[Core] Add new switch_rand() a compliant random number generator API. Add a unit-test.

* [Core] Add new switch_rand() a compliant random number generator API. Add a unit-test.

* Fall back to rand() on unsupported platforms compile time.

src/include/switch_utils.h

@@ -1514,6 +1514,11 @@ SWITCH_DECLARE(switch_status_t) switch_digest_string(const char *digest_name, ch
 SWITCH_DECLARE(char *) switch_must_strdup(const char *_s);
 SWITCH_DECLARE(const char *) switch_memory_usage_stream(switch_stream_handle_t *stream);
 
+/**
+/ Compliant random number generator. Returns the value between 0 and 0x7fff (RAND_MAX).
+**/
+SWITCH_DECLARE(int) switch_rand(void);
+
 SWITCH_END_EXTERN_C
 #endif
 /* For Emacs:

src/switch_utils.c

@@ -4811,6 +4811,63 @@ done:
 	return status;
 }
 
+SWITCH_DECLARE(int) switch_rand(void)
+{
+	uint32_t random_number = 0;
+#ifdef WIN32
+	BCRYPT_ALG_HANDLE hAlgorithm = NULL;
+	NTSTATUS status = BCryptOpenAlgorithmProvider(&hAlgorithm, BCRYPT_RNG_ALGORITHM, NULL, 0);
+
+	if (!BCRYPT_SUCCESS(status)) {
+		switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_ERROR, "BCryptOpenAlgorithmProvider failed with status %d\n", status);
+
+		return 1;
+	}
+
+	status = BCryptGenRandom(hAlgorithm, (PUCHAR)&random_number, sizeof(random_number), 0);
+	if (!BCRYPT_SUCCESS(status)) {
+		switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_ERROR, "BCryptGenRandom failed with status %d\n", status);
+
+		return 1;
+	}
+
+	BCryptCloseAlgorithmProvider(hAlgorithm, 0);
+
+	/* Make sure we return from 0 to RAND_MAX */
+	return (random_number & 0x7FFF);
+#elif defined(__unix__) || defined(__APPLE__)
+	int random_fd = open("/dev/urandom", O_RDONLY);
+	ssize_t result;
+	char error_msg[100];
+
+	if (random_fd == -1) {
+		strncpy(error_msg, strerror(errno), sizeof(error_msg) - 1);
+		error_msg[sizeof(error_msg) - 1] = '\0';
+
+		switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_ERROR, "open failed: %s\n", error_msg);
+
+		return 1;
+	}
+
+	result = read(random_fd, &random_number, sizeof(random_number));
+	if (result < 0) {
+		strncpy(error_msg, strerror(errno), sizeof(error_msg) - 1);
+		error_msg[sizeof(error_msg) - 1] = '\0';
+
+		switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_ERROR, "read failed: %s\n", error_msg);
+
+		return 1;
+	}
+	
+	close(random_fd);
+
+	/* Make sure we return from 0 to RAND_MAX */
+	return (random_number & 0x7FFF);
+#else
+	return rand();
+#endif
+}
+
 /* For Emacs:
  * Local Variables:
  * mode:c

tests/unit/switch_core.c

@@ -53,6 +53,27 @@ FST_CORE_BEGIN("./conf")
 		}
 		FST_TEARDOWN_END()
 
+		FST_TEST_BEGIN(test_switch_rand)
+		{
+			int i, c = 0;
+
+			switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_INFO, "\nLet's generate a few random numbers.\n");
+
+			for (i = 0; i < 10; i++) {
+				uint32_t rnd = switch_rand();
+
+				switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_INFO, "Random number %d\n", rnd);
+
+				if (rnd == 1) {
+					c++;
+				}
+			}
+
+			/* We do not expect all random numbers to be 1 all 10 times. That would mean we have an error OR we are lucky to have 10 random ones! */
+			fst_check(c < 10);
+		}
+		FST_TEST_END()
+
 		FST_TEST_BEGIN(test_switch_uint31_t_overflow)
 		{
 			switch_uint31_t x;