I'd want to design import mail functionality for an email provider. The process is: user enters email and password for another service at my site and then site accesses another email provider and downloads messages from it via IMAP or POP3 over TLS/STARTTLS.

What security issues should be taken into account when designing such functionality? Can those emails have something that will make import process stuck? Do i need anything else besides antivirus?

  • Can it be SMS confirmation? So when trying to enter password for remote server, you need to confirm the token of your new account. This way you make sure you dont do something stupid by quickly clicking and think twice and you can put big button "delete mail from remote server". Jul 24, 2012 at 21:21
  • 1
    @AndrewSmith No-one said that he plans to deliberately delete the messages from the other service, just get a copy of them.
    – ewanm89
    Jul 24, 2012 at 22:38

1 Answer 1

  1. You are accepting the users password for an account for a service not of your control and storing it for some time (may only be in RAM) this may also be forbidden for the user of the other service to give out their password in TOS or similar.
  2. The obvious issues with TLS MITM attacks, rogue CA... (see other questions on stack exchange, work by Moxie Marlinspike, probably not easily controllable unless you want to take your time to pin certs manually in your server implementation and only allow specific known services).
  3. The other service may do things like automatically delete emails as they are downloaded or similar that one might warn users to check they are okay with before proceeding.
  4. The usual security issues with your own services, buffer overflows, sql injection, cross site scripting, cross site request forgery...

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