974eeb93e3
Tweak to documentation following feedback Reviewed-by: Tim Hudson <tjh@openssl.org> Reviewed-by: Richard Levitte <levitte@openssl.org>
73 lines
2.3 KiB
Plaintext
73 lines
2.3 KiB
Plaintext
=pod
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=head1 NAME
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RAND_set_rand_method, RAND_get_rand_method, RAND_OpenSSL - select RAND method
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=head1 SYNOPSIS
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#include <openssl/rand.h>
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void RAND_set_rand_method(const RAND_METHOD *meth);
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const RAND_METHOD *RAND_get_rand_method(void);
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RAND_METHOD *RAND_OpenSSL(void);
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=head1 DESCRIPTION
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A B<RAND_METHOD> specifies the functions that OpenSSL uses for random number
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generation. By modifying the method, alternative implementations such as
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hardware RNGs may be used. IMPORTANT: See the NOTES section for important
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information about how these RAND API functions are affected by the use of
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B<ENGINE> API calls.
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Initially, the default RAND_METHOD is the OpenSSL internal implementation, as
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returned by RAND_OpenSSL().
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RAND_set_default_method() makes B<meth> the method for PRNG use. B<NB>: This is
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true only whilst no ENGINE has been set as a default for RAND, so this function
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is no longer recommended.
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RAND_get_default_method() returns a pointer to the current RAND_METHOD.
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However, the meaningfulness of this result is dependent on whether the ENGINE
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API is being used, so this function is no longer recommended.
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=head1 THE RAND_METHOD STRUCTURE
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typedef struct rand_meth_st
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{
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void (*seed)(const void *buf, int num);
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int (*bytes)(unsigned char *buf, int num);
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void (*cleanup)(void);
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void (*add)(const void *buf, int num, int entropy);
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int (*pseudorand)(unsigned char *buf, int num);
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int (*status)(void);
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} RAND_METHOD;
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The components point to method implementations used by (or called by), in order,
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RAND_seed(), RAND_bytes(), internal RAND cleanup, RAND_add(), RAND_pseudo_rand()
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and RAND_status().
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Each component may be NULL if the function is not implemented.
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=head1 RETURN VALUES
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RAND_set_rand_method() returns no value. RAND_get_rand_method() and
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RAND_OpenSSL() return pointers to the respective methods.
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=head1 NOTES
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RAND_METHOD implementations are grouped together with other
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algorithmic APIs (eg. RSA_METHOD, EVP_CIPHER, etc) in B<ENGINE> modules. If a
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default ENGINE is specified for RAND functionality using an ENGINE API function,
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that will override any RAND defaults set using the RAND API (ie.
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RAND_set_rand_method()). For this reason, the ENGINE API is the recommended way
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to control default implementations for use in RAND and other cryptographic
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algorithms.
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=head1 SEE ALSO
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L<rand(3)>, L<engine(3)>
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=cut
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