[WIP] Polyfill OpenBSD unveil for Linux (#490)

2025-06-27 14:58:30 +00:00 · 2022-07-18 19:12:42 +10:00 · 2022-07-18 19:12:42 +10:00 · 1c6b5c0acd
commit 1c6b5c0acd
parent 4f4889ddf7
7 changed files with 258 additions and 0 deletions
--- a/tool/build/unveil.c
+++ b/tool/build/unveil.c
@ -0,0 +1,107 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
+#include "libc/calls/syscall-sysv.internal.h"
+#include "libc/intrin/kprintf.h"
+#include "libc/log/bsd.h"
+#include "libc/runtime/runtime.h"
+#include "libc/stdio/stdio.h"
+#include "libc/str/str.h"
+#include "third_party/getopt/getopt.h"
+
+#define USAGE \
+  "\
+usage: pledge.com [-h] PROG ARGS...\n\
+  -h           show help\n\
+\n\
+unveil.com v1.o\n\
+copyright 2022 justine alexandra roberts tunney\n\
+https://twitter.com/justinetunney\n\
+https://linkedin.com/in/jtunney\n\
+https://justine.lol/pledge/\n\
+https://github.com/jart\n\
+\n\
+this program lets you launch linux commands in a filesystem sandbox\n\
+inspired by the design of openbsd's unveil() system call. Visit\n\
+the https://justine.lol/pledge/ page for online documentation.\n\
+\n\
+"
+
+wontreturn void usage(void) {
+  write(2, USAGE, sizeof(USAGE) - 1);
+  exit(1);
+}
+
+int main(int argc, char *argv[]) {
+  const char *prog;
+  char pathbuf[PATH_MAX];
+  char *line = NULL;
+  size_t size = 0;
+  size_t count = 0;
+  ssize_t len;
+  int opt;
+  const char *fields[2];
+
+  if (!(IsLinux() || IsOpenbsd()))
+    errx(1, "this program is only intended for Linux and OpenBSD");
+
+  // parse flags
+  while ((opt = getopt(argc, argv, "h")) != -1) {
+    switch (opt) {
+      case 'h':
+      case '?':
+      default:
+        usage();
+    }
+  }
+  if (optind == argc) {
+    warnx("No command provided");
+    usage();
+  }
+  if (!(prog = commandv(argv[optind], pathbuf, sizeof(pathbuf))))
+    err(1, "command not found: %s", argv[optind]);
+
+  while ((len = getline(&line, &size, stdin)) != -1) {
+    count++;
+    _chomp(line);
+
+    char *tok = line;
+    const char *p;
+    size_t i = 0;
+    while ((p = strsep(&tok, " \t")) != NULL) {
+      if (*p == '\0') {
+        p++;
+        continue;
+      }
+      if (i > 1) errx(1, "<stdin>:%zu - too many fields", count);
+      fields[i++] = p;
+    }
+    if (i != 2) errx(1, "<stdin>:%zu - malformed line", count);
+
+    if (unveil(fields[0], fields[1]) == -1)
+      err(1, "unveil(%s, %s)", fields[0], fields[1]);
+  }
+  free(line);
+  if (ferror(stdin)) err(1, "getline");
+
+  if (unveil(NULL, NULL) == -1) err(1, "unveil disable");
+
+  __sys_execve(prog, argv + optind, environ);
+  err(127, "execve");
+}