Add a basic sanity test for getentropy() if we are using it.
Change-Id: I78df8697814361993adafc342387a7d1804be371
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/62125
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
diff --git a/crypto/rand_extra/getentropy_test.cc b/crypto/rand_extra/getentropy_test.cc
new file mode 100644
index 0000000..d691913
--- /dev/null
+++ b/crypto/rand_extra/getentropy_test.cc
@@ -0,0 +1,65 @@
+/* Copyright (c) 2023, Google Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
+
+#if !defined(_DEFAULT_SOURCE)
+#define _DEFAULT_SOURCE // Needed for getentropy on musl and glibc
+#endif
+
+#include <openssl/rand.h>
+
+#include "../fipsmodule/rand/internal.h"
+
+#if defined(OPENSSL_RAND_GETENTROPY)
+
+#include <unistd.h>
+
+#include <sys/errno.h>
+
+#if defined(OPENSSL_MACOS) || defined(OPENSSL_FUCHSIA)
+#include <sys/random.h>
+#endif
+
+#include <gtest/gtest.h>
+
+#include <openssl/span.h>
+
+#include "../test/test_util.h"
+
+// This test is, strictly speaking, flaky, but we use large enough buffers
+// that the probability of failing when we should pass is negligible.
+
+TEST(GetEntropyTest, NotObviouslyBroken) {
+ static const uint8_t kZeros[256] = {0};
+
+ uint8_t buf1[256], buf2[256];
+
+ EXPECT_EQ(getentropy(buf1, sizeof(buf1)), 0);
+ EXPECT_EQ(getentropy(buf2, sizeof(buf2)), 0);
+ EXPECT_NE(Bytes(buf1), Bytes(buf2));
+ EXPECT_NE(Bytes(buf1), Bytes(kZeros));
+ EXPECT_NE(Bytes(buf2), Bytes(kZeros));
+ uint8_t buf3[256];
+ // Ensure that the implementation is not simply returning the memory unchanged.
+ memcpy(buf3, buf1, sizeof(buf3));
+ EXPECT_EQ(getentropy(buf1, sizeof(buf1)), 0);
+ EXPECT_NE(Bytes(buf1), Bytes(buf3));
+ errno = 0;
+ uint8_t toobig[257];
+ // getentropy should fail returning -1 and setting errno to EIO if you request
+ // more than 256 bytes of entropy. macOS's man page says EIO but it actually
+ // returns EINVAL, so we accept either.
+ EXPECT_EQ(getentropy(toobig, 257), -1);
+ EXPECT_TRUE(errno == EIO || errno == EINVAL);
+}
+#endif
