[profile] / hacks / ssh

#! /bin/bash
###
### SSH wrapper to spawn separate SSH master connections on demand
###
### (c) 2010 Mark Wooding
###

###----- Licensing notice ---------------------------------------------------
###
### This program is free software; you can redistribute it and/or modify
### it under the terms of the GNU General Public License as published by
### the Free Software Foundation; either version 2 of the License, or
### (at your option) any later version.
###
### This program is distributed in the hope that it will be useful,
### but WITHOUT ANY WARRANTY; without even the implied warranty of
### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
### GNU General Public License for more details.
###
### You should have received a copy of the GNU General Public License
### along with this program; if not, write to the Free Software Foundation,
### Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

###--------------------------------------------------------------------------
### Configuration.

: ${REAL_SSH=/usr/bin/ssh}

###--------------------------------------------------------------------------
### Parse the command line and dredge out information.

## This is a reasonable approximation to SSH's command-line argument parser.
unset host login
mode=m
declare -a opts masteropts
while :; do
  case "$1,$#" in

    ## Nothing left.  We're done.
    ,0)
      break
      ;;

    ## A command line option group.  Parse it and work out what's going on.
    -*)
      opt=$1
      opts=("${opts[@]}" "$opt")
      while :; do

	## Strip off the first character, because it's the one we dealt with
	## last time.
	opt=${opt#?}
	o=$opt

	## Phase 1: identify the option and whether it needs an argument.
	unset arg
	case "$o" in

	  ## Empty group.  We're done.
	  "")
	    break
	    ;;

	  ## Options with arguments.
	  [bcDeFiLlmOopRSw]*)
	    case "$#,$o" in

	      ## You're going to lose because there's no argument.  But we'll
	      ## let SSH deal with that.
	      1,?)
		arg=
		;;

	      ## There's an argument cuddled on to the end of the option.  It
	      ## will have been committed to the `opts' array as part of the
	      ## option group.
	      *,??*)
		arg=${opt#?}
		opt=
		;;

	      ## Nope.  There's an argument in the next word.  Grab it and
	      ## commit it.
	      *)
		arg="$2"
		opts=("${opts[@]}" "$arg")
		shift
		;;
	    esac
	    ;;

	  ## Anything else.  Let it go even if it's not valid: SSH will moan
	  ## if it wants.  Note that `--' is ignored by SSH, but this isn't
	  ## documented; in particular, `--' is /not/ a POSIX end-of-options
	  ## marker, so we don't try to handle it specially here either.
	  *)
	    ;;
	esac

	## Phase two.  Figure out whether what this means for us.
	case "$mode,$o" in

	  ## `-O foo' and `-S foo' mean that the caller wants to take
	  ## control of the multiplexing process.
	  ?,[MOS]*)
	    mode=p
	    ;;

	  ## Catch the login name if there is one.  Make sure the master
	  ## knows it.
	  ?,l*)
	    masteropts=("${masteropts[@]}" "-l$arg")
	    login=$arg
	    ;;

	  ## These options are interesting to the master connection.
	  m,[aADLlRSwxXv]*)
	    masteropts=("${masteropts[@]}" "-${o:0:1}$arg")
	    ;;

	  ## SSH options on the command line merit special attention.  Pass
	  ## them onto the master, if necessary.
	  ?,o*)
	    masteropts=("${masteropts[@]}" "${opt:0:1}$arg")
	    case "$mode,$arg" in

	      ## User wants to control the process.  Let him.
	      ?,ControlMaster=* | ?,ControlPath=*)
		mode=p
		;;

	    esac
	    ;;
	esac
      done
      ;;

    ## A bare word.  Maybe it's the hostname, or the start of the command.
    *)
      case ${host-t} in
	t) host=$1 ;;
	*) break ;;
      esac
      ;;
  esac
  shift
done

###--------------------------------------------------------------------------
### Now to actually do the job.

## If there's no host, pass straight through.  We can't do anything useful
## anyway.
case ${host+t} in
  t) ;;
  *) mode=p ;;
esac

## Actually do something useful.
case "$mode" in
  p)
    exec "$REAL_SSH" "${opts[@]}" ${host+"$host"} "$@"
    ;;
  m)
    if ! "$REAL_SSH" -Ocheck ${login+"$login@"}"$host" >/dev/null 2>&1; then
      "$REAL_SSH" -MNf "${masteropts[@]}" "$host"
    fi
    exec "$REAL_SSH" ${opts[@]} "$host" "$@"
    ;;
esac

###----- That's all, folks --------------------------------------------------
Commit	Line	Data
4d7d040b MW	1	#! /bin/bash
	2	###
	3	### SSH wrapper to spawn separate SSH master connections on demand
	4	###
	5	### (c) 2010 Mark Wooding
	6	###
	7
	8	###----- Licensing notice ---------------------------------------------------
	9	###
	10	### This program is free software; you can redistribute it and/or modify
	11	### it under the terms of the GNU General Public License as published by
	12	### the Free Software Foundation; either version 2 of the License, or
	13	### (at your option) any later version.
	14	###
	15	### This program is distributed in the hope that it will be useful,
	16	### but WITHOUT ANY WARRANTY; without even the implied warranty of
	17	### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	18	### GNU General Public License for more details.
	19	###
	20	### You should have received a copy of the GNU General Public License
	21	### along with this program; if not, write to the Free Software Foundation,
	22	### Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
	23
	24	###--------------------------------------------------------------------------
	25	### Configuration.
	26
	27	: ${REAL_SSH=/usr/bin/ssh}
	28
	29	###--------------------------------------------------------------------------
	30	### Parse the command line and dredge out information.
	31
	32	## This is a reasonable approximation to SSH's command-line argument parser.
	33	unset host login
	34	mode=m
	35	declare -a opts masteropts
	36	while :; do
	37	case "$1,$#" in
	38
	39	## Nothing left. We're done.
	40	,0)
	41	break
	42	;;
	43
	44	## A command line option group. Parse it and work out what's going on.
	45	-*)
	46	opt=$1
	47	opts=("${opts[@]}" "$opt")
	48	while :; do
	49
	50	## Strip off the first character, because it's the one we dealt with
	51	## last time.
	52	opt=${opt#?}
	53	o=$opt
	54
	55	## Phase 1: identify the option and whether it needs an argument.
	56	unset arg
	57	case "$o" in
	58
	59	## Empty group. We're done.
	60	"")
	61	break
	62	;;
	63
	64	## Options with arguments.
65	[bcDeFiLlmOopRSw]*)
66	case "$#,$o" in
67
68	## You're going to lose because there's no argument. But we'll
69	## let SSH deal with that.
70	1,?)
71	arg=
72	;;
73
74	## There's an argument cuddled on to the end of the option. It
75	## will have been committed to the `opts' array as part of the
76	## option group.
77	,??)
78	arg=${opt#?}
79	opt=
80	;;
81
82	## Nope. There's an argument in the next word. Grab it and
83	## commit it.
84	*)
85	arg="$2"
86	opts=("${opts[@]}" "$arg")
87	shift
88	;;
89	esac
90	;;
91
92	## Anything else. Let it go even if it's not valid: SSH will moan
93	## if it wants. Note that `--' is ignored by SSH, but this isn't
94	## documented; in particular, `--' is /not/ a POSIX end-of-options
95	## marker, so we don't try to handle it specially here either.
96	*)
97	;;
98	esac
99
100	## Phase two. Figure out whether what this means for us.
101	case "$mode,$o" in
102
103	## `-O foo' and `-S foo' mean that the caller wants to take
104	## control of the multiplexing process.
105	?,[MOS]*)
106	mode=p
107	;;
108
109	## Catch the login name if there is one. Make sure the master
110	## knows it.
111	?,l*)
112	masteropts=("${masteropts[@]}" "-l$arg")
113	login=$arg
114	;;
115
116	## These options are interesting to the master connection.
117	m,[aADLlRSwxXv]*)
118	masteropts=("${masteropts[@]}" "-${o:0:1}$arg")
119	;;
120
121	## SSH options on the command line merit special attention. Pass
122	## them onto the master, if necessary.
123	?,o*)
124	masteropts=("${masteropts[@]}" "${opt:0:1}$arg")
125	case "$mode,$arg" in
126
127	## User wants to control the process. Let him.
128	?,ControlMaster=* \| ?,ControlPath=*)
129	mode=p
130	;;
131
132	esac
133	;;
134	esac
135	done
136	;;
137
138	## A bare word. Maybe it's the hostname, or the start of the command.
139	*)
140	case ${host-t} in
141	t) host=$1 ;;
142	*) break ;;
143	esac
144	;;
145	esac
146	shift
147	done
148
149	###--------------------------------------------------------------------------
150	### Now to actually do the job.
151
152	## If there's no host, pass straight through. We can't do anything useful
153	## anyway.
154	case ${host+t} in
155	t) ;;
156	*) mode=p ;;
157	esac
158
159	## Actually do something useful.
160	case "$mode" in
161	p)
162	exec "$REAL_SSH" "${opts[@]}" ${host+"$host"} "$@"
163	;;
164	m)
165	if ! "$REAL_SSH" -Ocheck ${login+"$login@"}"$host" >/dev/null 2>&1; then
166	"$REAL_SSH" -MNf "${masteropts[@]}" "$host"
167	fi
168	exec "$REAL_SSH" ${opts[@]} "$host" "$@"
169	;;
170	esac
171
172	###----- That's all, folks --------------------------------------------------