Implemented the correct way to calculate MAC from a tag, feeding it an extra 32 zeroe...

[proxmark3-svn] / armsrc / optimized_cipher.c

diff --git a/armsrc/optimized_cipher.c b/armsrc/optimized_cipher.c
index 067e9022655e422f359ac46370977c35329fbea2..444b93d09f688db68b71d152745c3a92f84c6b43 100644 (file)
--- a/armsrc/optimized_cipher.c
+++ b/armsrc/optimized_cipher.c
@@ -68,21 +68,6 @@
 #include <stdint.h>
 #include <time.h>
 
-/**
-* Definition 1 (Cipher state). A cipher state of iClass s is an element of F 40/2
-* consisting of the following four components:
-*      1. the left register l = (l 0 . . . l 7 ) ∈ F 8/2 ;
-*      2. the right register r = (r 0 . . . r 7 ) ∈ F 8/2 ;
-*      3. the top register t = (t 0 . . . t 15 ) ∈ F 16/2 .
-*      4. the bottom register b = (b 0 . . . b 7 ) ∈ F 8/2 .
-**/
-typedef struct {
-       uint8_t l;
-       uint8_t r;
-       uint8_t b;
-       uint16_t t;
-} State;
-
 
 #define opt_T(s) (0x1 & ((s->t >> 15) ^ (s->t >> 14)^ (s->t >> 10)^ (s->t >> 8)^ (s->t >> 5)^ (s->t >> 4)^ (s->t >> 1)^ s->t))
 
@@ -118,7 +103,7 @@ uint8_t xopt__select(bool x, bool y, uint8_t r)
 }
 */
 
-void opt_successor(uint8_t* k, State *s, bool y, State* successor)
+void opt_successor(const uint8_t* k, State *s, bool y, State* successor)
 {
 
        uint8_t Tt = 1 & opt_T(s);
@@ -134,12 +119,12 @@ void opt_successor(uint8_t* k, State *s, bool y, State* successor)
 
 }
 
-void opt_suc(uint8_t* k,State* s, uint8_t *in)
+void opt_suc(const uint8_t* k,State* s, uint8_t *in, uint8_t length, bool add32Zeroes)
 {
        State x2;
        int i;
        uint8_t head = 0;
-       for(i =0 ; i < 12 ; i++)
+       for(i =0 ; i < length  ; i++)
        {
                head = 1 & (in[i] >> 7);
                opt_successor(k,s,head,&x2);
@@ -166,10 +151,16 @@ void opt_suc(uint8_t* k,State* s, uint8_t *in)
                opt_successor(k,&x2,head,s);
 
        }
-
+       //For tag MAC, an additional 32 zeroes
+       if(add32Zeroes)
+               for(i =0 ; i < 16 ; i++)
+               {
+                       opt_successor(k,s,0,&x2);
+                       opt_successor(k,&x2,0,s);
+               }
 }
 
-void opt_output(uint8_t* k,State* s,  uint8_t *buffer)
+void opt_output(const uint8_t* k,State* s,  uint8_t *buffer)
 {
        uint8_t times = 0;
        uint8_t bout = 0;
@@ -207,7 +198,7 @@ void opt_MAC(uint8_t* k, uint8_t* input, uint8_t* out)
                        0xE012 // t
                        };
 
-       opt_suc(k,&_init,input);
+       opt_suc(k,&_init,input,12, false);
        //printf("\noutp ");
        opt_output(k,&_init, out);
 }
@@ -224,16 +215,74 @@ void opt_reverse_arraybytecpy(uint8_t* dest, uint8_t *src, size_t len)
                dest[i] = rev_byte(src[i]);
 }
 
-void opt_doMAC(uint8_t *cc_nr_p, uint8_t *div_key_p, uint8_t mac[4])
+void opt_doReaderMAC(uint8_t *cc_nr_p, uint8_t *div_key_p, uint8_t mac[4])
 {
-       static uint8_t cc_nr[13];
-       static uint8_t div_key[8];
+       static uint8_t cc_nr[12];
 
        opt_reverse_arraybytecpy(cc_nr, cc_nr_p,12);
-       memcpy(div_key,div_key_p,8);
        uint8_t dest []= {0,0,0,0,0,0,0,0};
-       opt_MAC(div_key,cc_nr, dest);
+       opt_MAC(div_key_p,cc_nr, dest);
+       //The output MAC must also be reversed
+       opt_reverse_arraybytecpy(mac, dest,4);
+       return;
+}
+void opt_doTagMAC(uint8_t *cc_p, const uint8_t *div_key_p, uint8_t mac[4])
+{
+       static uint8_t cc_nr[8+4+4];
+       opt_reverse_arraybytecpy(cc_nr, cc_p,12);
+       State _init  =  {
+                       ((div_key_p[0] ^ 0x4c) + 0xEC) & 0xFF,// l
+                       ((div_key_p[0] ^ 0x4c) + 0x21) & 0xFF,// r
+                       0x4c, // b
+                       0xE012 // t
+                       };
+       opt_suc(div_key_p,&_init,cc_nr, 12,true);
+       uint8_t dest []= {0,0,0,0};
+       opt_output(div_key_p,&_init, dest);
+       //The output MAC must also be reversed
+       opt_reverse_arraybytecpy(mac, dest,4);
+       return;
+
+}
+/**
+ * The tag MAC can be divided (both can, but no point in dividing the reader mac) into
+ * two functions, since the first 8 bytes are known, we can pre-calculate the state
+ * reached after feeding CC to the cipher.
+ * @param cc_p
+ * @param div_key_p
+ * @return the cipher state
+ */
+State opt_doTagMAC_1(uint8_t *cc_p, const uint8_t *div_key_p)
+{
+       static uint8_t cc_nr[8];
+       opt_reverse_arraybytecpy(cc_nr, cc_p,8);
+       State _init  =  {
+                       ((div_key_p[0] ^ 0x4c) + 0xEC) & 0xFF,// l
+                       ((div_key_p[0] ^ 0x4c) + 0x21) & 0xFF,// r
+                       0x4c, // b
+                       0xE012 // t
+                       };
+       opt_suc(div_key_p,&_init,cc_nr, 8,false);
+       return _init;
+}
+/**
+ * The second part of the tag MAC calculation, since the CC is already calculated into the state,
+ * this function is fed only the NR, and internally feeds the remaining 32 0-bits to generate the tag
+ * MAC response.
+ * @param _init - precalculated cipher state
+ * @param nr - the reader challenge
+ * @param mac - where to store the MAC
+ * @param div_key_p - the key to use
+ */
+void opt_doTagMAC_2(State _init,  uint8_t* nr, uint8_t mac[4], const uint8_t* div_key_p)
+{
+       static uint8_t _nr [4];
+       opt_reverse_arraybytecpy(_nr, nr, 4);
+       opt_suc(div_key_p,&_init,_nr, 4, true);
+       //opt_suc(div_key_p,&_init,nr, 4, false);
+       uint8_t dest []= {0,0,0,0};
+       opt_output(div_key_p,&_init, dest);
        //The output MAC must also be reversed
-       opt_reverse_arraybytecpy(mac, dest,12);
+       opt_reverse_arraybytecpy(mac, dest,4);
        return;
 }