Re: [PATCH v2] tlv: Add tlv_bind_soc_uid mapping

[Sascha Hauer <s.hauer@pengutronix.de>]

On Mon, Nov 17, 2025 at 06:14:06PM +0100, Jonas Rebmann wrote:
> Particularly when using secure boot with signed TLVs, it may be required
> to issue and sign TLVs for specific units. As typically all units of a
> board are compiled to validate TLVs against the same key, a "binding"
> mechanism is needed if interchange of TLVs across those units must be
> prevented. This mapping binds against the UID of the SoC, rendering a
> signed TLV with such a field invalid for all but the one unit.
> 
> When generating TLVs that use this mapping, the exact case-sensitive
> string representation of the SoC UID must be taken into account.

Do we really want to have this case-sensitive? I am not sure we're not
creating problems with this once somebody changes the case for
compatibility with the kernel, it was accidently wrong etc.

> 
> Add the special mapping tlv_bind_soc_uid that aborts TLV parsing if the
> supplied string does not match the SoC UID number.
> 
> Include this mapping in barebox_tlv_v1_mappings with tag 0x0024 to make
> it available in testing and in other setups using the generic tlv
> parsers.
> 
> Set up tlv_register_default as a late initcall so that it's loaded after
> the SoC UID was initialized.
> 
> Signed-off-by: Jonas Rebmann <jre@pengutronix.de>
> ---
> Changes in v2:
> - Switch to using barebox_get_soc_uid and rename and reword everything
>   accordingly (serial number -> soc uid)
> - Init tlv_register_default as late_initcall instead of device_initcall
> - Link to v1: https://lore.barebox.org/barebox/20251112-tlv_bind_serial-v1-1-638cf222553a@pengutronix.de
> ---
>  common/tlv/barebox.c | 18 +++++++++++++++++-
>  include/tlv/tlv.h    |  1 +
>  2 files changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/common/tlv/barebox.c b/common/tlv/barebox.c
> index 24de3eeaaa..fdba9fa2a5 100644
> --- a/common/tlv/barebox.c
> +++ b/common/tlv/barebox.c
> @@ -1,8 +1,12 @@
>  // SPDX-License-Identifier: GPL-2.0-only
>  
> +#include "barebox-info.h"
>  #include <common.h>
>  #include <net.h>
>  #include <tlv/tlv.h>
> +#include <param.h>
> +#include <string.h>
> +
>  
>  int tlv_handle_serial(struct tlv_device *dev, struct tlv_mapping *map, u16 len, const u8 *val)
>  {
> @@ -16,6 +20,16 @@ int tlv_handle_serial(struct tlv_device *dev, struct tlv_mapping *map, u16 len,
>  	return 0;
>  }
>  
> +int tlv_bind_soc_uid(struct tlv_device *dev, struct tlv_mapping *map, u16 len, const u8 *val)
> +{
> +	char *tlv_serial = basprintf("%.*s", len, val);

tlv_serial is not freed.

> +
> +	if (streq_ptr(tlv_serial, barebox_get_soc_uid()))
> +		return __tlv_format_str(dev, map, len, val) ? 0 : -ENOMEM;

Why not simply forward the return value __tlv_format_str() instead?
(which is 0 or -ENOMEM anyway).

Sascha


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