* Add LeaseSetBufferValidate which checks lease validity and extracts timestamp

* check for leases with LeaseSetBufferValidate before update in floodfill code as to prevent malicous nodes removing good LS

libi2pd/LeaseSet.h

@@ -95,6 +95,12 @@ namespace data
 			size_t m_BufferLen;
 	};
 
+	/**
+			validate lease set buffer signature and extract expiration timestamp
+			@returns true if the leaseset is well formed and signature is valid
+	 */
+	bool LeaseSetBufferValidate(const uint8_t * ptr, size_t sz, uint64_t & expires);
+
 	class LocalLeaseSet
 	{
 		public: