Re: [SeaBIOS] [PATCH v2 2/3] tcgbios: Add TPM Physical Presence interface support

[Stefan Berger]

On 01/16/2018 01:36 PM, Kevin O'Connor wrote:
> On Tue, Jan 16, 2018 at 11:41:02AM -0500, Stefan Berger wrote:
> > Add support for TPM 1.2 and TPM 2 Physical Presence interface (PPI).
> > A shared memory structure is located at 0xfffe f000 - 0xfffe f3ff
> > that SeaBIOS initializes (unless it has already been intialized) and
> > then searches for a code it is supposed to act upon. A code typically
> > requires that one or more TPM commands are being sent.
>
> If I'm understanding the code correctly, it no longer hardcodes
> 0xfffef000 (great!).  The commit comment should also be updated.
> > The underlying spec can be accessed from this page here:
> >
> > https://trustedcomputinggroup.org/tcg-physical-presence-interface-specificat...
> >
> > Version 1.30 is implemented.
> > Signed-off-by: Stefan Berger
> >
> > src/post.c     |  4 +++
> >   src/std/acpi.h | 10 ++++++
> >   src/std/tcg.h  | 31 ++++++++++++++++++
> >   src/tcgbios.c  | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >   src/tcgbios.h  |  3 ++
> >   5 files changed, 147 insertions(+)
> >
> > diff --git a/src/post.c b/src/post.c
> > index f93106a..f451013 100644
> > --- a/src/post.c
> > +++ b/src/post.c
> > @@ -201,6 +201,7 @@ maininit(void)
> >   // Setup platform devices.
> >   platform_hardware_setup();
> >
> > tpm_ppi_init();
> >
> > // Start hardware initialization (if threads allowed during optionroms)
> >  if (threads_during_optionroms())
> >
> > @@ -220,6 +221,9 @@ maininit(void)
> >       // Run option roms
> >       optionrom_setup();
> > // Process user-requested TPM state change
> > tpm_ppi_process();
>
> I think it would be better if these two calls were added to the
> existing tpm_setup() call.

Done.
> Also, function suffixes of "_init" and "_setup" have specific meaning
> in seabios - see docs/Execution_and_code_flow.md - so you should not
> export a function with those sufixes unless they follow the
> convention.
>
> [...]
> > --- a/src/std/acpi.h
> > +++ b/src/std/acpi.h
> > @@ -320,4 +320,14 @@ struct tpm2_descriptor_rev2
> >       u64  log_area_start_address;
> >   } PACKED;
> >
> > +#define QEMU_SIGNATURE 0x554d4551
> > +struct qemu_descriptor
> > +{
> > ACPI_TABLE_HEADER_DEF
> > u32 tpmppi_address;
> > u8 tpm_version; /* 1 = 1.2, 2 = 2 */
> > u8 tpmppi_version;
> >
> > +#define TPM_PPI_VERSION_1_30   1
> > +} PACKED;
>
> I'm confused at the purpose of this acpi table.  If I'm understanding
> it correctly, it is purely to pass information from QEMU to SeaBIOS
> (and perhaps OVMF?).  If so, I don't think this is a good way to do it
> a regular fw_cfg setting seems simpler (and less likely to cause
>
> problems with OSes).
> > #endif // acpi.h
> >
> > diff --git a/src/std/tcg.h b/src/std/tcg.h
> > index 09a92d8..22353a9 100644
> > --- a/src/std/tcg.h
> > +++ b/src/std/tcg.h
> > @@ -551,4 +551,35 @@ struct pcctes_romex
> >   #define TPM_PPI_OP_SET_OWNERINSTALL_TRUE 8
> >   #define TPM_PPI_OP_SET_OWNERINSTALL_FALSE 9
> >
> > +struct tpm_ppi {
> > u8 ppin;            /*  0: 1 = initialized */
> > u32 ppip;           /*  1: not used */
> > u32 pprp;           /*  5: response from TPM; set by BIOS */
> > u32 pprq;           /*  9: opcode; set by ACPI */
> > u32 pprm;           /* 13: parameter for opcode; set by ACPI */
> > u32 lppr;           /* 17: last opcode; set by BIOS */
> > u32 fret;           /* 21: not used */
> > u8 res1;            /* 25: reserved */
> > u32 res2[4];        /* 26: reserved */
> > u8 res3[214];       /* 42: reserved */
> > u8 func[256];       /* 256: per function implementation flags; set by BIOS */
> >
> > +/* indication whether function is implemented; bit 0 */
> > +#define TPM_PPI_FUNC_IMPLEMENTED       (1 << 0)
> > +/* actions OS should take to transition to the pre-OS env.; bits 1, 2 */
> > +#define TPM_PPI_FUNC_ACTION_SHUTDOWN   (1 << 1)
> > +#define TPM_PPI_FUNC_ACTION_REBOOT     (2 << 1)
> > +#define TPM_PPI_FUNC_ACTION_VENDOR     (3 << 1)
> > +#define TPM_PPI_FUNC_ACTION_MASK       (3 << 1)
> > +/* whether function is blocked by BIOS settings; bits 3,4,5 */
> > +#define TPM_PPI_FUNC_NOT_IMPLEMENTED     (0 << 3)
> > +#define TPM_PPI_FUNC_BIOS_ONLY           (1 << 3)
> > +#define TPM_PPI_FUNC_BLOCKED             (2 << 3)
> > +#define TPM_PPI_FUNC_ALLOWED_USR_REQ     (3 << 3)
> > +#define TPM_PPI_FUNC_ALLOWED_USR_NOT_REQ (4 << 3)
> > +#define TPM_PPI_FUNC_MASK                (7 << 3)
> > +} PACKED;
> >
> > +void tpm_ppi_init(void);
> > +void tpm_ppi_process(void);
>
> The files in the std/ directory are for well defined specifications.
> It should not be used to export seabios functions.  Also, it's not
> clear to me if 'struct tpm_ppi' and the TPM_PPI_FUNC_* defines are a
> qemu/acpi/seabios interface or a TPM standard.

Move the definition of tpm_ppi struct to tcgbios.c. It's shared between 
ACPI and firmware.
> > #endif // tcg.h
> >
> > diff --git a/src/tcgbios.c b/src/tcgbios.c
> > index 730b5e7..c8e6ca2 100644
> > --- a/src/tcgbios.c
> > +++ b/src/tcgbios.c
> > @@ -1783,6 +1783,18 @@ tpm20_process_cfg(tpm_ppi_code msgCode, int verbose, u32 *returnCode)
> >   }
> >
> > static int
> > +tpm_process_cfg(tpm_ppi_code msgCode, int verbose, u32 *returnCode)
> > +{
> > switch (TPM_version) {
> > case TPM_VERSION_1_2:
> >    return tpm12_process_cfg(msgCode, verbose, returnCode);
> > case TPM_VERSION_2:
> >    return tpm20_process_cfg(msgCode, verbose, returnCode);
> > }
> > return -1;
> >
> > +}
> >
> > +static int
> >   tpm12_get_tpm_state(void)
> >   {
> >       int state = 0;
> > @@ -2021,3 +2033,90 @@ tpm_can_show_menu(void)
> >       }
> >       return 0;
> >   }
> >
> > +static struct tpm_ppi *tp;
> > +static u8 nextStep = TPM_PPI_OP_NOOP; /* opcode to execute after reboot */
> >
> > +#define FLAGS (TPM_PPI_FUNC_IMPLEMENTED | \
> >           TPM_PPI_FUNC_ACTION_REBOOT | \
> >           TPM_PPI_FUNC_ALLOWED_USR_NOT_REQ)
> >
> > +static const u8 tpm12_ppi_funcs[] = {
> > [TPM_PPI_OP_NOOP] = TPM_PPI_FUNC_IMPLEMENTED |
> >                    TPM_PPI_FUNC_ALLOWED_USR_NOT_REQ,
> > [TPM_PPI_OP_ENABLE]  = FLAGS,
> > [TPM_PPI_OP_DISABLE] = FLAGS,
> > [TPM_PPI_OP_ACTIVATE] = FLAGS,
> > [TPM_PPI_OP_DEACTIVATE] = FLAGS,
> > [TPM_PPI_OP_CLEAR] = FLAGS,
> > [TPM_PPI_OP_SET_OWNERINSTALL_TRUE] = FLAGS,
> > [TPM_PPI_OP_SET_OWNERINSTALL_FALSE] = FLAGS,
> >
> > +};
> >
> > +static const u8 tpm2_ppi_funcs[] = {
> > [TPM_PPI_OP_CLEAR] = FLAGS,
> >
> > +};
> >
> > +void
> > +tpm_ppi_init(void)
> > +{
> > struct qemu_descriptor *qemu = NULL;
> > while (1) {
> >    qemu  = find_acpi_table_iter(QEMU_SIGNATURE, qemu);
> >    if (!qemu)
> >        return;
> >    if (!memcmp("QEMU", qemu->oem_id, 5) && !memcmp("CONF", qemu->oem_table_id, 5))
> >        break;
> > }
> > tp = (struct tpm_ppi *)(u32)qemu->tpmppi_address;
> > dprintf(DEBUG_tcg, "TCGBIOS: TPM PPI struct at %p\n", tp);
> > memset(&tp->func, 0, sizeof(tp->func));
> > switch (qemu->tpmppi_version) {
> > case TPM_PPI_VERSION_1_30:
> >    switch (qemu->tpm_version) {
> >    case TPM_VERSION_1_2:
> >        memcpy(&tp->func, tpm12_ppi_funcs, sizeof(tpm12_ppi_funcs));
> >        break;
> >    case TPM_VERSION_2:
> >        memcpy(&tp->func, tpm2_ppi_funcs, sizeof(tpm2_ppi_funcs));
> >        break;
> >    }
>
> Can you elaborate on what this does?  Why is SeaBIOS filling a memory
> addreses created by QEMU?  Why wouldn't QEMU just fill it with what it
> wants directly?

QEMU merely creates the device and the ACPI code. SeaBIOS implements 
which codes the user can send. The above array inside the virtual device 
contains flags that describe the codes that the user can send. If OVMF 
was to implement less codes, less bytes would be set. If another 
firmware implemented the possibility to prevent the user from sending 
certain codes, the TPM_PPI_FUNC_BLOCKED flag could be set for example so 
that ACPI would refuse to set the code for the next reboot. It's 
parametrizing the interface between ACPI and firmware.

Stefan
> -Kevin
> >    break;
> > }
> > if (!tp->ppin) {
> >    tp->ppin = 1;
> >    tp->pprq = 0;
> >    tp->lppr = 0;
> > }
> >
> > +}
> >
> > +void
> > +tpm_ppi_process(void)
> > +{
> > tpm_ppi_code op;
> > if (tp) {
> >    op = tp->pprq;
> >    if (!op) {
> >        /* intermediate step after a reboot? */
> >        op = nextStep;
> >    } else {
> >        /* last full opcode */
> >        tp->lppr = op;
> >    }
> >    if (op) {
> >        /*
> >         * Reset the opcode so we don't permanently reboot upon
> >         * code 3 (Activate).
> >         */
> >        tp->pprq = 0;
> >        printf("Processing TPM PPI opcode %d\n", op);
> >        tpm_process_cfg(op, 0, &tp->pprp);
> >    }
> > }
> >
> > +}
> > diff --git a/src/tcgbios.h b/src/tcgbios.h
> > index 32fb941..52b86f2 100644
> > --- a/src/tcgbios.h
> > +++ b/src/tcgbios.h
> > @@ -16,4 +16,7 @@ void tpm_option_rom(const void *addr, u32 len);
> >   int tpm_can_show_menu(void);
> >   void tpm_menu(void);
> >
> > +void tpm_ppi_init(void);
> > +void tpm_ppi_process(void);
> > #endif /* TCGBIOS_H */