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.
> + 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...
> + 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?
And again, you can drop "grub_" prefixes from all stuff which is
internal for a given C file.
Daniel
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