From de07dd810164ec5c3d5798b45f0b98f92f9d994d Mon Sep 17 00:00:00 2001
From: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
Date: Sat, 17 Apr 2010 20:16:52 -0400
Subject: [PATCH] do not try to add to known_hosts if HASH_KNOWN_HOSTS is true
 but ssh-keygen is not available (includes some comments about how to fix
 these corner cases).

---
 src/share/common             | 22 +++++++++++++++++-----
 src/share/m/ssh_proxycommand | 12 +++++++++++-
 2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/src/share/common b/src/share/common
index adec5a1..9e40302 100644
--- a/src/share/common
+++ b/src/share/common
@@ -885,13 +885,25 @@ process_host_known_hosts() {
 
 	    # hash if specified
 	    if [ "$HASH_KNOWN_HOSTS" = 'true' ] ; then
+                if (type ssh-keygen >/dev/null) ; then
 		# FIXME: this is really hackish cause ssh-keygen won't
 		# hash from stdin to stdout
-		tmpfile=$(mktemp ${TMPDIR:-/tmp}/tmp.XXXXXXXXXX)
-		ssh2known_hosts "$host" "$sshKey" > "$tmpfile"
-		ssh-keygen -H -f "$tmpfile" 2>/dev/null
-		cat "$tmpfile" >> "$KNOWN_HOSTS"
-		rm -f "$tmpfile" "${tmpfile}.old"
+		    tmpfile=$(mktemp ${TMPDIR:-/tmp}/tmp.XXXXXXXXXX)
+		    ssh2known_hosts "$host" "$sshKey" > "$tmpfile"
+		    ssh-keygen -H -f "$tmpfile" 2>/dev/null
+		    cat "$tmpfile" >> "$KNOWN_HOSTS"
+		    rm -f "$tmpfile" "${tmpfile}.old"
+                else
+       # FIXME: we could do this without needing ssh-keygen.  hashed
+       # known_hosts looks like: |1|X|Y where 1 means SHA1 (nothing
+       # else is defined in openssh sources), X is the salt (same
+       # length as the digest output), base64-encoded, and Y is the
+       # digested hostname (also base64-encoded).
+
+       # see hostfile.{c,h} in openssh sources.
+
+                    failure "Cannot hash known_hosts as requested"
+                fi
 	    else
 		ssh2known_hosts "$host" "$sshKey" >> "$KNOWN_HOSTS"
 	    fi
diff --git a/src/share/m/ssh_proxycommand b/src/share/m/ssh_proxycommand
index 5f7a63b..5fb2ce4 100644
--- a/src/share/m/ssh_proxycommand
+++ b/src/share/m/ssh_proxycommand
@@ -237,7 +237,17 @@ else
         if (type ssh-keygen &>/dev/null) ; then
             hostKey=$(ssh-keygen -F "$HOST" -f "$KNOWN_HOSTS" 2>/dev/null)
         else
-            # FIXME: we're not dealing with digested known_hosts if we don't 
+            # FIXME: we're not dealing with digested known_hosts if we
+            # don't have ssh-keygen
+
+       # But we could do this without needing ssh-keygen.  hashed
+       # known_hosts looks like: |1|X|Y where 1 means SHA1 (nothing
+       # else is defined in openssh sources), X is the salt (same
+       # length as the digest output), base64-encoded, and Y is the
+       # digested hostname (also base64-encoded).
+
+       # see hostfile.{c,h} in openssh sources.
+
             hostKey=$(cut -f1 -d\  < .ssh/known_hosts | tr ',' '\n' | grep -Fx -e "$HOST" || :)
         fi
     fi
-- 
2.26.2