Hi,
On 2025-10-14 13:03, Jonas Rebmann wrote:
Implement TLV signature using the existing placeholders for it. Use the
existing cryptographic primitives and public key handling used for
fitimage verification.
Signature is verified and then must be valid iff CONFIG_TLV_SIGNATURE is
enabled and a keyring is selected for the decoder. SHA256 hashing is
hardcoded for now.
As 16 bit are well sufficient to store the length of the signature
section in bytes, reduce it to its least significant 16 bit and reserve
the remaining 16 bit for future use.
As sig_len where the only reserved bits left, and where zero-reserved,
this leaves more wiggle room to still expand the format in the future.
Signed-off-by: Jonas Rebmann <[email protected]>
---
common/Kconfig | 4 +++
common/tlv/parser.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++
include/tlv/format.h | 22 ++++++++++----
3 files changed, 105 insertions(+), 5 deletions(-)
[...]
diff --git a/common/tlv/parser.c b/common/tlv/parser.c
index f74ada99d7..0a23beba4e 100644
--- a/common/tlv/parser.c
+++ b/common/tlv/parser.c
[...]
@@ -17,6 +93,7 @@ int tlv_parse(struct tlv_device *tlvdev,
struct tlv_mapping *map = NULL;
struct tlv_header *header = tlv_device_header(tlvdev);
u32 magic;
+ u16 reserved;
size_t size;
int ret = 0;
u32 crc = ~0;
@@ -24,6 +101,7 @@ int tlv_parse(struct tlv_device *tlvdev,
magic = be32_to_cpu(header->magic);
size = tlv_total_len(header);
+ reserved = get_unaligned_be16(&header->reserved);
if (size == SIZE_MAX) {
pr_warn("Invalid TLV header, overflows\n");
@@ -36,6 +114,12 @@ int tlv_parse(struct tlv_device *tlvdev,
return -EILSEQ;
}
+ if (decoder->signature_keyring) {
+ ret = tlv_verify(header, decoder->signature_keyring);
+ if (ret)
+ return ret;
+ }
At some point I accidentally dropped the special handling of a signed
TLV matched to a decoder that has signature disabled. I believe it is
correct that we keep parsing without signature verification but that v2
should add a warning e.g.:
} else if (get_unaligned_be16(&header->length_sig)) {
pr_warn("Skipping verification of TLV signature: "
"No keyring selected in decoder with magic %08x\n",
decoder->magic);
}
+
for_each_tlv(header, tlv) {
struct tlv_mapping **mappings;
u16 tag = TLV_TAG(tlv);
[...]
Regards,
Jonas
--
Pengutronix e.K. | Jonas Rebmann |
Steuerwalder Str. 21 | http://www.pengutronix.de/ |
31137 Hildesheim, Germany | Phone: +49-5121-206917-0 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-9 |
