Password checker in c language - c

Question

I want to take input as a string and evaluate if it is a valid password. The password is valid if it has numbers, capital and small alphabets, and a length of at least 7 characters. Also, when all these requirements are satisfied, the output should be "Strong", else "Weak". Code:
#include<stdio.h>
#include<string.h>
#define N 20
int main()
{
char pass[N];
int i, x=0, p;
printf("Enter a password: ");
scanf("%s", &pass);
if(strlen(pass)>=7)
{
p=strlen(pass);
for (i = 0; i < p; i++)
{
if ((pass[i] >= 'a' && pass[i] <= 'z') || (pass[i] >= 'A' && pass[i <= 'Z') || (pass[i] >= '0' && pass[i] <= '9'))
printf("Sucess! ");
}
}
else
printf("Try Again..");
return 0;
}
Somethings are not working like: 1. After execution, it prints "Sucess!!" multiple times.. 2. In the inner if block, when i replace || with &&, it didn't print anything.
Please help.

Answer 1

You could change this section of code:
p=strlen(pass);
for (i = 0; i < p; i++)
{
if ((pass[i] >= 'a' && pass[i] <= 'z') || (pass[i] >= 'A' && pass[i <= 'Z') || (pass[i] >= '0' && pass[i] <= '9'))
printf("Sucess! ");
}
... to something like this:
int lower_case_count = 0;
int upper_case_count = 0;
int digit_count = 0;
p=strlen(pass);
for (i = 0; i < p; i++) {
if (pass[i] >= 'a' && pass[i] <= 'z') ++lower_case_count;
if (pass[i] >= 'A' && pass[i] <= 'Z') ++upper_case_count;
if (pass[i] >= '0' && pass[i] <= '9') ++digit_count;
}
if (lower_case_count > 0 && upper_case_count > 0 && digit_count > 0) {
printf("Strong\n");
}
In the loop you just want to count how many of each type of characters is present.
Once the loop is done, you can check whether all requirements are satisfied and take appropriate action.

Answer 2

You made me thinking and I came up with this rather simple solution - two series of ifs, one wrapped within a while loop. It checks for lower and uppercase, numbers and special characters, reporting the exact error a user had eventually made.
//A program for password validation
#include <stdio.h>
#include <ctype.h>//for islower(), isupper(), isdigit() and ispunct()
#include <string.h>//for strlen()
int main(void)
{
char pass[30];
printf("Enter your password: ");
scanf("%[^\n]s", pass);//so that password may contain space char
int i = 0,
lower_count = 0,
upper_count = 0,
digit_count = 0,
punct_count = 0;
int length = strlen(pass);
//loop goes through the password as array
while (pass[i]) {
if(islower(pass[i]))//if there is lowercase
lower_count++;
if(isupper(pass[i]))//if there is uppercase
upper_count++;
if (isdigit(pass[i]))//if there is a number
digit_count++;
if (ispunct(pass[i]))//if there is a special chars
punct_count++;
i++;
}
if(strlen(pass) < 8)
{
printf("The password must have at least 8 chars\n");
return 1;
}
if(lower_count == 0)
{
printf("You need lowercases\n");
}
if(upper_count == 0)
{
printf("You need an uppercase\n");
}
if(digit_count == 0)
{
printf("You need digits\n");
}
if(punct_count == 0)
{
printf("You need a special character\n");
}
if(upper_count != 0 && digit_count != 0 && punct_count != 0 &&
length > 12)
{
printf("Your password is strong!\n");
}
if(upper_count != 0 && digit_count != 0 && punct_count != 0 &&
length <= 12)
{
printf("Your password is OK\n");
}
return 0;
}