Version the pickled objects and check for errors when unpickling them

include/olm/error.hh

@@ -27,6 +27,8 @@ enum struct ErrorCode {
     BAD_MESSAGE_KEY_ID = 6, /*!< The message references an unknown key id */
     INVALID_BASE64 = 7, /*!< The input base64 was invalid */
     BAD_ACCOUNT_KEY = 8, /*!< The supplied account key is invalid */
+    UNKNOWN_PICKLE_VERSION = 9, /*!< The pickled object is too new */
+    CORRUPTED_PICKLE = 10, /*!< The pickled object couldn't be decoded */
 };
 
 } // namespace olm

src/account.cpp

@@ -360,11 +360,16 @@ static std::uint8_t const * unpickle(
 
 } // namespace olm
 
+namespace {
+static const std::uint32_t ACCOUNT_PICKLE_VERSION = 1;
+}
+
 
 std::size_t olm::pickle_length(
     olm::Account const & value
 ) {
     std::size_t length = 0;
+    length += olm::pickle_length(ACCOUNT_PICKLE_VERSION);
     length += olm::pickle_length(value.identity_keys);
     length += olm::pickle_length(value.one_time_keys);
     length += olm::pickle_length(value.next_one_time_key_id);
@@ -376,6 +381,7 @@ std::uint8_t * olm::pickle(
     std::uint8_t * pos,
     olm::Account const & value
 ) {
+    pos = olm::pickle(pos, ACCOUNT_PICKLE_VERSION);
     pos = olm::pickle(pos, value.identity_keys);
     pos = olm::pickle(pos, value.one_time_keys);
     pos = olm::pickle(pos, value.next_one_time_key_id);
@@ -387,6 +393,12 @@ std::uint8_t const * olm::unpickle(
     std::uint8_t const * pos, std::uint8_t const * end,
     olm::Account & value
 ) {
+    uint32_t pickle_version;
+    pos = olm::unpickle(pos, end, pickle_version);
+    if (pickle_version != ACCOUNT_PICKLE_VERSION) {
+        value.last_error = olm::ErrorCode::UNKNOWN_PICKLE_VERSION;
+        return end;
+    }
     pos = olm::unpickle(pos, end, value.identity_keys);
     pos = olm::unpickle(pos, end, value.one_time_keys);
     pos = olm::unpickle(pos, end, value.next_one_time_key_id);

src/olm.cpp

@@ -151,7 +151,7 @@ std::size_t b64_input(
     return raw_length;
 }
 
-const char * errors[9] {
+const char * errors[11] {
     "SUCCESS",
     "NOT_ENOUGH_RANDOM",
     "OUTPUT_BUFFER_TOO_SMALL",
@@ -161,6 +161,8 @@ const char * errors[9] {
     "BAD_MESSAGE_KEY_ID",
     "INVALID_BASE64",
     "BAD_ACCOUNT_KEY",
+    "UNKNOWN_PICKLE_VERSION",
+    "CORRUPTED_PICKLE",
 };
 
 } // namespace
@@ -282,7 +284,16 @@ size_t olm_unpickle_account(
         return std::size_t(-1);
     }
     std::uint8_t * const end = pos + raw_length;
-    unpickle(pos, end, object);
+    /* On success unpickle will return (pos + raw_length). If unpickling
+     * terminates too soon then it will return a pointer before
+     * (pos + raw_length). On error unpickle will return (pos + raw_length + 1).
+     */
+    if (end != unpickle(pos, end + 1, object)) {
+        if (object.last_error == olm::ErrorCode::SUCCESS) {
+            object.last_error = olm::ErrorCode::CORRUPTED_PICKLE;
+        }
+        return std::size_t(-1);
+    }
     return pickled_length;
 }
 
@@ -300,8 +311,18 @@ size_t olm_unpickle_session(
     if (raw_length == std::size_t(-1)) {
         return std::size_t(-1);
     }
-    std::uint8_t * const end = pos + raw_length;
-    unpickle(pos, end, object);
+
+    std::uint8_t * const end = pos + raw_length + 1;
+    /* On success unpickle will return (pos + raw_length). If unpickling
+     * terminates too soon then it will return a pointer before
+     * (pos + raw_length). On error unpickle will return (pos + raw_length + 1).
+     */
+    if (end != unpickle(pos, end + 1, object)) {
+        if (object.last_error == olm::ErrorCode::SUCCESS) {
+            object.last_error = olm::ErrorCode::CORRUPTED_PICKLE;
+        }
+        return std::size_t(-1);
+    }
     return pickled_length;
 }
 

src/session.cpp

@@ -353,11 +353,15 @@ std::size_t olm::Session::decrypt(
     return result;
 }
 
+namespace {
+static const std::uint32_t SESSION_PICKLE_VERSION = 1;
+}
 
 std::size_t olm::pickle_length(
     Session const & value
 ) {
     std::size_t length = 0;
+    length += olm::pickle_length(SESSION_PICKLE_VERSION);
     length += olm::pickle_length(value.received_message);
     length += olm::pickle_length(value.alice_identity_key);
     length += olm::pickle_length(value.alice_base_key);
@@ -371,6 +375,7 @@ std::uint8_t * olm::pickle(
     std::uint8_t * pos,
     Session const & value
 ) {
+    pos = olm::pickle(pos, SESSION_PICKLE_VERSION);
     pos = olm::pickle(pos, value.received_message);
     pos = olm::pickle(pos, value.alice_identity_key);
     pos = olm::pickle(pos, value.alice_base_key);
@@ -384,6 +389,12 @@ std::uint8_t const * olm::unpickle(
     std::uint8_t const * pos, std::uint8_t const * end,
     Session & value
 ) {
+    uint32_t pickle_version;
+    pos = olm::unpickle(pos, end, pickle_version);
+    if (pickle_version != SESSION_PICKLE_VERSION) {
+        value.last_error = olm::ErrorCode::UNKNOWN_PICKLE_VERSION;
+        return end;
+    }
     pos = olm::unpickle(pos, end, value.received_message);
     pos = olm::unpickle(pos, end, value.alice_identity_key);
     pos = olm::unpickle(pos, end, value.alice_base_key);