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)
This commit is contained in:
Matt Caswell
parent
d753cc333d
commit
11dbdc0714
3 changed files with 323 additions and 5 deletions
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@ -1216,9 +1216,8 @@ static void *evp_cipher_from_dispatch(const char *name,
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/*
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* In order to be a consistent set of functions we must have at least
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* a complete set of "encrypt" functions, or a complete set of "decrypt"
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* functions, or a single "cipher" function. In all cases we need a
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* complete set of context management functions, as well as the
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* blocksize, iv_length and key_length functions.
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* functions, or a single "cipher" function. In all cases we need both
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* the "newctx" and "freectx" functions.
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*/
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EVP_CIPHER_meth_free(cipher);
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EVPerr(EVP_F_EVP_CIPHER_FROM_DISPATCH, EVP_R_INVALID_PROVIDER_FUNCTIONS);
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@ -278,8 +278,11 @@ an B<EVP_CIPHER_CTX> structure.
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EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher mode:
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EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE, EVP_CIPH_OFB_MODE,
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EVP_CIPH_CTR_MODE, EVP_CIPH_GCM_MODE, EVP_CIPH_CCM_MODE, EVP_CIPH_XTS_MODE,
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EVP_CIPH_WRAP_MODE or EVP_CIPH_OCB_MODE. If the cipher is a stream cipher then
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EVP_CIPH_STREAM_CIPHER is returned.
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EVP_CIPH_WRAP_MODE, EVP_CIPH_OCB_MODE or EVP_CIPH_SIV_MODE. If the cipher is a
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stream cipher then EVP_CIPH_STREAM_CIPHER is returned.
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EVP_CIPHER_flags() returns any flags associated with the cipher. See
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EVP_CIPHER_meth_set_flags() for a list of currently defined flags.
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EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based
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on the passed cipher. This will typically include any parameters and an
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316
doc/man7/provider-cipher.pod
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316
doc/man7/provider-cipher.pod
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@ -0,0 +1,316 @@
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=pod
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=head1 NAME
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provider-cipher - The cipher library E<lt>-E<gt> provider functions
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=head1 SYNOPSIS
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=for comment multiple includes
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#include <openssl/core_numbers.h>
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#include <openssl/core_names.h>
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/*
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* None of these are actual functions, but are displayed like this for
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* the function signatures for functions that are offered as function
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* pointers in OSSL_DISPATCH arrays.
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*/
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/* Context management */
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void *OP_cipher_newctx(void *provctx);
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void OP_cipher_freectx(void *cctx);
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void *OP_cipher_dupctx(void *cctx);
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/* Encryption/decryption */
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int OP_cipher_encrypt_init(void *cctx, const unsigned char *key,
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size_t keylen, const unsigned char *iv,
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size_t ivlen);
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int OP_cipher_decrypt_init(void *cctx, const unsigned char *key,
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size_t keylen, const unsigned char *iv,
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size_t ivlen);
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int OP_cipher_update(void *cctx, unsigned char *out, size_t *outl,
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size_t outsize, const unsigned char *in, size_t inl);
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int OP_cipher_final(void *cctx, unsigned char *out, size_t *outl,
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size_t outsize);
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int OP_cipher_cipher(void *cctx, unsigned char *out, size_t *outl,
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size_t outsize, const unsigned char *in, size_t inl);
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/* Cipher parameters */
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int OP_cipher_get_params(OSSL_PARAM params[]);
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int OP_cipher_ctx_get_params(void *cctx, OSSL_PARAM params[]);
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int OP_cipher_ctx_set_params(void *cctx, const OSSL_PARAM params[]);
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=head1 DESCRIPTION
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This documentation is primarily aimed at provider authors. See L<provider(7)>
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for further information.
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The CIPHER operation enables providers to implement cipher algorithms and make
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them available to applications via the API functions L<EVP_EncryptInit_ex(3)>,
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L<EVP_EncryptUpdate(3)> and L<EVP_EncryptFinal(3)> (as well as the decrypt
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equivalents and other related functions).
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All "functions" mentioned here are passed as function pointers between
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F<libcrypto> and the provider in B<OSSL_DISPATCH> arrays via
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B<OSSL_ALGORITHM> arrays that are returned by the provider's
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provider_query_operation() function
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(see L<provider-base(7)/Provider Functions>).
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All these "functions" have a corresponding function type definition
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named B<OSSL_{name}_fn>, and a helper function to retrieve the
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function pointer from an B<OSSL_DISPATCH> element named
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B<OSSL_get_{name}>.
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For example, the "function" OP_cipher_newctx() has these:
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typedef void *(OSSL_OP_cipher_newctx_fn)(void *provctx);
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static ossl_inline OSSL_OP_cipher_newctx_fn
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OSSL_get_OP_cipher_newctx(const OSSL_DISPATCH *opf);
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B<OSSL_DISPATCH> arrays are indexed by numbers that are provided as
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macros in L<openssl-core_numbers.h(7)>, as follows:
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OP_cipher_newctx OSSL_FUNC_CIPHER_NEWCTX
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OP_cipher_freectx OSSL_FUNC_CIPHER_FREECTX
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OP_cipher_dupctx OSSL_FUNC_CIPHER_DUPCTX
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OP_cipher_encrypt_init OSSL_FUNC_CIPHER_ENCRYPT_INIT
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OP_cipher_decrypt_init OSSL_FUNC_CIPHER_DECRYPT_INIT
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OP_cipher_update OSSL_FUNC_CIPHER_UPDATE
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OP_cipher_final OSSL_FUNC_CIPHER_FINAL
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OP_cipher_cipher OSSL_FUNC_CIPHER_CIPHER
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OP_cipher_get_params OSSL_FUNC_CIPHER_GET_PARAMS
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OP_cipher_ctx_get_params OSSL_FUNC_CIPHER_CTX_GET_PARAMS
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OP_cipher_ctx_set_params OSSL_FUNC_CIPHER_CTX_SET_PARAMS
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A cipher algorithm implementation may not implement all of these functions.
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In order to be a consistent set of functions there must at least be a complete
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set of "encrypt" functions, or a complete set of "decrypt" functions, or a
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single "cipher" function.
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In all cases both the OP_cipher_newctx and OP_cipher_freectx functions must be
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present.
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All other functions are optional.
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=head2 Context Management Functions
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OP_cipher_newctx() should create and return a pointer to a provider side
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structure for holding context information during a cipher operation.
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A pointer to this context will be passed back in a number of the other cipher
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operation function calls.
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The paramater B<provctx> is the provider context generated during provider
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initialisation (see L<provider(3)>).
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OP_cipher_freectx() is passed a pointer to the provider side cipher context in
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the B<cctx> parameter.
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This function should free any resources associated with that context.
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OP_cipher_dupctx() should duplicate the provider side cipher context in the
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B<cctx> parameter and return the duplicate copy.
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=head2 Encryption/Decryption Functions
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OP_cipher_encrypt_init() initialises a cipher operation for encryption given a
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newly created provider side cipher context in the B<cctx> paramter.
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The key to be used is given in B<key> which is B<keylen> bytes long.
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The IV to be used is given in B<iv> which is B<ivlen> bytes long.
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OP_cipher_decrypt_init() is the same as OP_cipher_encrypt_init() except that it
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initialises the context for a decryption operation.
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OP_cipher_update() is called to supply data to be encrypted/decrypted as part of
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a previously initialised cipher operation.
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The B<cctx> parameter contains a pointer to a previously initialised provider
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side context.
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OP_cipher_update() should encrypt/decrypt B<inl> bytes of data at the location
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pointed to by B<in>.
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The encrypted data should be stored in B<out> and the amount of data written to
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B<*outl> which should not exceed B<outsize> bytes.
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OP_cipher_update() may be called multiple times for a single cipher operation.
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It is the responsibility of the cipher implementation to handle input lengths
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that are not multiples of the block length.
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In such cases a cipher implementation will typically cache partial blocks of
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input data until a complete block is obtained.
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B<out> may be the same location as B<in> but it should not partially overlap.
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The same expectations apply to B<outsize> as documented for
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L<EVP_EncryptUpdate(3)> and L<EVP_DecryptUpdate(3)>.
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OP_cipher_final() completes an encryption or decryption started through previous
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OP_cipher_encrypt_init() or OP_cipher_decrypt_init(), and OP_cipher_update()
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calls.
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The B<cctx> parameter contains a pointer to the provider side context.
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Any final encryption/decryption output should be written to B<out> and the
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amount of data written to B<*outl> which should not exceed B<outsize> bytes.
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The same expectations apply to B<outsize> as documented for
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L<EVP_EncryptFinal(3)> and L<EVP_DecryptFinal(3)>.
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OP_cipher_cipher() performs encryption/decryption using the provider side cipher
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context in the B<cctx> paramter that should have been previously initialised via
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a call to OP_cipher_encrypt_init() or OP_cipher_decrypt_init.
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This should call the raw underlying cipher function without any padding.
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This will be invoked in the provider as a result of the application calling
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L<EVP_Cipher(3)>.
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The application is responsible for ensuring that the input is a multiple of the
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block length.
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The data to be encrypted/decrypted will be in B<in>, and it will be B<inl> bytes
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in length.
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The output from the encryption/decryption should be stored in B<out> and the
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amount of data stored should be put in B<*outl> which should be no more than
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B<outsize> bytes.
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=head2 Cipher Parameters
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See L<OSSL_PARAM(3)> for further details on the parameters structure used by
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these functions.
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OP_cipher_get_params() gets details of parameter values associated with the
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provider algorithm and stores them in B<params>.
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OP_cipher_ctx_set_params() sets cipher parameters associated with the given
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provider side cipher context B<cctx> to B<params>.
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Any parameter settings are additional to any that were previously set.
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OP_cipher_ctx_get_params() gets details of currently set parameter values
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associated with the given provider side cipher context B<cctx> and stores them
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in B<params>.
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Parameters currently recognised by built-in ciphers are as follows. Not all
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parameters are relevant to, or are understood by all ciphers:
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=over 4
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=item B<OSSL_CIPHER_PARAM_PADDING> (int)
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Sets the padding mode for the associated cipher ctx.
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Setting a value of 1 will turn padding on.
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Setting a vlue of 0 will turn padding off.
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=item B<OSSL_CIPHER_PARAM_MODE> (int)
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Gets the mode for the associated cipher algorithm.
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See L<EVP_CIPHER_mode(3)> for a list of valid modes.
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=item B<OSSL_CIPHER_PARAM_BLOCK_SIZE> (int)
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Gets the block size for the associated cipher algorithm.
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The block size should be 1 for stream ciphers.
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Note that the block size for a cipher may be different to the block size for
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the underlying encryption/decryption primitive.
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For example AES in CTR mode has a block size of 1 (because it operates like a
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stream cipher), even though AES has a block size of 16.
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=item B<OSSL_CIPHER_PARAM_FLAGS> (ulong)
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Gets any flags for the associated cipher algorithm.
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See L<EVP_CIPHER_meth_set_flags(3)> for a list of currently defined cipher
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flags.
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=item B<OSSL_CIPHER_PARAM_KEYLEN> (int)
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Gets the key length for the associated cipher algorithm.
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This can also be used to get or set the key length for the associated cipher
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ctx.
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=item B<OSSL_CIPHER_PARAM_IVLEN> (int)
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Gets the IV length for the associated cipher algorithm.
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=item B<OSSL_CIPHER_PARAM_IV> (octet_string OR octet_ptr)
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Gets the IV for the associated cipher ctx.
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=item B<OSSL_CIPHER_PARAM_NUM> (int)
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Gets or sets the cipher specific "num" parameter for the associated cipher ctx.
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Built-in ciphers typically use this to track how much of the current underlying
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block has been "used" already.
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=item B<OSSL_CIPHER_PARAM_AEAD_TAG> (octet_string)
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Gets or sets the AEAD tag for the associated cipher ctx.
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See L<EVP_EncryptInit(3)/AEAD Interface>.
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=item B<OSSL_CIPHER_PARAM_AEAD_TLS1_AAD> (octet_string)
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=for comment TODO(3.0): Consider changing this interface so that all ciphers
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use the standard AEAD interface - rather than having this special purpose
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interface for TLS
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Sets TLSv1.2 AAD information for the associated cipher ctx.
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TLSv1.2 AAD information is always 13 bytes in length and is as defined for the
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"additional_data" field described in section 6.2.3.3 of RFC5246.
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=item B<OSSL_CIPHER_PARAM_AEAD_TLS1_AAD_PAD> (size_t)
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Gets the length of the tag that will be added to a TLS record for the AEAD
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tag for the associated cipher ctx.
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=item B<OSSL_CIPHER_PARAM_AEAD_TLS1_IV_FIXED> (octet_string)
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=for comment TODO(3.0): This interface needs completely redesigning!
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Sets the fixed portion of an IV for an AEAD cipher used in a TLS record
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encryption/ decryption for the associated cipher ctx.
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TLS record encryption/decryption always occurs "in place" so that the input and
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output buffers are always the same memory location.
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AEAD IVs in TLSv1.2 consist of an implicit "fixed" part and an explicit part
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that varies with every record.
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Setting a TLS fixed IV changes a cipher to encrypt/decrypt TLS records.
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TLS records are encrypted/decrypted using a single OP_cipher_cipher call per
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record.
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For a record decryption the first bytes of the input buffer will be the explict
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part of the IV and the final bytes of the input buffer will be the AEAD tag.
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The length of the explicit part of the IV and the tag length will depend on the
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cipher in use and will be defined in the RFC for the relevant ciphersuite.
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In order to allow for "in place" decryption the plaintext output should be
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written to the same location in the output buffer that the ciphertext payload
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was read from, i.e. immediately after the explicit IV.
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When encrypting a record the first bytes of the input buffer will be empty to
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allow space for the explicit IV, as will the final bytes where the tag will
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be written.
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The length of the input buffer will include the length of the explicit IV, the
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payload, and the tag bytes.
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The cipher implementation should generate the explicit IV and write it to the
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beginning of the output buffer, do "in place" encryption of the payload and
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write that to the output buffer, and finally add the tag onto the end of the
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output buffer.
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Whether encrypting or decrypting the value written to B<*outl> in the
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OP_cipher_cipher call should be the length of the payload excluding the explicit
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IV length and the tag length.
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=item B<OSSL_CIPHER_PARAM_AEAD_IVLEN> (size_t)
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Sets the IV length to be used for an AEAD cipher for the associated cipher ctx.
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=back
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=head1 RETURN VALUES
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OP_cipher_newctx() and OP_cipher_dupctx() should return the newly created
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provider side cipher context, or NULL on failure.
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OP_cipher_encrypt_init(), OP_cipher_decrypt_init(), OP_cipher_update(),
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OP_cipher_final(), OP_cipher_cipher(), OP_cipher_get_params(),
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OP_cipher_ctx_get_params() and OP_cipher_ctx_set_params() should return 1 for
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success or 0 on error.
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=head1 SEE ALSO
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L<provider(7)>
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=head1 HISTORY
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The provider CIPHER interface was introduced in OpenSSL 3.0.
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=head1 COPYRIGHT
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Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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