在python中使用pexpect的“ ssh-keygen -t rsa”未按预期生成公共文件

Question

While executing the "ssh-keygen -t rsa" command using pexpect in python, the command doesn't generate the "id_rsa.pub" file as expected, sometimes the .ssh folder will be empty and sometimes contains the "known hosts" file.

Following is the python code snippet:

import pexpect
command = 'ssh-keygen -t rsa'
print command
child = pexpect.spawn(command)
child.delaybeforesend=5
file_prompt = 'Enter file'
pwd_prompt = 'passphrase'
empty_string = '\n'
res = child.expect([pexpect.EOF,pexpect.TIMEOUT,file_prompt])
child.sendline(empty_string)
res = child.expect([pexpect.EOF,pexpect.TIMEOUT,pwd_prompt])
child.sendline(empty_string)
res = child.expect([pexpect.EOF,pexpect.TIMEOUT,pwd_prompt])
child.sendline(empty_string)
res = child.expect([pexpect.TIMEOUT,'$'])
child.close()

The same when executed line by line on the interpreter..everything goes fine. It generates the id_rsa.pub file as expected.

Tried out several runs but still could not figure out the reason for the same. I added the :

child.delaybeforesend=5

only to make sure that the key generation is completing. Please help on this.

Below is the reference command prompt :

[tecmint@tecmint.com ~]$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/tecmint/.ssh/id_rsa): [Pressenter 
key]
Created directory '/home/tecmint/.ssh'.
Enter passphrase (empty for no passphrase): [Press enter key]
Enter same passphrase again: [Press enter key]
Your identification has been saved in /home/tecmint/.ssh/id_rsa.
Your public key has been saved in /home/tecmint/.ssh/id_rsa.pub.
The key fingerprint is:
5f:ad:40:00:8a:d1:9b:99:b3:b0:f8:08:99:c3:ed:d3 tecmint@tecmint.com
The key's randomart image is:

With my context:

.ssh folder is either empty or contains "known_hosts" file when i run the code snippet.

and when I run the same code , line by line on the interpreter, it generates the id_rsa and the id_rsa.pub

Answer 1

You are not waiting for the prompt ssh-keygen is sending so pexpect doesn't know to send the passphrase. Adjust your prompt .