tests: add TestDiskFull

Also fix incomplete uid restoration in TestSupplementaryGroups
and replace syscall.Setregid and friends with unix.Setregid and
friends.

This test is added to check if have problems handling a full disk.
The ticket https://github.com/rfjakob/gocryptfs/issues/550 states
that the full disk was not where the backing gocryptfs filesystem
was, but this has no effect on gocryptfs, so we test the harder
case.

1 files changed, 169 insertions, 9 deletions

diff --git a/tests/root_test/root_test.go b/tests/root_test/root_test.go
index 26caafc..079c03b 100644
--- a/tests/root_test/root_test.go
+++ b/tests/root_test/root_test.go
@@ -1,11 +1,19 @@
+// Package root_test contains tests that need root
+// permissions to run
 package root_test
 
 import (
+	"io/ioutil"
 	"os"
+	"os/exec"
+	"path/filepath"
 	"runtime"
+	"sync"
 	"syscall"
 	"testing"
 
+	"golang.org/x/sys/unix"
+
 	"github.com/rfjakob/gocryptfs/tests/test_helpers"
 )
 
@@ -13,25 +21,57 @@ func asUser(uid int, gid int, supplementaryGroups []int, f func() error) error {
 	runtime.LockOSThread()
 	defer runtime.UnlockOSThread()
 
-	err := syscall.Setgroups(supplementaryGroups)
+	err := unix.Setgroups(supplementaryGroups)
 	if err != nil {
 		return err
 	}
-	defer syscall.Setgroups(nil)
-
-	err = syscall.Setregid(-1, gid)
+	defer func() {
+		err = unix.Setgroups(nil)
+		if err != nil {
+			panic(err)
+		}
+	}()
+	err = unix.Setregid(-1, gid)
 	if err != nil {
 		return err
 	}
-	defer syscall.Setregid(-1, 0)
-
-	err = syscall.Setreuid(-1, uid)
+	defer func() {
+		err = unix.Setregid(-1, 0)
+		if err != nil {
+			panic(err)
+		}
+	}()
+	err = unix.Setreuid(-1, uid)
 	if err != nil {
 		return err
 	}
-	defer syscall.Setreuid(-1, 0)
+	defer func() {
+		err = unix.Setreuid(-1, 0)
+		if err != nil {
+			panic(err)
+		}
+	}()
+
+	ret := f()
 
-	return f()
+	// Also reset the saved user id (suid) and saved group id (sgid) to prevent
+	// bizarre failures in later tests.
+	//
+	// Yes, the kernel checks that *all of them* match:
+	// https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/fuse/dir.c?h=v5.12-rc2#n1193
+	//
+	// How to check:
+	// ps -o tid,pid,euid,ruid,suid,egid,rgid,sgid,cmd -eL
+	err = unix.Setresuid(0, 0, 0)
+	if err != nil {
+		panic(err)
+	}
+	err = unix.Setresgid(0, 0, 0)
+	if err != nil {
+		panic(err)
+	}
+
+	return ret
 }
 
 func TestSupplementaryGroups(t *testing.T) {
@@ -73,3 +113,123 @@ func TestSupplementaryGroups(t *testing.T) {
 		t.Error(err)
 	}
 }
+
+func writeTillFull(t *testing.T, path string) (int, syscall.Errno) {
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	fd, err := syscall.Creat(path, 0600)
+	if err != nil {
+		return 0, err.(syscall.Errno)
+	}
+	defer syscall.Close(fd)
+	// Write in 100.000 byte-blocks, which is not aligend to the
+	// underlying block size
+	buf := make([]byte, 100000)
+	var sz int
+	for {
+		n, err := syscall.Write(fd, buf)
+		if err != nil {
+			return sz, err.(syscall.Errno)
+		}
+		sz += n
+	}
+	return sz, 0
+}
+
+func TestDiskFull(t *testing.T) {
+	if os.Getuid() != 0 {
+		t.Skip("must run as root")
+	}
+
+	// Create 10 MB file full of zeros
+	ext4img := filepath.Join(test_helpers.TmpDir, t.Name()+".ext4")
+	f, err := os.Create(ext4img)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	err = f.Truncate(10 * 1024 * 1024)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Format as ext4
+	cmd := exec.Command("mkfs.ext4", ext4img)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Log(string(out))
+		t.Fatal(err)
+	}
+
+	// Mount ext4
+	ext4mnt := ext4img + ".mnt"
+	err = os.Mkdir(ext4mnt, 0600)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cmd = exec.Command("mount", ext4img, ext4mnt)
+	out, err = cmd.CombinedOutput()
+	if err != nil {
+		t.Log(string(out))
+		t.Fatal(err)
+	}
+	defer syscall.Unlink(ext4img)
+	defer syscall.Unmount(ext4mnt, 0)
+
+	// gocryptfs -init
+	cipherdir := ext4mnt + "/a"
+	if err = os.Mkdir(cipherdir, 0600); err != nil {
+		t.Fatal(err)
+	}
+	cmd = exec.Command(test_helpers.GocryptfsBinary, "-q", "-init", "-extpass", "echo test", "-scryptn=10", cipherdir)
+	out, err = cmd.CombinedOutput()
+	if err != nil {
+		t.Log(string(out))
+		t.Fatal(err)
+	}
+
+	// Mount gocryptfs
+	mnt := ext4mnt + "/b"
+	err = os.Mkdir(mnt, 0600)
+	if err != nil {
+		t.Fatal(err)
+	}
+	test_helpers.MountOrFatal(t, cipherdir, mnt, "-extpass", "echo test")
+	defer test_helpers.UnmountPanic(mnt)
+
+	// Write till we get ENOSPC
+	var err1, err2 error
+	var sz1, sz2 int
+	var wg sync.WaitGroup
+	wg.Add(2)
+	go func() {
+		sz1, err1 = writeTillFull(t, mnt+"/foo1")
+		wg.Done()
+	}()
+	go func() {
+		sz2, err2 = writeTillFull(t, mnt+"/foo2")
+		wg.Done()
+	}()
+	wg.Wait()
+	if err1 != syscall.ENOSPC || err2 != syscall.ENOSPC {
+		t.Fatalf("err1=%v, err2=%v", err1, err2)
+	}
+	t.Logf("sz1=%d, sz2=%d", sz1, sz2)
+
+	foo1, err := ioutil.ReadFile(mnt + "/foo1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(foo1) != sz1 {
+		t.Fail()
+	}
+
+	foo2, err := ioutil.ReadFile(mnt + "/foo2")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(foo2) != sz2 {
+		t.Fail()
+	}
+}