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Diffstat (limited to 'secure/lib/libcrypto/man/man3/RAND_DRBG_set_callbacks.3')
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1 files changed, 268 insertions, 0 deletions
diff --git a/secure/lib/libcrypto/man/man3/RAND_DRBG_set_callbacks.3 b/secure/lib/libcrypto/man/man3/RAND_DRBG_set_callbacks.3 new file mode 100644 index 000000000000..49a765968ceb --- /dev/null +++ b/secure/lib/libcrypto/man/man3/RAND_DRBG_set_callbacks.3 @@ -0,0 +1,268 @@ +.\" Automatically generated by Pod::Man 4.11 (Pod::Simple 3.39) +.\" +.\" Standard preamble: +.\" ======================================================================== +.de Sp \" Vertical space (when we can't use .PP) +.if t .sp .5v +.if n .sp +.. +.de Vb \" Begin verbatim text +.ft CW +.nf +.ne \\$1 +.. +.de Ve \" End verbatim text +.ft R +.fi +.. +.\" Set up some character translations and predefined strings. \*(-- will +.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left +.\" double quote, and \*(R" will give a right double quote. \*(C+ will +.\" give a nicer C++. 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Always turn off hyphenation; it makes +.\" way too many mistakes in technical documents. +.if n .ad l +.nh +.SH "NAME" +RAND_DRBG_set_callbacks, RAND_DRBG_get_entropy_fn, RAND_DRBG_cleanup_entropy_fn, RAND_DRBG_get_nonce_fn, RAND_DRBG_cleanup_nonce_fn \&\- set callbacks for reseeding +.SH "SYNOPSIS" +.IX Header "SYNOPSIS" +.Vb 1 +\& #include <openssl/rand_drbg.h> +\& +\& +\& int RAND_DRBG_set_callbacks(RAND_DRBG *drbg, +\& RAND_DRBG_get_entropy_fn get_entropy, +\& RAND_DRBG_cleanup_entropy_fn cleanup_entropy, +\& RAND_DRBG_get_nonce_fn get_nonce, +\& RAND_DRBG_cleanup_nonce_fn cleanup_nonce); +.Ve +.SS "Callback Functions" +.IX Subsection "Callback Functions" +.Vb 6 +\& typedef size_t (*RAND_DRBG_get_entropy_fn)( +\& RAND_DRBG *drbg, +\& unsigned char **pout, +\& int entropy, +\& size_t min_len, size_t max_len, +\& int prediction_resistance); +\& +\& typedef void (*RAND_DRBG_cleanup_entropy_fn)( +\& RAND_DRBG *drbg, +\& unsigned char *out, size_t outlen); +\& +\& typedef size_t (*RAND_DRBG_get_nonce_fn)( +\& RAND_DRBG *drbg, +\& unsigned char **pout, +\& int entropy, +\& size_t min_len, size_t max_len); +\& +\& typedef void (*RAND_DRBG_cleanup_nonce_fn)( +\& RAND_DRBG *drbg, +\& unsigned char *out, size_t outlen); +.Ve +.SH "DESCRIPTION" +.IX Header "DESCRIPTION" +\&\fBRAND_DRBG_set_callbacks()\fR sets the callbacks for obtaining fresh entropy and +the nonce when reseeding the given \fBdrbg\fR. +The callback functions are implemented and provided by the caller. +Their parameter lists need to match the function prototypes above. +.PP +Setting the callbacks is allowed only if the \s-1DRBG\s0 has not been initialized yet. +Otherwise, the operation will fail. +To change the settings for one of the three shared DRBGs it is necessary to call +\&\fBRAND_DRBG_uninstantiate()\fR first. +.PP +The \fBget_entropy\fR() callback is called by the \fBdrbg\fR when it requests fresh +random input. +It is expected that the callback allocates and fills a random buffer of size +\&\fBmin_len\fR <= size <= \fBmax_len\fR (in bytes) which contains at least \fBentropy\fR +bits of randomness. +The \fBprediction_resistance\fR flag indicates whether the reseeding was +triggered by a prediction resistance request. +.PP +The buffer's address is to be returned in *\fBpout\fR and the number of collected +randomness bytes as return value. +.PP +If the callback fails to acquire at least \fBentropy\fR bits of randomness, +it must indicate an error by returning a buffer length of 0. +.PP +If \fBprediction_resistance\fR was requested and the random source of the \s-1DRBG\s0 +does not satisfy the conditions requested by [\s-1NIST SP 800\-90C\s0], then +it must also indicate an error by returning a buffer length of 0. +See \s-1NOTES\s0 section for more details. +.PP +The \fBcleanup_entropy\fR() callback is called from the \fBdrbg\fR to to clear and +free the buffer allocated previously by \fBget_entropy()\fR. +The values \fBout\fR and \fBoutlen\fR are the random buffer's address and length, +as returned by the \fBget_entropy()\fR callback. +.PP +The \fBget_nonce\fR() and \fBcleanup_nonce\fR() callbacks are used to obtain a nonce +and free it again. A nonce is only required for instantiation (not for reseeding) +and only in the case where the \s-1DRBG\s0 uses a derivation function. +The callbacks are analogous to \fBget_entropy()\fR and \fBcleanup_entropy()\fR, +except for the missing prediction_resistance flag. +.PP +If the derivation function is disabled, then no nonce is used for instantiation, +and the \fBget_nonce\fR() and \fBcleanup_nonce\fR() callbacks can be omitted by +setting them to \s-1NULL.\s0 +.SH "RETURN VALUES" +.IX Header "RETURN VALUES" +\&\fBRAND_DRBG_set_callbacks()\fR return 1 on success, and 0 on failure +.SH "NOTES" +.IX Header "NOTES" +It is important that \fBcleanup_entropy\fR() and \fBcleanup_nonce\fR() clear the buffer +contents safely before freeing it, in order not to leave sensitive information +about the \s-1DRBG\s0's state in memory. +.PP +A request for prediction resistance can only be satisfied by pulling fresh +entropy from one of the approved entropy sources listed in section 5.5.2 of +[\s-1NIST SP 800\-90C\s0]. +Since the default implementation of the get_entropy callback does not have access +to such an approved entropy source, a request for prediction resistance will +always fail. +In other words, prediction resistance is currently not supported yet by the \s-1DRBG.\s0 +.PP +The derivation function is disabled during initialization by calling the +\&\fBRAND_DRBG_set()\fR function with the \s-1RAND_DRBG_FLAG_CTR_NO_DF\s0 flag. +For more information on the derivation function and when it can be omitted, +see [\s-1NIST SP 800\-90A\s0 Rev. 1]. Roughly speaking it can be omitted if the random +source has \*(L"full entropy\*(R", i.e., contains 8 bits of entropy per byte. +.PP +Even if a nonce is required, the \fBget_nonce\fR() and \fBcleanup_nonce\fR() +callbacks can be omitted by setting them to \s-1NULL.\s0 +In this case the \s-1DRBG\s0 will automatically request an extra amount of entropy +(using the \fBget_entropy\fR() and \fBcleanup_entropy\fR() callbacks) which it will +utilize for the nonce, following the recommendations of [\s-1NIST SP 800\-90A\s0 Rev. 1], +section 8.6.7. +.SH "SEE ALSO" +.IX Header "SEE ALSO" +\&\fBRAND_DRBG_new\fR\|(3), +\&\fBRAND_DRBG_reseed\fR\|(3), +\&\s-1\fBRAND_DRBG\s0\fR\|(7) +.SH "HISTORY" +.IX Header "HISTORY" +The \s-1RAND_DRBG\s0 functions were added in OpenSSL 1.1.1. +.SH "COPYRIGHT" +.IX Header "COPYRIGHT" +Copyright 2017\-2019 The OpenSSL Project Authors. All Rights Reserved. +.PP +Licensed under the OpenSSL license (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>. |