Use JSON Pointer for conceal (#10)

* use json-pointer in encoder

* fix decoding bug, improve example + README

* bump to version 0.2.0

* clippy fix

* cleanup

* fix

Author: abdulmth

CHANGELOG.md

@@ -0,0 +1,18 @@
+# Change Log
+
+## [0.2.0]
+
+### Added
+- `HEADER_TYP` constant.
+
+### Changed
+- Changed `SdObjectEncoder::conceal` to take a JSON pointer string, instead of a string array.
+
+### Removed
+- Removed `SdObjectEncoder::conceal_array_entry` (replaced by `SdObjectEncoder::conceal`).
+
+### Fixed
+- Decoding bug when objects inside arrays include digests and plain text values.
+
+## [0.1.2]
+- 07 Draft implementation.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "sd-jwt-payload"
-version = "0.1.2"
+version = "0.2.0"
 edition = "2021"
 authors = ["IOTA Stiftung"]
 homepage = "https://www.iota.org"
@@ -16,10 +16,11 @@ multibase = { version = "0.9", default-features = false, features = ["std"] }
 serde_json = { version = "1.0", default-features = false, features = ["std" ] }
 rand = { version = "0.8.5", default-features = false, features = ["std", "std_rng"] }
 thiserror = { version = "1.0", default-features = false }
-strum = { version = "0.25", default-features = false, features = ["std", "derive"] }
+strum = { version = "0.26", default-features = false, features = ["std", "derive"] }
 itertools = { version = "0.12", default-features = false, features = ["use_std"]  }
 iota-crypto = { version = "0.23", default-features = false, features = ["sha"], optional = true }
 serde = { version = "1.0", default-features = false, features = ["derive"] }
+json-pointer = "0.3.4"
 
 [dev-dependencies]
 josekit = "0.8.4"

README.md

@@ -54,7 +54,7 @@ Include the library in your `cargo.toml`.
 
 ```bash
 [dependencies]
-sd-jwt-payload = { version = "0.1.2" }
+sd-jwt-payload = { version = "0.2.0" }
 ```
 
 ## Examples
@@ -93,38 +93,42 @@ Any JSON object can be encoded
 
 
 ```rust
-  let mut encoder = SdObjectEncoder::try_from(object).unwrap();
+  let mut encoder: SdObjectEncoder = object.try_into()?;
 ```
 This creates a stateful encoder with `Sha-256` hash function by default to create disclosure digests. 
 
 *Note: `SdObjectEncoder` is generic over `Hasher` which allows custom encoding with other hash functions.*
 
-The encoder can encode any of the object's values or any array element, using the `conceal` and `conceal_array_entry` methods respectively. Suppose the value of `street_address` should be selectively disclosed as well as the value of `address` and the first `phone` value.
+The encoder can encode any of the object's values or array elements, using the `conceal` method. Suppose the value of `street_address` should be selectively disclosed as well as the value of `address` and the first `phone` value.
+
 
 ```rust
-  let disclosure1 = encoder.conceal(&["address", "street_address"], None).unwrap();
-  let disclosure2 = encoder.conceal(&["address"], None).unwrap();
-  let disclosure3 = encoder.conceal_array_entry(&["phone"], 0, None).unwrap();
+  let disclosure1 = encoder.conceal("/address/street_address"], None)?;
+  let disclosure2 = encoder.conceal("/address", None)?;
+  let disclosure3 = encoder.conceal("/phone/0", None)?;
 ```
 
 ```
 "WyJHaGpUZVYwV2xlUHE1bUNrVUtPVTkzcXV4WURjTzIiLCAic3RyZWV0X2FkZHJlc3MiLCAiMTIzIE1haW4gU3QiXQ"
 "WyJVVXVBelg5RDdFV1g0c0FRVVM5aURLYVp3cU13blUiLCAiYWRkcmVzcyIsIHsicmVnaW9uIjoiQW55c3RhdGUiLCJfc2QiOlsiaHdiX2d0eG01SnhVbzJmTTQySzc3Q194QTUxcmkwTXF0TVVLZmI0ZVByMCJdfV0"
 "WyJHRDYzSTYwUFJjb3dvdXJUUmg4OG5aM1JNbW14YVMiLCAiKzQ5IDEyMzQ1NiJd"
 ```
+*Note: the `conceal` method takes a [JSON Pointer](https://datatracker.ietf.org/doc/html/rfc6901) to determine the element to conceal inside the JSON object.*
+
+
 The encoder also supports adding decoys. For instance, the amount of phone numbers and the amount of claims need to be hidden.
 
 ```rust
-  encoder.add_decoys(&["phone"], 3).unwrap(); //Adds 3 decoys to the array `phone`.
-  encoder.add_decoys(&[], 6).unwrap(); // Adds 6 decoys to the top level object.
+  encoder.add_decoys("/phone", 3).unwrap(); //Adds 3 decoys to the array `phone`.
+  encoder.add_decoys("", 6).unwrap(); // Adds 6 decoys to the top level object.
 ```
 
 Add the hash function claim.
 ```rust
   encoder.add_sd_alg_property(); // This adds "_sd_alg": "sha-256"
 ```
 
-Now `encoder.object()` will return the encoded object.
+Now `encoder.object()?` will return the encoded object.
 
 ```json
 {
@@ -182,10 +186,10 @@ Parse the SD-JWT string to extract the JWT and the disclosures in order to decod
 *Note: Validating the signature of the JWT and extracting the claim set is outside the scope of this library.
 
 ```rust
-  let sd_jwt: SdJwt = SdJwt::parse(sd_jwt_string).unwrap();
+  let sd_jwt: SdJwt = SdJwt::parse(sd_jwt_string)?;
   let claims_set: // extract claims from `sd_jwt.jwt`.
   let decoder = SdObjectDecoder::new();
-  let decoded_object = decoder.decode(claims_set, &sd_jwt.disclosures).unwrap();
+  let decoded_object = decoder.decode(claims_set, &sd_jwt.disclosures)?;
 ```
 `decoded_object`:
 

examples/sd_jwt.rs

@@ -1,4 +1,4 @@
-// Copyright 2020-2023 IOTA Stiftung
+// Copyright 2020-2024 IOTA Stiftung
 // SPDX-License-Identifier: Apache-2.0
 
 use std::error::Error;
@@ -11,6 +11,7 @@ use sd_jwt_payload::Disclosure;
 use sd_jwt_payload::SdJwt;
 use sd_jwt_payload::SdObjectDecoder;
 use sd_jwt_payload::SdObjectEncoder;
+use sd_jwt_payload::HEADER_TYP;
 use serde_json::json;
 
 fn main() -> Result<(), Box<dyn Error>> {
@@ -37,23 +38,27 @@ fn main() -> Result<(), Box<dyn Error>> {
 
   let mut encoder: SdObjectEncoder = object.try_into()?;
   let disclosures: Vec<Disclosure> = vec![
-    encoder.conceal(&["email"], None)?,
-    encoder.conceal(&["phone_number"], None)?,
-    encoder.conceal(&["address", "street_address"], None)?,
-    encoder.conceal(&["address"], None)?,
-    encoder.conceal_array_entry(&["nationalities"], 0, None)?,
+    encoder.conceal("/email", None)?,
+    encoder.conceal("/phone_number", None)?,
+    encoder.conceal("/address/street_address", None)?,
+    encoder.conceal("/address", None)?,
+    encoder.conceal("/nationalities/0", None)?,
   ];
+
+  encoder.add_decoys("/nationalities", 3)?;
+  encoder.add_decoys("", 4)?; // Add decoys to the top level.
+
   encoder.add_sd_alg_property();
 
-  println!("encoded object: {}", serde_json::to_string_pretty(encoder.object())?);
+  println!("encoded object: {}", serde_json::to_string_pretty(encoder.object()?)?);
 
   // Create the JWT.
   // Creating JWTs is outside the scope of this library, josekit is used here as an example.
   let mut header = JwsHeader::new();
-  header.set_token_type("sd-jwt");
+  header.set_token_type(HEADER_TYP);
 
   // Use the encoded object as a payload for the JWT.
-  let payload = JwtPayload::from_map(encoder.object().clone())?;
+  let payload = JwtPayload::from_map(encoder.object()?.clone())?;
   let key = b"0123456789ABCDEF0123456789ABCDEF";
   let signer = HS256.signer_from_bytes(key)?;
   let jwt = jwt::encode_with_signer(&payload, &header, &signer)?;

src/decoder.rs

@@ -1,4 +1,4 @@
-// Copyright 2020-2023 IOTA Stiftung
+// Copyright 2020-2024 IOTA Stiftung
 // SPDX-License-Identifier: Apache-2.0
 
 use crate::ARRAY_DIGEST_KEY;
@@ -15,7 +15,7 @@ use serde_json::Map;
 use serde_json::Value;
 use std::collections::BTreeMap;
 
-/// Substitutes digests in an SD-JWT object by their corresponding plaintext values provided by disclosures.
+/// Substitutes digests in an SD-JWT object by their corresponding plain text values provided by disclosures.
 pub struct SdObjectDecoder {
   hashers: BTreeMap<String, Box<dyn Hasher>>,
 }
@@ -54,7 +54,7 @@ impl SdObjectDecoder {
   }
 
   /// Decodes an SD-JWT `object` containing by Substituting the digests with their corresponding
-  /// plaintext values provided by `disclosures`.
+  /// plain text values provided by `disclosures`.
   ///
   /// ## Notes
   /// * The hasher is determined by the `_sd_alg` property. If none is set, the sha-256 hasher will
@@ -227,6 +227,7 @@ impl SdObjectDecoder {
           } else {
             let decoded_object = self.decode_object(object, disclosures, processed_digests)?;
             output.push(Value::Object(decoded_object));
+            break;
           }
         }
       } else if let Some(arr) = value.as_array() {
@@ -265,12 +266,16 @@ mod test {
       "id": "did:value",
     });
     let mut encoder = SdObjectEncoder::try_from(object).unwrap();
-    let dis = encoder.conceal(&["id"], None).unwrap();
+    let dis = encoder.conceal("/id", None).unwrap();
     encoder
-      .object_mut()
+      .object
+      .as_object_mut()
+      .unwrap()
       .insert("id".to_string(), Value::String("id-value".to_string()));
     let decoder = SdObjectDecoder::new_with_sha256();
-    let decoded = decoder.decode(encoder.object(), &vec![dis.to_string()]).unwrap_err();
+    let decoded = decoder
+      .decode(encoder.object().unwrap(), &vec![dis.to_string()])
+      .unwrap_err();
     assert!(matches!(decoded, Error::ClaimCollisionError(_)));
   }
 
@@ -284,9 +289,9 @@ mod test {
     });
     let mut encoder = SdObjectEncoder::try_from(object).unwrap();
     encoder.add_sd_alg_property();
-    assert_eq!(encoder.object().get("_sd_alg").unwrap(), "sha-256");
+    assert_eq!(encoder.object().unwrap().get("_sd_alg").unwrap(), "sha-256");
     let decoder = SdObjectDecoder::new_with_sha256();
-    let decoded = decoder.decode(encoder.object(), &vec![]).unwrap();
+    let decoded = decoder.decode(encoder.object().unwrap(), &vec![]).unwrap();
     assert!(decoded.get("_sd_alg").is_none());
   }
 
@@ -296,7 +301,7 @@ mod test {
       "id": "did:value",
     });
     let mut encoder = SdObjectEncoder::try_from(object).unwrap();
-    let dislosure: Disclosure = encoder.conceal(&["id"], Some("test".to_string())).unwrap();
+    let dislosure: Disclosure = encoder.conceal("/id", Some("test".to_string())).unwrap();
     // 'obj' contains digest of `id` twice.
     let obj = json!({
       "_sd":[
@@ -317,8 +322,8 @@ mod test {
       "tst": "tst-value"
     });
     let mut encoder = SdObjectEncoder::try_from(object).unwrap();
-    let disclosure_1: Disclosure = encoder.conceal(&["id"], Some("test".to_string())).unwrap();
-    let disclosure_2: Disclosure = encoder.conceal(&["tst"], Some("test".to_string())).unwrap();
+    let disclosure_1: Disclosure = encoder.conceal("/id", Some("test".to_string())).unwrap();
+    let disclosure_2: Disclosure = encoder.conceal("/tst", Some("test".to_string())).unwrap();
     // 'obj' contains only the digest of `id`.
     let obj = json!({
       "_sd":[