win32: changes to '#!' support

Since the earliest days of busybox-w32 '#!' has searched PATH for
the interpreter.  This doesn't seem to be supported by precedent.
In testing I also found that additional code was needed for the case
where PATH has been altered in the current shell or is modified on
the command line:  PATH has to be extracted from envp rather than
getenv("PATH").  Drop this non-standard feature.

*NIX implementations disagree on whether the interpreter can itself
be a script.  Follow Linux and allow this with a limit of four levels
of nesting.

2 files changed, 13 insertions, 12 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 4f1fe005b..c6f64e202 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -22,8 +22,7 @@
  * - Environment variables from Windows will all be turned to uppercase.
  * - PATH accepts both ; and : as separator, but can't be mixed
  * - command without ".exe" extension is still understood as executable
- * - shell scripts on the path are detected by the presence of '#!';
- *   the path to the interpreter is ignored, PATH is searched to find it
+ * - shell scripts on the path are detected by the presence of '#!'
  * - both / and \ are supported in PATH. Usually you must use /
  * - trap/job does not work
  * - /dev/null is supported for redirection
diff --git a/win32/process.c b/win32/process.c
index 28df33c23..d33f06405 100644
--- a/win32/process.c
+++ b/win32/process.c
@@ -292,7 +292,8 @@ mingw_spawn_applet(int mode,
 #endif
 
 static intptr_t
-mingw_spawn_interpreter(int mode, const char *prog, char *const *argv, char *const *envp)
+mingw_spawn_interpreter(int mode, const char *prog, char *const *argv,
+                        char *const *envp, int level)
 {
         intptr_t ret;
         int nopts;
@@ -304,6 +305,11 @@ mingw_spawn_interpreter(int mode, const char *prog, char *const *argv, char *con
         if (!parse_interpreter(prog, &interp))
                 return spawnveq(mode, prog, argv, envp);
 
+        if (++level > 4) {
+                errno = ELOOP;
+                return -1;
+        }
+
         nopts = interp.opts != NULL;
         argc = string_array_len((char **)argv);
         new_argv = xmalloc(sizeof(*argv)*(argc+nopts+2));
@@ -314,7 +320,7 @@ mingw_spawn_interpreter(int mode, const char *prog, char *const *argv, char *con
         if ((fullpath=alloc_win32_extension(interp.path)) != NULL ||
                         file_is_executable(interp.path)) {
                 new_argv[0] = fullpath ? fullpath : interp.path;
-                ret = spawnveq(mode, new_argv[0], new_argv, envp);
+                ret = mingw_spawn_interpreter(mode, new_argv[0], new_argv, envp, level);
         } else
 #if ENABLE_FEATURE_PREFER_APPLETS || ENABLE_FEATURE_SH_STANDALONE
         if (find_applet_by_name(interp.name) >= 0) {
@@ -323,11 +329,7 @@ mingw_spawn_interpreter(int mode, const char *prog, char *const *argv, char *con
                 ret = mingw_spawn_applet(mode, new_argv, envp);
         } else
 #endif
-        if ((fullpath=find_first_executable(interp.name)) != NULL) {
-                new_argv[0] = fullpath;
-                ret = spawnveq(mode, fullpath, new_argv, envp);
-        }
-        else {
+        {
                 errno = ENOENT;
                 ret = -1;
         }
@@ -349,10 +351,10 @@ mingw_spawn_1(int mode, const char *cmd, char *const *argv, char *const *envp)
 #endif
         if (strchr(cmd, '/') || strchr(cmd, '\\') || has_dos_drive_prefix(cmd)) {
                 const char *path = auto_win32_extension(cmd);
-                return mingw_spawn_interpreter(mode, path ? path : cmd, argv, envp);
+                return mingw_spawn_interpreter(mode, path ? path : cmd, argv, envp, 0);
         }
         else if ((prog=find_first_executable(cmd)) != NULL) {
-                intptr_t ret = mingw_spawn_interpreter(mode, prog, argv, envp);
+                intptr_t ret = mingw_spawn_interpreter(mode, prog, argv, envp, 0);
                 free(prog);
                 return ret;
         }
@@ -401,7 +403,7 @@ mingw_execvp(const char *cmd, char *const *argv)
 int
 mingw_execve(const char *cmd, char *const *argv, char *const *envp)
 {
-        int ret = (int)mingw_spawn_interpreter(P_WAIT, cmd, argv, envp);
+        int ret = (int)mingw_spawn_interpreter(P_WAIT, cmd, argv, envp, 0);
         if (ret != -1)
                 exit(ret);
         return ret;