decode_asn1.py 文件源码

def parse(self, backend, x509_obj):
        extensions = []
        seen_oids = set()
        for i in range(self.ext_count(backend, x509_obj)):
            ext = self.get_ext(backend, x509_obj, i)
            backend.openssl_assert(ext != backend._ffi.NULL)
            crit = backend._lib.X509_EXTENSION_get_critical(ext)
            critical = crit == 1
            oid = x509.ObjectIdentifier(
                _obj2txt(backend, backend._lib.X509_EXTENSION_get_object(ext))
            )
            if oid in seen_oids:
                raise x509.DuplicateExtension(
                    "Duplicate {0} extension found".format(oid), oid
                )

            # This OID is only supported in OpenSSL 1.1.0+ but we want
            # to support it in all versions of OpenSSL so we decode it
            # ourselves.
            if oid == ExtensionOID.TLS_FEATURE:
                data = backend._lib.X509_EXTENSION_get_data(ext)
                parsed = _Integers.load(_asn1_string_to_bytes(backend, data))
                value = x509.TLSFeature(
                    [_TLS_FEATURE_TYPE_TO_ENUM[x.native] for x in parsed]
                )
                extensions.append(x509.Extension(oid, critical, value))
                seen_oids.add(oid)
                continue

            try:
                handler = self.handlers[oid]
            except KeyError:
                # Dump the DER payload into an UnrecognizedExtension object
                data = backend._lib.X509_EXTENSION_get_data(ext)
                backend.openssl_assert(data != backend._ffi.NULL)
                der = backend._ffi.buffer(data.data, data.length)[:]
                unrecognized = x509.UnrecognizedExtension(oid, der)
                extensions.append(
                    x509.Extension(oid, critical, unrecognized)
                )
            else:
                ext_data = backend._lib.X509V3_EXT_d2i(ext)
                if ext_data == backend._ffi.NULL:
                    backend._consume_errors()
                    raise ValueError(
                        "The {0} extension is invalid and can't be "
                        "parsed".format(oid)
                    )

                value = handler(backend, ext_data)
                extensions.append(x509.Extension(oid, critical, value))

            seen_oids.add(oid)

        return x509.Extensions(extensions)