Pass workspace size to various bigint_ functions

These functions made assumptions about the workspace size available,
which if incorrect would cause memory corruption. Since the length is
always available at the caller, just provide it and avoid problems.

1 files changed, 9 insertions, 7 deletions

diff --git a/src/lib/math/mp/mp_karat.cpp b/src/lib/math/mp/mp_karat.cpp
index 8348025d9..fb8b16161 100644
--- a/src/lib/math/mp/mp_karat.cpp
+++ b/src/lib/math/mp/mp_karat.cpp
@@ -250,18 +250,19 @@ size_t karatsuba_size(size_t z_size, size_t x_size, size_t x_sw)
 /*
 * Multiplication Algorithm Dispatcher
 */
-void bigint_mul(BigInt& z, const BigInt& x, const BigInt& y, word workspace[])
+void bigint_mul(BigInt& z, const BigInt& x, const BigInt& y,
+                word workspace[], size_t ws_size)
    {
    return bigint_mul(z.mutable_data(), z.size(),
                      x.data(), x.size(), x.sig_words(),
                      y.data(), y.size(), y.sig_words(),
-                     workspace);
+                     workspace, ws_size);
    }
 
 void bigint_mul(word z[], size_t z_size,
                 const word x[], size_t x_size, size_t x_sw,
                 const word y[], size_t y_size, size_t y_sw,
-                word workspace[])
+                word workspace[], size_t ws_size)
    {
    clear_mem(z, z_size);
 
@@ -308,7 +309,7 @@ void bigint_mul(word z[], size_t z_size,
       {
       const size_t N = karatsuba_size(z_size, x_size, x_sw, y_size, y_sw);
 
-      if(N)
+      if(N && ws_size >= 2*N)
          karatsuba_mul(z, x, y, N, workspace);
       else
          basecase_mul(z, x, x_sw, y, y_sw);
@@ -318,8 +319,9 @@ void bigint_mul(word z[], size_t z_size,
 /*
 * Squaring Algorithm Dispatcher
 */
-void bigint_sqr(word z[], size_t z_size, word workspace[],
-                const word x[], size_t x_size, size_t x_sw)
+void bigint_sqr(word z[], size_t z_size,
+                const word x[], size_t x_size, size_t x_sw,
+                word workspace[], size_t ws_size)
    {
    BOTAN_ASSERT(z_size/2 >= x_sw, "Output size is sufficient");
 
@@ -355,7 +357,7 @@ void bigint_sqr(word z[], size_t z_size, word workspace[],
       {
       const size_t N = karatsuba_size(z_size, x_size, x_sw);
 
-      if(N)
+      if(N && ws_size >= 2*N)
          karatsuba_sqr(z, x, N, workspace);
       else
          basecase_mul(z, x, x_sw, x, x_sw);