ADD: since the client now calls legic prng, this is needed here too.

[proxmark3-svn] / common / lfdemod.c

diff --git a/common/lfdemod.c b/common/lfdemod.c
index 2f376e5f2f02438c8f4f55a3b2fdff1e11febcf6..f231cd69fd54e787506cea2cee9f4d022cf87e0a 100644 (file)
--- a/common/lfdemod.c
+++ b/common/lfdemod.c
@@ -148,8 +148,11 @@ uint32_t bytebits_to_byteLSBF(uint8_t *src, size_t numbits)
 //search for given preamble in given BitStream and return success=1 or fail=0 and startIndex and length
 uint8_t preambleSearch(uint8_t *BitStream, uint8_t *preamble, size_t pLen, size_t *size, size_t *startIdx)
 {
-       uint8_t foundCnt=0;
-       for (int idx=0; idx < *size - pLen; idx++){
+       // Sanity check.  If preamble length is bigger than bitstream length.
+       if ( *size <= pLen ) return 0;
+       
+       uint8_t foundCnt = 0;
+       for (int idx = 0; idx < *size - pLen; idx++){
                if (memcmp(BitStream+idx, preamble, pLen) == 0){
                        //first index found
                        foundCnt++;
@@ -732,21 +735,27 @@ int JablotronDemod(uint8_t *dest, size_t *size){
 
        size_t startIdx = 0;
        // 0xFFFF preamble, 64bits
-       uint8_t preamble[] = {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1};
+       uint8_t preamble[] = {
+                       1,1,1,1,
+                   1,1,1,1,
+                               1,1,1,1,
+                               1,1,1,1,
+                               0
+               };
 
        uint8_t errChk = preambleSearch(dest, preamble, sizeof(preamble), size, &startIdx);
        if (errChk == 0) return -4; //preamble not found
+       if (*size != 64) return -3;
        
-       uint8_t checkCalc = 0;
+       uint8_t checkchksum = 0;
        for (int i=16; i < 56; i += 8) {
-               checkCalc += bytebits_to_byte(dest+startIdx+i,8);
+               checkchksum += bytebits_to_byte(dest+startIdx+i,8);
        }
-       checkCalc ^= 0x3A;
+       checkchksum ^= 0x3A;
 
-       uint8_t crc = bytebits_to_byte(dest+startIdx+56,8);
+       uint8_t crc = bytebits_to_byte(dest+startIdx+56, 8);
        
-       if ( checkCalc != crc ) return -5;      
-       if (*size != 64) return -6;
+       if ( checkchksum != crc ) return -5;    
        return (int)startIdx;
 }