From 9f554a72b01705ebf6be66143c5e69b09b3c1372 Mon Sep 17 00:00:00 2001
From: EuAndreh <eu@euandre.org>
Date: Fri, 28 Jan 2022 07:33:30 -0300
Subject: Init project: copy files and skeletons from others

---
 src/random.c | 122 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 122 insertions(+)
 create mode 100644 src/random.c

(limited to 'src/random.c')

diff --git a/src/random.c b/src/random.c
new file mode 100644
index 0000000..d92d533
--- /dev/null
+++ b/src/random.c
@@ -0,0 +1,122 @@
+#include "config.h"
+
+#include <assert.h>
+#include <errno.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+
+#include "logerr.h"
+#include "random.h"
+
+#ifdef TEST
+#include "testing.h"
+#endif
+
+
+int
+urandom_bytes(const size_t n, uint8_t (*const addr)[]) {
+	int rc = 0;
+
+	FILE *f = NULL;
+
+	f = fopen("/dev/urandom", "r");
+	if (!f) {
+		logerr("fopen(\"/dev/urandom\", \"r\"): %s\n", strerror(errno));
+		rc = -1;
+		goto out;
+	}
+
+	const size_t read_count = fread(addr, 1, n, f);
+	if (ferror(f)) {
+		logerr("fread(addr, 1, n, f): %s\n", strerror(errno));
+		rc = -1;
+		goto out;
+	}
+	assert(read_count == n);
+
+out:
+	if (f) {
+		if (fclose(f)) {
+			logerr("fclose(f): %s\n", strerror(errno));
+			rc = -1;
+		}
+	}
+	return rc;
+}
+
+#ifdef TEST
+static int
+test_urandom_bytes(void) {
+	int rc = 0;
+
+	test_start("urandom_bytes()");
+
+	{
+		testing("we get to pick the size that comes out");
+
+		const size_t LEN = 256;
+		uint8_t arr[256 /* LEN */] = { 0 };
+
+		for (size_t n = 0; n < LEN; n++) {
+			if (urandom_bytes(n, &arr)) {
+				logerr("urandom_bytes(n, &arr);\n");
+				rc = -1;
+				goto out;
+			}
+			for (size_t i = n; i < LEN; i++) {
+				assert(arr[i] == 0);
+			}
+		}
+
+		test_ok();
+	}
+
+	{
+		testing("we always get a new value as a result");
+
+		const size_t LEN = 64;
+		uint8_t arr1[64 /* LEN */] = { 0 };
+		uint8_t arr2[64 /* LEN */] = { 0 };
+
+		if (urandom_bytes(LEN, &arr1)) {
+			logerr("urandom_bytes(LEN, &arr1);\n");
+			rc = -1;
+			goto out;
+		}
+
+		const size_t attempts = 10;
+		for (size_t n = 0; n < attempts; n++) {
+			if (urandom_bytes(LEN, &arr2)) {
+				logerr("urandom_bytes(LEN, &arr2);\n");
+				rc = -1;
+				goto out;
+			}
+			assert(memcmp(arr1, arr2, LEN) != 0);
+		}
+
+		test_ok();
+	}
+
+out:
+	return rc;
+}
+#endif
+
+
+#ifdef TEST
+int
+main(void) {
+	int rc = 0;
+
+	if (test_urandom_bytes()) {
+		logerr("test_urandom_bytes();\n");
+		rc = -1;
+		goto out;
+	}
+
+out:
+	return !!rc;
+}
+#endif
-- 
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