Certificate revocation lists (CRLs), Online Certificate Status Protocol (OCSP) structures, and Certificate Signing Requests (CSRs). These components are essential for PKI certificate lifecycle management, including certificate issuance, status checking, and revocation handling.
Structures for handling certificate revocation information.
class CertificateList(core.Sequence):
"""
Certificate Revocation List structure (RFC 5280).
Contains information about revoked certificates issued by a CA.
Structure:
tbsCertList: TBSCertList - CRL information
signatureAlgorithm: AlgorithmIdentifier - Signature algorithm
signature: BIT STRING - CRL signature
"""
@property
def issuer(self):
"""Get the CRL issuer name."""
@property
def this_update(self):
"""Get the CRL issue date."""
@property
def next_update(self):
"""Get the next scheduled CRL update date."""
@property
def revoked_certificates(self):
"""Get the list of revoked certificates."""
@property
def extensions(self):
"""Get the CRL extensions."""
@property
def signature_algorithm(self):
"""Get the signature algorithm."""
@property
def signature(self):
"""Get the signature value."""
class TBSCertList(core.Sequence):
"""
To-Be-Signed Certificate List structure.
Contains the actual CRL data that is signed by the CA.
Structure:
version: INTEGER OPTIONAL - CRL version
signature: AlgorithmIdentifier - Signature algorithm
issuer: Name - CRL issuer
thisUpdate: Time - CRL issue time
nextUpdate: Time OPTIONAL - Next CRL update time
revokedCertificates: RevokedCertificates OPTIONAL - Revoked certs
crlExtensions: Extensions OPTIONAL - CRL extensions
"""
class RevokedCertificate(core.Sequence):
"""
Individual revoked certificate entry.
Structure:
userCertificate: INTEGER - Certificate serial number
revocationDate: Time - Revocation date
crlEntryExtensions: Extensions OPTIONAL - Entry extensions
"""
@property
def user_certificate(self):
"""Get the revoked certificate serial number."""
@property
def revocation_date(self):
"""Get the revocation date."""
@property
def extensions(self):
"""Get the entry extensions."""
@property
def reason_code(self):
"""Get the revocation reason code (if present)."""
class RevokedCertificates(core.SequenceOf):
"""
Sequence of revoked certificate entries.
"""Structures for real-time certificate status checking.
class OCSPRequest(core.Sequence):
"""
OCSP Request structure (RFC 6960).
Used to query the status of certificates from an OCSP responder.
Structure:
tbsRequest: TBSRequest - Request information
optionalSignature: Signature OPTIONAL - Request signature
"""
@property
def tbs_request(self):
"""Get the to-be-signed request data."""
@property
def optional_signature(self):
"""Get the optional request signature."""
class TBSRequest(core.Sequence):
"""
To-Be-Signed OCSP Request structure.
Structure:
version: INTEGER OPTIONAL - Request version
requestorName: GeneralName OPTIONAL - Requestor identification
requestList: RequestList - List of certificate status requests
requestExtensions: Extensions OPTIONAL - Request extensions
"""
@property
def version(self):
"""Get the request version."""
@property
def requestor_name(self):
"""Get the requestor name."""
@property
def request_list(self):
"""Get the list of certificate requests."""
@property
def request_extensions(self):
"""Get the request extensions."""
class Request(core.Sequence):
"""
Single certificate status request.
Structure:
reqCert: CertID - Certificate identifier
singleRequestExtensions: Extensions OPTIONAL - Request extensions
"""
@property
def req_cert(self):
"""Get the certificate identifier."""
@property
def single_request_extensions(self):
"""Get the single request extensions."""
class CertID(core.Sequence):
"""
Certificate identifier for OCSP requests.
Structure:
hashAlgorithm: AlgorithmIdentifier - Hash algorithm
issuerNameHash: OCTET STRING - Hash of issuer name
issuerKeyHash: OCTET STRING - Hash of issuer key
serialNumber: INTEGER - Certificate serial number
"""
@property
def hash_algorithm(self):
"""Get the hash algorithm."""
@property
def issuer_name_hash(self):
"""Get the issuer name hash."""
@property
def issuer_key_hash(self):
"""Get the issuer key hash."""
@property
def serial_number(self):
"""Get the certificate serial number."""
class OCSPResponse(core.Sequence):
"""
OCSP Response structure (RFC 6960).
Contains the response from an OCSP responder.
Structure:
responseStatus: OCSPResponseStatus - Response status
responseBytes: ResponseBytes OPTIONAL - Response data
"""
@property
def response_status(self):
"""Get the response status."""
@property
def response_bytes(self):
"""Get the response bytes."""
@property
def basic_ocsp_response(self):
"""Get the basic OCSP response (if present)."""
class BasicOCSPResponse(core.Sequence):
"""
Basic OCSP Response structure.
Structure:
tbsResponseData: ResponseData - Response data
signatureAlgorithm: AlgorithmIdentifier - Signature algorithm
signature: BIT STRING - Response signature
certs: Certificates OPTIONAL - Response certificates
"""
@property
def tbs_response_data(self):
"""Get the to-be-signed response data."""
@property
def signature_algorithm(self):
"""Get the signature algorithm."""
@property
def signature(self):
"""Get the signature value."""
@property
def certs(self):
"""Get the response certificates."""
class ResponseData(core.Sequence):
"""
OCSP Response data structure.
Structure:
version: INTEGER OPTIONAL - Response version
responderID: ResponderID - Responder identifier
producedAt: GeneralizedTime - Response production time
responses: Responses - Certificate status responses
responseExtensions: Extensions OPTIONAL - Response extensions
"""
@property
def version(self):
"""Get the response version."""
@property
def responder_id(self):
"""Get the responder identifier."""
@property
def produced_at(self):
"""Get the response production time."""
@property
def responses(self):
"""Get the certificate status responses."""
class SingleResponse(core.Sequence):
"""
Single certificate status response.
Structure:
certID: CertID - Certificate identifier
certStatus: CertStatus - Certificate status
thisUpdate: GeneralizedTime - Status update time
nextUpdate: GeneralizedTime OPTIONAL - Next update time
singleExtensions: Extensions OPTIONAL - Response extensions
"""
@property
def cert_id(self):
"""Get the certificate identifier."""
@property
def cert_status(self):
"""Get the certificate status."""
@property
def this_update(self):
"""Get the status update time."""
@property
def next_update(self):
"""Get the next update time."""Structures for certificate enrollment and renewal.
class CertificationRequest(core.Sequence):
"""
Certificate Signing Request structure (RFC 2986).
Used to request certificate issuance from a Certificate Authority.
Structure:
certificationRequestInfo: CertificationRequestInfo - Request info
signatureAlgorithm: AlgorithmIdentifier - Signature algorithm
signature: BIT STRING - Request signature
"""
@property
def certification_request_info(self):
"""Get the certification request information."""
@property
def signature_algorithm(self):
"""Get the signature algorithm."""
@property
def signature(self):
"""Get the signature value."""
@property
def subject(self):
"""Get the requested certificate subject."""
@property
def public_key(self):
"""Get the public key to be certified."""
@property
def attributes(self):
"""Get the request attributes."""
class CertificationRequestInfo(core.Sequence):
"""
Certificate Request Information structure.
Structure:
version: INTEGER - Request version
subject: Name - Requested subject name
subjectPKInfo: SubjectPublicKeyInfo - Public key info
attributes: Attributes - Request attributes
"""
@property
def version(self):
"""Get the request version."""
@property
def subject(self):
"""Get the subject name."""
@property
def subject_pk_info(self):
"""Get the subject public key info."""
@property
def attributes(self):
"""Get the request attributes."""
class CRIAttributes(core.SetOf):
"""
Certificate Request Information attributes.
Set of attributes that can be included in a CSR.
"""from asn1crypto import crl, pem
# Load CRL from file
with open('ca.crl', 'rb') as f:
crl_data = f.read()
# Handle PEM encoding if present
if pem.detect(crl_data):
_, _, crl_der = pem.unarmor(crl_data)
else:
crl_der = crl_data
# Parse the CRL
certificate_list = crl.CertificateList.load(crl_der)
# Access CRL information
print(f"Issuer: {certificate_list.issuer.human_friendly}")
print(f"This Update: {certificate_list.this_update}")
print(f"Next Update: {certificate_list.next_update}")
print(f"Signature Algorithm: {certificate_list.signature_algorithm}")
# Check revoked certificates
if certificate_list.revoked_certificates:
print(f"Number of revoked certificates: {len(certificate_list.revoked_certificates)}")
for revoked in certificate_list.revoked_certificates:
print(f"Serial: {revoked.user_certificate}")
print(f"Revocation Date: {revoked.revocation_date}")
# Check for reason code extension
if revoked.reason_code:
print(f"Reason: {revoked.reason_code}")
else:
print("No certificates are revoked")
# Check CRL extensions
for extension in certificate_list.extensions:
print(f"Extension: {extension['extn_id'].dotted}")
if extension['critical']:
print(" (Critical)")from asn1crypto import ocsp, x509, algos
import hashlib
# Assuming we have a certificate and its issuer
cert = x509.Certificate.load(cert_der)
issuer_cert = x509.Certificate.load(issuer_der)
# Create certificate identifier for OCSP request
issuer_name_hash = hashlib.sha1(issuer_cert.subject.dump()).digest()
issuer_key_hash = hashlib.sha1(issuer_cert.public_key.dump()).digest()
cert_id = ocsp.CertID({
'hash_algorithm': algos.DigestAlgorithm('sha1'),
'issuer_name_hash': issuer_name_hash,
'issuer_key_hash': issuer_key_hash,
'serial_number': cert.serial_number
})
# Create single certificate request
single_request = ocsp.Request({
'req_cert': cert_id
})
# Create TBS request
tbs_request = ocsp.TBSRequest({
'request_list': [single_request]
})
# Create complete OCSP request
ocsp_request = ocsp.OCSPRequest({
'tbs_request': tbs_request
})
# Serialize for transmission
request_der = ocsp_request.dump()
print(f"OCSP request size: {len(request_der)} bytes")from asn1crypto import ocsp
# Parse OCSP response (assuming we received response_der from server)
response = ocsp.OCSPResponse.load(response_der)
# Check response status
print(f"Response Status: {response.response_status}")
if response.response_status == 'successful':
# Get basic OCSP response
basic_response = response.basic_ocsp_response
response_data = basic_response.tbs_response_data
print(f"Responder ID: {response_data.responder_id}")
print(f"Produced At: {response_data.produced_at}")
# Check individual certificate responses
for single_response in response_data.responses:
cert_id = single_response.cert_id
status = single_response.cert_status
print(f"Certificate Serial: {cert_id.serial_number}")
print(f"Status: {status.name}")
print(f"This Update: {single_response.this_update}")
if single_response.next_update:
print(f"Next Update: {single_response.next_update}")
# Handle different status types
if status.name == 'good':
print("Certificate is valid")
elif status.name == 'revoked':
revoked_info = status.chosen
print(f"Revoked on: {revoked_info['revocation_time']}")
if 'revocation_reason' in revoked_info:
print(f"Reason: {revoked_info['revocation_reason']}")
elif status.name == 'unknown':
print("Certificate status unknown")from asn1crypto import csr, pem
# Load CSR from file
with open('request.csr', 'rb') as f:
csr_data = f.read()
# Handle PEM encoding
if pem.detect(csr_data):
_, _, csr_der = pem.unarmor(csr_data)
else:
csr_der = csr_data
# Parse the CSR
cert_request = csr.CertificationRequest.load(csr_der)
# Access CSR information
print(f"Subject: {cert_request.subject.human_friendly}")
print(f"Public Key Algorithm: {cert_request.public_key.algorithm}")
print(f"Key Size: {cert_request.public_key.bit_size} bits")
print(f"Signature Algorithm: {cert_request.signature_algorithm}")
# Check CSR attributes
for attribute in cert_request.attributes:
attr_type = attribute['type'].dotted
print(f"Attribute: {attr_type}")
# Handle extension requests (common in CSRs)
if attr_type == '1.2.840.113549.1.9.14': # Extension request
extension_request = attribute['values'][0]
for extension in extension_request:
print(f" Requested Extension: {extension['extn_id'].dotted}")
if extension['critical']:
print(" (Critical)")
# Verify CSR signature (basic check - full verification requires crypto library)
print(f"Signature present: {len(cert_request.signature) > 0}")from asn1crypto import csr, x509, keys, core
# Assuming we have a private key and want to create a CSR
# (Note: Actual signing requires a crypto library like cryptography)
# Define the subject name
subject = x509.Name([
[{'type': 'common_name', 'value': 'example.com'}],
[{'type': 'organization_name', 'value': 'Example Corp'}],
[{'type': 'country_name', 'value': 'US'}]
])
# Create subject public key info (from private key)
# This example assumes you have the public key info available
public_key_info = keys.PublicKeyInfo.load(public_key_der)
# Create extension request for Subject Alternative Names
san_extension = core.Extension({
'extn_id': '2.5.29.17', # Subject Alternative Name
'critical': False,
'extn_value': x509.GeneralNames([
x509.GeneralName('dns_name', 'example.com'),
x509.GeneralName('dns_name', 'www.example.com')
])
})
# Create extension request attribute
ext_request = core.Attribute({
'type': '1.2.840.113549.1.9.14', # Extension request
'values': [core.Extensions([san_extension])]
})
# Create certification request info
csr_info = csr.CertificationRequestInfo({
'version': 0,
'subject': subject,
'subject_pk_info': public_key_info,
'attributes': [ext_request]
})
# Create the complete CSR structure (signature would be added by crypto library)
cert_request = csr.CertificationRequest({
'certification_request_info': csr_info,
'signature_algorithm': {'algorithm': 'sha256_rsa'},
'signature': b'\\x00' # Placeholder - real signature needed
})
print(f"CSR created for: {cert_request.subject.human_friendly}")These components work together in a complete PKI system: