linux-kernel - Re: [PATCH v3 05/10] tpm2-sessions: Umask tpm_buf_append_hmac

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Message-ID: <aNu6834tzirFzKM7@earth.li>
Date: Tue, 30 Sep 2025 12:11:47 +0100
From: Jonathan McDowell <noodles@...th.li>
To: Jarkko Sakkinen <jarkko@...nel.org>
Cc: linux-integrity@...r.kernel.org, dpsmith@...rtussolutions.com,
	ross.philipson@...cle.com,
	Jarkko Sakkinen <jarkko.sakkinen@...nsys.com>,
	Peter Huewe <peterhuewe@....de>, Jason Gunthorpe <jgg@...pe.ca>,
	David Howells <dhowells@...hat.com>,
	Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Mimi Zohar <zohar@...ux.ibm.com>,
	open list <linux-kernel@...r.kernel.org>,
	"open list:KEYS/KEYRINGS" <keyrings@...r.kernel.org>,
	"open list:SECURITY SUBSYSTEM" <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v3 05/10] tpm2-sessions: Umask
 tpm_buf_append_hmac_session()

On Mon, Sep 29, 2025 at 10:48:27PM +0300, Jarkko Sakkinen wrote:
> From: Jarkko Sakkinen <jarkko.sakkinen@...nsys.com>
> 
> Open code tpm_buf_append_hmac_session_opt() in order to unmask the code
> paths in the call sites of tpm_buf_append_hmac_session().
> 
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...nsys.com>

Reviewed-by: Jonathan McDowell <noodles@...a.com>

> ---
> v3:
> - No changes.
> v2:
> - Uncorrupt the patch.
> ---
>  drivers/char/tpm/tpm2-cmd.c               | 14 +++++++++++---
>  include/linux/tpm.h                       | 23 -----------------------
>  security/keys/trusted-keys/trusted_tpm2.c | 12 ++++++++++--
>  3 files changed, 21 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index 86b1a4d859b9..c7bfa705ea8f 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -257,9 +257,17 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>  
>  	do {
>  		tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_GET_RANDOM);
> -		tpm_buf_append_hmac_session_opt(chip, &buf, TPM2_SA_ENCRYPT
> -						| TPM2_SA_CONTINUE_SESSION,
> -						NULL, 0);
> +		if (tpm2_chip_auth(chip)) {
> +			tpm_buf_append_hmac_session(chip, &buf,
> +						    TPM2_SA_ENCRYPT |
> +						    TPM2_SA_CONTINUE_SESSION,
> +						    NULL, 0);
> +		} else  {
> +			offset = buf.handles * 4 + TPM_HEADER_SIZE;
> +			head = (struct tpm_header *)buf.data;
> +			if (tpm_buf_length(&buf) == offset)
> +				head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
> +		}
>  		tpm_buf_append_u16(&buf, num_bytes);
>  		tpm_buf_fill_hmac_session(chip, &buf);
>  		err = tpm_transmit_cmd(chip, &buf,
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 1fa02e18e688..e72e7657faa2 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -532,29 +532,6 @@ void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
>  				 int passphraselen);
>  void tpm_buf_append_auth(struct tpm_chip *chip, struct tpm_buf *buf,
>  			 u8 *passphrase, int passphraselen);
> -static inline void tpm_buf_append_hmac_session_opt(struct tpm_chip *chip,
> -						   struct tpm_buf *buf,
> -						   u8 attributes,
> -						   u8 *passphrase,
> -						   int passphraselen)
> -{
> -	struct tpm_header *head;
> -	int offset;
> -
> -	if (tpm2_chip_auth(chip)) {
> -		tpm_buf_append_hmac_session(chip, buf, attributes, passphrase, passphraselen);
> -	} else  {
> -		offset = buf->handles * 4 + TPM_HEADER_SIZE;
> -		head = (struct tpm_header *)buf->data;
> -
> -		/*
> -		 * If the only sessions are optional, the command tag must change to
> -		 * TPM2_ST_NO_SESSIONS.
> -		 */
> -		if (tpm_buf_length(buf) == offset)
> -			head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
> -	}
> -}
>  
>  #ifdef CONFIG_TCG_TPM2_HMAC
>  
> diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
> index e165b117bbca..c414a7006d78 100644
> --- a/security/keys/trusted-keys/trusted_tpm2.c
> +++ b/security/keys/trusted-keys/trusted_tpm2.c
> @@ -482,8 +482,10 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
>  			   struct trusted_key_options *options,
>  			   u32 blob_handle)
>  {
> +	struct tpm_header *head;
>  	struct tpm_buf buf;
>  	u16 data_len;
> +	int offset;
>  	u8 *data;
>  	int rc;
>  
> @@ -518,8 +520,14 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
>  		tpm2_buf_append_auth(&buf, options->policyhandle,
>  				     NULL /* nonce */, 0, 0,
>  				     options->blobauth, options->blobauth_len);
> -		tpm_buf_append_hmac_session_opt(chip, &buf, TPM2_SA_ENCRYPT,
> -						NULL, 0);
> +		if (tpm2_chip_auth(chip)) {
> +			tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_ENCRYPT, NULL, 0);
> +		} else  {
> +			offset = buf.handles * 4 + TPM_HEADER_SIZE;
> +			head = (struct tpm_header *)buf.data;
> +			if (tpm_buf_length(&buf) == offset)
> +				head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
> +		}
>  	}
>  
>  	tpm_buf_fill_hmac_session(chip, &buf);
> -- 
> 2.39.5
> 
> 

J.

-- 
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