[PATCH] tlv: Add tlv_bind_serial mapping

[Ahmad Fatoum]

Hi,

On 11/12/25 5:43 PM, 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 SoC serial number (a.k.a. SoC
> UID) of the unit, rendering a signed TLV with such a field invalid for
> all but one unit.
> 
> When generating TLVs that use this mapping, the exact case-sensitive
> string representation of the serial_number must be taken into account:
> All existing soc drivers supply the serial_number as uppercase
> hexadecimal representation without a prefix.
> 
> Add the special mapping tlv_bind_serial that aborts TLV parsing if the
> supplied string does not match the SoC serial 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. These parsers will store the serial_number in the
> "bound-serial-number" field.

as we have $global.serial_number, which is a different thing, I would
prefer to be more explicit here. Why not call it bound-soc-uid?

> Signed-off-by: Jonas Rebmann <jre at pengutronix.de>
> ---
>  common/tlv/barebox.c | 32 ++++++++++++++++++++++++++++++++
>  include/tlv/tlv.h    |  1 +
>  2 files changed, 33 insertions(+)
> 
> diff --git a/common/tlv/barebox.c b/common/tlv/barebox.c
> index 24de3eeaaa..cba9c3e2da 100644
> --- a/common/tlv/barebox.c
> +++ b/common/tlv/barebox.c
> @@ -3,6 +3,10 @@
>  #include <common.h>
>  #include <net.h>
>  #include <tlv/tlv.h>
> +#include <driver.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 +20,32 @@ int tlv_handle_serial(struct tlv_device *dev, struct tlv_mapping *map, u16 len,
>  	return 0;
>  }
>  
> +int tlv_bind_serial(struct tlv_device *dev, struct tlv_mapping *map, u16 len, const u8 *val)
> +{
> +	struct bus_type *bus;
> +	struct device_d *socdev;
> +	const char *soc_serial;
> +	char *tlv_serial = basprintf("%.*s", len, val);

strndup would also work here.

> +
> +	bus = get_bus_by_name("soc");
> +	if (!bus) {
> +		pr_err("No 'soc' bus found\n");

goto out and use a common error message? That way you also cover the
case of no socdev existing.

> +		return -EACCES;
> +	}
> +
> +	for_each_device(socdev) {
> +		soc_serial = dev_get_param(socdev, "serial_number");
> +		if (!soc_serial)
> +			continue;
> +
> +		if (streq_ptr(tlv_serial, soc_serial))
> +			return __tlv_format_str(dev, map, len, val) ? 0 : -ENOMEM;

	return tlv_format_str(...) directly instead?

I talked with Sascha yesterday and I believe he is implementing a common
get_soc_uid(). If so, that might be suitable for use here.

Cheers,
Ahmad

> +
> +	}
> +
> +	return -EACCES;
> +}
> +
>  int tlv_handle_eth_address(struct tlv_device *dev, struct tlv_mapping *map, u16 len, const u8 *val)
>  {
>  	int i;
> @@ -169,6 +199,8 @@ 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 */
> +	{ 0x0024, tlv_bind_serial, "bound-serial-number"},
>  	{ /* sentintel */ },
>  };
>  
> diff --git a/include/tlv/tlv.h b/include/tlv/tlv.h
> index 536f61646c..cadade27b4 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_serial(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: f485ddfccf960959d25462073528d314b8bf1aea
> change-id: 20251112-tlv_bind_serial-b8b24a6fd4a0
> 
> Best regards,
> --  
> Jonas Rebmann <jre at pengutronix.de>
> 
> 
> 

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