Disallow absolute path at the raw WASI level (#270)

This commit fixes a `path_open` behavior that allows opening absolute
paths. Although the path normalization correctly resolves the path and
enforces the sandbox, it's still a good idea to converge with other
runtimes here.

fixes #269

Signed-off-by: Yage Hu <me@huyage.dev>

src/path_resolver.c

@@ -440,6 +440,11 @@ uvwasi_errno_t uvwasi__resolve_path(const uvwasi_t* uvwasi,
   normalized_parent = NULL;
   resolved_link_target = NULL;
 
+  if (uvwasi__is_absolute_path(input, input_len)) {
+    *resolved_path = NULL;
+    return UVWASI_ENOTCAPABLE;
+  }
+
 start:
   normalized_path = NULL;
   err = UVWASI_ESUCCESS;

test/test-path-open-absolute.c

@@ -0,0 +1,53 @@
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include "uvwasi.h"
+#include "uv.h"
+#include "test-common.h"
+
+#define TEST_TMP_DIR    "./out/tmp"
+#define TEST_FILE       "/test-path-open-absolute.file"
+#define OFLAGS_CREAT    1
+#define RIGHTS_FD_WRITE 64
+
+int main(void) {
+  uvwasi_t uvwasi;
+  uvwasi_fd_t fd;
+  uvwasi_options_t init_options;
+  uvwasi_errno_t err;
+  uv_fs_t req;
+  int r;
+
+  setup_test_environment();
+
+  r = uv_fs_mkdir(NULL, &req, TEST_TMP_DIR, 0777, NULL);
+  uv_fs_req_cleanup(&req);
+  assert(r == 0 || r == UV_EEXIST);
+
+  uvwasi_options_init(&init_options);
+  init_options.preopenc = 1;
+  init_options.preopens = calloc(1, sizeof(uvwasi_preopen_t));
+  init_options.preopens[0].mapped_path = "var";
+  init_options.preopens[0].real_path = TEST_TMP_DIR;
+
+  err = uvwasi_init(&uvwasi, &init_options);
+  assert(err == 0);
+
+  err = uvwasi_path_open(&uvwasi,
+                         3,
+                         0,
+                         TEST_FILE,
+                         strlen(TEST_FILE) + 1,
+                         OFLAGS_CREAT,
+                         RIGHTS_FD_WRITE,
+                         0,
+                         0,
+                         &fd);
+  assert(err == UVWASI_ENOTCAPABLE && "open absolute path should fail");
+
+  uvwasi_destroy(&uvwasi);
+  free(init_options.preopens);
+
+  return 0;
+}

test/test-path-resolution.c

@@ -182,13 +182,13 @@ int main(void) {
 
   /* Arguments: fd mapped path, fd real path, path to resolve, expected path */
   pass("/", "/foo", "test_path", "/foo/test_path");
-  pass("/", "/foo", "/test_path", "/foo/test_path");
+  pass("/", "/foo", "test_path", "/foo/test_path");
   pass("/bar", "/baz", "test_path", "/baz/test_path");
   pass("/bar", "/baz", "./test_path", "/baz/test_path");
   pass("/bar", "/baz", "../bar/test_path", "/baz/test_path");
   pass("/bar", "/baz", "../bar/./test_path/../test_path", "/baz/test_path");
-  pass("/bar", "/baz", "/bar/test_path", "/baz/test_path");
-  pass("/bar", "/baz", "/bar/../bar/test_path", "/baz/test_path");
+  pass("/bar", "/baz", "bar/test_path", "/baz/bar/test_path");
+  pass("/bar", "/baz", "bar/../bar/test_path", "/baz/bar/test_path");
   pass(".", "/foo", "test_path", "/foo/test_path");
   pass("./", "/foo", "test_path", "/foo/test_path");
   pass(".", "/foo", "./test_path", "/foo/test_path");
@@ -222,16 +222,16 @@ int main(void) {
   create_symlink("./qux", TEST_TMP_DIR "/dir/quux");
 
   /* Arguments: fd mapped path, fd real path, path to resolve, expected path */
-  pass_follow("/", TEST_TMP_DIR, "/bar", TEST_TMP_DIR "/foo");
-  pass_follow("/", TEST_TMP_DIR, "/bar2", TEST_TMP_DIR "/foo");
-  pass_follow("/", TEST_TMP_DIR, "/bar3", TEST_TMP_DIR "/foo");
-  pass_follow("/", TEST_TMP_DIR, "/bar4", TEST_TMP_DIR "/foo");
-  pass_follow("/", TEST_TMP_DIR, "/bar5", TEST_TMP_DIR "/foo");
-  pass_follow("/", TEST_TMP_DIR, "/baz", TEST_TMP_DIR "/foo");
-  pass_follow("/", TEST_TMP_DIR, "/baz2", TEST_TMP_DIR "/foo");
-  pass_follow("/", TEST_TMP_DIR, "/baz3", TEST_TMP_DIR "/foo");
-  pass_follow("/", TEST_TMP_DIR, "/dir/qux", TEST_TMP_DIR "/foo");
-  pass_follow("/", TEST_TMP_DIR, "/dir/quux", TEST_TMP_DIR "/foo");
+  pass_follow("/", TEST_TMP_DIR, "bar", TEST_TMP_DIR "/foo");
+  pass_follow("/", TEST_TMP_DIR, "bar2", TEST_TMP_DIR "/foo");
+  pass_follow("/", TEST_TMP_DIR, "bar3", TEST_TMP_DIR "/foo");
+  pass_follow("/", TEST_TMP_DIR, "bar4", TEST_TMP_DIR "/foo");
+  pass_follow("/", TEST_TMP_DIR, "bar5", TEST_TMP_DIR "/foo");
+  pass_follow("/", TEST_TMP_DIR, "baz", TEST_TMP_DIR "/foo");
+  pass_follow("/", TEST_TMP_DIR, "baz2", TEST_TMP_DIR "/foo");
+  pass_follow("/", TEST_TMP_DIR, "baz3", TEST_TMP_DIR "/foo");
+  pass_follow("/", TEST_TMP_DIR, "dir/qux", TEST_TMP_DIR "/foo");
+  pass_follow("/", TEST_TMP_DIR, "dir/quux", TEST_TMP_DIR "/foo");
 
   /* Arguments: fd mapped path, fd real path, path to resolve, expected error */
   fail_follow("/dir", TEST_TMP_DIR "/dir", "/dir/qux", UVWASI_ENOTCAPABLE);