Re: [PATCH v2] tpm-v2: allow algoirthm name to be configured for pcr_read and pcr_extend

[Ilias Apalodimas <ilias.apalodimas@linaro.org>]

On Sat, 30 Mar 2024 at 09:15, Ilias Apalodimas
<ilias.apalodimas@linaro.org> wrote:
>
> Hi Tim
>
> On Sat, 30 Mar 2024 at 02:40, Tim Harvey <tharvey@gateworks.com> wrote:
> >
> > On Thu, Mar 28, 2024 at 11:18 PM Ilias Apalodimas
> > <ilias.apalodimas@linaro.org> wrote:
> > >
> > > Hi Tim,
> > >
> > > On Thu, 28 Mar 2024 at 19:01, Tim Harvey <tharvey@gateworks.com> wrote:
> > > >
> > > > For pcr_read and pcr_extend commands allow the digest algorithm to be
> > > > specified by an additional argument. If not specified it will default to
> > > > SHA256 for backwards compatibility.
> > > >
> > > > A follow-on to this could be to extend all PCR banks with the detected
> > > > algo when the <digest_algo> argument is 'auto'.
> > > >
> > > > Signed-off-by: Tim Harvey <tharvey@gateworks.com>
> > > > ---
> > > > v2:
> > > >  - use tpm2_algorithm_to_len
> > > >  - use enum tpm2_algorithms
> > > >  - make function names and parameter names more consistent with existing
> > > >    tpm-v2 functions
> > > >  - fix various spelling errors
> > > > ---
> > > >  cmd/tpm-v2.c     | 49 ++++++++++++++++++++++++++++++++++--------------
> > > >  include/tpm-v2.h | 18 ++++++++++++++++++
> > > >  lib/tpm-v2.c     | 34 +++++++++++++++++++++++++++++++++
> > > >  3 files changed, 87 insertions(+), 14 deletions(-)
> > > >
> > > > diff --git a/cmd/tpm-v2.c b/cmd/tpm-v2.c
> > > > index 7e479b9dfe36..2343b4d9cb9e 100644
> > > > --- a/cmd/tpm-v2.c
> > > > +++ b/cmd/tpm-v2.c
> > > > @@ -99,11 +99,19 @@ static int do_tpm2_pcr_extend(struct cmd_tbl *cmdtp, int flag, int argc,
> > > >         struct tpm_chip_priv *priv;
> > > >         u32 index = simple_strtoul(argv[1], NULL, 0);
> > > >         void *digest = map_sysmem(simple_strtoul(argv[2], NULL, 0), 0);
> > > > +       int algo = TPM2_ALG_SHA256;
> > > > +       int algo_len;
> > > >         int ret;
> > > >         u32 rc;
> > > >
> > > > -       if (argc != 3)
> > > > +       if (argc < 3 || argc > 4)
> > > >                 return CMD_RET_USAGE;
> > > > +       if (argc == 4) {
> > > > +               algo = tpm2_name_to_algorithm(argv[3]);
> > > > +               if (algo < 0)
> > > > +                       return CMD_RET_FAILURE;
> > > > +       }
> > > > +       algo_len = tpm2_algorithm_to_len(algo);
> > > >
> > > >         ret = get_tpm(&dev);
> > > >         if (ret)
> > > > @@ -116,8 +124,12 @@ static int do_tpm2_pcr_extend(struct cmd_tbl *cmdtp, int flag, int argc,
> > > >         if (index >= priv->pcr_count)
> > > >                 return -EINVAL;
> > > >
> > > > -       rc = tpm2_pcr_extend(dev, index, TPM2_ALG_SHA256, digest,
> > > > -                            TPM2_DIGEST_LEN);
> > > > +       rc = tpm2_pcr_extend(dev, index, algo, digest, algo_len);
> > > > +       if (!rc) {
> > > > +               printf("PCR #%u extended with %d byte %s digest\n", index,
> > > > +                      algo_len, tpm2_algorithm_name(algo));
> > > > +               print_byte_string(digest, algo_len);
> > > > +       }
> > > >
> > > >         unmap_sysmem(digest);
> > > >
> > > > @@ -127,15 +139,23 @@ static int do_tpm2_pcr_extend(struct cmd_tbl *cmdtp, int flag, int argc,
> > > >  static int do_tpm_pcr_read(struct cmd_tbl *cmdtp, int flag, int argc,
> > > >                            char *const argv[])
> > > >  {
> > > > +       enum tpm2_algorithms algo = TPM2_ALG_SHA256;
> > > >         struct udevice *dev;
> > > >         struct tpm_chip_priv *priv;
> > > >         u32 index, rc;
> > > > +       int algo_len;
> > > >         unsigned int updates;
> > > >         void *data;
> > > >         int ret;
> > > >
> > > > -       if (argc != 3)
> > > > +       if (argc < 3 || argc > 4)
> > > >                 return CMD_RET_USAGE;
> > > > +       if (argc == 4) {
> > > > +               algo = tpm2_name_to_algorithm(argv[3]);
> > > > +               if (algo < 0)
> > > > +                       return CMD_RET_FAILURE;
> > > > +       }
> > > > +       algo_len = tpm2_algorithm_to_len(algo);
> > > >
> > > >         ret = get_tpm(&dev);
> > > >         if (ret)
> > > > @@ -151,11 +171,12 @@ static int do_tpm_pcr_read(struct cmd_tbl *cmdtp, int flag, int argc,
> > > >
> > > >         data = map_sysmem(simple_strtoul(argv[2], NULL, 0), 0);
> > > >
> > > > -       rc = tpm2_pcr_read(dev, index, priv->pcr_select_min, TPM2_ALG_SHA256,
> > > > -                          data, TPM2_DIGEST_LEN, &updates);
> > > > +       rc = tpm2_pcr_read(dev, index, priv->pcr_select_min, algo,
> > > > +                          data, algo_len, &updates);
> > > >         if (!rc) {
> > > > -               printf("PCR #%u content (%u known updates):\n", index, updates);
> > > > -               print_byte_string(data, TPM2_DIGEST_LEN);
> > > > +               printf("PCR #%u %s %d byte content (%u known updates):\n", index,
> > > > +                      tpm2_algorithm_name(algo), algo_len, updates);
> > > > +               print_byte_string(data, algo_len);
> > > >         }
> > > >
> > > >         unmap_sysmem(data);
> > > > @@ -415,14 +436,14 @@ U_BOOT_CMD(tpm2, CONFIG_SYS_MAXARGS, 1, do_tpm, "Issue a TPMv2.x command",
> > > >  "    <hierarchy> is one of:\n"
> > > >  "        * TPM2_RH_LOCKOUT\n"
> > > >  "        * TPM2_RH_PLATFORM\n"
> > > > -"pcr_extend <pcr> <digest_addr>\n"
> > > > -"    Extend PCR #<pcr> with digest at <digest_addr>.\n"
> > > > +"pcr_extend <pcr> <digest_addr> [<digest_algo>]\n"
> > > > +"    Extend PCR #<pcr> with digest at <digest_addr> with digest_algo.\n"
> > > >  "    <pcr>: index of the PCR\n"
> > > > -"    <digest_addr>: address of a 32-byte SHA256 digest\n"
> > > > -"pcr_read <pcr> <digest_addr>\n"
> > > > -"    Read PCR #<pcr> to memory address <digest_addr>.\n"
> > > > +"    <digest_addr>: address of digest of digest_algo type (defaults to SHA256)\n"
> > > > +"pcr_read <pcr> <digest_addr> [<digest_algo>]\n"
> > > > +"    Read PCR #<pcr> to memory address <digest_addr> with <digest_algo>.\n"
> > > >  "    <pcr>: index of the PCR\n"
> > > > -"    <digest_addr>: address to store the a 32-byte SHA256 digest\n"
> > > > +"    <digest_addr>: address of digest of digest_algo type (defaults to SHA256)\n"
> > > >  "get_capability <capability> <property> <addr> <count>\n"
> > > >  "    Read and display <count> entries indexed by <capability>/<property>.\n"
> > > >  "    Values are 4 bytes long and are written at <addr>.\n"
> > > > diff --git a/include/tpm-v2.h b/include/tpm-v2.h
> > > > index 33dd103767c4..933882fcbf97 100644
> > > > --- a/include/tpm-v2.h
> > > > +++ b/include/tpm-v2.h
> > > > @@ -965,4 +965,22 @@ u32 tpm2_enable_nvcommits(struct udevice *dev, uint vendor_cmd,
> > > >   */
> > > >  u32 tpm2_auto_start(struct udevice *dev);
> > > >
> > > > +/**
> > > > + * tpm2_name_to_algorithm() - Return an algorithm id given a supported
> > > > + *                           algorithm name
> > > > + *
> > > > + * @name: algorithm name
> > > > + * Return: enum tpm2_algorithms or -EINVAL
> > > > + */
> > > > +enum tpm2_algorithms tpm2_name_to_algorithm(const char *name);
> > > > +
> > > > +/**
> > > > + * tpm2_algorithm_name() - Return an algorithm name string for a
> > > > + *                        supported algorithm id
> > > > + *
> > > > + * @algorithm_id: algorithm defined in enum tpm2_algorithms
> > > > + * Return: algorithm name string or ""
> > > > + */
> > > > +const char *tpm2_algorithm_name(enum tpm2_algorithms);
> > > > +
> > > >  #endif /* __TPM_V2_H */
> > > > diff --git a/lib/tpm-v2.c b/lib/tpm-v2.c
> > > > index 68eaaa639f89..19b2535682e1 100644
> > > > --- a/lib/tpm-v2.c
> > > > +++ b/lib/tpm-v2.c
> > > > @@ -29,6 +29,13 @@ const enum tpm2_algorithms tpm2_supported_algorithms[4] = {
> > > >         TPM2_ALG_SHA512,
> > > >  };
> > > >
> > > > +const char *tpm2_supported_algorithm_names[4] = {
> > > > +       "sha1",
> > > > +       "sha256",
> > > > +       "sha384",
> > > > +       "sha512",
> > > > +};
> > > > +
> > >
> > > Overall this looks correct(but we don't need the [4] in the definition
> > > tbh). However, keeping the info in 2 different places is not ideal.
> > > We used to have a nice struct array that had all the info tightly together [0].
> > >
> > > The struct looked like
> > >
> > > struct digest_info {
> > > u16 hash_alg;
> > > u32 hash_mask;
> > > u16 hash_len;
> > > };
> > >
> > > static const struct digest_info hash_algo_list[] = {
> > > {
> > > TPM2_ALG_SHA1,
> > > EFI_TCG2_BOOT_HASH_ALG_SHA1,
> > > TPM2_SHA1_DIGEST_SIZE,
> > > },
> > > {
> > > TPM2_ALG_SHA256,
> > > EFI_TCG2_BOOT_HASH_ALG_SHA256,
> > > TPM2_SHA256_DIGEST_SIZE,
> > > },
> > > {
> > > TPM2_ALG_SHA384,
> > > EFI_TCG2_BOOT_HASH_ALG_SHA384,
> > > TPM2_SHA384_DIGEST_SIZE,
> > > },
> > > {
> > > TPM2_ALG_SHA512,
> > > EFI_TCG2_BOOT_HASH_ALG_SHA512,
> > > TPM2_SHA512_DIGEST_SIZE,
> > > },
> > > };
> > >
> > > In short, we need to
> > > - define the algorithm registry as defined by the TCG spec
> > >   /* Algorithm Registry */
> > >   #define EFI_TCG2_BOOT_HASH_ALG_SHA1    0x00000001
> > >   #define EFI_TCG2_BOOT_HASH_ALG_SHA256  0x00000002
> > >   #define EFI_TCG2_BOOT_HASH_ALG_SHA384  0x00000004
> > >   #define EFI_TCG2_BOOT_HASH_ALG_SHA512  0x00000008
> > >   #define EFI_TCG2_BOOT_HASH_ALG_SM3_256 0x00000010
> > >
> >
> > the above defines do not make sense to me if they are truely supposed
> > to be masks compared to what we currently have:
> >
> > enum tpm2_algorithms {
> >         TPM2_ALG_SHA1           = 0x04,
> >         TPM2_ALG_XOR            = 0x0A,
> >         TPM2_ALG_SHA256         = 0x0B,
> >         TPM2_ALG_SHA384         = 0x0C,
> >         TPM2_ALG_SHA512         = 0x0D,
> >         TPM2_ALG_NULL           = 0x10,
> >         TPM2_ALG_SM3_256        = 0x12,
> > };
> > #define tpm2_algorithm_to_mask(a)       (1 << (a))
>
> Yes, this is a bit confusing.  We are *not* using those definitions
> when calling tpm2_algorithm_to_mask(). Instead const enum of
> tpm2_supported_algorithms[] is used which yields the same values.
>
> >
> > Is digest_info.hash_mask from 2023.04 something else or were those
> > defines just wrong (struct digest_info didn't seem to be used anywhere
> > in 2023.04)
>
> It's probably present in 2022.X versions. The link included in the
> mail is from 2022.01
> https://source.denx.de/u-boot/custodians/u-boot-tpm/-/blob/v2022.01-rc3/lib/efi_loader/efi_tcg2.c?ref_type=tags#L75
>
> >
> > I'm ok with changing tpm2_supported_algorithms to a struct which
> > defines name, algorithm_id, mask and len if I understand what values
> > they should be.
>
> I hope that's clear now. Basically if you checkout v2023.01 all the
> functions are in lib/efi_loader/efi_tcg.c
> You will need
>
> static const struct digest_info hash_algo_list[], alg_to_len and
> alg_to_mask functions. You can then add a new const char filed with
> the names you want to support in the command line
>
> Thanks for picking this up!
>
> /Ilias
>
> >
> > Sounds like your suggesting:
> > - add back struct digest_info
> > - make tpm2_supported_algorithms be an array of struct digtest_info
> > - use that array for tpm2_algorithm_to_len, tpm2_algorithm_to_mask,
> > tpm2_algorithm_to_len and tpm2_name_to_algorithm

Forgot to answer this one
- add back struct digest_info
- get rid of supported algorithms, since you wont need it anymore
- on struct digest_info add a string you can use on the command line
and the functions you need to retrieve/compare it

makes sense?
Thanks
/Ilias
> >
> > Tim
> >
> > > - Bring back the functions that exist in that branch. Pre 2023.07 all
> > > measured boot code lived in lib/efi_loader/efi_tcg.c, so we just need
> > > to copy them over
> > > - Add a new struct member with the name and a new function to retrieve it.
> > >
> > > [0] https://source.denx.de/u-boot/custodians/u-boot-tpm/-/blob/v2022.01-rc3/lib/efi_loader/efi_tcg2.c?ref_type=tags#L75
> > >
> > > I understand that's more than what your patch tries to achieve here. I
> > > am fine pulling this as-is and you/I can fix it up later unless you
> > > don't mind doing it in a v3.
> > >
> > > Thanks
> > > /Ilias
> > > >  int tcg2_get_active_pcr_banks(struct udevice *dev, u32 *active_pcr_banks)
> > > >  {
> > > >         u32 supported = 0;
> > > > @@ -1555,3 +1562,30 @@ u32 tpm2_enable_nvcommits(struct udevice *dev, uint vendor_cmd,
> > > >
> > > >         return 0;
> > > >  }
> > > > +
> > > > +enum tpm2_algorithms tpm2_name_to_algorithm(const char *name)
> > > > +{
> > > > +       enum tpm2_algorithms algo;
> > > > +       size_t i;
> > > > +
> > > > +       for (i = 0; i < ARRAY_SIZE(tpm2_supported_algorithms); ++i) {
> > > > +               algo = tpm2_supported_algorithms[i];
> > > > +               if (!strcasecmp(name, tpm2_supported_algorithm_names[i]))
> > > > +                       return algo;
> > > > +       }
> > > > +       printf("%s: unsupported algorithm %s\n", __func__, name);
> > > > +
> > > > +       return -EINVAL;
> > > > +}
> > > > +
> > > > +const char *tpm2_algorithm_name(enum tpm2_algorithms algo)
> > > > +{
> > > > +       size_t i;
> > > > +
> > > > +       for (i = 0; i < ARRAY_SIZE(tpm2_supported_algorithms); ++i) {
> > > > +               if (tpm2_supported_algorithms[i] == algo)
> > > > +                       return tpm2_supported_algorithm_names[i];
> > > > +       }
> > > > +
> > > > +       return "";
> > > > +}
> > > > --
> > > > 2.25.1
> > > >