initial commit

libpcp/mac.c

@@ -0,0 +1,97 @@
+#include "mac.h"
+
+
+
+
+
+unsigned char *pcp_derivekey(char *passphrase) {
+  unsigned char *hash64 = ucmalloc(crypto_hash_BYTES);
+  unsigned char *xor = ucmalloc(crypto_secretbox_KEYBYTES);
+  unsigned char *key = ucmalloc(crypto_secretbox_KEYBYTES);
+
+  size_t plen = strnlen(passphrase, 255);
+  unsigned char *temp = ucmalloc(crypto_hash_BYTES);
+  int i;
+
+  // make a hash from the passphrase and then HCYCLES times from the result
+  memcpy(temp, passphrase, plen);
+  for(i=0; i<HCYCLES; ++i) {
+    if(crypto_hash(hash64, temp, plen) == 0) {
+      memcpy(temp, hash64, crypto_hash_BYTES);
+    }
+  }
+
+  // xor the first half of the hash with the latter to get
+  // a 32 byte array
+  for(i=0; i<crypto_secretbox_KEYBYTES; ++i) {
+    xor[i] = hash64[i] ^ hash64[i + crypto_secretbox_KEYBYTES];
+  }
+
+  // turn the 32byte hash into a secret key
+  xor[0]  &= 248;
+  xor[31] &= 127;
+  xor[31] |= 64;
+
+  memcpy(key, xor, crypto_secretbox_KEYBYTES);
+
+  bzero(passphrase, plen);
+  bzero(temp, crypto_hash_BYTES);
+  free(passphrase);
+  free(temp);
+  free(xor);
+  free(hash64);
+
+  return key;
+}
+
+
+size_t pcp_sodium_mac(unsigned char **cipher,
+		unsigned char *cleartext,
+		size_t clearsize,
+		unsigned char *nonce,
+		unsigned char *key) {
+  unsigned char *pad_clear;
+  unsigned char *pad_cipher;
+
+  pad_cipher = ucmalloc(crypto_secretbox_ZEROBYTES + clearsize);
+
+  pcp_pad_prepend(&pad_clear, cleartext, crypto_secretbox_ZEROBYTES, clearsize);
+
+  crypto_secretbox(pad_cipher, pad_clear,
+		   clearsize + crypto_secretbox_ZEROBYTES, nonce, key);
+
+  pcp_pad_remove(cipher, pad_cipher, crypto_secretbox_BOXZEROBYTES,
+     (clearsize + crypto_secretbox_ZEROBYTES) - crypto_secretbox_BOXZEROBYTES);
+
+  free(pad_clear);
+  free(pad_cipher);
+
+  return (clearsize + crypto_secretbox_ZEROBYTES) - crypto_secretbox_BOXZEROBYTES;
+}
+
+int pcp_sodium_verify_mac(unsigned char **cleartext, unsigned char* message,
+			  size_t messagesize, unsigned char *nonce,
+			  unsigned char *key) {
+  // verify the mac
+  unsigned char *pad_cipher;
+  unsigned char *pad_clear;
+  int success = -1;
+
+  pcp_pad_prepend(&pad_cipher, message, crypto_secretbox_BOXZEROBYTES, messagesize);
+
+  pad_clear = (unsigned char *)ucmalloc((crypto_secretbox_BOXZEROBYTES + messagesize));
+
+  if (crypto_secretbox_open(pad_clear,
+			    pad_cipher,
+			    messagesize + crypto_secretbox_BOXZEROBYTES,
+			    nonce, key) == 0) {
+    success = 0;
+  }
+
+  pcp_pad_remove(cleartext, pad_clear, crypto_secretbox_ZEROBYTES, messagesize);
+
+  free(pad_clear);
+  free(pad_cipher);
+
+  return success;
+}