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1 //-----------------------------------------------------------------------------
2 // (c) 2009 Henryk Plötz <henryk@ploetzli.ch>
3 //
4 // This code is licensed to you under the terms of the GNU GPL, version 2 or,
5 // at your option, any later version. See the LICENSE.txt file for the text of
6 // the license.
7 //-----------------------------------------------------------------------------
8 // Hitag2 emulation
9 //
10 // Contains state and functions for an emulated Hitag2 tag. Offers an entry
11 // point to handle commands, needs a callback to send response.
12 //-----------------------------------------------------------------------------
13
14 #include "proxmark3.h"
15 #include "apps.h"
16 #include "util.h"
17 #include "hitag2.h"
18 #include "string.h"
19
20 struct hitag2_cipher_state {
21 uint64_t state;
22 };
23
24 struct hitag2_tag {
25 uint32_t uid;
26 enum {
27 TAG_STATE_RESET, // Just powered up, awaiting GetSnr
28 TAG_STATE_ACTIVATING, // In activation phase (password mode), sent UID, awaiting reader password
29 TAG_STATE_AUTHENTICATING, // In activation phase (crypto mode), awaiting reader authentication
30 TAG_STATE_ACTIVATED, // Activation complete, awaiting read/write commands
31 TAG_STATE_WRITING, // In write command, awaiting sector contents to be written
32 } state;
33 unsigned int active_sector;
34 char crypto_active;
35 struct hitag2_cipher_state cs;
36 char sectors[8][4];
37 };
38
39 static void hitag2_cipher_reset(struct hitag2_tag *tag, const char *challenge);
40 static int hitag2_cipher_authenticate(struct hitag2_cipher_state *cs, const char *authenticator);
41 static int hitag2_cipher_transcrypt(struct hitag2_cipher_state *cs, char *data, unsigned int bytes, unsigned int bits);
42
43 static struct hitag2_tag tag;
44 static const struct hitag2_tag resetdata = {
45 .state = TAG_STATE_RESET,
46 .sectors = { // Password mode: | Crypto mode:
47 [0] = { 0x35, 0x33, 0x70, 0x11}, // UID | UID
48 [1] = { 0x4d, 0x49, 0x4b, 0x52}, // Password RWD | 32 bit LSB key
49 [2] = { 0x20, 0xf0, 0x4f, 0x4e}, // Reserved | 16 bit MSB key, 16 bit reserved
50 [3] = { 0x0e, 0xaa, 'H', 'T'}, // Configuration, password TAG | Configuration, password TAG
51 },
52 };
53
54 int hitag2_reset(void)
55 {
56 tag.state = TAG_STATE_RESET;
57 tag.crypto_active = 0;
58 return 0;
59 }
60
61 int hitag2_init(void)
62 {
63 memcpy(&tag, &resetdata, sizeof(tag));
64 hitag2_reset();
65 return 0;
66 }
67
68 int hitag2_handle_command(const char* data, const int length, hitag2_response_callback_t cb, void *cb_cookie)
69 {
70 (void)data; (void)length; (void)cb; (void)cb_cookie;
71 int retry = 0, done = 0, result=0;
72 char temp[10];
73
74 if(tag.crypto_active && length < sizeof(temp)*8) {
75 /* Decrypt command */
76 memcpy(temp, data, (length+7)/8);
77 hitag2_cipher_transcrypt(&(tag.cs), temp, length/8, length%8);
78 data = temp;
79 }
80
81
82 handle_command_retry:
83 switch(tag.state) {
84 case TAG_STATE_RESET:
85 if(length == 5 && data[0] == 0xC0) {
86 /* Received 11000 from the reader, request for UID, send UID */
87 result=cb(tag.sectors[0], sizeof(tag.sectors[0])*8, 208, cb_cookie);
88 done=1;
89 if(tag.sectors[3][0] & 0x08) {
90 tag.state=TAG_STATE_AUTHENTICATING;
91 } else {
92 tag.state=TAG_STATE_ACTIVATING;
93 }
94 }
95 break;
96 case TAG_STATE_ACTIVATING:
97 if(length == 0x20) {
98 /* Received RWD password, respond with configuration and our password */
99 result=cb(tag.sectors[3], sizeof(tag.sectors[3])*8, 208, cb_cookie);
100 done=1;
101 tag.state=TAG_STATE_ACTIVATED;
102 }
103 break;
104 case TAG_STATE_AUTHENTICATING:
105 if(length == 0x40) {
106 /* Received initialisation vector || authentication token, fire up cipher, send our password */
107 hitag2_cipher_reset(&tag, data);
108 if(hitag2_cipher_authenticate(&(tag.cs), data+4)) {
109 char response_enc[4];
110 memcpy(response_enc, tag.sectors[3], 4);
111 hitag2_cipher_transcrypt(&(tag.cs), response_enc, 4, 0);
112 result=cb(response_enc, 4*8, 208, cb_cookie);
113 done=1;
114 tag.crypto_active = 1;
115 tag.state = TAG_STATE_ACTIVATED;
116 } else {
117 /* The reader failed to authenticate, do nothing */
118 DbpString("Reader authentication failed");
119 }
120 }
121 break;
122 case TAG_STATE_ACTIVATED:
123 if(length == 10) {
124 if( ((data[0] & 0xC0) == 0xC0) && ((data[0] & 0x06) == 0) ) {
125 /* Read command: 11xx x00y yy with yyy == ~xxx, xxx is sector number */
126 unsigned int sector = (~( ((data[0]<<2)&0x04) | ((data[1]>>6)&0x03) ) & 0x07);
127 if(sector == ( (data[0]>>3)&0x07 ) ) {
128 memcpy(temp, tag.sectors[sector], 4);
129 if(tag.crypto_active) {
130 hitag2_cipher_transcrypt(&(tag.cs), temp, 4, 0);
131 }
132 /* Respond with contents of sector sector */
133 result = cb(temp, 4*8, 208, cb_cookie);
134 done=1;
135 } else {
136 /* transmission error */
137 DbpString("Transmission error (read) in activated state");
138 }
139 } else if( ((data[0] & 0xC0) == 0x80) && ((data[0] & 0x06) == 2) ) {
140 /* Write command: 10xx x01y yy with yyy == ~xxx, xxx is sector number */
141 unsigned int sector = (~( ((data[0]<<2)&0x04) | ((data[1]>>6)&0x03) ) & 0x07);
142 if(sector == ( (data[0]>>3)&0x07 ) ) {
143 /* Prepare write, acknowledge by repeating command */
144 if(tag.crypto_active) {
145 hitag2_cipher_transcrypt(&(tag.cs), temp, length/8, length%8);
146 }
147 result = cb(data, length, 208, cb_cookie);
148 done=1;
149 tag.active_sector = sector;
150 tag.state=TAG_STATE_WRITING;
151 } else {
152 /* transmission error */
153 DbpString("Transmission error (write) in activated state");
154 }
155 }
156
157 }
158 case TAG_STATE_WRITING:
159 if(length == 32) {
160 /* These are the sector contents to be written. We don't have to do anything else. */
161 memcpy(tag.sectors[tag.active_sector], data, length/8);
162 tag.state=TAG_STATE_ACTIVATED;
163 done=1;
164 }
165 }
166
167 if(!done && !retry) {
168 /* We didn't respond, maybe our state is faulty. Reset and try again. */
169 retry=1;
170 if(tag.crypto_active) {
171 /* Restore undeciphered data */
172 memcpy(temp, data, (length+7)/8);
173 }
174 hitag2_reset();
175 goto handle_command_retry;
176 }
177
178 return result;
179 }
180
181 /* Following is a modified version of cryptolib.com/ciphers/hitag2/ */
182 // Software optimized 48-bit Philips/NXP Mifare Hitag2 PCF7936/46/47/52 stream cipher algorithm by I.C. Wiener 2006-2007.
183 // For educational purposes only.
184 // No warranties or guarantees of any kind.
185 // This code is released into the public domain by its author.
186
187 // Basic macros:
188
189 #define u8 uint8_t
190 #define u32 uint32_t
191 #define u64 uint64_t
192 #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))
193 #define rev16(x) (rev8 (x)+(rev8 (x>> 8)<< 8))
194 #define rev32(x) (rev16(x)+(rev16(x>>16)<<16))
195 #define rev64(x) (rev32(x)+(rev32(x>>32)<<32))
196 #define bit(x,n) (((x)>>(n))&1)
197 #define bit32(x,n) ((((x)[(n)>>5])>>((n)))&1)
198 #define inv32(x,i,n) ((x)[(i)>>5]^=((u32)(n))<<((i)&31))
199 #define rotl64(x, n) ((((u64)(x))<<((n)&63))+(((u64)(x))>>((0-(n))&63)))
200
201 // Single bit Hitag2 functions:
202
203 #define i4(x,a,b,c,d) ((u32)((((x)>>(a))&1)+(((x)>>(b))&1)*2+(((x)>>(c))&1)*4+(((x)>>(d))&1)*8))
204
205 static const u32 ht2_f4a = 0x2C79; // 0010 1100 0111 1001
206 static const u32 ht2_f4b = 0x6671; // 0110 0110 0111 0001
207 static const u32 ht2_f5c = 0x7907287B; // 0111 1001 0000 0111 0010 1000 0111 1011
208
209 static u32 _f20 (const u64 x)
210 {
211 u32 i5;
212
213 i5 = ((ht2_f4a >> i4 (x, 1, 2, 4, 5)) & 1)* 1
214 + ((ht2_f4b >> i4 (x, 7,11,13,14)) & 1)* 2
215 + ((ht2_f4b >> i4 (x,16,20,22,25)) & 1)* 4
216 + ((ht2_f4b >> i4 (x,27,28,30,32)) & 1)* 8
217 + ((ht2_f4a >> i4 (x,33,42,43,45)) & 1)*16;
218
219 return (ht2_f5c >> i5) & 1;
220 }
221
222 static u64 _hitag2_init (const u64 key, const u32 serial, const u32 IV)
223 {
224 u32 i;
225 u64 x = ((key & 0xFFFF) << 32) + serial;
226
227 for (i = 0; i < 32; i++)
228 {
229 x >>= 1;
230 x += (u64) (_f20 (x) ^ (((IV >> i) ^ (key >> (i+16))) & 1)) << 47;
231 }
232 return x;
233 }
234
235 static u64 _hitag2_round (u64 *state)
236 {
237 u64 x = *state;
238
239 x = (x >> 1) +
240 ((((x >> 0) ^ (x >> 2) ^ (x >> 3) ^ (x >> 6)
241 ^ (x >> 7) ^ (x >> 8) ^ (x >> 16) ^ (x >> 22)
242 ^ (x >> 23) ^ (x >> 26) ^ (x >> 30) ^ (x >> 41)
243 ^ (x >> 42) ^ (x >> 43) ^ (x >> 46) ^ (x >> 47)) & 1) << 47);
244
245 *state = x;
246 return _f20 (x);
247 }
248
249 static u32 _hitag2_byte (u64 * x)
250 {
251 u32 i, c;
252
253 for (i = 0, c = 0; i < 8; i++) c += (u32) _hitag2_round (x) << (i^7);
254 return c;
255 }
256
257
258 /* Cipher/tag glue code: */
259
260 static void hitag2_cipher_reset(struct hitag2_tag *tag, const char *iv)
261 {
262 uint64_t key = ((uint64_t)tag->sectors[2][2]) |
263 ((uint64_t)tag->sectors[2][3] << 8) |
264 ((uint64_t)tag->sectors[1][0] << 16) |
265 ((uint64_t)tag->sectors[1][1] << 24) |
266 ((uint64_t)tag->sectors[1][2] << 32) |
267 ((uint64_t)tag->sectors[1][3] << 40);
268 uint32_t uid = ((uint32_t)tag->sectors[0][0]) |
269 ((uint32_t)tag->sectors[0][1] << 8) |
270 ((uint32_t)tag->sectors[0][2] << 16) |
271 ((uint32_t)tag->sectors[0][3] << 24);
272 uint32_t iv_ = (((uint32_t)(iv[0]))) |
273 (((uint32_t)(iv[1])) << 8) |
274 (((uint32_t)(iv[2])) << 16) |
275 (((uint32_t)(iv[3])) << 24);
276 tag->cs.state = _hitag2_init(rev64(key), rev32(uid), rev32(iv_));
277 }
278
279 static int hitag2_cipher_authenticate(struct hitag2_cipher_state *cs, const char *authenticator_is)
280 {
281 char authenticator_should[4];
282 authenticator_should[0] = ~_hitag2_byte(&(cs->state));
283 authenticator_should[1] = ~_hitag2_byte(&(cs->state));
284 authenticator_should[2] = ~_hitag2_byte(&(cs->state));
285 authenticator_should[3] = ~_hitag2_byte(&(cs->state));
286 return memcmp(authenticator_should, authenticator_is, 4) == 0;
287 }
288
289 static int hitag2_cipher_transcrypt(struct hitag2_cipher_state *cs, char *data, unsigned int bytes, unsigned int bits)
290 {
291 int i;
292 for(i=0; i<bytes; i++) data[i] ^= _hitag2_byte(&(cs->state));
293 for(i=0; i<bits; i++) data[bytes] ^= _hitag2_round(&(cs->state)) << (7-i);
294 return 0;
295 }
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