feat: [#978] add a config option to disable cheking keys' expiration

When the tracker is running in private mode you can disable checking
keys' expiration in the configuration with:

```toml
[core]
private = false

[core.private_mode]
check_keys_expiration = true
```

All keys will be valid as long as they exist in the database.

packages/configuration/src/v2/core.rs

@@ -1,3 +1,4 @@
+use derive_more::{Constructor, Display};
 use serde::{Deserialize, Serialize};
 
 use super::network::Network;
@@ -32,6 +33,10 @@ pub struct Core {
     #[serde(default = "Core::default_private")]
     pub private: bool,
 
+    // Configuration specific when the tracker is running in private mode.
+    #[serde(default = "Core::default_private_mode")]
+    pub private_mode: Option<PrivateMode>,
+
     // Tracker policy configuration.
     #[serde(default = "Core::default_tracker_policy")]
     pub tracker_policy: TrackerPolicy,
@@ -54,6 +59,7 @@ impl Default for Core {
             listed: Self::default_listed(),
             net: Self::default_network(),
             private: Self::default_private(),
+            private_mode: Self::default_private_mode(),
             tracker_policy: Self::default_tracker_policy(),
             tracker_usage_statistics: Self::default_tracker_usage_statistics(),
         }
@@ -85,10 +91,43 @@ impl Core {
         false
     }
 
+    fn default_private_mode() -> Option<PrivateMode> {
+        if Self::default_private() {
+            Some(PrivateMode::default())
+        } else {
+            None
+        }
+    }
+
     fn default_tracker_policy() -> TrackerPolicy {
         TrackerPolicy::default()
     }
     fn default_tracker_usage_statistics() -> bool {
         true
     }
 }
+
+/// Configuration specific when the tracker is running in private mode.
+#[derive(Serialize, Deserialize, PartialEq, Eq, Debug, Clone, Copy, Constructor, Display)]
+pub struct PrivateMode {
+    /// A flag to disable expiration date for peer keys.
+    ///
+    /// When true, if the keys is not permanent the expiration date will be
+    /// ignored. The key will be accepted even if it has expired.
+    #[serde(default = "PrivateMode::default_check_keys_expiration")]
+    pub check_keys_expiration: bool,
+}
+
+impl Default for PrivateMode {
+    fn default() -> Self {
+        Self {
+            check_keys_expiration: Self::default_check_keys_expiration(),
+        }
+    }
+}
+
+impl PrivateMode {
+    fn default_check_keys_expiration() -> bool {
+        true
+    }
+}

src/core/auth.rs

@@ -33,7 +33,7 @@
 //!
 //! // And you can later verify it with:
 //!
-//! assert!(auth::verify_key(&expiring_key).is_ok());
+//! assert!(auth::verify_key_expiration(&expiring_key).is_ok());
 //! ```
 
 use std::panic::Location;
@@ -106,7 +106,7 @@ pub fn generate_key(lifetime: Option<Duration>) -> PeerKey {
 ///
 /// - `Error::KeyExpired` if `auth_key.valid_until` is past the `current_time`.
 /// - `Error::KeyInvalid` if `auth_key.valid_until` is past the `None`.
-pub fn verify_key(auth_key: &PeerKey) -> Result<(), Error> {
+pub fn verify_key_expiration(auth_key: &PeerKey) -> Result<(), Error> {
     let current_time: DurationSinceUnixEpoch = CurrentClock::now();
 
     match auth_key.valid_until {
@@ -322,7 +322,7 @@ mod tests {
         fn should_be_generated_with_a_expiration_time() {
             let expiring_key = auth::generate_key(Some(Duration::new(9999, 0)));
 
-            assert!(auth::verify_key(&expiring_key).is_ok());
+            assert!(auth::verify_key_expiration(&expiring_key).is_ok());
         }
 
         #[test]
@@ -336,12 +336,12 @@ mod tests {
             // Mock the time has passed 10 sec.
             clock::Stopped::local_add(&Duration::from_secs(10)).unwrap();
 
-            assert!(auth::verify_key(&expiring_key).is_ok());
+            assert!(auth::verify_key_expiration(&expiring_key).is_ok());
 
             // Mock the time has passed another 10 sec.
             clock::Stopped::local_add(&Duration::from_secs(10)).unwrap();
 
-            assert!(auth::verify_key(&expiring_key).is_err());
+            assert!(auth::verify_key_expiration(&expiring_key).is_err());
         }
     }
 }

src/core/mod.rs

@@ -996,7 +996,16 @@ impl Tracker {
                 location: Location::caller(),
                 key: Box::new(key.clone()),
             }),
-            Some(key) => auth::verify_key(key),
+            Some(key) => match self.config.private_mode {
+                Some(private_mode) => {
+                    if private_mode.check_keys_expiration {
+                        return auth::verify_key_expiration(key);
+                    }
+
+                    Ok(())
+                }
+                None => auth::verify_key_expiration(key),
+            },
         }
     }
 
@@ -1779,8 +1788,9 @@ mod tests {
                 use std::time::Duration;
 
                 use torrust_tracker_clock::clock::Time;
+                use torrust_tracker_configuration::v2::core::PrivateMode;
 
-                use crate::core::auth;
+                use crate::core::auth::{self, Key};
                 use crate::core::tests::the_tracker::private_tracker;
                 use crate::CurrentClock;
 
@@ -1829,6 +1839,24 @@ mod tests {
                     assert!(tracker.verify_auth_key(&expiring_key.key()).await.is_ok());
                 }
 
+                #[tokio::test]
+                async fn it_should_accept_an_expired_key_when_checking_expiration_is_disabled_in_configuration() {
+                    let mut tracker = private_tracker();
+
+                    tracker.config.private_mode = Some(PrivateMode {
+                        check_keys_expiration: false,
+                    });
+
+                    let past_time = Some(Duration::ZERO);
+
+                    let expiring_key = tracker
+                        .add_auth_key(Key::new("YZSl4lMZupRuOpSRC3krIKR5BPB14nrJ").unwrap(), past_time)
+                        .await
+                        .unwrap();
+
+                    assert!(tracker.authenticate(&expiring_key.key()).await.is_ok());
+                }
+
                 #[tokio::test]
                 async fn it_should_fail_verifying_an_unregistered_authentication_key() {
                     let tracker = private_tracker();