pam: Support changing user secret

By changing keyring secrets as well if we can unlock them using the
previous secret

Author: bilelmoussaoui

Cargo.lock

@@ -17,6 +17,7 @@ crate-type = ["cdylib"]
 libc = "0.2"
 tokio = { workspace = true, features = ["rt", "rt-multi-thread", "net", "io-util", "sync", "time"] }
 serde = { workspace = true }
+serde_repr = "0.1"
 zvariant = { workspace = true }
 tracing = { workspace = true }
 tracing-subscriber = { workspace = true, features = ["env-filter"] }

pam/Cargo.toml

@@ -59,14 +59,25 @@ auth       required     pam_unix.so
 auth       optional     pam_oo7.so
 account    required     pam_unix.so
 password   required     pam_unix.so
+password   optional     pam_oo7.so
 session    required     pam_unix.so
 session    optional     pam_oo7.so auto_start
 session    optional     pam_systemd.so
 ```
 
-**Important**: The module must be added to both `auth` and `session` stacks:
-- `auth` stack: Captures and stashes the password
-- `session` stack: Retrieves the password and sends it to the daemon
+**Important**: The module should be added to three PAM stacks:
+- `auth` stack: Captures and stashes the password during authentication
+- `session` stack: Retrieves the stashed password and sends it to the daemon for keyring unlocking
+- `password` stack: Intercepts password changes and updates the keyring password to match
+
+#### Password Change Support
+
+When added to the `password` stack, the module will automatically update your keyring passwords when you change your user password (e.g., using `passwd` command). This ensures your keyrings remain accessible after password changes.
+
+The module intercepts the password change operation:
+1. Captures both the old and new passwords
+2. Sends them to the daemon
+3. The daemon validates the old password and re-encrypts all matching keyrings with the new password
 
 ## Configuration
 

pam/README.md

@@ -4,9 +4,15 @@ use std::os::raw::{c_char, c_int, c_void};
 pub const PAM_SUCCESS: c_int = 0;
 pub const PAM_SYSTEM_ERR: c_int = 4;
 pub const PAM_AUTHTOK_RECOVER_ERR: c_int = 20;
+pub const PAM_IGNORE: c_int = 25;
 
 // PAM item types
 pub const PAM_AUTHTOK: c_int = 6;
+pub const PAM_OLDAUTHTOK: c_int = 7;
+
+// PAM chauthtok flags
+pub const PAM_PRELIM_CHECK: c_int = 0x1;
+pub const PAM_UPDATE_AUTHTOK: c_int = 0x2;
 
 // Opaque PAM handle type
 #[repr(C)]

pam/src/ffi.rs

@@ -15,7 +15,10 @@ use std::{
 use zeroize::Zeroizing;
 
 use crate::{
-    ffi::{PAM_AUTHTOK, PAM_AUTHTOK_RECOVER_ERR, PAM_SUCCESS, PAM_SYSTEM_ERR, pam_handle_t},
+    ffi::{
+        PAM_AUTHTOK, PAM_AUTHTOK_RECOVER_ERR, PAM_IGNORE, PAM_OLDAUTHTOK, PAM_PRELIM_CHECK,
+        PAM_SUCCESS, PAM_SYSTEM_ERR, PAM_UPDATE_AUTHTOK, pam_handle_t,
+    },
     protocol::PamMessage,
     socket::send_secret_to_daemon,
 };
@@ -42,18 +45,30 @@ unsafe fn get_user(pamh: *mut pam_handle_t) -> Result<String, c_int> {
 
 /// Get the authentication token from PAM
 unsafe fn get_auth_token(pamh: *mut pam_handle_t) -> Result<Zeroizing<Vec<u8>>, c_int> {
+    unsafe { get_auth_token_internal(pamh, PAM_AUTHTOK, "PAM_AUTHTOK") }
+}
+
+/// Get the old authentication token from PAM (for password changes)
+unsafe fn get_old_auth_token(pamh: *mut pam_handle_t) -> Result<Zeroizing<Vec<u8>>, c_int> {
+    unsafe { get_auth_token_internal(pamh, PAM_OLDAUTHTOK, "PAM_OLDAUTHTOK") }
+}
+
+unsafe fn get_auth_token_internal(
+    pamh: *mut pam_handle_t,
+    item_type: c_int,
+    item_name: &str,
+) -> Result<Zeroizing<Vec<u8>>, c_int> {
     let mut authtok_ptr: *const std::os::raw::c_void = std::ptr::null();
 
-    // Use pam_get_item to get PAM_AUTHTOK (just like pam_gnome_keyring does)
-    let ret = unsafe { ffi::pam_get_item(pamh, PAM_AUTHTOK, &mut authtok_ptr) };
+    let ret = unsafe { ffi::pam_get_item(pamh, item_type, &mut authtok_ptr) };
 
     if ret != PAM_SUCCESS {
-        tracing::debug!("pam_get_item returned error: {}", ret);
+        tracing::debug!("pam_get_item({}) returned error: {}", item_name, ret);
         return Err(ret);
     }
 
     if authtok_ptr.is_null() {
-        tracing::debug!("PAM_AUTHTOK is null (password not available)");
+        tracing::debug!("{} is null (password not available)", item_name);
         return Err(PAM_SYSTEM_ERR);
     }
 
@@ -62,7 +77,8 @@ unsafe fn get_auth_token(pamh: *mut pam_handle_t) -> Result<Zeroizing<Vec<u8>>,
     let password_bytes = password_cstr.to_bytes().to_vec();
 
     tracing::debug!(
-        "Captured auth token of length {} bytes",
+        "Captured {} of length {} bytes",
+        item_name,
         password_bytes.len()
     );
 
@@ -258,10 +274,7 @@ pub unsafe extern "C" fn pam_sm_open_session(
         }
     };
 
-    let message = PamMessage {
-        username: username.clone(),
-        secret: password.to_vec(),
-    };
+    let message = PamMessage::unlock(username.clone(), password.to_vec());
 
     // Send the secret to the oo7 daemon
     std::thread::spawn(
@@ -294,11 +307,100 @@ pub extern "C" fn pam_sm_close_session(
 
 /// PAM password change entry point
 #[unsafe(no_mangle)]
-pub extern "C" fn pam_sm_chauthtok(
-    _pamh: *mut pam_handle_t,
-    _flags: c_int,
+#[allow(clippy::missing_safety_doc)]
+pub unsafe extern "C" fn pam_sm_chauthtok(
+    pamh: *mut pam_handle_t,
+    flags: c_int,
     _argc: c_int,
     _argv: *mut *const c_char,
 ) -> c_int {
-    PAM_SUCCESS
+    if let Ok(layer) = tracing_journald::layer() {
+        use tracing_subscriber::layer::SubscriberExt;
+        let subscriber = tracing_subscriber::registry().with(layer);
+        let _ = tracing::subscriber::set_global_default(subscriber);
+    }
+
+    if flags & PAM_PRELIM_CHECK != 0 {
+        tracing::debug!("PAM_PRELIM_CHECK phase for password change");
+        return PAM_IGNORE;
+    }
+
+    if flags & PAM_UPDATE_AUTHTOK != 0 {
+        tracing::debug!("PAM_UPDATE_AUTHTOK phase for password change");
+
+        let username = match unsafe { get_user(pamh) } {
+            Ok(user) => user,
+            Err(ret) => {
+                tracing::error!("Failed to get username during password change");
+                return ret;
+            }
+        };
+
+        let user_uid = match get_user_uid(&username) {
+            Some(uid) => uid,
+            None => {
+                tracing::error!("Failed to get UID for user: {}", username);
+                return PAM_SYSTEM_ERR;
+            }
+        };
+
+        let old_password = match unsafe { get_old_auth_token(pamh) } {
+            Ok(pass) => pass,
+            Err(_) => {
+                tracing::warn!(
+                    "No old password available for user {}, cannot update keyring password",
+                    username
+                );
+                return PAM_SUCCESS;
+            }
+        };
+
+        let new_password = match unsafe { get_auth_token(pamh) } {
+            Ok(pass) => pass,
+            Err(_) => {
+                tracing::warn!(
+                    "No new password available for user {}, cannot update keyring password",
+                    username
+                );
+                return PAM_SUCCESS;
+            }
+        };
+
+        if old_password.is_empty() || new_password.is_empty() {
+            tracing::debug!("Old or new password is empty, skipping keyring password change");
+            return PAM_SUCCESS;
+        }
+
+        tracing::info!(
+            "Password change for user {}: old={} bytes, new={} bytes",
+            username,
+            old_password.len(),
+            new_password.len()
+        );
+
+        let message = PamMessage::change_password(
+            username.clone(),
+            old_password.to_vec(),
+            new_password.to_vec(),
+        );
+
+        std::thread::spawn(
+            move || match send_secret_to_daemon(message, user_uid, false) {
+                Ok(_) => {
+                    tracing::info!(
+                        "Successfully sent password change request to oo7 daemon for user: {}",
+                        username
+                    );
+                }
+                Err(e) => {
+                    tracing::error!("Failed to send password change to oo7 daemon: {}", e);
+                }
+            },
+        );
+
+        return PAM_SUCCESS;
+    }
+
+    tracing::warn!("pam_sm_chauthtok called with unknown flags: {}", flags);
+    PAM_IGNORE
 }

pam/src/lib.rs

@@ -1,14 +1,45 @@
 use serde::{Deserialize, Serialize};
+use serde_repr::{Deserialize_repr, Serialize_repr};
 use zeroize::{Zeroize, ZeroizeOnDrop};
 use zvariant::{Type, serialized::Context, to_bytes};
 
+#[derive(Debug, Clone, Copy, Serialize_repr, Deserialize_repr, Type, PartialEq, Eq)]
+#[repr(u8)]
+pub enum PamOperation {
+    Unlock = 0,
+    ChangePassword = 1,
+}
+
 #[derive(Debug, Serialize, Deserialize, Type, Zeroize, ZeroizeOnDrop)]
 pub struct PamMessage {
+    #[zeroize(skip)]
+    operation: PamOperation,
     pub username: String,
-    pub secret: Vec<u8>,
+    old_secret: Vec<u8>,
+    new_secret: Vec<u8>,
 }
 
 impl PamMessage {
+    /// Create an unlock message
+    pub fn unlock(username: String, secret: Vec<u8>) -> Self {
+        Self {
+            operation: PamOperation::Unlock,
+            username,
+            old_secret: Vec::new(),
+            new_secret: secret,
+        }
+    }
+
+    /// Create a password change message
+    pub fn change_password(username: String, old_secret: Vec<u8>, new_secret: Vec<u8>) -> Self {
+        Self {
+            operation: PamOperation::ChangePassword,
+            username,
+            old_secret,
+            new_secret,
+        }
+    }
+
     pub fn to_bytes(&self) -> Result<Vec<u8>, zvariant::Error> {
         let ctxt = Context::new_dbus(zvariant::LE, 0);
         to_bytes(ctxt, self).map(|data| data.to_vec())

pam/src/protocol.rs

@@ -156,11 +156,7 @@ async fn send_secret_to_daemon_async(
 
     tracing::debug!("Connected to daemon socket");
 
-    tracing::debug!(
-        "Sending secret of length {} bytes for user {}",
-        message.secret.len(),
-        message.username
-    );
+    tracing::debug!("Sending message for user {}", message.username);
     let message_bytes = Zeroizing::new(message.to_bytes().map_err(SocketError::Serialize)?);
 
     let length = message_bytes.len() as u32;
@@ -212,15 +208,12 @@ mod tests {
 
             let message = PamMessage::from_bytes(&message_bytes).unwrap();
             assert_eq!(message.username, "testuser");
-            assert_eq!(message.secret, b"testpassword");
+            assert_eq!(message.new_secret, b"testpassword");
         });
 
         tokio::time::sleep(Duration::from_millis(100)).await;
 
-        let message = PamMessage {
-            username: "testuser".to_string(),
-            secret: b"testpassword".to_vec(),
-        };
+        let message = PamMessage::unlock("testuser".to_string(), b"testpassword".to_vec());
 
         let result = send_secret_to_daemon_async(message, 1000, false).await;
         assert!(result.is_ok());

pam/src/socket.rs

@@ -25,6 +25,7 @@ openssl = { version = "0.10", optional = true }
 oo7 = { workspace = true, features = ["tokio"] }
 rpassword = "7.4"
 serde.workspace = true
+serde_repr = "0.1"
 sha2 = { version = "0.10", optional = true }
 tokio = { workspace = true, features = ["full"] }
 tokio-stream = "0.1"