IP anonymizing

use ip_anonymize.qweruse ip_truncate, ip_anonymize from ip_anonymize      // Quillo 0.6: only these

ipnet = "2"hmac = "0.12"sha2 = "0.10"

// Privacy-friendly access logs and a daily visitor count that keep no full IP address.////   quillo run ip_anonymize.qwe      then open http://localhost:8080/samplesuse "ip_anonymize.qwer"let SECRET = env("IP_SALT_SECRET") ?? crypto.token(32)// A new salt each day: today's pseudonyms cannot be tied to tomorrow's.fn todays_salt() = crypto.sha256(`${SECRET}:${date.today()}`)route GET /visit {    let line = { at: now(), ip: ip_anonymize(request.ip)?, path: request.path, visitor: ip_pseudonym(request.ip, todays_salt())? }    write_file("data/access.log", json.stringify(line))    line}route GET /samples = {    v4: ip_anonymize("203.0.113.77")?,    v6: ip_anonymize("2001:db8:85a3:8d3:1319:8a2e:370:7348")?,    mapped: ip_anonymize("::ffff:198.51.100.23")?,    coarse: ip_network("203.0.113.77", 16, 32)?,    same_visitor: ip_pseudonym("203.0.113.77", "a salt of at least sixteen") == ip_pseudonym("203.0.113.77", "a salt of at least sixteen"),    no_salt: ip_pseudonym("203.0.113.77", "").error,}

//! IP addresses made GDPR-friendly for logs and analytics: the last part cut off (/24 for IPv4, /48 for IPv6, or your own), or a salted hash that counts visitors without keeping who they were.//! version: 1.0.0//!//! [dependencies]//! ipnet = "2"//! hmac = "0.12"//! sha2 = "0.10"use hmac::{Hmac, Mac};use ipnet::{IpNet, Ipv4Net, Ipv6Net};use sha2::Sha256;use std::net::IpAddr;fn parse(ip: &str) -> Result<IpAddr, String> {    let ip: IpAddr = ip.trim().trim_start_matches('[').trim_end_matches(']').parse().map_err(|_| format!("`{}` is not an IP address", ip))?;    // An IPv4 address seen through IPv6 (::ffff:203.0.113.9) is cut as IPv4.    Ok(match ip {        IpAddr::V6(v6) => v6.to_ipv4_mapped().map(IpAddr::V4).unwrap_or(ip),        v4 => v4,    })}fn net(ip: &str, v4_bits: i64, v6_bits: i64) -> Result<IpNet, String> {    Ok(match parse(ip)? {        IpAddr::V4(a) => IpNet::V4(Ipv4Net::new(a, v4_bits.clamp(0, 32) as u8).map_err(|e| e.to_string())?.trunc()),        IpAddr::V6(a) => IpNet::V6(Ipv6Net::new(a, v6_bits.clamp(0, 128) as u8).map_err(|e| e.to_string())?.trunc()),    })}/// `ip` with all but its first `v4_bits` (IPv4) or `v6_bits` (IPv6) bits set to zero: `203.0.113.77` with 24 is `203.0.113.0`,/// `2001:db8:85a3:8d3:1319:8a2e:370:7348` with 48 is `2001:db8:85a3::`. Bits are kept within 0 to 32 and 0 to 128.pub fn ip_truncate(ip: &str, v4_bits: i64, v6_bits: i64) -> Result<String, String> {    Ok(net(ip, v4_bits, v6_bits)?.network().to_string())}/// `ip` cut as most analytics tools cut it for the GDPR: the last byte of an IPv4 (/24), the last 80 bits of an IPv6 (/48).pub fn ip_anonymize(ip: &str) -> Result<String, String> {    ip_truncate(ip, 24, 48)}/// The network `ip` falls in, cut as ip_truncate cuts it, written with its prefix: `203.0.113.0/24`. For grouping visitors.pub fn ip_network(ip: &str, v4_bits: i64, v6_bits: i64) -> Result<String, String> {    Ok(net(ip, v4_bits, v6_bits)?.to_string())}/// A pseudonym for `ip`: HMAC-SHA256 keyed with `salt`, the first 16 bytes in hex. The same IP and salt give the same/// pseudonym, so visits can be counted; change the salt each day (and forget the old one) and yesterday's pseudonyms/// can no longer be tied to anyone. With an empty salt it is an error: an unsalted hash of an IP is easy to reverse.pub fn ip_pseudonym(ip: &str, salt: &str) -> Result<String, String> {    if salt.len() < 16 {        return Err("give a salt of at least 16 random characters: an IP hashed without a secret can be found again".into());    }    let mut m = Hmac::<Sha256>::new_from_slice(salt.as_bytes()).map_err(|e| e.to_string())?;    m.update(parse(ip)?.to_string().as_bytes());    Ok(m.finalize().into_bytes()[..16].iter().map(|b| format!("{:02x}", b)).collect())}