luks

Pure Go library for LUKS volume management

luks.go is a pure-Go library for working with LUKS-encrypted volumes.

This library focuses on the read-only (unlocking) path — it reads LUKS metadata and recovers volume keys without modifying the LUKS header.

Installation

go get github.com/anatol/luks.go

Requires Linux (uses device-mapper via /dev/mapper).

Supported features

• LUKS v1 and LUKS v2
• Detached headers (OpenWithHeader)
• KDFs: pbkdf2, argon2i, argon2id
• Ciphers: AES, Camellia, Twofish (XTS mode)
• Hash algorithms: SHA-1/224/256/384/512, SHA-3, RIPEMD-160, BLAKE2b, BLAKE2s, Whirlpool
• dm-crypt flags: allow-discards, same-cpu-crypt, submit-from-crypt-cpus, no-read-workqueue, no-write-workqueue
• Token metadata (clevis, systemd-fido2, etc.)
• LUKS v2 keyslot priorities
• Multi-segment LUKS2 layouts (e.g. integrity)

Usage

Open and unlock

dev, err := luks.Open("/dev/sda1")
if err != nil {
    log.Fatal(err)
}
defer dev.Close()

// Unlock a specific slot and create a device mapper entry.
// Equivalent to: cryptsetup open /dev/sda1 volumename
if err := dev.Unlock(0, []byte("password"), "volumename"); err == luks.ErrPassphraseDoesNotMatch {
    log.Fatal("wrong password")
} else if err != nil {
    log.Fatal(err)
}
// /dev/mapper/volumename is now available

// Close the mapper when done.
// Equivalent to: cryptsetup close volumename
if err := luks.Lock("volumename"); err != nil {
    log.Fatal(err)
}

Try all keyslots

if err := dev.UnlockAny([]byte("password"), "volumename"); err != nil {
    log.Fatal(err)
}

Detached header

dev, err := luks.OpenWithHeader("/dev/sda1", "/path/to/header.bin")

Flags (dm-crypt options)

// Set flags before unlocking
dev.FlagsAdd(luks.FlagAllowDiscards)
dev.FlagsAdd(luks.FlagNoReadWorkqueue, luks.FlagNoWriteWorkqueue)

// Get current flags
flags := dev.FlagsGet()

// Clear all flags
dev.FlagsClear()

Available flags:

• FlagAllowDiscards — pass discard/TRIM requests through (SSD-friendly, reduces security)
• FlagSameCPUCrypt — perform encryption on the same CPU as the IO
• FlagSubmitFromCryptCPUs — submit IO from crypto CPUs
• FlagNoReadWorkqueue — bypass read workqueue (Linux 5.9+)
• FlagNoWriteWorkqueue — bypass write workqueue (Linux 5.9+)

Two-step unlock (advanced)

UnsealVolume recovers the key without activating the mapper, allowing inspection or custom dm-crypt setup:

volume, err := dev.UnsealVolume(0, []byte("password"))
if err == luks.ErrPassphraseDoesNotMatch {
    log.Fatal("wrong password")
} else if err != nil {
    log.Fatal(err)
}

// volume contains encryption parameters; activate when ready
if err := volume.SetupMapper("volumename"); err != nil {
    log.Fatal(err)
}

Token metadata

Tokens are LUKS v2 metadata entries (or luksmeta entries for LUKS v1) that carry supplementary information for unlocking tools like clevis or systemd-fido2.

tokens, err := dev.Tokens()
for _, t := range tokens {
    fmt.Printf("token %d: type=%s slots=%v\n", t.ID, t.Type, t.Slots)
    // t.Payload contains the raw JSON (LUKS v2) or binary (LUKS v1) token data
}

Device metadata

fmt.Println(dev.Version()) // 1 or 2
fmt.Println(dev.UUID())
fmt.Println(dev.Slots()) // active keyslot IDs, sorted by priority (LUKS v2)
fmt.Println(dev.Path())

How it works

The unlock process follows these steps for both LUKS v1 and v2:

1. Open — read and validate the binary header (magic bytes, version, checksum). For LUKS v2, the JSON metadata area is also parsed.
2. Key derivation — derive an intermediate key from the passphrase using the keyslot's KDF (PBKDF2 for v1; PBKDF2, Argon2i, or Argon2id for v2).
3. Keyslot decryption — decrypt the keyslot area sector-by-sector using XTS-mode encryption with the derived key.
4. Anti-forensic merge — recover the volume master key from 4000 stripes using the AFsplit/AFmerge algorithm (hash-based diffusion + XOR chain).
5. Digest verification — re-derive a digest from the recovered key and compare it against the stored digest to confirm the passphrase is correct.
6. Device mapper setup — pass the recovered key and encryption parameters to the Linux device mapper (dm-crypt) to create the decrypted block device.

References

• LUKS v1 on-disk format (PDF)
• LUKS v2 on-disk format (PDF)
• luksmeta (LUKS v1 token metadata)

License

See LICENSE.