Fix BER decoder integer overflow

2 files changed, 41 insertions, 1 deletions

diff --git a/src/lib/utils/info.txt b/src/lib/utils/info.txt
index 820dd407d..306e6e9ad 100644
--- a/src/lib/utils/info.txt
+++ b/src/lib/utils/info.txt
@@ -1,4 +1,4 @@
-define UTIL_FUNCTIONS 20150919
+define UTIL_FUNCTIONS 20161127
 
 load_on always
 
@@ -31,6 +31,7 @@ filesystem.h
 os_utils.h
 prefetch.h
 rounding.h
+safeint.h
 semaphore.h
 stl_util.h
 </header:internal>
diff --git a/src/lib/utils/safeint.h b/src/lib/utils/safeint.h
new file mode 100644
index 000000000..e0bd66232
--- /dev/null
+++ b/src/lib/utils/safeint.h
@@ -0,0 +1,39 @@
+/*
+* Safe(r) Integer Handling
+* (C) 2016 Jack Lloyd
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#ifndef BOTAN_UTILS_SAFE_INT_H__
+#define BOTAN_UTILS_SAFE_INT_H__
+
+#include <botan/exceptn.h>
+#include <string>
+
+namespace Botan {
+
+class Integer_Overflow_Detected : public Exception
+   {
+   public:
+      Integer_Overflow_Detected(const std::string& file, int line) :
+         Exception("Integer overflow detected at " + file + ":" + std::to_string(line))
+         {}
+   };
+
+inline size_t checked_add(size_t x, size_t y, const char* file, int line)
+   {
+   // TODO: use __builtin_x_overflow on GCC and Clang
+   size_t z = x + y;
+   if(z < x)
+      {
+      throw Integer_Overflow_Detected(file, line);
+      }
+   return z;
+   }
+
+#define BOTAN_CHECKED_ADD(x,y) checked_add(x,y,__FILE__,__LINE__)
+
+}
+
+#endif