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Directly use getrandom system call if possible

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topjohnwu 2022-02-16 23:57:28 -08:00
parent afa771a980
commit e7c82f20e3
1 changed files with 12 additions and 8 deletions
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20
native/jni/utils/misc.cpp
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@ -35,17 +35,21 @@ int fork_no_orphan() {
int gen_rand_str(char *buf, int len, bool varlen) {
constexpr char ALPHANUM[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
static std::mt19937 gen([]{
if (access("/dev/urandom", F_OK) != 0)
mknod("/dev/urandom", 0600 | S_IFCHR, makedev(1, 9));
int fd = xopen("/dev/urandom", O_RDONLY | O_CLOEXEC);
unsigned seed;
xxread(fd, &seed, sizeof(seed));
static mt19937 gen([]{
mt19937::result_type seed;
if (syscall(__NR_getrandom, &seed, sizeof(seed), 0) < 0) {
// This can happen if device is running a too low Linux version
if (access("/dev/urandom", F_OK) != 0)
mknod("/dev/urandom", 0600 | S_IFCHR, makedev(1, 9));
int fd = xopen("/dev/urandom", O_RDONLY | O_CLOEXEC);
xxread(fd, &seed, sizeof(seed));
close(fd);
}
return seed;
}());
std::uniform_int_distribution<int> dist(0, sizeof(ALPHANUM) - 2);
uniform_int_distribution<int> dist(0, sizeof(ALPHANUM) - 2);
if (varlen) {
std::uniform_int_distribution<int> len_dist(len / 2, len);
uniform_int_distribution<int> len_dist(len / 2, len);
len = len_dist(gen);
}
for (int i = 0; i < len - 1; ++i)