chore: import upstream snapshot with attribution

api/filesystem/filesystem_linux_test.go

@@ -0,0 +1,71 @@
+package filesystem
+
+import "testing"
+
+func TestJoinPaths(t *testing.T) {
+	t.Parallel()
+	var ts = []struct {
+		trusted   string
+		untrusted string
+		expected  string
+	}{
+		{"", "", "."},
+		{"", ".", "."},
+		{"", "d/e/f", "d/e/f"},
+		{"", "./d/e/f", "d/e/f"},
+		{"", "../d/e/f", "d/e/f"},
+		{"", "/d/e/f", "d/e/f"},
+		{"", "../../../etc/shadow", "etc/shadow"},
+
+		{".", "", "."},
+		{".", ".", "."},
+		{".", "d/e/f", "d/e/f"},
+		{".", "./d/e/f", "d/e/f"},
+		{".", "../d/e/f", "d/e/f"},
+		{".", "/d/e/f", "d/e/f"},
+		{".", "../../../etc/shadow", "etc/shadow"},
+
+		{"./", "", "."},
+		{"./", ".", "."},
+		{"./", "d/e/f", "d/e/f"},
+		{"./", "./d/e/f", "d/e/f"},
+		{"./", "../d/e/f", "d/e/f"},
+		{"./", "/d/e/f", "d/e/f"},
+		{"./", "../../../etc/shadow", "etc/shadow"},
+
+		{"a/b/c", "", "a/b/c"},
+		{"a/b/c", ".", "a/b/c"},
+		{"a/b/c", "d/e/f", "a/b/c/d/e/f"},
+		{"a/b/c", "./d/e/f", "a/b/c/d/e/f"},
+		{"a/b/c", "../d/e/f", "a/b/c/d/e/f"},
+		{"a/b/c", "../../../etc/shadow", "a/b/c/etc/shadow"},
+
+		{"/a/b/c", "", "/a/b/c"},
+		{"/a/b/c", ".", "/a/b/c"},
+		{"/a/b/c", "d/e/f", "/a/b/c/d/e/f"},
+		{"/a/b/c", "./d/e/f", "/a/b/c/d/e/f"},
+		{"/a/b/c", "../d/e/f", "/a/b/c/d/e/f"},
+		{"/a/b/c", "../../../etc/shadow", "/a/b/c/etc/shadow"},
+
+		{"./a/b/c", "", "a/b/c"},
+		{"./a/b/c", ".", "a/b/c"},
+		{"./a/b/c", "d/e/f", "a/b/c/d/e/f"},
+		{"./a/b/c", "./d/e/f", "a/b/c/d/e/f"},
+		{"./a/b/c", "../d/e/f", "a/b/c/d/e/f"},
+		{"./a/b/c", "../../../etc/shadow", "a/b/c/etc/shadow"},
+
+		{"../a/b/c", "", "../a/b/c"},
+		{"../a/b/c", ".", "../a/b/c"},
+		{"../a/b/c", "d/e/f", "../a/b/c/d/e/f"},
+		{"../a/b/c", "./d/e/f", "../a/b/c/d/e/f"},
+		{"../a/b/c", "../d/e/f", "../a/b/c/d/e/f"},
+		{"../a/b/c", "../../../etc/shadow", "../a/b/c/etc/shadow"},
+	}
+
+	for _, c := range ts {
+		r := JoinPaths(c.trusted, c.untrusted)
+		if r != c.expected {
+			t.Fatalf("expected '%s', got '%s'. Inputs = '%s', '%s'", c.expected, r, c.trusted, c.untrusted)
+		}
+	}
+}