enowars5-service-stldoctor

commit d296a0c73787537ad9ea087f213083f29fbd6f8f
parent ced5bcb273a17a31058dd58ab413f7c83cfe4508
Author: Louis Burda <quent.burda@gmail.com>
Date:   Mon, 31 May 2021 21:29:50 +0200

fix bug in revhash that generated false preimages

Diffstat:
M
checker/src/revhash/main.c
 | 
36
++++++++++++++++++++++--------------

1 file changed, 22 insertions(+), 14 deletions(-)
diff --git a/checker/src/revhash/main.c b/checker/src/revhash/main.c
@@ -9,18 +9,12 @@
 #define MIN(x,y)  ((x) < (y) ? (x) : (y))
 
 int
-hash()
+mhash(const char *str, size_t len)
 {
 	static char buf[MHASHLEN + 1];
-	char str[256];
 	int i, k, v;
 	char c, *bp;
-	size_t len;
-
-	if (!fgets(str, sizeof(str), stdin))
-		return EXIT_FAILURE;
 
-	len = strlen(str) -1;
 	if (len <= 0) return EXIT_FAILURE;
 
 	for (v = 0, i = 0; i < len; i++) v += str[i];
@@ -35,19 +29,26 @@ hash()
 }
 
 int
+hash()
+{
+	char str[256];
+	size_t len;
+
+	if (!fgets(str, sizeof(str), stdin))
+		return EXIT_FAILURE;
+
+	return mhash(str, strlen(str) - 1);
+}
+
+int
 revhash(const char *hashstr)
 {
-	char c, hexbuf[3] = { 0 }, *end, *buf;
-	int i, k, v, maxlen, sum, *hash, sublen, aftersum;
+	char c, hexbuf[3] = { 0 }, *end, buf[256];
+	int i, k, v, maxlen, sum, hash[256], sublen, aftersum;
 
 	if (strlen(hashstr) % 2 != 0)
 		goto invalid;
-
-	/* alloc */
 	maxlen = strlen(hashstr) / 2;
-	hash = calloc(maxlen, sizeof(int));
-	buf = malloc(strlen(hashstr));
-	if (!hash) return EXIT_FAILURE;
 
 	/* convert hex to int array */
 	for (i = 0; i < maxlen; i++) {
@@ -74,6 +75,8 @@ revhash(const char *hashstr)
 				buf[k] = (char) hash[k] ^ (rand() % 256);
 				if (buf[k] < 0 || buf[k] != buf[k % sublen]) break;
 			}
+		} else {
+			sublen = maxlen;
 		}
 
 		if (k < maxlen) continue;
@@ -86,9 +89,14 @@ revhash(const char *hashstr)
 			c = MIN(127, sum);
 			printf("%c", c);
 			sum -= c;
+			buf[k++] = c;
 		}
 
 		printf("\n");
+
+		if (getenv("OUTPUT_HASH"))
+			mhash(buf, k);
+
 		return EXIT_SUCCESS;
 	}