/*
 * x509_ed25519.h -- extract a raw Ed25519 public key from a DER-encoded
 * X.509 certificate's SubjectPublicKeyInfo (RFC 8410).
 *
 * Deliberately NOT a general ASN.1/X.509 parser (Milestone 6 decision,
 * FABRIC-2.md): walks exactly as far into the DER structure as needed
 * to reach SubjectPublicKeyInfo, verifies its AlgorithmIdentifier OID is
 * Ed25519 (1.3.101.112) and rejects anything else, then returns the raw
 * 32-byte key from the trailing BIT STRING. No signature verification,
 * no chain validation, no extension parsing -- this only answers "what
 * public key does this cert claim to hold," matching exactly what
 * ed25519_verify() needs as input.
 *
 * Freestanding C99, no libc beyond memcmp/memcpy (already provided by
 * src/starkernel/vm/host/shim.c in the kernel build).
 */
#ifndef STARKERNEL_X509_ED25519_H
#define STARKERNEL_X509_ED25519_H

#include <stdint.h>
#include <stddef.h>

/* Returns 0 on success (pubkey_out[32] filled), -1 on any malformed
 * encoding, unexpected structure, or non-Ed25519 algorithm. Never
 * faults on malformed input -- every DER length/tag is bounds-checked
 * against der_len before use. */
int x509_extract_ed25519_pubkey(const uint8_t *der, size_t der_len,
                                 uint8_t pubkey_out[32]);

#endif /* STARKERNEL_X509_ED25519_H */