openssl-prebuild/linux_amd64/ssl/share/man/man3/EVP_KDF.3
2020-03-02 16:50:34 +00:00

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.\" ========================================================================
.\"
.IX Title "EVP_KDF 3"
.TH EVP_KDF 3 "2020-03-02" "3.0.0-dev" "OpenSSL"
.\" For nroff, turn off justification. Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
EVP_KDF, EVP_KDF_fetch, EVP_KDF_free, EVP_KDF_up_ref,
EVP_KDF_CTX, EVP_KDF_CTX_new, EVP_KDF_CTX_free, EVP_KDF_CTX_dup,
EVP_KDF_reset, EVP_KDF_derive,
EVP_KDF_size, EVP_KDF_provider, EVP_KDF_CTX_kdf, EVP_KDF_is_a,
EVP_KDF_number, EVP_KDF_names_do_all,
EVP_KDF_CTX_get_params, EVP_KDF_CTX_set_params, EVP_KDF_do_all_provided,
EVP_KDF_get_params, EVP_KDF_gettable_ctx_params, EVP_KDF_settable_ctx_params,
EVP_KDF_gettable_params \- EVP KDF routines
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/kdf.h>
\&
\& typedef struct evp_kdf_st EVP_KDF;
\& typedef struct evp_kdf_ctx_st EVP_KDF_CTX;
\&
\& EVP_KDF_CTX *EVP_KDF_CTX_new(const EVP_KDF *kdf);
\& const EVP_KDF *EVP_KDF_CTX_kdf(EVP_KDF_CTX *ctx);
\& void EVP_KDF_CTX_free(EVP_KDF_CTX *ctx);
\& EVP_KDF_CTX *EVP_KDF_CTX_dup(const EVP_KDF_CTX *src);
\& void EVP_KDF_reset(EVP_KDF_CTX *ctx);
\& size_t EVP_KDF_size(EVP_KDF_CTX *ctx);
\& int EVP_KDF_derive(EVP_KDF_CTX *ctx, unsigned char *key, size_t keylen);
\& int EVP_KDF_up_ref(EVP_KDF *kdf);
\& void EVP_KDF_free(EVP_KDF *kdf);
\& EVP_KDF *EVP_KDF_fetch(OPENSSL_CTX *libctx, const char *algorithm,
\& const char *properties);
\& int EVP_KDF_number(const EVP_KDF *kdf);
\& int EVP_KDF_is_a(const EVP_KDF *kdf, const char *name);
\& const OSSL_PROVIDER *EVP_KDF_provider(const EVP_KDF *kdf);
\& void EVP_KDF_do_all_provided(OPENSSL_CTX *libctx,
\& void (*fn)(EVP_KDF *kdf, void *arg),
\& void *arg);
\& void EVP_KDF_names_do_all(const EVP_KDF *kdf,
\& void (*fn)(const char *name, void *data),
\& void *data);
\& int EVP_KDF_get_params(EVP_KDF *kdf, OSSL_PARAM params[]);
\& int EVP_KDF_CTX_get_params(EVP_KDF_CTX *ctx, OSSL_PARAM params[]);
\& int EVP_KDF_CTX_set_params(EVP_KDF_CTX *ctx, const OSSL_PARAM params[]);
\& const OSSL_PARAM *EVP_KDF_gettable_params(const EVP_KDF *kdf);
\& const OSSL_PARAM *EVP_KDF_gettable_ctx_params(const EVP_KDF *kdf);
\& const OSSL_PARAM *EVP_KDF_settable_ctx_params(const EVP_KDF *kdf);
\& const OSSL_PROVIDER *EVP_KDF_provider(const EVP_KDF *kdf);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \s-1EVP\s0 \s-1KDF\s0 routines are a high level interface to Key Derivation Function
algorithms and should be used instead of algorithm-specific functions.
.PP
After creating a \fB\s-1EVP_KDF_CTX\s0\fR for the required algorithm using
\&\fIEVP_KDF_CTX_new()\fR, inputs to the algorithm are supplied
using calls to \fIEVP_KDF_CTX_set_params()\fR before
calling \fIEVP_KDF_derive()\fR to derive the key.
.SS "Types"
.IX Subsection "Types"
\&\fB\s-1EVP_KDF\s0\fR is a type that holds the implementation of a \s-1KDF\s0.
.PP
\&\fB\s-1EVP_KDF_CTX\s0\fR is a context type that holds the algorithm inputs.
.SS "Algorithm implementation fetching"
.IX Subsection "Algorithm implementation fetching"
\&\fIEVP_KDF_fetch()\fR fetches an implementation of a \s-1KDF\s0 \fIalgorithm\fR, given
a library context \fIlibctx\fR and a set of \fIproperties\fR.
See \*(L"Fetching algorithms\*(R" in \fIprovider\fR\|(7) for further information.
.PP
The returned value must eventually be freed with
\&\fIEVP_KDF_free\fR\|(3).
.PP
\&\fIEVP_KDF_up_ref()\fR increments the reference count of an already fetched
\&\s-1KDF\s0.
.PP
\&\fIEVP_KDF_free()\fR frees a fetched algorithm.
\&\s-1NULL\s0 is a valid parameter, for which this function is a no-op.
.SS "Context manipulation functions"
.IX Subsection "Context manipulation functions"
\&\fIEVP_KDF_CTX_new()\fR creates a new context for the \s-1KDF\s0 implementation \fIkdf\fR.
.PP
\&\fIEVP_KDF_CTX_free()\fR frees up the context \fIctx\fR. If \fIctx\fR is \s-1NULL\s0, nothing
is done.
.PP
\&\fIEVP_KDF_CTX_kdf()\fR returns the \fB\s-1EVP_KDF\s0\fR associated with the context
\&\fIctx\fR.
.SS "Computing functions"
.IX Subsection "Computing functions"
\&\fIEVP_KDF_reset()\fR resets the context to the default state as if the context
had just been created.
.PP
\&\fIEVP_KDF_derive()\fR derives \fIkeylen\fR bytes of key material and places it in the
\&\fIkey\fR buffer. If the algorithm produces a fixed amount of output then an
error will occur unless the \fIkeylen\fR parameter is equal to that output size,
as returned by \fIEVP_KDF_size()\fR.
.PP
\&\fIEVP_KDF_get_params()\fR retrieves details about the implementation
\&\fIkdf\fR.
The set of parameters given with \fIparams\fR determine exactly what
parameters should be retrieved.
Note that a parameter that is unknown in the underlying context is
simply ignored.
.PP
\&\fIEVP_KDF_CTX_get_params()\fR retrieves chosen parameters, given the
context \fIctx\fR and its underlying context.
The set of parameters given with \fIparams\fR determine exactly what
parameters should be retrieved.
Note that a parameter that is unknown in the underlying context is
simply ignored.
.PP
\&\fIEVP_KDF_CTX_set_params()\fR passes chosen parameters to the underlying
context, given a context \fIctx\fR.
The set of parameters given with \fIparams\fR determine exactly what
parameters are passed down.
Note that a parameter that is unknown in the underlying context is
simply ignored.
Also, what happens when a needed parameter isn't passed down is
defined by the implementation.
.PP
\&\fIEVP_KDF_gettable_params()\fR, \fIEVP_KDF_gettable_ctx_params()\fR and
\&\fIEVP_KDF_settable_ctx_params()\fR get a constant \fB\s-1OSSL_PARAM\s0\fR array that
describes the retrievable and settable parameters, i.e. parameters that
can be used with \fIEVP_KDF_get_params()\fR, \fIEVP_KDF_CTX_get_params()\fR
and \fIEVP_KDF_CTX_set_params()\fR, respectively.
See \s-1\fIOSSL_PARAM\s0\fR\|(3) for the use of \fB\s-1OSSL_PARAM\s0\fR as parameter descriptor.
.SS "Information functions"
.IX Subsection "Information functions"
\&\fIEVP_KDF_size()\fR returns the output size if the algorithm produces a fixed amount
of output and \fB\s-1SIZE_MAX\s0\fR otherwise. If an error occurs then 0 is returned.
For some algorithms an error may result if input parameters necessary to
calculate a fixed output size have not yet been supplied.
.PP
\&\fIEVP_KDF_is_a()\fR returns 1 if \fIkdf\fR is an implementation of an
algorithm that's identifiable with \fIname\fR, otherwise 0.
.PP
\&\fIEVP_KDF_provider()\fR returns the provider that holds the implementation
of the given \fIkdf\fR.
.PP
\&\fIEVP_KDF_do_all_provided()\fR traverses all \s-1KDF\s0 implemented by all activated
providers in the given library context \fIlibctx\fR, and for each of the
implementations, calls the given function \fIfn\fR with the implementation method
and the given \fIarg\fR as argument.
.PP
\&\fIEVP_KDF_number()\fR returns the internal dynamic number assigned to
\&\fIkdf\fR.
.PP
\&\fIEVP_KDF_names_do_all()\fR traverses all names for \fIkdf\fR, and calls
\&\fIfn\fR with each name and \fIdata\fR.
.SH "PARAMETERS"
.IX Header "PARAMETERS"
The standard parameter names are:
.ie n .IP """pass"" (\fB\s-1OSSL_KDF_PARAM_PASSWORD\s0\fR) <octet string>" 4
.el .IP "``pass'' (\fB\s-1OSSL_KDF_PARAM_PASSWORD\s0\fR) <octet string>" 4
.IX Item "pass (OSSL_KDF_PARAM_PASSWORD) <octet string>"
Some \s-1KDF\s0 implementations require a password.
For those \s-1KDF\s0 implementations that support it, this parameter sets the password.
.ie n .IP """salt"" (\fB\s-1OSSL_KDF_PARAM_SALT\s0\fR) <octet string>" 4
.el .IP "``salt'' (\fB\s-1OSSL_KDF_PARAM_SALT\s0\fR) <octet string>" 4
.IX Item "salt (OSSL_KDF_PARAM_SALT) <octet string>"
Some \s-1KDF\s0 implementations can take a salt.
For those \s-1KDF\s0 implementations that support it, this parameter sets the salt.
.Sp
The default value, if any, is implementation dependent.
.ie n .IP """iter"" (\fB\s-1OSSL_KDF_PARAM_ITER\s0\fR) <unsigned integer>" 4
.el .IP "``iter'' (\fB\s-1OSSL_KDF_PARAM_ITER\s0\fR) <unsigned integer>" 4
.IX Item "iter (OSSL_KDF_PARAM_ITER) <unsigned integer>"
Some \s-1KDF\s0 implementations require an iteration count.
For those \s-1KDF\s0 implementations that support it, this parameter sets the
iteration count.
.Sp
The default value, if any, is implementation dependent.
.ie n .IP """properties"" (\fB\s-1OSSL_KDF_PARAM_PROPERTIES\s0\fR) <\s-1UTF8\s0 string>" 4
.el .IP "``properties'' (\fB\s-1OSSL_KDF_PARAM_PROPERTIES\s0\fR) <\s-1UTF8\s0 string>" 4
.IX Item "properties (OSSL_KDF_PARAM_PROPERTIES) <UTF8 string>"
.PD 0
.ie n .IP """mac"" (\fB\s-1OSSL_KDF_PARAM_MAC\s0\fR) <\s-1UTF8\s0 string>" 4
.el .IP "``mac'' (\fB\s-1OSSL_KDF_PARAM_MAC\s0\fR) <\s-1UTF8\s0 string>" 4
.IX Item "mac (OSSL_KDF_PARAM_MAC) <UTF8 string>"
.ie n .IP """digest"" (\fB\s-1OSSL_KDF_PARAM_DIGEST\s0\fR) <\s-1UTF8\s0 string>" 4
.el .IP "``digest'' (\fB\s-1OSSL_KDF_PARAM_DIGEST\s0\fR) <\s-1UTF8\s0 string>" 4
.IX Item "digest (OSSL_KDF_PARAM_DIGEST) <UTF8 string>"
.ie n .IP """cipher"" (\fB\s-1OSSL_KDF_PARAM_CIPHER\s0\fR) <\s-1UTF8\s0 string>" 4
.el .IP "``cipher'' (\fB\s-1OSSL_KDF_PARAM_CIPHER\s0\fR) <\s-1UTF8\s0 string>" 4
.IX Item "cipher (OSSL_KDF_PARAM_CIPHER) <UTF8 string>"
.PD
For \s-1KDF\s0 implementations that use an underlying computation \s-1MAC\s0, digest or
cipher, these parameters set what the algorithm should be.
.Sp
The value is always the name of the intended algorithm,
or the properties.
.Sp
Note that not all algorithms may support all possible underlying
implementations.
.ie n .IP """key"" (\fB\s-1OSSL_KDF_PARAM_KEY\s0\fR) <octet string>" 4
.el .IP "``key'' (\fB\s-1OSSL_KDF_PARAM_KEY\s0\fR) <octet string>" 4
.IX Item "key (OSSL_KDF_PARAM_KEY) <octet string>"
Some \s-1KDF\s0 implementations require a key.
For those \s-1KDF\s0 implementations that support it, this octet string parameter
sets the key.
.ie n .IP """maclen"" (\fB\s-1OSSL_KDF_PARAM_MAC_SIZE\s0\fR) <unsigned integer>" 4
.el .IP "``maclen'' (\fB\s-1OSSL_KDF_PARAM_MAC_SIZE\s0\fR) <unsigned integer>" 4
.IX Item "maclen (OSSL_KDF_PARAM_MAC_SIZE) <unsigned integer>"
Used by implementations that use a \s-1MAC\s0 with a variable output size (\s-1KMAC\s0).
For those \s-1KDF\s0 implementations that support it, this parameter
sets the \s-1MAC\s0 output size.
.Sp
The default value, if any, is implementation dependent.
The length must never exceed what can be given with a \fBsize_t\fR.
.ie n .IP """maxmem_bytes"" (\fB\s-1OSSL_KDF_PARAM_SCRYPT_MAXMEM\s0\fR) <unsigned integer>" 4
.el .IP "``maxmem_bytes'' (\fB\s-1OSSL_KDF_PARAM_SCRYPT_MAXMEM\s0\fR) <unsigned integer>" 4
.IX Item "maxmem_bytes (OSSL_KDF_PARAM_SCRYPT_MAXMEM) <unsigned integer>"
Memory-hard password-based \s-1KDF\s0 algorithms, such as scrypt, use an amount of
memory that depends on the load factors provided as input.
For those \s-1KDF\s0 implementations that support it, this \fBuint64_t\fR parameter sets
an upper limit on the amount of memory that may be consumed while performing
a key derivation.
If this memory usage limit is exceeded because the load factors are chosen
too high, the key derivation will fail.
.Sp
The default value is implementation dependent.
The memory size must never exceed what can be given with a \fBsize_t\fR.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fIEVP_KDF_fetch()\fR returns a pointer to a newly fetched \fB\s-1EVP_KDF\s0\fR, or
\&\s-1NULL\s0 if allocation failed.
.PP
\&\fIEVP_KDF_provider()\fR returns a pointer to the provider for the \s-1KDF\s0, or
\&\s-1NULL\s0 on error.
.PP
\&\fIEVP_KDF_up_ref()\fR returns 1 on success, 0 on error.
.PP
\&\fIEVP_KDF_CTX_new()\fR returns either the newly allocated
\&\fB\s-1EVP_KDF_CTX\s0\fR structure or \s-1NULL\s0 if an error occurred.
.PP
\&\fIEVP_KDF_CTX_free()\fR and \fIEVP_KDF_reset()\fR do not return a value.
.PP
\&\fIEVP_KDF_size()\fR returns the output size. \fB\s-1SIZE_MAX\s0\fR is returned to indicate
that the algorithm produces a variable amount of output; 0 to indicate failure.
.PP
The remaining functions return 1 for success and 0 or a negative value for
failure. In particular, a return value of \-2 indicates the operation is not
supported by the \s-1KDF\s0 algorithm.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\s-1\fIEVP_KDF\-SCRYPT\s0\fR\|(7)
\&\s-1\fIEVP_KDF\-TLS1_PRF\s0\fR\|(7)
\&\s-1\fIEVP_KDF\-PBKDF2\s0\fR\|(7)
\&\s-1\fIEVP_KDF\-HKDF\s0\fR\|(7)
\&\s-1\fIEVP_KDF\-SS\s0\fR\|(7)
\&\s-1\fIEVP_KDF\-SSHKDF\s0\fR\|(7)
\&\s-1\fIEVP_KDF\-X963\s0\fR\|(7)
\&\s-1\fIEVP_KDF\-X942\s0\fR\|(7)
.SH "HISTORY"
.IX Header "HISTORY"
This functionality was added to OpenSSL 3.0.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.