kubernetes/kubernetes · error

size of data is less than the nonce

Error message

size of data is less than the nonce

What it means

Returned by DecryptBytes when len(data) < gcm.NonceSize(). The AES-GCM ciphertext produced by EncryptBytes is structured as nonce||ciphertext; if the input is shorter than the nonce prefix it cannot contain a valid nonce and is rejected before any decryption attempt.

Source

Thrown at cmd/kubeadm/app/util/crypto/crypto.go:67

		return nil, err
	}
	return gcm.Seal(nonce, nonce, data, nil), nil
}

// DecryptBytes takes a byte slice of encrypted data and an encryption key and returns a decrypted byte slice of data.
// The key must be an AES key, either 16, 24, or 32 bytes to select AES-128, AES-192, or AES-256
func DecryptBytes(data, key []byte) ([]byte, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}
	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return nil, err
	}
	nonceSize := gcm.NonceSize()
	if len(data) < nonceSize {
		return nil, errors.New("size of data is less than the nonce")
	}

	nonce, out := data[:nonceSize], data[nonceSize:]
	out, err = gcm.Open(nil, nonce, out, nil)
	if err != nil {
		return nil, err
	}
	return out, nil
}

View on GitHub (pinned to b882c60b40)

Solutions

1. Ensure the data passed is the complete output of EncryptBytes (nonce + ciphertext), unmodified.
2. Verify the source file/blob is not truncated; re-copy or regenerate the encrypted payload.
3. Confirm the AES key length is 16, 24, or 32 bytes matching the encryption key used.
4. If the payload was base64-encoded, decode fully before calling DecryptBytes.

Example fix

// before
plain, err := crypto.DecryptBytes(partialBytes, key) // len < nonceSize

// after
full, err := os.ReadFile(fullEncryptedPath)
if err != nil { return err }
plain, err := crypto.DecryptBytes(full, key)

// AES-GCM nonce is 12 bytes; ciphertext must exceed that.
if len(data) < 12 {
    return nil, fmt.Errorf("ciphertext too short (%d bytes); expected nonce||ciphertext from EncryptBytes", len(data))
}

plain, err := crypto.DecryptBytes(data, key)
if err != nil {
    return fmt.Errorf("decryption failed (verify key length 16/24/32 and payload integrity): %w", err)
}

When it happens

Trigger: Calling crypto.DecryptBytes with truncated, empty, or corrupt ciphertext, or passing data that was not produced by EncryptBytes. Also reached if the wrong AES key size leads to a larger nonce expectation than the data provides.

Common situations: Corrupted/shortened encrypted secret blob (e.g. a copied key/cert fragment). Reading from a truncated file. Passing plaintext or a base64-decoded value that is too short. Mismatched key (16/24/32 bytes) yielding unexpected GCM nonce sizing.

Related errors

• shell not specified
• too many arguments. expected only the shell type
• the --old-config flag is mandatory
• can't use upload-certs with an external CA or an external fr
• cannot use --certificate-key without --print-join-command

AI-assisted analysis of kubernetes/kubernetes@b882c60b40 (2026-08-07). Data as JSON: /api/errors/622d8f9224d8c96e. Report an issue: GitHub.