Initial data commit

Task/SQL-based-authentication/Java/sql-based-authentication.java

@@ -0,0 +1,142 @@
+import java.io.UnsupportedEncodingException;
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
+import java.math.BigInteger;
+
+
+class UserManager {
+    private Connection dbConnection;
+
+    public UserManager() {
+    }
+
+    private String md5(String aString) throws NoSuchAlgorithmException, UnsupportedEncodingException {
+        MessageDigest md;
+        String hex;
+        StringBuffer hexString;
+        byte[] bytesOfMessage;
+        byte[] theDigest;
+
+        hexString = new StringBuffer();
+        bytesOfMessage = aString.getBytes("UTF-8");
+        md = MessageDigest.getInstance("MD5");
+        theDigest = md.digest(bytesOfMessage);
+
+        for (int i = 0; i < theDigest.length; i++) {
+            hex = Integer.toHexString(0xff & theDigest[i]);
+            if (hex.length() == 1) {
+                hexString.append('0');
+            }
+            hexString.append(hex);
+        }
+
+        return hexString.toString();
+    }
+
+    public void connectDB(String host, int port, String db, String user, String password)
+      throws ClassNotFoundException, SQLException {
+
+        Class.forName("com.mysql.jdbc.Driver");
+
+        this.dbConnection =  DriverManager.getConnection("jdbc:mysql://"
+                                + host
+                                + ":"
+                                + port
+                                + "/"
+                                + db, user, password);
+    }
+
+    public boolean createUser(String user, String password) {
+        SecureRandom random;
+        String insert;
+        String salt;
+
+        random = new SecureRandom();
+        salt =  new BigInteger(130, random).toString(16);
+
+        insert = "INSERT INTO users "
+            + "(username, pass_salt, pass_md5) "
+            + "VALUES (?, ?, ?)";
+
+        try (PreparedStatement pstmt = this.dbConnection.prepareStatement(insert)) {
+            pstmt.setString(1, user);
+            pstmt.setString(2, salt);
+            pstmt.setString(3, this.md5(salt + password));
+            pstmt.executeUpdate();
+
+            return true;
+        } catch(NoSuchAlgorithmException | SQLException | UnsupportedEncodingException ex) {
+            return false;
+        }
+    }
+
+    public boolean authenticateUser(String user, String password) {
+        String pass_md5;
+        String pass_salt;
+        String select;
+        ResultSet res;
+
+        select = "SELECT pass_salt, pass_md5 FROM users WHERE username = ?";
+        res = null;
+
+        try(PreparedStatement pstmt = this.dbConnection.prepareStatement(select)) {
+            pstmt.setString(1, user);
+            res = pstmt.executeQuery();
+
+            res.next(); // We assume that username is unique
+
+            pass_salt = res.getString(1);
+            pass_md5 = res.getString(2);
+
+            if (pass_md5.equals(this.md5(pass_salt + password))) {
+                return true;
+            } else {
+                return false;
+            }
+
+        } catch(NoSuchAlgorithmException | SQLException | UnsupportedEncodingException ex) {
+            return false;
+        } finally {
+            try {
+                if (res instanceof ResultSet && !res.isClosed()) {
+                    res.close();
+                }
+            } catch(SQLException ex) {
+            }
+        }
+    }
+
+    public void closeConnection() {
+        try {
+            this.dbConnection.close();
+        } catch(NullPointerException | SQLException ex) {
+        }
+    }
+
+    public static void main(String[] args) {
+        UserManager um;
+
+        um = new UserManager();
+        try {
+            um.connectDB("localhost", 3306, "test", "root", "admin");
+
+            if (um.createUser("johndoe", "test")) {
+                System.out.println("User created");
+            }
+
+            if (um.authenticateUser("johndoe", "test")) {
+                System.out.println("User authenticated");
+            }
+        } catch(ClassNotFoundException | SQLException ex) {
+            ex.printStackTrace();
+        } finally {
+            um.closeConnection();
+        }
+    }
+}