bunpen: implement BUNPEN_DISABLE=1 env var to bypass sandboxing

pkgs/additional/bunpen/config/cli.ha

@@ -10,6 +10,7 @@ export type cli_opts = struct {
   cmd: []str,
   // `--bunpen-debug`
   debug: uint,
+  disable: bool,
   drop_shell: bool,
   // `--bunpen-help`
   help: bool,
@@ -80,6 +81,13 @@ export fn usage() void = {
 export fn parse_args(args: []str) (cli_opts | errors::invalid) = {
   let parsed = cli_opts { autodetect = void, ... };
 
+  let dis = match (os::getenv("BUNPEN_DISABLE")) {
+    case let d: str => yield d;
+    case void => yield "";
+  };
+  if (dis != "" && dis != "0")
+    parsed.disable = true;
+
   for (let idx: size = 0; idx < len(args); idx += 1) {
     let arg = args[idx];
     let next: nullable *str = null;

pkgs/additional/bunpen/config/translate_opts.ha

@@ -15,44 +15,61 @@ use rt::ext;
 export type help = void;
 
 export type cli_request = struct {
-  // args to invoke the binary with.
-  // `exec_args[0]` is, by convention, the name of the executable,
-  // relevant for multi-call binaries like `busybox`.
-  exec_args: []str,
-  // path to the binary to be exec'd inside the sandbox.
-  // if the user requested `--bunpen-drop-shell`, this will be their shell (e.g. /bin/sh).
-  exec_bin: str,
+  exec_params: exec_params,
   // what to keep in the restricted environment (paths, network, etc)
   resources: restrict::resources,
 };
 
-export fn ingest_cli_opts(opts: cli_opts) (cli_request | help) = {
-  let req = cli_request { ... };
+export type exec_params = struct {
+  // args to invoke the binary with.
+  // `args[0]` is, by convention, the name of the executable,
+  // relevant for multi-call binaries like `busybox`.
+  args: []str,
+  // path to the binary to be exec'd inside the sandbox.
+  // if the user requested `--bunpen-drop-shell`, this will be their shell (e.g. /bin/sh), assuming `BUNPEN_DISABLE=1` wasn't specified.
+  bin: str,
+};
 
+fn cli_opts_get_exec_params(opts: cli_opts) exec_params = {
+  let params = exec_params { ... };
   //---- ingest `cmd` ----//
   if (len(os::args) > 0) {
     // forward argv0
-    append(req.exec_args, os::args[0]);
+    append(params.args, os::args[0]);
   };
 
   let saw_bin_path = false;
   for (let arg .. opts.cmd) {
     if (saw_bin_path) {
-      append(req.exec_args, arg);
+      append(params.args, arg);
     } else {
-      req.exec_bin = arg;
+      params.bin = arg;
       saw_bin_path = true;
     };
   };
 
+  return params;
+};
+
+export fn ingest_cli_opts(opts: cli_opts) (cli_request | exec_params | help) = {
+  let req = cli_request { ... };
+
   //---- ingest `help` ----//
   if (opts.help) {
     return help;
   };
 
+  //---- ingest opts.cmd ----//
+  req.exec_params = cli_opts_get_exec_params(opts);
+
+  //---- ingest `disable` ----//
+  if (opts.disable)
+    return req.exec_params;
+
   //---- ingest `caps` ----//
   req.resources.caps = restrict::cap_array_to_caps(opts.keep_caps);
 
+
   //---- ingest `home_paths` ----//
   ingest_paths(&req.resources.paths, opts.home_paths, os::getenv("HOME"));
   //---- ingest `keep_all_caps` ----//
@@ -71,12 +88,12 @@ export fn ingest_cli_opts(opts: cli_opts) (cli_request | help) = {
   //---- ingest `run_paths` ----//
   ingest_paths(&req.resources.paths, opts.run_paths, os::getenv("XDG_RUNTIME_DIR"));
 
-  //---- ingest `autodetect` (must be done after exec_args) ----//
+  //---- ingest `autodetect` (must be done after exec_params) ----//
   match (opts.autodetect) {
     case let method: autodetect =>
       // N.B.: skip first arg, since that's the name of the executable and
       // surely not an argument
-      ingest_paths(&req.resources.paths, req.exec_args[1..], os::getcwd(), true, method);
+      ingest_paths(&req.resources.paths, req.exec_params.args[1..], os::getcwd(), true, method);
     case void => void;
   };
 
@@ -84,9 +101,9 @@ export fn ingest_cli_opts(opts: cli_opts) (cli_request | help) = {
   if (opts.drop_shell) {
     // ignore the original command, and overwrite it with an interactive shell.
     // TODO: respect the user's `$SHELL`.
-    req.exec_bin = "/bin/sh";
-    delete(req.exec_args[..]);
-    append(req.exec_args, "sh");
+    req.exec_params.bin = "/bin/sh";
+    delete(req.exec_params.args[..]);
+    append(req.exec_params.args, "sh");
   };
 
   return req;

pkgs/additional/bunpen/main.ha

@@ -25,6 +25,25 @@ fn do_exec(path: str, args: []str) (os::exec::error | void) = {
   // work if you don't care about that:
 };
 
+fn prepare_env(req: config::cli_request) config::exec_params = {
+  {
+    let argv_str = strings::join(" ", os::args[1..]...);
+    defer free(argv_str);
+    log::printfln("invoked with: {}", argv_str);
+  };
+
+  // set no_new_privs early. this is a flag which prevents us from gaining privs
+  // via SUID/SGID executables, which we never intend to do.
+  errors::ext::check("no_new_privs", rt::ext::no_new_privs());
+  restrict::namespace_restrict(&req.resources);
+  restrict::capability_restrict(&req.resources);
+  // XXX: landlock prevents other sandboxers like `bwrap` from executing,
+  // because it forbids all future `mount` syscalls. so don't landlock.
+  // restrict::landlock_restrict(&req.resources);
+
+  return req.exec_params;
+};
+
 export fn main() void = {
   // install my logger, but defaulted to no logging.
   log::tree::install(tree::global);
@@ -36,29 +55,17 @@ export fn main() void = {
     case let other: config::cli_opts => yield other;
   };
 
-  // configure logging early
-  log::tree::set_level(tree::global, opts.debug);
-
-  {
-    let argv_str = strings::join(" ", os::args[1..]...);
-    defer free(argv_str);
-    log::printfln("invoked with: {}", argv_str);
-  };
-
-  let req = match (config::ingest_cli_opts(opts)) {
+  let exec_params = match (config::ingest_cli_opts(opts)) {
     case config::help =>
       config::usage();
       os::exit(0);
-    case let other: config::cli_request => yield other;
+    case let p: config::exec_params => yield p;  // run without sandboxing (BUNPEN_DISABLE=1)
+    case let req: config::cli_request =>
+      // configure logging early
+      log::tree::set_level(tree::global, opts.debug);
+
+      yield prepare_env(req);
   };
 
-  // set no_new_privs early. this is a flag which prevents us from gaining privs
-  // via SUID/SGID executables, which we never intend to do.
-  errors::ext::check("no_new_privs", rt::ext::no_new_privs());
-  restrict::namespace_restrict(&req.resources);
-  restrict::capability_restrict(&req.resources);
-  // XXX: landlock prevents other sandboxers like `bwrap` from executing,
-  // because it forbids all future `mount` syscalls. so don't landlock.
-  // restrict::landlock_restrict(&req.resources);
-  errors::ext::check("exec <user command>", do_exec(req.exec_bin, req.exec_args));
+  errors::ext::check("exec <user command>", do_exec(exec_params.bin, exec_params.args));
 };