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
                )
            try:
                handler = self.handlers[oid]
            except KeyError:
                if critical:
                    raise x509.UnsupportedExtension(
                        "Critical extension {0} is not currently supported"
                        .format(oid), oid
                    )
                else:
                    # 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:
                # For extensions which are not supported by OpenSSL we pass the
                # extension object directly to the parsing routine so it can
                # be decoded manually.
                if self.unsupported_exts and oid in self.unsupported_exts:
                    ext_data = ext
                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)