(PureBasic) 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.

For more information, see https://www.ietf.org/rfc/rfc3161.txt

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IncludeFile "CkBinData.pb"
IncludeFile "CkAsn.pb"
IncludeFile "CkHttp.pb"
IncludeFile "CkXml.pb"
IncludeFile "CkCrypt2.pb"
IncludeFile "CkStringBuilder.pb"
IncludeFile "CkHttpResponse.pb"

Procedure ChilkatExample()

    ; 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"
    success.i
    crypt.i = CkCrypt2::ckCreate()
    If crypt.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkCrypt2::setCkHashAlgorithm(crypt, "sha256")
    CkCrypt2::setCkEncodingMode(crypt, "base64")
    base64Hash.s = CkCrypt2::ckHashFileENC(crypt,"qa_data/hamlet.xml")

    http.i = CkHttp::ckCreate()
    If http.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    requestToken.i = CkBinData::ckCreate()
    If requestToken.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    optionalPolicyOid.s = ""
    addNonce.i = 0
    requestTsaCert.i = 1

    ; Create a time-stamp request token
    success = CkHttp::ckCreateTimestampRequest(http,"sha256",base64Hash,optionalPolicyOid,addNonce,requestTsaCert,requestToken)
    If success = 0
        Debug CkHttp::ckLastErrorText(http)
        CkCrypt2::ckDispose(crypt)
        CkHttp::ckDispose(http)
        CkBinData::ckDispose(requestToken)
        ProcedureReturn
    EndIf

    ; 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
    tsaUrl.s = "http://timestamp.digicert.com"
    resp.i = CkHttp::ckPBinaryBd(http,"POST",tsaUrl,requestToken,"application/timestamp-query",0,0)
    If CkHttp::ckLastMethodSuccess(http) = 0
        Debug CkHttp::ckLastErrorText(http)
        CkCrypt2::ckDispose(crypt)
        CkHttp::ckDispose(http)
        CkBinData::ckDispose(requestToken)
        ProcedureReturn
    EndIf

    ; Get the timestamp reply from the HTTP response object.
    timestampReply.i = CkBinData::ckCreate()
    If timestampReply.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkHttpResponse::ckGetBodyBd(resp,timestampReply)
    CkHttpResponse::ckDispose(resp)

    ; Convert the binary timestamp reply to XML
    asn.i = CkAsn::ckCreate()
    If asn.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkAsn::ckLoadBd(asn,timestampReply)
    If success = 0
        Debug CkAsn::ckLastErrorText(asn)
        CkCrypt2::ckDispose(crypt)
        CkHttp::ckDispose(http)
        CkBinData::ckDispose(requestToken)
        CkBinData::ckDispose(timestampReply)
        CkAsn::ckDispose(asn)
        ProcedureReturn
    EndIf

    xml.i = CkXml::ckCreate()
    If xml.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkXml::ckLoadXml(xml,CkAsn::ckAsnToXml(asn))

    ; 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  }

    tstInfoBase64.s = CkXml::ckGetChildContent(xml,"sequence[1]|contextSpecific|sequence|sequence|contextSpecific|octets")

    bdTstInfo.i = CkBinData::ckCreate()
    If bdTstInfo.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkBinData::ckAppendEncoded(bdTstInfo,tstInfoBase64,"base64")

    asnTstInfo.i = CkAsn::ckCreate()
    If asnTstInfo.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkAsn::ckLoadBd(asnTstInfo,bdTstInfo)
    If success = 0
        Debug CkAsn::ckLastErrorText(asnTstInfo)
        CkCrypt2::ckDispose(crypt)
        CkHttp::ckDispose(http)
        CkBinData::ckDispose(requestToken)
        CkBinData::ckDispose(timestampReply)
        CkAsn::ckDispose(asn)
        CkXml::ckDispose(xml)
        CkBinData::ckDispose(bdTstInfo)
        CkAsn::ckDispose(asnTstInfo)
        ProcedureReturn
    EndIf

    xmlTstInfo.i = CkXml::ckCreate()
    If xmlTstInfo.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkXml::ckLoadXml(xmlTstInfo,CkAsn::ckAsnToXml(asnTstInfo))
    Debug CkXml::ckGetXml(xmlTstInfo)

    ; 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

    sbGenTime.i = CkStringBuilder::ckCreate()
    If sbGenTime.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkStringBuilder::ckDecodeAndAppend(sbGenTime,CkXml::ckGetChildContent(xmlTstInfo,"universal"),"base64","utf-8")
    Debug CkStringBuilder::ckGetAsString(sbGenTime)

    ; Result:
    ; 20230316115718Z


    CkCrypt2::ckDispose(crypt)
    CkHttp::ckDispose(http)
    CkBinData::ckDispose(requestToken)
    CkBinData::ckDispose(timestampReply)
    CkAsn::ckDispose(asn)
    CkXml::ckDispose(xml)
    CkBinData::ckDispose(bdTstInfo)
    CkAsn::ckDispose(asnTstInfo)
    CkXml::ckDispose(xmlTstInfo)
    CkStringBuilder::ckDispose(sbGenTime)


    ProcedureReturn
EndProcedure