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Add documentation for the Asymmetric Cipher Operation

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Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/10152)
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Matt Caswell 2019-10-29 09:24:24 +00:00
parent 89abd1b6f4
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doc/man7/provider-asymcipher.pod Normal file
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=pod
=head1 NAME
provider-asym_cipher - The asym_cipher library E<lt>-E<gt> provider functions
=head1 SYNOPSIS
=for openssl multiple includes
#include <openssl/core_numbers.h>
#include <openssl/core_names.h>
/*
* None of these are actual functions, but are displayed like this for
* the function signatures for functions that are offered as function
* pointers in OSSL_DISPATCH arrays.
*/
/* Context management */
void *OP_asym_cipher_newctx(void *provctx);
void OP_asym_cipher_freectx(void *ctx);
void *OP_asym_cipher_dupctx(void *ctx);
/* Encryption */
int OP_asym_cipher_encrypt_init(void *ctx, void *provkey);
int OP_asym_cipher_encrypt(void *ctx, unsigned char *out, size_t *outlen,
size_t outsize, const unsigned char *in,
size_t inlen);
/* Decryption */
int OP_asym_cipher_decrypt_init(void *ctx, void *provkey);
int OP_asym_cipher_decrypt(void *ctx, unsigned char *out, size_t *outlen,
size_t outsize, const unsigned char *in,
size_t inlen);
/* Asymmetric Cipher parameters */
int OP_asym_cipher_get_ctx_params(void *ctx, OSSL_PARAM params[]);
const OSSL_PARAM *OP_asym_cipher_gettable_ctx_params(void);
int OP_asym_cipher_set_ctx_params(void *ctx, const OSSL_PARAM params[]);
const OSSL_PARAM *OP_asym_cipher_settable_ctx_params(void);
=head1 DESCRIPTION
This documentation is primarily aimed at provider authors. See L<provider(7)>
for further information.
The asymmetric cipher (OSSL_OP_ASYM_CIPHER) operation enables providers to
implement asymmetric cipher algorithms and make them available to applications
via the API functions L<EVP_PKEY_encrypt_init_ex(3)>, L<EVP_PKEY_encrypt(3)>,
L<EVP_PKEY_decrypt_init_ex(3)>, L<EVP_PKEY_decrypt(3)> (as well
as other related functions).
All "functions" mentioned here are passed as function pointers between
F<libcrypto> and the provider in B<OSSL_DISPATCH> arrays via
B<OSSL_ALGORITHM> arrays that are returned by the provider's
provider_query_operation() function
(see L<provider-base(7)/Provider Functions>).
All these "functions" have a corresponding function type definition
named B<OSSL_{name}_fn>, and a helper function to retrieve the
function pointer from an B<OSSL_DISPATCH> element named
B<OSSL_get_{name}>.
For example, the "function" OP_asym_cipher_newctx() has these:
typedef void *(OSSL_OP_asym_cipher_newctx_fn)(void *provctx);
static ossl_inline OSSL_OP_asym_cipher_newctx_fn
OSSL_get_OP_asym_cipher_newctx(const OSSL_DISPATCH *opf);
B<OSSL_DISPATCH> arrays are indexed by numbers that are provided as
macros in L<openssl-core_numbers.h(7)>, as follows:
OP_asym_cipher_newctx OSSL_FUNC_ASYM_CIPHER_NEWCTX
OP_asym_cipher_freectx OSSL_FUNC_ASYM_CIPHER_FREECTX
OP_asym_cipher_dupctx OSSL_FUNC_ASYM_CIPHER_DUPCTX
OP_asym_cipher_encrypt_init OSSL_FUNC_ASYM_CIPHER_ENCRYPT_INIT
OP_asym_cipher_encrypt OSSL_FUNC_ASYM_CIPHER_ENCRYPT
OP_asym_cipher_decrypt_init OSSL_FUNC_ASYM_CIPHER_DECRYPT_INIT
OP_asym_cipher_decrypt OSSL_FUNC_ASYM_CIPHER_DECRYPT
OP_asym_cipher_get_ctx_params OSSL_FUNC_ASYM_CIPHER_GET_CTX_PARAMS
OP_asym_cipher_gettable_ctx_params OSSL_FUNC_ASYM_CIPHER_GETTABLE_CTX_PARAMS
OP_asym_cipher_set_ctx_params OSSL_FUNC_ASYM_CIPHER_SET_CTX_PARAMS
OP_asym_cipher_settable_ctx_params OSSL_FUNC_ASYM_CIPHER_SETTABLE_CTX_PARAMS
An asymmetric cipher algorithm implementation may not implement all of these
functions.
In order to be a consistent set of functions a provider must implement
OP_asym_cipher_newctx and OP_asym_cipher_freectx.
It must also implement both of OP_asym_cipher_encrypt_init and
OP_asym_cipher_encrypt, or both of OP_asym_cipher_decrypt_init and
OP_asym_cipher_decrypt.
OP_asym_cipher_get_ctx_params is optional but if it is present then so must
OP_asym_cipher_gettable_ctx_params.
Similarly, OP_asym_cipher_set_ctx_params is optional but if it is present then
so must OP_asym_cipher_settable_ctx_params.
An asymmetric cipher algorithm must also implement some mechanism for generating,
loading or importing keys via the key management (OSSL_OP_KEYMGMT) operation.
See L<provider-keymgmt(7)> for further details.
=head2 Context Management Functions
OP_asym_cipher_newctx() should create and return a pointer to a provider side
structure for holding context information during an asymmetric cipher operation.
A pointer to this context will be passed back in a number of the other
asymmetric cipher operation function calls.
The parameter I<provctx> is the provider context generated during provider
initialisation (see L<provider(3)>).
OP_asym_cipher_freectx() is passed a pointer to the provider side asymmetric
cipher context in the I<ctx> parameter.
This function should free any resources associated with that context.
OP_asym_cipher_dupctx() should duplicate the provider side asymmetric cipher
context in the I<ctx> parameter and return the duplicate copy.
=head2 Encryption Functions
OP_asym_cipher_encrypt_init() initialises a context for an asymmetric encryption
given a provider side asymmetric cipher context in the I<ctx> parameter, and a
pointer to a provider key object in the I<provkey> parameter.
The key object should have been previously generated, loaded or imported into
the provider using the key management (OSSL_OP_KEYMGMT) operation (see
provider-keymgmt(7)>.
OP_asym_cipher_encrypt() performs the actual encryption itself.
A previously initialised asymmetric cipher context is passed in the I<ctx>
parameter.
The data to be encrypted is pointed to by the I<in> parameter which is I<inlen>
bytes long.
Unless I<out> is NULL, the encrypted data should be written to the location
pointed to by the I<out> parameter and it should not exceed I<outsize> bytes in
length.
The length of the encrypted data should be written to I<*outlen>.
If I<out> is NULL then the maximum length of the encrypted data should be
written to I<*outlen>.
=head2 Decryption Functions
OP_asym_cipher_decrypt_init() initialises a context for an asymmetric decryption
given a provider side asymmetric cipher context in the I<ctx> parameter, and a
pointer to a provider key object in the I<provkey> parameter.
The key object should have been previously generated, loaded or imported into
the provider using the key management (OSSL_OP_KEYMGMT) operation (see
provider-keymgmt(7)>.
OP_asym_cipher_decrypt() performs the actual decryption itself.
A previously initialised asymmetric cipher context is passed in the I<ctx>
parameter.
The data to be decrypted is pointed to by the I<in> parameter which is I<inlen>
bytes long.
Unless I<out> is NULL, the decrypted data should be written to the location
pointed to by the I<out> parameter and it should not exceed I<outsize> bytes in
length.
The length of the decrypted data should be written to I<*outlen>.
If I<out> is NULL then the maximum length of the decrypted data should be
written to I<*outlen>.
=head2 Asymmetric Cipher Parameters
See L<OSSL_PARAM(3)> for further details on the parameters structure used by
the OP_asym_cipher_get_ctx_params() and OP_asym_cipher_set_ctx_params()
functions.
OP_asym_cipher_get_ctx_params() gets asymmetric cipher parameters associated
with the given provider side asymmetric cipher context I<ctx> and stores them in
I<params>.
OP_asym_cipher_set_ctx_params() sets the asymmetric cipher parameters associated
with the given provider side asymmetric cipher context I<ctx> to I<params>.
Any parameter settings are additional to any that were previously set.
Parameters currently recognised by built-in asymmetric cipher algorithms are as
follows.
Not all parameters are relevant to, or are understood by all asymmetric cipher
algorithms:
=over 4
=item "pad-mode" (B<OSSL_ASYM_CIPHER_PARAM_PAD_MODE>) <integer>
=item "digest" (B<OSSL_ASYM_CIPHER_PARAM_OAEP_DIGEST>) <UTF8 string>
Gets or sets the name of the OAEP digest algorithm used when OAEP padding is in
use.
=item "digest-props" (B<OSSL_ASYM_CIPHER_PARAM_OAEP_DIGEST_PROPS>) <UTF8 string>
Gets or sets the properties to use when fetching the OAEP digest algorithm.
=item "mgf1-digest" (B<OSSL_ASYM_CIPHER_PARAM_MGF1_DIGEST>) <UTF8 string>
Gets or sets the name of the MGF1 digest algorithm used when OAEP or PSS padding
is in use.
=item "mgf1-digest-props" (B<OSSL_ASYM_CIPHER_PARAM_MGF1_DIGEST_PROPS>) <UTF8 string>
Gets or sets the properties to use when fetching the MGF1 digest algorithm.
=item "oaep-label" (B<OSSL_ASYM_CIPHER_PARAM_OAEP_LABEL>) <octet string>
Gets or sets the OAEP label used when OAEP padding is in use.
=item "oaep-label-len" (B<OSSL_ASYM_CIPHER_PARAM_OAEP_LABEL_LEN>) <size_t>
Gets the length of an OAEP label when OAEP padding is in use.
=back
OP_asym_cipher_gettable_ctx_params() and OP_asym_cipher_settable_ctx_params()
get a constant B<OSSL_PARAM> array that describes the gettable and settable
parameters, i.e. parameters that can be used with OP_asym_cipherget_ctx_params()
and OP_asym_cipher_set_ctx_params() respectively.
See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as parameter descriptor.
=head1 RETURN VALUES
OP_asym_cipher_newctx() and OP_asym_cipher_dupctx() should return the newly
created provider side asymmetric cipher context, or NULL on failure.
All other functions should return 1 for success or 0 on error.
=head1 SEE ALSO
L<provider(7)>
=head1 HISTORY
The provider ASYM_CIPHER interface was introduced in OpenSSL 3.0.
=head1 COPYRIGHT
Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
L<https://www.openssl.org/source/license.html>.
=cut