如何生成 SSH 代理签名响应

Question

我正在写一个内部管理系统，也需要实现一个SSH代理。到目前为止，我已经正确地实现了 SSH_AGENTC_REQUEST_IDENTITIES 和 SSH_AGENT_IDENTITIES_ANSWER，这导致 SSH 然后按照 https://tools.ietf.org/id/draft-miller-ssh-agent-00.html

发送 SSH_AGENTC_SIGN_REQUEST

我的问题是弄清楚如何签署请求，此时我只需要支持ssh-rsa。我已尝试按照 https://www.rfc-editor.org/rfc/rfc4253 实施此操作，但我似乎无法生成将进行身份验证的回复。

根据我对本规范的理解，SSH_AGENTC_SIGN_REQUEST 消息的整个数据部分需要使用 RSASSA-PKCS1-v1_5

进行签名

这是接收请求的代码

if msgType == SSH_AGENTC_SIGN_REQUEST:
  blobLen = struct.unpack('!I', sock.recv(4))[0]
  blob    = sock.recv(blobLen)
  dataLen = struct.unpack('!I', sock.recv(4))[0]
  data    = sock.recv(dataLen)
  flags   = struct.unpack('!I', sock.recv(4))[0]

  print("blob: %s\ndata: %s\n flags: %d" % (blob, data, flags))

  if base64.b64decode(server["public_key"]) != blob:
    sock.sendall(struct.pack('!IB', 1, SSH_AGENT_FAILURE))
    continue

  signed = rpc.root.signSSHData(server_id, data)
  if not signed:
    sock.sendall(struct.pack('!IB', 1, SSH_AGENT_FAILURE))
    continue

  buff = bytearray()
  buff.extend(struct.pack('!B', SSH_AGENT_SIGN_RESPONSE))
  packBytes(buff, bytes("ssh-rsa", "UTF-8"))
  packBytes(buff, signed)
  head = struct.pack('!I', len(buff))

  sock.sendall(head);
  sock.sendall(buff);

这里是rpc.root.signSSHData的来源：

  def exposed_signSSHData(self, server_id, data):
    query = "SELECT private_key FROM servers WHERE deleted = 0 AND id = %s LIMIT 1"
    cursor = self.core.getDBC().cursor()
    cursor.execute(query, (server_id, ))
    row    = cursor.fetchone();
    if row is None:
      cursor.close()
      return False

    key    = self.core.decryptData(row[0])
    key    = RSA.importKey(key);
    h      = SHA.new(data)
    signer = PKCS1_v1_5.new(key)
    return signer.sign(h)

更新 1： 我相信我可能已经弄明白了，似乎 data 是 RFC4252 中定义的 SSH_MSG_USERAUTH_REQUEST。我会更新我的应用程序，看看进展如何。

Answer 1

我找到了解决方法，回复的格式不正确，下面是更正后的代码：

if msgType == SSH_AGENTC_SIGN_REQUEST:
  blobLen = struct.unpack('!I', sock.recv(4))[0]
  blob    = sock.recv(blobLen)
  dataLen = struct.unpack('!I', sock.recv(4))[0]
  data    = sock.recv(dataLen)
  flags   = struct.unpack('!I', sock.recv(4))[0]

  if base64.b64decode(server["public_key"]) != blob:
    sock.sendall(struct.pack('!IB', 1, SSH_AGENT_FAILURE))
    continue

  sig = rpc.root.signSSHData(server_id, data);
  if not sig:
    sock.sendall(struct.pack('!IB', 1, SSH_AGENT_FAILURE))
    continue

  signature = bytearray()
  packBytes(signature, bytes("ssh-rsa", "UTF-8"))
  packBytes(signature, sig)

  buff = bytearray()
  buff.extend(struct.pack('!B', SSH_AGENT_SIGN_RESPONSE))
  packBytes(buff, signature)
  head = struct.pack('!I', len(buff))

  sock.sendall(head);
  sock.sendall(buff);
  continue

如何生成 SSH 代理签名响应

How do I generate the SSH agent sign response

python

ssh

rsa

pycrypto

ssh-agent