backend.py 文件源码

def _public_key_bytes(self, encoding, format, evp_pkey, cdata):
        if not isinstance(encoding, serialization.Encoding):
            raise TypeError("encoding must be an item from the Encoding enum")

        if format is serialization.PublicFormat.SubjectPublicKeyInfo:
            if encoding is serialization.Encoding.PEM:
                write_bio = self._lib.PEM_write_bio_PUBKEY
            else:
                assert encoding is serialization.Encoding.DER
                write_bio = self._lib.i2d_PUBKEY_bio

            key = evp_pkey
        elif format is serialization.PublicFormat.PKCS1:
            # Only RSA is supported here.
            assert self._lib.Cryptography_EVP_PKEY_id(
                evp_pkey
            ) == self._lib.EVP_PKEY_RSA
            if encoding is serialization.Encoding.PEM:
                write_bio = self._lib.PEM_write_bio_RSAPublicKey
            else:
                assert encoding is serialization.Encoding.DER
                write_bio = self._lib.i2d_RSAPublicKey_bio

            key = cdata
        else:
            raise TypeError(
                "format must be an item from the PublicFormat enum"
            )

        bio = self._create_mem_bio_gc()
        res = write_bio(bio, key)
        self.openssl_assert(res == 1)
        return self._read_mem_bio(bio)