CIDR tool: check if an IP address belongs to a CIDR block

cidr_tool.py

license = '''Copyright (c) 2024 Jonathan Voss (k98kurz)

Permission to use, copy, modify, and/or distribute this software
for any purpose with or without fee is hereby granted, provided
that the above copyleft notice and this permission notice appear in
all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
'''

import customtkinter as ctk


def get_good_color():
    return "white" if ctk.get_appearance_mode().lower() == "dark" else "black"


class App(ctk.CTk):
    def __init__(self, license):
        super().__init__()
        self.license = license

        # Window configuration
        self.title("CIDR/IP Checker")
        self.geometry("550x380")

        # Create scrollable frame instead of regular frame
        self.main_frame = ctk.CTkFrame(self, fg_color="transparent")
        self.main_frame.pack(pady=20, padx=20, fill="both", expand=True)

        # CIDR input
        self.cidr_label = ctk.CTkLabel(self.main_frame, text="CIDR Block:")
        self.cidr_label.pack(pady=(20, 5))
        self.cidr_entry = ctk.CTkEntry(self.main_frame, placeholder_text="e.g., 192.168.1.0/24")
        self.cidr_entry.pack(pady=(0, 10))
        self.cidr_entry.bind("<Return>", lambda event: self.check_ip())
        self.cidr_entry.bind("<KP_Enter>", lambda event: self.check_ip())

        # IP input
        self.ip_label = ctk.CTkLabel(self.main_frame, text="IP Address:")
        self.ip_label.pack(pady=(10, 5))
        self.ip_entry = ctk.CTkEntry(self.main_frame, placeholder_text="e.g., 192.168.1.100")
        self.ip_entry.pack(pady=(0, 20))
        self.ip_entry.bind("<Return>", lambda event: self.check_ip())
        self.ip_entry.bind("<KP_Enter>", lambda event: self.check_ip())

        # Check button
        self.check_button = ctk.CTkButton(self.main_frame, text="Check", command=self.check_ip)
        self.check_button.pack(pady=10)

        # Result label
        self.result_label = ctk.CTkLabel(self.main_frame, text="result will be here", font=("Arial", 18))
        self.result_label.pack(pady=20)

        # License button
        self.license_button = ctk.CTkButton(self.main_frame, text="ISC License", command=self.show_license)
        self.license_button.pack(pady=10)

    def show_license(self):
        # resolution
        width = 600
        height = 350
        # open a new window with the license
        license_window = ctk.CTkToplevel(self)
        license_window.title("ISC License")
        license_window.geometry(f"{width}x{height}")
        # add a text widget with the license
        license_text = ctk.CTkTextbox(license_window, wrap="none", height=height, width=width, text_color=get_good_color(), fg_color="transparent")
        license_text.pack(pady=20, padx=20, fill="both", expand=True)
        license_text.insert("0.0", self.license)
        license_text.configure(state="disabled")
        license_window.mainloop()

    def check_ip(self):
        try:
            # Get the network from CIDR notation
            cidr_txt = self.cidr_entry.get()
            # Get the IP address to check
            addr_txt = self.ip_entry.get()

            # Determine the bitmask as preceding bits of a 32 bit integer
            bits = int(cidr_txt.split('/')[1])
            bitmask = ((1 << 32)) - (1 << (32 - bits))

            # shift the bits in the cidr and combine into a single integer
            cidr = [int(c) for c in cidr_txt.split('/')[0].split('.')]
            cidr = (cidr[0] << 24) + (cidr[1] << 16) + (cidr[2] << 8) + cidr[3]

            # shift the bits in the IP address and combine into a single integer
            ip = [int(c) for c in addr_txt.split('.')]
            ip = (ip[0] << 24) + (ip[1] << 16) + (ip[2] << 8) + ip[3]

            # check if the IP prefix matches the CIDR prefix
            if (cidr & bitmask) == (ip & bitmask):
                self.result_label.configure(text=f"IP {addr_txt} is in the network {cidr_txt}")
                self.result_label.configure(text_color=get_good_color())
            else:
                self.result_label.configure(text=f"IP {addr_txt} is NOT in the network {cidr_txt}")
                self.result_label.configure(text_color="orange")

        except BaseException as e:
            self.result_label.configure(text=f"Error: {e}")
            self.result_label.configure(text_color="orange")


def main():
    app = App(license)
    app.mainloop()


if __name__ == "__main__":
    main()