54 lines
1.9 KiB
Python
54 lines
1.9 KiB
Python
#!/usr/bin/python3
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#
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# This script implement's Dovecot's checkpassword authentication mechanism:
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# http://wiki2.dovecot.org/AuthDatabase/CheckPassword?action=show&redirect=PasswordDatabase%2FCheckPassword
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#
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# This allows us to perform our own password validation, such as for two-factor authentication,
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# which Dovecot does not have any native support for.
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#
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# We will issue an HTTP request to our management server to perform authentication.
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import sys, os, urllib.request, base64, json, traceback
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try:
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# Read fd 3 which provides the username and password separated
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# by NULLs and two other undocumented/empty fields.
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creds = b''
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while True:
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b = os.read(3, 1024)
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if len(b) == 0: break
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creds += b
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email, pw, dummy, dummy = creds.split(b'\x00')
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# Call the management server's "/me" method with the
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# provided credentials
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req = urllib.request.Request('http://127.0.0.1:10222/me')
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req.add_header(b'Authorization', b'Basic ' + base64.b64encode(email + b':' + pw))
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response = urllib.request.urlopen(req)
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# The response is always success and always a JSON object
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# indicating the authentication result.
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resp = response.read().decode('utf8')
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resp = json.loads(resp)
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if not isinstance(resp, dict): raise ValueError("Response is not a JSON object.")
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except:
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# Handle all exceptions. Print what happens (ends up in syslog, thanks
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# to dovecot) and return an exit status that indicates temporary failure,
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# which is passed on to the authenticating client.
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traceback.print_exc()
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print(json.dumps(dict(os.environ), indent=2), file=sys.stderr)
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sys.exit(111)
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if resp.get('status') != 'authorized':
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# Indicates login failure.
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# (sys.exit should not be inside the try block.)
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sys.exit(1)
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# Signal ok by executing the indicated process, per the Dovecot
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# protocol. (Note that the second parameter is the 0th argument
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# to the called process, which is required and is typically the
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# file itself.)
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os.execl(sys.argv[1], sys.argv[1])
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