Document the provider CIPHER operation

Extends the existing provider documentation with information about the
CIPHER operation. This is primarily for provider authors.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/9473)

crypto/evp/evp_enc.c

@@ -1216,9 +1216,8 @@ static void *evp_cipher_from_dispatch(const char *name,
         /*
          * In order to be a consistent set of functions we must have at least
          * a complete set of "encrypt" functions, or a complete set of "decrypt"
-         * functions, or a single "cipher" function. In all cases we need a
+         * functions, or a single "cipher" function. In all cases we need both
-         * complete set of context management functions, as well as the
+         * the "newctx" and "freectx" functions.
-         * blocksize, iv_length and key_length functions.
          */
         EVP_CIPHER_meth_free(cipher);
         EVPerr(EVP_F_EVP_CIPHER_FROM_DISPATCH, EVP_R_INVALID_PROVIDER_FUNCTIONS);

doc/man3/EVP_EncryptInit.pod

@@ -278,8 +278,11 @@ an B<EVP_CIPHER_CTX> structure.
 EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher mode:
 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 or EVP_CIPH_OCB_MODE. If the cipher is a stream cipher then
+EVP_CIPH_WRAP_MODE, EVP_CIPH_OCB_MODE or EVP_CIPH_SIV_MODE. If the cipher is a
-EVP_CIPH_STREAM_CIPHER is returned.
+stream cipher then EVP_CIPH_STREAM_CIPHER is returned.
+
+EVP_CIPHER_flags() returns any flags associated with the cipher. See
+EVP_CIPHER_meth_set_flags() for a list of currently defined flags.
 
 EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based
 on the passed cipher. This will typically include any parameters and an

doc/man7/provider-cipher.pod

@@ -0,0 +1,316 @@
+=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 parameters */
+ int OP_cipher_get_params(OSSL_PARAM params[]);
+ int OP_cipher_ctx_get_params(void *cctx, OSSL_PARAM params[]);
+ int OP_cipher_ctx_set_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_ctx_get_params    OSSL_FUNC_CIPHER_CTX_GET_PARAMS
+ OP_cipher_ctx_set_params    OSSL_FUNC_CIPHER_CTX_SET_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 paramater 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> paramter.
+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> paramter 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 parameter values associated with the
+provider algorithm and stores them in B<params>.
+
+OP_cipher_ctx_set_params() sets cipher parameters associated with the given
+provider side cipher context B<cctx> to B<params>.
+Any parameter settings are additional to any that were previously set.
+
+OP_cipher_ctx_get_params() gets details of currently set parameter values
+associated with the given provider side cipher context B<cctx> and stores them
+in B<params>.
+
+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> (int)
+
+Sets the padding mode for the associated cipher ctx.
+Setting a value of 1 will turn padding on.
+Setting a vlue of 0 will turn padding off.
+
+=item B<OSSL_CIPHER_PARAM_MODE> (int)
+
+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> (int)
+
+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> (int)
+
+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> (int)
+
+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> (int)
+
+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_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.
+
+=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_ctx_get_params() and OP_cipher_ctx_set_params() should return 1 for
+success or 0 on error.
+
+=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