Update build for OpenSSL-0.9.8j upgrade.
[dragonfly.git] / secure / lib / libcrypto / man / RAND_egd.3
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132.\" ========================================================================
133.\"
134.IX Title "RAND_egd 3"
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135.TH RAND_egd 3 "2009-01-11" "0.9.8j" "OpenSSL"
136.\" For nroff, turn off justification. Always turn off hyphenation; it makes
137.\" way too many mistakes in technical documents.
138.if n .ad l
139.nh
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140.SH "NAME"
141RAND_egd \- query entropy gathering daemon
142.SH "SYNOPSIS"
8b0cefbb 143.IX Header "SYNOPSIS"
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144.Vb 1
145\& #include <openssl/rand.h>
e257b235 146\&
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147\& int RAND_egd(const char *path);
148\& int RAND_egd_bytes(const char *path, int bytes);
e257b235 149\&
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150\& int RAND_query_egd_bytes(const char *path, unsigned char *buf, int bytes);
151.Ve
152.SH "DESCRIPTION"
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153.IX Header "DESCRIPTION"
154\&\fIRAND_egd()\fR queries the entropy gathering daemon \s-1EGD\s0 on socket \fBpath\fR.
155It queries 255 bytes and uses \fIRAND_add\fR\|(3) to seed the
156OpenSSL built-in \s-1PRNG\s0. RAND_egd(path) is a wrapper for
157RAND_egd_bytes(path, 255);
984263bc 158.PP
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159\&\fIRAND_egd_bytes()\fR queries the entropy gathering daemon \s-1EGD\s0 on socket \fBpath\fR.
160It queries \fBbytes\fR bytes and uses \fIRAND_add\fR\|(3) to seed the
161OpenSSL built-in \s-1PRNG\s0.
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162This function is more flexible than \fIRAND_egd()\fR.
163When only one secret key must
164be generated, it is not necessary to request the full amount 255 bytes from
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165the \s-1EGD\s0 socket. This can be advantageous, since the amount of entropy
166that can be retrieved from \s-1EGD\s0 over time is limited.
984263bc 167.PP
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168\&\fIRAND_query_egd_bytes()\fR performs the actual query of the \s-1EGD\s0 daemon on socket
169\&\fBpath\fR. If \fBbuf\fR is given, \fBbytes\fR bytes are queried and written into
170\&\fBbuf\fR. If \fBbuf\fR is \s-1NULL\s0, \fBbytes\fR bytes are queried and used to seed the
171OpenSSL built-in \s-1PRNG\s0 using \fIRAND_add\fR\|(3).
984263bc 172.SH "NOTES"
8b0cefbb 173.IX Header "NOTES"
984263bc 174On systems without /dev/*random devices providing entropy from the kernel,
8b0cefbb 175the \s-1EGD\s0 entropy gathering daemon can be used to collect entropy. It provides
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176a socket interface through which entropy can be gathered in chunks up to
177255 bytes. Several chunks can be queried during one connection.
178.PP
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179\&\s-1EGD\s0 is available from http://www.lothar.com/tech/crypto/ (\f(CW\*(C`perl
180Makefile.PL; make; make install\*(C'\fR to install). It is run as \fBegd\fR
181\&\fIpath\fR, where \fIpath\fR is an absolute path designating a socket. When
182\&\fIRAND_egd()\fR is called with that path as an argument, it tries to read
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183random bytes that \s-1EGD\s0 has collected. \fIRAND_egd()\fR retrieves entropy from the
184daemon using the daemon's \*(L"non-blocking read\*(R" command which shall
185be answered immediately by the daemon without waiting for additional
186entropy to be collected. The write and read socket operations in the
187communication are blocking.
984263bc 188.PP
8b0cefbb 189Alternatively, the EGD-interface compatible daemon \s-1PRNGD\s0 can be used. It is
984263bc 190available from
edae4a78 191http://prngd.sourceforge.net/ .
8b0cefbb 192\&\s-1PRNGD\s0 does employ an internal \s-1PRNG\s0 itself and can therefore never run
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193out of entropy.
194.PP
8b0cefbb 195OpenSSL automatically queries \s-1EGD\s0 when entropy is requested via \fIRAND_bytes()\fR
984263bc 196or the status is checked via \fIRAND_status()\fR for the first time, if the socket
8b0cefbb 197is located at /var/run/egd\-pool, /dev/egd\-pool or /etc/egd\-pool.
984263bc 198.SH "RETURN VALUE"
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199.IX Header "RETURN VALUE"
200\&\fIRAND_egd()\fR and \fIRAND_egd_bytes()\fR return the number of bytes read from the
984263bc 201daemon on success, and \-1 if the connection failed or the daemon did not
8b0cefbb 202return enough data to fully seed the \s-1PRNG\s0.
984263bc 203.PP
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204\&\fIRAND_query_egd_bytes()\fR returns the number of bytes read from the daemon on
205success, and \-1 if the connection failed. The \s-1PRNG\s0 state is not considered.
984263bc 206.SH "SEE ALSO"
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207.IX Header "SEE ALSO"
208\&\fIrand\fR\|(3), \fIRAND_add\fR\|(3),
209\&\fIRAND_cleanup\fR\|(3)
984263bc 210.SH "HISTORY"
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211.IX Header "HISTORY"
212\&\fIRAND_egd()\fR is available since OpenSSL 0.9.5.
984263bc 213.PP
8b0cefbb 214\&\fIRAND_egd_bytes()\fR is available since OpenSSL 0.9.6.
984263bc 215.PP
8b0cefbb 216\&\fIRAND_query_egd_bytes()\fR is available since OpenSSL 0.9.7.
984263bc 217.PP
8b0cefbb 218The automatic query of /var/run/egd\-pool et al was added in OpenSSL 0.9.7.