patrick
9a24ea29e1
Git-Repository für bestehenden archivdms-Code initialisiert, Branch-/Commit-Konvention (feature/<ticket>-<slug>-Branches, Ticket-Prefix in Commit-Nachricht) etabliert.
74 lines
2.5 KiB
Go
74 lines
2.5 KiB
Go
// Package cryptutil provides authenticated symmetric encryption (AES-256-GCM)
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// for secrets that must be stored at rest but read back in plaintext at
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// runtime — currently the LDAP service-bind password (internal/ldapstore).
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//
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// The 256-bit key is derived via HKDF-SHA256 from the application's existing
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// master/JWT secret (config.API.Secret), so no additional secret needs to be
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// provisioned. A distinct HKDF info label keeps this key independent from the
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// JWT signing key even though both originate from the same input secret.
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package cryptutil
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import (
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"crypto/aes"
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"crypto/cipher"
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"crypto/rand"
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"crypto/sha256"
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"fmt"
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"io"
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"golang.org/x/crypto/hkdf"
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)
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// hkdfInfo domain-separates the secretbox key from every other key derived
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// from the same master secret (e.g. the JWT signing key uses "archivdms-jwt-v1").
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const hkdfInfo = "archivdms-ldap-secretbox-v1"
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// Box performs AES-256-GCM encrypt/decrypt with a key derived from a secret.
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type Box struct {
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gcm cipher.AEAD
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}
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// NewBox derives a 256-bit AES key from secret via HKDF-SHA256 and returns a
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// ready-to-use Box. secret must be non-empty.
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func NewBox(secret string) (*Box, error) {
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if secret == "" {
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return nil, fmt.Errorf("cryptutil: empty secret")
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}
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key := make([]byte, 32)
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if _, err := io.ReadFull(hkdf.New(sha256.New, []byte(secret), nil, []byte(hkdfInfo)), key); err != nil {
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return nil, fmt.Errorf("cryptutil: derive key: %w", err)
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}
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block, err := aes.NewCipher(key)
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if err != nil {
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return nil, fmt.Errorf("cryptutil: new cipher: %w", err)
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}
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gcm, err := cipher.NewGCM(block)
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if err != nil {
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return nil, fmt.Errorf("cryptutil: new gcm: %w", err)
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}
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return &Box{gcm: gcm}, nil
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}
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// Encrypt seals plaintext, returning the ciphertext and the freshly generated
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// nonce (stored separately in the DB). Callers persist both.
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func (b *Box) Encrypt(plaintext []byte) (ciphertext, nonce []byte, err error) {
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nonce = make([]byte, b.gcm.NonceSize())
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if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
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return nil, nil, fmt.Errorf("cryptutil: nonce: %w", err)
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}
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ciphertext = b.gcm.Seal(nil, nonce, plaintext, nil)
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return ciphertext, nonce, nil
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}
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// Decrypt opens ciphertext using nonce, returning the original plaintext.
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func (b *Box) Decrypt(ciphertext, nonce []byte) ([]byte, error) {
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if len(nonce) != b.gcm.NonceSize() {
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return nil, fmt.Errorf("cryptutil: bad nonce length %d", len(nonce))
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}
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plaintext, err := b.gcm.Open(nil, nonce, ciphertext, nil)
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if err != nil {
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return nil, fmt.Errorf("cryptutil: decrypt: %w", err)
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}
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return plaintext, nil
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}
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