Differentiate between malformed pickle objects and trailing junk data.

Adds the OLM_PICKLE_EXTRA_DATA error code. We fail with this code when
the pickle object looks right except for some unexpected trailing bytes
which we didn't process.

include/olm/error.h

@@ -58,6 +58,12 @@ enum OlmErrorCode {
      */
     OLM_SAS_THEIR_KEY_NOT_SET = 16,
 
+    /**
+     * The pickled object was successfully decoded, but the unpickling still failed
+     * because it had some extraneous junk data at the end.
+     */
+    OLM_PICKLE_EXTRA_DATA = 17,
+
     /* remember to update the list of string constants in error.c when updating
      * this list. */
 };

src/error.c

@@ -32,7 +32,8 @@ static const char * ERRORS[] = {
     "BAD_LEGACY_ACCOUNT_PICKLE",
     "BAD_SIGNATURE",
     "OLM_INPUT_BUFFER_TOO_SMALL",
-    "OLM_SAS_THEIR_KEY_NOT_SET"
+    "OLM_SAS_THEIR_KEY_NOT_SET",
+    "OLM_PICKLE_EXTRA_DATA"
 };
 
 const char * _olm_error_to_string(enum OlmErrorCode error)

src/inbound_group_session.c

@@ -275,7 +275,7 @@ size_t olm_unpickle_inbound_group_session(
 
     if (pos != end) {
         /* Input was longer than expected. */
-        session->last_error = OLM_CORRUPTED_PICKLE;
+        session->last_error = OLM_PICKLE_EXTRA_DATA;
         return (size_t)-1;
     }
 

src/olm.cpp

@@ -303,7 +303,7 @@ size_t olm_unpickle_account(
         return std::size_t(-1);
     } else if (pos != end) {
         /* Input was longer than expected. */
-        object.last_error = OlmErrorCode::OLM_CORRUPTED_PICKLE;
+        object.last_error = OlmErrorCode::OLM_PICKLE_EXTRA_DATA;
         return std::size_t(-1);
     }
 
@@ -338,7 +338,7 @@ size_t olm_unpickle_session(
         return std::size_t(-1);
     } else if (pos != end) {
         /* Input was longer than expected. */
-        object.last_error = OlmErrorCode::OLM_CORRUPTED_PICKLE;
+        object.last_error = OlmErrorCode::OLM_PICKLE_EXTRA_DATA;
         return std::size_t(-1);
     }
 

src/outbound_group_session.c

@@ -160,7 +160,7 @@ size_t olm_unpickle_outbound_group_session(
 
     if (pos != end) {
         /* Input was longer than expected. */
-        session->last_error = OLM_CORRUPTED_PICKLE;
+        session->last_error = OLM_PICKLE_EXTRA_DATA;
         return (size_t)-1;
     }
 

src/pk.cpp

@@ -348,7 +348,7 @@ size_t olm_unpickle_pk_decryption(
         return std::size_t(-1);
     } else if (pos != end) {
         /* Input was longer than expected. */
-        object.last_error = OlmErrorCode::OLM_CORRUPTED_PICKLE;
+        object.last_error = OlmErrorCode::OLM_PICKLE_EXTRA_DATA;
         return std::size_t(-1);
     }
 

tests/test_group_session.cpp

@@ -73,7 +73,7 @@ int main() {
             "secret_key", 10,
             junk_pickle.data(), junk_pickle_length
         ));
-    assert_equals(OLM_CORRUPTED_PICKLE,
+    assert_equals(OLM_PICKLE_EXTRA_DATA,
                   olm_outbound_group_session_last_error_code(session));
 }
 
@@ -128,7 +128,7 @@ int main() {
             "secret_key", 10,
             junk_pickle.data(), junk_pickle_length
         ));
-    assert_equals(OLM_CORRUPTED_PICKLE,
+    assert_equals(OLM_PICKLE_EXTRA_DATA,
                   olm_inbound_group_session_last_error_code(session));
 }
 

tests/test_olm.cpp

@@ -83,7 +83,7 @@ const size_t junk_pickle_length = add_junk_suffix_to_pickle(
 assert_equals(std::size_t(-1),
     ::olm_unpickle_account(account, "secret_key", 10,
         junk_pickle.data(), junk_pickle_length));
-assert_equals(OLM_CORRUPTED_PICKLE, olm_account_last_error_code(account));
+assert_equals(OLM_PICKLE_EXTRA_DATA, olm_account_last_error_code(account));
 }
 
 
@@ -174,7 +174,7 @@ const size_t junk_pickle_length = add_junk_suffix_to_pickle(
 assert_equals(std::size_t(-1),
     ::olm_unpickle_session(session, "secret_key", 10,
         junk_pickle.data(), junk_pickle_length));
-assert_equals(OLM_CORRUPTED_PICKLE, olm_session_last_error_code(session));
+assert_equals(OLM_PICKLE_EXTRA_DATA, olm_session_last_error_code(session));
 }
 
 { /** Loopback test */

tests/test_pk.cpp

@@ -167,7 +167,7 @@ assert_equals(std::size_t(-1),
         junk_pickle.data(), junk_pickle_length,
         pubkey.data(), pubkey.size()
     ));
-assert_equals(OLM_CORRUPTED_PICKLE, olm_pk_decryption_last_error_code(decryption));
+assert_equals(OLM_PICKLE_EXTRA_DATA, olm_pk_decryption_last_error_code(decryption));
 /***/
 
 char *ciphertext = strdup("ntk49j/KozVFtSqJXhCejg");