Merge pull request #314 from randombit/ct-tls-cbc-padding

TLS improvements

1 files changed, 53 insertions, 1 deletions

diff --git a/src/lib/utils/ct_utils.h b/src/lib/utils/ct_utils.h
index 52a3bc388..2307dd587 100644
--- a/src/lib/utils/ct_utils.h
+++ b/src/lib/utils/ct_utils.h
@@ -14,7 +14,7 @@
 #ifndef BOTAN_TIMING_ATTACK_CM_H__
 #define BOTAN_TIMING_ATTACK_CM_H__
 
-#include <botan/types.h>
+#include <botan/secmem.h>
 #include <vector>
 
 #if defined(BOTAN_USE_CTGRIND)
@@ -51,6 +51,12 @@ inline void unpoison(T* p, size_t n)
 #endif
    }
 
+template<typename T>
+inline void unpoison(T& p)
+   {
+   unpoison(&p, 1);
+   }
+
 /*
 * T should be an unsigned machine integer type
 * Expand to a mask used for other operations
@@ -90,6 +96,16 @@ inline T is_equal(T x, T y)
    }
 
 template<typename T>
+inline T is_less(T x, T y)
+   {
+   /*
+   This expands to a constant time sequence with GCC 5.2.0 on x86-64
+   but something more complicated may be needed for portable const time.
+   */
+   return expand_mask<T>(x < y);
+   }
+
+template<typename T>
 inline void conditional_copy_mem(T value,
                                  T* to,
                                  const T* from0,
@@ -102,6 +118,42 @@ inline void conditional_copy_mem(T value,
       to[i] = CT::select(mask, from0[i], from1[i]);
    }
 
+template<typename T>
+inline T expand_top_bit(T a)
+   {
+   return expand_mask<T>(a >> (sizeof(T)*8-1));
+   }
+
+template<typename T>
+inline T max(T a, T b)
+   {
+   const T a_larger = b - a; // negative if a is larger
+   return select(expand_top_bit(a), a, b);
+   }
+
+template<typename T>
+inline T min(T a, T b)
+   {
+   const T a_larger = b - a; // negative if a is larger
+   return select(expand_top_bit(b), b, a);
+   }
+
+template<typename T, typename Alloc>
+std::vector<T, Alloc> strip_leading_zeros(const std::vector<T, Alloc>& input)
+   {
+   size_t leading_zeros = 0;
+
+   uint8_t only_zeros = 0xFF;
+
+   for(size_t i = 0; i != input.size(); ++i)
+      {
+      only_zeros &= CT::is_zero(input[i]);
+      leading_zeros += CT::select<uint8_t>(only_zeros, 1, 0);
+      }
+
+   return secure_vector<byte>(input.begin() + leading_zeros, input.end());
+   }
+
 }
 
 }