Merge pull request #48 from P403n1x87/fix/where-pipe-permissions

fix: where mode named pipe permissions

Author: P403n1x87

echion/__main__.py

@@ -31,19 +31,24 @@ def detach(pid: int) -> None:
 def attach(args: argparse.Namespace) -> None:
     from hypno import inject_py
 
-    script = dedent(
-        f"""
-        from echion.bootstrap.attach import attach
-        attach({args.__dict__!r})
-        """
-    ).strip()
-
     pid = args.pid or args.where
 
     try:
+        pipe_name = None
         if args.where:
             pipe_name = Path(tempfile.gettempdir()) / f"echion-{pid}"
             os.mkfifo(pipe_name)
+            # This named pipe is likely created by the superuser, so we need to
+            # make it writable by everyone to allow the target process to write
+            # to it.
+            os.chmod(pipe_name, 0o666)
+
+        script = dedent(
+            f"""
+            from echion.bootstrap.attach import attach
+            attach({args.__dict__!r}, {repr(str(pipe_name)) if pipe_name is not None else str(None)})
+            """
+        ).strip()
 
         inject_py(pid, script)
 
@@ -53,6 +58,7 @@ def attach(args: argparse.Namespace) -> None:
                 from time import monotonic as time
 
                 end = time() + args.exposure
+
             while not args.where:
                 try:
                     os.kill(pid, 0)
@@ -61,11 +67,12 @@ def attach(args: argparse.Namespace) -> None:
                 if end is not None and time() > end:
                     break
                 os.sched_yield()
+
         except (KeyboardInterrupt, ProcessLookupError):
             pass
 
         # Read the output
-        if args.where and pipe_name.exists():
+        if args.where and pipe_name is not None and pipe_name.exists():
             with pipe_name.open("r") as f:
                 while True:
                     line = f.readline()
@@ -76,7 +83,7 @@ def attach(args: argparse.Namespace) -> None:
         detach(pid)
 
     finally:
-        if args.where and pipe_name.exists():
+        if args.where and pipe_name is not None and pipe_name.exists():
             pipe_name.unlink()
 
 

echion/bootstrap/attach.py

@@ -6,7 +6,7 @@
 import typing as t
 
 
-def attach(config: t.Dict[str, str]) -> None:
+def attach(config: t.Dict[str, str], pipe_name: t.Optional[str] = None) -> None:
     os.environ["ECHION_CPU"] = str(int(config["cpu"]))
     os.environ["ECHION_NATIVE"] = str(int(config["native"]))
     os.environ["ECHION_OUTPUT"] = config["output"]
@@ -15,6 +15,12 @@ def attach(config: t.Dict[str, str]) -> None:
 
     from echion.bootstrap import start
 
+    # This is used in where mode for IPC.
+    if pipe_name is not None:
+        from echion.core import set_pipe_name
+
+        set_pipe_name(pipe_name)
+
     start()
 
 

echion/config.h

@@ -26,6 +26,9 @@ static int native = 0;
 // Where mode
 static int where = 0;
 
+// Pipe name (where mode IPC)
+static std::string pipe_name;
+
 // ----------------------------------------------------------------------------
 static PyObject *
 set_interval(PyObject *Py_UNUSED(m), PyObject *args)
@@ -77,3 +80,16 @@ set_where(PyObject *Py_UNUSED(m), PyObject *args)
 
     Py_RETURN_NONE;
 }
+
+// ----------------------------------------------------------------------------
+static PyObject *
+set_pipe_name(PyObject *Py_UNUSED(m), PyObject *args)
+{
+    const char *name;
+    if (!PyArg_ParseTuple(args, "s", &name))
+        return NULL;
+
+    pipe_name = name;
+
+    Py_RETURN_NONE;
+}

echion/core.pyi

@@ -23,3 +23,4 @@ def set_interval(interval: int) -> None: ...
 def set_cpu(cpu: bool) -> None: ...
 def set_native(native: bool) -> None: ...
 def set_where(where: bool) -> None: ...
+def set_pipe_name(name: str) -> None: ...

echion/coremodule.cc

@@ -138,15 +138,13 @@ _sampler()
 
     if (where)
     {
-        auto pipe_name = std::filesystem::temp_directory_path() / ("echion-" + std::to_string(getpid()));
         std::ofstream pipe(pipe_name, std::ios::out);
-        if (!pipe)
-        {
-            std::cerr << "Failed to open pipe " << pipe_name << std::endl;
-            return;
-        }
 
-        do_where(pipe);
+        if (pipe)
+            do_where(pipe);
+
+        else
+            std::cerr << "Failed to open pipe " << pipe_name << std::endl;
 
         running = 0;
 
@@ -398,6 +396,7 @@ static PyMethodDef echion_core_methods[] = {
     {"set_cpu", set_cpu, METH_VARARGS, "Set whether to use CPU time instead of wall time"},
     {"set_native", set_native, METH_VARARGS, "Set whether to sample the native stacks"},
     {"set_where", set_where, METH_VARARGS, "Set whether to use where mode"},
+    {"set_pipe_name", set_pipe_name, METH_VARARGS, "Set the pipe name"},
     {NULL, NULL, 0, NULL} /* Sentinel */
 };