upstream: Add ssh-keyscan -D option to make it print its results in

SSHFP format bz#2821, ok dtucker@

OpenBSD-Commit-ID: 831446b582e0f298ca15c9d99c415c899e392221

2 files changed, 29 insertions, 7 deletions

diff --git a/ssh-keyscan.1 b/ssh-keyscan.1
index aa4a2ae83..cdbce0b30 100644
--- a/ssh-keyscan.1
+++ b/ssh-keyscan.1
@@ -1,4 +1,4 @@
-.\"     $OpenBSD: ssh-keyscan.1,v 1.40 2017/05/02 17:04:09 jmc Exp $
+.\"     $OpenBSD: ssh-keyscan.1,v 1.41 2018/02/23 05:14:05 djm Exp $
 .\"
 .\" Copyright 1995, 1996 by David Mazieres <dm@lcs.mit.edu>.
 .\"
@@ -6,7 +6,7 @@
 .\" permitted provided that due credit is given to the author and the
 .\" OpenBSD project by leaving this copyright notice intact.
 .\"
-.Dd $Mdocdate: May 2 2017 $
+.Dd $Mdocdate: February 23 2018 $
 .Dt SSH-KEYSCAN 1
 .Os
 .Sh NAME
@@ -15,7 +15,7 @@
 .Sh SYNOPSIS
 .Nm ssh-keyscan
 .Bk -words
-.Op Fl 46cHv
+.Op Fl 46cDHv
 .Op Fl f Ar file
 .Op Fl p Ar port
 .Op Fl T Ar timeout
@@ -56,6 +56,12 @@ Forces
 to use IPv6 addresses only.
 .It Fl c
 Request certificates from target hosts instead of plain keys.
+.It Fl D
+Print keys found as SSHFP DNS records.
+The default is to print keys in a format usable as a
+.Xr ssh 1
+.Pa known_hosts
+file.
 .It Fl f Ar file
 Read hosts or
 .Dq addrlist namelist
@@ -159,6 +165,10 @@ $ ssh-keyscan -t rsa,dsa,ecdsa,ed25519 -f ssh_hosts | \e
 .Sh SEE ALSO
 .Xr ssh 1 ,
 .Xr sshd 8
+.%R RFC 4255
+.%T "Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints"
+.%D 2006
+.Re
 .Sh AUTHORS
 .An -nosplit
 .An David Mazieres Aq Mt dm@lcs.mit.edu
diff --git a/ssh-keyscan.c b/ssh-keyscan.c
index a816a220e..15059f6fa 100644
--- a/ssh-keyscan.c
+++ b/ssh-keyscan.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-keyscan.c,v 1.116 2017/11/25 06:46:22 dtucker Exp $ */
+/* $OpenBSD: ssh-keyscan.c,v 1.117 2018/02/23 05:14:05 djm Exp $ */
 /*
  * Copyright 1995, 1996 by David Mazieres <dm@lcs.mit.edu>.
  *
@@ -46,6 +46,7 @@
 #include "hostfile.h"
 #include "ssherr.h"
 #include "ssh_api.h"
+#include "dns.h"
 
 /* Flag indicating whether IPv4 or IPv6.  This can be set on the command line.
    Default value is AF_UNSPEC means both IPv4 and IPv6. */
@@ -66,6 +67,8 @@ int get_keytypes = KT_RSA|KT_ECDSA|KT_ED25519;
 
 int hash_hosts = 0;             /* Hash hostname on output */
 
+int print_sshfp = 0;            /* Print SSHFP records instead of known_hosts */
+
 #define MAXMAXFD 256
 
 /* The number of seconds after which to give up on a TCP connection */
@@ -280,6 +283,11 @@ keyprint_one(const char *host, struct sshkey *key)
         char *hostport;
         const char *known_host, *hashed;
 
+        if (print_sshfp) {
+                export_dns_rr(host, key, stdout, 0);
+                return;
+        }
+
         hostport = put_host_port(host, ssh_port);
         lowercase(hostport);
         if (hash_hosts && (hashed = host_hash(host, NULL, 0)) == NULL)
@@ -497,7 +505,8 @@ congreet(int s)
                 confree(s);
                 return;
         }
-        fprintf(stderr, "# %s:%d %s\n", c->c_name, ssh_port, chop(buf));
+        fprintf(stderr, "%c %s:%d %s\n", print_sshfp ? ';' : '#',
+            c->c_name, ssh_port, chop(buf));
         keygrab_ssh2(c);
         confree(s);
 }
@@ -621,7 +630,7 @@ static void
 usage(void)
 {
         fprintf(stderr,
-            "usage: %s [-46cHv] [-f file] [-p port] [-T timeout] [-t type]\n"
+            "usage: %s [-46cDHv] [-f file] [-p port] [-T timeout] [-t type]\n"
             "\t\t   [host | addrlist namelist] ...\n",
             __progname);
         exit(1);
@@ -650,7 +659,7 @@ main(int argc, char **argv)
         if (argc <= 1)
                 usage();
 
-        while ((opt = getopt(argc, argv, "cHv46p:T:t:f:")) != -1) {
+        while ((opt = getopt(argc, argv, "cDHv46p:T:t:f:")) != -1) {
                 switch (opt) {
                 case 'H':
                         hash_hosts = 1;
@@ -658,6 +667,9 @@ main(int argc, char **argv)
                 case 'c':
                         get_cert = 1;
                         break;
+                case 'D':
+                        print_sshfp = 1;
+                        break;
                 case 'p':
                         ssh_port = a2port(optarg);
                         if (ssh_port <= 0) {