bignums: detach bignum-related functions from dh.c.

Reviewed-by: Andreas Schneider <asn@samba.org>

1 files changed, 94 insertions, 0 deletions

diff --git a/src/bignum.c b/src/bignum.c
new file mode 100644
index 00000000..6904c5d9
--- /dev/null
+++ b/src/bignum.c
@@ -0,0 +1,94 @@
+/*
+ * This file is part of the SSH Library
+ *
+ * Copyright (c) 2014 by Aris Adamantiadis <aris@badcode.be>
+ *
+ * The SSH Library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or (at your
+ * option) any later version.
+ *
+ * The SSH Library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with the SSH Library; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+#include "libssh/priv.h"
+#include "libssh/bignum.h"
+#include "libssh/string.h"
+
+ssh_string make_bignum_string(bignum num) {
+  ssh_string ptr = NULL;
+  int pad = 0;
+  unsigned int len = bignum_num_bytes(num);
+  unsigned int bits = bignum_num_bits(num);
+
+  if (len == 0) {
+      return NULL;
+  }
+
+  /* If the first bit is set we have a negative number */
+  if (!(bits % 8) && bignum_is_bit_set(num, bits - 1)) {
+    pad++;
+  }
+
+#ifdef DEBUG_CRYPTO
+  fprintf(stderr, "%d bits, %d bytes, %d padding\n", bits, len, pad);
+#endif /* DEBUG_CRYPTO */
+
+  ptr = ssh_string_new(len + pad);
+  if (ptr == NULL) {
+    return NULL;
+  }
+
+  /* We have a negative number so we need a leading zero */
+  if (pad) {
+    ptr->data[0] = 0;
+  }
+
+#ifdef HAVE_LIBGCRYPT
+  bignum_bn2bin(num, len, ptr->data + pad);
+#elif HAVE_LIBCRYPTO
+  bignum_bn2bin(num, ptr->data + pad);
+#endif
+
+  return ptr;
+}
+
+bignum make_string_bn(ssh_string string){
+  bignum bn = NULL;
+  unsigned int len = ssh_string_len(string);
+
+#ifdef DEBUG_CRYPTO
+  fprintf(stderr, "Importing a %d bits, %d bytes object ...\n",
+      len * 8, len);
+#endif /* DEBUG_CRYPTO */
+
+#ifdef HAVE_LIBGCRYPT
+  bignum_bin2bn(string->data, len, &bn);
+#elif defined HAVE_LIBCRYPTO
+  bn = bignum_bin2bn(string->data, len, NULL);
+#endif
+
+  return bn;
+}
+
+/* prints the bignum on stderr */
+void ssh_print_bignum(const char *which, bignum num) {
+#ifdef HAVE_LIBGCRYPT
+  unsigned char *hex = NULL;
+  bignum_bn2hex(num, &hex);
+#elif defined HAVE_LIBCRYPTO
+  char *hex = NULL;
+  hex = bignum_bn2hex(num);
+#endif
+  fprintf(stderr, "%s value: ", which);
+  fprintf(stderr, "%s\n", (hex == NULL) ? "(null)" : (char *) hex);
+  SAFE_FREE(hex);
+}