feat: Add IPv6 prefix-based rate limiting on login failures (#13070)

Enhance security by implementing rate limiting on IPv6 prefixes (/64, /56, /48)
to prevent brute force attacks that exploit cheap IPv6 address generation.

* Add private get_ipv6_prefixes() to calculate network prefixes
* Implement private check_failure_ipv6_prefix() for prefix-specific limits
  on IPv6 addresses
* Refactor check_failure() and update_failure() to support both IPs and prefixes
* Add ExceedIPv6PrefixAttempts to AlarmAuditType enum

Signed-off-by: Michael Bacarella <m@bacarella.com>

src/server/connection.rs

@@ -50,8 +50,10 @@ use serde_json::{json, value::Value};
 #[cfg(not(any(target_os = "android", target_os = "ios")))]
 use std::sync::atomic::Ordering;
 use std::{
+    net::Ipv6Addr,
     num::NonZeroI64,
     path::PathBuf,
+    str::FromStr,
     sync::{atomic::AtomicI64, mpsc as std_mpsc},
 };
 #[cfg(not(any(target_os = "android", target_os = "ios")))]
@@ -3173,35 +3175,134 @@ impl Connection {
         }
     }
 
-    fn update_failure(&self, (mut failure, time): ((i32, i32, i32), i32), remove: bool, i: usize) {
+    // Try to parse connection IP as IPv6 address, returning /64, /56, and /48 prefixes.
+    // Parsing an IPv4 address just returns None.
+    // note: we specifically don't use hbb_common::is_ipv6_str to avoid divergence issues
+    // between its regex and the system std::net::Ipv6Addr implementation.
+    fn get_ipv6_prefixes(&self) -> Option<(String, String, String)> {
+        fn mask_u128(addr: u128, prefix: u8) -> u128 {
+            let mask = if prefix == 0 || prefix > 128 {
+                0
+            } else {
+                (!0u128) << (128 - prefix)
+            };
+            addr & mask
+        }
+        // eliminate zone-ids like "fe80::1%eth0"
+        let ip_only = self.ip.split('%').next().unwrap_or(&self.ip).trim();
+        let ip = Ipv6Addr::from_str(ip_only).ok()?;
+
+        let as_u128 = u128::from_be_bytes(ip.octets());
+
+        let p64 = Ipv6Addr::from(mask_u128(as_u128, 64).to_be_bytes()).to_string() + "/64";
+        let p56 = Ipv6Addr::from(mask_u128(as_u128, 56).to_be_bytes()).to_string() + "/56";
+        let p48 = Ipv6Addr::from(mask_u128(as_u128, 48).to_be_bytes()).to_string() + "/48";
+
+        Some((p64, p56, p48))
+    }
+
+    fn update_failure(&self, (failure, time): ((i32, i32, i32), i32), remove: bool, i: usize) {
+        fn bump(mut cur: (i32, i32, i32), time: i32) -> (i32, i32, i32) {
+            if cur.0 == time {
+                cur.1 += 1;
+                cur.2 += 1;
+            } else {
+                cur.0 = time;
+                cur.1 = 1;
+                cur.2 += 1;
+            }
+            cur
+        }
+        let map_mutex = &LOGIN_FAILURES[i];
         if remove {
             if failure.0 != 0 {
-                LOGIN_FAILURES[i].lock().unwrap().remove(&self.ip);
+                if let Some((p64, p56, p48)) = self.get_ipv6_prefixes() {
+                    let mut m = map_mutex.lock().unwrap();
+                    m.remove(&p64);
+                    m.remove(&p56);
+                    m.remove(&p48);
+                    m.remove(&self.ip);
+                } else {
+                    map_mutex.lock().unwrap().remove(&self.ip);
+                }
             }
             return;
         }
-        if failure.0 == time {
-            failure.1 += 1;
-            failure.2 += 1;
+        // Bump the prefixes, fetching existing values
+        if let Some((p64, p56, p48)) = self.get_ipv6_prefixes() {
+            let mut m = map_mutex.lock().unwrap();
+            for key in [p64, p56, p48] {
+                let cur = m.get(&key).copied().unwrap_or((0, 0, 0));
+                m.insert(key, bump(cur, time));
+            }
+            // Update full IP: bump from the *original* passed-in failure
+            m.insert(self.ip.clone(), bump(failure, time));
         } else {
-            failure.0 = time;
-            failure.1 = 1;
-            failure.2 += 1;
+            // Update full IP: bump from the *original* passed-in failure
+            let mut m = map_mutex.lock().unwrap();
+            m.insert(self.ip.clone(), bump(failure, time));
         }
-        LOGIN_FAILURES[i]
+    }
+
+    async fn check_failure_ipv6_prefix(
+        &mut self,
+        i: usize,
+        time: i32,
+        prefix: &str,
+        prefix_num: i8,
+        thresh: i32,
+    ) -> Option<(((i32, i32, i32), i32), bool)> {
+        let failure_prefix = LOGIN_FAILURES[i]
             .lock()
             .unwrap()
-            .insert(self.ip.clone(), failure);
+            .get(prefix)
+            .copied()
+            .unwrap_or((0, 0, 0));
+
+        if failure_prefix.2 > thresh {
+            self.send_login_error(format!(
+                "Too many wrong attempts for IPv6 prefix /{}",
+                prefix_num
+            ))
+            .await;
+            Self::post_alarm_audit(
+                AlarmAuditType::ExceedIPv6PrefixAttempts,
+                json!({
+                            "ip": self.ip,
+                            "id": self.lr.my_id.clone(),
+                            "name": self.lr.my_name.clone(),
+                }),
+            );
+            Some(((failure_prefix, time), false))
+        } else {
+            None
+        }
     }
 
     async fn check_failure(&mut self, i: usize) -> (((i32, i32, i32), i32), bool) {
+        let time = (get_time() / 60_000) as i32;
+
+        // IPv6 addresses are cheap to make so we check prefix/netblock as well
+        if let Some((p64, p56, p48)) = self.get_ipv6_prefixes() {
+            if let Some(res) = self.check_failure_ipv6_prefix(i, time, &p64, 64, 60).await {
+                return res;
+            }
+            if let Some(res) = self.check_failure_ipv6_prefix(i, time, &p56, 56, 80).await {
+                return res;
+            }
+            if let Some(res) = self.check_failure_ipv6_prefix(i, time, &p48, 48, 100).await {
+                return res;
+            }
+        }
+
+        // checks IPv6 and IPv4 direct addresses
         let failure = LOGIN_FAILURES[i]
             .lock()
             .unwrap()
             .get(&self.ip)
-            .map(|x| x.clone())
+            .copied()
             .unwrap_or((0, 0, 0));
-        let time = (get_time() / 60_000) as i32;
+
         let res = if failure.2 > 30 {
             self.send_login_error("Too many wrong attempts").await;
             Self::post_alarm_audit(
@@ -4377,6 +4478,7 @@ pub enum AlarmAuditType {
     IpWhitelist = 0,
     ExceedThirtyAttempts = 1,
     SixAttemptsWithinOneMinute = 2,
+    ExceedIPv6PrefixAttempts = 3,
 }
 
 pub enum FileAuditType {
@@ -4942,4 +5044,11 @@ mod test {
         assert_eq!(pos.x, 510);
         assert_eq!(pos.y, 510);
     }
+
+    #[test]
+    fn ipv6() {
+        assert!(Ipv6Addr::from_str("::1").is_ok());
+        assert!(Ipv6Addr::from_str("127.0.0.1").is_err());
+        assert!(Ipv6Addr::from_str("0").is_err());
+    }
 }