fix: Fix label handling for custom metadata (#1354)

mauricefisher64 · web-flow · commit 9fc179e1914b · 2025-08-28T16:29:02.000-04:00
* Fix label handling for custom metadata

* fix integration test

* Fix builder metadata usage to allow custom metadata to pass through

* Fix wasm warning

* Code simplification

* Update to the corrected exifEx namespace

* More exifEx fixes

* Add backcompat support since there has been some cleanup of the namespaces
diff --git a/sdk/src/assertions/exif.rs b/sdk/src/assertions/exif.rs
@@ -44,7 +44,7 @@ impl Exif {
         Self {
             object_context: Some(json!({
               "dc": "http://purl.org/dc/elements/1.1/",
-              "exifEX": "http://cipa.jp/exif/2.32/",
+              "exifEX": "http://cipa.jp/exif/1.0/",
               "exif": "http://ns.adobe.com/exif/1.0/",
               "tiff": "http://ns.adobe.com/tiff/1.0/",
               "xmp": "http://ns.adobe.com/xap/1.0/",
@@ -138,7 +138,7 @@ pub mod tests {
     const SPEC_EXAMPLE: &str = r#"{
         "@context" : {
           "dc": "http://purl.org/dc/elements/1.1/",
-          "exifEX": "http://cipa.jp/exif/2.32/",
+          "exifEX": "http://cipa.jp/exif/1.0/",
           "exif": "http://ns.adobe.com/exif/1.0/",
           "tiff": "http://ns.adobe.com/tiff/1.0/",
           "xmp": "http://ns.adobe.com/xap/1.0/",
diff --git a/sdk/src/assertions/metadata.rs b/sdk/src/assertions/metadata.rs
@@ -22,6 +22,8 @@ use crate::{
     Error,
 };
 
+const ASSERTION_CREATION_VERSION: usize = 1;
+
 /// A `Metadata` assertion provides structured metadata using JSON-LD format for
 /// both standardized C2PA metadata and custom metadata schemas.
 ///
@@ -38,21 +40,29 @@ pub struct Metadata {
     /// Metadata fields with namespace prefixes.
     #[serde(flatten)]
     pub value: HashMap<String, Value>,
-    /// Assertion label (not serialized).
+
+    /// Custom assertion label (not serialized into content).
     #[serde(skip)]
-    pub label: String,
+    custom_metadata_label: Option<String>,
 }
 
 impl Metadata {
     /// Creates a new metadata assertion from a JSON-LD string.
-    pub fn new(label: &str, jsonld: &str) -> Result<Self, Error> {
+    pub fn new(metadata_label: &str, jsonld: &str) -> Result<Self, Error> {
         let metadata = serde_json::from_slice::<Metadata>(jsonld.as_bytes())
             .map_err(|e| Error::BadParam(format!("Invalid JSON format: {e}")))?;
 
+        // is this a standard c2pa.metadata assertion or a custom field
+        let custom_metadata_label = if metadata_label != labels::METADATA {
+            Some(metadata_label.to_owned())
+        } else {
+            None
+        };
+
         Ok(Self {
             context: metadata.context,
             value: metadata.value,
-            label: label.to_owned(),
+            custom_metadata_label,
         })
     }
 
@@ -67,11 +77,18 @@ impl Metadata {
             return false;
         }
 
-        if self.label == labels::METADATA {
+        if self.label() == labels::METADATA {
             for (namespace, uri) in &self.context {
                 if let Some(expected_uri) = ALLOWED_SCHEMAS.get(namespace.as_str()) {
                     if uri != expected_uri {
-                        return false;
+                        // check the backcompat list
+                        if let Some(bcl) = BACKCOMPAT_LIST.get(namespace.as_str()) {
+                            if !bcl.iter().any(|v| v == uri) {
+                                return false;
+                            }
+                        } else {
+                            return false;
+                        }
                     }
                 }
             }
@@ -83,19 +100,30 @@ impl Metadata {
                     return false;
                 }
             }
-            if self.label == labels::METADATA && !ALLOWED_FIELDS.contains(&label.as_str()) {
+            if self.label() == labels::METADATA && !ALLOWED_FIELDS.contains(&label.as_str()) {
                 return false;
             }
         }
         true
     }
+
+    /// Get the label for the metadata
+    pub fn get_label(&self) -> &str {
+        self.label()
+    }
 }
 
 impl AssertionJson for Metadata {}
 
 impl AssertionBase for Metadata {
+    const LABEL: &'static str = labels::METADATA;
+    const VERSION: Option<usize> = Some(ASSERTION_CREATION_VERSION);
+
     fn label(&self) -> &str {
-        &self.label
+        match &self.custom_metadata_label {
+            Some(cm) => cm,
+            None => Self::LABEL,
+        }
     }
 
     fn to_assertion(&self) -> Result<Assertion, Error> {
@@ -104,7 +132,10 @@ impl AssertionBase for Metadata {
 
     fn from_assertion(assertion: &Assertion) -> Result<Self, Error> {
         let mut metadata = Self::from_json_assertion(assertion)?;
-        metadata.label = assertion.label().to_owned();
+
+        metadata.custom_metadata_label =
+            (assertion.label() != labels::METADATA).then(|| assertion.label().to_owned());
+
         Ok(metadata)
     }
 }
@@ -122,14 +153,21 @@ lazy_static! {
         ("dc", "http://purl.org/dc/elements/1.1/"),
         ("Iptc4xmpExt", "http://iptc.org/std/Iptc4xmpExt/2008-02-29/"),
         ("exif", "http://ns.adobe.com/exif/1.0/"),
-        ("exifEX", "http://cipa.jp/exif/1.0/exifEX"),
+        ("exifEX", "http://cipa.jp/exif/1.0/"),
         ("photoshop", "http://ns.adobe.com/photoshop/1.0/"),
         ("tiff", "http://ns.adobe.com/tiff/1.0/"),
         ("xmpDM", "http://ns.adobe.com/xmp/1.0/DynamicMedia/"),
         ("plus", "http://ns.useplus.org/ldf/xmp/1.0/"),
     ]
     .into_iter()
     .collect();
+
+    // list is to support versions that have changed since the current spec
+    static ref BACKCOMPAT_LIST: HashMap<&'static str, Vec<&'static str>> = vec![
+        ("exifEX", vec!["http://cipa.jp/exif/1.0/exifEX", "http://cipa.jp/exif/2.32/"])
+    ]
+    .into_iter()
+    .collect();
 }
 
 /// The c2pa.metadata assertion shall only contain certain fields.
@@ -459,7 +497,7 @@ pub mod tests {
     const SPEC_EXAMPLE: &str = r#"{
         "@context" : {
             "exif": "http://ns.adobe.com/exif/1.0/",
-            "exifEX": "http://cipa.jp/exif/1.0/exifEX",
+            "exifEX": "http://cipa.jp/exif/1.0/",
             "tiff": "http://ns.adobe.com/tiff/1.0/",
             "Iptc4xmpExt": "http://iptc.org/std/Iptc4xmpExt/2008-02-29/",
             "photoshop" : "http://ns.adobe.com/photoshop/1.0/"
@@ -537,6 +575,25 @@ pub mod tests {
         }
         "#;
 
+    const BACKCOMPAT: &str = r#" {
+        "@context" : {
+            "exif": "http://ns.adobe.com/exif/1.0/",
+            "exifEX": "http://cipa.jp/exif/2.32/",
+            "tiff": "http://ns.adobe.com/tiff/1.0/",
+            "Iptc4xmpExt": "http://iptc.org/std/Iptc4xmpExt/2008-02-29/",
+            "photoshop" : "http://ns.adobe.com/photoshop/1.0/"
+        },
+        "photoshop:DateCreated": "Aug 31, 2022",
+        "Iptc4xmpExt:DigitalSourceType": "https://cv.iptc.org/newscodes/digitalsourcetype/digitalCapture",
+        "exif:GPSVersionID": "2.2.0.0",
+        "exif:GPSLatitude": "39,21.102N",
+        "exif:GPSLongitude": "74,26.5737W",
+        "exif:GPSAltitudeRef": 0,
+        "exif:GPSAltitude": "100963/29890",
+        "exifEX:LensSpecification": { "@list": [ 1.55, 4.2, 1.6, 2.4 ] }
+    }
+    "#;
+
     #[test]
     fn metadata_from_json() {
         let metadata = Metadata::new(METADATA, SPEC_EXAMPLE).unwrap();
@@ -551,12 +608,26 @@ pub mod tests {
         assert_eq!(metadata, result);
     }
 
+    #[test]
+    fn backcompat() {
+        let metadata = Metadata::new(METADATA, BACKCOMPAT).unwrap();
+        assert!(metadata.is_valid());
+    }
+
+    #[test]
+    fn assertion_custom_round_trip() {
+        let metadata = Metadata::new("custom.metadata", CUSTOM_METADATA).unwrap();
+        let assertion = metadata.to_assertion().unwrap();
+        let result = Metadata::from_assertion(&assertion).unwrap();
+        assert_eq!(metadata, result);
+    }
+
     #[test]
     fn test_custom_validation() {
         let mut metadata = Metadata::new("custom.metadata", CUSTOM_METADATA).unwrap();
         assert!(metadata.is_valid());
         // c2pa.metadata has restrictions on fields
-        metadata.label = METADATA.to_owned();
+        metadata.custom_metadata_label = Some(METADATA.to_owned());
         assert!(!metadata.is_valid());
     }
 
@@ -570,7 +641,7 @@ pub mod tests {
     fn test_field_not_in_context() {
         let mut metadata = Metadata::new("custom.metadata", MISSING_CONTEXT).unwrap();
         assert!(!metadata.is_valid());
-        metadata.label = METADATA.to_owned();
+        metadata.custom_metadata_label = Some(METADATA.to_owned());
         assert!(!metadata.is_valid());
     }
 
@@ -579,7 +650,7 @@ pub mod tests {
         let mut metadata = Metadata::new(METADATA, MISMATCH_URI).unwrap();
         assert!(!metadata.is_valid());
         // custom metadata does not have restriction on uris
-        metadata.label = "custom.metadata".to_owned();
+        metadata.custom_metadata_label = Some("custom.metadata".to_owned());
         assert!(metadata.is_valid());
     }
 
diff --git a/sdk/src/builder.rs b/sdk/src/builder.rs
@@ -26,15 +26,14 @@ use serde_with::skip_serializing_none;
 use uuid::Uuid;
 use zip::{write::SimpleFileOptions, ZipArchive, ZipWriter};
 
+use crate::assertion::AssertionBase;
 #[allow(deprecated)]
 use crate::{
     assertion::AssertionDecodeError,
     assertions::{
-        c2pa_action,
-        labels::{self, METADATA_LABEL_REGEX},
-        Action, ActionTemplate, Actions, AssertionMetadata, BmffHash, BoxHash, CreativeWork,
-        DataHash, DigitalSourceType, EmbeddedData, Exif, Metadata, SoftwareAgent, Thumbnail, User,
-        UserCbor,
+        c2pa_action, labels, Action, ActionTemplate, Actions, AssertionMetadata, BmffHash, BoxHash,
+        CreativeWork, DataHash, DigitalSourceType, EmbeddedData, Exif, Metadata, SoftwareAgent,
+        Thumbnail, User, UserCbor,
     },
     cbor_types::value_cbor_to_type,
     claim::Claim,
@@ -1006,7 +1005,8 @@ impl Builder {
                     let bmff_hash: BmffHash = manifest_assertion.to_assertion()?;
                     claim.add_assertion_with_salt(&bmff_hash, &salt)
                 }
-                l if METADATA_LABEL_REGEX.is_match(l) => {
+                Metadata::LABEL => {
+                    // user metadata will go through the fallback path
                     let metadata: Metadata = manifest_assertion.to_assertion()?;
                     claim.add_gathered_assertion_with_salt(&metadata, &salt)
                 }
diff --git a/sdk/src/utils/io_utils.rs b/sdk/src/utils/io_utils.rs
@@ -22,7 +22,7 @@ use std::{
 #[allow(unused)] // different code path for WASI
 use tempfile::{tempdir, Builder, NamedTempFile, SpooledTempFile, TempDir};
 
-use crate::{asset_io::rename_or_move, settings::get_settings_value, Error, Result};
+use crate::{asset_io::rename_or_move, Error, Result};
 // Replace data at arbitrary location and len in a file.
 // start_location is where the replacement data will start
 // replace_len is how many bytes from source to replaced starting a start_location
@@ -127,7 +127,7 @@ fn stream_with_fs_fallback_wasm(
 
 #[cfg(not(target_arch = "wasm32"))]
 fn stream_with_fs_fallback_file_io(threshold_override: Option<usize>) -> Result<SpooledTempFile> {
-    let threshold = threshold_override.unwrap_or(get_settings_value::<usize>(
+    let threshold = threshold_override.unwrap_or(crate::settings::get_settings_value::<usize>(
         "core.backing_store_memory_threshold_in_mb",
     )?);
 
@@ -452,8 +452,10 @@ mod tests {
         assert!(!stream.is_rolled(), "data still in memory");
 
         let large_data = vec![0; 1024 * 1024]; // 1MB.
-        let threshold =
-            get_settings_value::<usize>("core.backing_store_memory_threshold_in_mb").unwrap();
+        let threshold = crate::settings::get_settings_value::<usize>(
+            "core.backing_store_memory_threshold_in_mb",
+        )
+        .unwrap();
 
         for _ in 0..threshold {
             stream.write_all(&large_data).unwrap();
diff --git a/sdk/tests/integration.rs b/sdk/tests/integration.rs
@@ -279,8 +279,14 @@ mod integration_1 {
         let custom_metadata_assertion = Metadata::new("custom.foo.metadata", CUSTOM_METADATA)?;
 
         // add metadata assertions
-        builder.add_assertion_json(&c2pa_metadata_assertion.label, &c2pa_metadata_assertion)?;
-        builder.add_assertion_json(&custom_metadata_assertion.label, &custom_metadata_assertion)?;
+        builder.add_assertion_json(
+            c2pa_metadata_assertion.get_label(),
+            &c2pa_metadata_assertion,
+        )?;
+        builder.add_assertion_json(
+            custom_metadata_assertion.get_label(),
+            &custom_metadata_assertion,
+        )?;
 
         // sign and embed into the target file
         let signer = Settings::signer()?;
diff --git a/sdk/tests/v2_api_integration.rs b/sdk/tests/v2_api_integration.rs
@@ -96,7 +96,7 @@ mod integration_v2 {
                 "data": {
                     "@context" : {
                         "exif": "http://ns.adobe.com/exif/1.0/",
-                        "exifEX": "http://cipa.jp/exif/2.32/",
+                        "exifEX": "http://cipa.jp/exif/1.0/",
                         "tiff": "http://ns.adobe.com/tiff/1.0/",
                         "Iptc4xmpExt": "http://iptc.org/std/Iptc4xmpExt/2008-02-29/",
                         "photoshop" : "http://ns.adobe.com/photoshop/1.0/"
