qemu/hw/tpm/tpm_util.c

/*
 * 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 "qemu/osdep.h"
#include "qemu/error-report.h"
#include "tpm_util.h"
#include "tpm_int.h"
#include "exec/memory.h"

#define DEBUG_TPM 0

#define DPRINTF(fmt, ...) do { \
    if (DEBUG_TPM) { \
        fprintf(stderr, "tpm-util:"fmt"\n", ## __VA_ARGS__); \
    } \
} while (0)

/*
 * Write an error message in the given output buffer.
 */
void tpm_util_write_fatal_error_response(uint8_t *out, uint32_t out_len)
{
    if (out_len >= sizeof(struct tpm_resp_hdr)) {
        struct tpm_resp_hdr *resp = (struct tpm_resp_hdr *)out;

        resp->tag = cpu_to_be16(TPM_TAG_RSP_COMMAND);
        resp->len = cpu_to_be32(sizeof(struct tpm_resp_hdr));
        resp->errcode = cpu_to_be32(TPM_FAIL);
    }
}

bool tpm_util_is_selftest(const uint8_t *in, uint32_t in_len)
{
    struct tpm_req_hdr *hdr = (struct tpm_req_hdr *)in;

    if (in_len >= sizeof(*hdr)) {
        return (be32_to_cpu(hdr->ordinal) == TPM_ORD_ContinueSelfTest);
    }

    return false;
}

/*
 * Send request to a TPM device. We expect a response within one second.
 */
static int tpm_util_request(int fd,
                            unsigned char *request,
                            size_t requestlen,
                            unsigned char *response,
                            size_t responselen)
{
    struct tpm_resp_hdr *resp;
    fd_set readfds;
    int n;
    struct timeval tv = {
        .tv_sec = 1,
        .tv_usec = 0,
    };

    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, response, responselen);
    if (n < sizeof(struct tpm_resp_hdr)) {
        return -EFAULT;
    }

    resp = (struct tpm_resp_hdr *)response;
    /* check the header */
    if (be32_to_cpu(resp->len) != n) {
        return -EMSGSIZE;
    }

    return 0;
}

/*
 * A basic test of a TPM device. We expect a well formatted response header
 * (error response is fine).
 */
static int tpm_util_test(int fd,
                         unsigned char *request,
                         size_t requestlen,
                         uint16_t *return_tag)
{
    struct tpm_resp_hdr *resp;
    unsigned char buf[1024];
    ssize_t ret;

    ret = tpm_util_request(fd, request, requestlen,
                           buf, sizeof(buf));
    if (ret < 0) {
        return ret;
    }

    resp = (struct tpm_resp_hdr *)buf;
    *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;
}

int tpm_util_get_buffer_size(int tpm_fd, TPMVersion tpm_version,
                             size_t *buffersize)
{
    unsigned char buf[1024];
    int ret;

    switch (tpm_version) {
    case TPM_VERSION_1_2: {
        const struct tpm_req_get_buffer_size {
            struct tpm_req_hdr hdr;
            uint32_t capability;
            uint32_t len;
            uint32_t subcap;
        } QEMU_PACKED tpm_get_buffer_size = {
            .hdr = {
                .tag = cpu_to_be16(TPM_TAG_RQU_COMMAND),
                .len = cpu_to_be32(sizeof(tpm_get_buffer_size)),
                .ordinal = cpu_to_be32(TPM_ORD_GetCapability),
            },
            .capability = cpu_to_be32(TPM_CAP_PROPERTY),
            .len = cpu_to_be32(sizeof(uint32_t)),
            .subcap = cpu_to_be32(TPM_CAP_PROP_INPUT_BUFFER),
        };
        struct tpm_resp_get_buffer_size {
            struct tpm_resp_hdr hdr;
            uint32_t len;
            uint32_t buffersize;
        } QEMU_PACKED *tpm_resp = (struct tpm_resp_get_buffer_size *)buf;

        ret = tpm_util_request(tpm_fd, (unsigned char *)&tpm_get_buffer_size,
                               sizeof(tpm_get_buffer_size), buf, sizeof(buf));
        if (ret < 0) {
            return ret;
        }

        if (be32_to_cpu(tpm_resp->hdr.len) != sizeof(*tpm_resp) ||
            be32_to_cpu(tpm_resp->len) != sizeof(uint32_t)) {
            DPRINTF("tpm_resp->hdr.len = %u, expected = %zu\n",
                    be32_to_cpu(tpm_resp->hdr.len), sizeof(*tpm_resp));
            DPRINTF("tpm_resp->len = %u, expected = %zu\n",
                    be32_to_cpu(tpm_resp->len), sizeof(uint32_t));
            error_report("tpm_util: Got unexpected response to "
                         "TPM_GetCapability; errcode: 0x%x",
                         be32_to_cpu(tpm_resp->hdr.errcode));
            return -EFAULT;
        }
        *buffersize = be32_to_cpu(tpm_resp->buffersize);
        break;
    }
    case TPM_VERSION_2_0: {
        const struct tpm2_req_get_buffer_size {
            struct tpm_req_hdr hdr;
            uint32_t capability;
            uint32_t property;
            uint32_t count;
        } QEMU_PACKED tpm2_get_buffer_size = {
            .hdr = {
                .tag = cpu_to_be16(TPM2_ST_NO_SESSIONS),
                .len = cpu_to_be32(sizeof(tpm2_get_buffer_size)),
                .ordinal = cpu_to_be32(TPM2_CC_GetCapability),
            },
            .capability = cpu_to_be32(TPM2_CAP_TPM_PROPERTIES),
            .property = cpu_to_be32(TPM2_PT_MAX_COMMAND_SIZE),
            .count = cpu_to_be32(2), /* also get TPM2_PT_MAX_RESPONSE_SIZE */
        };
        struct tpm2_resp_get_buffer_size {
            struct tpm_resp_hdr hdr;
            uint8_t more;
            uint32_t capability;
            uint32_t count;
            uint32_t property1;
            uint32_t value1;
            uint32_t property2;
            uint32_t value2;
        } QEMU_PACKED *tpm2_resp = (struct tpm2_resp_get_buffer_size *)buf;

        ret = tpm_util_request(tpm_fd, (unsigned char *)&tpm2_get_buffer_size,
                               sizeof(tpm2_get_buffer_size), buf, sizeof(buf));
        if (ret < 0) {
            return ret;
        }

        if (be32_to_cpu(tpm2_resp->hdr.len) != sizeof(*tpm2_resp) ||
            be32_to_cpu(tpm2_resp->count) != 2) {
            DPRINTF("tpm2_resp->hdr.len = %u, expected = %zu\n",
                    be32_to_cpu(tpm2_resp->hdr.len), sizeof(*tpm2_resp));
            DPRINTF("tpm2_resp->len = %u, expected = %u\n",
                    be32_to_cpu(tpm2_resp->count), 2);
            error_report("tpm_util: Got unexpected response to "
                         "TPM2_GetCapability; errcode: 0x%x",
                         be32_to_cpu(tpm2_resp->hdr.errcode));
            return -EFAULT;
        }
        *buffersize = MAX(be32_to_cpu(tpm2_resp->value1),
                          be32_to_cpu(tpm2_resp->value2));
        break;
    }
    case TPM_VERSION_UNSPEC:
        return -EFAULT;
    }

    DPRINTF("buffersize of device: %zu\n", *buffersize);

    return 0;
}