params: add helper functions to allocate & copy params

Added a function to allocate a buffer and copy a maching param.
Added a function to allocate a buffer and concatenate all matching params.

Fixes #20717

Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20724)

1 files changed, 38 insertions, 0 deletions

diff --git a/include/internal/params.h b/include/internal/params.h
new file mode 100644
index 0000000000..3fbd0cf954
--- /dev/null
+++ b/include/internal/params.h
@@ -0,0 +1,38 @@
+/*
+ * Copyright 2023 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 <stddef.h>
+#include <openssl/params.h>
+
+/*
+ * Extract the parameter into an allocated buffer.
+ * Any existing allocation in *out is cleared and freed.
+ *
+ * Returns 1 on success, 0 on failure and -1  if there are no matching params.
+ *
+ * *out and *out_len are guaranteed to be untouched if this function
+ * doesn't return success.
+ */
+int ossl_param_get1_octet_string(const OSSL_PARAM *params, const char *name,
+                                 unsigned char **out, size_t *out_len);
+/*
+ * Concatenate all of the matching params together.
+ * *out will point to an allocated buffer on successful return.
+ * Any existing allocation in *out is cleared and freed.
+ *
+ * Passing 0 for maxsize means unlimited size output.
+ *
+ * Returns 1 on success, 0 on failure and -1 if there are no matching params.
+ *
+ * *out and *out_len are guaranteed to be untouched if this function
+ * doesn't return success.
+ */
+int ossl_param_get1_concat_octet_string(const OSSL_PARAM *params, const char *name,
+                                        unsigned char **out, size_t *out_len,
+                                        size_t maxsize);