hw/tpm/tpm_util.c

   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  */
  30 void 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
  41 bool 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  */
  56 static 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  */
 107 int 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 }