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78c44b0594
The code is derived from @sftcd's work in PR #17172. This PR puts the DHKEM algorithms into the provider layer as KEM algorithms for EC and ECX. This PR only implements the DHKEM component of HPKE as specified in RFC 9180. crypto/hpke/hpke_util.c has been added for fuctions that will be shared between DHKEM and HPKE. API's for EVP_PKEY_auth_encapsulate_init() and EVP_PKEY_auth_decapsulate_init() have been added to support authenticated encapsulation. auth_init() functions were chosen rather that a EVP_PKEY_KEM_set_auth() interface to support future algorithms that could possibly need different init functions. Internal code has been refactored, so that it can be shared between the DHKEM and other systems. Since DHKEM operates on low level keys it needs to be able to do low level ECDH and ECXDH calls without converting the keys back into EVP_PKEY/EVP_PKEY_CTX form. See ossl_ecx_compute_key(), ossl_ec_public_from_private() DHKEM requires API's to derive a key using a seed (IKM). This did not sit well inside the DHKEM itself as dispatch functions. This functionality fits better inside the EC and ECX keymanagers keygen, since they are just variations of keygen where the private key is generated in a different manner. This should mainly be used for testing purposes. See ossl_ec_generate_key_dhkem(). It supports this by allowing a settable param to be passed to keygen (See OSSL_PKEY_PARAM_DHKEM_IKM). The keygen calls code within ec and ecx dhkem implementation to handle this. See ossl_ecx_dhkem_derive_private() and ossl_ec_dhkem_derive_private(). These 2 functions are also used by the EC/ECX DHKEM implementations to generate the sender ephemeral keys. Reviewed-by: Hugo Landau <hlandau@openssl.org> Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from https://github.com/openssl/openssl/pull/19068)
112 lines
3.7 KiB
Plaintext
112 lines
3.7 KiB
Plaintext
=pod
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=head1 NAME
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EVP_PKEY_encapsulate_init, EVP_PKEY_auth_encapsulate_init, EVP_PKEY_encapsulate
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- Key encapsulation using a public key algorithm
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=head1 SYNOPSIS
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#include <openssl/evp.h>
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int EVP_PKEY_encapsulate_init(EVP_PKEY_CTX *ctx, const OSSL_PARAM params[]);
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int EVP_PKEY_auth_encapsulate_init(EVP_PKEY_CTX *ctx, EVP_PKEY *authpriv,
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const OSSL_PARAM params[]);
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int EVP_PKEY_encapsulate(EVP_PKEY_CTX *ctx,
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unsigned char *out, size_t *outlen,
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unsigned char *genkey, size_t *genkeylen);
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=head1 DESCRIPTION
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The EVP_PKEY_encapsulate_init() function initializes a public key algorithm
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context I<ctx> for an encapsulation operation and then sets the I<params>
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on the context in the same way as calling L<EVP_PKEY_CTX_set_params(3)>.
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The EVP_PKEY_auth_encapsulate_init() function is similiar to
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EVP_PKEY_encapsulate_init() but also passes an I<authpriv> authentication private
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key that is used during encapsulation.
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The EVP_PKEY_encapsulate() function performs a public key encapsulation
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operation using I<ctx> with the name I<name>.
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If I<out> is B<NULL> then the maximum size of the output buffer is written to the
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I<*outlen> parameter and the maximum size of the generated key buffer is written
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to I<*genkeylen>. If I<out> is not B<NULL> and the call is successful then the
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internally generated key is written to I<genkey> and its size is written to
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I<*genkeylen>. The encapsulated version of the generated key is written to
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I<out> and its size is written to I<*outlen>.
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=head1 NOTES
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After the call to EVP_PKEY_encapsulate_init() algorithm specific parameters
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for the operation may be set or modified using L<EVP_PKEY_CTX_set_params(3)>.
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=head1 RETURN VALUES
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EVP_PKEY_encapsulate_init(), EVP_PKEY_auth_encapsulate_init() and
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EVP_PKEY_encapsulate() return 1 for success and 0 or a negative value for
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failure. In particular a return value of -2 indicates the operation is not
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supported by the public key algorithm.
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=head1 EXAMPLES
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Encapsulate an RSASVE key (for RSA keys).
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#include <openssl/evp.h>
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/*
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* NB: assumes rsa_pub_key is an public key of another party.
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*/
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EVP_PKEY_CTX *ctx = NULL;
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size_t secretlen = 0, outlen = 0;
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unsigned char *out = NULL, *secret = NULL;
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ctx = EVP_PKEY_CTX_new_from_pkey(libctx, rsa_pub_key, NULL);
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if (ctx = NULL)
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/* Error */
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if (EVP_PKEY_encapsulate_init(ctx, NULL) <= 0)
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/* Error */
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/* Set the mode - only 'RSASVE' is currently supported */
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if (EVP_PKEY_CTX_set_kem_op(ctx, "RSASVE") <= 0)
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/* Error */
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/* Determine buffer length */
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if (EVP_PKEY_encapsulate(ctx, NULL, &outlen, NULL, &secretlen) <= 0)
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/* Error */
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out = OPENSSL_malloc(outlen);
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secret = OPENSSL_malloc(secretlen);
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if (out == NULL || secret == NULL)
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/* malloc failure */
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/*
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* The generated 'secret' can be used as key material.
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* The encapsulated 'out' can be sent to another party who can
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* decapsulate it using their private key to retrieve the 'secret'.
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*/
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if (EVP_PKEY_encapsulate(ctx, out, &outlen, secret, &secretlen) <= 0)
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/* Error */
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=head1 SEE ALSO
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L<EVP_PKEY_CTX_new(3)>,
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L<EVP_PKEY_decapsulate(3)>,
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L<EVP_KEM-RSA(7)>, L<EVP_KEM-X25519(7)>, L<EVP_KEM-EC(7)>
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=head1 HISTORY
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These functions EVP_PKEY_encapsulate_init() and EVP_PKEY_encapsulate() were
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added in OpenSSL 3.0.
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The function EVP_PKEY_auth_encapsulate_init() was added in OpenSSL 3.1.
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=head1 COPYRIGHT
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Copyright 2020-2022 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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