Default POSIX/Windows RNG should be treated as user-set RNG.
The default RNG functions on POSIX and windows are secure, and
should be used as if the user had set an RNG. Also, don't set an
RNG at all on other platforms.
diff --git a/platform-specific.inc b/platform-specific.inc
index 207ac8b..9d42534 100644
--- a/platform-specific.inc
+++ b/platform-specific.inc
@@ -120,6 +120,7 @@
CryptReleaseContext(prov, 0);
return 1;
}
+#define default_RNG_defined 1
#elif defined(unix) || defined(__linux__) || defined(__unix__) || defined(__unix) || \
(defined(__APPLE__) && defined(__MACH__)) || defined(uECC_POSIX)
@@ -157,12 +158,7 @@
close(fd);
return 1;
}
-
-#else /* Some other platform */
-
-static int default_RNG(uint8_t *dest, unsigned size) {
- return 0;
-}
+#define default_RNG_defined 1
#endif /* platform */
diff --git a/uECC.c b/uECC.c
index e5336a0..a3bb418 100644
--- a/uECC.c
+++ b/uECC.c
@@ -64,7 +64,11 @@
#include "asm_arm_small.inc"
#endif
+#if default_RNG_defined
static uECC_RNG_Function g_rng_function = &default_RNG;
+#else
+static uECC_RNG_Function g_rng_function = 0;
+#endif
void uECC_set_rng(uECC_RNG_Function rng_function) {
g_rng_function = rng_function;
@@ -827,7 +831,7 @@
static cmpresult_t generate_random_int(uECC_word_t *random,
wordcount_t num_words,
const wordcount_t num_bits) {
- if (!g_rng_function((uint8_t *)random, num_words * uECC_WORD_SIZE)) {
+ if (!g_rng_function || !g_rng_function((uint8_t *)random, num_words * uECC_WORD_SIZE)) {
return 0;
}
if (num_words * uECC_WORD_SIZE * 8 > num_bits) {
@@ -887,7 +891,7 @@
/* If an RNG function was specified, try to get a random initial Z value to improve
protection against side-channel attacks. */
- if (g_rng_function != &default_RNG) {
+ if (g_rng_function) {
for (tries = 0; tries < MAX_TRIES; ++tries) {
if (!generate_random_int(p2[carry], curve->num_words, curve->num_bytes * 8)) {
return 0;
@@ -999,7 +1003,7 @@
}
/* Attempt to get a random number to prevent side channel analysis of k. */
- if (g_rng_function == &default_RNG) {
+ if (!g_rng_function) {
vli_clear(tmp, curve->num_n_words);
tmp[0] = 1;
} else {
