| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | ASN1_EXTERN_FUNCS, ASN1_ex_d2i, ASN1_ex_d2i_ex, ASN1_ex_i2d, ASN1_ex_new_func,
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| 6 | ASN1_ex_new_ex_func, ASN1_ex_free_func, ASN1_ex_print_func,
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| 7 | IMPLEMENT_EXTERN_ASN1
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| 8 | - ASN.1 external function support
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| 9 |
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| 10 | =head1 SYNOPSIS
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| 11 |
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| 12 | #include <openssl/asn1t.h>
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| 13 |
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| 14 | typedef int ASN1_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
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| 15 | const ASN1_ITEM *it, int tag, int aclass, char opt,
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| 16 | ASN1_TLC *ctx);
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| 17 | typedef int ASN1_ex_d2i_ex(ASN1_VALUE **pval, const unsigned char **in, long len,
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| 18 | const ASN1_ITEM *it, int tag, int aclass, char opt,
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| 19 | ASN1_TLC *ctx, OSSL_LIB_CTX *libctx,
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| 20 | const char *propq);
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| 21 | typedef int ASN1_ex_i2d(const ASN1_VALUE **pval, unsigned char **out,
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| 22 | const ASN1_ITEM *it, int tag, int aclass);
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| 23 | typedef int ASN1_ex_new_func(ASN1_VALUE **pval, const ASN1_ITEM *it);
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| 24 | typedef int ASN1_ex_new_ex_func(ASN1_VALUE **pval, const ASN1_ITEM *it,
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| 25 | OSSL_LIB_CTX *libctx, const char *propq);
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| 26 | typedef void ASN1_ex_free_func(ASN1_VALUE **pval, const ASN1_ITEM *it);
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| 27 | typedef int ASN1_ex_print_func(BIO *out, const ASN1_VALUE **pval,
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| 28 | int indent, const char *fname,
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| 29 | const ASN1_PCTX *pctx);
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| 30 |
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| 31 | struct ASN1_EXTERN_FUNCS_st {
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| 32 | void *app_data;
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| 33 | ASN1_ex_new_func *asn1_ex_new;
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| 34 | ASN1_ex_free_func *asn1_ex_free;
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| 35 | ASN1_ex_free_func *asn1_ex_clear;
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| 36 | ASN1_ex_d2i *asn1_ex_d2i;
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| 37 | ASN1_ex_i2d *asn1_ex_i2d;
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| 38 | ASN1_ex_print_func *asn1_ex_print;
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| 39 | ASN1_ex_new_ex_func *asn1_ex_new_ex;
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| 40 | ASN1_ex_d2i_ex *asn1_ex_d2i_ex;
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| 41 | };
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| 42 | typedef struct ASN1_EXTERN_FUNCS_st ASN1_EXTERN_FUNCS;
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| 43 |
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| 44 | #define IMPLEMENT_EXTERN_ASN1(sname, tag, fptrs)
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| 45 |
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| 46 | =head1 DESCRIPTION
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| 47 |
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| 48 | ASN.1 data structures templates are typically defined in OpenSSL using a series
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| 49 | of macros such as ASN1_SEQUENCE(), ASN1_SEQUENCE_END() and so on. Instead
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| 50 | templates can also be defined based entirely on external functions. These
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| 51 | external functions are called to perform operations such as creating a new
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| 52 | B<ASN1_VALUE> or converting an B<ASN1_VALUE> to or from DER encoding.
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| 53 |
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| 54 | The macro IMPLEMENT_EXTERN_ASN1() can be used to create such an externally
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| 55 | defined structure. The name of the structure should be supplied in the I<sname>
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| 56 | parameter. The tag for the structure (e.g. typically B<V_ASN1_SEQUENCE>) should
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| 57 | be supplied in the I<tag> parameter. Finally a pointer to an
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| 58 | B<ASN1_EXTERN_FUNCS> structure should be supplied in the I<fptrs> parameter.
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| 59 |
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| 60 | The B<ASN1_EXTERN_FUNCS> structure has the following entries.
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| 61 |
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| 62 | =over 4
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| 63 |
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| 64 | =item I<app_data>
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| 65 |
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| 66 | A pointer to arbitrary application specific data.
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| 67 |
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| 68 | =item I<asn1_ex_new>
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| 69 |
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| 70 | A "new" function responsible for constructing a new B<ASN1_VALUE> object. The
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| 71 | newly constructed value should be stored in I<*pval>. The I<it> parameter is a
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| 72 | pointer to the B<ASN1_ITEM> template object created via the
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| 73 | IMPLEMENT_EXTERN_ASN1() macro.
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| 74 |
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| 75 | Returns a positive value on success or 0 on error.
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| 76 |
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| 77 | =item I<asn1_ex_free>
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| 78 |
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| 79 | A "free" function responsible for freeing the B<ASN1_VALUE> passed in I<*pval>
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| 80 | that was previously allocated via a "new" function. The I<it> parameter is a
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| 81 | pointer to the B<ASN1_ITEM> template object created via the
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| 82 | IMPLEMENT_EXTERN_ASN1() macro.
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| 83 |
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| 84 | =item I<asn1_ex_clear>
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| 85 |
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| 86 | A "clear" function responsible for clearing any data in the B<ASN1_VALUE> passed
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| 87 | in I<*pval> and making it suitable for reuse. The I<it> parameter is a pointer
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| 88 | to the B<ASN1_ITEM> template object created via the IMPLEMENT_EXTERN_ASN1()
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| 89 | macro.
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| 90 |
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| 91 | =item I<asn1_ex_d2i>
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| 92 |
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| 93 | A "d2i" function responsible for converting DER data with the tag I<tag> and
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| 94 | class I<class> into an B<ASN1_VALUE>. If I<*pval> is non-NULL then the
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| 95 | B<ASN_VALUE> it points to should be reused. Otherwise a new B<ASN1_VALUE>
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| 96 | should be allocated and stored in I<*pval>. I<*in> points to the DER data to be
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| 97 | decoded and I<len> is the length of that data. After decoding I<*in> should be
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| 98 | updated to point at the next byte after the decoded data. If the B<ASN1_VALUE>
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| 99 | is considered optional in this context then I<opt> will be nonzero. Otherwise
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| 100 | it will be zero. The I<it> parameter is a pointer to the B<ASN1_ITEM> template
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| 101 | object created via the IMPLEMENT_EXTERN_ASN1() macro. A pointer to the current
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| 102 | B<ASN1_TLC> context (which may be required for other ASN1 function calls) is
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| 103 | passed in the I<ctx> parameter.
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| 104 |
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| 105 | The I<asn1_ex_d2i> entry may be NULL if I<asn1_ex_d2i_ex> has been specified
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| 106 | instead.
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| 107 |
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| 108 | Returns <= 0 on error or a positive value on success.
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| 109 |
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| 110 | =item I<asn1_ex_i2d>
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| 111 |
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| 112 | An "i2d" function responsible for converting an B<ASN1_VALUE> into DER encoding.
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| 113 | On entry I<*pval> will contain the B<ASN1_VALUE> to be encoded. If default
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| 114 | tagging is to be used then I<tag> will be -1 on entry. Otherwise if implicit
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| 115 | tagging should be used then I<tag> and I<aclass> will be the tag and associated
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| 116 | class.
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| 117 |
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| 118 | If I<out> is not NULL then this function should write the DER encoded data to
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| 119 | the buffer in I<*out>, and then increment I<*out> to point to immediately after
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| 120 | the data just written.
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| 121 |
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| 122 | If I<out> is NULL then no data should be written but the length calculated and
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| 123 | returned as if it were.
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| 124 |
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| 125 | The I<asn1_ex_i2d> entry may be NULL if I<asn1_ex_i2d_ex> has been specified
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| 126 | instead.
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| 127 |
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| 128 | The return value should be negative if a fatal error occurred, or 0 if a
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| 129 | non-fatal error occurred. Otherwise it should return the length of the encoded
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| 130 | data.
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| 131 |
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| 132 | =item I<asn1_ex_print>
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| 133 |
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| 134 | A "print" function. I<out> is the BIO to print the output to. I<*pval> is the
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| 135 | B<ASN1_VALUE> to be printed. I<indent> is the number of spaces of indenting to
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| 136 | be printed before any data is printed. I<fname> is currently unused and is
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| 137 | always "". I<pctx> is a pointer to the B<ASN1_PCTX> for the print operation.
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| 138 |
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| 139 | Returns 0 on error or a positive value on success. If the return value is 2 then
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| 140 | an additional newline will be printed after the data printed by this function.
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| 141 |
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| 142 | =item I<asn1_ex_new_ex>
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| 143 |
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| 144 | This is the same as I<asn1_ex_new> except that it is additionally passed the
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| 145 | OSSL_LIB_CTX to be used in I<libctx> and any property query string to be used
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| 146 | for algorithm fetching in the I<propq> parameter. See
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| 147 | L<crypto(7)/ALGORITHM FETCHING> for further details. If I<asn1_ex_new_ex> is
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| 148 | non NULL, then it will always be called in preference to I<asn1_ex_new>.
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| 149 |
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| 150 | =item I<asn1_ex_d2i_ex>
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| 151 |
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| 152 | This is the same as I<asn1_ex_d2i> except that it is additionally passed the
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| 153 | OSSL_LIB_CTX to be used in I<libctx> and any property query string to be used
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| 154 | for algorithm fetching in the I<propq> parameter. See
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| 155 | L<crypto(7)/ALGORITHM FETCHING> for further details. If I<asn1_ex_d2i_ex> is
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| 156 | non NULL, then it will always be called in preference to I<asn1_ex_d2i>.
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| 157 |
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| 158 | =back
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| 159 |
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| 160 | =head1 RETURN VALUES
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| 161 |
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| 162 | Return values for the various callbacks are as described above.
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| 163 |
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| 164 | =head1 SEE ALSO
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| 165 |
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| 166 | L<ASN1_item_new_ex(3)>
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| 167 |
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| 168 | =head1 HISTORY
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| 169 |
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| 170 | The I<asn1_ex_new_ex> and I<asn1_ex_d2i_ex> callbacks were added in OpenSSL 3.0.
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| 171 |
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| 172 | =head1 COPYRIGHT
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| 173 |
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| 174 | Copyright 2021 The OpenSSL Project Authors. All Rights Reserved.
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| 175 |
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| 176 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 177 | this file except in compliance with the License. You can obtain a copy
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| 178 | in the file LICENSE in the source distribution or at
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| 179 | L<https://www.openssl.org/source/license.html>.
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| 180 |
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| 181 | =cut
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