Send OMEMO-encrypted messages and files using 12 byte IV

plugins/omemo/src/file_transfer/file_decryptor.vala

@@ -52,14 +52,8 @@ public class OmemoFileDecryptor : FileDecryptor, Object {
             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;
+            uint8[] iv = iv_and_key[0:iv_and_key.length-16];
-            if (iv_and_key.length == 44) {
+            uint8[] key = iv_and_key[iv_and_key.length-16:iv_and_key.length];
-                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];
-            }
 
             file_transfer.encryption = Encryption.OMEMO;
             debug("Decrypting file %s from %s", file_transfer.file_name, file_transfer.server_file_name);

plugins/omemo/src/file_transfer/file_encryptor.vala

@@ -20,13 +20,15 @@ public class OmemoFileEncryptor : Dino.FileEncryptor, Object {
     }
 
     public FileMeta encrypt_file(Conversation conversation, FileTransfer file_transfer) throws FileSendError {
+        const uint KEY_SIZE = 32;
+        const uint IV_SIZE = 12;
         var omemo_http_file_meta = new OmemoHttpFileMeta();
 
         try {
             //Create a key and use it to encrypt the file
-            uint8[] iv = new uint8[16];
+            uint8[] iv = new uint8[IV_SIZE];
             Plugin.get_context().randomize(iv);
-            uint8[] key = new uint8[32];
+            uint8[] key = new uint8[KEY_SIZE];
             Plugin.get_context().randomize(key);
 
             SymmetricCipher cipher = new SymmetricCipher("AES-GCM");

plugins/omemo/src/jingle/jet_omemo.vala

@@ -12,6 +12,8 @@ private const string AES_128_GCM_URI = "urn:xmpp:ciphers:aes-128-gcm-nopadding";
 public class Module : XmppStreamModule, Jet.EnvelopEncoding {
     public static Xmpp.ModuleIdentity<Module> IDENTITY = new Xmpp.ModuleIdentity<Module>(NS_URI, "0396_jet_omemo");
     private Omemo.Plugin plugin;
+    const uint KEY_SIZE = 16;
+    const uint IV_SIZE = 12;
 
     public Module(Omemo.Plugin plugin) {
         this.plugin = plugin;
@@ -21,7 +23,7 @@ public class Module : XmppStreamModule, Jet.EnvelopEncoding {
         if (stream.get_module(Jet.Module.IDENTITY) != null) {
             stream.get_module(ServiceDiscovery.Module.IDENTITY).add_feature(stream, NS_URI);
             stream.get_module(Jet.Module.IDENTITY).register_envelop_encoding(this);
-            stream.get_module(Jet.Module.IDENTITY).register_cipher(new AesGcmCipher(16, AES_128_GCM_URI));
+            stream.get_module(Jet.Module.IDENTITY).register_cipher(new AesGcmCipher(KEY_SIZE, IV_SIZE, AES_128_GCM_URI));
         }
     }
 
@@ -114,17 +116,19 @@ public class Module : XmppStreamModule, Jet.EnvelopEncoding {
 }
 
 public class AesGcmCipher : Jet.Cipher, Object {
-    private int key_size;
+    private uint key_size;
+    private uint default_iv_size;
     private string uri;
-    public AesGcmCipher(int key_size, string uri) {
+    public AesGcmCipher(uint key_size, uint default_iv_size, string uri) {
         this.key_size = key_size;
+        this.default_iv_size = default_iv_size;
         this.uri = uri;
     }
     public string get_cipher_uri() {
         return uri;
     }
     public Jet.TransportSecret generate_random_secret() {
-        uint8[] iv = new uint8[16];
+        uint8[] iv = new uint8[default_iv_size];
         Omemo.Plugin.get_context().randomize(iv);
         uint8[] key = new uint8[key_size];
         Omemo.Plugin.get_context().randomize(key);

plugins/omemo/src/logic/trust_manager.vala

@@ -145,6 +145,8 @@ public class TrustManager {
     }
 
     public EncryptState encrypt(MessageStanza message, Jid self_jid, Gee.List<Jid> recipients, XmppStream stream, Account account) {
+        const uint KEY_SIZE = 16;
+        const uint IV_SIZE = 12;
         EncryptState status = new EncryptState();
         if (!Plugin.ensure_context()) return status;
         if (message.to == null) return status;
@@ -153,9 +155,9 @@ public class TrustManager {
 
         try {
             //Create a key and use it to encrypt the message
-            uint8[] key = new uint8[16];
+            uint8[] key = new uint8[KEY_SIZE];
             Plugin.get_context().randomize(key);
-            uint8[] iv = new uint8[16];
+            uint8[] iv = new uint8[IV_SIZE];
             Plugin.get_context().randomize(iv);
 
             uint8[] aes_encrypt_result = aes_encrypt(Cipher.AES_GCM_NOPADDING, key, iv, message.body.data);

plugins/omemo/src/protocol/stream_module.vala

@@ -5,7 +5,7 @@ using Signal;
 
 namespace Dino.Plugins.Omemo {
 
-private const string NS_URI = "eu.siacs.conversations.axolotl";
+internal const string NS_URI = "eu.siacs.conversations.axolotl";
 private const string NODE_DEVICELIST = NS_URI + ".devicelist";
 private const string NODE_BUNDLES = NS_URI + ".bundles";
 private const string NODE_VERIFICATION = NS_URI + ".verification";

plugins/signal-protocol/src/signal_helper.c

@@ -211,8 +211,6 @@ int signal_vala_encrypt(signal_buffer **output,
     int algo, mode, error_code = SG_ERR_UNKNOWN;
     if (aes_cipher(cipher, key_len, &algo, &mode)) return SG_ERR_INVAL;
 
-    if (iv_len != 16 && iv_len != 12) return SG_ERR_INVAL;
-
     gcry_cipher_hd_t ctx = {0};
 
     if (gcry_cipher_open(&ctx, algo, mode, 0)) return SG_ERR_NOMEM;
@@ -294,8 +292,6 @@ int signal_vala_decrypt(signal_buffer **output,
     if (aes_cipher(cipher, key_len, &algo, &mode)) return SG_ERR_INVAL;
     if (ciphertext_len == 0) return SG_ERR_INVAL;
 
-    if (iv_len != 16 && iv_len != 12) return SG_ERR_INVAL;
-
     gcry_cipher_hd_t ctx = {0};
 
     if (gcry_cipher_open(&ctx, algo, mode, 0)) return SG_ERR_NOMEM;