release/src/router/dnscrypt/src/libnacl/crypto_secretbox/wrapper-open.cpp

   1 #include <string>
   2 using std::string;
   3 #include "crypto_secretbox.h"
   4
   5 string crypto_secretbox_open(const string &c,const string &n,const string &k)
   6 {
   7   if (k.size() != crypto_secretbox_KEYBYTES) throw "incorrect key length";
   8   if (n.size() != crypto_secretbox_NONCEBYTES) throw "incorrect nonce length";
   9   size_t clen = c.size() + crypto_secretbox_BOXZEROBYTES;
  10   unsigned char cpad[clen];
  11   for (int i = 0;i < crypto_secretbox_BOXZEROBYTES;++i) cpad[i] = 0;
  12   for (int i = crypto_secretbox_BOXZEROBYTES;i < clen;++i) cpad[i] = c[i - crypto_secretbox_BOXZEROBYTES];
  13   unsigned char mpad[clen];
  14   if (crypto_secretbox_open(mpad,cpad,clen,(const unsigned char *) n.c_str(),(const unsigned char *) k.c_str()) != 0)
  15     throw "ciphertext fails verification";
  16   if (clen < crypto_secretbox_ZEROBYTES)
  17     throw "ciphertext too short"; // should have been caught by _open
  18   return string(
  19     (char *) mpad + crypto_secretbox_ZEROBYTES,
  20     clen - crypto_secretbox_ZEROBYTES
  21   );
  22 }