Prepare to provide EVP_MD_CTX{,_set}_pkey_ctx()

This API with very strange ownership handling is used by Ruby 3.1,
unfortunately.

For unclear reasons, it was decided that the caller retains ownership of
the pctx passed in.  EVP_PKEY_CTX aren't refcounted, so a flag was added to
make sure that md_ctx->pctx is not freed in EVP_MD_CTX_{cleanup,reset}().
Since EVP_MD_CTX_copy_ex() duplicates the md_ctx->pctx, the flag also needs
to be unset on the duplicated EVP_MD_CTX.

ok inoguchi jsing

1 files changed, 30 insertions, 1 deletions

diff --git a/src/lib/libcrypto/evp/evp_lib.c b/src/lib/libcrypto/evp/evp_lib.c
index 8070fa45ae..c96813987f 100644
--- a/src/lib/libcrypto/evp/evp_lib.c
+++ b/src/lib/libcrypto/evp/evp_lib.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: evp_lib.c,v 1.22 2022/01/07 11:13:54 tb Exp $ */
+/* $OpenBSD: evp_lib.c,v 1.23 2022/01/09 15:15:25 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -385,6 +385,35 @@ EVP_MD_CTX_md_data(const EVP_MD_CTX *ctx)
         return ctx->md_data;
 }
 
+EVP_PKEY_CTX *
+EVP_MD_CTX_pkey_ctx(const EVP_MD_CTX *ctx)
+{
+        return ctx->pctx;
+}
+
+void
+EVP_MD_CTX_set_pkey_ctx(EVP_MD_CTX *ctx, EVP_PKEY_CTX *pctx)
+{
+        if (EVP_MD_CTX_test_flags(ctx, EVP_MD_CTX_FLAG_KEEP_PKEY_CTX)) {
+                EVP_MD_CTX_clear_flags(ctx, EVP_MD_CTX_FLAG_KEEP_PKEY_CTX);
+        } else {
+                EVP_PKEY_CTX_free(ctx->pctx);
+        }
+
+        ctx->pctx = pctx;
+
+        if (pctx != NULL) {
+                /*
+                 * For unclear reasons it was decided that the caller keeps
+                 * ownership of pctx. So a flag was invented to make sure we
+                 * don't free it in EVP_MD_CTX_cleanup(). We also need to
+                 * unset it in EVP_MD_CTX_copy_ex(). Fortunately, the flag
+                 * isn't public...
+                 */
+                EVP_MD_CTX_set_flags(ctx, EVP_MD_CTX_FLAG_KEEP_PKEY_CTX);
+        }
+}
+
 void
 EVP_MD_CTX_set_flags(EVP_MD_CTX *ctx, int flags)
 {