(struct tpm_resp_hdr)) {
  89        return -EFAULT;
  90    }
  91
  92    resp = (struct tpm_resp_hdr *)buf;
  93    /* check the header */
  94    if (be32_to_cpu(resp->len) != n) {
  95        return -EMSGSIZE;
  96    }
  97
  98    *return_tag = be16_to_cpu(resp->tag);
  99
 100    return 0;
 101}
 102
 103/*
 104 * Probe for the TPM device in the back
 105 * Returns 0 on success with the version of the probed TPM set, 1 on failure.
 106 */
 107int tpm_util_test_tpmdev(int tpm_fd, TPMVersion *tpm_version)
 108{
 109    /*
 110     * Sending a TPM1.2 command to a TPM2 should return a TPM1.2
 111     * header (tag = 0xc4) and error code (TPM_BADTAG = 0x1e)
 112     *
 113     * Sending a TPM2 command to a TPM 2 will give a TPM 2 tag in the
 114     * header.
 115     * Sending a TPM2 command to a TPM 1.2 will give a TPM 1.2 tag
 116     * in the header and an error code.
 117     */
 118    const struct tpm_req_hdr test_req = {
 119        .tag = cpu_to_be16(TPM_TAG_RQU_COMMAND),
 120        .len = cpu_to_be32(sizeof(test_req)),
 121        .ordinal = cpu_to_be32(TPM_ORD_GetTicks),
 122    };
 123
 124    const struct tpm_req_hdr test_req_tpm2 = {
 125        .tag = cpu_to_be16(TPM2_ST_NO_SESSIONS),
 126        .len = cpu_to_be32(sizeof(test_req_tpm2)),
 127        .ordinal = cpu_to_be32(TPM2_CC_ReadClock),
 128    };
 129    uint16_t return_tag;
 130    int ret;
 131
 132    /* Send TPM 2 command */
 133    ret = tpm_util_test(tpm_fd, (unsigned char *)&test_req_tpm2,
 134                        sizeof(test_req_tpm2), &return_tag);
 135    /* TPM 2 would respond with a tag of TPM2_ST_NO_SESSIONS */
 136    if (!ret && return_tag == TPM2_ST_NO_SESSIONS) {
 137        *tpm_version = TPM_VERSION_2_0;
 138        return 0;
 139    }
 140
 141    /* Send TPM 1.2 command */
 142    ret = tpm_util_test(tpm_fd, (unsigned char *)&test_req,
 143                        sizeof(test_req), &return_tag);
 144    if (!ret && return_tag == TPM_TAG_RSP_COMMAND) {
 145        *tpm_version = TPM_VERSION_1_2;
 146        /* this is a TPM 1.2 */
 147        return 0;
 148    }
 149
 150    *tpm_version = TPM_VERSION_UNSPEC;
 151
 152    return 1;
 153}
 154