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upstream: apply a lick of paint; tweaks/ok dtucker

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OpenBSD-Commit-ID: 518a6736338045e0037f503c21027d958d05e703
This commit is contained in:
jmc@openbsd.org 2018-03-02 21:40:15 +00:00 committed by Damien Miller
parent 713d9cb510
commit f493d2b0b6
2 changed files with 48 additions and 58 deletions
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102
ssh-keyscan.1
View File

@ -1,4 +1,4 @@
.\" $OpenBSD: ssh-keyscan.1,v 1.42 2018/02/23 07:38:09 jmc Exp $
.\" $OpenBSD: ssh-keyscan.1,v 1.43 2018/03/02 21:40:15 jmc Exp $
.\"
.\" Copyright 1995, 1996 by David Mazieres <dm@lcs.mit.edu>.
.\"
@ -6,26 +6,23 @@
.\" permitted provided that due credit is given to the author and the
.\" OpenBSD project by leaving this copyright notice intact.
.\"
.Dd $Mdocdate: February 23 2018 $
.Dd $Mdocdate: March 2 2018 $
.Dt SSH-KEYSCAN 1
.Os
.Sh NAME
.Nm ssh-keyscan
.Nd gather ssh public keys
.Nd gather SSH public keys
.Sh SYNOPSIS
.Nm ssh-keyscan
.Bk -words
.Op Fl 46cDHv
.Op Fl f Ar file
.Op Fl p Ar port
.Op Fl T Ar timeout
.Op Fl t Ar type
.Op Ar host | addrlist namelist
.Ar ...
.Ek
.Sh DESCRIPTION
.Nm
is a utility for gathering the public ssh host keys of a number of
is a utility for gathering the public SSH host keys of a number of
hosts.
It was designed to aid in building and verifying
.Pa ssh_known_hosts
@ -39,19 +36,41 @@ uses non-blocking socket I/O to contact as many hosts as possible in
parallel, so it is very efficient.
The keys from a domain of 1,000
hosts can be collected in tens of seconds, even when some of those
hosts are down or do not run ssh.
hosts are down or do not run
.Xr sshd 8 .
For scanning, one does not need
login access to the machines that are being scanned, nor does the
scanning process involve any encryption.
.Pp
Input is expected in the format:
.Bd -literal -offset 3n
1.2.3.4,1.2.4.4 name.my.domain,name,n.my.domain,n,1.2.3.4,1.2.4.4
.Ed
.Pp
The output format is:
.Bd -literal -offset 3n
host-or-namelist keytype base64-encoded-key
.Ed
.Pp
Where
.Ar keytype
is either
.Dq ecdsa-sha2-nistp256 ,
.Dq ecdsa-sha2-nistp384 ,
.Dq ecdsa-sha2-nistp521 ,
.Dq ssh-ed25519 ,
.Dq ssh-dss
or
.Dq ssh-rsa .
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl 4
Forces
Force
.Nm
to use IPv4 addresses only.
.It Fl 6
Forces
Force
.Nm
to use IPv6 addresses only.
.It Fl c
@ -69,32 +88,32 @@ pairs from
.Ar file ,
one per line.
If
.Pa -
.Sq -
is supplied instead of a filename,
.Nm
will read hosts or
.Dq addrlist namelist
pairs from the standard input.
will read from the standard input.
.It Fl H
Hash all hostnames and addresses in the output.
Hashed names may be used normally by
.Nm ssh
.Xr ssh 1
and
.Nm sshd ,
.Xr sshd 8 ,
but they do not reveal identifying information should the file's contents
be disclosed.
.It Fl p Ar port
Port to connect to on the remote host.
Connect to
.Ar port
on the remote host.
.It Fl T Ar timeout
Set the timeout for connection attempts.
If
.Ar timeout
seconds have elapsed since a connection was initiated to a host or since the
last time anything was read from that host, then the connection is
last time anything was read from that host, the connection is
closed and the host in question considered unavailable.
Default is 5 seconds.
The default is 5 seconds.
.It Fl t Ar type
Specifies the type of the key to fetch from the scanned hosts.
Specify the type of the key to fetch from the scanned hosts.
The possible values are
.Dq dsa ,
.Dq ecdsa ,
@ -109,12 +128,10 @@ and
.Dq ed25519
keys.
.It Fl v
Verbose mode.
Causes
.Nm
to print debugging messages about its progress.
Verbose mode:
print debugging messages about progress.
.El
.Sh SECURITY
.Pp
If an ssh_known_hosts file is constructed using
.Nm
without verifying the keys, users will be vulnerable to
@ -125,40 +142,18 @@ On the other hand, if the security model allows such a risk,
can help in the detection of tampered keyfiles or man in the middle
attacks which have begun after the ssh_known_hosts file was created.
.Sh FILES
Input format:
.Bd -literal
1.2.3.4,1.2.4.4 name.my.domain,name,n.my.domain,n,1.2.3.4,1.2.4.4
.Ed
.Pp
Output format for RSA, DSA, ECDSA, and Ed25519 keys:
.Bd -literal
host-or-namelist keytype base64-encoded-key
.Ed
.Pp
Where
.Ar keytype
is either
.Dq ecdsa-sha2-nistp256 ,
.Dq ecdsa-sha2-nistp384 ,
.Dq ecdsa-sha2-nistp521 ,
.Dq ssh-ed25519 ,
.Dq ssh-dss
or
.Dq ssh-rsa .
.Pp
.Pa /etc/ssh/ssh_known_hosts
.Sh EXAMPLES
Print the rsa host key for machine
Print the RSA host key for machine
.Ar hostname :
.Bd -literal
$ ssh-keyscan hostname
.Ed
.Pp
.Dl $ ssh-keyscan -t rsa hostname
.Pp
Find all hosts from the file
.Pa ssh_hosts
which have new or different keys from those in the sorted file
.Pa ssh_known_hosts :
.Bd -literal
.Bd -literal -offset indent
$ ssh-keyscan -t rsa,dsa,ecdsa,ed25519 -f ssh_hosts | \e
sort -u - ssh_known_hosts | diff ssh_known_hosts -
.Ed
@ -176,8 +171,3 @@ $ ssh-keyscan -t rsa,dsa,ecdsa,ed25519 -f ssh_hosts | \e
wrote the initial version, and
.An Wayne Davison Aq Mt wayned@users.sourceforge.net
added support for protocol version 2.
.Sh BUGS
It generates "Connection closed by remote host" messages on the consoles
of all the machines it scans if the server is older than version 2.9.
This is because it opens a connection to the ssh port, reads the public
key, and drops the connection as soon as it gets the key.

4
ssh-keyscan.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: ssh-keyscan.c,v 1.118 2018/02/23 15:58:38 markus Exp $ */
/* $OpenBSD: ssh-keyscan.c,v 1.119 2018/03/02 21:40:15 jmc Exp $ */
/*
* Copyright 1995, 1996 by David Mazieres <dm@lcs.mit.edu>.
*
@ -636,7 +636,7 @@ usage(void)
{
fprintf(stderr,
"usage: %s [-46cDHv] [-f file] [-p port] [-T timeout] [-t type]\n"
"\t\t [host | addrlist namelist] ...\n",
"\t\t [host | addrlist namelist]\n",
__progname);
exit(1);
}