Merge #21407: i2p: limit the size of incoming messages

7059e6d82275b44efc41675ee10760145b6c1073 test: add a test to ensure RecvUntilTerminator() limit works (Vasil Dimov)
80a5a8ea2b7ad512c74c29df5b504e9be6cf23a0 i2p: limit the size of incoming messages (Vasil Dimov)

Pull request description:

  Put a limit on the amount of data `Sock::RecvUntilTerminator()` can read
  if no terminator is received.

  In the case of I2P this avoids a runaway (or malicious) I2P proxy
  sending us tons of data without a terminator before a timeout is
  triggered.

ACKs for top commit:
  laanwj:
    Re-ACK 7059e6d82275b44efc41675ee10760145b6c1073

Tree-SHA512: 21f3f3468c765c726cdc877eae847cdb4dbe225d94c5bd1849bd752c9761fac881c554f16ea7a685ad40312159d554e126c481e21c5fd83a6d947060b920373d

1 files changed, 31 insertions, 0 deletions

diff --git a/src/test/sock_tests.cpp b/src/test/sock_tests.cpp
index ed9780dfb5..400de875b7 100644
--- a/src/test/sock_tests.cpp
+++ b/src/test/sock_tests.cpp
@@ -4,11 +4,13 @@
 
 #include <compat.h>
 #include <test/util/setup_common.h>
+#include <threadinterrupt.h>
 #include <util/sock.h>
 #include <util/system.h>
 
 #include <boost/test/unit_test.hpp>
 
+#include <cassert>
 #include <thread>
 
 using namespace std::chrono_literals;
@@ -144,6 +146,35 @@ BOOST_AUTO_TEST_CASE(wait)
     waiter.join();
 }
 
+BOOST_AUTO_TEST_CASE(recv_until_terminator_limit)
+{
+    constexpr auto timeout = 1min; // High enough so that it is never hit.
+    CThreadInterrupt interrupt;
+    int s[2];
+    CreateSocketPair(s);
+
+    Sock sock_send(s[0]);
+    Sock sock_recv(s[1]);
+
+    std::thread receiver([&sock_recv, &timeout, &interrupt]() {
+        constexpr size_t max_data{10};
+        bool threw_as_expected{false};
+        // BOOST_CHECK_EXCEPTION() writes to some variables shared with the main thread which
+        // creates a data race. So mimic it manually.
+        try {
+            sock_recv.RecvUntilTerminator('\n', timeout, interrupt, max_data);
+        } catch (const std::runtime_error& e) {
+            threw_as_expected = HasReason("too many bytes without a terminator")(e);
+        }
+        assert(threw_as_expected);
+    });
+
+    BOOST_REQUIRE_NO_THROW(sock_send.SendComplete("1234567", timeout, interrupt));
+    BOOST_REQUIRE_NO_THROW(sock_send.SendComplete("89a\n", timeout, interrupt));
+
+    receiver.join();
+}
+
 #endif /* WIN32 */
 
 BOOST_AUTO_TEST_SUITE_END()