Avoid segfaults in EVP_PKEY_CTX_free()

It is possible to call pmeth->cleanup() with an EVP_PKEY_CTX whose data
is NULL. If pmeth->init() in int_ctx_new() fails, EVP_PKEY_CTX_free() is
called with such a context. This in turn calls pmeth->cleanup(), and thus
these cleanup functions must be careful not to use NULL data.  Most of
them are, but one of GOST's functions and HMAC's aren't.

Reported for HMAC by Masaru Masada
#129

ok bcook jsing

Author: tb

src/lib/libcrypto/gost/gostr341001_pmeth.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: gostr341001_pmeth.c,v 1.15 2022/01/07 09:40:03 tb Exp $ */
+/* $OpenBSD: gostr341001_pmeth.c,v 1.16 2022/03/30 07:17:48 tb Exp $ */
 /*
  * Copyright (c) 2014 Dmitry Eremin-Solenikov <[email protected]>
  * Copyright (c) 2005-2006 Cryptocom LTD
@@ -175,7 +175,10 @@ pkey_gost01_copy(EVP_PKEY_CTX *dst, EVP_PKEY_CTX *src)
 static void
 pkey_gost01_cleanup(EVP_PKEY_CTX *ctx)
 {
-	struct gost_pmeth_data *data = EVP_PKEY_CTX_get_data(ctx);
+	struct gost_pmeth_data *data;
+
+	if ((data = EVP_PKEY_CTX_get_data(ctx)) == NULL)
+		return;
 
 	free(data->shared_ukm);
 	free(data);

src/lib/libcrypto/hmac/hm_pmeth.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: hm_pmeth.c,v 1.12 2022/03/30 07:12:30 tb Exp $ */
+/* $OpenBSD: hm_pmeth.c,v 1.13 2022/03/30 07:17:48 tb Exp $ */
 /* Written by Dr Stephen N Henson ([email protected]) for the OpenSSL
  * project 2007.
  */
@@ -116,7 +116,10 @@ pkey_hmac_copy(EVP_PKEY_CTX *dst, EVP_PKEY_CTX *src)
 static void
 pkey_hmac_cleanup(EVP_PKEY_CTX *ctx)
 {
-	HMAC_PKEY_CTX *hctx = ctx->data;
+	HMAC_PKEY_CTX *hctx;
+
+	if ((hctx = ctx->data) == NULL)
+		return;
 
 	HMAC_CTX_cleanup(&hctx->ctx);
 	freezero(hctx->ktmp.data, hctx->ktmp.length);