This is the first time I am using python so please help... :)
This telnet script works fine for me if I know the correct password, but the router on 192.168.1.1 will sometimes boot up with the password: password1 and sometimes with the password: password2, and I need the script to be fully automated so passwords need to be read directly from the script because I want to telnet and log to router no matter if the password is the first or the second one.
import telnetlib
import time
router = '192.168.1.1'
password = 'password1'
username = 'admin'
tn = telnetlib.Telnet(router)
tn.read_until(b"Login: ")
tn.write(username.encode("ascii") + b"\n")
tn.read_until(b"Password: ")
tn.write(password.encode('ascii') + b"\n")
print("Successfully connected to %s" % router)
tn.write(b"sh ip int bri\n")
time.sleep(2)
print (type("output"))
output = tn.read_very_eager()
#print(output)
output_formatted = output.decode('utf-8')
print(output_formatted)
print("done")`
How can I modify this code, to make it try out a second password if the first one was not correct, in order to be successfully logged in via telnet in both cases (password1 or password2)?
After writing the first password, tn.write(password...), you need to determine what output corresponds to a correct login. For example, this might be a command prompt ending in "ok >". For an incorrect password, you need to detect output corresponding to another password prompt, for example "Password:" again, or starting again from "Login: ".
You can then use telnetlib's expect() method to look simultaneously for these 2 outputs by putting them in a list, eg ["ok >", "Password: "]. See pydoc telnetlib. This method returns a tuple (index in list, match object, text read till match). The only item of interest is the first, the index; it will be 0 if "ok >" was seen, 1 if "Password: " was seen, or -1 if neither was seen by some given timeout. You just need to test this value and proceed appropriately.
index, match, text = tn.expect([b"ok >", b"Password: "], timeout=10)
if index==-1:
... # oops, timeout
elif index==1:
... # need to send password2
else:
... # ok, logged in
Note, the strings passed to expect() are compiled into regular expressions, so beware of using special characters (see pydoc re).