Make the functions FapiContext::set_callbacks() and FapiContext::clear_callbacks() return the previous callbacks instance, if any was set.

Author: danieltrick

src/callback.rs

@@ -6,7 +6,7 @@
 
 use super::{HashAlgorithm, fapi_sys::TPM2_ALG_ID, memory::CStringHolder};
 use log::trace;
-use std::{borrow::Cow, ffi::CStr, fmt::Debug};
+use std::{any::Any, borrow::Cow, ffi::CStr, fmt::Debug};
 
 // ==========================================================================
 // Callback parameters
@@ -132,46 +132,62 @@ impl<'a> PolicyActionCbParam<'a> {
 ///     }
 /// }
 /// ```
-pub trait FapiCallbacks: Debug + Send {
+pub trait FapiCallbacks: Any + Send + Debug {
     /// A callback function that allows the FAPI to request authorization values.
+    ///
+    /// The default implementation of this function returns `None`. Please override as needed!
+    ///
+    /// *See also:* [`Fapi_SetAuthCB()`](https://tpm2-tss.readthedocs.io/en/stable/group___fapi___set_auth_c_b.html)
     fn auth_cb(&self, _param: AuthCbParam) -> Option<Cow<'static, str>> {
         None
     }
 
     /// A callback function that allows the FAPI to request signatures.
     ///
     /// Signatures are requested for authorizing TPM objects.
+    ///
+    /// The default implementation of this function returns `None`. Please override as needed!
+    ///
+    /// *See also:* [`Fapi_SetSignCB()`](https://tpm2-tss.readthedocs.io/en/stable/group___fapi___set_sign_c_b.html)
     fn sign_cb(&self, _param: SignCbParam) -> Option<Vec<u8>> {
         None
     }
 
     /// A callback function that allows the FAPI to request branch choices.
     ///
     /// It is usually called during policy evaluation.
+    ///
+    /// The default implementation of this function returns `None`. Please override as needed!
+    ///
+    /// *See also:* [`Fapi_SetBranchCB()`](https://tpm2-tss.readthedocs.io/en/stable/group___fapi___set_sign_c_b.html)
     fn branch_cb(&self, _param: BranchCbParam) -> Option<usize> {
         None
     }
 
     /// A callback function that allows the FAPI to notify the application.
     ///
     /// It is usually called to announce policy actions.
+    ///
+    /// The default implementation of this function returns `false`. Please override as needed!
+    ///
+    /// *See also:* [`Fapi_SetPolicyActionCB()`](https://tpm2-tss.readthedocs.io/en/stable/group___fapi___set_sign_c_b.html)
     fn policy_action_cb(&self, _param: PolicyActionCbParam) -> bool {
         false
     }
 }
 
 // ==========================================================================
-// Callbacks wrapper
+// Callbacks manager
 // ==========================================================================
 
 #[derive(Debug)]
-pub struct Callbacks {
+pub struct CallbackManager {
     inner: Box<dyn FapiCallbacks>,
     auth_value: Option<CStringHolder>,
     sign_data: Option<Vec<u8>>,
 }
 
-impl Callbacks {
+impl CallbackManager {
     pub fn new(callbacks: impl FapiCallbacks + 'static) -> Self {
         Self { inner: Box::new(callbacks), auth_value: None, sign_data: None }
     }
@@ -185,6 +201,10 @@ impl Callbacks {
         }
     }
 
+    pub fn into_inner(self) -> Box<dyn FapiCallbacks> {
+        self.inner
+    }
+
     // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     // Callback functions
     // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -301,7 +321,7 @@ pub mod entry_point {
             },
             memory::{ptr_to_cstr_vec, ptr_to_opt_cstr},
         },
-        Callbacks,
+        CallbackManager,
     };
     use std::{
         ffi::{CStr, c_char, c_void},
@@ -321,7 +341,7 @@ pub mod entry_point {
             return mk_fapi_rc!(TSS2_BASE_RC_BAD_VALUE);
         }
         unsafe {
-            match (*(user_data as *mut Callbacks)).auth_cb(CStr::from_ptr(object_path), ptr_to_opt_cstr(description)) {
+            match (*(user_data as *mut CallbackManager)).auth_cb(CStr::from_ptr(object_path), ptr_to_opt_cstr(description)) {
                 Some(auth_value) => {
                     *auth = auth_value.as_ptr();
                     TSS2_RC_SUCCESS
@@ -356,7 +376,7 @@ pub mod entry_point {
             return mk_fapi_rc!(TSS2_BASE_RC_BAD_VALUE);
         }
         unsafe {
-            match (*(user_data as *mut Callbacks)).sign_cb(
+            match (*(user_data as *mut CallbackManager)).sign_cb(
                 CStr::from_ptr(object_path),
                 ptr_to_opt_cstr(description),
                 CStr::from_ptr(public_key),
@@ -387,7 +407,7 @@ pub mod entry_point {
             return mk_fapi_rc!(TSS2_BASE_RC_BAD_VALUE);
         }
         unsafe {
-            match (*(user_data as *mut Callbacks)).branch_cb(
+            match (*(user_data as *mut CallbackManager)).branch_cb(
                 CStr::from_ptr(object_path),
                 ptr_to_opt_cstr(description),
                 &ptr_to_cstr_vec(branch_names, num_branches)[..],
@@ -407,7 +427,7 @@ pub mod entry_point {
             return mk_fapi_rc!(TSS2_BASE_RC_BAD_VALUE);
         }
         unsafe {
-            match (*(user_data as *mut Callbacks)).policy_action_cb(CStr::from_ptr(object_path), ptr_to_opt_cstr(action)) {
+            match (*(user_data as *mut CallbackManager)).policy_action_cb(CStr::from_ptr(object_path), ptr_to_opt_cstr(action)) {
                 true => TSS2_RC_SUCCESS,
                 _ => mk_fapi_rc!(TSS2_BASE_RC_GENERAL_FAILURE),
             }

src/context.rs

@@ -9,7 +9,7 @@ use std::{ffi::c_char, fmt::Display, num::NonZeroUsize, os::raw::c_void, ptr, sy
 use crate::{
     BaseErrorCode, BlobType, ErrorCode, FapiCallbacks, ImportData, InternalError, KeyFlags, NvFlags, PaddingFlags, QuoteFlags, QuoteResult, SealFlags,
     SignResult, TpmBlobs,
-    callback::{Callbacks, entry_point},
+    callback::{CallbackManager, entry_point},
     fapi_sys::{self, FAPI_CONTEXT, TPM2_RC, TSS2_RC, constants::TSS2_RC_SUCCESS},
     flags::Flags,
     json::{self, JsonValue},
@@ -80,7 +80,7 @@ type TctiOpaqueContextBlob = *mut [u8; 0];
 #[derive(Debug)]
 pub struct FapiContext {
     native_holder: NativeContextHolder,
-    callbacks: Option<Callbacks>,
+    callbacks: Option<CallbackManager>,
 }
 
 /// A struct that wraps the native C pointer to the underlying FAPI_CONTEXT instance
@@ -148,37 +148,41 @@ impl FapiContext {
     // Callback setters
     // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-    /// This function registers application-defined callback functions with the FAPI context.
+    /// This function registers application-defined callback functions with the FAPI context, replacing any previously registered callbacks.
     ///
     /// The callback functions are implemented via the [`FapiCallbacks`](crate::FapiCallbacks) trait.
     ///
+    /// If successful, the function retruns the previously registered callback functions, which may be `None`.
+    ///
     /// *See also:*
     /// - [`Fapi_SetAuthCB()`](https://tpm2-tss.readthedocs.io/en/stable/group___fapi___set_auth_c_b.html)
     /// - [`Fapi_SetSignCB()`](https://tpm2-tss.readthedocs.io/en/stable/group___fapi___set_sign_c_b.html)
     /// - [`Fapi_SetBranchCB()`](https://tpm2-tss.readthedocs.io/en/stable/group___fapi___set_sign_c_b.html)
     /// - [`Fapi_SetPolicyActionCB()`](https://tpm2-tss.readthedocs.io/en/stable/group___fapi___set_sign_c_b.html)
-    pub fn set_callbacks(&mut self, callbacks: impl FapiCallbacks + 'static) -> Result<(), ErrorCode> {
-        let _previous = self.callbacks.replace(Callbacks::new(callbacks));
-        let callbacks_ptr = self.callbacks.as_mut().unwrap() as *mut Callbacks as *mut c_void;
+    pub fn set_callbacks(&mut self, callbacks: impl FapiCallbacks + 'static) -> Result<Option<Box<dyn FapiCallbacks>>, ErrorCode> {
+        let previous = self.callbacks.replace(CallbackManager::new(callbacks));
+        let callbacks_ptr = self.callbacks.as_mut().unwrap() as *mut CallbackManager as *mut c_void;
         let results = [
             self.fapi_call(false, |context| unsafe { fapi_sys::Fapi_SetAuthCB(context, Some(entry_point::auth_cb), callbacks_ptr) }),
             self.fapi_call(false, |context| unsafe { fapi_sys::Fapi_SetSignCB(context, Some(entry_point::sign_cb), callbacks_ptr) }),
             self.fapi_call(false, |context| unsafe { fapi_sys::Fapi_SetBranchCB(context, Some(entry_point::branch_cb), callbacks_ptr) }),
             self.fapi_call(false, |context| unsafe { fapi_sys::Fapi_SetPolicyActionCB(context, Some(entry_point::policy_action_cb), callbacks_ptr) }),
         ];
-        results.iter().try_fold((), |_acc, &result| result)
+        results.iter().try_fold(previous.map(|cb| cb.into_inner()), |acc, ret| ret.map(|_| acc))
     }
 
-    /// This function un-registers any application-defined callback functions that have been registers via the [`set_callbacks()`](FapiContext::set_callbacks) function.
-    pub fn clear_callbacks(&mut self) -> Result<(), ErrorCode> {
-        let _previous = self.callbacks.take();
+    /// This function un-registers the application-defined callback functions that have been registers via [`set_callbacks()`](FapiContext::set_callbacks).
+    ///
+    /// If successful, the function retruns the previously registered callback functions, which may be `None`.
+    pub fn clear_callbacks(&mut self) -> Result<Option<Box<dyn FapiCallbacks>>, ErrorCode> {
+        let previous = self.callbacks.take();
         let results = [
             self.fapi_call(false, |context| unsafe { fapi_sys::Fapi_SetAuthCB(context, None, ptr::null_mut()) }),
             self.fapi_call(false, |context| unsafe { fapi_sys::Fapi_SetSignCB(context, None, ptr::null_mut()) }),
             self.fapi_call(false, |context| unsafe { fapi_sys::Fapi_SetBranchCB(context, None, ptr::null_mut()) }),
             self.fapi_call(false, |context| unsafe { fapi_sys::Fapi_SetPolicyActionCB(context, None, ptr::null_mut()) }),
         ];
-        results.iter().try_fold((), |_acc, &result| result)
+        results.iter().try_fold(previous.map(|cb| cb.into_inner()), |acc, ret| ret.map(|_| acc))
     }
 
     // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

tests/03_provision_test.rs

@@ -33,8 +33,7 @@ fn test_provision() {
         };
 
         // Set up auth callback
-        let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
-        if let Err(error) = context.set_callbacks(callbacks) {
+        if let Err(error) = context.set_callbacks(MyCallbacks::new(PASSWORD, None)) {
             panic!("Setting up the callback has failed: {:?}", error)
         }
 
@@ -72,7 +71,7 @@ fn test_to_destruction() {
                 Ok(fpai_ctx) => fpai_ctx,
                 Err(error) => panic!("Failed to create context: {:?}", error),
             };
-            let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
+            let callbacks = MyCallbacks::new(PASSWORD, None);
             tpm_initialize!(context, PASSWORD, callbacks);
         }
 

tests/04_get_random_test.rs

@@ -34,8 +34,7 @@ fn test_get_random() {
         };
 
         // Initialize TPM, if not already initialized
-        let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
-        tpm_initialize!(context, PASSWORD, callbacks);
+        tpm_initialize!(context, PASSWORD, MyCallbacks::new(PASSWORD, None));
 
         // Fetch random data
         let random_data = match context.get_random(NonZeroUsize::new(128usize).unwrap()) {

tests/05_key_test.rs

@@ -42,8 +42,7 @@ fn test_create_key() {
         };
 
         // Initialize TPM, if not already initialized
-        let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
-        tpm_initialize!(context, PASSWORD, callbacks);
+        tpm_initialize!(context, PASSWORD, MyCallbacks::new(PASSWORD, None));
 
         // Create new key, if not already created
         match context.create_key(key_path, Some(KEY_FLAGS), None, Some(PASSWORD)) {
@@ -70,8 +69,7 @@ fn test_list_keys() {
         };
 
         // Initialize TPM, if not already initialized
-        let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
-        tpm_initialize!(context, PASSWORD, callbacks);
+        tpm_initialize!(context, PASSWORD, MyCallbacks::new(PASSWORD, None));
 
         // Create new key, if not already created
         for key_path in key_paths {
@@ -116,8 +114,7 @@ fn test_export_key() {
         };
 
         // Initialize TPM, if not already initialized
-        let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
-        tpm_initialize!(context, PASSWORD, callbacks);
+        tpm_initialize!(context, PASSWORD, MyCallbacks::new(PASSWORD, None));
 
         // Create new key, if not already created
         match context.create_key(key_path, Some(KEY_FLAGS), None, Some(PASSWORD)) {
@@ -164,8 +161,7 @@ fn test_import_key() {
         };
 
         // Initialize TPM, if not already initialized
-        let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
-        tpm_initialize!(context, PASSWORD, callbacks);
+        tpm_initialize!(context, PASSWORD, MyCallbacks::new(PASSWORD, None));
 
         // Import the existing public key
         match context.import(key_path, ImportData::from_pem(PUBLIC_KEY_DATA).unwrap()) {
@@ -199,8 +195,7 @@ fn test_delete() {
         };
 
         // Initialize TPM, if not already initialized
-        let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
-        tpm_initialize!(context, PASSWORD, callbacks);
+        tpm_initialize!(context, PASSWORD, MyCallbacks::new(PASSWORD, None));
 
         // Create new key, if not already created
         match context.create_key(key_path, Some(KEY_FLAGS), None, Some(PASSWORD)) {
@@ -240,8 +235,7 @@ fn test_get_tpm_blobs() {
         };
 
         // Initialize TPM, if not already initialized
-        let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
-        tpm_initialize!(context, PASSWORD, callbacks);
+        tpm_initialize!(context, PASSWORD, MyCallbacks::new(PASSWORD, None));
 
         // Create new key, if not already created
         match context.create_key(key_path, Some(KEY_FLAGS), None, Some(PASSWORD)) {
@@ -283,8 +277,7 @@ fn test_get_tpm_blobs_with_private() {
         };
 
         // Initialize TPM, if not already initialized
-        let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
-        tpm_initialize!(context, PASSWORD, callbacks);
+        tpm_initialize!(context, PASSWORD, MyCallbacks::new(PASSWORD, None));
 
         // Create new key, if not already created
         match context.create_key(key_path, Some(KEY_FLAGS), None, Some(PASSWORD)) {
@@ -331,8 +324,7 @@ fn test_get_esys_blob() {
         };
 
         // Initialize TPM, if not already initialized
-        let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
-        tpm_initialize!(context, PASSWORD, callbacks);
+        tpm_initialize!(context, PASSWORD, MyCallbacks::new(PASSWORD, None));
 
         // Create new key, if not already created
         match context.create_key(key_path, Some(KEY_FLAGS), None, Some(PASSWORD)) {

tests/06_encrypt_decrypt_test.rs

@@ -47,8 +47,7 @@ fn test_encrypt() {
         };
 
         // Initialize TPM, if not already initialized
-        let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
-        tpm_initialize!(context, PASSWORD, callbacks);
+        tpm_initialize!(context, PASSWORD, MyCallbacks::new(PASSWORD, None));
 
         // Create new key, if not already created
         match context.create_key(key_path, Some(KEY_FLAGS_ENCR), None, Some(PASSWORD)) {
@@ -92,8 +91,7 @@ fn test_decrypt() {
         };
 
         // Initialize TPM, if not already initialized
-        let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
-        tpm_initialize!(context, PASSWORD, callbacks);
+        tpm_initialize!(context, PASSWORD, MyCallbacks::new(PASSWORD, None));
 
         // Create new key, if not already created
         match context.create_key(key_path, Some(KEY_FLAGS_ENCR), None, Some(PASSWORD)) {

tests/07_signature_test.rs

@@ -49,8 +49,7 @@ fn test_sign() {
         };
 
         // Initialize TPM, if not already initialized
-        let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
-        tpm_initialize!(context, PASSWORD, callbacks);
+        tpm_initialize!(context, PASSWORD, MyCallbacks::new(PASSWORD, None));
 
         // Create new key, if not already created
         match context.create_key(key_path, Some(KEY_FLAGS_SIGN), None, Some(PASSWORD)) {
@@ -103,8 +102,7 @@ fn test_sign_with_pubkey() {
         };
 
         // Initialize TPM, if not already initialized
-        let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
-        tpm_initialize!(context, PASSWORD, callbacks);
+        tpm_initialize!(context, PASSWORD, MyCallbacks::new(PASSWORD, None));
 
         // Create new key, if not already created
         match context.create_key(key_path, Some(KEY_FLAGS_SIGN), None, Some(PASSWORD)) {
@@ -160,8 +158,7 @@ fn test_verify_signature() {
         };
 
         // Initialize TPM, if not already initialized
-        let (callbacks, _logger) = MyCallbacks::new(PASSWORD, None);
-        tpm_initialize!(context, PASSWORD, callbacks);
+        tpm_initialize!(context, PASSWORD, MyCallbacks::new(PASSWORD, None));
 
         // Create new key, if not already created
         match context.create_key(key_path, Some(KEY_FLAGS_SIGN), None, Some(PASSWORD)) {