ssh.py

# Copyright 2023 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Utility for ssh."""

import dataclasses

from airflow.decorators import task
from airflow.models import Variable
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import rsa


@dataclasses.dataclass
class SshKeys:
  """Represents a pair of SSH keys."""

  private: str
  public: str
  user: str


@task
def generate_ssh_keys() -> SshKeys:
  """Generate an RSA key pair in the OpenSSH format."""
  key = rsa.generate_private_key(
      public_exponent=65537,
      key_size=2048,
  )

  private_key = key.private_bytes(
      serialization.Encoding.PEM,
      serialization.PrivateFormat.OpenSSH,
      serialization.NoEncryption(),
  )
  public_key = key.public_key().public_bytes(
      serialization.Encoding.OpenSSH, serialization.PublicFormat.OpenSSH
  )

  return SshKeys(
      private=private_key.decode(),
      public=public_key.decode(),
      user="ml-auto-solutions",
  )


@task
def obtain_persist_ssh_keys() -> SshKeys:
  """Obtain persistent SSH keys and user from Airflow Variables."""
  try:
    user = Variable.get("os-login-ssh-user")
    private_key = Variable.get("os-login-ssh-private-key")
    public_key = Variable.get("os-login-ssh-public-key")
  except KeyError as e:
    raise ValueError(
        f"Required Airflow Variable {e} is not set. "
        "Please ensure 'os-login-ssh-user', 'os-login-ssh-private-key', "
        "and 'os-login-ssh-public-key' are configured."
    ) from e

  return SshKeys(private=private_key, public=public_key, user=user)