dearsky/pico-fido
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Add 4 pseudorandom bytes to allow indexing used by some RP entities.

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Fixes #185

Signed-off-by: Pol Henarejos <pol.henarejos@cttc.es>
This commit is contained in:
Pol Henarejos
2025-09-11 11:31:45 +02:00
parent 56d5c61044
commit 54fb02995f
2 changed files with 7 additions and 3 deletions
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8
src/fido/credential.c
View File

@@ -429,16 +429,20 @@ int credential_derive_resident(const uint8_t *cred_id, size_t cred_id_len, uint8
memset(outk, 0, CRED_RESIDENT_LEN);
const mbedtls_md_info_t *md_info = mbedtls_md_info_from_type(MBEDTLS_MD_SHA256);
uint8_t *cred_idr = outk + CRED_RESIDENT_HEADER_LEN;
mbedtls_md_hmac(md_info, cred_idr, 32, pico_serial.id, sizeof(pico_serial.id), outk);
memcpy(outk + 4, CRED_PROTO_RESIDENT, CRED_PROTO_RESIDENT_LEN);
outk[4 + CRED_PROTO_RESIDENT_LEN] = 0x00;
outk[4 + CRED_PROTO_RESIDENT_LEN + 1] = 0x00;
mbedtls_md_hmac(md_info, cred_idr, 32, (uint8_t *) "SLIP-0022", 9, cred_idr);
mbedtls_md_hmac(md_info, cred_idr, 32, (uint8_t *) cred_id, CRED_PROTO_LEN, cred_idr);
mbedtls_md_hmac(md_info, cred_idr, 32, (uint8_t *) "resident", 8, cred_idr);
mbedtls_md_hmac(md_info, cred_idr, 32, cred_id, cred_id_len, cred_idr);
memcpy(outk, CRED_PROTO_RESIDENT, CRED_PROTO_RESIDENT_LEN);
return 0;
}
bool credential_is_resident(const uint8_t *cred_id, size_t cred_id_len) {
return memcmp(cred_id, CRED_PROTO_RESIDENT, CRED_PROTO_RESIDENT_LEN) == 0;
return memcmp(cred_id + 4, CRED_PROTO_RESIDENT, CRED_PROTO_RESIDENT_LEN) == 0;
}
int credential_load_resident(const file_t *ef, const uint8_t *rp_id_hash, Credential *cred) {

2
src/fido/credential.h
View File

@@ -70,7 +70,7 @@ typedef struct Credential {
#define CRED_PROTO_RESIDENT CRED_PROTO_23_S
#define CRED_PROTO_RESIDENT_LEN 4
#define CRED_RESIDENT_HEADER_LEN (CRED_PROTO_RESIDENT_LEN + 4)
#define CRED_RESIDENT_HEADER_LEN (CRED_PROTO_RESIDENT_LEN + 6)
#define CRED_RESIDENT_LEN (CRED_RESIDENT_HEADER_LEN + 32)
typedef enum