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

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);

DESCRIPTION

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

EVP_CIPHER_meth_new() creates a new EVP_CIPHER structure.

EVP_CIPHER_meth_dup() creates a copy of cipher.

EVP_CIPHER_meth_free() destroys a EVP_CIPHER structure.

EVP_CIPHER_meth_set_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 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:

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.
EVP_CIPH_VARIABLE_LENGTH: This cipher is of variable length.
EVP_CIPH_CUSTOM_IV: Storing and initialising the IV is left entirely to the implementation.
EVP_CIPH_ALWAYS_CALL_INIT: Set this if the implementation's init() function should be called even if key is NULL.
EVP_CIPH_CTRL_INIT: Set this to have the implementation's ctrl() function called with command code EVP_CTRL_INIT early in its setup.
EVP_CIPH_CUSTOM_KEY_LENGTH: Checking and setting the key length after creating the EVP_CIPHER is left to the implementation. Whenever someone uses EVP_CIPHER_CTX_set_key_length() on a EVP_CIPHER with this flag set, the implementation's ctrl() function will be called with the control code EVP_CTRL_SET_KEY_LENGTH and the key length in arg.
EVP_CIPH_NO_PADDING: Don't use standard block padding.
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 EVP_CTRL_RAND_KEY and the pointer to the key memory storage in ptr.
EVP_CIPH_CUSTOM_COPY: Set this to have the implementation's ctrl() function called with command code 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 EVP_CIPHER_CTX is passed to the control with the ptr parameter. The implementation specific data block is reached with EVP_CIPHER_CTX_get_cipher_data().
EVP_CIPH_FLAG_DEFAULT_ASN1: Use the default EVP routines to pass IV to and from ASN.1.
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 instead of bytes for this implementation. This is only useful for CFB1 ciphers.
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.
EVP_CIPH_FLAG_AEAD_CIPHER: This indicates that this is an AEAD cipher implementation.
EVP_CIPH_FLAG_TLS1_1_MULTIBLOCK: Allow interleaving of crypto blocks, a particular optimization only applicable to certain TLS ciphers.

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 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 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 cipher to do extra cleanup before the method's private data structure is cleaned out and freed. Note that the cleanup function is passed a 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_set_asn1_params() sets the function for cipher to set the AlgorithmIdentifier "parameter" based on the passed cipher. This function is called by EVP_CIPHER_param_to_asn1(). EVP_CIPHER_meth_set_get_asn1_params() sets the function for cipher that sets the cipher parameters based on an ASN.1 AlgorithmIdentifier "parameter". Both these functions are needed when there is a need for custom data (more or other than the cipher IV). They are called by EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() respectively if defined.

EVP_CIPHER_meth_set_ctrl() sets the control function for cipher.

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() and EVP_CIPHER_meth_get_ctrl() are all used to retrieve the method data given with the EVP_CIPHER_meth_set_*() functions above.

RETURN VALUES

EVP_CIPHER_meth_new() and EVP_CIPHER_meth_dup() return a pointer to a newly created EVP_CIPHER, or NULL on failure. All EVP_CIPHER_meth_set_*() functions return 1. All EVP_CIPHER_meth_get_*() functions return pointers to their respective cipher function.

HISTORY

The functions described here were added in OpenSSL 1.1.0.

COPYRIGHT

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 <https://www.openssl.org/source/license.html>.

2022-06-24