dotnet/wpf · error · System.Xml.XmlException

SR.PartReferenceUriMalformed

Error message

SR.PartReferenceUriMalformed

What it means

ParsePartUriAttribute parses the SourceUri/ContentType attributes of a <Reference> in a signed manifest. If PackUriHelper.ValidatePartUri rejects the URI (or the derived content type is invalid), the code rethrows PartReferenceUriMalformed as an XmlException because the signature XML references a malformed part URI — meaning the signature is corrupt or non-conformant.

Solutions

1. Fix the producing tool to write valid OPC part URIs (PackUriHelper-compliant relative part names)
2. Validate part URIs with PackUriHelper.ValidatePartUri before writing them into signatures
3. Re-sign or regenerate the package from source since validation cannot proceed on a malformed reference
4. Treat the package signature as invalid and fall back to untrusted handling if you don't control the source

Example fix

// before (written into signature)
<Reference SourceUri="http://example.com/doc.xml" .../>
// after (valid relative OPC part URI)
<Reference SourceUri="/doc.xml" ContentType="application/xml" .../>

bool IsValidPartUri(string s) =>
    Uri.TryCreate(s, UriKind.Relative, out var u) &&
    TryGet(() => PackUriHelper.ValidatePartUri(u)) != null;
static T TryGet<T>(Func<T> f) { try { return f(); } catch { return default; } }

try { package.VerifySignatures(); }
catch (XmlException ex) when (ex.Message.Contains("malformed") || ex.Message.Contains("PartReference")) { /* mark package signature invalid */ }

When it happens

Trigger: Signature validation (via ParsePartUri -> ParsePartUriAttribute) encountering a <Reference> whose URI substring fails PackUriHelper.ValidatePartUri — e.g. illegal characters, absolute URIs where relative required, or invalid part name syntax.

Common situations: Packages signed by third-party tools writing non-canonical part names; signature XML edited or corrupted in transit; part names with characters needing escaping that weren't.

Understand the failure class

Background: "Invalid URL" errors: why new URL(), URI.parse, and reqwest::Url reject your string — missing scheme, whitespace, and bad path format — this error's family across 39 libraries.

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• SR.PackageSignatureCorruption
• SR.RequiredTagNotFound (template: RequiredTagNotFound, arg…
• SR.UnexpectedXmlTag (template: UnexpectedXmlTag, arg…
• SR.UnsupportedHashAlgorithm
• SR.XmlSignatureParseError

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/f395f651457d2fa4. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/WindowsBase/MS/Internal/IO/Packaging/XmlSignatureManifest.cs:608

            {
                try
                {
                    // ensure it starts with the correct query prefix
                    String query = attrValue.Substring(index);
                    if ((query.Length > _contentTypeQueryStringPrefix.Length) && (query.StartsWith(_contentTypeQueryStringPrefix, StringComparison.Ordinal)))
                    {
                        // truncate the prefix and validate
                        contentType = new ContentType(query.Substring(_contentTypeQueryStringPrefix.Length));
}

                    // now construct the uri without the query
                    uri = PackUriHelper.ValidatePartUri(new Uri(attrValue.Substring(0, index), UriKind.Relative));
                }
                catch (ArgumentException ae)
                {
                    // Content type or part uri is malformed so we have a bad signature.
                    // Rethrow as XmlException so outer validation loop can catch it and return validation result.
                    throw new XmlException(SR.PartReferenceUriMalformed, ae);
                }
            }

            // throw if we failed
            if (contentType.ToString().Length <= 0)
                throw new XmlException(SR.PartReferenceUriMalformed);

            return uri;
        }

        /// <summary>
        /// Generates a Reference tag that contains a Relationship transform
        /// </summary>
        /// <param name="manager">manager</param>
        /// <param name="relationshipPartName">name of the relationship part</param>
        /// <param name="xDoc">current xml document</param>
        /// <param name="hashAlgorithm">hash algorithm = digest method</param>
        /// <param name="relationshipSelectors">relationshipSelectors that represent the relationships to sign </param>

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