=pod

=head1 NAME

EVP_CIPHER_meth_new, EVP_CIPHER_meth_dup, EVP_CIPHER_meth_free,
EVP_CIPHER_meth_set_iv_length, EVP_CIPHER_meth_set_flags,
EVP_CIPHER_meth_set_impl_ctx_size, EVP_CIPHER_meth_set_init,
EVP_CIPHER_meth_set_do_cipher, EVP_CIPHER_meth_set_cleanup,
EVP_CIPHER_meth_set_set_asn1_params, EVP_CIPHER_meth_set_get_asn1_params,
EVP_CIPHER_meth_set_ctrl, EVP_CIPHER_meth_get_init,
EVP_CIPHER_meth_get_do_cipher, EVP_CIPHER_meth_get_cleanup,
EVP_CIPHER_meth_get_set_asn1_params, EVP_CIPHER_meth_get_get_asn1_params,
EVP_CIPHER_meth_get_ctrl  - Routines to build up EVP_CIPHER methods

=head1 SYNOPSIS

 #include <openssl/evp.h>

 EVP_CIPHER *EVP_CIPHER_meth_new(int cipher_type, int block_size, int key_len);
 EVP_CIPHER *EVP_CIPHER_meth_dup(const EVP_CIPHER *cipher);
 void EVP_CIPHER_meth_free(EVP_CIPHER *cipher);

 int EVP_CIPHER_meth_set_iv_length(EVP_CIPHER *cipher, int iv_len);
 int EVP_CIPHER_meth_set_flags(EVP_CIPHER *cipher, unsigned long flags);
 int EVP_CIPHER_meth_set_impl_ctx_size(EVP_CIPHER *cipher, int ctx_size);
 int EVP_CIPHER_meth_set_init(EVP_CIPHER *cipher,
                              int (*init) (EVP_CIPHER_CTX *ctx,
                                           const unsigned char *key,
                                           const unsigned char *iv,
                                           int enc));
 int EVP_CIPHER_meth_set_do_cipher(EVP_CIPHER *cipher,
                                   int (*do_cipher) (EVP_CIPHER_CTX *ctx,
                                                     unsigned char *out,
                                                     const unsigned char *in,
                                                     size_t inl));
 int EVP_CIPHER_meth_set_cleanup(EVP_CIPHER *cipher,
                                 int (*cleanup) (EVP_CIPHER_CTX *));
 int EVP_CIPHER_meth_set_set_asn1_params(EVP_CIPHER *cipher,
                                         int (*set_asn1_parameters) (EVP_CIPHER_CTX *,
                                                                     ASN1_TYPE *));
 int EVP_CIPHER_meth_set_get_asn1_params(EVP_CIPHER *cipher,
                                         int (*get_asn1_parameters) (EVP_CIPHER_CTX *,
                                                                     ASN1_TYPE *));
 int EVP_CIPHER_meth_set_ctrl(EVP_CIPHER *cipher,
                              int (*ctrl) (EVP_CIPHER_CTX *, int type,
                                           int arg, void *ptr));

 int (*EVP_CIPHER_meth_get_init(const EVP_CIPHER *cipher))(EVP_CIPHER_CTX *ctx,
                                                           const unsigned char *key,
                                                           const unsigned char *iv,
                                                           int enc);
 int (*EVP_CIPHER_meth_get_do_cipher(const EVP_CIPHER *cipher))(EVP_CIPHER_CTX *ctx,
                                                                unsigned char *out,
                                                                const unsigned char *in,
                                                                size_t inl);
 int (*EVP_CIPHER_meth_get_cleanup(const EVP_CIPHER *cipher))(EVP_CIPHER_CTX *);
 int (*EVP_CIPHER_meth_get_set_asn1_params(const EVP_CIPHER *cipher))(EVP_CIPHER_CTX *,
                                                                      ASN1_TYPE *);
 int (*EVP_CIPHER_meth_get_get_asn1_params(const EVP_CIPHER *cipher))(EVP_CIPHER_CTX *,
                                                                ASN1_TYPE *);
 int (*EVP_CIPHER_meth_get_ctrl(const EVP_CIPHER *cipher))(EVP_CIPHER_CTX *,
                                                           int type, int arg,
                                                           void *ptr);

=head1 DESCRIPTION

The B<EVP_CIPHER> type is a structure for symmetric cipher method
implementation.

EVP_CIPHER_meth_new() creates a new B<EVP_CIPHER> structure.

EVP_CIPHER_meth_dup() creates a copy of B<cipher>.

EVP_CIPHER_meth_free() destroys a B<EVP_CIPHER> structure.

EVP_CIPHER_meth_iv_length() sets the length of the IV.
This is only needed when the implemented cipher mode requires it.

EVP_CIPHER_meth_set_flags() sets the flags to describe optional
behaviours in the particular B<cipher>.
With the exception of cipher modes, of which only one may be present,
several flags can be or'd together.
The available flags are:

=over

=item EVP_CIPH_STREAM_CIPHER, EVP_CIPH_ECB_MODE EVP_CIPH_CBC_MODE,
EVP_CIPH_CFB_MODE, EVP_CIPH_OFB_MODE, EVP_CIPH_CTR_MODE, EVP_CIPH_GCM_MODE,
EVP_CIPH_CCM_MODE, EVP_CIPH_XTS_MODE, EVP_CIPH_WRAP_MODE,
EVP_CIPH_OCB_MODE

The cipher mode.

=item EVP_CIPH_VARIABLE_LENGTH

This cipher is of variable length.

=item EVP_CIPH_CUSTOM_IV

Storing and initialising the IV is left entirely to the
implementation.

=item EVP_CIPH_ALWAYS_CALL_INIT

Set this if the implementation's init() function should be called even
if B<key> is B<NULL>.

=item EVP_CIPH_CTRL_INIT

Set this to have the implementation's ctrl() function called with
command code B<EVP_CTRL_INIT> early in its setup.

=item EVP_CIPH_CUSTOM_KEY_LENGTH

Checking and setting the key length after creating the B<EVP_CIPHER>
is left to the implementation.
Whenever someone uses EVP_CIPHER_CTX_set_key_length() on a
B<EVP_CIPHER> with this flag set, the implementation's ctrl() function
will be called with the control code B<EVP_CTRL_SET_KEY_LENGTH> and
the key length in B<arg>.

=item EVP_CIPH_NO_PADDING

Don't use standard block padding.

=item EVP_CIPH_RAND_KEY

Making a key with random content is left to the implementation.
This is done by calling the implementation's ctrl() function with the
control code B<EVP_CTRL_RAND_KEY> and the pointer to the key memory
storage in B<ptr>.

=item EVP_CIPH_CUSTOM_COPY

Set this to have the implementation's ctrl() function called with
command code B<EVP_CTRL_COPY> at the end of EVP_CIPHER_CTX_copy().
The intended use is for further things to deal with after the
implementation specific data block has been copied.
The destination B<EVP_CIPHER_CTX> is passed to the control with the
B<ptr> parameter.
The implementation specific data block is reached with
EVP_CIPHER_CTX_get_cipher_data().

=item EVP_CIPH_FLAG_DEFAULT_ASN1

Use the default EVP routines to pass IV to and from ASN.1.

=item EVP_CIPH_FLAG_LENGTH_BITS

Signals that the length of the input buffer for encryption /
decryption is to be understood as the number of bits bits instead of
bytes for this implementation.
This is only useful for CFB1 ciphers.

=begin comment
The FIPS flags seem to be unused, so I'm hiding them until I get an
explanation or they get removed.  /RL

=item EVP_CIPH_FLAG_FIPS

=item EVP_CIPH_FLAG_NON_FIPS_ALLOW

=end comment

=item EVP_CIPH_FLAG_CUSTOM_CIPHER

This indicates that the implementation takes care of everything,
including padding, buffering and finalization.
The EVP routines will simply give them control and do nothing more.

=item EVP_CIPH_FLAG_AEAD_CIPHER

This indicates that this is an AEAD cipher implementation.

=item EVP_CIPH_FLAG_TLS1_1_MULTIBLOCK

Allow interleaving of crypto blocks, a particular optimization only applicable
to certain TLS ciphers.

=back

EVP_CIPHER_meth_set_impl_ctx_size() sets the size of the EVP_CIPHER's
implementation context so that it can be automatically allocated.

EVP_CIPHER_meth_set_init() sets the cipher init function for
B<cipher>.
The cipher init function is called by EVP_CipherInit(),
EVP_CipherInit_ex(), EVP_EncryptInit(), EVP_EncryptInit_ex(),
EVP_DecryptInit(), EVP_DecryptInit_ex().

EVP_CIPHER_meth_set_do_cipher() sets the cipher function for
B<cipher>.
The cipher function is called by EVP_CipherUpdate(),
EVP_EncryptUpdate(), EVP_DecryptUpdate(), EVP_CipherFinal(),
EVP_EncryptFinal(), EVP_EncryptFinal_ex(), EVP_DecryptFinal() and
EVP_DecryptFinal_ex().

EVP_CIPHER_meth_set_cleanup() sets the function for B<cipher> to do
extra cleanup before the method's privata data structure is cleaned
out and freed.
Note that the cleanup function is passed a B<EVP_CIPHER_CTX *>, the
private data structure is then available with
EVP_CIPHER_CTX_get_cipher_data().
This cleanup function is called by EVP_CIPHER_CTX_reset() and
EVP_CIPHER_CTX_free().

EVP_CIPHER_meth_set_ctrl() sets the control function for B<cipher>.

=head1 RETURN VALUES

EVP_CIPHER_meth_get_input_blocksize(), EVP_CIPHER_meth_get_result_size(),
EVP_CIPHER_meth_get_app_datasize(), EVP_CIPHER_meth_get_flags(),
EVP_CIPHER_meth_get_init(), EVP_CIPHER_meth_get_update(),
EVP_CIPHER_meth_get_final(), EVP_CIPHER_meth_get_copy(),
EVP_CIPHER_meth_get_cleanup() and EVP_CIPHER_meth_get_ctrl() are all used
to retrieve the method data given with the EVP_CIPHER_meth_set_*()
functions above.

=head1 SEE ALSO

L<EVP_EncryptInit>

=head1 HISTORY

The B<EVP_CIPHER> structure was openly available in OpenSSL before version
1.1.
The functions described here were added in OpenSSL version 1.1.

=head1 COPYRIGHT

Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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