::crypto::tink::JsonKeysetReader may crash on invalid input before tink-cc version 2.1.3.

[juergw]

::crypto::tink::JsonKeysetReader parses keysets in Tink's JSON proto keyset format.

In older releases of tink-cc, there were some cases where it would crash on some invalid inputs. Here is an example:

constexpr absl::string_view kJsonTink = "NDMyNjg4NTA5MjQxMjUzMDczCg=="; // Encodes an integer
std::string decoded_key;
absl::Base64Unescape(kJsonTink, &decoded_key);
auto json_result = crypto::tink::JsonKeysetReader::New(decoded_key);
EXPECT_OK(json_result);
auto keyset_result = json_result.value()->Read(); // Will cause a crash

also, large and highly nested inputs were able to cause the stack to overflow.

Both of these issue are fixed in release 2.1.3.
See da091f8 and dfbbe8f.