cli: T9077: insert literal '?' inside quoted values instead of triggering help

The '?' key is a raw readline binding (possible-completions), so a
literal question mark can never be typed into a value: readline
intercepts the keystroke before bash parsing begins and quoting cannot
protect it. Values like remote-group URLs with query strings get
silently corrupted ('.../blacklist?key=x' is stored as
'.../blacklistkey=x') with no error at any stage.

Rebind '?' to a bind -x handler that scans the line left of the cursor
for an open single/double quote or a pending backslash escape. Inside a
quote or escape the key self-inserts; otherwise it triggers the
standard help via a DSR round-trip (printf '\e[5n' with the terminal's
reply ESC [ 0 n bound to possible-completions), keeping the help path
and output identical to the previous behavior.

'set terminal key query-help enable' now restores the quote-aware
handler instead of the raw binding; 'disable' keeps its existing
self-insert override, which takes precedence at login as before.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

2 files changed, 37 insertions, 2 deletions

diff --git a/src/etc/bash_completion.d/vyatta-op b/src/etc/bash_completion.d/vyatta-op
index cedbcfbc1..11f0db6ed 100644
--- a/src/etc/bash_completion.d/vyatta-op
+++ b/src/etc/bash_completion.d/vyatta-op
@@ -35,6 +35,39 @@ test -z "$_vyatta_default_pager" && \
 test -z "$VYATTA_PAGER" && \
     declare -x VYATTA_PAGER=$_vyatta_default_pager
 
+# Handler for the '?' key. Outside of a quoted string, '?' shows the
+# completion help as before. Inside a quoted string (or after a
+# backslash), it self-inserts, so values like URLs with query strings
+# can be typed without Ctrl-V:
+#   set firewall group remote-group X url 'https://example.com/list?key=abc'
+_vyatta_question_mark ()
+{
+  local head=${READLINE_LINE:0:READLINE_POINT}
+  local i c in_sq='' in_dq='' esc=''
+  for (( i=0; i<${#head}; i++ )); do
+    c=${head:i:1}
+    if [[ -n $esc ]]; then
+      esc=''
+      continue
+    fi
+    case $c in
+      \\) [[ -z $in_sq ]] && esc=1 ;;
+      \') [[ -z $in_dq ]] && { [[ -n $in_sq ]] && in_sq='' || in_sq=1; } ;;
+      \") [[ -z $in_sq ]] && { [[ -n $in_dq ]] && in_dq='' || in_dq=1; } ;;
+    esac
+  done
+  if [[ -n $in_sq || -n $in_dq || -n $esc ]]; then
+    READLINE_LINE=${READLINE_LINE:0:READLINE_POINT}\?${READLINE_LINE:READLINE_POINT}
+    (( READLINE_POINT++ ))
+  else
+    # 'bind -x' handlers cannot invoke readline functions directly, so
+    # ask the terminal for a Device Status Report (DSR); the terminal's
+    # reply (ESC [ 0 n) is bound to possible-completions below, which
+    # re-enters the standard help path with the line unchanged.
+    printf '\e[5n'
+  fi
+}
+
 _vyatta_op_do_key_bindings ()
 {
   if [[ "$SHELL" != "/bin/vbash" && "$SHELL" != "/sbin/radius_shell" ]]; then
@@ -45,7 +78,8 @@ _vyatta_op_do_key_bindings ()
   shopt -u nullglob
   case "$-" in
     *i*)
-      bind '"?": possible-completions'
+      bind -x '"?": _vyatta_question_mark'
+      bind '"\e[0n": possible-completions'
       bind 'set show-all-if-ambiguous on'
       bind_cmds=$(grep '^bind .* # vyatta key binding$' $HOME/.bashrc)
       eval $bind_cmds
diff --git a/src/op_mode/toggle_help_binding.sh b/src/op_mode/toggle_help_binding.sh
index 7c8bc05ce..23550bff6 100755
--- a/src/op_mode/toggle_help_binding.sh
+++ b/src/op_mode/toggle_help_binding.sh
@@ -21,5 +21,6 @@ if [ "$1" == 'disable' ]; then
   bind '"?": self-insert'
 else
   sed -i "/^bind '\"?\": .* # vyatta key binding$/d" $HOME/.bashrc
-  bind '"?": possible-completions'
+  # default binding: quote-aware help handler from bash_completion.d/vyatta-op
+  bind -x '"?": _vyatta_question_mark'
 fi