f585cefc04
Document the new EC functions that are OPENSSL_CTX aware. Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com> (Merged from https://github.com/openssl/openssl/pull/9380)
163 lines
7.2 KiB
Text
163 lines
7.2 KiB
Text
=pod
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=head1 NAME
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EC_GROUP_get_ecparameters,
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EC_GROUP_get_ecpkparameters,
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EC_GROUP_new_ex,
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EC_GROUP_new,
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EC_GROUP_new_from_ecparameters,
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EC_GROUP_new_from_ecpkparameters,
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EC_GROUP_free,
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EC_GROUP_clear_free,
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EC_GROUP_new_curve_GFp,
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EC_GROUP_new_curve_GF2m,
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EC_GROUP_new_by_curve_name_ex,
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EC_GROUP_new_by_curve_name,
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EC_GROUP_set_curve,
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EC_GROUP_get_curve,
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EC_GROUP_set_curve_GFp,
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EC_GROUP_get_curve_GFp,
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EC_GROUP_set_curve_GF2m,
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EC_GROUP_get_curve_GF2m,
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EC_get_builtin_curves - Functions for creating and destroying EC_GROUP
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objects
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=head1 SYNOPSIS
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#include <openssl/ec.h>
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EC_GROUP *EC_GROUP_new_ex(OPENSSL_CTX *libctx, const EC_METHOD *meth);
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EC_GROUP *EC_GROUP_new(const EC_METHOD *meth);
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EC_GROUP *EC_GROUP_new_from_ecparameters(const ECPARAMETERS *params)
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EC_GROUP *EC_GROUP_new_from_ecpkparameters(const ECPKPARAMETERS *params)
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void EC_GROUP_free(EC_GROUP *group);
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void EC_GROUP_clear_free(EC_GROUP *group);
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EC_GROUP *EC_GROUP_new_curve_GFp(const BIGNUM *p, const BIGNUM *a,
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const BIGNUM *b, BN_CTX *ctx);
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EC_GROUP *EC_GROUP_new_curve_GF2m(const BIGNUM *p, const BIGNUM *a,
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const BIGNUM *b, BN_CTX *ctx);
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EC_GROUP *EC_GROUP_new_by_curve_name_ex(OPENSSL_CTX *libctx, int nid);
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EC_GROUP *EC_GROUP_new_by_curve_name(int nid);
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int EC_GROUP_set_curve(EC_GROUP *group, const BIGNUM *p, const BIGNUM *a,
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const BIGNUM *b, BN_CTX *ctx);
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int EC_GROUP_get_curve(const EC_GROUP *group, BIGNUM *p, BIGNUM *a, BIGNUM *b,
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BN_CTX *ctx);
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int EC_GROUP_set_curve_GFp(EC_GROUP *group, const BIGNUM *p,
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const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx);
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int EC_GROUP_get_curve_GFp(const EC_GROUP *group, BIGNUM *p,
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BIGNUM *a, BIGNUM *b, BN_CTX *ctx);
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int EC_GROUP_set_curve_GF2m(EC_GROUP *group, const BIGNUM *p,
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const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx);
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int EC_GROUP_get_curve_GF2m(const EC_GROUP *group, BIGNUM *p,
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BIGNUM *a, BIGNUM *b, BN_CTX *ctx);
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ECPARAMETERS *EC_GROUP_get_ecparameters(const EC_GROUP *group, ECPARAMETERS *params)
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ECPKPARAMETERS *EC_GROUP_get_ecpkparameters(const EC_GROUP *group, ECPKPARAMETERS *params)
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size_t EC_get_builtin_curves(EC_builtin_curve *r, size_t nitems);
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=head1 DESCRIPTION
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Within the library there are two forms of elliptic curve that are of interest. The first form is those defined over the
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prime field Fp. The elements of Fp are the integers 0 to p-1, where p is a prime number. This gives us a revised
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elliptic curve equation as follows:
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y^2 mod p = x^3 +ax + b mod p
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The second form is those defined over a binary field F2^m where the elements of the field are integers of length at
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most m bits. For this form the elliptic curve equation is modified to:
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y^2 + xy = x^3 + ax^2 + b (where b != 0)
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Operations in a binary field are performed relative to an B<irreducible polynomial>. All such curves with OpenSSL
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use a trinomial or a pentanomial for this parameter.
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A new curve can be constructed by calling EC_GROUP_new_ex, using the implementation provided by B<meth> (see
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L<EC_GFp_simple_method(3)>) and associated with the library context B<ctx>
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(see L<OPENSSL_CTX(3)>).
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The B<ctx> parameter may be NULL in which case the default library context is used.
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It is then necessary to call EC_GROUP_set_curve() to set the curve parameters.
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EC_GROUP_new_from_ecparameters() will create a group from the
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specified B<params> and
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EC_GROUP_new_from_ecpkparameters() will create a group from the specific PK B<params>.
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EC_GROUP_new is the same as EC_GROUP_new_ex() except that the library context
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used is always the default library context.
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EC_GROUP_set_curve() sets the curve parameters B<p>, B<a> and B<b>. For a curve over Fp B<b>
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is the prime for the field. For a curve over F2^m B<p> represents the irreducible polynomial - each bit
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represents a term in the polynomial. Therefore there will either be three or five bits set dependent on whether
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the polynomial is a trinomial or a pentanomial.
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EC_group_get_curve() obtains the previously set curve parameters.
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EC_GROUP_set_curve_GFp() and EC_GROUP_set_curve_GF2m() are synonyms for EC_GROUP_set_curve(). They are defined for
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backwards compatibility only and should not be used.
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EC_GROUP_get_curve_GFp() and EC_GROUP_get_curve_GF2m() are synonyms for EC_GROUP_get_curve(). They are defined for
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backwards compatibility only and should not be used.
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The functions EC_GROUP_new_curve_GFp and EC_GROUP_new_curve_GF2m are shortcuts for calling EC_GROUP_new and then the
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EC_GROUP_set_curve function. An appropriate default implementation method will be used.
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Whilst the library can be used to create any curve using the functions described above, there are also a number of
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predefined curves that are available. In order to obtain a list of all of the predefined curves, call the function
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EC_get_builtin_curves. The parameter B<r> should be an array of EC_builtin_curve structures of size B<nitems>. The function
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will populate the B<r> array with information about the builtin curves. If B<nitems> is less than the total number of
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curves available, then the first B<nitems> curves will be returned. Otherwise the total number of curves will be
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provided. The return value is the total number of curves available (whether that number has been populated in B<r> or
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not). Passing a NULL B<r>, or setting B<nitems> to 0 will do nothing other than return the total number of curves available.
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The EC_builtin_curve structure is defined as follows:
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typedef struct {
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int nid;
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const char *comment;
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} EC_builtin_curve;
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Each EC_builtin_curve item has a unique integer id (B<nid>), and a human readable comment string describing the curve.
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In order to construct a builtin curve use the function EC_GROUP_new_by_curve_name_ex and provide the B<nid> of the curve to
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be constructed and the associated library context to be used in B<ctx> (see L<OPENSSL_CTX(3)>).
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The B<ctx> value may be NULL in which case the default library context is used.
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EC_GROUP_new_by_curve_name is the same as EC_GROUP_new_by_curve_name_ex except
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that the default library context is always used.
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EC_GROUP_free frees the memory associated with the EC_GROUP.
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If B<group> is NULL nothing is done.
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EC_GROUP_clear_free destroys any sensitive data held within the EC_GROUP and then frees its memory.
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If B<group> is NULL nothing is done.
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=head1 RETURN VALUES
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All EC_GROUP_new* functions return a pointer to the newly constructed group, or NULL on error.
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EC_get_builtin_curves returns the number of builtin curves that are available.
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EC_GROUP_set_curve_GFp, EC_GROUP_get_curve_GFp, EC_GROUP_set_curve_GF2m, EC_GROUP_get_curve_GF2m return 1 on success or 0 on error.
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=head1 SEE ALSO
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L<crypto(7)>, L<EC_GROUP_copy(3)>,
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L<EC_POINT_new(3)>, L<EC_POINT_add(3)>, L<EC_KEY_new(3)>,
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L<EC_GFp_simple_method(3)>, L<d2i_ECPKParameters(3)>,
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L<OPENSSL_CTX(3)>
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=head1 HISTORY
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EC_GROUP_new_ex and EC_GROUP_new_by_curve_name_ex were added in OpenSSL 3.0.
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=head1 COPYRIGHT
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Copyright 2013-2018 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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