Re: [PATCH v2] tlv: Add tlv_bind_soc_uid mapping

["Jan Lübbe" <jlu@pengutronix.de>]

On Mon, 2025-11-17 at 18:14 +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.
> 
> 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);
> +
> +	if (streq_ptr(tlv_serial, barebox_get_soc_uid()))
> +		return __tlv_format_str(dev, map, len, val) ? 0 : -ENOMEM;
> +
> +	return -EACCES;
> +}
> +
>  int tlv_handle_eth_address(struct tlv_device *dev, struct tlv_mapping *map, u16 len, const u8 *val)
>  {
>  	int i;
> @@ -169,6 +183,8 @@ struct tlv_mapping barebox_tlv_v1_mappings[] = {
>  	{ 0x0011, tlv_handle_eth_address, "ethernet-address" },
>  	/* A sequence of multiple Ethernet addresses */
>  	{ 0x0012, tlv_handle_eth_address_seq, "ethernet-address" },
> +	/* Reject TLVs if device serial number string does not match CPU serial */

This still used the 'serial' term.

> +	{ 0x0024, tlv_bind_soc_uid, "bound-soc_uid"},

Don't start mixing '-' and '_'. All existing property names use only '-'.

Jan

>  	{ /* sentintel */ },
>  };
>  
> @@ -212,4 +228,4 @@ static int tlv_register_default(void)
>  	}
>  	return 0;
>  }
> -device_initcall(tlv_register_default);
> +late_initcall(tlv_register_default);
> diff --git a/include/tlv/tlv.h b/include/tlv/tlv.h
> index 536f61646c..54e3afed45 100644
> --- a/include/tlv/tlv.h
> +++ b/include/tlv/tlv.h
> @@ -37,6 +37,7 @@ extern int tlv_format_hex(struct tlv_device *dev, struct tlv_mapping *map, u16 l
>  extern int tlv_format_mac(struct tlv_device *dev, struct tlv_mapping *map, u16 len, const u8 *val);
>  extern int tlv_format_blob(struct tlv_device *dev, struct tlv_mapping *map, u16 len, const u8 *val);
>  extern int tlv_handle_serial(struct tlv_device *dev, struct tlv_mapping *map, u16 len, const u8 *val);
> +extern int tlv_bind_soc_uid(struct tlv_device *dev, struct tlv_mapping *map, u16 len, const u8 *val);
>  extern int tlv_handle_eth_address(struct tlv_device *dev, struct tlv_mapping *map, u16 len, const u8 *val);
>  extern int tlv_handle_eth_address_seq(struct tlv_device *dev, struct tlv_mapping *map, u16 len, const u8 *val);
>  
> 
> ---
> base-commit: bafc52d7dc93accb213271e3e5c267c4335d8cb2
> change-id: 20251112-tlv_bind_serial-b8b24a6fd4a0
> 
> Best regards,
> --  
> Jonas Rebmann <jre@pengutronix.de>
> 
> 
> 

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