Factor out serialization functions to a new struct

crates/matrix-sdk-indexeddb/src/crypto_store/indexeddb_serializer.rs

@@ -0,0 +1,164 @@
+// Copyright 2023 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use std::sync::Arc;
+
+use gloo_utils::format::JsValueSerdeExt;
+use matrix_sdk_crypto::CryptoStoreError;
+use matrix_sdk_store_encryption::StoreCipher;
+use serde::{de::DeserializeOwned, Serialize};
+use wasm_bindgen::JsValue;
+use web_sys::IdbKeyRange;
+
+use crate::{safe_encode::SafeEncode, IndexeddbCryptoStoreError};
+
+type Result<A, E = IndexeddbCryptoStoreError> = std::result::Result<A, E>;
+
+/// Handles the functionality of serializing and encrypting data for the
+/// indexeddb store.
+pub struct IndexeddbSerializer {
+    store_cipher: Option<Arc<StoreCipher>>,
+}
+
+impl IndexeddbSerializer {
+    pub fn new(store_cipher: Option<Arc<StoreCipher>>) -> Self {
+        Self { store_cipher }
+    }
+
+    /// Hash the given key securely for the given tablename, using the store
+    /// cipher.
+    ///
+    /// First calls [`SafeEncode::as_encoded_string`]
+    /// on the `key` to encode it into a formatted string.
+    ///
+    /// Then, if a cipher is configured, hashes the formatted key and returns
+    /// the hash encoded as unpadded base64.
+    ///
+    /// If no cipher is configured, just returns the formatted key.
+    ///
+    /// This is faster than [`serialize_value`] and reliably gives the same
+    /// output for the same input, making it suitable for index keys.
+    pub fn encode_key<T>(&self, table_name: &str, key: T) -> JsValue
+    where
+        T: SafeEncode,
+    {
+        self.encode_key_as_string(table_name, key).into()
+    }
+
+    /// Hash the given key securely for the given tablename, using the store
+    /// cipher.
+    ///
+    /// The same as [`encode_key`], but stops short of converting the resulting
+    /// base64 string into a JsValue
+    pub fn encode_key_as_string<T>(&self, table_name: &str, key: T) -> String
+    where
+        T: SafeEncode,
+    {
+        match &self.store_cipher {
+            Some(cipher) => key.as_secure_string(table_name, cipher),
+            None => key.as_encoded_string(),
+        }
+    }
+
+    pub fn encode_to_range<T>(
+        &self,
+        table_name: &str,
+        key: T,
+    ) -> Result<IdbKeyRange, IndexeddbCryptoStoreError>
+    where
+        T: SafeEncode,
+    {
+        match &self.store_cipher {
+            Some(cipher) => key.encode_to_range_secure(table_name, cipher),
+            None => key.encode_to_range(),
+        }
+        .map_err(|e| IndexeddbCryptoStoreError::DomException {
+            code: 0,
+            name: "IdbKeyRangeMakeError".to_owned(),
+            message: e,
+        })
+    }
+
+    /// Encode the value for storage as a value in indexeddb.
+    ///
+    /// First, serialise the given value as JSON.
+    ///
+    /// Then, if a store cipher is enabled, encrypt the JSON string using the
+    /// configured store cipher, giving a byte array. Then, wrap the byte
+    /// array as a `JsValue`.
+    ///
+    /// If no cipher is enabled, deserialises the JSON string again giving a JS
+    /// object.
+    pub fn serialize_value(&self, value: &impl Serialize) -> Result<JsValue, CryptoStoreError> {
+        if let Some(cipher) = &self.store_cipher {
+            let value = cipher.encrypt_value(value).map_err(CryptoStoreError::backend)?;
+
+            // Turn the Vec<u8> into a Javascript-side `Array<number>`.
+            // XXX Isn't there a way to do this that *doesn't* involve going via a JSON
+            // string?
+            Ok(JsValue::from_serde(&value)?)
+        } else {
+            // Turn the rust-side struct into a JS-side `Object`.
+            Ok(JsValue::from_serde(&value)?)
+        }
+    }
+
+    /// Encode the value for storage as a value in indexeddb.
+    ///
+    /// This is the same algorithm as [`serialize_value`], but stops short of
+    /// encoding the resultant byte vector in a JsValue.
+    ///
+    /// Returns a byte vector which is either the JSON serialisation of the
+    /// value, or an encrypted version thereof.
+    pub fn serialize_value_as_bytes(
+        &self,
+        value: &impl Serialize,
+    ) -> Result<Vec<u8>, CryptoStoreError> {
+        match &self.store_cipher {
+            Some(cipher) => cipher.encrypt_value(value).map_err(CryptoStoreError::backend),
+            None => serde_json::to_vec(value).map_err(CryptoStoreError::backend),
+        }
+    }
+
+    /// Decode a value that was previously encoded with [`serialize_value`]
+    pub fn deserialize_value<T: DeserializeOwned>(
+        &self,
+        value: JsValue,
+    ) -> Result<T, CryptoStoreError> {
+        if let Some(cipher) = &self.store_cipher {
+            // `value` is a JS-side array containing the byte values. Turn it into a
+            // rust-side Vec<u8>.
+            // XXX: Isn't there a way to do this that *doesn't* involve going via a JSON
+            // string?
+            let value: Vec<u8> = value.into_serde()?;
+
+            cipher.decrypt_value(&value).map_err(CryptoStoreError::backend)
+        } else {
+            Ok(value.into_serde()?)
+        }
+    }
+
+    /// Decode a value that was previously encoded with
+    /// [`serialize_value_as_bytes`]
+    pub fn deserialize_value_from_bytes<T: DeserializeOwned>(
+        &self,
+        value: &[u8],
+    ) -> Result<T, CryptoStoreError> {
+        if let Some(cipher) = &self.store_cipher {
+            cipher.decrypt_value(value).map_err(CryptoStoreError::backend)
+        } else {
+            serde_json::from_slice(value).map_err(CryptoStoreError::backend)
+        }
+    }
+}