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#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <syscall.h>
#include "frida-gum.h"
#include "debug.h"
#include "util.h"
#define DEFAULT_MMAP_MIN_ADDR (32UL << 10)
#define MAX_MEMFD_SIZE (64UL << 10)
extern struct cmp_map *__afl_cmp_map;
static GArray *cmplog_ranges = NULL;
static GHashTable * hash = NULL;
static int memfd = -1;
static size_t memfd_size = 0;
static u8 scratch[MAX_MEMFD_SIZE] = {0};
static gboolean cmplog_range(const GumRangeDetails *details,
gpointer user_data) {
GArray * cmplog_ranges = (GArray *)user_data;
GumMemoryRange range = *details->range;
g_array_append_val(cmplog_ranges, range);
return TRUE;
}
static gint cmplog_sort(gconstpointer a, gconstpointer b) {
return ((GumMemoryRange *)b)->base_address -
((GumMemoryRange *)a)->base_address;
}
static void cmplog_get_ranges(void) {
OKF("CMPLOG - Collecting ranges");
cmplog_ranges =
g_array_sized_new(false, false, sizeof(GumMemoryRange), 100);
gum_process_enumerate_ranges(GUM_PAGE_READ, cmplog_range, cmplog_ranges);
g_array_sort(cmplog_ranges, cmplog_sort);
for (guint i = 0; i < cmplog_ranges->len; i++) {
GumMemoryRange *range = &g_array_index(cmplog_ranges, GumMemoryRange, i);
}
g_array_free(cmplog_ranges, TRUE);
}
void cmplog_init(void) {
if (__afl_cmp_map != NULL) { OKF("CMPLOG mode enabled"); }
cmplog_get_ranges();
for (guint i = 0; i < cmplog_ranges->len; i++) {
GumMemoryRange *range = &g_array_index(cmplog_ranges, GumMemoryRange, i);
OKF("CMPLOG Range - %3u: 0x%016" G_GINT64_MODIFIER
"X - 0x%016" G_GINT64_MODIFIER "X",
i, range->base_address, range->base_address + range->size);
}
memfd = syscall(__NR_memfd_create, "cmplog_memfd", 0);
if (memfd < 0) {
FATAL("Failed to create_memfd, errno: %d", errno);
}
hash = g_hash_table_new (g_direct_hash, g_direct_equal);
if (hash == NULL) {
FATAL("Failed to g_hash_table_new, errno: %d", errno);
}
}
static gboolean cmplog_contains(GumAddress inner_base, GumAddress inner_limit,
GumAddress outer_base, GumAddress outer_limit) {
return (inner_base >= outer_base && inner_limit <= outer_limit);
}
gboolean cmplog_test_addr(guint64 addr, size_t size) {
if (g_hash_table_contains(hash, (gpointer)addr)) { return true; }
if (memfd_size > MAX_MEMFD_SIZE) {
if (lseek(memfd, 0, SEEK_SET) < 0) {
FATAL("CMPLOG - Failed lseek, errno: %d", errno);
}
}
/*
* Our address map can change (e.g. stack growth), use write as a fallback to
* validate our address.
*/
ssize_t written = syscall(SYS_write, memfd, (void *)addr, size);
if (written < 0 && errno != EFAULT && errno != 0) {
FATAL("CMPLOG - Failed __NR_write, errno: %d", errno);
}
/*
* If the write succeeds, then the buffer must be valid otherwise it would
* return EFAULT
*/
if (written > 0) { memfd_size += written; }
if ((size_t)written == size) {
if (!g_hash_table_add (hash, (gpointer)addr)) {
FATAL("Failed - g_hash_table_add");
}
return true;
}
return false;
}
gboolean cmplog_is_readable(guint64 addr, size_t size) {
if (cmplog_ranges == NULL) FATAL("CMPLOG not initialized");
/*
* The Linux kernel prevents mmap from allocating from the very bottom of the
* address space to mitigate NULL pointer dereference attacks. The exact size
* is set by sysctl by setting mmap_min_addr and 64k is suggested on most
* platforms with 32k on ARM systems. We therefore fail fast if the address
* is lower than this. This should avoid some overhead when functions are
* called where one of the parameters is a size, or a some other small value.
*/
if (addr < DEFAULT_MMAP_MIN_ADDR) { return false; }
/* Check our addres/length don't wrap around */
if (SIZE_MAX - addr < size) { return false; }
GumAddress inner_base = addr;
GumAddress inner_limit = inner_base + size;
for (guint i = 0; i < cmplog_ranges->len; i++) {
GumMemoryRange *range = &g_array_index(cmplog_ranges, GumMemoryRange, i);
GumAddress outer_base = range->base_address;
GumAddress outer_limit = outer_base + range->size;
if (cmplog_contains(inner_base, inner_limit, outer_base, outer_limit))
return true;
}
if (cmplog_test_addr(addr, size)) { return true; }
return false;
}
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