system: In resolve command, check that found element is a file

src/core/opamSystem.ml

@@ -441,11 +441,11 @@ let t_resolve_command =
     else fun f ->
       try
         let open Unix in
-        let uid = geteuid () in
+        let {st_uid; st_gid; st_perm; st_kind; _} = stat f in
+        if st_kind <> Unix.S_REG then false else
         let groups = OpamStd.IntSet.of_list (getegid () :: Array.to_list (getgroups ())) in
-        let {st_uid; st_gid; st_perm; _} = stat f in
         let mask =
-          if uid = st_uid then
+          if geteuid () = st_uid then
             0o100
           else if OpamStd.IntSet.mem st_gid groups then
             0o010
@@ -488,9 +488,12 @@ let t_resolve_command =
         name ^ ".exe"
       else name
     in
-    let possibles = OpamStd.List.filter_map (fun path ->
-        let candidate = Filename.concat path name in
-        if Sys.file_exists candidate then Some candidate else None) path
+    let possibles =
+      OpamStd.List.filter_map (fun path ->
+          let candidate = Filename.concat path name in
+          if Sys.file_exists candidate && not (Sys.is_directory candidate) then
+            Some candidate else None)
+        path
     in
     match List.find check_perms possibles with
     | cmdname -> `Cmd cmdname

tests/reftests/core-system.test

@@ -12,11 +12,9 @@ system
 ### mkdir -p bin/echo
 ### PATH=$BASEDIR/bin/:${PATH}
 ### opam exec -- echo system
-Fatal error: exception ${OPAM}: "execvpe" failed on ${BASEDIR}/bin/echo: Permission denied
-# Return code 2 #
+system
 ### opam exec --no-switch -- echo system
-Fatal error: exception ${OPAM}: "execvpe" failed on ${BASEDIR}/bin/echo: Permission denied
-# Return code 2 #
+system
 ### :I:c: is not executable
 ### rm -rf bin/echo
 ### <bin/echo>