qemu-spoof/src/spoof-core.c

/*
 * spoof-core.c — seed/config acquisition + the deterministic derivation engine
 * + the policy knobs (hv mode / WAET / vmgenid). See spoof-core.h, spoof.h.
 */
#include "qemu/osdep.h"
#include "qemu/cutils.h"       /* pstrcpy */
#include "hw/misc/spoof.h"
#include "hw/misc/spoof-core.h"
#include "hw/core/boards.h"     /* current_machine */
#include "qom/object.h"

const char SPOOF_A36[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const char SPOOF_LET[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const char SPOOF_DIG[] = "0123456789";

/* ---- config: machine property first, env var as a test fallback ----------- */
static char g_seed[256];
static bool g_ready, g_enabled;
static char g_hv[16], g_waet[16], g_vgid[16], g_pvp[16];

static void read_prop(const char *prop, const char *env, char *out, size_t n)
{
    out[0] = '\0';
    if (current_machine && object_property_find(OBJECT(current_machine), prop)) {
        char *v = object_property_get_str(OBJECT(current_machine), prop, NULL);
        if (v) { pstrcpy(out, n, v); g_free(v); }
    }
    if (!out[0]) {
        const char *e = getenv(env);
        if (e) { pstrcpy(out, n, e); }
    }
}

static void config_load(void)
{
    if (g_ready) {
        return;
    }
    read_prop("spoof-seed",    "QEMU_SPOOF_SEED",    g_seed, sizeof(g_seed));
    read_prop("spoof-hv",      "QEMU_SPOOF_HV",      g_hv,   sizeof(g_hv));
    read_prop("spoof-waet",    "QEMU_SPOOF_WAET",    g_waet, sizeof(g_waet));
    read_prop("spoof-vmgenid", "QEMU_SPOOF_VMGENID", g_vgid, sizeof(g_vgid));
    read_prop("spoof-pvpanic", "QEMU_SPOOF_PVPANIC", g_pvp,  sizeof(g_pvp));
    g_enabled = g_seed[0] != '\0';
    g_ready = true;
}

bool spoof_on(void)      { config_load(); return g_enabled; }
bool spoof_enabled(void) { return spoof_on(); }

/* ---- deterministic derivation: fnv1a(seed|key) -> splitmix64 -------------- */
static uint64_t fnv1a(const char *s)
{
    uint64_t h = 1469598103934665603ULL;
    for (; *s; s++) { h ^= (uint8_t)*s; h *= 1099511628211ULL; }
    return h;
}
static uint64_t mix(uint64_t x)
{
    x += 0x9E3779B97F4A7C15ULL;
    x = (x ^ (x >> 30)) * 0xBF58476D1CE4E5B9ULL;
    x = (x ^ (x >> 27)) * 0x94D049BB133111EBULL;
    return x ^ (x >> 31);
}
uint64_t spoof_field(const char *key)
{
    config_load();
    return mix(fnv1a(g_seed) ^ (fnv1a(key) * 0x100000001B3ULL));
}
uint64_t spoof_field_n(const char *key, unsigned i)
{
    char k[96];
    snprintf(k, sizeof(k), "%s#%u", key, i);
    return spoof_field(k);
}
const char *spoof_pick(const char *key, const char *const *arr, size_t n)
{
    return arr[spoof_field(key) % n];
}
void spoof_gen(const char *key, const char *cs, int len, char *out)
{
    size_t m = strlen(cs);
    for (int i = 0; i < len; i++) {
        out[i] = cs[spoof_field_n(key, (unsigned)i) % m];
    }
    out[len] = '\0';
}
/* one cpu-vendor draw anchors BOTH the CPU signature and the chipset/PCI vendor. */
int spoof_anchor_vendor(void)
{
    return (int)(spoof_field("anchor.cpu") & 1);   /* 0 Intel, 1 AMD */
}

/* ---- policy knobs --------------------------------------------------------- */
SpoofHvMode spoof_hv_mode(void)
{
    config_load();
    if (!strcmp(g_hv, "hidden")) return SPOOF_HV_HIDDEN;
    if (!strcmp(g_hv, "hyperv")) return SPOOF_HV_HYPERV;
    if (!strcmp(g_hv, "off"))    return SPOOF_HV_OFF;
    return g_enabled ? SPOOF_HV_HYPERV : SPOOF_HV_OFF;   /* seeded default = hyperv */
}
bool spoof_waet_drop(void)
{
    config_load();
    if (!strcmp(g_waet, "on"))  return true;
    if (!strcmp(g_waet, "off")) return false;
    return g_enabled;                                    /* seeded default = drop */
}
bool spoof_pvpanic_hide(void)
{
    config_load();
    if (!strcmp(g_pvp, "on"))  return true;
    if (!strcmp(g_pvp, "off")) return false;
    return g_enabled;                                    /* seeded default = hide pvpanic */
}
SpoofVgidPolicy spoof_vmgenid_policy(void)
{
    config_load();
    if (!strcmp(g_vgid, "hide")) return SPOOF_VGID_HIDE;
    if (!strcmp(g_vgid, "mask")) return SPOOF_VGID_MASK;
    if (!strcmp(g_vgid, "keep")) return SPOOF_VGID_KEEP;
    switch (spoof_hv_mode()) {                            /* default tracks hv mode */
    case SPOOF_HV_HIDDEN: return SPOOF_VGID_HIDE;
    case SPOOF_HV_HYPERV: return SPOOF_VGID_MASK;
    default:              return SPOOF_VGID_KEEP;
    }
}