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)
}
#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
@@ -20,6 +20,7 @@ OPENBSD=base64.o basename.o bcrypt_pbkdf.o bindresvport.o blowfish.o daemon.o di
port-solaris.o \
port-net.o \
port-uw.o \
+ port-linux-prng.o \
port-linux-sshd.o
.c.o:
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 +1,70 @@
+/*
+ * Copyright (c) 2011 - 2020 Red Hat, Inc.
+ *
+ * Authors:
+ * Jan F. Chadima <jchadima@redhat.com>
+ * Jakub Jelen <jjelen@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 <string.h>
+#include <openssl/rand.h>
+#include <sys/random.h>
+
+#include "log.h"
+
+void
+linux_seed(void)
+{
+ char *env = NULL;
+ size_t randlen = 14, left;
+ unsigned int flags = 0;
+ unsigned char buf[256], *p;
+
+ env = getenv("SSH_USE_STRONG_RNG");
+ if (env && strcmp(env, "0") != 0) {
+ size_t ienv = atoi(env);
+
+ /* Max on buffer length */
+ if (ienv > sizeof(buf))
+ ienv = sizeof(buf);
+ /* Minimum is always 14 B */
+ if (ienv > randlen)
+ randlen = ienv;
+ flags = GRND_RANDOM;
+ }
+
+ errno = 0;
+ left = randlen;
+ p = buf;
+ do {
+ ssize_t len = getrandom(p, left, flags);
+ if (len == -1) {
+ if (errno != EINTR)
+ fatal("Failed to seed from getrandom: %s", strerror(errno));
+ } else if (len > 0) {
+ left -= len;
+ p += len;
+ }
+ } while (left > 0);
+
+ RAND_seed(buf, randlen);
+}
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