/** * (C) 2007-21 - ntop.org and contributors * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not see see * */ #include "random_numbers.h" // the following code offers an alterate pseudo random number generator // namely XORSHIFT128+ to use instead of C's rand() // its performance is on par with C's rand() // the state must be seeded in a way that it is not all zero, choose some // arbitrary defaults (in this case: taken from splitmix64) static rn_generator_state_t rn_current_state = { .a = 0x9E3779B97F4A7C15, .b = 0xBF58476D1CE4E5B9 }; // used for mixing the initializing seed static uint64_t splitmix64 (splitmix64_state_t *state) { uint64_t result = state->s; state->s = result + 0x9E3779B97F4A7C15; result = (result ^ (result >> 30)) * 0xBF58476D1CE4E5B9; result = (result ^ (result >> 27)) * 0x94D049BB133111EB; return result ^ (result >> 31); } int n2n_srand (uint64_t seed) { uint8_t i; splitmix64_state_t smstate = { seed }; rn_current_state.a = 0; rn_current_state.b = 0; rn_current_state.a = splitmix64 (&smstate); rn_current_state.b = splitmix64 (&smstate); // the following lines could be deleted as soon as it is formally prooved that // there is no seed leading to (a == b == 0). until then, just to be safe: if((rn_current_state.a == 0) && (rn_current_state.b == 0)) { rn_current_state.a = 0x9E3779B97F4A7C15; rn_current_state.b = 0xBF58476D1CE4E5B9; } // stabilize in unlikely case of weak state with only a few bits set for(i = 0; i < 32; i++) n2n_rand(); return 0; } // the following code of xorshift128p was taken from // https://en.wikipedia.org/wiki/Xorshift as of July, 2019 // and thus is considered public domain uint64_t n2n_rand (void) { uint64_t t = rn_current_state.a; uint64_t const s = rn_current_state.b; rn_current_state.a = s; t ^= t << 23; t ^= t >> 17; t ^= s ^ (s >> 26); rn_current_state.b = t; return t + s; } // the following code tries to gather some entropy from several sources // for use as seed. Note, that this code does not set the random generator // state yet, a call to n2n_srand (n2n_seed()) would do uint64_t n2n_seed (void) { uint64_t seed = 0; /* this could even go uninitialized */ uint64_t ret = 0; /* this could even go uninitialized */ size_t i; #ifdef SYS_getrandom int rc = -1; for(i = 0; (i < RND_RETRIES) && (rc != sizeof(seed)); i++) { rc = syscall (SYS_getrandom, &seed, sizeof(seed), GRND_NONBLOCK); // if successful, rc should contain the requested number of random bytes if(rc != sizeof(seed)) { if (errno != EAGAIN) { traceEvent(TRACE_ERROR, "n2n_seed faced error errno=%u from getrandom syscall.", errno); break; } } } // if we still see an EAGAIN error here, we must have run out of retries if(errno == EAGAIN) { traceEvent(TRACE_ERROR, "n2n_seed saw getrandom syscall indicate not being able to provide enough entropy yet."); } #endif // as we want randomness, it does no harm to add up even uninitialized values or // erroneously arbitrary values returned from the syscall for the first time ret += seed; // __RDRND__ is set only if architecturual feature is set, e.g. compiled with -march=native #ifdef __RDRND__ for(i = 0; i < RND_RETRIES; i++) { if(_rdrand64_step((unsigned long long*)&seed)) { // success! // from now on, we keep this inside the loop because in case of failure // and with unchanged values, we do not want to double the previous value ret += seed; break; } // continue loop to try again otherwise } if(i == RND_RETRIES) { traceEvent(TRACE_ERROR, "n2n_seed was not able to get a hardware generated random number from RDRND."); } #endif // __RDSEED__ ist set only if architecturual feature is set, e.g. compile with -march=native #ifdef __RDSEED__ for(i = 0; i < RND_RETRIES; i++) { if(_rdseed64_step((unsigned long long*)&seed)) { // success! ret += seed; break; } // continue loop to try again otherwise } if(i == RND_RETRIES) { traceEvent(TRACE_ERROR, "n2n_seed was not able to get a hardware generated random number from RDSEED."); } #endif #ifdef WIN32 HCRYPTPROV crypto_provider; CryptAcquireContext (&crypto_provider, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT); CryptGenRandom (crypto_provider, 8, &seed); CryptReleaseContext (crypto_provider, 0); ret += seed; #endif seed = time(NULL); /* UTC in seconds */ ret += seed; seed = clock(); /* ticks since program start */ seed *= 18444244737; ret += seed; return ret; } // an integer squrare root approximation // from https://stackoverflow.com/a/1100591 static int ftbl[33] = { 0, 1, 1, 2, 2, 4, 5, 8, 11, 16, 22, 32, 45, 64, 90, 128, 181 ,256 ,362, 512, 724, 1024, 1448, 2048, 2896, 4096, 5792, 8192, 11585, 16384, 23170, 32768, 46340 }; static int ftbl2[32] = { 32768, 33276, 33776, 34269, 34755, 35235, 35708, 36174, 36635, 37090, 37540, 37984, 38423, 38858, 39287, 39712, 40132, 40548, 40960, 41367, 41771, 42170, 42566, 42959, 43347, 43733, 44115, 44493, 44869, 45241, 45611, 45977 }; static int i_sqrt (int val) { int cnt = 0; int t = val; while(t) { cnt++; t>>=1; } if(6 >= cnt) t = (val << (6-cnt)); else t = (val >> (cnt-6)); return (ftbl[cnt] * ftbl2[t & 31]) >> 15; } static int32_t int_sqrt (int val) { int ret; ret = i_sqrt (val); ret += i_sqrt (val - ret * ret) / 16; return ret; } // returns a random number from [0, max_n] with higher probability towards the borders uint32_t n2n_rand_sqr (uint32_t max_n) { uint32_t raw_max = 0; uint32_t raw_rnd = 0; int32_t ret = 0; raw_max = (max_n+2) * (max_n+2); raw_rnd = n2n_rand() % (raw_max); ret = int_sqrt(raw_rnd) / 2; ret = (raw_rnd & 1) ? ret : -ret; ret = max_n / 2 + ret; if(ret < 0) ret = 0; if (ret > max_n) ret = max_n; return ret; }