=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 4

=over 4

=item The cipher modes:

=over 4

=item EVP_CIPH_STREAM_CIPHER

=item EVP_CIPH_ECB_MODE

=item EVP_CIPH_CBC_MODE

=item EVP_CIPH_CFB_MODE

=item EVP_CIPH_OFB_MODE

=item EVP_CIPH_CTR_MODE

=item EVP_CIPH_GCM_MODE

=item EVP_CIPH_CCM_MODE

=item EVP_CIPH_XTS_MODE

=item EVP_CIPH_WRAP_MODE

=item EVP_CIPH_OCB_MODE

=back

=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 a AEAD cipher implementation.

=item EVP_CIPH_FLAG_TLS1_1_MULTIBLOCK

=begin comment

I could use some help explaining this one!

=end comment

=back

=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>.


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.

=cut