From: Timo Sirainen <timo.sirainen@open-xchange.com>
Date: Sun, 29 Jan 2023 10:54:30 +0000 (+0200)
Subject: lib: Add unit test for random_fill()
X-Git-Tag: 2.4.0~3023
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=dff8b216cdd23c53ef0387aafbb97b7df16eb3d5;p=thirdparty%2Fdovecot%2Fcore.git

lib: Add unit test for random_fill()
---

diff --git a/src/lib/randgen.c b/src/lib/randgen.c
index f6b2da9c99..54d6800dac 100644
--- a/src/lib/randgen.c
+++ b/src/lib/randgen.c
@@ -61,14 +61,6 @@ static int init_refcount = 0;
 static int urandom_fd = -1;
 
 #if defined(USE_GETRANDOM) || defined(USE_RANDOM_DEV)
-/* Use a small buffer when reading randomness. This is mainly to make small
-   random reads more efficient, such as i_rand*(). When reading larger amount
-   of randomness this buffer is bypassed.
-
-   There doesn't seem to be a big difference in Linux system CPU usage when
-   buffer size is above 16 bytes. Double it just to be safe. Avoid it being
-   too large anyway so we don't unnecessarily waste CPU and memory. */
-#define RANDOM_READ_BUFFER_SIZE 32
 static unsigned char random_next[RANDOM_READ_BUFFER_SIZE];
 static size_t random_next_pos = 0;
 static size_t random_next_size = 0;
diff --git a/src/lib/randgen.h b/src/lib/randgen.h
index d532880fb3..cab234d984 100644
--- a/src/lib/randgen.h
+++ b/src/lib/randgen.h
@@ -14,4 +14,15 @@ void random_deinit(void);
 int rand_get_last_seed(unsigned int *seed_r);
 #endif
 
+/* Internal for unit test:
+
+   Use a small buffer when reading randomness. This is mainly to make small
+   random reads more efficient, such as i_rand*(). When reading larger amount
+   of randomness this buffer is bypassed.
+
+   There doesn't seem to be a big difference in Linux system CPU usage when
+   buffer size is above 16 bytes. Double it just to be safe. Avoid it being
+   too large anyway so we don't unnecessarily waste CPU and memory. */
+#define RANDOM_READ_BUFFER_SIZE 32
+
 #endif
diff --git a/src/lib/test-random.c b/src/lib/test-random.c
index 6c83ff6b88..cb30de4c04 100644
--- a/src/lib/test-random.c
+++ b/src/lib/test-random.c
@@ -1,6 +1,7 @@
 /* Copyright (c) 2018 Dovecot authors, see the included COPYING file */
 
 #include "test-lib.h"
+#include "hash.h"
 #include "stats-dist.h"
 #include "randgen.h"
 #include <math.h>
@@ -43,10 +44,36 @@ static void test_random_limits(void)
 	test_end();
 }
 
+static void test_random_fill(void)
+{
+	test_begin("random_fill()");
+	unsigned int hash = 0;
+	for (unsigned int i = 0; i <= (2*RANDOM_READ_BUFFER_SIZE)+1; i++) {
+		/* Rely on valgrind to verify that there are no uninitialized
+		   bytes, so don't use i_malloc(). */
+		unsigned char *buf = malloc(i);
+		random_fill(buf, i);
+		hash ^= mem_hash(buf, i);
+		free(buf);
+	}
+	/* Try also with some random small numbers */
+	for (unsigned int i = 0; i < 100; i++) {
+		/* 32 = RANDOM_READ_BUFFER_SIZE */
+		unsigned int size = i_rand_minmax(1, RANDOM_READ_BUFFER_SIZE);
+		unsigned char *buf = malloc(size);
+		random_fill(buf, size);
+		hash ^= mem_hash(buf, size);
+		free(buf);
+	}
+	test_out_reason("hash", TRUE, dec2str(hash));
+	test_end();
+}
+
 void test_random(void)
 {
 	test_random_median();
 	test_random_limits();
+	test_random_fill();
 }
 
 enum fatal_test_state fatal_random(unsigned int stage)