Added Password Strength Evaluator utility class

Author: mhingan

pom.xml

@@ -48,6 +48,14 @@
           </dynamicDependencies>
         </configuration>
       </plugin>
+        <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-compiler-plugin</artifactId>
+            <configuration>
+                <source>11</source>
+                <target>11</target>
+            </configuration>
+        </plugin>
     </plugins>
   </build>
 </project>

src/main/java/PasswordEvaluator/PasswordStrengthEvaluator.java

@@ -0,0 +1,123 @@
+package PasswordEvaluator;
+
+import java.io.*;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.util.Random;
+
+/**
+ * A utility class for evaluating the strength of passwords
+ * and suggesting new secure passwords if needed.
+ */
+public class PasswordStrengthEvaluator {
+
+    private static final String LETTERS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+    /**
+     * Evaluates the strength of a given password based on multiple criteria:
+     * - Length between 8 and 30 characters
+     * - Contains both uppercase and lowercase letters
+     * - Contains special characters (@, &, !)
+     * - Is not a common password from a predefined list
+     *
+     * @param password the password to evaluate
+     * @return a string representing the strength level (MAX, MIN, COMMON)
+     * @throws IOException if there is a problem reading the common passwords file
+     */
+    public static String evaluatePassword(String password) throws IOException {
+
+        boolean hasUppercase = password.matches(".*[A-Z].*");
+        boolean hasLowercase = password.matches(".*[a-z].*");
+        boolean hasSpecialChar = password.contains("@") || password.contains("&") || password.contains("!");
+        int length = password.length();
+
+        boolean isCommon = isCommon(password);
+
+        if (!isCommon && length >= 8 && length < 30 && hasUppercase && hasLowercase && hasSpecialChar) {
+            return "Password strength level: MAX";
+        }
+
+        if (length < 8 || !hasUppercase || !hasLowercase || !hasSpecialChar || length >= 30) {
+            suggetsPassword(12);
+            return "Password strength level: MIN";
+        }
+
+        if (isCommon) {
+            return "Password strength level: COMMON" + suggetsPassword(12);
+        }
+
+        return "Unable to determine password strength.";
+    }
+
+
+    /**
+     * Checks whether a given password appears in a list of the most common passwords,
+     * retrieved from a remote public file on GitHub. The comparison is exact, line by line.
+     *
+     * @param password the password to check
+     * @return true if the password is exactly matched in the list, false otherwise
+     * @throws RuntimeException if there is an error reading the remote password file
+     */
+    public static boolean isCommon(String password) {
+        String fileUrl = "https://raw.githubusercontent.com/danielmiessler/SecLists/refs/heads/master/Passwords/Common-Credentials/10-million-password-list-top-1000000.txt";
+
+        try {
+            HttpClient client = HttpClient.newHttpClient();
+            HttpRequest request = HttpRequest.newBuilder()
+                    .uri(URI.create(fileUrl))
+                    .build();
+
+            HttpResponse<InputStream> response = client.send(request, HttpResponse.BodyHandlers.ofInputStream());
+
+            try (BufferedReader reader = new BufferedReader(new InputStreamReader(response.body()))) {
+                String line;
+                while ((line = reader.readLine()) != null) {
+                    if (line.equals(password)) {
+                        return true;
+                    }
+                }
+            }
+
+        } catch (Exception e) {
+            throw new RuntimeException("Error reading the common passwords file.", e);
+        }
+
+        return false;
+    }
+
+
+
+
+
+    /**
+     * Suggests a secure random password of a specified length,
+     * containing only uppercase and lowercase letters.
+     *
+     * If the requested length is less than 8, a password with 8 characters is suggested
+     * and a warning message is returned.
+     *
+     * @param length the desired length of the suggested password
+     * @return a suggested password or a warning message if the length is too short
+     */
+    private static String suggetsPassword(int length) {
+        Random random = new Random();
+        StringBuilder password = new StringBuilder();
+        StringBuilder provisionallyPassword = new StringBuilder();
+
+        if (length >= 8) {
+            for (int i = 0; i < length; i++) {
+                int index = random.nextInt(LETTERS.length());
+                password.append(LETTERS.charAt(index));
+            }
+            return password.toString();
+        } else {
+            for (int i = 0; i < 8; i++) {
+                int index = random.nextInt(LETTERS.length());
+                provisionallyPassword.append(LETTERS.charAt(index));
+            }
+            return "Length must be between 8 and 30 characters. Suggested password with 8 characters: " + provisionallyPassword.toString();
+        }
+    }
+}

src/main/java/PasswordEvaluator/TestPasswordEvaluator.java

@@ -0,0 +1,23 @@
+package PasswordEvaluator;
+
+import java.io.IOException;
+import java.util.Scanner;
+
+public class TestPasswordEvaluator {
+
+
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+        System.out.println("Enter a password to evaluate:");
+        String input = scanner.nextLine();
+
+        try {
+            String result = PasswordStrengthEvaluator.evaluatePassword(input);
+            System.out.println(result);
+        } catch (IOException e) {
+            System.out.println("Error: " + e.getMessage());
+        }
+    }
+}
+
+