SERIALIZER: add functions for serialization to file

These functions are added:

- OSSL_SERIALIZER_to_bio()
- OSSL_SERIALIZER_to_fp() (unless 'no-stdio')

OSSL_SERIALIZER_to_bio() and OSSL_SERIALIZER_to_fp() work as wrapper
functions, and call an internal "do_output" function with the given
serializer context and a BIO to output the serialized result to.

The internal "do_output" function must have intimate knowledge of the
object being output.  This will defined independently with context
creators for specific OpenSSL types.

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/10394)

3 files changed, 51 insertions, 1 deletions

diff --git a/crypto/serializer/build.info b/crypto/serializer/build.info
index 7d69df931c..1a35152586 100644
--- a/crypto/serializer/build.info
+++ b/crypto/serializer/build.info
@@ -1 +1 @@
-SOURCE[../../libcrypto]=serializer_meth.c
+SOURCE[../../libcrypto]=serializer_meth.c serializer_lib.c
diff --git a/crypto/serializer/serializer_lib.c b/crypto/serializer/serializer_lib.c
new file mode 100644
index 0000000000..932ef1e3ae
--- /dev/null
+++ b/crypto/serializer/serializer_lib.c
@@ -0,0 +1,43 @@
+/*
+ * Copyright 2019 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/bio.h>
+#include <openssl/serializer.h>
+#include "serializer_local.h"
+
+int OSSL_SERIALIZER_to_bio(OSSL_SERIALIZER_CTX *ctx, BIO *out)
+{
+    return ctx->do_output(ctx, out);
+}
+
+#ifndef OPENSSL_NO_STDIO
+static BIO *bio_from_file(FILE *fp)
+{
+    BIO *b;
+
+    if ((b = BIO_new(BIO_s_file())) == NULL) {
+        ERR_raise(ERR_LIB_OSSL_SERIALIZER, ERR_R_BUF_LIB);
+        return NULL;
+    }
+    BIO_set_fp(b, fp, BIO_NOCLOSE);
+    return b;
+}
+
+int OSSL_SERIALIZER_to_fp(OSSL_SERIALIZER_CTX *ctx, FILE *fp)
+{
+    BIO *b = bio_from_file(fp);
+    int ret = 0;
+
+    if (b != NULL)
+        ret = OSSL_SERIALIZER_to_bio(ctx, b);
+
+    BIO_free(b);
+    return ret;
+}
+#endif
diff --git a/crypto/serializer/serializer_local.h b/crypto/serializer/serializer_local.h
index 979ba83e78..dd0eb85414 100644
--- a/crypto/serializer/serializer_local.h
+++ b/crypto/serializer/serializer_local.h
@@ -31,4 +31,11 @@ struct ossl_serializer_st {
 struct ossl_serializer_ctx_st {
     OSSL_SERIALIZER *ser;
     void *serctx;
+
+    /*
+     * |object| is the libcrypto object to handle.
+     * |do_output| must have intimate knowledge of this object.
+     */
+    const void *object;
+    int (*do_output)(OSSL_SERIALIZER_CTX *ctx, BIO *out);
 };