lib/net: Limit the maximum size of TCP or SSL input buffers

This commit is the 2/3 part of the fix for the following security
vulnerability:
 - CVE-2021-42076 DoS via excess length messages

The issue has been reported by Matthias Gerstner <mgerstner@suse.de>.

(cherry picked from commit af90f39b4a)

src/lib/net/SecureSocket.cpp

@@ -40,6 +40,7 @@
 
 #define MAX_ERROR_SIZE 65535
 
+static const std::size_t MAX_INPUT_BUFFER_SIZE = 1024 * 1024;
 static const float s_retryDelay = 0.01f;
 
 enum {
@@ -180,7 +181,11 @@ SecureSocket::doRead()
         // slurp up as much as possible
         do {
             m_inputBuffer.write(buffer, bytesRead);
-            
+
+            if (m_inputBuffer.getSize() > MAX_INPUT_BUFFER_SIZE) {
+                break;
+            }
+
             status = secureRead(buffer, sizeof(buffer), bytesRead);
             if (status < 0) {
                 return kBreak;

src/lib/net/TCPSocket.cpp

@@ -33,9 +33,7 @@
 #include <cstdlib>
 #include <memory>
 
-//
-// TCPSocket
-//
+static const std::size_t MAX_INPUT_BUFFER_SIZE = 1024 * 1024;
 
 TCPSocket::TCPSocket(IEventQueue* events, SocketMultiplexer* socketMultiplexer, IArchNetwork::EAddressFamily family) :
     IDataSocket(events),
@@ -345,6 +343,10 @@ TCPSocket::doRead()
         do {
             m_inputBuffer.write(buffer, (UInt32)bytesRead);
 
+            if (m_inputBuffer.getSize() > MAX_INPUT_BUFFER_SIZE) {
+                break;
+            }
+
             bytesRead = ARCH->readSocket(m_socket, buffer, sizeof(buffer));
         } while (bytesRead > 0);