doc/man7/provider-cipher.pod - third_party/openssl - Git at Google

 =pod

 =head1 NAME

 provider-cipher - The cipher library E<lt>-E<gt> provider functions

 =head1 SYNOPSIS

 =for comment 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_cipher_newctx(void *provctx);
  void OP_cipher_freectx(void *cctx);
  void *OP_cipher_dupctx(void *cctx);

  /* Encryption/decryption */
  int OP_cipher_encrypt_init(void *cctx, const unsigned char *key,
                             size_t keylen, const unsigned char *iv,
                             size_t ivlen);
  int OP_cipher_decrypt_init(void *cctx, const unsigned char *key,
                             size_t keylen, const unsigned char *iv,
                             size_t ivlen);
  int OP_cipher_update(void *cctx, unsigned char *out, size_t *outl,
                       size_t outsize, const unsigned char *in, size_t inl);
  int OP_cipher_final(void *cctx, unsigned char *out, size_t *outl,
                      size_t outsize);
  int OP_cipher_cipher(void *cctx, unsigned char *out, size_t *outl,
                       size_t outsize, const unsigned char *in, size_t inl);

  /* Cipher parameter descriptors */
  const OSSL_PARAM *OP_cipher_gettable_params(void);

  /* Cipher operation parameter descriptors */
  const OSSL_PARAM *OP_cipher_gettable_ctx_params(void);
  const OSSL_PARAM *OP_cipher_settable_ctx_params(void);

  /* Cipher parameters */
  int OP_cipher_get_params(OSSL_PARAM params[]);

  /* Cipher operation parameters */
  int OP_cipher_get_ctx_params(void *cctx, OSSL_PARAM params[]);
  int OP_cipher_set_ctx_params(void *cctx, const OSSL_PARAM params[]);

 =head1 DESCRIPTION

 This documentation is primarily aimed at provider authors. See L<provider(7)>
 for further information.

 The CIPHER operation enables providers to implement cipher algorithms and make
 them available to applications via the API functions L<EVP_EncryptInit_ex(3)>,
 L<EVP_EncryptUpdate(3)> and L<EVP_EncryptFinal(3)> (as well as the decrypt
 equivalents and 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_cipher_newctx() has these:

  typedef void *(OSSL_OP_cipher_newctx_fn)(void *provctx);
  static ossl_inline OSSL_OP_cipher_newctx_fn
      OSSL_get_OP_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_cipher_newctx               OSSL_FUNC_CIPHER_NEWCTX
  OP_cipher_freectx              OSSL_FUNC_CIPHER_FREECTX
  OP_cipher_dupctx               OSSL_FUNC_CIPHER_DUPCTX

  OP_cipher_encrypt_init         OSSL_FUNC_CIPHER_ENCRYPT_INIT
  OP_cipher_decrypt_init         OSSL_FUNC_CIPHER_DECRYPT_INIT
  OP_cipher_update               OSSL_FUNC_CIPHER_UPDATE
  OP_cipher_final                OSSL_FUNC_CIPHER_FINAL
  OP_cipher_cipher               OSSL_FUNC_CIPHER_CIPHER

  OP_cipher_get_params           OSSL_FUNC_CIPHER_GET_PARAMS
  OP_cipher_get_ctx_params       OSSL_FUNC_CIPHER_GET_CTX_PARAMS
  OP_cipher_set_ctx_params       OSSL_FUNC_CIPHER_SET_CTX_PARAMS

  OP_cipher_gettable_params      OSSL_FUNC_CIPHER_GETTABLE_PARAMS
  OP_cipher_gettable_ctx_params  OSSL_FUNC_CIPHER_GETTABLE_CTX_PARAMS
  OP_cipher_settable_ctx_params  OSSL_FUNC_CIPHER_SETTABLE_CTX_PARAMS

 A cipher algorithm implementation may not implement all of these functions.
 In order to be a consistent set of functions there must at least be a complete
 set of "encrypt" functions, or a complete set of "decrypt" functions, or a
 single "cipher" function.
 In all cases both the OP_cipher_newctx and OP_cipher_freectx functions must be
 present.
 All other functions are optional.

 =head2 Context Management Functions

 OP_cipher_newctx() should create and return a pointer to a provider side
 structure for holding context information during a cipher operation.
 A pointer to this context will be passed back in a number of the other cipher
 operation function calls.
 The parameter B<provctx> is the provider context generated during provider
 initialisation (see L<provider(3)>).

 OP_cipher_freectx() is passed a pointer to the provider side cipher context in
 the B<cctx> parameter.
 This function should free any resources associated with that context.

 OP_cipher_dupctx() should duplicate the provider side cipher context in the
 B<cctx> parameter and return the duplicate copy.

 =head2 Encryption/Decryption Functions

 OP_cipher_encrypt_init() initialises a cipher operation for encryption given a
 newly created provider side cipher context in the B<cctx> parameter.
 The key to be used is given in B<key> which is B<keylen> bytes long.
 The IV to be used is given in B<iv> which is B<ivlen> bytes long.

 OP_cipher_decrypt_init() is the same as OP_cipher_encrypt_init() except that it
 initialises the context for a decryption operation.

 OP_cipher_update() is called to supply data to be encrypted/decrypted as part of
 a previously initialised cipher operation.
 The B<cctx> parameter contains a pointer to a previously initialised provider
 side context.
 OP_cipher_update() should encrypt/decrypt B<inl> bytes of data at the location
 pointed to by B<in>.
 The encrypted data should be stored in B<out> and the amount of data written to
 B<*outl> which should not exceed B<outsize> bytes.
 OP_cipher_update() may be called multiple times for a single cipher operation.
 It is the responsibility of the cipher implementation to handle input lengths
 that are not multiples of the block length.
 In such cases a cipher implementation will typically cache partial blocks of
 input data until a complete block is obtained.
 B<out> may be the same location as B<in> but it should not partially overlap.
 The same expectations apply to B<outsize> as documented for
 L<EVP_EncryptUpdate(3)> and L<EVP_DecryptUpdate(3)>.

 OP_cipher_final() completes an encryption or decryption started through previous
 OP_cipher_encrypt_init() or OP_cipher_decrypt_init(), and OP_cipher_update()
 calls.
 The B<cctx> parameter contains a pointer to the provider side context.
 Any final encryption/decryption output should be written to B<out> and the
 amount of data written to B<*outl> which should not exceed B<outsize> bytes.
 The same expectations apply to B<outsize> as documented for
 L<EVP_EncryptFinal(3)> and L<EVP_DecryptFinal(3)>.

 OP_cipher_cipher() performs encryption/decryption using the provider side cipher
 context in the B<cctx> parameter that should have been previously initialised via
 a call to OP_cipher_encrypt_init() or OP_cipher_decrypt_init.
 This should call the raw underlying cipher function without any padding.
 This will be invoked in the provider as a result of the application calling
 L<EVP_Cipher(3)>.
 The application is responsible for ensuring that the input is a multiple of the
 block length.
 The data to be encrypted/decrypted will be in B<in>, and it will be B<inl> bytes
 in length.
 The output from the encryption/decryption should be stored in B<out> and the
 amount of data stored should be put in B<*outl> which should be no more than
 B<outsize> bytes.

 =head2 Cipher Parameters

 See L<OSSL_PARAM(3)> for further details on the parameters structure used by
 these functions.

 OP_cipher_get_params() gets details of the algorithm implementation
 and stores them in B<params>.

 OP_cipher_set_ctx_params() sets cipher operation parameters for the
 provider side cipher context B<cctx> to B<params>.
 Any parameter settings are additional to any that were previously set.

 OP_cipher_get_ctx_params() gets cipher operation details details from
 the given provider side cipher context B<cctx> and stores them in B<params>.

 OP_cipher_gettable_params(), OP_cipher_gettable_ctx_params(), and
 OP_cipher_settable_ctx_params() all return constant B<OSSL_PARAM> arrays
 as descriptors of the parameters that OP_cipher_get_params(),
 OP_cipher_get_ctx_params(), and OP_cipher_set_ctx_params() can handle,
 respectively.

 Parameters currently recognised by built-in ciphers are as follows. Not all
 parameters are relevant to, or are understood by all ciphers:

 =over 4

 =item B<OSSL_CIPHER_PARAM_PADDING> (uint)

 Sets the padding mode for the associated cipher ctx.
 Setting a value of 1 will turn padding on.
 Setting a value of 0 will turn padding off.

 =item B<OSSL_CIPHER_PARAM_MODE> (uint)

 Gets the mode for the associated cipher algorithm.
 See L<EVP_CIPHER_mode(3)> for a list of valid modes.

 =item B<OSSL_CIPHER_PARAM_BLOCK_SIZE> (size_t)

 Gets the block size for the associated cipher algorithm.
 The block size should be 1 for stream ciphers.
 Note that the block size for a cipher may be different to the block size for
 the underlying encryption/decryption primitive.
 For example AES in CTR mode has a block size of 1 (because it operates like a
 stream cipher), even though AES has a block size of 16.

 =item B<OSSL_CIPHER_PARAM_FLAGS> (ulong)

 Gets any flags for the associated cipher algorithm.
 See L<EVP_CIPHER_meth_set_flags(3)> for a list of currently defined cipher
 flags.

 =item B<OSSL_CIPHER_PARAM_KEYLEN> (size_t)

 Gets the key length for the associated cipher algorithm.
 This can also be used to get or set the key length for the associated cipher
 ctx.

 =item B<OSSL_CIPHER_PARAM_IVLEN> (size_t)

 Gets the IV length for the associated cipher algorithm.

 =item B<OSSL_CIPHER_PARAM_IV> (octet_string OR octet_ptr)

 Gets the IV for the associated cipher ctx.

 =item B<OSSL_CIPHER_PARAM_NUM> (uint)

 Gets or sets the cipher specific "num" parameter for the associated cipher ctx.
 Built-in ciphers typically use this to track how much of the current underlying
 block has been "used" already.

 =item B<OSSL_CIPHER_PARAM_AEAD_TAG> (octet_string)

 Gets or sets the AEAD tag for the associated cipher ctx.
 See L<EVP_EncryptInit(3)/AEAD Interface>.

 =item B<OSSL_CIPHER_PARAM_AEAD_TAGLEN> (size_t)

 Gets the tag length to be used for an AEAD cipher for the associated cipher ctx.
 It returns a default value if it has not been set.

 =item B<OSSL_CIPHER_PARAM_AEAD_TLS1_AAD> (octet_string)

 =for comment TODO(3.0): Consider changing this interface so that all ciphers
 use the standard AEAD interface - rather than having this special purpose
 interface for TLS

 Sets TLSv1.2 AAD information for the associated cipher ctx.
 TLSv1.2 AAD information is always 13 bytes in length and is as defined for the
 "additional_data" field described in section 6.2.3.3 of RFC5246.

 =item B<OSSL_CIPHER_PARAM_AEAD_TLS1_AAD_PAD> (size_t)

 Gets the length of the tag that will be added to a TLS record for the AEAD
 tag for the associated cipher ctx.

 =item B<OSSL_CIPHER_PARAM_AEAD_TLS1_IV_FIXED> (octet_string)

 =for comment TODO(3.0): This interface needs completely redesigning!

 Sets the fixed portion of an IV for an AEAD cipher used in a TLS record
 encryption/ decryption for the associated cipher ctx.
 TLS record encryption/decryption always occurs "in place" so that the input and
 output buffers are always the same memory location.
 AEAD IVs in TLSv1.2 consist of an implicit "fixed" part and an explicit part
 that varies with every record.
 Setting a TLS fixed IV changes a cipher to encrypt/decrypt TLS records.
 TLS records are encrypted/decrypted using a single OP_cipher_cipher call per
 record.
 For a record decryption the first bytes of the input buffer will be the explict
 part of the IV and the final bytes of the input buffer will be the AEAD tag.
 The length of the explicit part of the IV and the tag length will depend on the
 cipher in use and will be defined in the RFC for the relevant ciphersuite.
 In order to allow for "in place" decryption the plaintext output should be
 written to the same location in the output buffer that the ciphertext payload
 was read from, i.e. immediately after the explicit IV.

 When encrypting a record the first bytes of the input buffer will be empty to
 allow space for the explicit IV, as will the final bytes where the tag will
 be written.
 The length of the input buffer will include the length of the explicit IV, the
 payload, and the tag bytes.
 The cipher implementation should generate the explicit IV and write it to the
 beginning of the output buffer, do "in place" encryption of the payload and
 write that to the output buffer, and finally add the tag onto the end of the
 output buffer.

 Whether encrypting or decrypting the value written to B<*outl> in the
 OP_cipher_cipher call should be the length of the payload excluding the explicit
 IV length and the tag length.

 =item B<OSSL_CIPHER_PARAM_AEAD_IVLEN> (size_t)

 Sets the IV length to be used for an AEAD cipher for the associated cipher ctx.

 =item B<OSSL_CIPHER_PARAM_RANDOM_KEY> (octet_string)

 Gets a implementation specific randomly generated key for the associated
 cipher ctx. This is currently only supported by 3DES (which sets the key to
 odd parity).

 =back

 =head1 RETURN VALUES

 OP_cipher_newctx() and OP_cipher_dupctx() should return the newly created
 provider side cipher context, or NULL on failure.

 OP_cipher_encrypt_init(), OP_cipher_decrypt_init(), OP_cipher_update(),
 OP_cipher_final(), OP_cipher_cipher(), OP_cipher_get_params(),
 OP_cipher_get_ctx_params() and OP_cipher_set_ctx_params() should return 1 for
 success or 0 on error.

 OP_cipher_gettable_params(), OP_cipher_gettable_ctx_params() and
 OP_cipher_settable_ctx_params() should return a constant B<OSSL_PARAM>
 array, or NULL if none is offered.

 =head1 SEE ALSO

 L<provider(7)>

 =head1 HISTORY

 The provider 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
	=pod

	=head1 NAME

	provider-cipher - The cipher library E<lt>-E<gt> provider functions

	=head1 SYNOPSIS

	=for comment 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_cipher_newctx(void provctx);
	void OP_cipher_freectx(void *cctx);
	void OP_cipher_dupctx(void cctx);

	/* Encryption/decryption */
	int OP_cipher_encrypt_init(void cctx, const unsigned char key,
	size_t keylen, const unsigned char *iv,
	size_t ivlen);
	int OP_cipher_decrypt_init(void cctx, const unsigned char key,
	size_t keylen, const unsigned char *iv,
	size_t ivlen);
	int OP_cipher_update(void cctx, unsigned char out, size_t *outl,
	size_t outsize, const unsigned char *in, size_t inl);
	int OP_cipher_final(void cctx, unsigned char out, size_t *outl,
	size_t outsize);
	int OP_cipher_cipher(void cctx, unsigned char out, size_t *outl,
	size_t outsize, const unsigned char *in, size_t inl);

	/* Cipher parameter descriptors */
	const OSSL_PARAM *OP_cipher_gettable_params(void);

	/* Cipher operation parameter descriptors */
	const OSSL_PARAM *OP_cipher_gettable_ctx_params(void);
	const OSSL_PARAM *OP_cipher_settable_ctx_params(void);

	/* Cipher parameters */
	int OP_cipher_get_params(OSSL_PARAM params[]);

	/* Cipher operation parameters */
	int OP_cipher_get_ctx_params(void *cctx, OSSL_PARAM params[]);
	int OP_cipher_set_ctx_params(void *cctx, const OSSL_PARAM params[]);

	=head1 DESCRIPTION

	This documentation is primarily aimed at provider authors. See L<provider(7)>
	for further information.

	The CIPHER operation enables providers to implement cipher algorithms and make
	them available to applications via the API functions L<EVP_EncryptInit_ex(3)>,
	L<EVP_EncryptUpdate(3)> and L<EVP_EncryptFinal(3)> (as well as the decrypt
	equivalents and 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_cipher_newctx() has these:

	typedef void (OSSL_OP_cipher_newctx_fn)(void provctx);
	static ossl_inline OSSL_OP_cipher_newctx_fn
	OSSL_get_OP_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_cipher_newctx OSSL_FUNC_CIPHER_NEWCTX
	OP_cipher_freectx OSSL_FUNC_CIPHER_FREECTX
	OP_cipher_dupctx OSSL_FUNC_CIPHER_DUPCTX

	OP_cipher_encrypt_init OSSL_FUNC_CIPHER_ENCRYPT_INIT
	OP_cipher_decrypt_init OSSL_FUNC_CIPHER_DECRYPT_INIT
	OP_cipher_update OSSL_FUNC_CIPHER_UPDATE
	OP_cipher_final OSSL_FUNC_CIPHER_FINAL
	OP_cipher_cipher OSSL_FUNC_CIPHER_CIPHER

	OP_cipher_get_params OSSL_FUNC_CIPHER_GET_PARAMS
	OP_cipher_get_ctx_params OSSL_FUNC_CIPHER_GET_CTX_PARAMS
	OP_cipher_set_ctx_params OSSL_FUNC_CIPHER_SET_CTX_PARAMS

	OP_cipher_gettable_params OSSL_FUNC_CIPHER_GETTABLE_PARAMS
	OP_cipher_gettable_ctx_params OSSL_FUNC_CIPHER_GETTABLE_CTX_PARAMS
	OP_cipher_settable_ctx_params OSSL_FUNC_CIPHER_SETTABLE_CTX_PARAMS

	A cipher algorithm implementation may not implement all of these functions.
	In order to be a consistent set of functions there must at least be a complete
	set of "encrypt" functions, or a complete set of "decrypt" functions, or a
	single "cipher" function.
	In all cases both the OP_cipher_newctx and OP_cipher_freectx functions must be
	present.
	All other functions are optional.

	=head2 Context Management Functions

	OP_cipher_newctx() should create and return a pointer to a provider side
	structure for holding context information during a cipher operation.
	A pointer to this context will be passed back in a number of the other cipher
	operation function calls.
	The parameter B<provctx> is the provider context generated during provider
	initialisation (see L<provider(3)>).

	OP_cipher_freectx() is passed a pointer to the provider side cipher context in
	the B<cctx> parameter.
	This function should free any resources associated with that context.

	OP_cipher_dupctx() should duplicate the provider side cipher context in the
	B<cctx> parameter and return the duplicate copy.

	=head2 Encryption/Decryption Functions

	OP_cipher_encrypt_init() initialises a cipher operation for encryption given a
	newly created provider side cipher context in the B<cctx> parameter.
	The key to be used is given in B<key> which is B<keylen> bytes long.
	The IV to be used is given in B<iv> which is B<ivlen> bytes long.

	OP_cipher_decrypt_init() is the same as OP_cipher_encrypt_init() except that it
	initialises the context for a decryption operation.

	OP_cipher_update() is called to supply data to be encrypted/decrypted as part of
	a previously initialised cipher operation.
	The B<cctx> parameter contains a pointer to a previously initialised provider
	side context.
	OP_cipher_update() should encrypt/decrypt B<inl> bytes of data at the location
	pointed to by B<in>.
	The encrypted data should be stored in B<out> and the amount of data written to
	B<*outl> which should not exceed B<outsize> bytes.
	OP_cipher_update() may be called multiple times for a single cipher operation.
	It is the responsibility of the cipher implementation to handle input lengths
	that are not multiples of the block length.
	In such cases a cipher implementation will typically cache partial blocks of
	input data until a complete block is obtained.
	B<out> may be the same location as B<in> but it should not partially overlap.
	The same expectations apply to B<outsize> as documented for
	L<EVP_EncryptUpdate(3)> and L<EVP_DecryptUpdate(3)>.

	OP_cipher_final() completes an encryption or decryption started through previous
	OP_cipher_encrypt_init() or OP_cipher_decrypt_init(), and OP_cipher_update()
	calls.
	The B<cctx> parameter contains a pointer to the provider side context.
	Any final encryption/decryption output should be written to B<out> and the
	amount of data written to B<*outl> which should not exceed B<outsize> bytes.
	The same expectations apply to B<outsize> as documented for
	L<EVP_EncryptFinal(3)> and L<EVP_DecryptFinal(3)>.

	OP_cipher_cipher() performs encryption/decryption using the provider side cipher
	context in the B<cctx> parameter that should have been previously initialised via
	a call to OP_cipher_encrypt_init() or OP_cipher_decrypt_init.
	This should call the raw underlying cipher function without any padding.
	This will be invoked in the provider as a result of the application calling
	L<EVP_Cipher(3)>.
	The application is responsible for ensuring that the input is a multiple of the
	block length.
	The data to be encrypted/decrypted will be in B<in>, and it will be B<inl> bytes
	in length.
	The output from the encryption/decryption should be stored in B<out> and the
	amount of data stored should be put in B<*outl> which should be no more than
	B<outsize> bytes.

	=head2 Cipher Parameters

	See L<OSSL_PARAM(3)> for further details on the parameters structure used by
	these functions.

	OP_cipher_get_params() gets details of the algorithm implementation
	and stores them in B<params>.

	OP_cipher_set_ctx_params() sets cipher operation parameters for the
	provider side cipher context B<cctx> to B<params>.
	Any parameter settings are additional to any that were previously set.

	OP_cipher_get_ctx_params() gets cipher operation details details from
	the given provider side cipher context B<cctx> and stores them in B<params>.

	OP_cipher_gettable_params(), OP_cipher_gettable_ctx_params(), and
	OP_cipher_settable_ctx_params() all return constant B<OSSL_PARAM> arrays
	as descriptors of the parameters that OP_cipher_get_params(),
	OP_cipher_get_ctx_params(), and OP_cipher_set_ctx_params() can handle,
	respectively.

	Parameters currently recognised by built-in ciphers are as follows. Not all
	parameters are relevant to, or are understood by all ciphers:

	=over 4

	=item B<OSSL_CIPHER_PARAM_PADDING> (uint)

	Sets the padding mode for the associated cipher ctx.
	Setting a value of 1 will turn padding on.
	Setting a value of 0 will turn padding off.

	=item B<OSSL_CIPHER_PARAM_MODE> (uint)

	Gets the mode for the associated cipher algorithm.
	See L<EVP_CIPHER_mode(3)> for a list of valid modes.

	=item B<OSSL_CIPHER_PARAM_BLOCK_SIZE> (size_t)

	Gets the block size for the associated cipher algorithm.
	The block size should be 1 for stream ciphers.
	Note that the block size for a cipher may be different to the block size for
	the underlying encryption/decryption primitive.
	For example AES in CTR mode has a block size of 1 (because it operates like a
	stream cipher), even though AES has a block size of 16.

	=item B<OSSL_CIPHER_PARAM_FLAGS> (ulong)

	Gets any flags for the associated cipher algorithm.
	See L<EVP_CIPHER_meth_set_flags(3)> for a list of currently defined cipher
	flags.

	=item B<OSSL_CIPHER_PARAM_KEYLEN> (size_t)

	Gets the key length for the associated cipher algorithm.
	This can also be used to get or set the key length for the associated cipher
	ctx.

	=item B<OSSL_CIPHER_PARAM_IVLEN> (size_t)

	Gets the IV length for the associated cipher algorithm.

	=item B<OSSL_CIPHER_PARAM_IV> (octet_string OR octet_ptr)

	Gets the IV for the associated cipher ctx.

	=item B<OSSL_CIPHER_PARAM_NUM> (uint)

	Gets or sets the cipher specific "num" parameter for the associated cipher ctx.
	Built-in ciphers typically use this to track how much of the current underlying
	block has been "used" already.

	=item B<OSSL_CIPHER_PARAM_AEAD_TAG> (octet_string)

	Gets or sets the AEAD tag for the associated cipher ctx.
	See L<EVP_EncryptInit(3)/AEAD Interface>.

	=item B<OSSL_CIPHER_PARAM_AEAD_TAGLEN> (size_t)

	Gets the tag length to be used for an AEAD cipher for the associated cipher ctx.
	It returns a default value if it has not been set.

	=item B<OSSL_CIPHER_PARAM_AEAD_TLS1_AAD> (octet_string)

	=for comment TODO(3.0): Consider changing this interface so that all ciphers
	use the standard AEAD interface - rather than having this special purpose
	interface for TLS

	Sets TLSv1.2 AAD information for the associated cipher ctx.
	TLSv1.2 AAD information is always 13 bytes in length and is as defined for the
	"additional_data" field described in section 6.2.3.3 of RFC5246.

	=item B<OSSL_CIPHER_PARAM_AEAD_TLS1_AAD_PAD> (size_t)

	Gets the length of the tag that will be added to a TLS record for the AEAD
	tag for the associated cipher ctx.

	=item B<OSSL_CIPHER_PARAM_AEAD_TLS1_IV_FIXED> (octet_string)

	=for comment TODO(3.0): This interface needs completely redesigning!

	Sets the fixed portion of an IV for an AEAD cipher used in a TLS record
	encryption/ decryption for the associated cipher ctx.
	TLS record encryption/decryption always occurs "in place" so that the input and
	output buffers are always the same memory location.
	AEAD IVs in TLSv1.2 consist of an implicit "fixed" part and an explicit part
	that varies with every record.
	Setting a TLS fixed IV changes a cipher to encrypt/decrypt TLS records.
	TLS records are encrypted/decrypted using a single OP_cipher_cipher call per
	record.
	For a record decryption the first bytes of the input buffer will be the explict
	part of the IV and the final bytes of the input buffer will be the AEAD tag.
	The length of the explicit part of the IV and the tag length will depend on the
	cipher in use and will be defined in the RFC for the relevant ciphersuite.
	In order to allow for "in place" decryption the plaintext output should be
	written to the same location in the output buffer that the ciphertext payload
	was read from, i.e. immediately after the explicit IV.

	When encrypting a record the first bytes of the input buffer will be empty to
	allow space for the explicit IV, as will the final bytes where the tag will
	be written.
	The length of the input buffer will include the length of the explicit IV, the
	payload, and the tag bytes.
	The cipher implementation should generate the explicit IV and write it to the
	beginning of the output buffer, do "in place" encryption of the payload and
	write that to the output buffer, and finally add the tag onto the end of the
	output buffer.

	Whether encrypting or decrypting the value written to B<*outl> in the
	OP_cipher_cipher call should be the length of the payload excluding the explicit
	IV length and the tag length.

	=item B<OSSL_CIPHER_PARAM_AEAD_IVLEN> (size_t)

	Sets the IV length to be used for an AEAD cipher for the associated cipher ctx.

	=item B<OSSL_CIPHER_PARAM_RANDOM_KEY> (octet_string)

	Gets a implementation specific randomly generated key for the associated
	cipher ctx. This is currently only supported by 3DES (which sets the key to
	odd parity).

	=back

	=head1 RETURN VALUES

	OP_cipher_newctx() and OP_cipher_dupctx() should return the newly created
	provider side cipher context, or NULL on failure.

	OP_cipher_encrypt_init(), OP_cipher_decrypt_init(), OP_cipher_update(),
	OP_cipher_final(), OP_cipher_cipher(), OP_cipher_get_params(),
	OP_cipher_get_ctx_params() and OP_cipher_set_ctx_params() should return 1 for
	success or 0 on error.

	OP_cipher_gettable_params(), OP_cipher_gettable_ctx_params() and
	OP_cipher_settable_ctx_params() should return a constant B<OSSL_PARAM>
	array, or NULL if none is offered.

	=head1 SEE ALSO

	L<provider(7)>

	=head1 HISTORY

	The provider 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