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G.2 (v2.0.0): unified rng_get_bytes() entropy entry point; virtio-rng sole backend

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The QEMU-verifiable slice of the real-hardware RNG driver (per FABRIC-3.md
§G.2). New include/starkernel/rng.h + src/starkernel/rng/rng.c provide the
single entropy entry point: rng_init() probes the backend set (v2.0.0:
virtio-rng only) and, on no backend, prints a loud boot-time warning while
rng_get_bytes() returns RNG_ERR_NO_BACKEND - never silently degrading to a
deterministic seed. The backend-selection switch in rng.c is the exact seam
v2.5.0's per-arch drivers (amd64 RDRAND, riscv64 Zkr, aarch64 peripheral) plug
into without touching the call path.

Consumers route through the unified layer instead of virtio-rng directly:
capsule_mint.c (identity seed + drive_uuid) and kernel_main.c phase 8
(rng_init()). virtio_rng.c stays as the sole backend. Built clean on
amd64/aarch64/riscv64. QEMU amd64 boot: POST 1012/0/0 + ok>, "rng: backend =
virtio-rng" + "entropy: ready", Zuse identity confirmed from thumbdrive -
mint/cert behavior unchanged.

FABRIC-3.md §G.2 v2.0.0 slice marked BUILT+VERIFIED.
This commit is contained in:
Robert Allan James
2026-08-29 09:57:17 -04:00
parent aee1ecaa8f
commit 09857b7228
8 changed files with 157 additions and 17 deletions
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src/starkernel/capsule/capsule_mint.c
+4 -4
View File
@@ -16,7 +16,7 @@
#include "starkernel/user_identity_seed.h"
#include "starkernel/x509_ed25519.h"
#include "starkernel/ed25519.h"
#include "starkernel/virtio_rng.h"
#include "starkernel/rng.h"
#include "block_subsystem.h" /* compute_crc64() */
#include "blkio.h"
#include <string.h>
@@ -101,11 +101,11 @@ MintResult capsule_mint_identity(struct blkio_dev *dev, VM *issuer_vm,
/* issuer_vm==NULL is genesis mode (§F.21) -- no existing Zuse to
* require a cert from. */
if (issuer_vm && !issuer_vm->zuse_cert_installed) return MINT_ERR_NO_ZUSE_CERT;
if (!virtio_rng_ready()) return MINT_ERR_NO_ENTROPY;
if (!rng_ready()) return MINT_ERR_NO_ENTROPY;
/* Fresh identity keypair. */
uint8_t seed[32], pubkey[32];
if (virtio_rng_get_bytes(seed, sizeof(seed)) != 0) return MINT_ERR_NO_ENTROPY;
if (rng_get_bytes(seed, sizeof(seed)) != 0) return MINT_ERR_NO_ENTROPY;
ed25519_keygen(seed, pubkey);
if (out_pubkey) memcpy(out_pubkey, pubkey, 32);
if (out_seed) memcpy(out_seed, seed, 32);
@@ -114,7 +114,7 @@ MintResult capsule_mint_identity(struct blkio_dev *dev, VM *issuer_vm,
* the identity seed (§F.8 decision 3: "which physical drive," not
* "whose identity"). */
uint8_t drive_uuid[16];
if (virtio_rng_get_bytes(drive_uuid, sizeof(drive_uuid)) != 0)
if (rng_get_bytes(drive_uuid, sizeof(drive_uuid)) != 0)
return MINT_ERR_NO_ENTROPY;
uint32_t cert_devblock = 0;