X-Git-Url: https://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/6c283951062aaad9d0d1ba8670b02895047be438..e619ddc071e882bb9de75d2e0905c4eda2b11516:/common/lfdemod.c?ds=sidebyside

diff --git a/common/lfdemod.c b/common/lfdemod.c
index 2f376e5f..f231cd69 100644
--- 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;
 }