mirror of https://github.com/openssl/openssl.git
270 lines
9.6 KiB
Plaintext
270 lines
9.6 KiB
Plaintext
=pod
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=head1 NAME
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EVP_KDF, EVP_KDF_fetch, EVP_KDF_free, EVP_KDF_up_ref,
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EVP_KDF_CTX, EVP_KDF_CTX_new, EVP_KDF_CTX_free, EVP_KDF_CTX_dup,
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EVP_KDF_reset, EVP_KDF_derive,
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EVP_KDF_size, EVP_KDF_provider, EVP_KDF_CTX_kdf, EVP_KDF_is_a,
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EVP_KDF_number, EVP_KDF_names_do_all,
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EVP_KDF_CTX_get_params, EVP_KDF_CTX_set_params, EVP_KDF_do_all_provided,
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EVP_KDF_get_params, EVP_KDF_gettable_ctx_params, EVP_KDF_settable_ctx_params,
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EVP_KDF_gettable_params - EVP KDF routines
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=head1 SYNOPSIS
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#include <openssl/kdf.h>
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typedef struct evp_kdf_st EVP_KDF;
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typedef struct evp_kdf_ctx_st EVP_KDF_CTX;
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EVP_KDF_CTX *EVP_KDF_CTX_new(const EVP_KDF *kdf);
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const EVP_KDF *EVP_KDF_CTX_kdf(EVP_KDF_CTX *ctx);
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void EVP_KDF_CTX_free(EVP_KDF_CTX *ctx);
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EVP_KDF_CTX *EVP_KDF_CTX_dup(const EVP_KDF_CTX *src);
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void EVP_KDF_reset(EVP_KDF_CTX *ctx);
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size_t EVP_KDF_size(EVP_KDF_CTX *ctx);
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int EVP_KDF_derive(EVP_KDF_CTX *ctx, unsigned char *key, size_t keylen);
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int EVP_KDF_up_ref(EVP_KDF *kdf);
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void EVP_KDF_free(EVP_KDF *kdf);
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EVP_KDF *EVP_KDF_fetch(OPENSSL_CTX *libctx, const char *algorithm,
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const char *properties);
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int EVP_KDF_number(const EVP_KDF *kdf);
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int EVP_KDF_is_a(const EVP_KDF *kdf, const char *name);
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const OSSL_PROVIDER *EVP_KDF_provider(const EVP_KDF *kdf);
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void EVP_KDF_do_all_provided(OPENSSL_CTX *libctx,
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void (*fn)(EVP_KDF *kdf, void *arg),
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void *arg);
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void EVP_KDF_names_do_all(const EVP_KDF *kdf,
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void (*fn)(const char *name, void *data),
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void *data);
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int EVP_KDF_get_params(EVP_KDF *kdf, OSSL_PARAM params[]);
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int EVP_KDF_CTX_get_params(EVP_KDF_CTX *ctx, OSSL_PARAM params[]);
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int EVP_KDF_CTX_set_params(EVP_KDF_CTX *ctx, const OSSL_PARAM params[]);
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const OSSL_PARAM *EVP_KDF_gettable_params(const EVP_KDF *kdf);
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const OSSL_PARAM *EVP_KDF_gettable_ctx_params(const EVP_KDF *kdf);
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const OSSL_PARAM *EVP_KDF_settable_ctx_params(const EVP_KDF *kdf);
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const OSSL_PROVIDER *EVP_KDF_provider(const EVP_KDF *kdf);
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=head1 DESCRIPTION
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The EVP KDF routines are a high level interface to Key Derivation Function
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algorithms and should be used instead of algorithm-specific functions.
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After creating a B<EVP_KDF_CTX> for the required algorithm using
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EVP_KDF_CTX_new(), inputs to the algorithm are supplied
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using calls to EVP_KDF_CTX_set_params() before
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calling EVP_KDF_derive() to derive the key.
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=head2 Types
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B<EVP_KDF> is a type that holds the implementation of a KDF.
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B<EVP_KDF_CTX> is a context type that holds the algorithm inputs.
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=head2 Algorithm implementation fetching
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EVP_KDF_fetch() fetches an implementation of a KDF I<algorithm>, given
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a library context I<libctx> and a set of I<properties>.
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See L<provider(7)/Fetching algorithms> for further information.
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See L<OSSL_PROVIDER-default(7)/Key Derivation Function (KDF)> for the lists of
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algorithms supported by the default provider.
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The returned value must eventually be freed with
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L<EVP_KDF_free(3)>.
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EVP_KDF_up_ref() increments the reference count of an already fetched
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KDF.
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EVP_KDF_free() frees a fetched algorithm.
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NULL is a valid parameter, for which this function is a no-op.
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=head2 Context manipulation functions
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EVP_KDF_CTX_new() creates a new context for the KDF implementation I<kdf>.
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EVP_KDF_CTX_free() frees up the context I<ctx>. If I<ctx> is NULL, nothing
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is done.
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EVP_KDF_CTX_kdf() returns the B<EVP_KDF> associated with the context
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I<ctx>.
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=head2 Computing functions
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EVP_KDF_reset() resets the context to the default state as if the context
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had just been created.
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EVP_KDF_derive() derives I<keylen> bytes of key material and places it in the
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I<key> buffer. If the algorithm produces a fixed amount of output then an
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error will occur unless the I<keylen> parameter is equal to that output size,
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as returned by EVP_KDF_size().
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EVP_KDF_get_params() retrieves details about the implementation
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I<kdf>.
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The set of parameters given with I<params> determine exactly what
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parameters should be retrieved.
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Note that a parameter that is unknown in the underlying context is
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simply ignored.
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EVP_KDF_CTX_get_params() retrieves chosen parameters, given the
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context I<ctx> and its underlying context.
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The set of parameters given with I<params> determine exactly what
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parameters should be retrieved.
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Note that a parameter that is unknown in the underlying context is
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simply ignored.
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EVP_KDF_CTX_set_params() passes chosen parameters to the underlying
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context, given a context I<ctx>.
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The set of parameters given with I<params> determine exactly what
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parameters are passed down.
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Note that a parameter that is unknown in the underlying context is
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simply ignored.
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Also, what happens when a needed parameter isn't passed down is
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defined by the implementation.
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EVP_KDF_gettable_params(), EVP_KDF_gettable_ctx_params() and
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EVP_KDF_settable_ctx_params() get a constant B<OSSL_PARAM> array that
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describes the retrievable and settable parameters, i.e. parameters that
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can be used with EVP_KDF_get_params(), EVP_KDF_CTX_get_params()
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and EVP_KDF_CTX_set_params(), respectively.
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See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as parameter descriptor.
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=head2 Information functions
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EVP_KDF_size() returns the output size if the algorithm produces a fixed amount
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of output and B<SIZE_MAX> otherwise. If an error occurs then 0 is returned.
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For some algorithms an error may result if input parameters necessary to
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calculate a fixed output size have not yet been supplied.
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EVP_KDF_is_a() returns 1 if I<kdf> is an implementation of an
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algorithm that's identifiable with I<name>, otherwise 0.
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EVP_KDF_provider() returns the provider that holds the implementation
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of the given I<kdf>.
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EVP_KDF_do_all_provided() traverses all KDF implemented by all activated
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providers in the given library context I<libctx>, and for each of the
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implementations, calls the given function I<fn> with the implementation method
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and the given I<arg> as argument.
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EVP_KDF_number() returns the internal dynamic number assigned to
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I<kdf>.
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EVP_KDF_names_do_all() traverses all names for I<kdf>, and calls
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I<fn> with each name and I<data>.
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=head1 PARAMETERS
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The standard parameter names are:
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=over 4
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=item "pass" (B<OSSL_KDF_PARAM_PASSWORD>) <octet string>
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Some KDF implementations require a password.
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For those KDF implementations that support it, this parameter sets the password.
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=item "salt" (B<OSSL_KDF_PARAM_SALT>) <octet string>
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Some KDF implementations can take a salt.
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For those KDF implementations that support it, this parameter sets the salt.
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The default value, if any, is implementation dependent.
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=item "iter" (B<OSSL_KDF_PARAM_ITER>) <unsigned integer>
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Some KDF implementations require an iteration count.
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For those KDF implementations that support it, this parameter sets the
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iteration count.
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The default value, if any, is implementation dependent.
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=item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
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=item "mac" (B<OSSL_KDF_PARAM_MAC>) <UTF8 string>
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=item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
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=item "cipher" (B<OSSL_KDF_PARAM_CIPHER>) <UTF8 string>
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For KDF implementations that use an underlying computation MAC, digest or
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cipher, these parameters set what the algorithm should be.
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The value is always the name of the intended algorithm,
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or the properties.
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Note that not all algorithms may support all possible underlying
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implementations.
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=item "key" (B<OSSL_KDF_PARAM_KEY>) <octet string>
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Some KDF implementations require a key.
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For those KDF implementations that support it, this octet string parameter
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sets the key.
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=item "maclen" (B<OSSL_KDF_PARAM_MAC_SIZE>) <unsigned integer>
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Used by implementations that use a MAC with a variable output size (KMAC).
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For those KDF implementations that support it, this parameter
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sets the MAC output size.
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The default value, if any, is implementation dependent.
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The length must never exceed what can be given with a B<size_t>.
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=item "maxmem_bytes" (B<OSSL_KDF_PARAM_SCRYPT_MAXMEM>) <unsigned integer>
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Memory-hard password-based KDF algorithms, such as scrypt, use an amount of
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memory that depends on the load factors provided as input.
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For those KDF implementations that support it, this B<uint64_t> parameter sets
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an upper limit on the amount of memory that may be consumed while performing
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a key derivation.
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If this memory usage limit is exceeded because the load factors are chosen
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too high, the key derivation will fail.
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The default value is implementation dependent.
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The memory size must never exceed what can be given with a B<size_t>.
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=back
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=head1 RETURN VALUES
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EVP_KDF_fetch() returns a pointer to a newly fetched B<EVP_KDF>, or
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NULL if allocation failed.
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EVP_KDF_provider() returns a pointer to the provider for the KDF, or
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NULL on error.
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EVP_KDF_up_ref() returns 1 on success, 0 on error.
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EVP_KDF_CTX_new() returns either the newly allocated
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B<EVP_KDF_CTX> structure or NULL if an error occurred.
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EVP_KDF_CTX_free() and EVP_KDF_reset() do not return a value.
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EVP_KDF_size() returns the output size. B<SIZE_MAX> is returned to indicate
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that the algorithm produces a variable amount of output; 0 to indicate failure.
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The remaining functions return 1 for success and 0 or a negative value for
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failure. In particular, a return value of -2 indicates the operation is not
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supported by the KDF algorithm.
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=head1 SEE ALSO
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L<OSSL_PROVIDER-default(7)/Key Derivation Function (KDF)>
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=head1 HISTORY
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This functionality was added to 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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