[SeaBIOS] [PATCH 3/3] tpm: Support 2.0 TPM devices connected to a TIS host
Stefan Berger
stefanb at linux.vnet.ibm.com
Tue Feb 27 00:02:49 CET 2018
On 02/26/2018 05:44 PM, Stephen Douthit wrote:
> On 02/26/2018 05:09 PM, Stefan Berger wrote:
>> On 02/26/2018 03:37 PM, Stephen Douthit wrote:
>>> tis_get_tpm_version() was returning the interface version, which is
>>> always
>>> 1.2 since tis_probe() would have failed if the interface wasn't TIS.
>>>
>>> New version check is based on the tpm2_probe() function from the Linux
>>> tpm_tis driver.
>>>
>>> Signed-off-by: Stephen Douthit <stephend at silicom-usa.com>
>>> Tested-by: Stephen Douthit <stephend at silicom-usa.com>
>>> ---
>>> src/hw/tpm_drivers.c | 21 +++++++++++++++------
>>> src/std/tcg.h | 1 +
>>> src/tcgbios.c | 2 +-
>>> src/tcgbios.h | 4 ++++
>>> 4 files changed, 21 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/src/hw/tpm_drivers.c b/src/hw/tpm_drivers.c
>>> index 789d70a..32c34df 100644
>>> --- a/src/hw/tpm_drivers.c
>>> +++ b/src/hw/tpm_drivers.c
>>> @@ -11,6 +11,7 @@
>>> #include "config.h" // CONFIG_TPM_TIS_SHA1THRESHOLD
>>> #include "hw/tpm_drivers.h" // struct tpm_driver
>>> #include "std/tcg.h" // TCG_RESPONSE_TIMEOUT
>>> +#include "tcgbios.h" // tpm20_getcapability
>>> #include "output.h" // warn_timeout
>>> #include "stacks.h" // yield
>>> #include "string.h" // memcpy
>>> @@ -119,7 +120,7 @@ static u32 tis_probe(void)
>>> if ((didvid != 0) && (didvid != 0xffffffff))
>>> rc = 1;
>>>
>>> - /* TPM 2 has an interface register */
>>> + /* Low 32 bits of CRB interface register overlap TIS interface
>>> register */
>>> u32 ifaceid = readl(TIS_REG(0, TIS_REG_IFACE_ID));
>>
>> Since this is tis_probe, I don't think we need to mention the CRB
>> here ...
>
> I think that was a note to myself I forgot to strip out when I
> dropped my debug prints. I'll change the comment back.
>
>>>
>>> if ((ifaceid & 0xf) != 0xf) {
>>> @@ -142,13 +143,21 @@ static u32 tis_probe(void)
>>>
>>> static TPMVersion tis_get_tpm_version(void)
>>> {
>>> - /* TPM 2 has an interface register */
>>> - u32 ifaceid = readl(TIS_REG(0, TIS_REG_IFACE_ID));
>>> + u8 buffer[128];
>>> + int ret;
>>> + struct tpm2_res_getcapability *trg =
>>> + (struct tpm2_res_getcapability *)&buffer;
>>> +
>>> + ret = tpm20_getcapability(TPM2_CAP_TPM_PROPERTIES,
>>> cpu_to_be32(0x100),
>>> + cpu_to_be32(1), &trg->hdr,
>>> sizeof(buffer));
>>> + if (ret == TPM2_RC_INITIALIZE)
>>> + return TPM_VERSION_2;
>>> + else if (ret)
>>> + return TPM_VERSION_NONE;
>> I haven't tried yet, but likely this will not work for TPM 1.2 since
>> it will also return an error.
>
> Doh. That makes sense. I'll need to find a 1.2 system to test on to
> avoid stupid mistakes like that.
>
>> Wouldn't the check for the tag below not be sufficient? We are doing
>> something similar in QEMU when probing for the TPM. Here we send TPM
>> 2 command TPM_CC_ReadClock and check the tag for TPM 2 type and then
>> TPM 1.2 command TPM_ORD_GetTicks and check for TPM 1.2 tag.
>
> It might be, it wasn't clear to me if the tag could be trusted if the
> return code wasn't success. The Linux tpm2_probe() code bails before
> the tag comparison if tpm_transmit_cmd() returns an error.
>
> Is there a block of QEMU code you would recommend as a reference for
> probing TPMs? I'm not very familiar with that code base, and a
> pointer would be handy.
https://github.com/stefanberger/qemu-tpm/blob/v2.4.1%2Btpm/hw/tpm/tpm_util.c#L94
What I don't like about the sending of commands is that we're breaking
the layer here. We basically cannot send commands using this higher
level API. The lowest we could go would be to call tpmhw_transmit, but
that function cannot be used as it is but has to be split up to take
tpm_driver as a parameter. You would pass to it
&tpm_drivers[TIS_DRIVER_INDEX].
As far as I know, TPM 1.2 didn't have that register, so they either
return static 0 or 0xffffffff in that register.
Though if reading the flags from the interface register really turns out
to be insufficient, I think you should try to send a command like
TPM2_CC_ReadClock. If you get back a TPM2_ST_NO_SESSION, it's a TPM 2.
If you get a TPM_TAG_RSP_COMMAND it's a TPM 12.
>
>> Do you know what value does the InterfaceType show on your TIS? I
>> only tested this with QEMU TIS and here we return 0x0 in those 4
>> bits, which means, following specs, 'FIFO interface as defined in PTP
>> for TPM 2.0 is active'.
>
> I don't see it in my notes, I can put some debug prints back in
> tomorrow and will get back to you.
>
> Thanks,
> Steve
>
>>>
>>> - if ((ifaceid & 0xf) == 0) {
>>> - /* TPM 2 */
>>> + if (cpu_to_be32(trg->hdr.tag) == TPM2_ST_NO_SESSIONS)
>>> return TPM_VERSION_2;
>>> - }
>>> +
>>> return TPM_VERSION_1_2;
>>> }
>>>
>>> diff --git a/src/std/tcg.h b/src/std/tcg.h
>>> index 09a92d8..4c07493 100644
>>> --- a/src/std/tcg.h
>>> +++ b/src/std/tcg.h
>>> @@ -357,6 +357,7 @@ struct tpm_res_sha1complete {
>>>
>>> /* TPM 2 Capabilities */
>>> #define TPM2_CAP_PCRS 0x00000005
>>> +#define TPM2_CAP_TPM_PROPERTIES 0x00000006
>>>
>>> /* TPM 2 data structures */
>>>
>>> diff --git a/src/tcgbios.c b/src/tcgbios.c
>>> index 40b3028..b86bf64 100644
>>> --- a/src/tcgbios.c
>>> +++ b/src/tcgbios.c
>>> @@ -381,7 +381,7 @@ tpm_simple_cmd(u8 locty, u32 ordinal
>>> return ret;
>>> }
>>>
>>> -static int
>>> +int
>>> tpm20_getcapability(u32 capability, u32 property, u32 count,
>>> struct tpm_rsp_header *rsp, u32 rsize)
>>> {
>>> diff --git a/src/tcgbios.h b/src/tcgbios.h
>>> index 32fb941..9fc711a 100644
>>> --- a/src/tcgbios.h
>>> +++ b/src/tcgbios.h
>>> @@ -1,6 +1,7 @@
>>> #ifndef TCGBIOS_H
>>> #define TCGBIOS_H
>>>
>>> +#include "std/tcg.h" // struct tpm_rsp_header
>>> #include "types.h"
>>>
>>> struct bregs;
>>> @@ -15,5 +16,8 @@ void tpm_add_cdrom_catalog(const u8 *addr, u32
>>> length);
>>> void tpm_option_rom(const void *addr, u32 len);
>>> int tpm_can_show_menu(void);
>>> void tpm_menu(void);
>>> +int
>>> +tpm20_getcapability(u32 capability, u32 property, u32 count,
>>> + struct tpm_rsp_header *rsp, u32 rsize);
>>>
>>> #endif /* TCGBIOS_H */
>>
>>
>
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