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Title "ASN1_EXTERN_FUNCS 3ossl" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
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 Header "SYNOPSIS" .Vb 1 #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) .Ve Header "DESCRIPTION" \s-1ASN.1\s0 data structures templates are typically defined in OpenSSL using a series of macros such as \s-1ASN1_SEQUENCE\s0(), \s-1ASN1_SEQUENCE_END\s0() 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 \fB\s-1ASN1_VALUE\s0 or converting an \s-1ASN1_VALUE\s0 to or from \s-1DER\s0 encoding.

The macro \s-1IMPLEMENT_EXTERN_ASN1\s0() 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 \fB\s-1ASN1_EXTERN_FUNCS\s0 structure should be supplied in the fptrs parameter.

The \s-1ASN1_EXTERN_FUNCS\s0 structure has the following entries.

Item "app_data" A pointer to arbitrary application specific data. Item "asn1_ex_new" A \*(L"new\*(R" function responsible for constructing a new \s-1ASN1_VALUE\s0 object. The newly constructed value should be stored in *pval. The it parameter is a pointer to the \s-1ASN1_ITEM\s0 template object created via the \s-1IMPLEMENT_EXTERN_ASN1\s0() macro. .Sp Returns a positive value on success or 0 on error. Item "asn1_ex_free" A \*(L"free\*(R" function responsible for freeing the \s-1ASN1_VALUE\s0 passed in *pval that was previously allocated via a \*(L"new\*(R" function. The it parameter is a pointer to the \s-1ASN1_ITEM\s0 template object created via the \s-1IMPLEMENT_EXTERN_ASN1\s0() macro. Item "asn1_ex_clear" A \*(L"clear\*(R" function responsible for clearing any data in the \s-1ASN1_VALUE\s0 passed in *pval and making it suitable for reuse. The it parameter is a pointer to the \s-1ASN1_ITEM\s0 template object created via the \s-1IMPLEMENT_EXTERN_ASN1\s0() macro. Item "asn1_ex_d2i" A \*(L"d2i\*(R" function responsible for converting \s-1DER\s0 data with the tag tag and class class into an \s-1ASN1_VALUE\s0. If *pval is non-NULL then the \fB\s-1ASN_VALUE\s0 it points to should be reused. Otherwise a new \s-1ASN1_VALUE\s0 should be allocated and stored in *pval. *in points to the \s-1DER\s0 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 \s-1ASN1_VALUE\s0 is considered optional in this context then opt will be nonzero. Otherwise it will be zero. The it parameter is a pointer to the \s-1ASN1_ITEM\s0 template object created via the \s-1IMPLEMENT_EXTERN_ASN1\s0() macro. A pointer to the current \fB\s-1ASN1_TLC\s0 context (which may be required for other \s-1ASN1\s0 function calls) is passed in the ctx parameter. .Sp The asn1_ex_d2i entry may be \s-1NULL\s0 if asn1_ex_d2i_ex has been specified instead. .Sp Returns <= 0 on error or a positive value on success. Item "asn1_ex_i2d" An \*(L"i2d\*(R" function responsible for converting an \s-1ASN1_VALUE\s0 into \s-1DER\s0 encoding. On entry *pval will contain the \s-1ASN1_VALUE\s0 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. .Sp If out is not \s-1NULL\s0 then this function should write the \s-1DER\s0 encoded data to the buffer in *out, and then increment *out to point to immediately after the data just written. .Sp If out is \s-1NULL\s0 then no data should be written but the length calculated and returned as if it were. .Sp The asn1_ex_i2d entry may be \s-1NULL\s0 if asn1_ex_i2d_ex has been specified instead. .Sp 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. Item "asn1_ex_print" A \*(L"print\*(R" function. out is the \s-1BIO\s0 to print the output to. *pval is the \fB\s-1ASN1_VALUE\s0 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 \s-1ASN1_PCTX\s0 for the print operation. .Sp 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. Item "asn1_ex_new_ex" This is the same as asn1_ex_new except that it is additionally passed the \s-1OSSL_LIB_CTX\s0 to be used in libctx and any property query string to be used for algorithm fetching in the propq parameter. See \*(L"\s-1ALGORITHM FETCHING\*(R"\s0 in crypto\|(7) for further details. If asn1_ex_new_ex is non \s-1NULL,\s0 then it will always be called in preference to asn1_ex_new. Item "asn1_ex_d2i_ex" This is the same as asn1_ex_d2i except that it is additionally passed the \s-1OSSL_LIB_CTX\s0 to be used in libctx and any property query string to be used for algorithm fetching in the propq parameter. See \*(L"\s-1ALGORITHM FETCHING\*(R"\s0 in crypto\|(7) for further details. If asn1_ex_d2i_ex is non \s-1NULL,\s0 then it will always be called in preference to asn1_ex_d2i. Header "RETURN VALUES" Return values for the various callbacks are as described above. Header "SEE ALSO" \fBASN1_item_new_ex\|(3) Header "HISTORY" The asn1_ex_new_ex and asn1_ex_d2i_ex callbacks were added in OpenSSL 3.0. Header "COPYRIGHT" Copyright 2021 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.