diff --git a/entropy.c b/entropy.c
index 2d483b3..b361a04 100644
--- a/entropy.c
+++ b/entropy.c
@@ -234,6 +234,9 @@ seed_rng(void)
memset(buf, '\0', sizeof(buf));
#endif /* OPENSSL_PRNG_ONLY */
+#ifdef __linux__
+ linux_seed();
+#endif /* __linux__ */
if (RAND_status() != 1)
fatal("PRNG is not seeded");
}
diff --git a/openbsd-compat/Makefile.in b/openbsd-compat/Makefile.in
index b912dbe..9206337 100644
--- a/openbsd-compat/Makefile.in
+++ b/openbsd-compat/Makefile.in
@@ -20,7 +20,7 @@ OPENBSD=base64.o basename.o bcrypt_pbkdf.o bindresvport.o blowfish.o daemon.o di
COMPAT=arc4random.o bsd-asprintf.o bsd-closefrom.o bsd-cray.o bsd-cygwin_util.o bsd-getpeereid.o getrrsetbyname-ldns.o bsd-err.o bsd-misc.o bsd-nextstep.o bsd-openpty.o bsd-poll.o bsd-setres_id.o bsd-snprintf.o bsd-statvfs.o bsd-waitpid.o fake-rfc2553.o openssl-compat.o xcrypt.o kludge-fd_set.o
-PORTS=port-aix.o port-irix.o port-linux.o port-linux-sshd.o port-solaris.o port-tun.o port-uw.o
+PORTS=port-aix.o port-irix.o port-linux.o port-linux-sshd.o port-linux-prng.o port-solaris.o port-tun.o port-uw.o
.c.o:
$(CC) $(CFLAGS) $(CPPFLAGS) -c $<
diff -up openssh-7.4p1/openbsd-compat/port-linux.h.entropy openssh-7.4p1/openbsd-compat/port-linux.h
--- openssh-7.4p1/openbsd-compat/port-linux.h.entropy 2016-12-23 18:34:27.747753563 +0100
+++ openssh-7.4p1/openbsd-compat/port-linux.h 2016-12-23 18:34:27.769753570 +0100
@@ -34,4 +34,6 @@ void oom_adjust_restore(void);
void oom_adjust_setup(void);
#endif
+void linux_seed(void);
+
#endif /* ! _PORT_LINUX_H */
diff --git a/openbsd-compat/port-linux-prng.c b/openbsd-compat/port-linux-prng.c
new file mode 100644
index 0000000..92a617c
--- /dev/null
+++ b/openbsd-compat/port-linux-prng.c
@@ -0,0 +1,59 @@
+/* $Id: port-linux.c,v 1.11.4.2 2011/02/04 00:43:08 djm Exp $ */
+
+/*
+ * Copyright (c) 2011 Jan F. Chadima <jchadima@redhat.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * Linux-specific portability code - prng support
+ */
+
+#include "includes.h"
+
+#include <errno.h>
+#include <stdarg.h>
+#include <string.h>
+#include <stdio.h>
+#include <openssl/rand.h>
+
+#include "log.h"
+#include "xmalloc.h"
+#include "misc.h" /* servconf.h needs misc.h for struct ForwardOptions */
+#include "servconf.h"
+#include "port-linux.h"
+#include "key.h"
+#include "hostfile.h"
+#include "auth.h"
+
+void
+linux_seed(void)
+{
+ char *env = getenv("SSH_USE_STRONG_RNG");
+ char *random = "/dev/random";
+ size_t len, ienv, randlen = 14;
+
+ if (!env || !strcmp(env, "0"))
+ random = "/dev/urandom";
+ else if ((ienv = atoi(env)) > randlen)
+ randlen = ienv;
+
+ errno = 0;
+ if ((len = RAND_load_file(random, randlen)) != randlen) {
+ if (errno)
+ fatal ("cannot read from %s, %s", random, strerror(errno));
+ else
+ fatal ("EOF reading %s", random);
+ }
+}
diff --git a/ssh-add.0 b/ssh-add.0
index ba43fee..0b2629a 100644
--- a/ssh-add.0
+++ b/ssh-add.0
@@ -82,6 +82,16 @@ ENVIRONMENT
Identifies the path of a UNIX-domain socket used to communicate
with the agent.
+ SSH_USE_STRONG_RNG
+ The reseeding of the OpenSSL random generator is usually done
+ from /dev/urandom. If the SSH_USE_STRONG_RNG environment vari-
+ able is set to value other than 0 the OpenSSL random generator is
+ reseeded from /dev/random. The number of bytes read is defined
+ by the SSH_USE_STRONG_RNG value. Minimum is 14 bytes. This set-
+ ting is not recommended on the computers without the hardware
+ random generator because insufficient entropy causes the connec-
+ tion to be blocked until enough entropy is available.
+
FILES
~/.ssh/identity
Contains the protocol version 1 RSA authentication identity of
diff --git a/ssh-add.1 b/ssh-add.1
index 4812448..16305bf 100644
--- a/ssh-add.1
+++ b/ssh-add.1
@@ -161,6 +161,20 @@ to make this work.)
Identifies the path of a
.Ux Ns -domain
socket used to communicate with the agent.
+.It Ev SSH_USE_STRONG_RNG
+The reseeding of the OpenSSL random generator is usually done from
+.Cm /dev/urandom .
+If the
+.Cm SSH_USE_STRONG_RNG
+environment variable is set to value other than
+.Cm 0
+the OpenSSL random generator is reseeded from
+.Cm /dev/random .
+The number of bytes read is defined by the SSH_USE_STRONG_RNG value.
+Minimum is 14 bytes.
+This setting is not recommended on the computers without the hardware
+random generator because insufficient entropy causes the connection to
+be blocked until enough entropy is available.
.El
.Sh FILES
.Bl -tag -width Ds
diff --git a/ssh-agent.1 b/ssh-agent.1
index 281ecbd..1a9a635 100644
--- a/ssh-agent.1
+++ b/ssh-agent.1
@@ -201,6 +201,24 @@ sockets used to contain the connection to the authentication agent.
These sockets should only be readable by the owner.
The sockets should get automatically removed when the agent exits.
.El
+.Sh ENVIRONMENT
+.Bl -tag -width Ds -compact
+.Pp
+.It Pa SSH_USE_STRONG_RNG
+The reseeding of the OpenSSL random generator is usually done from
+.Cm /dev/urandom .
+If the
+.Cm SSH_USE_STRONG_RNG
+environment variable is set to value other than
+.Cm 0
+the OpenSSL random generator is reseeded from
+.Cm /dev/random .
+The number of bytes read is defined by the SSH_USE_STRONG_RNG value.
+Minimum is 14 bytes.
+This setting is not recommended on the computers without the hardware
+random generator because insufficient entropy causes the connection to
+be blocked until enough entropy is available.
+.El
.Sh SEE ALSO
.Xr ssh 1 ,
.Xr ssh-add 1 ,
diff --git a/ssh-keygen.1 b/ssh-keygen.1
index 12e00d4..1b51a4a 100644
--- a/ssh-keygen.1
+++ b/ssh-keygen.1
@@ -832,6 +832,24 @@ Contains Diffie-Hellman groups used for DH-GEX.
The file format is described in
.Xr moduli 5 .
.El
+.Sh ENVIRONMENT
+.Bl -tag -width Ds -compact
+.Pp
+.It Pa SSH_USE_STRONG_RNG
+The reseeding of the OpenSSL random generator is usually done from
+.Cm /dev/urandom .
+If the
+.Cm SSH_USE_STRONG_RNG
+environment variable is set to value other than
+.Cm 0
+the OpenSSL random generator is reseeded from
+.Cm /dev/random .
+The number of bytes read is defined by the SSH_USE_STRONG_RNG value.
+Minimum is 14 bytes.
+This setting is not recommended on the computers without the hardware
+random generator because insufficient entropy causes the connection to
+be blocked until enough entropy is available.
+.El
.Sh SEE ALSO
.Xr ssh 1 ,
.Xr ssh-add 1 ,
diff --git a/ssh-keysign.8 b/ssh-keysign.8
index 69d0829..02d79f8 100644
--- a/ssh-keysign.8
+++ b/ssh-keysign.8
@@ -80,6 +80,24 @@ must be set-uid root if host-based authentication is used.
If these files exist they are assumed to contain public certificate
information corresponding with the private keys above.
.El
+.Sh ENVIRONMENT
+.Bl -tag -width Ds -compact
+.Pp
+.It Pa SSH_USE_STRONG_RNG
+The reseeding of the OpenSSL random generator is usually done from
+.Cm /dev/urandom .
+If the
+.Cm SSH_USE_STRONG_RNG
+environment variable is set to value other than
+.Cm 0
+the OpenSSL random generator is reseeded from
+.Cm /dev/random .
+The number of bytes read is defined by the SSH_USE_STRONG_RNG value.
+Minimum is 14 bytes.
+This setting is not recommended on the computers without the hardware
+random generator because insufficient entropy causes the connection to
+be blocked until enough entropy is available.
+.El
.Sh SEE ALSO
.Xr ssh 1 ,
.Xr ssh-keygen 1 ,
diff --git a/ssh.1 b/ssh.1
index 929904b..f65e42f 100644
--- a/ssh.1
+++ b/ssh.1
@@ -1309,6 +1309,23 @@ For more information, see the
.Cm PermitUserEnvironment
option in
.Xr sshd_config 5 .
+.Sh ENVIRONMENT
+.Bl -tag -width Ds -compact
+.It Ev SSH_USE_STRONG_RNG
+The reseeding of the OpenSSL random generator is usually done from
+.Cm /dev/urandom .
+If the
+.Cm SSH_USE_STRONG_RNG
+environment variable is set to value other than
+.Cm 0
+the OpenSSL random generator is reseeded from
+.Cm /dev/random .
+The number of bytes read is defined by the SSH_USE_STRONG_RNG value.
+Minimum is 14 bytes.
+This setting is not recommended on the computers without the hardware
+random generator because insufficient entropy causes the connection to
+be blocked until enough entropy is available.
+.El
.Sh FILES
.Bl -tag -width Ds -compact
.It Pa ~/.rhosts
diff --git a/sshd.8 b/sshd.8
index c2c237f..058d37a 100644
--- a/sshd.8
+++ b/sshd.8
@@ -951,6 +951,24 @@ concurrently for different ports, this contains the process ID of the one
started last).
The content of this file is not sensitive; it can be world-readable.
.El
+.Sh ENVIRONMENT
+.Bl -tag -width Ds -compact
+.Pp
+.It Pa SSH_USE_STRONG_RNG
+The reseeding of the OpenSSL random generator is usually done from
+.Cm /dev/urandom .
+If the
+.Cm SSH_USE_STRONG_RNG
+environment variable is set to value other than
+.Cm 0
+the OpenSSL random generator is reseeded from
+.Cm /dev/random .
+The number of bytes read is defined by the SSH_USE_STRONG_RNG value.
+Minimum is 14 bytes.
+This setting is not recommended on the computers without the hardware
+random generator because insufficient entropy causes the connection to
+be blocked until enough entropy is available.
+.El
.Sh IPV6
IPv6 address can be used everywhere where IPv4 address. In all entries must be the IPv6 address enclosed in square brackets. Note: The square brackets are metacharacters for the shell and must be escaped in shell.
.Sh SEE ALSO