git.zerfleddert.de Git - proxmark3-svn/blob - armsrc/hitag2.c

   1 /*
   2  * Hitag2 emulation
   3  *
   4  * Contains state and functions for an emulated Hitag2 tag. Offers an entry
   5  * point to handle commands, needs a callback to send response.
   6  *
   7  * (c) 2009 Henryk Plötz <henryk@ploetzli.ch>
   8  */
   9
  10 #include "proxmark3.h"
  11 #include "apps.h"
  12 #include "util.h"
  13 #include "hitag2.h"
  14 #include "string.h"
  15
  16 struct hitag2_cipher_state {
  17         uint64_t state;
  18 };
  19
  20 struct hitag2_tag {
  21         uint32_t uid;
  22         enum {
  23                 TAG_STATE_RESET,          // Just powered up, awaiting GetSnr
  24                 TAG_STATE_ACTIVATING,     // In activation phase (password mode), sent UID, awaiting reader password
  25                 TAG_STATE_AUTHENTICATING, // In activation phase (crypto mode), awaiting reader authentication
  26                 TAG_STATE_ACTIVATED,      // Activation complete, awaiting read/write commands
  27                 TAG_STATE_WRITING,        // In write command, awaiting sector contents to be written
  28         } state;
  29         unsigned int active_sector;
  30         char crypto_active;
  31         struct hitag2_cipher_state cs;
  32         char sectors[8][4];
  33 };
  34
  35 static void hitag2_cipher_reset(struct hitag2_tag *tag, const char *challenge);
  36 static int hitag2_cipher_authenticate(struct hitag2_cipher_state *cs, const char *authenticator);
  37 static int hitag2_cipher_transcrypt(struct hitag2_cipher_state *cs, char *data, unsigned int bytes, unsigned int bits);
  38
  39 static struct hitag2_tag tag;
  40 static const struct hitag2_tag resetdata = {
  41                 .state = TAG_STATE_RESET,
  42                 .sectors = {                                     // Password mode:               | Crypto mode:
  43                                 [0] = { 0x35, 0x33, 0x70, 0x11}, // UID                          | UID
  44                                 [1] = { 0x4d, 0x49, 0x4b, 0x52}, // Password RWD                 | 32 bit LSB key
  45                                 [2] = { 0x20, 0xf0, 0x4f, 0x4e}, // Reserved                     | 16 bit MSB key, 16 bit reserved
  46                                 [3] = { 0x0e, 0xaa, 'H', 'T'},   // Configuration, password TAG  | Configuration, password TAG
  47                 },
  48 };
  49
  50 int hitag2_reset(void)
  51 {
  52         tag.state = TAG_STATE_RESET;
  53         tag.crypto_active = 0;
  54         return 0;
  55 }
  56
  57 int hitag2_init(void)
  58 {
  59         memcpy(&tag, &resetdata, sizeof(tag));
  60         hitag2_reset();
  61         return 0;
  62 }
  63
  64 int hitag2_handle_command(const char* data, const int length, hitag2_response_callback_t cb, void *cb_cookie)
  65 {
  66         (void)data; (void)length; (void)cb; (void)cb_cookie;
  67         int retry = 0, done = 0, result=0;
  68         char temp[10];
  69
  70         if(tag.crypto_active && length < sizeof(temp)*8) {
  71                 /* Decrypt command */
  72                 memcpy(temp, data, (length+7)/8);
  73                 hitag2_cipher_transcrypt(&(tag.cs), temp, length/8, length%8);
  74                 data = temp;
  75         }
  76
  77
  78 handle_command_retry:
  79         switch(tag.state) {
  80         case TAG_STATE_RESET:
  81                 if(length == 5 && data[0] == 0xC0) {
  82                         /* Received 11000 from the reader, request for UID, send UID */
  83                         result=cb(tag.sectors[0], sizeof(tag.sectors[0])*8, 208, cb_cookie);
  84                         done=1;
  85                         if(tag.sectors[3][0] & 0x08) {
  86                                 tag.state=TAG_STATE_AUTHENTICATING;
  87                         } else {
  88                                 tag.state=TAG_STATE_ACTIVATING;
  89                         }
  90                 }
  91                 break;
  92         case TAG_STATE_ACTIVATING:
  93                 if(length == 0x20) {
  94                         /* Received RWD password, respond with configuration and our password */
  95                         result=cb(tag.sectors[3], sizeof(tag.sectors[3])*8, 208, cb_cookie);
  96                         done=1;
  97                         tag.state=TAG_STATE_ACTIVATED;
  98                 }
  99                 break;
 100         case TAG_STATE_AUTHENTICATING:
 101                 if(length == 0x40) {
 102                         /* Received initialisation vector || authentication token, fire up cipher, send our password */
 103                         hitag2_cipher_reset(&tag, data);
 104                         if(hitag2_cipher_authenticate(&(tag.cs), data+4)) {
 105                                 char response_enc[4];
 106                                 memcpy(response_enc, tag.sectors[3], 4);
 107                                 hitag2_cipher_transcrypt(&(tag.cs), response_enc, 4, 0);
 108                                 result=cb(response_enc, 4*8, 208, cb_cookie);
 109                                 done=1;
 110                                 tag.crypto_active = 1;
 111                                 tag.state = TAG_STATE_ACTIVATED;
 112                         } else {
 113                                 /* The reader failed to authenticate, do nothing */
 114                                 DbpString("Reader authentication failed");
 115                         }
 116                 }
 117                 break;
 118         case TAG_STATE_ACTIVATED:
 119                 if(length == 10) {
 120                         if( ((data[0] & 0xC0) == 0xC0) && ((data[0] & 0x06) == 0) ) {
 121                                 /* Read command: 11xx x00y  yy with yyy == ~xxx, xxx is sector number */
 122                                 unsigned int sector = (~( ((data[0]<<2)&0x04) | ((data[1]>>6)&0x03) ) & 0x07);
 123                                 if(sector == ( (data[0]>>3)&0x07 ) ) {
 124                                         memcpy(temp, tag.sectors[sector], 4);
 125                                         if(tag.crypto_active) {
 126                                                 hitag2_cipher_transcrypt(&(tag.cs), temp, 4, 0);
 127                                         }
 128                                         /* Respond with contents of sector sector */
 129                                         result = cb(temp, 4*8, 208, cb_cookie);
 130                                         done=1;
 131                                 } else {
 132                                         /* transmission error */
 133                                         DbpString("Transmission error (read) in activated state");
 134                                 }
 135                         } else if( ((data[0] & 0xC0) == 0x80) && ((data[0] & 0x06) == 2) ) {
 136                                 /* Write command: 10xx x01y  yy with yyy == ~xxx, xxx is sector number */
 137                                 unsigned int sector = (~( ((data[0]<<2)&0x04) | ((data[1]>>6)&0x03) ) & 0x07);
 138                                 if(sector == ( (data[0]>>3)&0x07 ) ) {
 139                                         /* Prepare write, acknowledge by repeating command */
 140                                         if(tag.crypto_active) {
 141                                                 hitag2_cipher_transcrypt(&(tag.cs), temp, length/8, length%8);
 142                                         }
 143                                         result = cb(data, length, 208, cb_cookie);
 144                                         done=1;
 145                                         tag.active_sector = sector;
 146                                         tag.state=TAG_STATE_WRITING;
 147                                 } else {
 148                                         /* transmission error */
 149                                         DbpString("Transmission error (write) in activated state");
 150                                 }
 151                         }
 152
 153                 }
 154         case TAG_STATE_WRITING:
 155                 if(length == 32) {
 156                         /* These are the sector contents to be written. We don't have to do anything else. */
 157                         memcpy(tag.sectors[tag.active_sector], data, length/8);
 158                         tag.state=TAG_STATE_ACTIVATED;
 159                         done=1;
 160                 }
 161         }
 162
 163         if(!done && !retry) {
 164                 /* We didn't respond, maybe our state is faulty. Reset and try again. */
 165                 retry=1;
 166                 if(tag.crypto_active) {
 167                         /* Restore undeciphered data */
 168                         memcpy(temp, data, (length+7)/8);
 169                 }
 170                 hitag2_reset();
 171                 goto handle_command_retry;
 172         }
 173
 174         return result;
 175 }
 176
 177 /* Following is a modified version of cryptolib.com/ciphers/hitag2/ */
 178 // Software optimized 48-bit Philips/NXP Mifare Hitag2 PCF7936/46/47/52 stream cipher algorithm by I.C. Wiener 2006-2007.
 179 // For educational purposes only.
 180 // No warranties or guarantees of any kind.
 181 // This code is released into the public domain by its author.
 182
 183 // Basic macros:
 184
 185 #define u8                              uint8_t
 186 #define u32                             uint32_t
 187 #define u64                             uint64_t
 188 #define rev8(x)                 ((((x)>>7)&1)+((((x)>>6)&1)<<1)+((((x)>>5)&1)<<2)+((((x)>>4)&1)<<3)+((((x)>>3)&1)<<4)+((((x)>>2)&1)<<5)+((((x)>>1)&1)<<6)+(((x)&1)<<7))
 189 #define rev16(x)                (rev8 (x)+(rev8 (x>> 8)<< 8))
 190 #define rev32(x)                (rev16(x)+(rev16(x>>16)<<16))
 191 #define rev64(x)                (rev32(x)+(rev32(x>>32)<<32))
 192 #define bit(x,n)                (((x)>>(n))&1)
 193 #define bit32(x,n)              ((((x)[(n)>>5])>>((n)))&1)
 194 #define inv32(x,i,n)    ((x)[(i)>>5]^=((u32)(n))<<((i)&31))
 195 #define rotl64(x, n)    ((((u64)(x))<<((n)&63))+(((u64)(x))>>((0-(n))&63)))
 196
 197 // Single bit Hitag2 functions:
 198
 199 #define i4(x,a,b,c,d)   ((u32)((((x)>>(a))&1)+(((x)>>(b))&1)*2+(((x)>>(c))&1)*4+(((x)>>(d))&1)*8))
 200
 201 static const u32 ht2_f4a = 0x2C79;              // 0010 1100 0111 1001
 202 static const u32 ht2_f4b = 0x6671;              // 0110 0110 0111 0001
 203 static const u32 ht2_f5c = 0x7907287B;  // 0111 1001 0000 0111 0010 1000 0111 1011
 204
 205 static u32 _f20 (const u64 x)
 206 {
 207         u32                                     i5;
 208
 209         i5 = ((ht2_f4a >> i4 (x, 1, 2, 4, 5)) & 1)* 1
 210            + ((ht2_f4b >> i4 (x, 7,11,13,14)) & 1)* 2
 211            + ((ht2_f4b >> i4 (x,16,20,22,25)) & 1)* 4
 212            + ((ht2_f4b >> i4 (x,27,28,30,32)) & 1)* 8
 213            + ((ht2_f4a >> i4 (x,33,42,43,45)) & 1)*16;
 214
 215         return (ht2_f5c >> i5) & 1;
 216 }
 217
 218 static u64 _hitag2_init (const u64 key, const u32 serial, const u32 IV)
 219 {
 220         u32                                     i;
 221         u64                                     x = ((key & 0xFFFF) << 32) + serial;
 222
 223         for (i = 0; i < 32; i++)
 224         {
 225                 x >>= 1;
 226                 x += (u64) (_f20 (x) ^ (((IV >> i) ^ (key >> (i+16))) & 1)) << 47;
 227         }
 228         return x;
 229 }
 230
 231 static u64 _hitag2_round (u64 *state)
 232 {
 233         u64                                     x = *state;
 234
 235         x = (x >>  1) +
 236          ((((x >>  0) ^ (x >>  2) ^ (x >>  3) ^ (x >>  6)
 237           ^ (x >>  7) ^ (x >>  8) ^ (x >> 16) ^ (x >> 22)
 238           ^ (x >> 23) ^ (x >> 26) ^ (x >> 30) ^ (x >> 41)
 239           ^ (x >> 42) ^ (x >> 43) ^ (x >> 46) ^ (x >> 47)) & 1) << 47);
 240
 241         *state = x;
 242         return _f20 (x);
 243 }
 244
 245 static u32 _hitag2_byte (u64 * x)
 246 {
 247         u32                                     i, c;
 248
 249         for (i = 0, c = 0; i < 8; i++) c += (u32) _hitag2_round (x) << (i^7);
 250         return c;
 251 }
 252
 253
 254 /* Cipher/tag glue code: */
 255
 256 static void hitag2_cipher_reset(struct hitag2_tag *tag, const char *iv)
 257 {
 258         uint64_t key = ((uint64_t)tag->sectors[2][2]) |
 259                         ((uint64_t)tag->sectors[2][3] << 8) |
 260                         ((uint64_t)tag->sectors[1][0] << 16) |
 261                         ((uint64_t)tag->sectors[1][1] << 24) |
 262                         ((uint64_t)tag->sectors[1][2] << 32) |
 263                         ((uint64_t)tag->sectors[1][3] << 40);
 264         uint32_t uid = ((uint32_t)tag->sectors[0][0]) |
 265                         ((uint32_t)tag->sectors[0][1] << 8) |
 266                         ((uint32_t)tag->sectors[0][2] << 16) |
 267                         ((uint32_t)tag->sectors[0][3] << 24);
 268         uint32_t iv_ = (((uint32_t)(iv[0]))) |
 269                         (((uint32_t)(iv[1])) << 8) |
 270                         (((uint32_t)(iv[2])) << 16) |
 271                         (((uint32_t)(iv[3])) << 24);
 272         tag->cs.state = _hitag2_init(rev64(key), rev32(uid), rev32(iv_));
 273 }
 274
 275 static int hitag2_cipher_authenticate(struct hitag2_cipher_state *cs, const char *authenticator_is)
 276 {
 277         char authenticator_should[4];
 278         authenticator_should[0] = ~_hitag2_byte(&(cs->state));
 279         authenticator_should[1] = ~_hitag2_byte(&(cs->state));
 280         authenticator_should[2] = ~_hitag2_byte(&(cs->state));
 281         authenticator_should[3] = ~_hitag2_byte(&(cs->state));
 282         return memcmp(authenticator_should, authenticator_is, 4) == 0;
 283 }
 284
 285 static int hitag2_cipher_transcrypt(struct hitag2_cipher_state *cs, char *data, unsigned int bytes, unsigned int bits)
 286 {
 287         int i;
 288         for(i=0; i<bytes; i++) data[i] ^= _hitag2_byte(&(cs->state));
 289         for(i=0; i<bits; i++) data[bytes] ^= _hitag2_round(&(cs->state)) << (7-i);
 290         return 0;
 291 }