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Code to get random bytes in C, cross-platform

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Kovid Goyal 2020-12-31 11:26:22 +05:30
parent 72d193e852
commit 3c77290c2c
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GPG Key ID: 06BC317B515ACE7C
2 changed files with 37 additions and 0 deletions
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35
kitty/cross-platform-random.h Normal file
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@ -0,0 +1,35 @@
/*
* Copyright (C) 2020 Kovid Goyal <kovid at kovidgoyal.net>
*
* Distributed under terms of the GPL3 license.
*/
#pragma once
#include <stdlib.h>
#include <stdbool.h>
#if __linux__
#include <sys/random.h>
#include <errno.h>
static inline bool
secure_random_bytes(void *buf, size_t nbytes) {
unsigned char* p = buf;
ssize_t left = nbytes;
while(1) {
ssize_t n = getrandom(p, left, 0);
if (n >= left) return true;
if (n < 0) {
if (errno != EINTR) return false; // should never happen but if it does, we fail without any feedback
continue;
}
left -= n; p += n;
}
}
#else
static inline bool
secure_random_bytes(void *buf, size_t nbytes) {
arc4random_buf(buf, nbytes);
return true;
}
#endif

2
kitty/disk-cache.c
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@ -10,6 +10,7 @@
#include "disk-cache.h"
#include "uthash.h"
#include "loop-utils.h"
#include "cross-platform-random.h"
#include <stdlib.h>
#include <sys/stat.h>
#include <fcntl.h>
@ -186,6 +187,7 @@ add_to_disk_cache(PyObject *self_, const void *key, size_t key_sz, const uint8_t
if (s == NULL) {
s = calloc(1, sizeof(CacheEntry));
if (!s) { PyErr_NoMemory(); goto end; }
if (!secure_random_bytes(s->encryption_key, sizeof(s->encryption_key))) { free(s); PyErr_SetFromErrno(PyExc_OSError); goto end; }
s->hash_key = malloc(key_sz);
if (!s->hash_key) { free(s); PyErr_NoMemory(); goto end; }
s->hash_keylen = key_sz;