diff --git a/.deadcode-out b/.deadcode-out
index 72d5df86dc..539056a429 100644
--- a/.deadcode-out
+++ b/.deadcode-out
@@ -170,6 +170,11 @@ code.gitea.io/gitea/modules/json
StdJSON.NewDecoder
StdJSON.Indent
+code.gitea.io/gitea/modules/keying
+ DeriveKey
+ Key.Encrypt
+ Key.Decrypt
+
code.gitea.io/gitea/modules/markup
GetRendererByType
RenderString
diff --git a/modules/keying/keying.go b/modules/keying/keying.go
new file mode 100644
index 0000000000..7cf5f28a44
--- /dev/null
+++ b/modules/keying/keying.go
@@ -0,0 +1,111 @@
+// Copyright 2024 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+// Keying is a module that allows for subkeys to be determistically generated
+// from the same master key. It allows for domain seperation to take place by
+// using new keys for new subsystems/domains. These subkeys are provided with
+// an API to encrypt and decrypt data. The module panics if a bad interaction
+// happened, the panic should be seen as an non-recoverable error.
+//
+// HKDF (per RFC 5869) is used to derive new subkeys in a safe manner. It
+// provides a KDF security property, which is required for Forgejo, as the
+// secret key would be an ASCII string and isn't a random uniform bit string.
+// XChaCha-Poly1305 (per draft-irtf-cfrg-xchacha-01) is used as AEAD to encrypt
+// and decrypt messages. A new fresh random nonce is generated for every
+// encryption. The nonce gets prepended to the ciphertext.
+package keying
+
+import (
+ "crypto/rand"
+ "crypto/sha256"
+
+ "golang.org/x/crypto/chacha20poly1305"
+ "golang.org/x/crypto/hkdf"
+)
+
+var (
+ // The hash used for HKDF.
+ hash = sha256.New
+ // The AEAD used for encryption/decryption.
+ aead = chacha20poly1305.NewX
+ aeadKeySize = chacha20poly1305.KeySize
+ aeadNonceSize = chacha20poly1305.NonceSizeX
+ // The pseudorandom key generated by HKDF-Extract.
+ prk []byte
+)
+
+// Set the main IKM for this module.
+func Init(ikm []byte) {
+ // Salt is intentionally left empty, it's not useful to Forgejo's use case.
+ prk = hkdf.Extract(hash, ikm, nil)
+}
+
+// Specifies the context for which a subkey should be derived for.
+// This must be a hardcoded string and must not be arbitrarily constructed.
+type Context string
+
+// Derive *the* key for a given context, this is a determistic function. The
+// same key will be provided for the same context.
+func DeriveKey(context Context) *Key {
+ if len(prk) == 0 {
+ panic("keying: not initialized")
+ }
+
+ r := hkdf.Expand(hash, prk, []byte(context))
+
+ key := make([]byte, aeadKeySize)
+ // This should never return an error, but if it does, panic.
+ if _, err := r.Read(key); err != nil {
+ panic(err)
+ }
+
+ return &Key{key}
+}
+
+type Key struct {
+ key []byte
+}
+
+// Encrypts the specified plaintext with some additional data that is tied to
+// this plaintext. The additional data can be seen as the context in which the
+// data is being encrypted for, this is different than the context for which the
+// key was derrived this allows for more granuality without deriving new keys.
+// Avoid any user-generated data to be passed into the additional data. The most
+// common usage of this would be to encrypt a database field, in that case use
+// the ID and database column name as additional data. The additional data isn't
+// appended to the ciphertext and may be publicly known, it must be available
+// when decryping the ciphertext.
+func (k *Key) Encrypt(plaintext, additionalData []byte) []byte {
+ // Construct a new AEAD with the key.
+ e, err := aead(k.key)
+ if err != nil {
+ panic(err)
+ }
+
+ // Generate a random nonce.
+ nonce := make([]byte, aeadNonceSize)
+ if _, err := rand.Read(nonce); err != nil {
+ panic(err)
+ }
+
+ // Returns the ciphertext of this plaintext.
+ return e.Seal(nonce, nonce, plaintext, additionalData)
+}
+
+// Decrypts the ciphertext and authenticates it against the given additional
+// data that was given when it was encrypted. It returns an error if the
+// authentication failed.
+func (k *Key) Decrypt(ciphertext, additionalData []byte) ([]byte, error) {
+ if len(ciphertext) <= aeadNonceSize {
+ panic("keying: ciphertext is too short")
+ }
+
+ e, err := aead(k.key)
+ if err != nil {
+ panic(err)
+ }
+
+ nonce, ciphertext := ciphertext[:aeadNonceSize], ciphertext[aeadNonceSize:]
+
+ return e.Open(nil, nonce, ciphertext, additionalData)
+}
diff --git a/modules/keying/keying_test.go b/modules/keying/keying_test.go
new file mode 100644
index 0000000000..16a6781af8
--- /dev/null
+++ b/modules/keying/keying_test.go
@@ -0,0 +1,96 @@
+// Copyright 2024 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package keying_test
+
+import (
+ "testing"
+
+ "code.gitea.io/gitea/modules/keying"
+
+ "github.com/stretchr/testify/assert"
+ "github.com/stretchr/testify/require"
+ "golang.org/x/crypto/chacha20poly1305"
+)
+
+func TestKeying(t *testing.T) {
+ t.Run("Not initalized", func(t *testing.T) {
+ assert.Panics(t, func() {
+ keying.DeriveKey(keying.Context("TESTING"))
+ })
+ })
+
+ t.Run("Initialization", func(t *testing.T) {
+ keying.Init([]byte{0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07})
+ })
+
+ t.Run("Context seperation", func(t *testing.T) {
+ key1 := keying.DeriveKey(keying.Context("TESTING"))
+ key2 := keying.DeriveKey(keying.Context("TESTING2"))
+
+ ciphertext := key1.Encrypt([]byte("This is for context TESTING"), nil)
+
+ plaintext, err := key2.Decrypt(ciphertext, nil)
+ require.Error(t, err)
+ assert.Empty(t, plaintext)
+
+ plaintext, err = key1.Decrypt(ciphertext, nil)
+ require.NoError(t, err)
+ assert.EqualValues(t, "This is for context TESTING", plaintext)
+ })
+
+ context := keying.Context("TESTING PURPOSES")
+ plainText := []byte("Forgejo is run by [Redacted]")
+ var cipherText []byte
+ t.Run("Encrypt", func(t *testing.T) {
+ key := keying.DeriveKey(context)
+
+ cipherText = key.Encrypt(plainText, []byte{0x05, 0x06})
+ cipherText2 := key.Encrypt(plainText, []byte{0x05, 0x06})
+
+ // Ensure ciphertexts don't have an determistic output.
+ assert.NotEqualValues(t, cipherText, cipherText2)
+ })
+
+ t.Run("Decrypt", func(t *testing.T) {
+ key := keying.DeriveKey(context)
+
+ t.Run("Succesful", func(t *testing.T) {
+ convertedPlainText, err := key.Decrypt(cipherText, []byte{0x05, 0x06})
+ require.NoError(t, err)
+ assert.EqualValues(t, plainText, convertedPlainText)
+ })
+
+ t.Run("Not enougn additional data", func(t *testing.T) {
+ plainText, err := key.Decrypt(cipherText, []byte{0x05})
+ require.Error(t, err)
+ assert.Empty(t, plainText)
+ })
+
+ t.Run("Too much additional data", func(t *testing.T) {
+ plainText, err := key.Decrypt(cipherText, []byte{0x05, 0x06, 0x07})
+ require.Error(t, err)
+ assert.Empty(t, plainText)
+ })
+
+ t.Run("Incorrect nonce", func(t *testing.T) {
+ // Flip the first byte of the nonce.
+ cipherText[0] = ^cipherText[0]
+
+ plainText, err := key.Decrypt(cipherText, []byte{0x05, 0x06})
+ require.Error(t, err)
+ assert.Empty(t, plainText)
+ })
+
+ t.Run("Incorrect ciphertext", func(t *testing.T) {
+ assert.Panics(t, func() {
+ key.Decrypt(nil, nil)
+ })
+
+ assert.Panics(t, func() {
+ cipherText := make([]byte, chacha20poly1305.NonceSizeX)
+ key.Decrypt(cipherText, nil)
+ })
+ })
+ })
+}
diff --git a/modules/setting/security.go b/modules/setting/security.go
index 3d7b1f9ce7..678a57cb30 100644
--- a/modules/setting/security.go
+++ b/modules/setting/security.go
@@ -10,6 +10,7 @@ import (
"code.gitea.io/gitea/modules/auth/password/hash"
"code.gitea.io/gitea/modules/generate"
+ "code.gitea.io/gitea/modules/keying"
"code.gitea.io/gitea/modules/log"
)
@@ -110,6 +111,7 @@ func loadSecurityFrom(rootCfg ConfigProvider) {
// Until it supports rotating an existing secret key, we shouldn't move users off of the widely used default value
SecretKey = "!#@FDEWREWR&*(" //nolint:gosec
}
+ keying.Init([]byte(SecretKey))
CookieRememberName = sec.Key("COOKIE_REMEMBER_NAME").MustString("gitea_incredible")