zsh/Completion/User/_ssh

#compdef ssh ssh-add ssh-agent ssh-keygen

local state lstate line ret=1 expl
typeset -A options

case "$words[1]" in
ssh)
  _arguments -s \
    '-a[disable forwarding of authentication agent connection]' \
    '-c[select encryption cipher]:encryption cipher:(idea des 3des blowfish arcfour tss none)' \
    '-e[set escape character]:escape character (or `none'"'"'):' \
    '(-n)-f[go to background]' \
    '-i[select identity file]:SSH identity file:_files' \
    '-k[disable forwarding of kerberos tickets]' \
    '-l[specify login name]:login name:_users' \
    '-n[redirect stdin from /dev/null]' \
    '*-o[specify extra options]:option string:->option' \
    '-p[specify port on remote host]:port number on remote host:' \
    '-q[quiet operation]' \
    '-P[use non priviledged port]' \
    '-t[force pseudo-tty allocation]' \
    '-v[verbose mode]' \
    '-V[show version number]' \
    '-x[disable X11 forwarding]' \
    '-C[compress all data]' \
    '-L[specify local port forwarding]:local port forwarding:->forward' \
    '-R[specify remote port forwarding]:remote port forwarding:->forward' \
    ':remote host name:_hosts' \
    ':command: _command_names -e' \
    '*::args:->command' && ret=0

  while [[ -n "$state" ]]; do
    lstate="$state"
    state=''

    case "$lstate" in
    option)
      if compset -P '* '; then
        case "$IPREFIX" in
        *(#i)(batchmode|compression|fallbacktorsh|forward(agent|x11)|keepalive|passwordauthentication|rhosts(|rsa)authentication|rsaauthentication|usersh|kerberos(authetication|tgtparsing)|usepriviledgedport)*)
          compadd yes no && ret=0
  	;;
        *(#i)cipher*)
          _description expl 'encryption cipher'
          compadd "$expl[@]" idea des 3des blowfish arcfour tss none && ret=0
          ;;
        *(#i)globalknownhostsfile*)
          _description expl 'global file with known hosts'
          _files "$expl[@]" && ret=0
          ;;
        *(#i)hostname*)
          _description expl 'real host name to log into'
          _hosts "$expl[@]" && ret=0
          ;;
        *(#i)identityfile*)
          _description expl 'SSH identity file'
          _files "$expl[@]" && ret=0
          ;;
        *(#i)(local|remote)forward*)
          state=forward
          ;;
        *(#i)proxycommand*)
          compset -q
  	  shift 1 words
	  (( CURRENT-- ))
          _normal && ret=0
          ;;
        *(#i)stricthostkeychecking*)
          compadd yes no ask
          ;;
        *(#i)userknownhostsfile*)
          _description expl 'user file with known hosts'
          _files "$expl[@]" && ret=0
          ;;
        *(#i)user*)
          _description expl 'user to log in as'
          _users "$expl[@]" && ret=0
          ;;
        *(#i)xauthlocation*)
          _description expl 'xauth program'
          _files "$expl[@]" -g '*(*)' && ret=0
          ;;
        esac
      else
        _description expl 'configure file option'
        compadd "$expl[@]" -M 'm:{a-z}={A-Z}' -S ' ' - \
                BatchMode ClearAllForwardings Cipher Compression CompressionLevel \
	        Host ConnectionAttempts EscapeChar FallBackToRsh ForwardAgent \
	        ForwardX11 GlobalKnownHostsFile HostName IdentityFile KeepAlive \
	        KerberosAuthentication KerberosTgtPassing LocalForward \
	        NumberOfPasswordPrompts PasswordAuthentication Port ProxyCommand \
	        RemoteForward RhostsAuthentication RhostsRSAAuthentication \
	        RSAAuthentication StrictHostKeyChecking TISAuthentication \
	        UsePriviledgedPort User UserKnownHostsFile UseRsh \
                XAuthLocation && ret=0
      fi
      ;;
    forward)
      if compset -P 1 '*:'; then
        if compset -P '*:'; then
          _message 'port number'
        else
          _hosts -S:
        fi
      else
        _message 'listen-port number'
      fi
      return
      ;;
    command)
      shift 1 words
      (( CURRENT-- ))
      _normal
      return
      ;;
    esac

    break;
  done

  return ret
  ;;
ssh-add)
  _arguments -s \
    '-p[read passphrase from stdin]' \
    '-l[list all identities]' \
    '-d[remove identity]' \
    '-D[delete all identities]' \
    '*:SSH identity file:_files'
  return
  ;;
ssh-agent)
  _arguments -s \
    '(:)-k[kill agent automatically]' \
    '(:)-s[force sh-style shell]' \
    '(:)-c[force csh-style shell]' \
    '*::command: _normal'
  return
  ;;
ssh-keygen)
  _arguments \
    '(-p -c -u -P)-b[specify number of bits in key]:bits in key:' \
    '(-p -c)-f[key file]:key file:_files' \
    '(-c -u)-N[specify new passphrase]:new passphrase:' \
    '(-b -u -f)-P[specify old passphrase]:old passphrase:' \
    '(-p -u)-C[specify new comment]:new comment:' \
    '(-b -f -C -u -c)-p[change passphrase of private key file]' \
    '(-b -f -N -p -u)-c[change comment in private and public key files]' \
    '(-b -N -C -p -c)-u[change key cipher to default]'
  return
  ;;
esac