C#

Extract TSTInfo from RFC3161 Timestamp Reply

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Sends an RFC 3161 timestamp request to a TSA (Timestamp Authority) server and converts the timestamp reply to XML, and then extracts the TSTInfo from the XML and converts it to XML. C#

bool success = false;

//  Note: Requires Chilkat v9.5.0.75 or greater.

//  This requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

//  First sha-256 hash the data that is to be timestamped.
//  In this example, the data is the string "Hello World"

Chilkat.Crypt2 crypt = new Chilkat.Crypt2();
crypt.HashAlgorithm = "sha256";
crypt.EncodingMode = "base64";
string base64Hash = crypt.HashFileENC("qa_data/hamlet.xml");

Chilkat.Http http = new Chilkat.Http();

Chilkat.BinData requestToken = new Chilkat.BinData();
string optionalPolicyOid = "";
bool addNonce = false;
bool requestTsaCert = true;

//  Create a time-stamp request token
success = http.CreateTimestampRequest("sha256",base64Hash,optionalPolicyOid,addNonce,requestTsaCert,requestToken);
if (success == false) {
    Debug.WriteLine(http.LastErrorText);
    return;
}

//  Send the time-stamp request token to the TSA.
//  This is the equivalent of the following CURL command:
//  curl -H "Content-Type: application/timestamp-query" --data-binary '@file.tsq' http://timestamp.digicert.com > file.tsr
string tsaUrl = "http://timestamp.digicert.com";
Chilkat.HttpResponse resp = new Chilkat.HttpResponse();
success = http.HttpBd("POST",tsaUrl,requestToken,"application/timestamp-query",resp);
if (success == false) {
    Debug.WriteLine(http.LastErrorText);
    return;
}

//  Get the timestamp reply from the HTTP response object.
Chilkat.BinData timestampReply = new Chilkat.BinData();
resp.GetBodyBd(timestampReply);

//  Convert the binary timestamp reply to XML
Chilkat.Asn asn = new Chilkat.Asn();
success = asn.LoadBd(timestampReply);
if (success == false) {
    Debug.WriteLine(asn.LastErrorText);
    return;
}

Chilkat.Xml xml = new Chilkat.Xml();
success = xml.LoadXml(asn.AsnToXml());

//  Extract the TSTInfo from the XML.
//  The TSTInfo is this base64 encoded ASN.1 

//  TSTInfo ::= SEQUENCE  {
//     version                      INTEGER  { v1(1) },
//     policy                       TSAPolicyId,
//     messageImprint               MessageImprint,
//       -- MUST have the same value as the similar field in
//       -- TimeStampReq
//     serialNumber                 INTEGER,
//      -- Time-Stamping users MUST be ready to accommodate integers
//      -- up to 160 bits.
//     genTime                      GeneralizedTime,
//     accuracy                     Accuracy                 OPTIONAL,
//     ordering                     BOOLEAN             DEFAULT FALSE,
//     nonce                        INTEGER                  OPTIONAL,
//       -- MUST be present if the similar field was present
//       -- in TimeStampReq.  In that case it MUST have the same value.
//     tsa                          [0] GeneralName          OPTIONAL,
//     extensions                   [1] IMPLICIT Extensions   OPTIONAL  }

string tstInfoBase64 = xml.GetChildContent("sequence[1]|contextSpecific|sequence|sequence|contextSpecific|octets");

Chilkat.BinData bdTstInfo = new Chilkat.BinData();
bdTstInfo.AppendEncoded(tstInfoBase64,"base64");

Chilkat.Asn asnTstInfo = new Chilkat.Asn();
success = asnTstInfo.LoadBd(bdTstInfo);
if (success == false) {
    Debug.WriteLine(asnTstInfo.LastErrorText);
    return;
}

Chilkat.Xml xmlTstInfo = new Chilkat.Xml();
success = xmlTstInfo.LoadXml(asnTstInfo.AsnToXml());
Debug.WriteLine(xmlTstInfo.GetXml());

//  Here's the TSTInfo XML:

//  <?xml version="1.0" encoding="utf-8"?>
//  <sequence>
//      <int>01</int>
//      <oid>2.16.840.1.114412.7.1</oid>
//      <sequence>
//          <sequence>
//              <oid>2.16.840.1.101.3.4.2.1</oid>
//              <null/>
//          </sequence>
//          <octets>4sRRyWOzC7EOic4fQ9+Op1pa10DbgoBGjBvkq09LZmE=</octets>
//      </sequence>
//      <int>00AD2C86E49872597B60F87D5C54BCFFAE</int>
//      <universal tag="24" constructed="0">MjAyMzAzMTYxMTQ5NTJa</universal>
//  </sequence>

//     The genTime (GeneralizedTime) is contained in the final "universal" XML element and is 
//     in base64. It is the time at which the time-stamp token has been created by
//     the TSA. After decoding from base64, it is:
//  
//     The syntax is: YYYYMMDDhhmmss[.s...]Z
//     Example: 19990609001326.34352Z

Chilkat.StringBuilder sbGenTime = new Chilkat.StringBuilder();
sbGenTime.DecodeAndAppend(xmlTstInfo.GetChildContent("universal"),"base64","utf-8");
Debug.WriteLine(sbGenTime.GetAsString());

//  Result:
//  20230316115718Z