address review feedback

cmd/snap-exec/main.go

@@ -89,14 +89,16 @@ func run() error {
 	return snapExecApp(snapApp, revision, opts.Command, extraArgs)
 }
 
+const defaultShell = "/bin/bash"
+
 func findCommand(app *snap.AppInfo, command string) (string, error) {
 	var cmd string
 	switch command {
 	case "shell":
-		cmd = "/bin/bash"
+		cmd = defaultShell
 	case "complete":
 		if app.Completer != "" {
-			cmd = "/bin/bash"
+			cmd = defaultShell
 		}
 	case "stop":
 		cmd = app.StopCommand
@@ -153,10 +155,10 @@ func snapExecApp(snapApp, revision, command string, args []string) error {
 	fullCmd := filepath.Join(app.Snap.MountDir(), cmd)
 	switch command {
 	case "shell":
-		fullCmd = "/bin/bash"
+		fullCmd = defaultShell
 		cmdArgs = nil
 	case "complete":
-		fullCmd = "/bin/bash"
+		fullCmd = defaultShell
 		cmdArgs = []string{
 			dirs.CompletionHelper,
 			filepath.Join(app.Snap.MountDir(), app.Completer),

data/completion/complete.sh

@@ -6,7 +6,32 @@
 _complete_from_snap() {
     {
         read -a opts
+        # opts is expected to be a series of compopt options
+        if [[ ${#opts[@]} -gt 0 ]]; then
+            if [[ "${opts[0]}" == "cannot" ]]; then
+                # older snap-execs sent errors over stdout :-(
+                return 1
+            fi
+
+            for i in "${opts[@]}"; do
+                if ! [[ "$i" =~ ^[a-z]+$ ]]; then
+                    # non-alphanumeric option; something awry
+                    return 2
+                fi
+            done
+        fi
+
         read bounced
+        case "$bounced" in
+            ""|"alias"|"export"|"job"|"variable")
+                # OK
+                ;;
+            *)
+                # unrecognised bounce
+                return 2
+                ;;
+        esac
+
         read sep
         if [ "$sep" ]; then
             # non-blank separator? madness!
@@ -21,10 +46,6 @@ _complete_from_snap() {
         fi
 
         if [[ ${#opts[@]} -gt 0 ]]; then
-            if [[ "${opts[0]}" == "cannot" ]]; then
-                # older snap-execs sent errors over stdout :-(
-                return 1
-            fi
             compopt $(printf " -o %s" "${opts[@]}")
         fi
         if [ "$bounced" ]; then

data/completion/etelpmoc.sh

@@ -48,7 +48,7 @@ fi
 
 . /usr/share/bash-completion/bash_completion
 
-. $_compscript
+. "$_compscript"
 
 # _compopts is an associative array, which keys are options.
 declare -A _compopts

interfaces/apparmor/template.go

@@ -201,8 +201,7 @@ var defaultTemplate = `
   /usr/lib/snapd/snap-exec m,
 
   # For in-snap tab completion
-  /etc/bash_completion.d/ r,
-  /etc/bash_completion.d/* r,
+  /etc/bash_completion.d/{,*} r,
   /usr/lib/snapd/etelpmoc.sh ixr,               # marshaller (see complete.sh for out-of-snap unmarshal)
   /usr/share/bash-completion/bash_completion r, # user-provided completions (run in-snap) may use functions from here