Make underlying plumbing more generic (#54)

* Turn into box

* Use Trait instead of type

* WIP

* Change import

* Add logs

* Add logging deps

* Logger

* Temp COSE change

* COSE handling

* WIP

* Clean up

* Python UDL mapping

* Add export

* Add a fucntion

* Missing export

* One more api change

* Revert wrapping

* Restore mistakenly removed file

* Undo wrapping

* Add more logs

* Add alg support

* Make alg param optional

* API changes to simplify

* Fix typings in UDL

* Update bindings

* Remove env_logger init

* Clean up logs

* Add pytest to Linux action for testing

* Pytest attempt 2

* Remove maturin from workflow

* Update build.yml

* Clean up API

* Add code doc

* Fix doc

.github/workflows/build.yml

@@ -55,7 +55,6 @@ jobs:
                 # If we're running on debian-based system.
                 apt update -y && apt-get install -y libssl-dev openssl pkg-config
             fi
-
       - name: Upload wheels
         uses: actions/upload-artifact@v3
         with:

Cargo.toml

@@ -19,6 +19,8 @@ serde_json = "1.0"
 thiserror = "1.0.49"
 uniffi = "0.24.1"
 openssl-src = "=300.3.1" # Required for openssl-sys
+log = "0.4.21"
+env_logger = "0.11.3"
 
 [build-dependencies]
 uniffi = { version = "0.24.1", features = ["build"] }

README.md

@@ -333,6 +333,8 @@ pip install -U pytest
 python3 -m build --wheel
 ```
 
+Note: To peek at the Python code (uniffi generated and non-generated), run `maturin develop` and look in the c2pa folder.
+
 ### ManyLinux build
 
 Build using [manylinux](https://github.com/pypa/manylinux) by using a Docker image as follows:

c2pa/__init__.py

@@ -11,7 +11,7 @@
 # specific language governing permissions and limitations under
 # each license.
 
-from .c2pa_api import Reader, Builder, create_signer, sign_ps256
+from .c2pa_api import Reader, Builder, create_signer, create_remote_signer, sign_ps256
 from .c2pa import Error, SigningAlg, sdk_version, version
 
-__all__ = ['Reader', 'Builder', 'create_signer', 'sign_ps256', 'Error', 'SigningAlg', 'sdk_version', 'version']
+__all__ = ['Reader', 'Builder', 'create_signer', 'sign_ps256', 'Error', 'SigningAlg', 'sdk_version', 'version', 'create_remote_signer']

c2pa/c2pa_api/c2pa_api.py

@@ -23,7 +23,6 @@
 sys.path.append(SOURCE_PATH)
 
 import c2pa.c2pa as api
-#from c2pa import Error, SigningAlg, version, sdk_version
 
 # This module provides a simple Python API for the C2PA library.
 
@@ -134,7 +133,6 @@ def sign_file(self, signer, sourcePath, outputPath):
         return super().sign_file(signer, sourcePath, outputPath)
 
 
-
 # Implements a C2paStream given a stream handle
 # This is used to pass a file handle to the c2pa library
 # It is used by the Reader and Builder classes internally
@@ -166,6 +164,7 @@ def flush_stream(self) -> None:
     def open_file(path: str, mode: str) -> api.Stream:
         return C2paStream(open(path, mode))
 
+
 # Internal class to implement signer callbacks
 # We need this because the callback expects a class with a sign method
 class SignerCallback(api.SignerCallback):
@@ -193,7 +192,37 @@ def __init__(self, callback):
 def create_signer(callback, alg, certs, timestamp_url=None):
     return api.CallbackSigner(SignerCallback(callback), alg, certs, timestamp_url)
 
-
+# Because we "share" SigningAlg enum in-between bindings,
+# seems we need to manually coerce the enum types,
+# like unffi itself does too
+def convert_to_alg(alg):
+    match str(alg):
+        case "SigningAlg.ES256":
+            return api.SigningAlg.ES256
+        case "SigningAlg.ES384":
+            return api.SigningAlg.ES384
+        case "SigningAlg.ES512":
+            return api.SigningAlg.ES512
+        case "SigningAlg.PS256":
+            return api.SigningAlg.PS256
+        case "SigningAlg.PS384":
+            return api.SigningAlg.PS384
+        case "SigningAlg.PS512":
+            return api.SigningAlg.PS512
+        case "SigningAlg.ED25519":
+            return api.SigningAlg.ED25519
+        case _:
+            raise ValueError("Unsupported signing algorithm: " + str(alg))
+
+# Creates a special case signer that uses direct COSE handling
+# The callback signer should also define the signing algorithm to use
+# And a way to find out the needed reserve size
+def create_remote_signer(callback):
+    return api.CallbackSigner.new_from_signer(
+        callback,
+        convert_to_alg(callback.alg()),
+        callback.reserve_size()
+    )
 
 # Example of using openssl in an os shell to sign data using Ps256
 # Note: the openssl command line tool must be installed for this to work

src/c2pa.udl

@@ -74,6 +74,9 @@ callback interface SignerCallback {
 
 interface CallbackSigner {
   constructor(SignerCallback callback, SigningAlg alg, bytes certs, string? ta_url);
+
+  [Name=new_from_signer]
+  constructor(SignerCallback callback, SigningAlg alg, u32 reserve_size);
 };
 
 interface Builder {

src/callback_signer.rs

@@ -10,7 +10,8 @@
 // specific language governing permissions and limitations under
 // each license.
 
-use c2pa::SigningAlg;
+use c2pa::{SigningAlg, Signer};
+use log::debug;
 
 use crate::Result;
 
@@ -24,7 +25,36 @@ pub trait SignerCallback: Send + Sync {
 ///
 /// Uniffi callbacks are only supported as a method in a structure, so this is a workaround
 pub struct CallbackSigner {
-    signer: c2pa::CallbackSigner,
+    signer: Box<dyn Signer + Sync + Send>,
+}
+
+pub struct RemoteSigner {
+    signer_callback : Box<dyn SignerCallback>,
+    alg: SigningAlg,
+    reserve_size: u32,
+}
+
+impl c2pa::Signer for RemoteSigner {
+  fn alg(&self) -> SigningAlg {
+      self.alg
+  }
+
+  fn certs(&self) -> c2pa::Result<Vec<Vec<u8>>> {
+      Ok(Vec::new())
+  }
+
+  // signer will return a COSE structure
+  fn direct_cose_handling(&self) -> bool {
+      true
+  }
+
+  fn sign(&self, data: &[u8]) -> c2pa::Result<Vec<u8>> {
+      self.signer_callback.sign(data.to_vec()).map_err(|e| c2pa::Error::BadParam(e.to_string()))
+  }
+
+  fn reserve_size(&self) -> usize {
+      self.reserve_size as usize // TODO: Find better conversion for usize
+  }
 }
 
 impl CallbackSigner {
@@ -45,11 +75,27 @@ impl CallbackSigner {
         if let Some(url) = ta_url {
             signer = signer.set_tsa_url(url);
         }
-        Self { signer }
+
+        Self { signer: Box::new(signer) }
+    }
+
+    pub fn new_from_signer(
+      callback: Box<dyn SignerCallback>,
+      alg: SigningAlg,
+      reserve_size: u32,
+    ) -> Self {
+        debug!("c2pa-python: CallbackSigner -> new_from_signer");
+        let signer = RemoteSigner {
+            signer_callback: callback,
+            alg,
+            reserve_size
+        };
+
+        Self { signer: Box::new(signer) }
     }
 
     /// The python Builder wrapper sign function calls this
-    pub fn signer(&self) -> &c2pa::CallbackSigner {
+    pub fn signer(&self) -> &Box<dyn c2pa::Signer + Sync + Send> {
         &self.signer
     }
 }

src/lib.rs

@@ -134,7 +134,7 @@ impl Builder {
         Ok(())
     }
 
-    /// Set to true to disable embedding a manifest 
+    /// Set to true to disable embedding a manifest
     pub fn set_no_embed(&self) -> Result<()> {
         if let Ok(mut builder) = self.builder.try_write() {
             builder.set_no_embed(true);
@@ -214,7 +214,7 @@ impl Builder {
         let mut dest = StreamAdapter::from(dest);
         if let Ok(mut builder) = self.builder.try_write() {
             let signer = (*signer).signer();
-            Ok(builder.sign(signer, format, &mut source, &mut dest)?)
+            Ok(builder.sign(signer.as_ref(), format, &mut source, &mut dest)?)
         } else {
             Err(Error::RwLock)
         }
@@ -224,7 +224,7 @@ impl Builder {
     pub fn sign_file(&self, signer: &CallbackSigner, source: &str, dest: &str) -> Result<Vec<u8>> {
         if let Ok(mut builder) = self.builder.try_write() {
             let signer = (*signer).signer();
-            Ok(builder.sign_file(signer, source, dest)?)
+            Ok(builder.sign_file(signer.as_ref(), source, dest)?)
         } else {
             Err(Error::RwLock)
         }