1 files changed, 90 insertions, 0 deletions
diff --git a/main/src/plugins/omemo/file_transfer/file_decryptor.vala b/main/src/plugins/omemo/file_transfer/file_decryptor.vala
new file mode 100644
index 00000000..8ae0b96b
--- /dev/null
+++ b/main/src/plugins/omemo/file_transfer/file_decryptor.vala
@@ -0,0 +1,90 @@
+using Dino.Entities;
+
+using Dino.Crypto;
+using Omemo;
+
+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 Encryption get_encryption() {
+        return Encryption.OMEMO;
+    }
+
+    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) throws FileReceiveError {
+        const uint KEY_SIZE = 32;
+        try {
+            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 = iv_and_key[0:iv_and_key.length-KEY_SIZE];
+            uint8[] key = iv_and_key[iv_and_key.length-KEY_SIZE:iv_and_key.length];
+
+            file_transfer.encryption = Encryption.OMEMO;
+            debug("Decrypting file %s from %s", file_transfer.file_name, file_transfer.server_file_name);
+
+            SymmetricCipherDecryption cipher = create_symmetric_cipher_decryption("AES-GCM");
+            cipher.set_key(key);
+            cipher.set_iv(iv);
+            return new ConverterInputStream(encrypted_stream, new SymmetricCipherDecrypter((owned) cipher, 16));
+
+        } catch (Crypto.Error e) {
+            throw new FileReceiveError.DECRYPTION_FAILED("OMEMO file decryption error: %s".printf(e.message));
+        } catch (GLib.Error e) {
+            throw new FileReceiveError.DECRYPTION_FAILED("OMEMO file decryption error: %s".printf(e.message));
+        }
+    }
+
+    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);
+    }
+}
+
+}