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Fix issue #135: Segfault in Message::peekType()

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* Add missing nullptr check in Message::peekType().

* According to its specification, sd_bus_message_peek_type() sets a
  given contents parameter to NULL if the next element in a message is
  not a container. Since assigning a nullptr to a std::string has
  undefined behaviour (typically resulting in an invalid memory access),
  Message::peekType() must not assign contentsSig unconditionally.
This commit is contained in:
Benjamin Kaufmann
2021-06-12 13:02:17 +02:00
committed by Stanislav Angelovič
parent fa9569fdd9
commit a5e94f07bf
2 changed files with 27 additions and 1 deletions
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2
src/Message.cpp
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@ -617,7 +617,7 @@ void Message::peekType(std::string& type, std::string& contents) const
auto r = sd_bus_message_peek_type((sd_bus_message*)msg_, &typeSig, &contentsSig);
SDBUS_THROW_ERROR_IF(r < 0, "Failed to peek message type", -r);
type = typeSig;
contents = contentsSig;
contents = contentsSig ? contentsSig : "";
}
bool Message::isValid() const

26
tests/unittests/Message_test.cpp
View File

@ -238,3 +238,29 @@ TEST(AMessage, CanCarryAComplexType)
ASSERT_THAT(dataRead, Eq(dataWritten));
}
TEST(AMessage, CanPeekASimpleType)
{
auto msg = sdbus::createPlainMessage();
msg << 123;
msg.seal();
std::string type;
std::string contents;
msg.peekType(type, contents);
ASSERT_THAT(type, "i");
ASSERT_THAT(contents, "");
}
TEST(AMessage, CanPeekContainerContents)
{
auto msg = sdbus::createPlainMessage();
msg << std::map<int, std::string>{{1, "one"}, {2, "two"}};
msg.seal();
std::string type;
std::string contents;
msg.peekType(type, contents);
ASSERT_THAT(type, "a");
ASSERT_THAT(contents, "{is}");
}