test-rand: return failure on not enough data, allow parent

The test-rand RNG was returning success when it had some but insufficient data.
Now, it returns failure and doesn't advance the data pointer.

The test-rand RNG was failing when a parent was specified.  This case is now
ignored.

Fixes #16785

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16905)

(cherry picked from commit d4dfd983e32b32b633aaa9edec422cc30419c6f7)

3 files changed, 63 insertions, 2 deletions

diff --git a/test/build.info b/test/build.info
index 2e209b45c7..1e4205ddb3 100644
--- a/test/build.info
+++ b/test/build.info
@@ -62,7 +62,7 @@ IF[{- !$disabled{tests} -}]
           context_internal_test aesgcmtest params_test evp_pkey_dparams_test \
           keymgmt_internal_test hexstr_test provider_status_test defltfips_test \
           bio_readbuffer_test user_property_test pkcs7_test upcallstest \
-          provfetchtest prov_config_test
+          provfetchtest prov_config_test rand_test
 
   IF[{- !$disabled{'deprecated-3.0'} -}]
     PROGRAMS{noinst}=enginetest
@@ -84,6 +84,10 @@ IF[{- !$disabled{tests} -}]
   INCLUDE[sanitytest]=../include ../apps/include
   DEPEND[sanitytest]=../libcrypto libtestutil.a
 
+  SOURCE[rand_test]=rand_test.c
+  INCLUDE[rand_test]=../include ../apps/include
+  DEPEND[rand_test]=../libcrypto libtestutil.a
+
   SOURCE[rsa_complex]=rsa_complex.c
   INCLUDE[rsa_complex]=../include ../apps/include
 
diff --git a/test/rand_test.c b/test/rand_test.c
new file mode 100644
index 0000000000..864f3cdb51
--- /dev/null
+++ b/test/rand_test.c
@@ -0,0 +1,56 @@
+/*
+ * Copyright 2021 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the >License>).  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#include <openssl/evp.h>
+#include <openssl/rand.h>
+#include <openssl/bio.h>
+#include <openssl/core_names.h>
+#include "testutil.h"
+
+static int test_rand(void)
+{
+    EVP_RAND_CTX *privctx;
+    OSSL_PARAM params[2], *p = params;
+    unsigned char entropy1[] = { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05 };
+    unsigned char entropy2[] = { 0xff, 0xfe, 0xfd };
+    unsigned char outbuf[3];
+
+    if (!TEST_ptr(privctx = RAND_get0_private(NULL)))
+        return 0;
+
+    *p++ = OSSL_PARAM_construct_octet_string(OSSL_RAND_PARAM_TEST_ENTROPY,
+                                             entropy1, sizeof(entropy1));
+    *p = OSSL_PARAM_construct_end();
+
+    if (!TEST_ptr(privctx = RAND_get0_private(NULL))
+            || !TEST_true(EVP_RAND_CTX_set_params(privctx, params))
+            || !TEST_int_gt(RAND_priv_bytes(outbuf, sizeof(outbuf)), 0)
+            || !TEST_mem_eq(outbuf, sizeof(outbuf), entropy1, sizeof(outbuf))
+            || !TEST_int_le(RAND_priv_bytes(outbuf, sizeof(outbuf) + 1), 0)
+            || !TEST_int_gt(RAND_priv_bytes(outbuf, sizeof(outbuf)), 0)
+            || !TEST_mem_eq(outbuf, sizeof(outbuf),
+                            entropy1 + sizeof(outbuf), sizeof(outbuf)))
+        return 0;
+
+    *params = OSSL_PARAM_construct_octet_string(OSSL_RAND_PARAM_TEST_ENTROPY,
+                                                entropy2, sizeof(entropy2));
+    if (!TEST_true(EVP_RAND_CTX_set_params(privctx, params))
+            || !TEST_int_gt(RAND_priv_bytes(outbuf, sizeof(outbuf)), 0)
+            || !TEST_mem_eq(outbuf, sizeof(outbuf), entropy2, sizeof(outbuf)))
+        return 0;
+    return 1;
+}
+
+int setup_tests(void)
+{
+    if (!TEST_true(RAND_set_DRBG_type(NULL, "TEST-RAND", NULL, NULL, NULL)))
+        return 0;
+    ADD_TEST(test_rand);
+    return 1;
+}
diff --git a/test/recipes/05-test_rand.t b/test/recipes/05-test_rand.t
index 750b1a28e8..f37b7bcb98 100644
--- a/test/recipes/05-test_rand.t
+++ b/test/recipes/05-test_rand.t
@@ -11,8 +11,9 @@ use warnings;
 use OpenSSL::Test;
 use OpenSSL::Test::Utils;
 
-plan tests => 2;
+plan tests => 3;
 setup("test_rand");
 
+ok(run(test(["rand_test"])));
 ok(run(test(["drbgtest"])));
 ok(run(test(["rand_status_test"])));