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darwin: impl MountSecretFs

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This commit is contained in:
Pogobanane 2022-07-10 21:54:32 +02:00
parent 58ceff1f7b
commit 98834d958b
1 changed files with 46 additions and 8 deletions
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54
pkgs/sops-install-secrets/darwin.go
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@ -4,8 +4,12 @@
package main
import (
"errors"
"fmt"
"log"
"os"
"os/exec"
"strings"
"golang.org/x/sys/unix"
)
@ -33,30 +37,64 @@ func SecureSymlinkChown(symlinkToCheck string, expectedTarget string, owner, gro
return nil
}
// Does:
// mkdir /tmp/mymount
// NUMSECTORS=128000 # a sector is 512 bytes
// mydev=`hdiutil attach -nomount ram://$NUMSECTORS`
// newfs_hfs $mydev
// mkdir /tmp/mymount
// mount -t hfs $mydev /tmp/mymount
func MountSecretFs(mountpoint string, keysGid int, userMode bool) error {
//if err := os.MkdirAll(mountpoint, 0751); err != nil {
// return fmt.Errorf("Cannot create directory '%s': %w", mountpoint, err)
//}
if err := os.MkdirAll(mountpoint, 0751); err != nil {
return fmt.Errorf("Cannot create directory '%s': %w", mountpoint, err)
}
if _, err := os.Stat(mountpoint + "/sops-nix-secretfs"); !errors.Is(err, os.ErrNotExist) {
return nil // secret fs already exists
}
// MacOS/darwin options for temporary files:
// - /tmp or NSTemporaryDirectory is persistent, and regularly wiped from files not touched >3d
// https://wiki.lazarus.freepascal.org/Locating_the_macOS_tmp_directory
// - there is no ramfs, also `man statfs` doesn't have flags for memfs things
// - we can allocate and mount statically allocated memory (ram://), however most
// functions for that are not publicly exposed to userspace.
mb := 64 // size in MB
size := mb * 1024 * 1024 / 512 // size in sectors a 512 bytes
cmd := exec.Command("hdiutil", "attach", "-nomount", fmt.Sprintf("ram://%d", int(size)))
out, err := cmd.Output() // /dev/diskN
log.Printf("%q\n", string(out))
diskpath := strings.TrimRight(string(out[:]), " \t\n")
log.Printf("%q\n", diskpath)
log.Printf("hdiutil attach ret %v. out: %s", err, diskpath)
// format as hfs
out, err = exec.Command("newfs_hfs", diskpath).Output()
log.Printf("newfs_hfs ret %v. out: %s", err, out)
// "posix" mount takes `struct hfs_mount_args` which we dont have bindings for at hand.
// See https://stackoverflow.com/a/49048846/4108673
// err = unix.Mount("hfs", mountpoint, unix.MNT_NOEXEC|unix.MNT_NODEV, mount_args)
// Instead we call:
out, err = exec.Command("mount", "-t", "hfs", diskpath, mountpoint).Output()
log.Printf("mount ret %v. out: %s", err, out)
// There is no documented way to check for memfs mountpoint. Thus we place a file.
_, err = os.Create(mountpoint + "/sops-nix-secretfs")
// This would be the way to check on unix.
//buf := unix.Statfs_t{}
//if err := unix.Statfs(mountpoint, &buf); err != nil {
// return fmt.Errorf("Cannot get statfs for directory '%s': %w", mountpoint, err)
//}
//
//if int32(buf.Type) != RAMFS_MAGIC {
// if err := unix.Mount("none", mountpoint, "ramfs", unix.MS_NODEV|unix.MS_NOSUID, "mode=0751"); err != nil {
// return fmt.Errorf("Cannot mount: %s", err)
// }
//}
//if err := os.Chown(mountpoint, 0, int(keysGid)); err != nil {
// return fmt.Errorf("Cannot change owner/group of '%s' to 0/%d: %w", mountpoint, keysGid, err)
//}
if err := os.Chown(mountpoint, 0, int(keysGid)); err != nil {
return fmt.Errorf("Cannot change owner/group of '%s' to 0/%d: %w", mountpoint, keysGid, err)
}
return nil
}