Rework EC documentation

This replaces the giant, poor quality and outdated EC_GROUP_copy.3,
EC_GROUP_new.3, and EC_POINT_new.3 manuals with seven new manuals
written from scratch.

* EC_GROUP_new_by_curve_name() is the entry point for builtin curves,
* EC_GROUP_new_curve_GFp() describes lower level API that should not
  usually be needed apart from a handful of accessors.
* EC_GROUP_check() contains two functions that applications should not
  need because either you know for certain something is an elliptic
  curve (so these checks are pointless) or you should not use it.
* EC_GROUP_get_curve_name() describes some low level ASN.1 footguns
  and corresponding getters.
* EC_POINT_new() contains the simple EC_POINT allocation and freeing API
* EC_POINT_get_affine_coordinates() contains the coordinate accessors
* EC_POINT_point2oct() is about encoding elliptic curve points

While all this is quite far from perfect, the diff is getting too big
and it will be easier to improve this in tree. It is definitely more
repetitive than I would like it to be.

Reviews, tweaks and general feedback are of course welcome.

discussed with jsing

1 files changed, 0 insertions, 492 deletions

diff --git a/src/lib/libcrypto/man/EC_GROUP_copy.3 b/src/lib/libcrypto/man/EC_GROUP_copy.3
deleted file mode 100644
index 2e5e798236..0000000000
--- a/src/lib/libcrypto/man/EC_GROUP_copy.3
+++ /dev/null
@@ -1,492 +0,0 @@
-.\" $OpenBSD: EC_GROUP_copy.3,v 1.16 2025/03/08 16:40:59 tb Exp $
-.\" full merge up to: OpenSSL d900a015 Oct 8 14:40:42 2015 +0200
-.\" selective merge up to: OpenSSL 24c23e1f Aug 22 10:51:25 2019 +0530
-.\"
-.\" This file was written by Matt Caswell <matt@openssl.org>,
-.\" Dr. Stephen Henson <steve@openssl.org>,
-.\" and Jayaram X Matta <jayaramx.matta@intel.com>.
-.\" Copyright (c) 2013, 2015, 2019 The OpenSSL Project.  All rights reserved.
-.\"
-.\" Redistribution and use in source and binary forms, with or without
-.\" modification, are permitted provided that the following conditions
-.\" are met:
-.\"
-.\" 1. Redistributions of source code must retain the above copyright
-.\"    notice, this list of conditions and the following disclaimer.
-.\"
-.\" 2. Redistributions in binary form must reproduce the above copyright
-.\"    notice, this list of conditions and the following disclaimer in
-.\"    the documentation and/or other materials provided with the
-.\"    distribution.
-.\"
-.\" 3. All advertising materials mentioning features or use of this
-.\"    software must display the following acknowledgment:
-.\"    "This product includes software developed by the OpenSSL Project
-.\"    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
-.\"
-.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
-.\"    endorse or promote products derived from this software without
-.\"    prior written permission. For written permission, please contact
-.\"    openssl-core@openssl.org.
-.\"
-.\" 5. Products derived from this software may not be called "OpenSSL"
-.\"    nor may "OpenSSL" appear in their names without prior written
-.\"    permission of the OpenSSL Project.
-.\"
-.\" 6. Redistributions of any form whatsoever must retain the following
-.\"    acknowledgment:
-.\"    "This product includes software developed by the OpenSSL Project
-.\"    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
-.\"
-.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
-.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
-.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
-.\" PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
-.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
-.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
-.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
-.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
-.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
-.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
-.\" OF THE POSSIBILITY OF SUCH DAMAGE.
-.\"
-.Dd $Mdocdate: March 8 2025 $
-.Dt EC_GROUP_COPY 3
-.Os
-.Sh NAME
-.Nm EC_GROUP_copy ,
-.Nm EC_GROUP_dup ,
-.Nm EC_GROUP_set_generator ,
-.Nm EC_GROUP_get0_generator ,
-.Nm EC_GROUP_get_order ,
-.Nm EC_GROUP_order_bits ,
-.Nm EC_GROUP_get_cofactor ,
-.Nm EC_GROUP_set_curve_name ,
-.Nm EC_GROUP_get_curve_name ,
-.Nm EC_GROUP_set_asn1_flag ,
-.Nm EC_GROUP_get_asn1_flag ,
-.Nm EC_GROUP_set_point_conversion_form ,
-.Nm EC_GROUP_get_point_conversion_form ,
-.Nm EC_GROUP_get0_seed ,
-.Nm EC_GROUP_get_seed_len ,
-.Nm EC_GROUP_set_seed ,
-.Nm EC_GROUP_get_degree ,
-.Nm EC_GROUP_check ,
-.Nm EC_GROUP_check_discriminant ,
-.Nm EC_GROUP_cmp ,
-.Nm EC_GROUP_get_basis_type
-.Nd manipulate EC_GROUP objects
-.Sh SYNOPSIS
-.In openssl/ec.h
-.In openssl/bn.h
-.Ft int
-.Fo EC_GROUP_copy
-.Fa "EC_GROUP *dst"
-.Fa "const EC_GROUP *src"
-.Fc
-.Ft EC_GROUP *
-.Fo EC_GROUP_dup
-.Fa "const EC_GROUP *src"
-.Fc
-.Ft int
-.Fo EC_GROUP_set_generator
-.Fa "EC_GROUP *group"
-.Fa "const EC_POINT *generator"
-.Fa "const BIGNUM *order"
-.Fa "const BIGNUM *cofactor"
-.Fc
-.Ft const EC_POINT *
-.Fo EC_GROUP_get0_generator
-.Fa "const EC_GROUP *group"
-.Fc
-.Ft int
-.Fo EC_GROUP_get_order
-.Fa "const EC_GROUP *group"
-.Fa "BIGNUM *order"
-.Fa "BN_CTX *ctx"
-.Fc
-.Ft int
-.Fo EC_GROUP_order_bits
-.Fa "const EC_GROUP *group"
-.Fc
-.Ft int
-.Fo EC_GROUP_get_cofactor
-.Fa "const EC_GROUP *group"
-.Fa "BIGNUM *cofactor"
-.Fa "BN_CTX *ctx"
-.Fc
-.Ft void
-.Fo EC_GROUP_set_curve_name
-.Fa "EC_GROUP *group"
-.Fa "int nid"
-.Fc
-.Ft int
-.Fo EC_GROUP_get_curve_name
-.Fa "const EC_GROUP *group"
-.Fc
-.Ft void
-.Fo EC_GROUP_set_asn1_flag
-.Fa "EC_GROUP *group"
-.Fa "int flag"
-.Fc
-.Ft int
-.Fo EC_GROUP_get_asn1_flag
-.Fa "const EC_GROUP *group"
-.Fc
-.Ft void
-.Fo EC_GROUP_set_point_conversion_form
-.Fa "EC_GROUP *group"
-.Fa "point_conversion_form_t form"
-.Fc
-.Ft point_conversion_form_t
-.Fo EC_GROUP_get_point_conversion_form
-.Fa "const EC_GROUP *"
-.Fc
-.Ft unsigned char *
-.Fo EC_GROUP_get0_seed
-.Fa "const EC_GROUP *x"
-.Fc
-.Ft size_t
-.Fo EC_GROUP_get_seed_len
-.Fa "const EC_GROUP *"
-.Fc
-.Ft size_t
-.Fo EC_GROUP_set_seed
-.Fa "EC_GROUP *"
-.Fa "const unsigned char *"
-.Fa "size_t len"
-.Fc
-.Ft int
-.Fo EC_GROUP_get_degree
-.Fa "const EC_GROUP *group"
-.Fc
-.Ft int
-.Fo EC_GROUP_check
-.Fa "const EC_GROUP *group"
-.Fa "BN_CTX *ctx"
-.Fc
-.Ft int
-.Fo EC_GROUP_check_discriminant
-.Fa "const EC_GROUP *group"
-.Fa "BN_CTX *ctx"
-.Fc
-.Ft int
-.Fo EC_GROUP_cmp
-.Fa "const EC_GROUP *a"
-.Fa "const EC_GROUP *b"
-.Fa "BN_CTX *ctx"
-.Fc
-.Ft int
-.Fo EC_GROUP_get_basis_type
-.Fa "const EC_GROUP *"
-.Fc
-.Sh DESCRIPTION
-These functions operate on
-.Vt EC_GROUP
-objects created by the functions described in
-.Xr EC_GROUP_new 3 .
-.Pp
-.Fn EC_GROUP_copy
-copies the curve
-.Fa src
-into
-.Fa dst .
-Both
-.Fa src
-and
-.Fa dst
-must use the same
-.Vt EC_METHOD .
-.Pp
-.Fn EC_GROUP_dup
-creates a new
-.Vt EC_GROUP
-object and copies the content from
-.Fa src
-to the newly created
-.Vt EC_GROUP
-object.
-.Pp
-.Fn EC_GROUP_set_generator
-sets curve parameters that must be agreed by all participants using
-the curve.
-These parameters include the
-.Fa generator ,
-the
-.Fa order
-and the
-.Fa cofactor .
-The
-.Fa generator
-is a well defined point on the curve chosen for cryptographic
-operations.
-Integers used for point multiplications will be between 0 and
-.Fa order No - 1 .
-The
-.Fa order
-multiplied by the
-.Fa cofactor
-gives the number of points on the curve.
-.Pp
-.Fn EC_GROUP_get0_generator
-returns the generator for the identified
-.Fa group .
-.Pp
-.Fn EC_GROUP_get_order
-retrieves the order of the
-.Fa group
-and copies its value into
-.Fa order .
-It fails if the order of the
-.Fa group
-is not set or set to zero.
-.Pp
-.Fn EC_GROUP_get_cofactor
-retrieves the cofactor of the
-.Fa group
-and copies its value into
-.Fa cofactor .
-It fails if the cofactor of the
-.Fa group
-is not set or set to zero.
-.Pp
-The functions
-.Fn EC_GROUP_set_curve_name
-and
-.Fn EC_GROUP_get_curve_name
-set and get the NID for the curve, respectively (see
-.Xr EC_GROUP_new 3 ) .
-If a curve does not have a NID associated with it, then
-.Fn EC_GROUP_get_curve_name
-will return
-.Dv NID_undef .
-.Pp
-The asn1_flag value is used to determine whether the curve encoding
-uses explicit parameters or a named curve using an ASN.1 OID:
-many applications only support the latter form.
-If asn1_flag is the default value
-.Dv OPENSSL_EC_NAMED_CURVE ,
-then the named curve form is used and the parameters must have a
-corresponding named curve NID set.
-If asn1_flags is
-.Dv OPENSSL_EC_EXPLICIT_CURVE ,
-the parameters are explicitly encoded.
-The functions
-.Fn EC_GROUP_get_asn1_flag
-and
-.Fn EC_GROUP_set_asn1_flag
-get and set the status of the asn1_flag for the curve.
-.Pp
-The point_conversion_form for a curve controls how
-.Vt EC_POINT
-data is encoded as ASN.1 as defined in X9.62 (ECDSA).
-.Vt point_conversion_form_t
-is an enum defined as follows:
-.Bd -literal
-typedef enum {
-        /** the point is encoded as z||x, where the octet z specifies
-         *   which solution of the quadratic equation y is  */
-        POINT_CONVERSION_COMPRESSED = 2,
-        /** the point is encoded as z||x||y, where z is the octet 0x04  */
-        POINT_CONVERSION_UNCOMPRESSED = 4,
-        /** the point is encoded as z||x||y, where the octet z specifies
-         *  which solution of the quadratic equation y is  */
-        POINT_CONVERSION_HYBRID = 6
-} point_conversion_form_t;
-.Ed
-.Pp
-For
-.Dv POINT_CONVERSION_UNCOMPRESSED
-the point is encoded as an octet signifying the UNCOMPRESSED form
-has been used followed by the octets for x, followed by the octets
-for y.
-.Pp
-For any given x coordinate for a point on a curve it is possible to
-derive two possible y values.
-For
-.Dv POINT_CONVERSION_COMPRESSED
-the point is encoded as an octet signifying that the COMPRESSED
-form has been used AND which of the two possible solutions for y
-has been used, followed by the octets for x.
-.Pp
-For
-.Dv POINT_CONVERSION_HYBRID
-the point is encoded as an octet signifying the HYBRID form has
-been used AND which of the two possible solutions for y has been
-used, followed by the octets for x, followed by the octets for y.
-.Pp
-The functions
-.Fn EC_GROUP_set_point_conversion_form
-and
-.Fn EC_GROUP_get_point_conversion_form
-set and get the point_conversion_form for the curve, respectively.
-.Pp
-ANSI X9.62 (ECDSA standard) defines a method of generating the curve
-parameter b from a random number.
-This provides advantages in that a parameter obtained in this way is
-highly unlikely to be susceptible to special purpose attacks, or have
-any trapdoors in it.
-If the seed is present for a curve then the b parameter was generated in
-a verifiable fashion using that seed.
-The OpenSSL EC library does not use this seed value but does enable you
-to inspect it using
-.Fn EC_GROUP_get0_seed .
-This returns a pointer to a memory block containing the seed that was
-used.
-The length of the memory block can be obtained using
-.Fn EC_GROUP_get_seed_len .
-A number of the builtin curves within the library provide seed values
-that can be obtained.
-It is also possible to set a custom seed using
-.Fn EC_GROUP_set_seed
-and passing a pointer to a memory block, along with the length of
-the seed.
-Again, the EC library will not use this seed value, although it will be
-preserved in any ASN.1 based communications.
-.Pp
-.Fn EC_GROUP_get_degree
-gets the degree of the field.
-For Fp fields this will be the number of bits in p.
-For F2^m fields this will be the value m.
-.Pp
-The function
-.Fn EC_GROUP_check_discriminant
-calculates the discriminant for the curve and verifies that it is
-valid.
-For a curve defined over Fp the discriminant is given by the formula
-4*a^3 + 27*b^2 whilst for F2^m curves the discriminant is simply b.
-In either case for the curve to be valid the discriminant must be
-non-zero.
-.Pp
-The function
-.Fn EC_GROUP_check
-performs a number of checks on a curve to verify that it is valid.
-Checks performed include verifying that the discriminant is non-zero;
-that a generator has been defined; that the generator is on the curve
-and has the correct order.
-.Pp
-.Fn EC_GROUP_cmp
-compares
-.Fa a
-and
-.Fa b
-to determine whether they represent the same curve or not.
-.Pp
-.Fn EC_GROUP_get_basis_type
-always returns 0 and is only provided for compatibility.
-.Sh RETURN VALUES
-The following functions return 1 on success or 0 on error:
-.Fn EC_GROUP_copy ,
-.Fn EC_GROUP_set_generator ,
-.Fn EC_GROUP_check ,
-and
-.Fn EC_GROUP_check_discriminant .
-.Pp
-.Fn EC_GROUP_dup
-returns a pointer to the duplicated curve or
-.Dv NULL
-on error.
-.Pp
-.Fn EC_GROUP_get0_generator
-returns the generator for the given curve or
-.Dv NULL
-on error.
-.Pp
-.Fn EC_GROUP_get_order
-returns 0 if the order is not set or set to zero for the
-.Fa group
-or if copying into
-.Fa order
-fails, or 1 otherwise.
-.Pp
-.Fn EC_GROUP_order_bits
-returns the number of bits in the group order.
-.Pp
-.Fn EC_GROUP_get_cofactor
-returns 0 if the cofactor is not set or set to zero for the
-.Fa group
-or if copying into
-.Fa cofactor
-fails, or 1 otherwise.
-.Pp
-.Fn EC_GROUP_get_curve_name
-returns the curve name (NID) for the
-.Fa group
-or
-.Dv NID_undef
-if no curve name is associated.
-.Pp
-.Fn EC_GROUP_get_asn1_flag
-returns the ASN.1 flag for the specified
-.Fa group .
-.Pp
-.Fn EC_GROUP_get_point_conversion_form
-returns the point_conversion_form for the
-.Fa group .
-.Pp
-.Fn EC_GROUP_get_degree
-returns the degree for the
-.Fa group
-or 0 if the operation is not supported
-by the underlying group implementation.
-.Pp
-.Fn EC_GROUP_get0_seed
-returns a pointer to the seed that was used to generate the parameter
-b, or
-.Dv NULL
-if the seed is not specified.
-.Fn EC_GROUP_get_seed_len
-returns the length of the seed or 0 if the seed is not specified.
-.Pp
-.Fn EC_GROUP_set_seed
-returns the length of the seed that has been set.
-If the supplied seed is
-.Dv NULL
-or the supplied seed length is 0, the return value will be 1.
-On error 0 is returned.
-.Pp
-.Fn EC_GROUP_cmp
-returns 0 if the curves are equal, 1 if they are not equal,
-or -1 on error.
-.Pp
-.Fn EC_GROUP_get_basis_type
-always returns 0.
-.Sh SEE ALSO
-.Xr d2i_ECPKParameters 3 ,
-.Xr EC_GROUP_new 3 ,
-.Xr EC_KEY_new 3 ,
-.Xr EC_POINT_add 3 ,
-.Xr EC_POINT_new 3
-.Sh HISTORY
-.Fn EC_GROUP_copy ,
-.Fn EC_GROUP_set_generator ,
-.Fn EC_GROUP_get0_generator ,
-.Fn EC_GROUP_get_order ,
-and
-.Fn EC_GROUP_get_cofactor
-first appeared in OpenSSL 0.9.7 and have been available since
-.Ox 3.2 .
-.Pp
-.Fn EC_GROUP_dup ,
-.Fn EC_GROUP_set_curve_name ,
-.Fn EC_GROUP_get_curve_name ,
-.Fn EC_GROUP_set_asn1_flag ,
-.Fn EC_GROUP_get_asn1_flag ,
-.Fn EC_GROUP_set_point_conversion_form ,
-.Fn EC_GROUP_get_point_conversion_form ,
-.Fn EC_GROUP_get0_seed ,
-.Fn EC_GROUP_get_seed_len ,
-.Fn EC_GROUP_set_seed ,
-.Fn EC_GROUP_get_degree ,
-.Fn EC_GROUP_check ,
-.Fn EC_GROUP_check_discriminant ,
-.Fn EC_GROUP_cmp ,
-and
-.Fn EC_GROUP_get_basis_type
-first appeared in OpenSSL 0.9.8 and have been available since
-.Ox 4.5 .
-.Pp
-.Fn EC_GROUP_order_bits
-first appeared in OpenSSL 1.1.0 and has been available since
-.Ox 7.0 .