fix: trust new identities

presage-cli/src/main.rs

@@ -33,6 +33,7 @@ use presage::{
     Manager,
 };
 use presage_store_sled::MigrationConflictStrategy;
+use presage_store_sled::OnNewIdentity;
 use presage_store_sled::SledStore;
 use tempfile::Builder;
 use tokio::task;
@@ -203,6 +204,7 @@ async fn main() -> anyhow::Result<()> {
         db_path,
         args.passphrase,
         MigrationConflictStrategy::Raise,
+        OnNewIdentity::Trust,
     )?;
     run(args.subcommand, config_store).await
 }

presage-store-sled/src/lib.rs

@@ -24,8 +24,8 @@ use presage::libsignal_service::{
     session_store::SessionStoreExt,
     Profile, ServiceAddress,
 };
-use presage::manager::RegistrationData;
 use presage::store::{ContentExt, ContentsStore, PreKeyStoreExt, StateStore, Store, Thread};
+use presage::{manager::RegistrationData, proto::verified};
 use prost::Message;
 use serde::{de::DeserializeOwned, Deserialize, Serialize};
 use sha2::{Digest, Sha256};
@@ -64,6 +64,8 @@ pub struct SledStore {
     db: Arc<RwLock<sled::Db>>,
     #[cfg(feature = "encryption")]
     cipher: Option<Arc<presage_store_cipher::StoreCipher>>,
+    /// Whether to trust new identities automatically (for instance, when a somebody's phone has changed)
+    trust_new_identities: OnNewIdentity,
 }
 
 /// Sometimes Migrations can't proceed without having to drop existing
@@ -111,11 +113,18 @@ impl SchemaVersion {
     }
 }
 
+#[derive(Debug, Clone)]
+pub enum OnNewIdentity {
+    Reject,
+    Trust,
+}
+
 impl SledStore {
     #[allow(unused_variables)]
     fn new(
         db_path: impl AsRef<Path>,
         passphrase: Option<impl AsRef<str>>,
+        trust_new_identities: OnNewIdentity,
     ) -> Result<Self, SledStoreError> {
         let database = sled::open(db_path)?;
 
@@ -133,25 +142,33 @@ impl SledStore {
             db: Arc::new(RwLock::new(database)),
             #[cfg(feature = "encryption")]
             cipher: cipher.map(Arc::new),
+            trust_new_identities,
         })
     }
 
     pub fn open(
         db_path: impl AsRef<Path>,
         migration_conflict_strategy: MigrationConflictStrategy,
+        trust_new_identities: OnNewIdentity,
     ) -> Result<Self, SledStoreError> {
-        Self::open_with_passphrase(db_path, None::<&str>, migration_conflict_strategy)
+        Self::open_with_passphrase(
+            db_path,
+            None::<&str>,
+            migration_conflict_strategy,
+            trust_new_identities,
+        )
     }
 
     pub fn open_with_passphrase(
         db_path: impl AsRef<Path>,
         passphrase: Option<impl AsRef<str>>,
         migration_conflict_strategy: MigrationConflictStrategy,
+        trust_new_identities: OnNewIdentity,
     ) -> Result<Self, SledStoreError> {
         let passphrase = passphrase.as_ref();
 
         migrate(&db_path, passphrase, migration_conflict_strategy)?;
-        Self::new(db_path, passphrase)
+        Self::new(db_path, passphrase, trust_new_identities)
     }
 
     #[cfg(feature = "encryption")]
@@ -182,6 +199,7 @@ impl SledStore {
             #[cfg(feature = "encryption")]
             // use store cipher with a random key
             cipher: Some(Arc::new(presage_store_cipher::StoreCipher::new())),
+            trust_new_identities: OnNewIdentity::Reject
         })
     }
 
@@ -297,7 +315,7 @@ fn migrate(
     let passphrase = passphrase.as_ref();
 
     let run_migrations = move || {
-        let mut store = SledStore::new(db_path, passphrase)?;
+        let mut store = SledStore::new(db_path, passphrase, OnNewIdentity::Reject)?;
         let schema_version = store.schema_version();
         for step in schema_version.steps() {
             match &step {
@@ -492,7 +510,7 @@ impl ContentsStore for SledStore {
         Ok(())
     }
 
-    fn save_message(&mut self, thread: &Thread, message: Content) -> Result<(), SledStoreError> {
+    fn save_message(&self, thread: &Thread, message: Content) -> Result<(), SledStoreError> {
         let ts = message.timestamp();
         log::trace!("storing a message with thread: {thread}, timestamp: {ts}",);
 
@@ -968,17 +986,28 @@ impl IdentityKeyStore for SledStore {
         identity_key: &IdentityKey,
     ) -> Result<bool, SignalProtocolError> {
         trace!("saving identity");
-        self.insert(
-            SLED_TREE_IDENTITIES,
-            address.to_string(),
-            identity_key.serialize(),
-        )
-        .map_err(|e| {
-            error!("error saving identity for {:?}: {}", address, e);
-            e.into_signal_error()
-        })?;
+        let existed_before = self
+            .insert(
+                SLED_TREE_IDENTITIES,
+                address.to_string(),
+                identity_key.serialize(),
+            )
+            .map_err(|e| {
+                error!("error saving identity for {:?}: {}", address, e);
+                e.into_signal_error()
+            })?;
+
+        self.save_trusted_identity_message(
+            address,
+            *identity_key,
+            if existed_before {
+                verified::State::Unverified
+            } else {
+                verified::State::Default
+            },
+        );
 
-        Ok(false)
+        Ok(true)
     }
 
     async fn is_trusted_identity(
@@ -998,7 +1027,17 @@ impl IdentityKeyStore for SledStore {
                 warn!("trusting new identity {:?}", address);
                 Ok(true)
             }
-            Some(left_identity_key) => Ok(left_identity_key == *right_identity_key),
+            // when we encounter some identity we know, we need to decide whether we trust it or not
+            Some(left_identity_key) => {
+                if left_identity_key == *right_identity_key {
+                    Ok(true)
+                } else {
+                    match self.trust_new_identities {
+                        OnNewIdentity::Trust => Ok(true),
+                        OnNewIdentity::Reject => Ok(false),
+                    }
+                }
+            }
         }
     }
 
@@ -1269,7 +1308,7 @@ mod tests {
 
     #[quickcheck_async::tokio]
     async fn test_store_messages(thread: Thread, content: Content) -> anyhow::Result<()> {
-        let mut db = SledStore::temporary()?;
+        let db = SledStore::temporary()?;
         let thread = thread.0;
         db.save_message(&thread, content_with_timestamp(&content, 1678295210))?;
         db.save_message(&thread, content_with_timestamp(&content, 1678295220))?;

presage/src/manager/linking.rs

@@ -28,12 +28,12 @@ impl<S: Store> Manager<S, Linking> {
     /// use futures::{channel::oneshot, future, StreamExt};
     /// use presage::libsignal_service::configuration::SignalServers;
     /// use presage::Manager;
-    /// use presage_store_sled::{MigrationConflictStrategy, SledStore};
+    /// use presage_store_sled::{MigrationConflictStrategy, OnNewIdentity, SledStore};
     ///
     /// #[tokio::main]
     /// async fn main() -> Result<(), Box<dyn std::error::Error>> {
     ///     let store =
-    ///         SledStore::open("/tmp/presage-example", MigrationConflictStrategy::Drop)?;
+    ///         SledStore::open("/tmp/presage-example", MigrationConflictStrategy::Drop, OnNewIdentity::Trust)?;
     ///
     ///     let (mut tx, mut rx) = oneshot::channel();
     ///     let (manager, err) = future::join(

presage/src/manager/registration.rs

@@ -39,12 +39,12 @@ impl<S: Store> Manager<S, Registration> {
     /// };
     /// use presage::manager::RegistrationOptions;
     /// use presage::Manager;
-    /// use presage_store_sled::{MigrationConflictStrategy, SledStore};
+    /// use presage_store_sled::{MigrationConflictStrategy, OnNewIdentity, SledStore};
     ///
     /// #[tokio::main]
     /// async fn main() -> Result<(), Box<dyn std::error::Error>> {
     ///     let store =
-    ///         SledStore::open("/tmp/presage-example", MigrationConflictStrategy::Drop)?;
+    ///         SledStore::open("/tmp/presage-example", MigrationConflictStrategy::Drop, OnNewIdentity::Trust)?;
     ///
     ///     let manager = Manager::register(
     ///         store,

presage/src/store.rs

@@ -1,21 +1,22 @@
 //! Traits that are used by the manager for storing the data.
 
-use std::{fmt, ops::RangeBounds};
+use std::{fmt, ops::RangeBounds, time::SystemTime};
 
 use libsignal_service::{
-    content::ContentBody,
+    content::{ContentBody, Metadata},
     groups_v2::Group,
     models::Contact,
     prelude::{Content, ProfileKey, Uuid, UuidError},
     proto::{
         sync_message::{self, Sent},
-        DataMessage, EditMessage, GroupContextV2, SyncMessage,
+        verified, DataMessage, EditMessage, GroupContextV2, SyncMessage, Verified,
     },
-    protocol::{ProtocolStore, SenderKeyStore},
+    protocol::{IdentityKey, ProtocolAddress, ProtocolStore, SenderKeyStore},
     session_store::SessionStoreExt,
     zkgroup::GroupMasterKeyBytes,
     Profile,
 };
+use log::error;
 use serde::{Deserialize, Serialize};
 
 use crate::manager::RegistrationData;
@@ -87,11 +88,54 @@ pub trait ContentsStore {
 
     /// Save a message in a [Thread] identified by a timestamp.
     fn save_message(
-        &mut self,
+        &self,
         thread: &Thread,
         message: Content,
     ) -> Result<(), Self::ContentsStoreError>;
 
+    /// Saves a message that can show users when the identity of a contact has changed
+    /// On Signal Android, this is usually displayed as: "Your safety number with XYZ has changed."
+    fn save_trusted_identity_message(
+        &self,
+        protocol_address: &ProtocolAddress,
+        right_identity_key: IdentityKey,
+        verified_state: verified::State,
+    ) {
+        let Ok(sender) = protocol_address.name().parse() else {
+            return;
+        };
+
+        // TODO: this is a hack to save a message showing that the verification status changed
+        // It is possibly ok to do it like this, but rebuidling the metadata and content body feels dirty
+        let thread = Thread::Contact(sender);
+        let verified_sync_message = Content {
+            metadata: Metadata {
+                sender: sender.into(),
+                sender_device: 0,
+                timestamp: SystemTime::now()
+                    .duration_since(SystemTime::UNIX_EPOCH)
+                    .unwrap_or_default()
+                    .as_secs(),
+                needs_receipt: false,
+                unidentified_sender: false,
+            },
+            body: SyncMessage {
+                verified: Some(Verified {
+                    destination_aci: None,
+                    identity_key: Some(right_identity_key.public_key().serialize().to_vec()),
+                    state: Some(verified_state.into()),
+                    null_message: None,
+                }),
+                ..Default::default()
+            }
+            .into(),
+        };
+
+        if let Err(error) = self.save_message(&thread, verified_sync_message) {
+            error!("failed to save the verified session message in thread: {error}");
+        }
+    }
+
     /// Delete a single message, identified by its received timestamp from a thread.
     /// Useful when you want to delete a message locally only.
     fn delete_message(