Chilkat2-Python

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. Chilkat2-Python

import sys
import chilkat2

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"

crypt = chilkat2.Crypt2()
crypt.HashAlgorithm = "sha256"
crypt.EncodingMode = "base64"
base64Hash = crypt.HashFileENC("qa_data/hamlet.xml")

http = chilkat2.Http()

requestToken = chilkat2.BinData()
optionalPolicyOid = ""
addNonce = False
requestTsaCert = True

# Create a time-stamp request token
success = http.CreateTimestampRequest("sha256",base64Hash,optionalPolicyOid,addNonce,requestTsaCert,requestToken)
if (success == False):
    print(http.LastErrorText)
    sys.exit()

# 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 = "http://timestamp.digicert.com"
resp = chilkat2.HttpResponse()
success = http.HttpBd("POST",tsaUrl,requestToken,"application/timestamp-query",resp)
if (success == False):
    print(http.LastErrorText)
    sys.exit()

# Get the timestamp reply from the HTTP response object.
timestampReply = chilkat2.BinData()
resp.GetBodyBd(timestampReply)

# Convert the binary timestamp reply to XML
asn = chilkat2.Asn()
success = asn.LoadBd(timestampReply)
if (success == False):
    print(asn.LastErrorText)
    sys.exit()

xml = chilkat2.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  }

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

bdTstInfo = chilkat2.BinData()
bdTstInfo.AppendEncoded(tstInfoBase64,"base64")

asnTstInfo = chilkat2.Asn()
success = asnTstInfo.LoadBd(bdTstInfo)
if (success == False):
    print(asnTstInfo.LastErrorText)
    sys.exit()

xmlTstInfo = chilkat2.Xml()
success = xmlTstInfo.LoadXml(asnTstInfo.AsnToXml())
print(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

sbGenTime = chilkat2.StringBuilder()
sbGenTime.DecodeAndAppend(xmlTstInfo.GetChildContent("universal"),"base64","utf-8")
print(sbGenTime.GetAsString())

# Result:
# 20230316115718Z