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Introduce more randomness

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- Use C++ random generator instead of old and broken rand()
- Randomize string length to piss off stupid detectors
This commit is contained in:
topjohnwu
2019-07-14 17:41:51 -07:00
parent 188ea2644a
commit 41045b62dc
4 changed files with 35 additions and 29 deletions
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3
native/jni/utils/include/misc.h
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@@ -10,7 +10,6 @@ extern "C" {
unsigned get_shell_uid();
int fork_dont_care();
int fork_no_zombie();
void gen_rand_str(char *buf, int len);
int strend(const char *s1, const char *s2);
char *rtrim(char *str);
void init_argv0(int argc, char **argv);
@@ -24,6 +23,8 @@ int parse_int(const char *s);
#include <functional>
#include <string_view>
void gen_rand_str(char *buf, int len, bool varlen = true);
#define str_contains(s, ss) ((ss) != nullptr && (s).find(ss) != std::string::npos)
#define str_starts(s, ss) ((ss) != nullptr && (s).compare(0, strlen(ss), ss) == 0)

39
native/jni/utils/misc.cpp
View File

@@ -1,6 +1,10 @@
/* misc.cpp - Store all functions that are unable to be catagorized clearly
*/
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/prctl.h>
#include <sys/sysmacros.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
@@ -8,10 +12,7 @@
#include <pwd.h>
#include <unistd.h>
#include <syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/prctl.h>
#include <sys/sysmacros.h>
#include <random>
#include <logging.h>
#include <utils.h>
@@ -49,17 +50,27 @@ int fork_no_zombie() {
return 0;
}
static bool rand_init = false;
void gen_rand_str(char *buf, int len) {
constexpr const char base[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
if (!rand_init) {
srand(time(nullptr));
rand_init = true;
constexpr char ALPHANUM[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
static bool seeded = false;
static std::mt19937 gen;
static std::uniform_int_distribution<int> dist(0, sizeof(ALPHANUM) - 1);
void gen_rand_str(char *buf, int len, bool varlen) {
if (!seeded) {
if (access("/dev/urandom", F_OK) == 0) {
std::random_device rdev;
gen.seed(rdev());
} else {
// In magiskinit
gen.seed(time(nullptr));
}
seeded = true;
}
for (int i = 0; i < len - 1; ++i) {
buf[i] = base[rand() % (sizeof(base) - 1)];
if (varlen) {
std::uniform_int_distribution<int> len_dist(len / 2, len);
len = len_dist(gen);
}
for (int i = 0; i < len - 1; ++i)
buf[i] = ALPHANUM[dist(gen)];
buf[len - 1] = '\0';
}