Instagram makes API calls to non-HTTPS endpoints with session cookies in the request headers allowing full session hijack by a malicious actor.
Steps to reproduce (on Mac OS X):
- Jump on an open or WEP encrypted wifi access point
- Put your network interface into promiscuous mode filtering on i.instagram.com
sudo tcpdump -In -i en0 -s 2048 -A dst i.instagram.com
- Wait for someone to use the Instagram iOS app on the same network
- Extract cookie request header from the resulting output
- Use sessionid cookie parameter to make any api call as that user
Even https endpoints like direct messages.
curl -H 'User-Agent: Instagram 6.0.4 (iPhone6,2; iPhone OS 7_1_1; en_GB; en-GB) AppleWebKit/420+' \ -H 'Cookie: sessionid=REDACTED' \ https://i.instagram.com/api/v1/direct_share/inbox/`
This returns the user's direct message inbox as JSON
I was able to perform a session hijack on my own account on my laptop while someone else browsed instagram on my iPhone.
I was also able to:
- take the cookie sniffed from the iOS app
- go to instagram.com as an unlogged in user.
- set document.cookie = $COOKIE
- navigate to a profile
- see I'm logged in as that user
There is some screwy behaviour where 'instagram.com/' gets into redirect loop, I will see if I can fix that. However going to 'instagram.com/someones_profile' works and shows me as logged in.
I think this attack is extremely severe because it allows full session hijack and is easily automated. I could go to the Apple Store tomorrow and reap thousands of accounts in one day, and then use them to post spam.
Recommendations:
- Use SSL everywhere
- Revoke all logged-in sessions?
@wodim what would @stevegraham be sued for even if he didn't adhere to FB's responsible disclosure procedure? People might have frowned on releasing this information before disclosing it to Facebook, but AFAIK there is nothing here that Facebook could sue him for (and win the decision).