Fix security risk, Fix bug when overriding a key

main.c

@@ -5,6 +5,7 @@
 #include <string.h>
 #include <sys/types.h>
 #include <time.h>
+#include <stdbool.h>
 
 #define WORD 32
 #define TRANSFORM_TABLE_MAX_RAND 4294967296
@@ -24,11 +25,12 @@
 typedef struct
 {
     char *key;
+    unsigned int keylen;
+    
     void *data;
 
     // gets set to 1 if another key, collides with this elemnts location
     u_int8_t encountered_collision;
-
     // On collision, this field stores, where in the hash table array the second key (with the same hash) is located
     int next_key_location;
 
@@ -37,12 +39,12 @@ typedef struct
 // Contains everything the functions for the hashtables need, to work with, including the hash table itself
 typedef struct
 {
+    // stores a transformation table used by the shash_hash function
     unsigned int *transformation_table;
     shash_table_element_t *hash_table;
     unsigned int table_size;
 } shash_hashtable_t;
 
-// Returns -1 when the hashtable is full
 int get_empty_hashtable_slot(shash_hashtable_t *hashtable)
 {
     assert(hashtable != NULL);
@@ -58,7 +60,7 @@ int get_empty_hashtable_slot(shash_hashtable_t *hashtable)
 
 int shash_init_hashtable(shash_hashtable_t *hashtable, unsigned int table_size)
 {
-    // Initialize the RNG to a non-constant value, to make the output less pseudo random
+    // Initialize the RNG to a non-constant seed, to make the output less pseudo random
     srand(time(NULL));
 
     // Create a transformation table
@@ -104,6 +106,20 @@ unsigned int shash_hash(char *key, unsigned int len, shash_hashtable_t *hashtabl
     return hash_word % hashtable->table_size;
 }
 
+static bool is_key_in_slot(shash_table_element_t slot, char *key, unsigned int len)
+{
+    if(slot.keylen != len)
+    {
+	return 0;
+    }
+    unsigned int longer_key_lenght = slot.keylen > len ? slot.keylen : len;
+    if(strncmp(slot.key, key, longer_key_lenght) == 0)
+    {
+	return true;
+    }
+    return false;
+}
+
 int shash_set(char *key, unsigned int len, void *data, shash_hashtable_t *hashtable)
 {
     assert(key != NULL);
@@ -111,9 +127,9 @@ int shash_set(char *key, unsigned int len, void *data, shash_hashtable_t *hashta
     assert(hashtable != NULL);
 
     unsigned int slot = shash_hash(key, len, hashtable);
-
+    
     // Loop to the end of the linked list
-    while (hashtable->hash_table[slot].encountered_collision != 0 && strcmp(hashtable->hash_table[slot].key, key) != 0)
+    while (hashtable->hash_table[slot].encountered_collision != 0 && !is_key_in_slot(hashtable->hash_table[slot], key, len))
     {
         slot = hashtable->hash_table[slot].next_key_location;
     }
@@ -121,10 +137,11 @@ int shash_set(char *key, unsigned int len, void *data, shash_hashtable_t *hashta
     shash_table_element_t table_element =
         {
             .key = strndup(key, len),
+	    .keylen = len,
             .data = data};
 
     // If there is no element already in the slot, we can just use it
-    if (hashtable->hash_table[slot].key == 0)
+    if (hashtable->hash_table[slot].key == 0 || is_key_in_slot(hashtable->hash_table[slot], key, len))
     {
         hashtable->hash_table[slot] = table_element;
         return EXIT_SUCCESS;
@@ -153,7 +170,7 @@ void *shash_get(char *key, unsigned int len, shash_hashtable_t *hashtable)
     unsigned int slot = shash_hash(key, len, hashtable);
 
     // Itereate through the link list until we find the right element
-    while (strcmp(hashtable->hash_table[slot].key, key) != 0)
+    while (!is_key_in_slot(hashtable->hash_table[slot], key, len))
     {
         if (hashtable->hash_table[slot].encountered_collision == 1)
         {