sbtools: add brute force option for sb1 in sbtoelf

After some reverse engineering, it appears that the keys of the
sb1 format are very weak: the 128 bytes are generated from the
laserfuse words 4,5 and 6 but in a weird manner: 4 and 5 are
simply ORed and 6 is only half used (somehow), making it "only" a
48 bit word to find.

Change-Id: I40702e19d0924ef51c01894efce3cb65bd664456

utils/imxtools/sbtools/crypto.h

@@ -125,5 +125,6 @@ void sha_1_output(struct sha_1_params_t *params, byte *out);
 // WARNING those functions modifies the keys !!
 uint32_t xor_encrypt(union xorcrypt_key_t keys[2], void *data, int size);
 uint32_t xor_decrypt(union xorcrypt_key_t keys[2], void *data, int size);
+void xor_generate_key(uint32_t laserfuse[3], union xorcrypt_key_t key[2]);
 
 #endif /* __CRYPTO_H__ */

utils/imxtools/sbtools/misc.c

@@ -117,8 +117,23 @@ bool parse_key(char **pstr, struct crypto_key_t *key)
     while(isspace(*str))
         str++;
     /* CRYPTO_KEY: 32 hex characters
-     * CRYPTO_USBOTP: usbotp(vid:pid) where vid and pid are hex numbers */
+     * CRYPTO_USBOTP: usbotp(vid:pid) where vid and pid are hex numbers
-    if(isxdigit(str[0]))
+     * CRYPTO_XOR_KEY: 256 hex characters */
+    if(isxdigit(str[0]) && strlen(str) >= 256 && isxdigit(str[32]))
+    {
+        for(int j = 0; j < 128; j++)
+        {
+            byte a, b;
+            if(convxdigit(str[2 * j], &a) || convxdigit(str[2 * j + 1], &b))
+                return false;
+            key->u.xor_key[j / 64].key[j % 64] = (a << 4) | b;
+        }
+        /* skip key */
+        *pstr = str + 256;
+        key->method = CRYPTO_XOR_KEY;
+        return true;
+    }
+    else if(isxdigit(str[0]))
     {
         if(strlen(str) < 32)
             return false;

utils/imxtools/sbtools/sb1.c

@@ -252,6 +252,109 @@ static const char *sb1_datatype_name(int cmd)
     }
 }
 
+bool sb1_is_key_valid_fast(void *buffer, size_t size, union xorcrypt_key_t _key[2])
+{
+    struct sb1_header_t *header = (struct sb1_header_t *)buffer;
+
+    union xorcrypt_key_t key[2];
+    
+    uint8_t sector[SECTOR_SIZE];
+    /* copy key and data because it's modified by the crypto code */
+    memcpy(key, _key, sizeof(key));
+    memcpy(sector, header + 1, SECTOR_SIZE - header->header_size);
+    /* try to decrypt the first sector */
+    uint32_t mark = xor_decrypt(key, sector, SECTOR_SIZE - 4 - header->header_size);
+    /* copy key again it's modified by the crypto code */
+    return mark == *(uint32_t *)&sector[SECTOR_SIZE - 4 - header->header_size];
+}
+
+bool sb1_brute_force(const char *filename, void *u, sb1_color_printf cprintf,
+    enum sb1_error_t *err, struct crypto_key_t *key)
+{
+    #define printf(c, ...) cprintf(u, false, c, __VA_ARGS__)
+    uint8_t sector[SECTOR_SIZE];
+    FILE *f = fopen(filename, "rb");
+    if(f == NULL)
+    {
+        printf("Cannot open file '%s' for reading: %m\n", filename);
+        *err = SB1_OPEN_ERROR;
+        return false;
+    }
+    if(fread(sector, sizeof(sector), 1, f) != 1)
+    {
+        printf("Cannot read file '%s': %m\n", filename);
+        *err = SB1_READ_ERROR;
+        fclose(f);
+        return false;
+    }
+    fclose(f);
+
+    printf(BLUE, "Brute forcing key...\n");
+    time_t start_time = time(NULL);
+    uint32_t laserfuse[3] = {0, 0, 0};
+    unsigned last_print = 0;
+    do
+    {
+        for(int i = 0; i < 0x10000; i++)
+        {
+            laserfuse[2] = (i & 0xff00) << 8 | (i & 0xff);
+            xor_generate_key(laserfuse, key->u.xor_key);
+            if(g_debug)
+            {
+                printf(GREEN, "Trying key");
+                printf(GREEN, "[");
+                printf(RED, "%08x", laserfuse[0]);
+                printf(GREEN, ",");
+                printf(RED, "%08x", laserfuse[1]);
+                printf(GREEN, ",");
+                printf(RED, "%08x", laserfuse[2]);
+                printf(GREEN, "]:");
+                for(int j = 0; j < 32; j++)
+                    printf(YELLOW, " %08x", key->u.xor_key[j / 16].k[j % 16]);
+            }
+            if(sb1_is_key_valid_fast(sector, SECTOR_SIZE, key->u.xor_key))
+            {
+                if(g_debug)
+                    printf(RED, " Ok\n");
+                return true;
+            }
+            else
+            {
+                if(g_debug)
+                    printf(RED, " No\n");
+            }
+        }
+        laserfuse[0]++;
+
+        if(laserfuse[0] / 1000 != last_print)
+        {
+            time_t cur_time = time(NULL);
+            float key_per_sec = laserfuse[0] / (float)(cur_time - start_time);
+            float tot = 0x1000000LL / key_per_sec;
+            time_t eta_time = start_time + tot;
+
+            printf(YELLOW, "%llu", laserfuse[0] * 0x10000LL);
+            printf(GREEN, " out of ");
+            printf(BLUE, "%llu", 0x1000000LL * 0x10000LL);
+            printf(GREEN, " tested (");
+            printf(RED, "%f%%", laserfuse[0] / (float)0x1000000LL * 100.0);
+            printf(GREEN, "), ");
+            printf(YELLOW, "%d", cur_time - start_time);
+            printf(GREEN, " seconds elapsed, ");
+            printf(BLUE, "%d", eta_time - cur_time);
+            printf(GREEN, " seconds remaining, [");
+            printf(RED, "%f", key_per_sec);
+            printf(GREEN, " keys/s], ETA ");
+            printf(YELLOW, "%s", ctime(&eta_time));
+            last_print = laserfuse[0] / 1000;
+        }
+    }while(laserfuse[0] != 0);
+
+    *err = SB1_NO_VALID_KEY;
+    return false;
+    #undef printf
+}
+
 struct sb1_file_t *sb1_read_memory(void *_buf, size_t filesize, void *u,
     sb1_color_printf cprintf, enum sb1_error_t *err)
 {

utils/imxtools/sbtools/sb1.h

@@ -154,6 +154,11 @@ struct sb1_file_t *sb1_read_file_ex(const char *filename, size_t offset, size_t
 struct sb1_file_t *sb1_read_memory(void *buffer, size_t size, void *u,
     sb1_color_printf printf, enum sb1_error_t *err);
 
+/* do as little checks as possible, make sure the image is valid (advance use only) */
+bool sb1_is_key_valid_fast(void *buffer, size_t size, union xorcrypt_key_t key[2]);
+bool sb1_brute_force(const char *filename, void *u, sb1_color_printf printf,
+    enum sb1_error_t *err, struct crypto_key_t *key);
+
 void sb1_get_default_key(struct crypto_key_t *key);
 
 void sb1_dump(struct sb1_file_t *file, void *u, sb1_color_printf printf);

utils/imxtools/sbtools/sbtoelf.c

@@ -231,6 +231,7 @@ static void usage(void)
     printf("  -2/--v2\tForce to read file as a version 2 file\n");
     printf("  -s/--no-simpl\tPrevent elf files from being simplified*\n");
     printf("  -x\t\tUse default sb1 key\n");
+    printf("  -b\tBrute force key\n");
     printf("Options marked with a * are for debug purpose only\n");
     exit(1);
 }
@@ -308,6 +309,7 @@ int main(int argc, char **argv)
     const char *loopback = NULL;
     bool force_sb1 = false;
     bool force_sb2 = false;
+    bool brute_force = false;
 
     while(1)
     {
@@ -325,7 +327,7 @@ int main(int argc, char **argv)
             {0, 0, 0, 0}
         };
 
-        int c = getopt_long(argc, argv, "?do:k:zra:nl:f12xs", long_options, NULL);
+        int c = getopt_long(argc, argv, "?do:k:zra:nl:f12xsb", long_options, NULL);
         if(c == -1)
             break;
         switch(c)
@@ -391,6 +393,9 @@ int main(int argc, char **argv)
             case 's':
                 g_elf_simplify = false;
                 break;
+            case 'b':
+                brute_force = true;
+                break;
             default:
                 abort();
         }
@@ -442,6 +447,33 @@ int main(int argc, char **argv)
     }
     else if(force_sb1 || ver == SB_VERSION_1)
     {
+        if(brute_force)
+        {
+            struct crypto_key_t key;
+            enum sb1_error_t err;
+            if(!sb1_brute_force(sb_filename, NULL, sb_printf, &err, &key))
+            {
+                color(OFF);
+                printf("Brute force failed: %d\n", err);
+                return 1;
+            }
+            color(RED);
+            printf("Key found:");
+            color(YELLOW);
+            for(int i = 0; i < 32; i++)
+                printf(" %08x", key.u.xor_key[i / 16].k[i % 16]);
+            color(OFF);
+            printf("\n");
+            color(RED);
+            printf("Key: ");
+            color(YELLOW);
+            for(int i = 0; i < 128; i++)
+                printf("%02x", key.u.xor_key[i / 64].key[i % 64]);
+            color(OFF);
+            printf("\n");
+            add_keys(&key, 1);
+        }
+
         enum sb1_error_t err;
         struct sb1_file_t *file = sb1_read_file(sb_filename, NULL, sb_printf, &err);
         if(file == NULL)

utils/imxtools/sbtools/xorcrypt.c

@@ -22,6 +22,42 @@
 #include <stdlib.h>
 #include "misc.h"
 
+static uint32_t g_ROM_Key_Table[256] =
+{
+    0x6B8B4567,0x327B23C6,0x643C9869,0x66334873,0x74B0DC51,0x19495CFF,0x2AE8944A,
+    0x625558EC,0x238E1F29,0x46E87CCD,0x3D1B58BA,0x507ED7AB,0x2EB141F2,0x41B71EFB,0x79E2A9E3,0x7545E146,
+    0x515F007C,0x5BD062C2,0x12200854,0x4DB127F8,0x216231B,0x1F16E9E8,0x1190CDE7,
+    0x66EF438D,0x140E0F76,0x3352255A,0x109CF92E,0xDED7263,0x7FDCC233,0x1BEFD79F,0x41A7C4C9,0x6B68079A,
+    0x4E6AFB66,0x25E45D32,0x519B500D,0x431BD7B7,0x3F2DBA31,0x7C83E458,0x257130A3,
+    0x62BBD95A,0x436C6125,0x628C895D,0x333AB105,0x721DA317,0x2443A858,0x2D1D5AE9,0x6763845E,0x75A2A8D4,
+    0x8EDBDAB,0x79838CB2,0x4353D0CD,0xB03E0C6,0x189A769B,0x54E49EB4,0x71F32454,
+    0x2CA88611,0x836C40E,0x2901D82,0x3A95F874,0x8138641,0x1E7FF521,0x7C3DBD3D,0x737B8DDC,0x6CEAF087,
+    0x22221A70,0x4516DDE9,0x3006C83E,0x614FD4A1,0x419AC241,0x5577F8E1,0x440BADFC,
+    0x5072367,0x3804823E,0x77465F01,0x7724C67E,0x5C482A97,0x2463B9EA,0x5E884ADC,0x51EAD36B,0x2D517796,
+    0x580BD78F,0x153EA438,0x3855585C,0x70A64E2A,0x6A2342EC,0x2A487CB0,0x1D4ED43B,
+    0x725A06FB,0x2CD89A32,0x57E4CCAF,0x7A6D8D3C,0x4B588F54,0x542289EC,0x6DE91B18,0x38437FDB,0x7644A45C,
+    0x32FFF902,0x684A481A,0x579478FE,0x749ABB43,0x3DC240FB,0x1BA026FA,0x79A1DEAA,
+    0x75C6C33A,0x12E685FB,0x70C6A529,0x520EEDD1,0x374A3FE6,0x4F4EF005,0x23F9C13C,0x649BB77C,0x275AC794,
+    0x39386575,0x1CF10FD8,0x180115BE,0x235BA861,0x47398C89,0x354FE9F9,0x15B5AF5C,
+    0x741226BB,0xD34B6A8,0x10233C99,0x3F6AB60F,0x61574095,0x7E0C57B1,0x77AE35EB,0x579BE4F1,0x310C50B3,
+    0x5FF87E05,0x2F305DEF,0x25A70BF7,0x1DBABF00,0x4AD084E9,0x1F48EAA1,0x1381823A,
+    0x5DB70AE5,0x100F8FCA,0x6590700B,0x15014ACB,0x5F5E7FD0,0x98A3148,0x799D0247,0x6B94764,0x42C296BD,
+    0x168E121F,0x1EBA5D23,0x661E3F1E,0x5DC79EA8,0x540A471C,0x7BD3EE7B,0x51D9C564,
+    0x613EFDC5,0xBF72B14,0x11447B73,0x42963E5A,0xA0382C5,0x8F2B15E,0x1A32234B,0x3B0FD379,0x68EB2F63,
+    0x4962813B,0x60B6DF70,0x6A5EE64,0x14330624,0x7FFFCA11,0x1A27709E,0x71EA1109,
+    0x100F59DC,0x7FB7E0AA,0x6EB5BD4,0x6F6DD9AC,0x94211F2,0x885E1B,0x76272110,0x4C04A8AF,0x1716703B,
+    0x14E17E33,0x3222E7CD,0x74DE0EE3,0x68EBC550,0x2DF6D648,0x46B7D447,0x4A2AC315,
+    0x39EE015C,0x57FC4FBB,0xCC1016F,0x43F18422,0x60EF0119,0x26F324BA,0x7F01579B,0x49DA307D,0x7055A5F5,
+    0x5FB8370B,0x50801EE1,0x488AC1A,0x5FB8011C,0x6AA78F7F,0x7672BD23,0x6FC75AF8,
+    0x6A5F7029,0x7D5E18F8,0x5F3534A4,0x73A1821B,0x7DE67713,0x555C55B5,0x3FA62ACA,0x14FCE74E,0x6A3DD3E8,
+    0x71C91298,0x9DAF632,0x53299938,0x1FBFE8E0,0x5092CA79,0x1D545C4D,0x59ADEA3D,
+    0x288F1A34,0x2A155DBC,0x1D9F6E5F,0x97E1B4E,0x51088277,0x1CA0C5FA,0x53584BCB,0x415E286C,0x7C58FD05,
+    0x23D86AAC,0x45E6D486,0x5C10FE21,0xE7FFA2B,0x3C5991AA,0x4BD8591A,0x78DF6A55,
+    0x39B7AAA2,0x2B0D8DBE,0x6C80EC70,0x379E21B5,0x69E373,0x2C27173B,0x4C9B0904,0x6AA7B75C,0x1DF029D3,
+    0x5675FF36,0x3DD15094,0x3DB012B3,0x2708C9AF,0x5B25ACE2,0x175DFCF0,0x4F97E3E4,
+    0x53B0A9E,0x34FD6B4F,0x5915FF32,0x56438D15,0x519E3149,0x2C6E4AFD,0x17A1B582,0x4DF72E4E,0x5046B5A9
+};
+
 static uint32_t do_round(union xorcrypt_key_t *key)
 {
     uint32_t k7 = key->k[7];
@@ -97,6 +133,29 @@ static void test_round(union xorcrypt_key_t keys[2])
     }
 }
 
+void xor_generate_key(uint32_t laserfuse[3], union xorcrypt_key_t key[2])
+{
+    uint16_t bitmask = 0x36c9;
+    uint8_t magic = (laserfuse[2] >> 24 | laserfuse[2] >> 16) & 0xff;
+    uint32_t magic2 = laserfuse[0] | laserfuse[1];
+    uint8_t magic3 = (laserfuse[2] >> 8 | laserfuse[2] >> 0) & 0xff;
+
+    for(int i = 0; i < 16; i++, bitmask >>= 1, magic++)
+        key[0].k[i] = (bitmask & 1) ? 0 : g_ROM_Key_Table[magic];
+    bitmask = 0x36c9;
+    for(int i = 0; i < 16; i++, bitmask >>= 1, magic++)
+        key[1].k[i] = (bitmask & 1) ? 0 : g_ROM_Key_Table[magic];
+    key[0].k[0] ^= magic2;
+    key[1].k[0] ^= magic2;
+
+#if 1
+    for(int i = 0; i < magic3 + 57; i++)
+        do_round(&key[0]);
+    for(int i = 0; i < magic3 + 57; i++)
+        do_round(&key[1]);
+#endif
+}
+
 uint32_t xor_encrypt(union xorcrypt_key_t keys[2], void *_data, int size)
 {
     if(size % 4)