Add backup encryption function

Cargo.toml

@@ -24,8 +24,8 @@ qrcode = ["matrix-sdk-crypto/qrcode"]
 tracing = ["dep:tracing-subscriber"]
 
 [dependencies]
-matrix-sdk-common = { git = "https://github.com/matrix-org/matrix-rust-sdk", rev = "931c5649420adb071caf1abafc7964758487e472", features = ["js"] }
-matrix-sdk-sqlite = { git = "https://github.com/matrix-org/matrix-rust-sdk", rev = "931c5649420adb071caf1abafc7964758487e472", features = ["crypto-store"] }
+matrix-sdk-common = { git = "https://github.com/matrix-org/matrix-rust-sdk", rev = "48220571630521fbc58529df36a0f2d4772ef5e1", features = ["js"] }
+matrix-sdk-sqlite = { git = "https://github.com/matrix-org/matrix-rust-sdk", rev = "48220571630521fbc58529df36a0f2d4772ef5e1", features = ["crypto-store"] }
 napi = { version = "2.9.1", default-features = false, features = ["napi6", "tokio_rt"] }
 napi-derive = "2.9.1"
 # Fix error[E0635]: unknown feature `stdsimd` caused by ahash < 0.8.7
@@ -37,7 +37,7 @@ zeroize = "1.3.0"
 
 [dependencies.matrix-sdk-crypto]
 git = "https://github.com/matrix-org/matrix-rust-sdk"
-rev = "931c5649420adb071caf1abafc7964758487e472"
+rev = "48220571630521fbc58529df36a0f2d4772ef5e1"
 default-features = false
 features = ["js", "automatic-room-key-forwarding"]
 

src/backup.rs

@@ -1,6 +1,8 @@
 //! Megolm backup types
 
-use matrix_sdk_crypto::{backups::MegolmV1BackupKey as InnerMegolmV1BackupKey, store};
+use matrix_sdk_crypto::{
+    backups::MegolmV1BackupKey as InnerMegolmV1BackupKey, olm::InboundGroupSession, store,
+};
 use napi_derive::*;
 
 use crate::into_err;
@@ -19,6 +21,29 @@ pub struct MegolmV1BackupKey {
     inner: InnerMegolmV1BackupKey,
 }
 
+#[napi(object)]
+#[derive(Debug, Clone)]
+pub struct SessionData {
+    /// Unpadded base64-encoded public half of the ephemeral key.
+    pub ephemeral: String,
+
+    /// Ciphertext, encrypted using AES-CBC-256 with PKCS#7 padding, encoded in
+    /// base64.
+    pub ciphertext: String,
+
+    /// First 8 bytes of MAC key, encoded in base64.
+    pub mac: String,
+}
+
+#[napi]
+#[derive(Debug, Clone)]
+pub struct KeyBackupData {
+    pub first_message_index: i64,
+    pub forwarded_count: i64,
+    pub is_verified: bool,
+    pub session_data: SessionData,
+}
+
 #[napi]
 impl MegolmV1BackupKey {
     /// The actual base64 encoded public key.
@@ -32,6 +57,35 @@ impl MegolmV1BackupKey {
     pub fn backup_algorithm(&self) -> String {
         self.inner.backup_algorithm().into()
     }
+
+    /// Try to create a [`MegolmV1BackupKey`] from a base 64 encoded string.
+    #[napi(strict)]
+    pub fn from_base64(key: String) -> napi::Result<MegolmV1BackupKey> {
+        Ok(Self { inner: InnerMegolmV1BackupKey::from_base64(&key).map_err(into_err)? })
+    }
+
+    /// Encrypt an exported room session which can then be uploaded to the
+    /// homeserver's key backup. Consumes a single session exported from
+    /// `OlmMachine.export_room_keys_for_session`
+    #[napi(strict)]
+    pub async fn encrypt_exported_session(
+        &self,
+        exported_session_json: String,
+    ) -> napi::Result<KeyBackupData> {
+        let exported_session = serde_json::from_str(&exported_session_json).map_err(into_err)?;
+        let session = InboundGroupSession::from_export(&exported_session).map_err(into_err)?;
+        let res = self.inner.encrypt(session).await;
+        Ok(KeyBackupData {
+            first_message_index: res.first_message_index.into(),
+            forwarded_count: res.forwarded_count.into(),
+            is_verified: res.is_verified,
+            session_data: SessionData {
+                ephemeral: res.session_data.ephemeral.to_string(),
+                ciphertext: res.session_data.ciphertext.to_string(),
+                mac: res.session_data.mac.to_string(),
+            },
+        })
+    }
 }
 
 #[napi]