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pwdgen.c
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pwdgen.c
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// pwdgen
// Filip Rokita
// www.filiprokita.com
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#include <limits.h>
#include <time.h>
#define MAX_LENGTH 1024 // set more reasonable password length limit
int main(int argc, char *argv[])
{
// check if the user provided the correct number of arguments
if (argc != 2)
{
fprintf(stderr, "Usage: %s <length>\n", argv[0]);
return 1;
}
// save argv[1] as a string
char *input = argv[1];
// check if the user provided a number
for (int i = 0, len = strlen(input); i < len; i++)
{
if (!isdigit(input[i]))
{
fprintf(stderr, "Error: Only numbers may be provided\n");
return 1;
}
}
// convert the string to an integer safely
char *endptr;
long length = strtol(input, &endptr, 10); // fixed: more secure integer conversion
// check if the conversion was successful
if (*endptr != '\0' || length <= 0 || length > MAX_LENGTH)
{
fprintf(stderr, "Error: Invalid length. Please provide a number between 1 and %d\n", MAX_LENGTH);
return 1;
}
// generate a pseudo-random password
char *password = malloc(length + 1);
if (password == NULL)
{
fprintf(stderr, "Error: Memory allocation failed\n");
return 1;
}
// seed the random number generator
// fixed: added a seeding step with time(NULL) to make the password more random
srand((unsigned int)time(NULL));
for (int i = 0; i < length; i++)
{
password[i] = (rand() % 94) + 33; // generates a character in the printable ASCII range
}
// null-terminate the string
password[length] = '\0';
// print the password
printf("%s\n", password);
// free allocated memory
free(password);
return 0;
}