fix(agent-setup): stop agent wrappers from resolving themselves as the real binary

packages/agent-setup/src/agent-wrappers-common.ts

@@ -5,9 +5,19 @@ import { ARTIFACT_GUARD_SCRIPT_NAME } from "./artifact-guard-hook";
 import { NOTIFY_SCRIPT_NAME } from "./notify-hook";
 import { getBinDir } from "./paths";
 
-export const WRAPPER_MARKER = "# Superset agent-wrapper v5";
 export { SUPERSET_MANAGED_BINARIES };
 
+export const WRAPPER_MARKER_PREFIX = "# Superset agent-wrapper";
+export const WRAPPER_MARKER = `${WRAPPER_MARKER_PREFIX} v5`;
+
+/** Wrapper passes allowed per binary in one process tree before it refuses to run. */
+export const MAX_WRAPPER_NESTING = 8;
+export const WRAPPER_LOOP_EXIT_STATUS = 126;
+
+export function getWrapperDepthVar(binaryName: string): string {
+	return `SUPERSET_WRAPPER_DEPTH_${binaryName.replace(/[^A-Za-z0-9]/g, "_")}`;
+}
+
 /** Path (under SUPERSET_HOME_DIR) of the runtime notify hook script. */
 export const MANAGED_NOTIFY_RELATIVE_PATH = `hooks/${NOTIFY_SCRIPT_NAME}`;
 
@@ -117,26 +127,58 @@ export function isManagedArtifactGuardCommand(
 	);
 }
 
+/**
+ * A candidate is never the real binary when it is this wrapper (`-ef` follows
+ * symlinks, so aliased bin dirs, links elsewhere on PATH and relative or
+ * duplicate entries all match) or any other Superset wrapper, found by the
+ * marker on its second line. Neither check depends on HOME or on where the
+ * wrapper was generated.
+ */
 function buildRealBinaryResolver(): string {
 	return `find_real_binary() {
   local name="$1"
   local IFS=:
+  local dir candidate first_line marker_line
   for dir in $PATH; do
     [ -z "$dir" ] && continue
     dir="\${dir%/}"
     case "$dir" in
       "${getBinDir()}"|"$HOME"/.paradev/bin|"$HOME"/.paradev-*/bin|"$HOME"/.superset/bin|"$HOME"/.superset-*/bin) continue ;;
     esac
-    if [ -x "$dir/$name" ] && [ ! -d "$dir/$name" ]; then
-      printf "%s\\n" "$dir/$name"
-      return 0
-    fi
+    candidate="$dir/$name"
+    [ -x "$candidate" ] && [ ! -d "$candidate" ] || continue
+    [ "$candidate" -ef "$0" ] && continue
+    marker_line=""
+    { IFS= read -r -n 256 first_line; IFS= read -r -n 256 marker_line; } 2>/dev/null <"$candidate"
+    case "$marker_line" in
+      "${WRAPPER_MARKER_PREFIX}"*) continue ;;
+    esac
+    printf "%s\\n" "$candidate"
+    return 0
   done
   return 1
 }
 `;
 }
 
+/**
+ * Last line of defense if the resolver ever lets the wrapper find itself: the
+ * counter lives in the environment, which every re-entry inherits (child or
+ * exec), so the loop ends after a few passes with a clear message.
+ */
+function buildLoopGuard(binaryName: string): string {
+	const depthVar = getWrapperDepthVar(binaryName);
+	return `_superset_depth="\${${depthVar}:-0}"
+case "$_superset_depth" in *[!0-9]*) _superset_depth=0 ;; esac
+if [ "$_superset_depth" -ge ${MAX_WRAPPER_NESTING} ]; then
+  echo "Paradev: ${binaryName} wrapper re-entered itself ${MAX_WRAPPER_NESTING} times; a PATH entry resolves ${binaryName} back to this wrapper ($0). Remove it from PATH." >&2
+  exit ${WRAPPER_LOOP_EXIT_STATUS}
+fi
+export ${depthVar}=$((10#$_superset_depth + 1))
+
+`;
+}
+
 /**
  * Shell block that re-resolves the Usage-tab default account at launch.
  * The PTY env is frozen at terminal spawn, so an account switch would
@@ -259,7 +301,7 @@ ${buildLaunchReportBlock()}fi
 ${WRAPPER_MARKER}
 # Superset wrapper for ${binaryName}
 
-${buildRealBinaryResolver()}
+${buildLoopGuard(binaryName)}${buildRealBinaryResolver()}
 REAL_BIN="$(find_real_binary "${binaryName}")"
 if [ -z "$REAL_BIN" ]; then
   echo "${getMissingBinaryMessage(binaryName)}" >&2