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ASN1_EXTERN_FUNCS(3) OpenSSL ASN1_EXTERN_FUNCS(3)
NAME
ASN1_EXTERN_FUNCS, ASN1_ex_d2i, ASN1_ex_d2i_ex, ASN1_ex_i2d,
ASN1_ex_new_func, ASN1_ex_new_ex_func, ASN1_ex_free_func,
ASN1_ex_print_func, IMPLEMENT_EXTERN_ASN1 - ASN.1 external function
support
LIBRARY
libcrypto, -lcrypto
SYNOPSIS
#include <openssl/asn1t.h>
typedef int ASN1_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
const ASN1_ITEM *it, int tag, int aclass, char opt,
ASN1_TLC *ctx);
typedef int ASN1_ex_d2i_ex(ASN1_VALUE **pval, const unsigned char **in, long len,
const ASN1_ITEM *it, int tag, int aclass, char opt,
ASN1_TLC *ctx, OSSL_LIB_CTX *libctx,
const char *propq);
typedef int ASN1_ex_i2d(const ASN1_VALUE **pval, unsigned char **out,
const ASN1_ITEM *it, int tag, int aclass);
typedef int ASN1_ex_new_func(ASN1_VALUE **pval, const ASN1_ITEM *it);
typedef int ASN1_ex_new_ex_func(ASN1_VALUE **pval, const ASN1_ITEM *it,
OSSL_LIB_CTX *libctx, const char *propq);
typedef void ASN1_ex_free_func(ASN1_VALUE **pval, const ASN1_ITEM *it);
typedef int ASN1_ex_print_func(BIO *out, const ASN1_VALUE **pval,
int indent, const char *fname,
const ASN1_PCTX *pctx);
struct ASN1_EXTERN_FUNCS_st {
void *app_data;
ASN1_ex_new_func *asn1_ex_new;
ASN1_ex_free_func *asn1_ex_free;
ASN1_ex_free_func *asn1_ex_clear;
ASN1_ex_d2i *asn1_ex_d2i;
ASN1_ex_i2d *asn1_ex_i2d;
ASN1_ex_print_func *asn1_ex_print;
ASN1_ex_new_ex_func *asn1_ex_new_ex;
ASN1_ex_d2i_ex *asn1_ex_d2i_ex;
};
typedef struct ASN1_EXTERN_FUNCS_st ASN1_EXTERN_FUNCS;
#define IMPLEMENT_EXTERN_ASN1(sname, tag, fptrs)
DESCRIPTION
ASN.1 data structures templates are typically defined in OpenSSL using
a series of macros such as ASN1_SEQUENCE(), ASN1_SEQUENCE_END() and so
on. Instead templates can also be defined based entirely on external
functions. These external functions are called to perform operations
such as creating a new ASN1_VALUE or converting an ASN1_VALUE to or
from DER encoding.
The macro IMPLEMENT_EXTERN_ASN1() can be used to create such an
externally defined structure. The name of the structure should be
supplied in the sname parameter. The tag for the structure (e.g.
typically V_ASN1_SEQUENCE) should be supplied in the tag parameter.
Finally a pointer to an ASN1_EXTERN_FUNCS structure should be supplied
in the fptrs parameter.
The ASN1_EXTERN_FUNCS structure has the following entries.
app_data
A pointer to arbitrary application specific data.
asn1_ex_new
A "new" function responsible for constructing a new ASN1_VALUE
object. The newly constructed value should be stored in *pval. The
it parameter is a pointer to the ASN1_ITEM template object created
via the IMPLEMENT_EXTERN_ASN1() macro.
Returns a positive value on success or 0 on error.
asn1_ex_free
A "free" function responsible for freeing the ASN1_VALUE passed in
*pval that was previously allocated via a "new" function. The it
parameter is a pointer to the ASN1_ITEM template object created via
the IMPLEMENT_EXTERN_ASN1() macro.
asn1_ex_clear
A "clear" function responsible for clearing any data in the
ASN1_VALUE passed in *pval and making it suitable for reuse. The it
parameter is a pointer to the ASN1_ITEM template object created via
the IMPLEMENT_EXTERN_ASN1() macro.
asn1_ex_d2i
A "d2i" function responsible for converting DER data with the tag
tag and class class into an ASN1_VALUE. If *pval is non-NULL then
the ASN_VALUE it points to should be reused. Otherwise a new
ASN1_VALUE should be allocated and stored in *pval. *in points to
the DER data to be decoded and len is the length of that data.
After decoding *in should be updated to point at the next byte
after the decoded data. If the ASN1_VALUE is considered optional in
this context then opt will be nonzero. Otherwise it will be zero.
The it parameter is a pointer to the ASN1_ITEM template object
created via the IMPLEMENT_EXTERN_ASN1() macro. A pointer to the
current ASN1_TLC context (which may be required for other ASN1
function calls) is passed in the ctx parameter.
The asn1_ex_d2i entry may be NULL if asn1_ex_d2i_ex has been
specified instead.
Returns <= 0 on error or a positive value on success.
asn1_ex_i2d
An "i2d" function responsible for converting an ASN1_VALUE into DER
encoding. On entry *pval will contain the ASN1_VALUE to be
encoded. If default tagging is to be used then tag will be -1 on
entry. Otherwise if implicit tagging should be used then tag and
aclass will be the tag and associated class.
If out is not NULL then this function should write the DER encoded
data to the buffer in *out, and then increment *out to point to
immediately after the data just written.
If out is NULL then no data should be written but the length
calculated and returned as if it were.
The asn1_ex_i2d entry may be NULL if asn1_ex_i2d_ex has been
specified instead.
The return value should be negative if a fatal error occurred, or 0
if a non-fatal error occurred. Otherwise it should return the
length of the encoded data.
asn1_ex_print
A "print" function. out is the BIO to print the output to. *pval is
the ASN1_VALUE to be printed. indent is the number of spaces of
indenting to be printed before any data is printed. fname is
currently unused and is always "". pctx is a pointer to the
ASN1_PCTX for the print operation.
Returns 0 on error or a positive value on success. If the return
value is 2 then an additional newline will be printed after the
data printed by this function.
asn1_ex_new_ex
This is the same as asn1_ex_new except that it is additionally
passed the OSSL_LIB_CTX to be used in libctx and any property query
string to be used for algorithm fetching in the propq parameter.
See "ALGORITHM FETCHING" in crypto(7) for further details. If
asn1_ex_new_ex is non NULL, then it will always be called in
preference to asn1_ex_new.
asn1_ex_d2i_ex
This is the same as asn1_ex_d2i except that it is additionally
passed the OSSL_LIB_CTX to be used in libctx and any property query
string to be used for algorithm fetching in the propq parameter.
See "ALGORITHM FETCHING" in crypto(7) for further details. If
asn1_ex_d2i_ex is non NULL, then it will always be called in
preference to asn1_ex_d2i.
RETURN VALUES
Return values for the various callbacks are as described above.
SEE ALSO
ASN1_item_new_ex(3)
HISTORY
The asn1_ex_new_ex and asn1_ex_d2i_ex callbacks were added in OpenSSL
3.0.
COPYRIGHT
Copyright 2021 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>.
3.0.12 2023-05-07 ASN1_EXTERN_FUNCS(3)