NAME

ASN1_item_new, ASN1_item_free —

generic ASN.1 value constructor and destructor

SYNOPSIS

#include <openssl/asn1.h>

ASN1_VALUE *
ASN1_item_new(const ASN1_ITEM *it);

void
ASN1_item_free(ASN1_VALUE *val_in, const ASN1_ITEM *it);

DESCRIPTION

ASN1_item_new() allocates and initializes an empty ASN.1 value of the type described by the global static object it.

If the item type described by it is reference counted, ASN1_item_free() decrements the reference count of val_in. Otherwise, or if the reference count reaches 0, ASN1_item_free() frees val_in, assuming that it is of the type described by it. If the true type of val_in fails to match the specified it, buffer overflows and segmentation faults are likely to occur. It is not possible to recover the type of an ASN1_VALUE object by inspecting it; the type always needs to be remembered separately.

ASN1_VALUE is an incomplete type, and pointers to it always require casting to the correct complete type before they can be dereferenced. For all practical purposes, a pointer to ASN1_VALUE is equivalent to a void pointer.

Depending on it, there are more than 150 different types that ASN1_item_new() may return. Most of them are pointers to structures or pointers to arrays of structures, but there are a few exceptions, for example: If it is ASN1_NULL_it, ASN1_item_new() returns a specific invalid pointer representing the unique ASN1_NULL object. If it is LONG_it, ASN1_item_new() does not return a pointer at all, but a long value cast to ASN1_VALUE *.

RETURN VALUES

The ASN1_item_new() function returns the new ASN1_VALUE object if successful; otherwise NULL is returned and an error code can be retrieved with ERR_get_error(3).

HISTORY

ASN1_item_new() and ASN1_item_free() first appeared in OpenSSL 0.9.7 and have been available since OpenBSD 3.2.

BUGS

The ASN1_VALUE type compromises type safety and invites programming mistakes that will typically have severe consequences.