From 8bbc7f2211bacd201b8f2b219aad067c17b8c2ec Mon Sep 17 00:00:00 2001
From: Dmitry Belyavskiy <beldmit@gmail.com>
Date: Wed, 4 Sep 2019 22:49:09 +0300
Subject: [PATCH] Disallow change EVP_MD properties once set

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9764)
---
 crypto/evp/evp_lib.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/crypto/evp/evp_lib.c b/crypto/evp/evp_lib.c
index acb90f222b..9c3edb3322 100644
--- a/crypto/evp/evp_lib.c
+++ b/crypto/evp/evp_lib.c
@@ -574,26 +574,41 @@ void EVP_MD_meth_free(EVP_MD *md)
 }
 int EVP_MD_meth_set_input_blocksize(EVP_MD *md, int blocksize)
 {
+    if (md->block_size != 0)
+        return 0;
+
     md->block_size = blocksize;
     return 1;
 }
 int EVP_MD_meth_set_result_size(EVP_MD *md, int resultsize)
 {
+    if (md->md_size != 0)
+        return 0;
+
     md->md_size = resultsize;
     return 1;
 }
 int EVP_MD_meth_set_app_datasize(EVP_MD *md, int datasize)
 {
+    if (md->ctx_size != 0)
+        return 0;
+
     md->ctx_size = datasize;
     return 1;
 }
 int EVP_MD_meth_set_flags(EVP_MD *md, unsigned long flags)
 {
+    if (md->flags != 0)
+        return 0;
+
     md->flags = flags;
     return 1;
 }
 int EVP_MD_meth_set_init(EVP_MD *md, int (*init)(EVP_MD_CTX *ctx))
 {
+    if (md->init != NULL)
+        return 0;
+
     md->init = init;
     return 1;
 }
@@ -601,29 +616,44 @@ int EVP_MD_meth_set_update(EVP_MD *md, int (*update)(EVP_MD_CTX *ctx,
                                                      const void *data,
                                                      size_t count))
 {
+    if (md->update != NULL)
+        return 0;
+
     md->update = update;
     return 1;
 }
 int EVP_MD_meth_set_final(EVP_MD *md, int (*final)(EVP_MD_CTX *ctx,
                                                    unsigned char *md))
 {
+    if (md->final != NULL)
+        return 0;
+
     md->final = final;
     return 1;
 }
 int EVP_MD_meth_set_copy(EVP_MD *md, int (*copy)(EVP_MD_CTX *to,
                                                  const EVP_MD_CTX *from))
 {
+    if (md->copy != NULL)
+        return 0;
+
     md->copy = copy;
     return 1;
 }
 int EVP_MD_meth_set_cleanup(EVP_MD *md, int (*cleanup)(EVP_MD_CTX *ctx))
 {
+    if (md->cleanup != NULL)
+        return 0;
+
     md->cleanup = cleanup;
     return 1;
 }
 int EVP_MD_meth_set_ctrl(EVP_MD *md, int (*ctrl)(EVP_MD_CTX *ctx, int cmd,
                                                  int p1, void *p2))
 {
+    if (md->md_ctrl != NULL)
+        return 0;
+
     md->md_ctrl = ctrl;
     return 1;
 }
-- 
2.25.1