On Wed, Oct 16, 2024 at 05:44:29PM +0200, Daniel Kiper wrote:
> On Fri, Sep 06, 2024 at 05:11:14PM +0800, Gary Lin via Grub-devel wrote:
> > From: Hernan Gatta <hega...@linux.microsoft.com>
> >
> > The TPM2 key protector is a module that enables the automatic retrieval
> > of a fully-encrypted disk's unlocking key from a TPM 2.0.
> >
> > The theory of operation is such that the module accepts various
> > arguments, most of which are optional and therefore possess reasonable
> > defaults. One of these arguments is the keyfile/tpm2key parameter, which
> > is mandatory. There are two supported key formats:
> >
> > 1. Raw Sealed Key (--keyfile)
> > When sealing a key with TPM2_Create, the public portion of the sealed
> > key is stored in TPM2B_PUBLIC, and the private portion is in
> > TPM2B_PRIVATE. The raw sealed key glues the fully marshalled
> > TPM2B_PUBLIC and TPM2B_PRIVATE into one file.
> >
> > 2. TPM 2.0 Key (--tpm2key)
> > The following is the ASN.1 definition of TPM 2.0 Key File:
> >
> > TPMPolicy ::= SEQUENCE {
> > CommandCode [0] EXPLICIT INTEGER
> > CommandPolicy [1] EXPLICIT OCTET STRING
> > }
> >
> > TPMAuthPolicy ::= SEQUENCE {
> > Name [0] EXPLICIT UTF8STRING OPTIONAL
> > Policy [1] EXPLICIT SEQUENCE OF TPMPolicy
> > }
> >
> > TPMKey ::= SEQUENCE {
> > type OBJECT IDENTIFIER
> > emptyAuth [0] EXPLICIT BOOLEAN OPTIONAL
> > policy [1] EXPLICIT SEQUENCE OF TPMPolicy OPTIONAL
> > secret [2] EXPLICIT OCTET STRING OPTIONAL
> > authPolicy [3] EXPLICIT SEQUENCE OF TPMAuthPolicy OPTIONAL
> > description [4] EXPLICIT UTF8String OPTIONAL,
> > rsaParent [5] EXPLICIT BOOLEAN OPTIONAL,
> > parent INTEGER
> > pubkey OCTET STRING
> > privkey OCTET STRING
> > }
> >
> > The TPM2 key protector only expects a "sealed" key in DER encoding,
> > so 'type' is always 2.23.133.10.1.5, 'emptyAuth' is 'TRUE', and
> > 'secret' is empty. 'policy' and 'authPolicy' are the possible policy
> > command sequences to construst the policy digest to unseal the key.
> > Similar to the raw sealed key, the public portion (TPM2B_PUBLIC) of
> > the sealed key is stored in 'pubkey', and the private portion
> > (TPM2B_PRIVATE) is in 'privkey'.
> >
> > For more details:
> > https://www.hansenpartnership.com/draft-bottomley-tpm2-keys.html
> >
> > This sealed key file is created via the grub-protect tool. The tool
> > utilizes the TPM's sealing functionality to seal (i.e., encrypt) an
> > unlocking key using a Storage Root Key (SRK) to the values of various
> > Platform Configuration Registers (PCRs). These PCRs reflect the state
> > of the system as it boots. If the values are as expected, the system
> > may be considered trustworthy, at which point the TPM allows for a
> > caller to utilize the private component of the SRK to unseal (i.e.,
> > decrypt) the sealed key file. The caller, in this case, is this key
> > protector.
> >
> > The TPM2 key protector registers two commands:
> >
> > - tpm2_key_protector_init: Initializes the state of the TPM2 key
> > protector for later usage, clearing any
> > previous state, too, if any.
> >
> > - tpm2_key_protector_clear: Clears any state set by tpm2_key_protector_init.
> >
> > The way this is expected to be used requires the user to, either
> > interactively or, normally, via a boot script, initialize/configure
> > the key protector and then specify that it be used by the 'cryptomount'
> > command (modifications to this command are in a different patch).
> >
> > For instance, to unseal the raw sealed key file:
> >
> > tpm2_key_protector_init --keyfile=(hd0,gpt1)/efi/grub2/sealed-1.key
> > cryptomount -u <PART1_UUID> -P tpm2
> >
> > tpm2_key_protector_init --keyfile=(hd0,gpt1)/efi/grub2/sealed-2.key
> > --pcrs=7,11
> > cryptomount -u <PART2_UUID> -P tpm2
> >
> > Or, to unseal the TPM 2.0 Key file:
> >
> > tpm2_key_protector_init --tpm2key=(hd0,gpt1)/efi/grub2/sealed-1.tpm
> > cryptomount -u <PART1_UUID> -P tpm2
> >
> > tpm2_key_protector_init --tpm2key=(hd0,gpt1)/efi/grub2/sealed-2.tpm
> > --pcrs=7,11
> > cryptomount -u <PART2_UUID> -P tpm2
> >
> > If a user does not initialize the key protector and attempts to use it
> > anyway, the protector returns an error.
> >
> > Before unsealing the key, the TPM2 key protector follows the "TPMPolicy"
> > sequences to enforce the TPM policy commands to construct a valid policy
> > digest to unseal the key.
> >
> > For the TPM 2.0 Key files, 'authPolicy' may contain multiple "TPMPolicy"
> > sequences, the TPM2 key protector iterates 'authPolicy' to find a valid
> > sequence to unseal key. If 'authPolicy' is empty or all sequences in
> > 'authPolicy' fail, the protector tries the one from 'policy'. In case
> > 'policy' is also empty, the protector creates a "TPMPolicy" sequence
> > based on the given PCR selection.
> >
> > For the raw sealed key, the TPM2 key protector treats the key file as a
> > TPM 2.0 Key file without 'authPolicy' and 'policy', so the "TPMPolicy"
> > sequence is always based on the PCR selection from the command
> > parameters.
> >
> > This commit only supports one policy command: TPM2_PolicyPCR. The
> > command set will be extended to support advanced features, such as
> > authorized policy, in the later commits.
> >
> > Cc: Stefan Berger <stef...@linux.ibm.com>
> > Cc: James Bottomley <j...@linux.ibm.com>
> > Signed-off-by: Hernan Gatta <hega...@linux.microsoft.com>
> > Signed-off-by: Gary Lin <g...@suse.com>
> > ---
> > grub-core/Makefile.core.def | 11 +
> > grub-core/commands/tpm2_key_protector/args.c | 129 ++
> > .../commands/tpm2_key_protector/module.c | 1153 +++++++++++++++++
> > grub-core/commands/tpm2_key_protector/tpm2.h | 36 +
> > .../commands/tpm2_key_protector/tpm2_args.h | 49 +
> > .../commands/tpm2_key_protector/tpm2key.asn | 49 +
> > .../commands/tpm2_key_protector/tpm2key.c | 499 +++++++
> > .../commands/tpm2_key_protector/tpm2key.h | 87 ++
> > .../tpm2_key_protector/tpm2key_asn1_tab.c | 63 +
> > 9 files changed, 2076 insertions(+)
> > create mode 100644 grub-core/commands/tpm2_key_protector/args.c
> > create mode 100644 grub-core/commands/tpm2_key_protector/module.c
> > create mode 100644 grub-core/commands/tpm2_key_protector/tpm2.h
> > create mode 100644 grub-core/commands/tpm2_key_protector/tpm2_args.h
> > create mode 100644 grub-core/commands/tpm2_key_protector/tpm2key.asn
> > create mode 100644 grub-core/commands/tpm2_key_protector/tpm2key.c
> > create mode 100644 grub-core/commands/tpm2_key_protector/tpm2key.h
> > create mode 100644 grub-core/commands/tpm2_key_protector/tpm2key_asn1_tab.c
> >
> > diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def
> > index 45b705a34..97ae4e49b 100644
> > --- a/grub-core/Makefile.core.def
> > +++ b/grub-core/Makefile.core.def
> > @@ -2578,6 +2578,17 @@ module = {
> > cppflags = '-I$(srcdir)/lib/tss2';
> > };
> >
> > +module = {
> > + name = tpm2_key_protector;
> > + common = commands/tpm2_key_protector/args.c;
> > + common = commands/tpm2_key_protector/module.c;
> > + common = commands/tpm2_key_protector/tpm2key.c;
> > + common = commands/tpm2_key_protector/tpm2key_asn1_tab.c;
> > + /* The plaform support of tpm2_key_protector depends on the tcg2
> > implementation in tss2. */
> > + enable = efi;
> > + cppflags = '-I$(srcdir)/lib/tss2 -I$(srcdir)/lib/libtasn1-grub';
> > +};
> > +
> > module = {
> > name = tr;
> > common = commands/tr.c;
> > diff --git a/grub-core/commands/tpm2_key_protector/args.c
> > b/grub-core/commands/tpm2_key_protector/args.c
> > new file mode 100644
> > index 000000000..c58cbe307
> > --- /dev/null
> > +++ b/grub-core/commands/tpm2_key_protector/args.c
> > @@ -0,0 +1,129 @@
> > +/*
> > + * GRUB -- GRand Unified Bootloader
> > + * Copyright (C) 2022 Microsoft Corporation
> > + * Copyright (C) 2024 Free Software Foundation, Inc.
> > + *
> > + * GRUB is free software: you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License as published by
> > + * the Free Software Foundation, either version 3 of the License, or
> > + * (at your option) any later version.
> > + *
> > + * GRUB is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with GRUB. If not, see <http://www.gnu.org/licenses/>.
> > + */
> > +
> > +#include <grub/err.h>
> > +#include <grub/mm.h>
> > +#include <grub/misc.h>
> > +
> > +#include "tpm2_args.h"
> > +
> > +grub_err_t
> > +grub_tpm2_protector_parse_pcrs (char *value, grub_uint8_t *pcrs,
> > + grub_uint8_t *pcr_count)
> > +{
> > + char *current_pcr = value;
> > + char *next_pcr;
> > + const char *pcr_end;
> > + grub_uint64_t pcr;
> > + grub_uint8_t i;
> > +
> > + if (grub_strlen (value) == 0)
> > + return GRUB_ERR_BAD_ARGUMENT;
> > +
> > + *pcr_count = 0;
> > + for (i = 0; i < TPM_MAX_PCRS; i++)
> > + {
> > + next_pcr = grub_strchr (current_pcr, ',');
> > + if (next_pcr == current_pcr)
> > + return grub_error (GRUB_ERR_BAD_ARGUMENT, "Empty entry in PCR list");
> > + if (next_pcr != NULL)
> > + *next_pcr = '\0';
> > +
> > + grub_errno = GRUB_ERR_NONE;
>
> This is probably remnant from previous version of the patch.
>
Ah, yeah. There is no need to reset grub_errno here.
> > + pcr = grub_strtoul (current_pcr, &pcr_end, 10);
> > + if (*current_pcr == '\0' || *pcr_end != '\0')
> > + return grub_error (GRUB_ERR_BAD_NUMBER, "Entry '%s' in PCR list is not
> > a number", current_pcr);
> > +
> > + if (pcr > TPM_MAX_PCRS)
> > + return grub_error (GRUB_ERR_OUT_OF_RANGE, "Entry %" PRIuGRUB_UINT64_T "
> > in PCR list is too large to be a PCR number, PCR numbers range from 0 to
> > %u", pcr, TPM_MAX_PCRS);
> > +
> > + pcrs[i] = (grub_uint8_t) pcr;
> > + ++(*pcr_count);
> > +
> > + if (next_pcr == NULL)
> > + break;
> > +
> > + current_pcr = next_pcr + 1;
> > + if (*current_pcr == '\0')
> > + return grub_error (GRUB_ERR_BAD_ARGUMENT, "Trailing comma at the end of
> > PCR list");
> > + }
> > +
> > + if (i == TPM_MAX_PCRS)
> > + return grub_error (GRUB_ERR_OUT_OF_RANGE, "Too many PCRs in PCR list,
> > the maximum number of PCRs is %u", TPM_MAX_PCRS);
> > +
> > + return GRUB_ERR_NONE;
> > +}
> > +
> > +grub_err_t
> > +grub_tpm2_protector_parse_asymmetric (const char *value,
> > + grub_srk_type_t *srk_type)
> > +{
> > + if (grub_strcasecmp (value, "ECC") == 0 ||
> > + grub_strcasecmp (value, "ECC_NIST_P256") == 0)
> > + {
> > + srk_type->type = TPM_ALG_ECC;
> > + srk_type->detail.ecc_curve = TPM_ECC_NIST_P256;
> > + }
> > + else if (grub_strcasecmp (value, "RSA") == 0 ||
> > + grub_strcasecmp (value, "RSA2048") == 0)
> > + {
> > + srk_type->type = TPM_ALG_RSA;
> > + srk_type->detail.rsa_bits = 2048;
> > + }
> > + else
> > + return grub_error (GRUB_ERR_OUT_OF_RANGE, "Value '%s' is not a valid
> > asymmetric key type", value);
> > +
> > + return GRUB_ERR_NONE;
> > +}
> > +
> > +grub_err_t
> > +grub_tpm2_protector_parse_bank (const char *value, TPM_ALG_ID_t *bank)
> > +{
> > + if (grub_strcasecmp (value, "SHA1") == 0)
> > + *bank = TPM_ALG_SHA1;
> > + else if (grub_strcasecmp (value, "SHA256") == 0)
> > + *bank = TPM_ALG_SHA256;
> > + else if (grub_strcasecmp (value, "SHA384") == 0)
> > + *bank = TPM_ALG_SHA384;
> > + else if (grub_strcasecmp (value, "SHA512") == 0)
> > + *bank = TPM_ALG_SHA512;
> > + else
> > + return grub_error (GRUB_ERR_OUT_OF_RANGE, "Value '%s' is not a valid
> > PCR bank", value);
> > +
> > + return GRUB_ERR_NONE;
> > +}
> > +
> > +grub_err_t
> > +grub_tpm2_protector_parse_tpm_handle (const char *value, TPM_HANDLE_t
> > *handle)
> > +{
> > + grub_uint64_t num;
> > + const char *str_end;
> > +
> > + grub_errno = GRUB_ERR_NONE;
>
> Ditto. Please fix similar problems everywhere...
>
Okay. Will remove the unnecessary grub_errno in the next version.
> > + num = grub_strtoul (value, &str_end, 0);
> > + if (*value == '\0' || *str_end != '\0')
> > + return grub_error (GRUB_ERR_BAD_NUMBER, "TPM handle value '%s' is not
> > a number", value);
> > +
> > + if (num > GRUB_UINT_MAX)
> > + return grub_error (GRUB_ERR_OUT_OF_RANGE, "Value %lu is too large to
> > be a TPM handle, TPM handles are unsigned 32-bit integers", num);
> > +
> > + *handle = (TPM_HANDLE_t) num;
> > +
> > + return GRUB_ERR_NONE;
> > +}
> > diff --git a/grub-core/commands/tpm2_key_protector/module.c
> > b/grub-core/commands/tpm2_key_protector/module.c
> > new file mode 100644
> > index 000000000..909c3cc6a
> > --- /dev/null
> > +++ b/grub-core/commands/tpm2_key_protector/module.c
> > @@ -0,0 +1,1153 @@
> > +/*
> > + * GRUB -- GRand Unified Bootloader
> > + * Copyright (C) 2022 Microsoft Corporation
> > + * Copyright (C) 2024 Free Software Foundation, Inc.
> > + *
> > + * GRUB is free software: you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License as published by
> > + * the Free Software Foundation, either version 3 of the License, or
> > + * (at your option) any later version.
> > + *
> > + * GRUB is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with GRUB. If not, see <http://www.gnu.org/licenses/>.
> > + */
> > +
> > +#include <grub/dl.h>
> > +#include <grub/extcmd.h>
> > +#include <grub/file.h>
> > +#include <grub/list.h>
> > +#include <grub/misc.h>
> > +#include <grub/mm.h>
> > +#include <grub/key_protector.h>
> > +
> > +#include <tss2_buffer.h>
> > +#include <tss2_types.h>
> > +#include <tss2_mu.h>
> > +
> > +#include "tpm2_args.h"
> > +#include "tpm2.h"
> > +#include "tpm2key.h"
> > +
> > +GRUB_MOD_LICENSE ("GPLv3+");
> > +
> > +typedef enum grub_tpm2_protector_mode
> > +{
> > + GRUB_TPM2_PROTECTOR_MODE_UNSET,
> > + GRUB_TPM2_PROTECTOR_MODE_SRK,
> > + GRUB_TPM2_PROTECTOR_MODE_NV
> > +} grub_tpm2_protector_mode_t;
> > +
> > +enum grub_tpm2_protector_options
> > +{
> > + OPTION_MODE,
> > + OPTION_PCRS,
> > + OPTION_BANK,
> > + OPTION_TPM2KEY,
> > + OPTION_KEYFILE,
> > + OPTION_SRK,
> > + OPTION_ASYMMETRIC,
> > + OPTION_NVINDEX
> > +};
>
> May I ask you to be more consistent and define enums
> as types like you did for grub_tpm2_protector_mode?
>
Okay.
> And again, you can drop "grub_" prefixes from all stuff which is
> internal for a given C file.
>
Will fix them in the next version.
Gary Lin
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