[PATCH v3 11/11] tpm: Allow disabling platform hierarchy with TPM2

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

On Sat, Jan 23, 2021 at 10:26:07AM -0700, Simon Glass wrote:
> With TPM2 we don't actually lock the TPM once verified boot is finished.
> Instead we disable the platform hierarchy which serves the same purpose.
> Add an implementation of this so we can safely boot into the kernel.
> 
> Signed-off-by: Simon Glass <sjg@chromium.org>
> ---
> 
> (no changes since v2)
> 
> Changes in v2:
> - Add definition of TPM2_RC_NV_DEFINED return code
> 
>  include/tpm-v2.h | 13 +++++++++++++
>  lib/tpm-v2.c     | 35 +++++++++++++++++++++++++++++++++++
>  2 files changed, 48 insertions(+)
> 
> diff --git a/include/tpm-v2.h b/include/tpm-v2.h
> index 1ca1e7e2011..e18c8b1ccca 100644
> --- a/include/tpm-v2.h
> +++ b/include/tpm-v2.h
> @@ -235,6 +235,7 @@ enum tpm2_handles {
>  enum tpm2_command_codes {
>  	TPM2_CC_STARTUP		= 0x0144,
>  	TPM2_CC_SELF_TEST	= 0x0143,
> +	TPM2_CC_HIER_CONTROL	= 0x0121,
>  	TPM2_CC_CLEAR		= 0x0126,
>  	TPM2_CC_CLEARCONTROL	= 0x0127,
>  	TPM2_CC_HIERCHANGEAUTH	= 0x0129,
> @@ -272,6 +273,7 @@ enum tpm2_return_codes {
>  	TPM2_RC_COMMAND_CODE	= TPM2_RC_VER1 + 0x0043,
>  	TPM2_RC_AUTHSIZE	= TPM2_RC_VER1 + 0x0044,
>  	TPM2_RC_AUTH_CONTEXT	= TPM2_RC_VER1 + 0x0045,
> +	TPM2_RC_NV_DEFINED	= TPM2_RC_VER1 + 0x004c,
>  	TPM2_RC_NEEDS_TEST	= TPM2_RC_VER1 + 0x0053,
>  	TPM2_RC_WARN		= 0x0900,
>  	TPM2_RC_TESTING		= TPM2_RC_WARN + 0x000A,
> @@ -582,4 +584,15 @@ u32 tpm2_get_random(struct udevice *dev, void *data, u32 count);
>   */
>  u32 tpm2_write_lock(struct udevice *dev, u32 index);
>  
> +/**
> + * Disable access to any platform data
> + *
> + * This can be called to close off access to the firmware data in the data,
> + * before calling the kernel.
> + *
> + * @dev		TPM device
> + * @return code of the operation
> + */
> +u32 tpm2_disable_platform_hierarchy(struct udevice *dev);
> +
>  #endif /* __TPM_V2_H */
> diff --git a/lib/tpm-v2.c b/lib/tpm-v2.c
> index 35f3917aeb5..1b32661979d 100644
> --- a/lib/tpm-v2.c
> +++ b/lib/tpm-v2.c
> @@ -625,3 +625,38 @@ u32 tpm2_write_lock(struct udevice *dev, u32 index)
>  
>  	return tpm_sendrecv_command(dev, command_v2, NULL, NULL);
>  }
> +
> +u32 tpm2_disable_platform_hierarchy(struct udevice *dev)
> +{
> +	struct tpm_chip_priv *priv = dev_get_uclass_priv(dev);
> +	u8 command_v2[COMMAND_BUFFER_SIZE] = {
> +		/* header 10 bytes */
> +		tpm_u16(TPM2_ST_SESSIONS),	/* TAG */
> +		tpm_u32(10 + 4 + 13 + 5),	/* Length */
> +		tpm_u32(TPM2_CC_HIER_CONTROL),	/* Command code */
> +
> +		/* 4 bytes */
> +		tpm_u32(TPM2_RH_PLATFORM),	/* Primary platform seed */
> +
> +		/* session header 9 bytes */
> +		tpm_u32(9),			/* Header size */
> +		tpm_u32(TPM2_RS_PW),		/* Password authorisation */
> +		tpm_u16(0),			/* nonce_size */
> +		0,				/* session_attrs */
> +		tpm_u16(0),			/* auth_size */
> +
> +		/* payload 5 bytes */
> +		tpm_u32(TPM2_RH_PLATFORM),	/* Hierarchy to disable */
> +		0,				/* 0=disable */
> +	};
> +	int ret;
> +
> +	ret = tpm_sendrecv_command(dev, command_v2, NULL, NULL);
> +	log_info("ret=%s, %x\n", dev->name, ret);
> +	if (ret)
> +		return ret;
> +
> +	priv->plat_hier_disabled = true;
> +
> +	return 0;
> +}
> -- 
> 2.30.0.280.ga3ce27912f-goog
> 
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>