Re: [Qemu-devel] [PATCH V8 14/14] Allow to provide inital TPM state

[Michael S. Tsirkin]

On Wed, Aug 31, 2011 at 10:36:05AM -0400, Stefan Berger wrote:
> This patch adds a -tpm ...,initstate=...,... command line option to the
> TPM's existing options and enables the TPM to be initialized with an
> existing state blob. This in turn allows us to simulate TPM manufacturing
> and equip the TPM with an endorsement key, certificates and initialize its
> NVRAM areas etc.. This step is typically done during manufacturng of the TPM
> and/or the (physical) machine.
> 
> The initial state can be passed either as file or via a file descriptor. The
> encoding of the state can either be binary or in form of a base64-encoded
> blob surrounded by tags indicating the start and end.
> 
> The intial state can be produced through a yet-to-be-published tpm-authoring
> tool.
> 
> Signed-off-by: Stefan Berger <address@hidden>

I am guessing we get the base64 format from tpmlib?

> ---
>  hw/tpm_builtin.c |  123 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  qemu-config.c    |   12 +++++
>  qemu-options.hx  |   40 ++++++++++++++++-
>  3 files changed, 172 insertions(+), 3 deletions(-)
> 
> Index: qemu-git/hw/tpm_builtin.c
> ===================================================================
> --- qemu-git.orig/hw/tpm_builtin.c
> +++ qemu-git/hw/tpm_builtin.c
> @@ -170,9 +170,16 @@ static struct enckey {
>      AES_KEY tpm_dec_key;
>  } enckey;
>  
> +static int tpm_initstatefd = -1;
> +static bool tpm_initstate_bin;
> +

This hardcodes assumption of a single backend.

>  static int tpm_builtin_load_sized_data_from_bs(BlockDriverState *bs,
>                                                 enum BSEntryType be,
>                                                 TPMSizedBuffer *tsb);
> +static TPM_RESULT tpm_builtin_get_initial_state(unsigned char **data,
> +                                                uint32_t *length,
> +                                                size_t tpm_number,
> +                                                const char *name);
>  
>  
>  
> @@ -1269,7 +1276,7 @@ static TPM_RESULT tpm_builtin_nvram_load
>          *length = permanent_state.size;
>  
>          if (*length == 0) {
> -            rc = TPM_RETRY;
> +            rc = tpm_builtin_get_initial_state(data, length, tpm_number, 
> name);
>          } else {
>              /* keep a copy of the last permanent state */
>              rc = TPM_Malloc(data, *length);
> @@ -1452,6 +1459,94 @@ static TPM_RESULT tpm_builtin_io_getphys
>  }
>  
>  
> +static TPM_RESULT tpm_builtin_get_initial_state(unsigned char **data,
> +                                                uint32_t *length,
> +                                                size_t tpm_number,
> +                                                const char *name)
> +{
> +    TPM_RESULT rc = TPM_RETRY;
> +    uint32_t allocated = 0;
> +    int len, flags;
> +    unsigned char buf[1024];
> +    unsigned char *result = NULL;
> +    size_t result_len;
> +
> +    if (tpm_initstatefd >= 0) {
> +        *data = NULL;
> +        *length = 0;
> +
> +        flags = fcntl(tpm_initstatefd, F_GETFL);
> +        if (flags < 0 ||
> +            fcntl(tpm_initstatefd, F_SETFL, flags & ~O_NONBLOCK) < 0) {
> +            return TPM_FAIL;
> +        }
> +
> +        while (TRUE) {
> +            len = read(tpm_initstatefd, buf, sizeof(buf));
> +
> +            if (len > 0) {
> +                if (len > allocated - *length) {
> +                    allocated = *length + len + 1024;
> +                    if (TPM_Realloc(data, allocated) != TPM_SUCCESS) {
> +                        goto err_exit;
> +                    }
> +                }
> +                memcpy(&(*data)[*length], buf, len);
> +                *length += len;
> +                (*data)[*length] = 0;
> +            } else if (len == 0) {
> +                rc = TPM_SUCCESS;
> +                break;
> +            } else if (len < 0) {
> +                if (errno == EINTR) {
> +                    continue;
> +                }
> +                goto err_exit;
> +            }
> +        }
> +
> +        if (*data == NULL) {
> +            /* nothing read */
> +            rc = TPM_FAIL;
> +            goto err_exit;
> +        }
> +
> +        if (!tpm_initstate_bin) {
> +            if (TPMLIB_DecodeBlob((char *)*data, TPMLIB_BLOB_TYPE_INITSTATE,
> +                                  &result, &result_len) != TPM_SUCCESS) {
> +                goto err_exit;
> +            }
> +            TPM_Free(*data);
> +            *data = result;
> +            *length = result_len;
> +            result = NULL;
> +        }
> +        /* sanity check for the size of the blob */
> +        if (*length > tpmlib_get_prop(TPMPROP_TPM_MAX_NV_SPACE)) {
> +            goto err_exit;
> +        }

Do we really have to hand-craft file reading?
How large is TPMPROP_TPM_MAX_NV_SPACE?
If not too large, we can just allocate that
and do a single fread call?

Or, we rely on glib now - can we use 
g_io_channel_read_to_end () or something like that?



> +        /* have it written into the BlockStorage */
> +        rc = tpm_builtin_nvram_storedata(*data, *length, tpm_number, name);

What if that backend is compiled-out?
link will fail?

> +        if (rc != TPM_SUCCESS) {
> +            goto err_exit;
> +        }
> +    }
> +
> +norm_exit:
> +    close(tpm_initstatefd);
> +    tpm_initstatefd = -1;
> +
> +    return rc;
> +
> +err_exit:
> +    TPM_Free(*data);
> +    *data = NULL;
> +    *length = 0;
> +    TPM_Free(result);
> +
> +    goto norm_exit;
> +}
> +
>  /*****************************************************************/
>  
>  
> @@ -1748,6 +1843,7 @@ static TPMBackend *tpm_builtin_create(Qe
>      const char *value;
>      unsigned char keyvalue[256/8];
>      int keysize = sizeof(keyvalue);
> +    unsigned int offset;
>  
>      driver = g_malloc(sizeof(TPMBackend));
>      if (!driver) {
> @@ -1801,6 +1897,28 @@ static TPMBackend *tpm_builtin_create(Qe
>          enckey.enctype = BS_DIR_ENCTYPE_NONE;
>      }
>  
> +    value = qemu_opt_get(opts, "initstate");
> +    if (value) {
> +        offset = 0;
> +
> +        if (!strncmp(value, "bin:", 4)) {
> +            tpm_initstate_bin = true;
> +            offset = 4;
> +        } else if (!strncmp(value, "base64:", 7)) {
> +            tpm_initstate_bin = false;
> +            offset = 7;
> +        }
> +
> +        if (sscanf(&value[offset], "fd:%d", &tpm_initstatefd) != 1) {
> +            tpm_initstatefd = open(&value[offset], O_RDONLY);
> +            if (tpm_initstatefd < 0) {
> +                fprintf(stderr, "tpm: could not open file '%s' for 
> reading.\n",
> +                        value);
> +                goto err_exit;
> +            }
> +        }
> +    }
> +

Separate options for fd and for file mode would be better.

>      return driver;
>  
>  err_exit:
> @@ -1816,6 +1934,9 @@ static void tpm_builtin_destroy(TPMBacke
>      g_free(driver->id);
>      g_free(driver->model);
>      g_free(driver);
> +
> +    close(tpm_initstatefd);
> +    tpm_initstatefd = -1;
>  }
>  
>  
> Index: qemu-git/qemu-config.c
> ===================================================================
> --- qemu-git.orig/qemu-config.c
> +++ qemu-git/qemu-config.c
> @@ -527,6 +527,12 @@ static QemuOptsList qemu_tpmdev_opts = {
>              .type = QEMU_OPT_STRING,
>              .help = "Data encryption key",
>          },
> +        {
> +            .name = "initstate",
> +            .type = QEMU_OPT_STRING,
> +            .help = "File or file descriptor for reading initial TPM state "
> +                    "from",
> +        },
>          { /* end of list */ }
>      },
>  };
> @@ -556,6 +562,12 @@ static QemuOptsList qemu_tpm_opts = {
>              .type = QEMU_OPT_STRING,
>              .help = "Data encryption key",
>          },
> +        {
> +            .name = "initstate",
> +            .type = QEMU_OPT_STRING,
> +            .help = "File or file descriptor for reading initial TPM state "
> +                    "from",
> +        },
>          { /* end of list */ }
>      },
>  };

I think description should document the magic bin:/base64: etc strings,
or better get rid of them.

> Index: qemu-git/qemu-options.hx
> ===================================================================
> --- qemu-git.orig/qemu-options.hx
> +++ qemu-git/qemu-options.hx
> @@ -1767,8 +1767,10 @@ DEFHEADING(TPM device options:)
>  DEF("tpm", HAS_ARG, QEMU_OPTION_tpm, \
>      "" \
>      "-tpm builtin,path=<path>[,model=<model>][,key=<aes key>]\n" \
> +    "     [,initstate=[bin:|base64:]fd:<fd>|<path>]\n" \
>      "                enable a builtin TPM with state in file in path\n" \
>      "                and encrypt the TPM's state with the given AES key\n" \
> +    "                initstate= path to initial state of TPM; default is 
> base64\n" \
>      "-tpm null       enable a TPM null driver that responds with a fault\n" \
>      "                message to every TPM request\n" \
>      "-tpm model=?    to list available TPM device models\n" \
> @@ -1800,7 +1802,7 @@ Use ? to print all available TPM backend
>  qemu -tpmdev ?
>  @end example
>  
> address@hidden -tpmdev builtin ,address@hidden, address@hidden 
> [,address@hidden
> address@hidden -tpmdev builtin ,address@hidden, address@hidden 
> [,address@hidden [,address@hidden
>  
>  Creates an instance of the built-in TPM.
>  
> @@ -1830,6 +1832,40 @@ using AES-CBC encryption scheme supply t
>  -tpmdev 
> builtin,id=tpm0,path=<path_to_qcow2>,key=aes-cbc:0x1234567890abcdef01234567890abcdef
>  -device tpm-tis,tpmdev=tpm0
>  @end example
>  
> address@hidden specifies the path to a file containing the initial
> +state of the TPM. It can be used to provide the TPM with an EK and 
> certificates
> +for the EK, TPM and Platform. Since the file contains binary data that
> +have to conform to the TPM's layout of data, it must have been created using
> +an approriate authoring tool.
> +
> +The initstate option allows to provide a binary state blob or one that is
> +encode in base 64. The base64-encode state blob must have the format
> +
> address@hidden
> +-----BEGIN INITSTATE-----
> +<base 64 encoded state>
> +-----END INITSTATE-----
> address@hidden example
> +
> +The initstate option is only effective when Qemu is started with blank
> +state.
> +
> +The initstate option supports several formats:
> +
> address@hidden @option
> + @item  [base64:]<path_to_blob>
> + Provide the path to the TPM's initial state blob in base64 format.
> + @item  bin:<path to blob>
> + Provide the path to the TPM's initial state blob in binary format.
> + @item  [base64:]fd:<fd>
> + Provide the base64 formatted initial state via a file descriptor to read 
> from.
> + @item  bin:fd:<fd>
> + Provide the binary initial state via a file descriptor to read from.

The command line is non standard.  E.g. what if the path starts with fd?

> address@hidden table
> +
> address@hidden is optional.
> +
> +
>  @item -tpmdev null
>  
>  Creates an instance of a TPM null driver that responds to every command
> @@ -1840,7 +1876,7 @@ with a fault message.
>  The short form of a TPM device option is:
>  @table @option
>  
> address@hidden -tpm @var{backend-type}, address@hidden [,address@hidden 
> [,address@hidden
> address@hidden -tpm @var{backend-type}, address@hidden [,address@hidden 
> [,address@hidden [,address@hidden
>  @findex -tpm
>  
>  @option{model} specifies the device model. The default device model is a
>