bignum: Define bignum_dup(bignum orig, bignum *dest)

The macro is defined for each crypto back end.  If (*dest) is NULL, a
new bignum is allocated.  Otherwise the value of orig is copied to
(*dest).

Signed-off-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>

include/libssh/libcrypto.h

@@ -102,6 +102,14 @@ typedef BN_CTX* bignum_CTX;
 #define bignum_bn2bin(num,len, ptr) BN_bn2bin(num, ptr)
 #define bignum_cmp(num1,num2) BN_cmp(num1,num2)
 #define bignum_rshift1(dest, src) BN_rshift1(dest, src)
+#define bignum_dup(orig, dest) do { \
+        if (*(dest) == NULL) { \
+            *(dest) = BN_dup(orig); \
+        } else { \
+            BN_copy(*(dest), orig); \
+        } \
+    } while(0)
+
 
 /* Returns true if the OpenSSL is operating in FIPS mode */
 #define ssh_fips_mode() (FIPS_mode() != 0)

include/libssh/libgcrypt.h

@@ -92,6 +92,13 @@ int ssh_gcry_rand_range(bignum rnd, bignum max);
 #define bignum_sub(dst, a, b) gcry_mpi_sub(dst, a, b)
 #define bignum_mod(dst, a, b, ctx) 1,gcry_mpi_mod(dst, a, b)
 #define bignum_rand_range(rnd, max) ssh_gcry_rand_range(rnd, max);
+#define bignum_dup(orig, dest) do { \
+        if (*(dest) == NULL) { \
+            *(dest) = gcry_mpi_copy(orig); \
+        } else { \
+            gcry_mpi_set(*(dest), orig); \
+        } \
+    } while(0)
 /* Helper functions for data conversions.  */
 
 /* Extract an MPI from the given s-expression SEXP named NAME which is

include/libssh/libmbedcrypto.h

@@ -118,6 +118,14 @@ int ssh_mbedcry_hex2bn(bignum *dest, char *data);
         mbedtls_mpi_size(num))
 #define bignum_cmp(num1, num2) mbedtls_mpi_cmp_mpi(num1, num2)
 #define bignum_rshift1(dest, src) mbedtls_mpi_copy(dest, src), mbedtls_mpi_shift_r(dest, 1)
+#define bignum_dup(orig, dest) do { \
+    if (*(dest) == NULL) { \
+        *(dest) = bignum_new(); \
+    } \
+    if (*(dest) != NULL) { \
+        mbedtls_mpi_copy(orig, *(dest)); \
+    } \
+    } while(0)
 
 mbedtls_ctr_drbg_context *ssh_get_mbedtls_ctr_drbg_context(void);