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182 lines
7.1 KiB
Plaintext
182 lines
7.1 KiB
Plaintext
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=pod
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=head1 NAME
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ASN1_EXTERN_FUNCS, ASN1_ex_d2i, ASN1_ex_d2i_ex, ASN1_ex_i2d, ASN1_ex_new_func,
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ASN1_ex_new_ex_func, ASN1_ex_free_func, ASN1_ex_print_func,
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IMPLEMENT_EXTERN_ASN1
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- ASN.1 external function support
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=head1 SYNOPSIS
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#include <openssl/asn1t.h>
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typedef int ASN1_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
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const ASN1_ITEM *it, int tag, int aclass, char opt,
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ASN1_TLC *ctx);
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typedef int ASN1_ex_d2i_ex(ASN1_VALUE **pval, const unsigned char **in, long len,
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const ASN1_ITEM *it, int tag, int aclass, char opt,
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ASN1_TLC *ctx, OSSL_LIB_CTX *libctx,
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const char *propq);
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typedef int ASN1_ex_i2d(const ASN1_VALUE **pval, unsigned char **out,
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const ASN1_ITEM *it, int tag, int aclass);
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typedef int ASN1_ex_new_func(ASN1_VALUE **pval, const ASN1_ITEM *it);
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typedef int ASN1_ex_new_ex_func(ASN1_VALUE **pval, const ASN1_ITEM *it,
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OSSL_LIB_CTX *libctx, const char *propq);
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typedef void ASN1_ex_free_func(ASN1_VALUE **pval, const ASN1_ITEM *it);
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typedef int ASN1_ex_print_func(BIO *out, const ASN1_VALUE **pval,
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int indent, const char *fname,
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const ASN1_PCTX *pctx);
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struct ASN1_EXTERN_FUNCS_st {
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void *app_data;
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ASN1_ex_new_func *asn1_ex_new;
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ASN1_ex_free_func *asn1_ex_free;
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ASN1_ex_free_func *asn1_ex_clear;
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ASN1_ex_d2i *asn1_ex_d2i;
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ASN1_ex_i2d *asn1_ex_i2d;
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ASN1_ex_print_func *asn1_ex_print;
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ASN1_ex_new_ex_func *asn1_ex_new_ex;
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ASN1_ex_d2i_ex *asn1_ex_d2i_ex;
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};
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typedef struct ASN1_EXTERN_FUNCS_st ASN1_EXTERN_FUNCS;
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#define IMPLEMENT_EXTERN_ASN1(sname, tag, fptrs)
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=head1 DESCRIPTION
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ASN.1 data structures templates are typically defined in OpenSSL using a series
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of macros such as ASN1_SEQUENCE(), ASN1_SEQUENCE_END() and so on. Instead
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templates can also be defined based entirely on external functions. These
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external functions are called to perform operations such as creating a new
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B<ASN1_VALUE> or converting an B<ASN1_VALUE> to or from DER encoding.
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The macro IMPLEMENT_EXTERN_ASN1() can be used to create such an externally
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defined structure. The name of the structure should be supplied in the I<sname>
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parameter. The tag for the structure (e.g. typically B<V_ASN1_SEQUENCE>) should
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be supplied in the I<tag> parameter. Finally a pointer to an
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B<ASN1_EXTERN_FUNCS> structure should be supplied in the I<fptrs> parameter.
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The B<ASN1_EXTERN_FUNCS> structure has the following entries.
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=over 4
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=item I<app_data>
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A pointer to arbitrary application specific data.
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=item I<asn1_ex_new>
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A "new" function responsible for constructing a new B<ASN1_VALUE> object. The
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newly constructed value should be stored in I<*pval>. The I<it> parameter is a
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pointer to the B<ASN1_ITEM> template object created via the
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IMPLEMENT_EXTERN_ASN1() macro.
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Returns a positive value on success or 0 on error.
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=item I<asn1_ex_free>
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A "free" function responsible for freeing the B<ASN1_VALUE> passed in I<*pval>
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that was previously allocated via a "new" function. The I<it> parameter is a
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pointer to the B<ASN1_ITEM> template object created via the
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IMPLEMENT_EXTERN_ASN1() macro.
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=item I<asn1_ex_clear>
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A "clear" function responsible for clearing any data in the B<ASN1_VALUE> passed
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in I<*pval> and making it suitable for reuse. The I<it> parameter is a pointer
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to the B<ASN1_ITEM> template object created via the IMPLEMENT_EXTERN_ASN1()
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macro.
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=item I<asn1_ex_d2i>
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A "d2i" function responsible for converting DER data with the tag I<tag> and
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class I<class> into an B<ASN1_VALUE>. If I<*pval> is non-NULL then the
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B<ASN_VALUE> it points to should be reused. Otherwise a new B<ASN1_VALUE>
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should be allocated and stored in I<*pval>. I<*in> points to the DER data to be
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decoded and I<len> is the length of that data. After decoding I<*in> should be
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updated to point at the next byte after the decoded data. If the B<ASN1_VALUE>
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is considered optional in this context then I<opt> will be nonzero. Otherwise
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it will be zero. The I<it> parameter is a pointer to the B<ASN1_ITEM> template
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object created via the IMPLEMENT_EXTERN_ASN1() macro. A pointer to the current
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B<ASN1_TLC> context (which may be required for other ASN1 function calls) is
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passed in the I<ctx> parameter.
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The I<asn1_ex_d2i> entry may be NULL if I<asn1_ex_d2i_ex> has been specified
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instead.
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Returns <= 0 on error or a positive value on success.
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=item I<asn1_ex_i2d>
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An "i2d" function responsible for converting an B<ASN1_VALUE> into DER encoding.
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On entry I<*pval> will contain the B<ASN1_VALUE> to be encoded. If default
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tagging is to be used then I<tag> will be -1 on entry. Otherwise if implicit
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tagging should be used then I<tag> and I<aclass> will be the tag and associated
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class.
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If I<out> is not NULL then this function should write the DER encoded data to
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the buffer in I<*out>, and then increment I<*out> to point to immediately after
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the data just written.
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If I<out> is NULL then no data should be written but the length calculated and
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returned as if it were.
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The I<asn1_ex_i2d> entry may be NULL if I<asn1_ex_i2d_ex> has been specified
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instead.
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The return value should be negative if a fatal error occurred, or 0 if a
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non-fatal error occurred. Otherwise it should return the length of the encoded
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data.
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=item I<asn1_ex_print>
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A "print" function. I<out> is the BIO to print the output to. I<*pval> is the
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B<ASN1_VALUE> to be printed. I<indent> is the number of spaces of indenting to
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be printed before any data is printed. I<fname> is currently unused and is
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always "". I<pctx> is a pointer to the B<ASN1_PCTX> for the print operation.
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Returns 0 on error or a positive value on success. If the return value is 2 then
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an additional newline will be printed after the data printed by this function.
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=item I<asn1_ex_new_ex>
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This is the same as I<asn1_ex_new> except that it is additionally passed the
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OSSL_LIB_CTX to be used in I<libctx> and any property query string to be used
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for algorithm fetching in the I<propq> parameter. See
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L<crypto(7)/ALGORITHM FETCHING> for further details. If I<asn1_ex_new_ex> is
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non NULL, then it will always be called in preference to I<asn1_ex_new>.
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=item I<asn1_ex_d2i_ex>
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This is the same as I<asn1_ex_d2i> except that it is additionally passed the
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OSSL_LIB_CTX to be used in I<libctx> and any property query string to be used
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for algorithm fetching in the I<propq> parameter. See
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L<crypto(7)/ALGORITHM FETCHING> for further details. If I<asn1_ex_d2i_ex> is
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non NULL, then it will always be called in preference to I<asn1_ex_d2i>.
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=back
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=head1 RETURN VALUES
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Return values for the various callbacks are as described above.
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=head1 SEE ALSO
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L<ASN1_item_new_ex(3)>
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=head1 HISTORY
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The I<asn1_ex_new_ex> and I<asn1_ex_d2i_ex> callbacks were added in OpenSSL 3.0.
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=head1 COPYRIGHT
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Copyright 2021 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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