[SLOF] [PATCH 07/16] Perform some initial measurements

[Nikunj A Dadhania]

Stefan Berger <stefanb at linux.vnet.ibm.com> writes:

> On 11/09/2015 04:22 AM, Nikunj A Dadhania wrote:
>> Stefan Berger <stefanb at linux.vnet.ibm.com> writes:
>> +/*
>> + * Add event separators for PCRs 0 to 7
>> + */
>> +uint32_t tpm_add_event_separators(void)
>> +{
>> +	uint32_t rc;
>> +	uint32_t pcrindex = 0;
>> +
>> +	if (!has_working_tpm())
>> +		return TCGBIOS_GENERAL_ERROR;
>> +
>> +	while (pcrindex <= 7) {
>> +		rc = tpm_add_measurement(pcrindex, EV_SEPARATOR, NULL);
>> +		if (rc)
>> +			break;
>> +		pcrindex ++;
>> +	}
>> +
>> +	return rc;
>> +}
>> +
>> +/*
>> + * Add a measurement regarding the boot device (CDRom, Floppy, HDD) to
>> + * the list of measurements.
>> Is network boot device supported ?
>
> It may be. I don't have a setup to test it.

This would help:

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Installation_Guide/chap-installation-server-setup.html#sect-network-boot-setup-ppc-grub2


>>> +	default:
>>> +		/*
>>> +		 * equivalent to:
>>> +		 * dd if=/dev/hda ibs=1 count=440 | sha1sum
>>> +		 */
>>> +		string = "MBR";
>>> +		rc = tpm_add_measurement_to_log(4, EV_IPL,
>>> +						string, strlen(string),
>>> +						addr, 0x1b8);
>>> +
>>> +		if (rc)
>>> +			break;
>>> +
>>> +		/*
>>> +		 * equivalent to:
>>> +		 * dd if=/dev/hda ibs=1 count=72 skip=440 | sha1sum
>>> +		 */
>>> +		string = "MBR PARTITION TABLE";
>>> +		rc = tpm_add_measurement_to_log(5, EV_IPL_PARTITION_DATA,
>>> +						string, strlen(string),
>>> +						addr + 0x1b8, 0x48);
>>> +	}
>> We also support GPT, dont we need support for that ?
>> Most of the distros are moving to GPT.
>
> If I remember correctly, Fedora 22 still uses MBR. Again, I would need a 
> setup to test this. Not sure what specs say about what to measure in 
> that case.

AFAIK, Ubuntu defaults to GPT.

>
>
>>
>>> +
>>> +	return rc;
>>> +}
>>> +
>>> +uint32_t tpm_add_bcv(uint32_t bootdrv, const uint8_t *addr, uint32_t
>>> length)
>> tpm_add_bcv: what does bcv mean ?
>
> Boot connection vector. I will remove this function.

I thought you were using this function?

>
>>
>>> +{
>>> +	uint32_t rc;
>>> +
>>> +	if (!has_working_tpm())
>>> +		return TCGBIOS_GENERAL_ERROR;
>>> +
>>> +	rc = tpm_add_bootdevice(0, bootdrv);
>>> +	if (rc)
>>> +		return rc;
>>> +
>>> +	return tpm_ipl(IPL_BCV, addr, length);
>>> +}
>>> diff --git a/lib/libtpm/tcgbios.h b/lib/libtpm/tcgbios.h
>>> index b217dd1..9b43ce3 100644
>>> --- a/lib/libtpm/tcgbios.h
>>> +++ b/lib/libtpm/tcgbios.h
>>> @@ -15,9 +15,18 @@
>>>
>>>   #include <stdint.h>
>>>
>>> +enum ipltype {
>>> +    IPL_BCV = 0,
>>> +    IPL_EL_TORITO_1,
>>> +    IPL_EL_TORITO_2
>>> +};
>>> +
>>>   uint32_t tpm_start(void);
>>>   uint32_t tpm_unassert_pp(void);
>>>   void tpm_set_log_parameters(void *address, unsigned int size);
>>>   uint32_t tpm_get_logsize(void);
>>> +uint32_t tpm_ipl(enum ipltype bootcd, const uint8_t *addr, uint32_t length);
>>> +uint32_t tpm_add_bcv(uint32_t bootdrv, const uint8_t *addr, uint32_t length);
>>> +uint32_t tpm_add_event_separators(void);
>>>
>>>   #endif /* TCGBIOS_H */
>>> diff --git a/lib/libtpm/tpm.code b/lib/libtpm/tpm.code
>>> index b868ca3..de90717 100644
>>> --- a/lib/libtpm/tpm.code
>>> +++ b/lib/libtpm/tpm.code
>>> @@ -56,3 +56,37 @@ PRIM(tpm_X2d_get_X2d_logsize)
>>>   	PUSH;
>>>   	TOS.n = tpm_get_logsize();
>>>   MIRP
>>> +
>>> +/************************************************/
>>> +/* Measure and log event separators             */
>>> +/* SLOF:   tpm-add-event-separators  ( -- )     */
>>> +/* LIBTPM: tpm_add_event_separators(void)       */
>>> +/************************************************/
>>> +PRIM(tpm_X2d_add_X2d_event_X2d_separators)
>>> +	PUSH;
>>> +	TOS.n = tpm_add_event_separators();
>>> +MIRP
>>> +
>>> +/************************************************/
>>> +/* Measure and log IPL                          */
>>> +/* SLOF:   tpm-ipl  ( ipltype addr length -- )  */
>> Does not return anything, missed in the comment?
>>
>> /* SLOF:   tpm-ipl  ( ipltype addr length --  return ) */
>>
>>> +/* LIBTPM: tpm_ipl(void)                        */
>>> +/************************************************/
>>> +PRIM(tpm_X2d_ipl)
>>> +	int length = TOS.u; POP;
>>> +	void *addr = TOS.a; POP;
>>> +	int bootcd = TOS.u;
>>> +	TOS.n = tpm_ipl(bootcd, addr, length);
>>> +MIRP
>>> +
>>> +/****************************************************/
>>> +/* Measure and log bcv IPL                          */
>>> +/* SLOF:   tpm-add-bcv  ( bootdrv addr length -- )  */
>> ditto, forgot return in comment ?
>>
>>> +/* LIBTPM: tpm_add_bcv(void)                        */
>>> +/****************************************************/
>>> +PRIM(tpm_X2d_add_X2d_bcv)
>>> +	int length = TOS.u; POP;
>>> +	void *addr = TOS.a; POP;
>>> +	int bootdrv = TOS.u;
>>> +	TOS.n = tpm_add_bcv(bootdrv, addr, length);
>>> +MIRP
>>> diff --git a/lib/libtpm/tpm.in b/lib/libtpm/tpm.in
>>> index 32d675f..06b0672 100644
>>> --- a/lib/libtpm/tpm.in
>>> +++ b/lib/libtpm/tpm.in
>>> @@ -17,3 +17,6 @@ cod(tpm-start)
>>>   cod(tpm-unassert-pp)
>>>   cod(tpm-set-log-parameters)
>>>   cod(tpm-get-logsize)
>>> +cod(tpm-add-event-separators)
>>> +cod(tpm-ipl)
>>> +cod(tpm-add-bcv)
>>> diff --git a/slof/fs/tpm/tpm-static.fs b/slof/fs/tpm/tpm-static.fs
>>> index 11e4ad5..d425693 100644
>>> --- a/slof/fs/tpm/tpm-static.fs
>>> +++ b/slof/fs/tpm/tpm-static.fs
>>> @@ -22,6 +22,17 @@ false VALUE vtpm-debug?
>>>       THEN
>>>   ;
>>>
>>> +: vtpm-add-event-separators
>>> +    vtpm-available? IF
>>> +        tpm-add-event-separators                  ( -- errcode )
>> Why do we ignore the error code?
>
>
> We can ignore the error on this level. In SeaBIOS we do the same and we 
> do not abort the boot. In case of an error we should probably write a 
> log entry that indicates an error, assuming that such a log entry has 
> been defined.

What I am unable to understand is if this feature is for Secure booting, and
we ignore the errors, how is it that vTPM will ensure secured
images/boot?

Regards,
Nikunj