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(C#) Verify XML Signature with External URL ReferencesDemonstrates how to verify an XML digital signature that includes references to URLs where the data to be digested is on a web server.
// This example requires the Chilkat API to have been previously unlocked. // See Global Unlock Sample for sample code. // The signed XML we wish to verify contains external references such as this: // <ds:Reference Id="xmldsig-e7ae7ce2-9133-4d56-bd97-0a6aef738cc2-ref0" URI="https://www.chilkatsoft.com/images/starfish.jpg"> // <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/> // <ds:DigestValue>AOU810yJV5Np/DnO29qpObqiTSTTCDvxGsX5ayiTYXI=</ds:DigestValue> // </ds:Reference> // <ds:Reference Id="xmldsig-e7ae7ce2-9133-4d56-bd97-0a6aef738cc2-ref1" URI="https://www.chilkatsoft.com/hamlet.xml"> // <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/> // <ds:DigestValue>4sRRyWOzC7EOic4fQ9+Op1pa10DbgoBGjBvkq09LZmE=</ds:DigestValue> // </ds:Reference> Chilkat.XmlDSig verifier = new Chilkat.XmlDSig(); Chilkat.Http http = new Chilkat.Http(); // First load the signed XML Chilkat.StringBuilder sbSignedXml = new Chilkat.StringBuilder(); bool success = sbSignedXml.LoadFile("qa_data/xml_dsig_verify/signedWithExternalUrlRefs.xml","utf-8"); if (success == false) { Debug.WriteLine("Failed to load signed XML."); return; } success = verifier.LoadSignatureSb(sbSignedXml); if (success == false) { Debug.WriteLine(verifier.LastErrorText); return; } // Iterate over each reference. If it is an external URL reference, download the data and provide it to the verifier. Chilkat.StringBuilder sbRefUri = new Chilkat.StringBuilder(); Chilkat.BinData bd = new Chilkat.BinData(); int numRefs = verifier.NumReferences; int i = 0; while (i < numRefs) { if (verifier.IsReferenceExternal(i) == true) { sbRefUri.Clear(); sbRefUri.Append(verifier.ReferenceUri(i)); if (sbRefUri.StartsWith("https://",false) == true) { Debug.WriteLine("External URL Reference: " + sbRefUri.GetAsString()); // Download the data at the URL and provide to the verifier. success = http.DownloadBd(sbRefUri.GetAsString(),bd); if (success == false) { Debug.WriteLine(http.LastErrorText); return; } success = verifier.SetRefDataBd(i,bd); if (success == false) { Debug.WriteLine(verifier.LastErrorText); return; } } } i = i + 1; } // Now that we have the external data, verify the signature.. bool bVerified = verifier.VerifySignature(true); if (bVerified == false) { Debug.WriteLine(verifier.LastErrorText); } Debug.WriteLine("Signature verified = " + Convert.ToString(bVerified)); |
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