Robert Allan JamesandClaude Sonnet 5
2e7e957680
New freestanding, verify-only Ed25519 (RFC 8032) implementation:
include/starkernel/{sha512,fe25519,scalar25519,ed25519}.h +
src/starkernel/crypto/{sha512,fe25519,scalar25519,ed25519}.c, wired into
Makefile.starkernel. Kernel never signs or generates keys -- only
ed25519_verify() is needed; signing happens in the host-side mkcapsule
build tool via libsodium/OpenSSL.
Confirmed __int128 multiply/add/shift-by-constant compile with zero
undefined symbols on all three target toolchains (only division needs
libgcc's __udivti3, per timer.c's existing documented finding -- that
file's comment updated to narrow the claim, since it had been read as
"avoid __int128 entirely"). This enabled the standard 5-limb radix-2^51
field arithmetic representation.
An abandoned first attempt (10-limb radix-2^26, avoiding __int128 out of
premature caution) hit two real bugs, both invisible on inspection and
found only by property-based testing against Python's own bignum
arithmetic: a non-uniform-radix limb misalignment in multiplication, and
a double-counted carry. Verification chain: SHA-512 against known +
boundary vectors (7/7); field arithmetic property-tested 25,045 cases;
scalar-mod-L arithmetic 300 cases (L confirmed prime via Miller-Rabin
first); full verify() end-to-end against 110 real signatures from
Python's cryptography library, including tampered inputs and the RFC
8032 S>=L malleability attack -- all correctly accepted/rejected.
Compiles clean (zero warnings) and links on all three architectures,
confirmed via the mandatory three-arch QEMU boot. The code is linked but
not yet called from anywhere -- wiring into capsule_birth.c needs a
from-scratch X.509/DER parser first (Captain Bob chose real X.509 over a
raw-blob cert format this session), which is the next open item.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HZ8kNoTuP63pbQtro4qvrm
31 lines
1.1 KiB
C
31 lines
1.1 KiB
C
/* sha512.h -- freestanding SHA-512 (FIPS 180-4 / RFC 6234), C99, no libc
|
|
* beyond memcpy/memset (both available in the kernel via
|
|
* src/starkernel/vm/host/shim.c). No __int128 used -- 64-bit words only,
|
|
* portable to amd64/aarch64/riscv64 without libgcc helpers.
|
|
*/
|
|
#ifndef SHA512_H
|
|
#define SHA512_H
|
|
|
|
#include <stdint.h>
|
|
#include <stddef.h>
|
|
|
|
typedef struct {
|
|
uint64_t state[8];
|
|
uint64_t bitlen; /* total message length in bits, low 64 bits
|
|
* (SHA-512 defines a 128-bit length field; a
|
|
* single uint64_t of bit-length is enough for
|
|
* any message this kernel will ever hash --
|
|
* capsules and certs, not exabyte streams) */
|
|
uint8_t buf[128];
|
|
size_t buf_len;
|
|
} sha512_ctx_t;
|
|
|
|
void sha512_init(sha512_ctx_t *ctx);
|
|
void sha512_update(sha512_ctx_t *ctx, const uint8_t *data, size_t len);
|
|
void sha512_final(sha512_ctx_t *ctx, uint8_t out[64]);
|
|
|
|
/* Convenience one-shot. */
|
|
void sha512(const uint8_t *data, size_t len, uint8_t out[64]);
|
|
|
|
#endif /* SHA512_H */
|