dotnet/wpf · error · ArgumentException

SR.PackageSpecificReferenceTagMustBeUnique

Error message

SR.PackageSpecificReferenceTagMustBeUnique

What it means

ValidateReferences walks the signature's <Reference> elements. Per the OPC spec there must be exactly one package-specific reference (URI equal to the OpcLinkAttrValue) pointing at the package <Object>. If such a reference is encountered where package-specific references are not allowed, ArgumentException(SR.PackageSpecificReferenceTagMustBeUnique) is thrown.

Solutions

  1. Re-sign the package with PackageDigitalSignatureManager.Sign so references are structured per the OPC profile.
  2. Remove the package-specific <Reference> from the part-level reference set; it must exist only in the allowed group.
  3. Inspect the signature's SignedXml Reference URIs and fix the one using the OpcLink value.
  4. Reject/strip non-conformant third-party signatures before verification.

Example fix

// before: package-specific reference among part refs
<Reference URI="#idPackageObject">...</Reference>  <!-- inside part manifest refs -->
// after: re-sign correctly
var dsm = new PackageDigitalSignatureManager(pkg);
dsm.Sign(toSign, cert); // places the package Object reference per OPC spec
Defensive patterns

Strategy: validation

Validate before calling

// Scan part-level references for the package-specific URI before Verify
var opcUri = "#idPackageObject"; // XTable.OpcLinkAttrValue
var badRefs = doc.SelectNodes("//*[local-name()='Reference']/@URI")
    .Cast<XmlAttribute>()
    .Where(a => a.Value == opcUri);
// only the allowed group may contain it; >0 elsewhere is invalid

Type guard

static bool NoOpcLinkInPartRefs(IEnumerable<string> partRefUris, string opcUri) =>
    !partRefUris.Contains(opcUri);

Try / catch

try { dsm.VerifySignatures(true); }
catch (ArgumentException ex) { /* misplaced package-specific reference — reject/re-sign */ }

Prevention

When it happens

Trigger: Verifying a signature or adding custom object tags when a <Reference> with the package-specific URI appears in a reference set that forbids it — e.g. a part-level reference list contains a reference to the package Object instead of a real part URI.

Common situations: Custom signing code that adds a package-specific reference into the wrong reference group; signatures crafted by third-party tools that mix part references and package Object references; verifying signatures not produced by the OPC-aware .NET signer.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/62d6922b86fbb34a. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/WindowsBase/MS/Internal/IO/Packaging/XmlDigitalSignatureProcessor.cs:1179

        private void ValidateReferences(IEnumerable references, bool allowPackageSpecificReferences)
        {
            Debug.Assert(references != null);

            bool packageReferenceFound = false;
            TransformChain currentTransformChain;

            foreach (Reference currentReference in references)
            {
                //As per the OPC spec, Uri attribute in Reference elements MUST refer using fragment identifiers
                //This implies that Uri cannot be absolute.
                if (currentReference.Uri.StartsWith("#", StringComparison.Ordinal))
                {
                    //As per the OPC spec, there MUST be exactly one package specific reference to the 
                    //package specific <Object> element 
                    if (string.Equals(currentReference.Uri, XTable.Get(XTable.ID.OpcLinkAttrValue), StringComparison.Ordinal))
                    {
                        if (!allowPackageSpecificReferences)
                            throw new ArgumentException(SR.PackageSpecificReferenceTagMustBeUnique);

                        //If there are more than one package specific tags
                        if (packageReferenceFound)
                            throw new XmlException(SR.MoreThanOnePackageSpecificReference);
                        else
                            packageReferenceFound = true;
                    }

                    currentTransformChain = currentReference.TransformChain;

                    for(int j=0; j<currentTransformChain.Count; j++)
                    {
                        //As per the OPC spec, only two transforms are supported for the reference tags
                        if (!IsValidXmlCanonicalizationTransform(currentTransformChain[j].Algorithm))
                            throw new XmlException(SR.UnsupportedTransformAlgorithm);
                    }
                }
                else

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