tests/drbgtest: use new RAND_DRBG callback_data API instead of ex_data

It took me a little while to realize why the test_rand_drbg_reseed test
kept crashing after replacing the RAND_DRBG_{gs}et_ex_data() calls by
RAND_DRBG_{gs}et_callback_data().

The reason was that the ex_data API prohibits modifying the callbacks
or callback data of chained DRBGs and returned an error which was
ignored by the `test_rand_drbg_reseed` test, for good reasons.

The `test_rand_drbg_reseed` test is special in this respect, because
it needs to install callbacks for all DRBGs, in order to intercept
and count the reseeding events.

Since the drbgtest module has access to the internal structures of
the DRBG anyway, the problem could be solved by accessing the members
directly. I added a warning comment in hook_drbg().

[extended tests]

Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/10950)

1 files changed, 16 insertions, 15 deletions

diff --git a/test/drbgtest.c b/test/drbgtest.c
index b8dcbf7b7b..34a5cc744d 100644
--- a/test/drbgtest.c
+++ b/test/drbgtest.c
@@ -127,8 +127,6 @@ static DRBG_SELFTEST_DATA drbg_test[] = {
     make_drbg_test_data_hash(NID_sha512, sha512, 0),
 };
 
-static int app_data_index;
-
 /*
  * Test context data, attached as EXDATA to the RAND_DRBG
  */
@@ -145,7 +143,7 @@ static size_t kat_entropy(RAND_DRBG *drbg, unsigned char **pout,
                           int entropy, size_t min_len, size_t max_len,
                           int prediction_resistance)
 {
-    TEST_CTX *t = (TEST_CTX *)RAND_DRBG_get_ex_data(drbg, app_data_index);
+    TEST_CTX *t = (TEST_CTX *)RAND_DRBG_get_callback_data(drbg);
 
     t->entropycnt++;
     *pout = (unsigned char *)t->entropy;
@@ -155,7 +153,7 @@ static size_t kat_entropy(RAND_DRBG *drbg, unsigned char **pout,
 static size_t kat_nonce(RAND_DRBG *drbg, unsigned char **pout,
                         int entropy, size_t min_len, size_t max_len)
 {
-    TEST_CTX *t = (TEST_CTX *)RAND_DRBG_get_ex_data(drbg, app_data_index);
+    TEST_CTX *t = (TEST_CTX *)RAND_DRBG_get_callback_data(drbg);
 
     t->noncecnt++;
     *pout = (unsigned char *)t->nonce;
@@ -213,6 +211,7 @@ static int single_kat(DRBG_SELFTEST_DATA *td)
         return 0;
     if (!TEST_true(RAND_DRBG_set_callbacks(drbg, kat_entropy, NULL,
                                            kat_nonce, NULL))
+        || !TEST_true(RAND_DRBG_set_callback_data(drbg, &t))
         || !TEST_true(disable_crngt(drbg))) {
         failures++;
         goto err;
@@ -222,7 +221,6 @@ static int single_kat(DRBG_SELFTEST_DATA *td)
     t.entropylen = td->entropylen;
     t.nonce = td->nonce;
     t.noncelen = td->noncelen;
-    RAND_DRBG_set_ex_data(drbg, app_data_index, &t);
 
     if (!TEST_true(RAND_DRBG_instantiate(drbg, td->pers, td->perslen))
             || !TEST_true(RAND_DRBG_generate(drbg, buff, td->exlen, 0,
@@ -246,9 +244,9 @@ static int single_kat(DRBG_SELFTEST_DATA *td)
      */
     if (!TEST_true(RAND_DRBG_set(drbg, td->nid, td->flags))
             || !TEST_true(RAND_DRBG_set_callbacks(drbg, kat_entropy, NULL,
-                                                  kat_nonce, NULL)))
+                                                  kat_nonce, NULL))
+            || !TEST_true(RAND_DRBG_set_callback_data(drbg, &t)))
         failures++;
-    RAND_DRBG_set_ex_data(drbg, app_data_index, &t);
     t.entropy = td->entropy_pr;
     t.entropylen = td->entropylen_pr;
     t.nonce = td->nonce_pr;
@@ -296,7 +294,7 @@ static int init(RAND_DRBG *drbg, DRBG_SELFTEST_DATA *td, TEST_CTX *t)
             || !TEST_true(RAND_DRBG_set_callbacks(drbg, kat_entropy, NULL,
                                                   kat_nonce, NULL)))
         return 0;
-    RAND_DRBG_set_ex_data(drbg, app_data_index, t);
+    RAND_DRBG_set_callback_data(drbg, t);
     t->entropy = td->entropy;
     t->entropylen = td->entropylen;
     t->nonce = td->nonce;
@@ -551,7 +549,7 @@ static HOOK_CTX master_ctx, public_ctx, private_ctx;
 
 static HOOK_CTX *get_hook_ctx(RAND_DRBG *drbg)
 {
-    return (HOOK_CTX *)RAND_DRBG_get_ex_data(drbg, app_data_index);
+    return (HOOK_CTX *)RAND_DRBG_get_callback_data(drbg);
 }
 
 /* Intercepts and counts calls to the get_entropy() callback */
@@ -579,17 +577,22 @@ static void hook_drbg(RAND_DRBG *drbg, HOOK_CTX *ctx)
     memset(ctx, 0, sizeof(*ctx));
     ctx->drbg = drbg;
     ctx->get_entropy = drbg->get_entropy;
+
+    /*
+     * We can't use the public API here, since it prohibits modifying
+     * the callbacks or the callback data of chained DRBGs.
+     */
     drbg->get_entropy = get_entropy_hook;
-    RAND_DRBG_set_ex_data(drbg, app_data_index, ctx);
+    drbg->callback_data = ctx;
 }
 
 /* Installs the hook for the get_entropy() callback of the given drbg */
 static void unhook_drbg(RAND_DRBG *drbg)
 {
-    HOOK_CTX *ctx = get_hook_ctx(drbg);
+    HOOK_CTX *ctx = drbg->callback_data;
 
-    drbg->get_entropy = ctx->get_entropy;
-    CRYPTO_free_ex_data(CRYPTO_EX_INDEX_RAND_DRBG, drbg, &drbg->ex_data);
+    if (ctx != NULL)
+        drbg->get_entropy = ctx->get_entropy;
 }
 
 /* Resets the given hook context */
@@ -1382,8 +1385,6 @@ err:
 
 int setup_tests(void)
 {
-    app_data_index = RAND_DRBG_get_ex_new_index(0L, NULL, NULL, NULL, NULL);
-
     ADD_ALL_TESTS(test_kats, OSSL_NELEM(drbg_test));
     ADD_ALL_TESTS(test_error_checks, OSSL_NELEM(drbg_test));
     ADD_TEST(test_rand_drbg_reseed);