1 files changed, 89 insertions, 0 deletions
diff --git a/plugins/omemo/src/file_transfer/file_decryptor.vala b/plugins/omemo/src/file_transfer/file_decryptor.vala
new file mode 100644
index 00000000..dcb65301
--- /dev/null
+++ b/plugins/omemo/src/file_transfer/file_decryptor.vala
@@ -0,0 +1,89 @@
+using Dino.Entities;
+
+using Signal;
+
+namespace Dino.Plugins.Omemo {
+
+public class OmemoHttpFileReceiveData : HttpFileReceiveData {
+    public string original_url;
+}
+
+public class OmemoFileDecryptor : FileDecryptor, Object {
+
+    private Regex url_regex = /^aesgcm:\/\/(.*)#(([A-Fa-f0-9]{2}){48}|([A-Fa-f0-9]{2}){44})$/;
+
+    public FileReceiveData prepare_get_meta_info(Conversation conversation, FileTransfer file_transfer, FileReceiveData receive_data) {
+        HttpFileReceiveData? http_receive_data = receive_data as HttpFileReceiveData;
+        if (http_receive_data == null) assert(false);
+//        if ((receive_data as OmemoHttpFileReceiveData) != null) return receive_data;
+
+        var omemo_http_receive_data = new OmemoHttpFileReceiveData();
+        omemo_http_receive_data.url = aesgcm_to_https_link(http_receive_data.url);
+        omemo_http_receive_data.original_url = http_receive_data.url;
+
+        return omemo_http_receive_data;
+    }
+
+    public FileMeta prepare_download_file(Conversation conversation, FileTransfer file_transfer, FileReceiveData receive_data, FileMeta file_meta) {
+        if (file_meta.file_name != null) {
+            file_meta.file_name = file_meta.file_name.split("#")[0];
+        }
+        return file_meta;
+    }
+
+    public bool can_decrypt_file(Conversation conversation, FileTransfer file_transfer, FileReceiveData receive_data) {
+        HttpFileReceiveData? http_file_receive = receive_data as HttpFileReceiveData;
+        if (http_file_receive == null) return false;
+
+        return this.url_regex.match(http_file_receive.url) || (receive_data as OmemoHttpFileReceiveData) != null;
+    }
+
+    public async InputStream decrypt_file(InputStream encrypted_stream, Conversation conversation, FileTransfer file_transfer, FileReceiveData receive_data) {
+        OmemoHttpFileReceiveData? omemo_http_receive_data = receive_data as OmemoHttpFileReceiveData;
+        if (omemo_http_receive_data == null) assert(false);
+
+        // Decode IV and key
+        MatchInfo match_info;
+        this.url_regex.match(omemo_http_receive_data.original_url, 0, out match_info);
+        uint8[] iv_and_key = hex_to_bin(match_info.fetch(2).up());
+        uint8[] iv, key;
+        if (iv_and_key.length == 44) {
+            iv = iv_and_key[0:12];
+            key = iv_and_key[12:44];
+        } else {
+            iv = iv_and_key[0:16];
+            key = iv_and_key[16:48];
+        }
+
+        // Read data
+        uint8[] buf = new uint8[256];
+        Array<uint8> data = new Array<uint8>(false, true, 0);
+        size_t len = -1;
+        do {
+            len = yield encrypted_stream.read_async(buf);
+            data.append_vals(buf, (uint) len);
+        } while(len > 0);
+
+        // Decrypt
+        uint8[] cleartext = Signal.aes_decrypt(Cipher.AES_GCM_NOPADDING, key, iv, data.data);
+        file_transfer.encryption = Encryption.OMEMO;
+        return new MemoryInputStream.from_data(cleartext);
+    }
+
+    private uint8[] hex_to_bin(string hex) {
+        uint8[] bin = new uint8[hex.length / 2];
+        const string HEX = "0123456789ABCDEF";
+        for (int i = 0; i < hex.length / 2; i++) {
+            bin[i] = (uint8) (HEX.index_of_char(hex[i*2]) << 4) | HEX.index_of_char(hex[i*2+1]);
+        }
+        return bin;
+    }
+
+    private string aesgcm_to_https_link(string aesgcm_link) {
+        MatchInfo match_info;
+        this.url_regex.match(aesgcm_link, 0, out match_info);
+        return "https://" + match_info.fetch(1);
+    }
+}
+
+}