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// FIXME: This is mostlikely incredibly inefficent and insecure.
#include <assert.h>
#include <crypto/ChaCha20/chacha20.h>
#include <crypto/SHA1/sha1.h>
#include <crypto/xoshiro256plusplus/xoshiro256plusplus.h>
#include <fcntl.h>
#include <fs/devfs.h>
#include <fs/vfs.h>
#include <random.h>
#include <stddef.h>
#include <string.h>
#define HASH_CTX SHA1_CTX
#define HASH_LEN SHA1_LEN
u32 internal_chacha_block[16] = {
// Constant ascii values of "expand 32-byte k"
0x61707865,
0x3320646e,
0x79622d32,
0x6b206574,
// The unique key
0x00000000,
0x00000000,
0x00000000,
0x00000000,
0x00000000,
0x00000000,
0x00000000,
0x00000000,
// Block counter
0x00000000,
// Nonce
0x00000000,
0x00000000,
};
void mix_chacha(void) {
u8 rand_data[BLOCK_SIZE];
get_random((BYTEPTR)rand_data, BLOCK_SIZE);
memcpy(internal_chacha_block + KEY, rand_data, KEY_SIZE);
memcpy(internal_chacha_block + NONCE, rand_data + KEY_SIZE, NONCE_SIZE);
internal_chacha_block[COUNT] = 0;
}
void get_fast_insecure_random(u8 *buffer, u64 len) {
static u8 is_fast_random_seeded = 0;
if (!is_fast_random_seeded) {
uint64_t seed[4];
get_random((u8 *)&seed, sizeof(seed));
seed_xoshiro_256_pp(seed);
is_fast_random_seeded = 1;
}
for (; len >= 8; len -= 8, buffer += 8) {
*((uint64_t *)buffer) = xoshiro_256_pp();
}
for (; len > 0; len--, buffer++) {
*((uint8_t *)buffer) = xoshiro_256_pp() & 0xFF;
}
}
void get_random(u8 *buffer, u64 len) {
u8 rand_data[BLOCK_SIZE];
for (; len > 0;) {
if (COUNT_MAX - 1 == internal_chacha_block[COUNT]) {
// The current block has used up all the 2^32 counts. If the
// key and/or the nonce are not changed and the count
// overflows back to zero then the random values would
// repeate. This is of course not desiered behaviour. The
// solution is to create a new nonce and key using the
// already established chacha block.
internal_chacha_block[COUNT]++;
mix_chacha();
}
u32 read_len = (BLOCK_SIZE < len) ? (BLOCK_SIZE) : len;
chacha_block((u32 *)rand_data, internal_chacha_block);
internal_chacha_block[COUNT]++;
memcpy(buffer, rand_data, read_len);
buffer += read_len;
len -= read_len;
}
}
HASH_CTX hash_pool;
u32 hash_pool_size = 0;
void add_hash_pool(void) {
u8 new_chacha_key[KEY_SIZE];
get_random(new_chacha_key, KEY_SIZE);
u8 hash_buffer[HASH_LEN];
SHA1_Final(&hash_pool, hash_buffer);
for (size_t i = 0; i < HASH_LEN; i++) {
new_chacha_key[i % KEY_SIZE] ^= hash_buffer[i];
}
SHA1_Init(&hash_pool);
SHA1_Update(&hash_pool, hash_buffer, HASH_LEN);
u8 block[BLOCK_SIZE];
get_random(block, BLOCK_SIZE);
SHA1_Update(&hash_pool, block, BLOCK_SIZE);
memcpy(internal_chacha_block + KEY, new_chacha_key, KEY_SIZE);
mix_chacha();
}
void add_entropy(u8 *buffer, size_t size) {
SHA1_Update(&hash_pool, buffer, size);
hash_pool_size += size;
if (hash_pool_size >= HASH_LEN * 2) {
add_hash_pool();
}
}
void setup_random(void) {
SHA1_Init(&hash_pool);
BYTE seed[1024];
int rand_fd = vfs_open("/etc/seed", O_RDWR, 0);
if (0 > rand_fd) {
klog(LOG_WARN, "/etc/seed not found");
return;
}
size_t offset = 0;
for (int rc; (rc = vfs_pread(rand_fd, seed, 1024, offset)); offset += rc) {
if (0 > rc) {
klog(LOG_WARN, "/etc/seed read error");
break;
}
add_entropy(seed, rc);
}
add_hash_pool();
// Update the /etc/seed file to ensure we get a new state upon next
// boot.
get_random(seed, 1024);
vfs_pwrite(rand_fd, seed, 1024, 0);
vfs_close(rand_fd);
}
int random_write(BYTEPTR buffer, u64 offset, u64 len, vfs_fd_t *fd) {
(void)offset;
(void)fd;
add_entropy(buffer, len);
return len; // add_entropy() never fails to recieve (len) amount of data.
}
int random_read(BYTEPTR buffer, u64 offset, u64 len, vfs_fd_t *fd) {
(void)offset;
(void)fd;
get_random(buffer, len);
return len; // get_random() never fails to give "len" amount of data.
}
void add_random_devices(void) {
devfs_add_file("/random", random_read, random_write, NULL, always_has_data,
always_can_write, FS_TYPE_CHAR_DEVICE);
devfs_add_file("/urandom", random_read, random_write, NULL, always_has_data,
always_can_write, FS_TYPE_CHAR_DEVICE);
}
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