1 files changed, 27 insertions, 0 deletions

diff --git a/nacl/crypto_box/wrapper-open.cpp b/nacl/crypto_box/wrapper-open.cpp
new file mode 100644
index 00000000..67663a21
--- /dev/null
+++ b/nacl/crypto_box/wrapper-open.cpp
@@ -0,0 +1,27 @@
+#include <string>
+using std::string;
+#include "crypto_box.h"
+
+string crypto_box_open(const string &c,const string &n,const string &pk,const string &sk)
+{
+  if (pk.size() != crypto_box_PUBLICKEYBYTES) throw "incorrect public-key length";
+  if (sk.size() != crypto_box_SECRETKEYBYTES) throw "incorrect secret-key length";
+  if (n.size() != crypto_box_NONCEBYTES) throw "incorrect nonce length";
+  size_t clen = c.size() + crypto_box_BOXZEROBYTES;
+  unsigned char cpad[clen];
+  for (int i = 0;i < crypto_box_BOXZEROBYTES;++i) cpad[i] = 0;
+  for (int i = crypto_box_BOXZEROBYTES;i < clen;++i) cpad[i] = c[i - crypto_box_BOXZEROBYTES];
+  unsigned char mpad[clen];
+  if (crypto_box_open(mpad,cpad,clen,
+                       (const unsigned char *) n.c_str(),
+                       (const unsigned char *) pk.c_str(),
+                       (const unsigned char *) sk.c_str()
+                     ) != 0)
+    throw "ciphertext fails verification";
+  if (clen < crypto_box_ZEROBYTES)
+    throw "ciphertext too short"; // should have been caught by _open
+  return string(
+    (char *) mpad + crypto_box_ZEROBYTES,
+    clen - crypto_box_ZEROBYTES
+  );
+}