83 lines
2.8 KiB
Text
83 lines
2.8 KiB
Text
=pod
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=head1 NAME
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RAND_set_rand_method, RAND_get_rand_method, RAND_SSLeay - 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_SSLeay(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_SSLeay().
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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 the implementation of RAND_seed(),
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RAND_bytes(), 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_SSLeay() return pointers to the respective methods.
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=head1 NOTES
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As of version 0.9.7, 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)|rand(3)>, L<engine(3)|engine(3)>
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=head1 HISTORY
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RAND_set_rand_method(), RAND_get_rand_method() and RAND_SSLeay() are
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available in all versions of OpenSSL.
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In the engine version of version 0.9.6, RAND_set_rand_method() was altered to
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take an ENGINE pointer as its argument. As of version 0.9.7, that has been
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reverted as the ENGINE API transparently overrides RAND defaults if used,
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otherwise RAND API functions work as before. RAND_set_rand_engine() was also
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introduced in version 0.9.7.
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=cut
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