Hacker discovers iPhone SMS spoofing issue, asks Apple to fix for iOS 6
According to a blog posting by "pod2g" the way iOS handles SMS messages supports transmission of optional, advanced features in the SMS specification's User Data Header, including a "reply to" address.
Not all phones support these features, and "most carriers don't check this part of the message, which means one can write whatever he wants in this section," the hacker writes. This would apparently limit the audience of SMS spoofing largely to iPhone users.
Because the iPhone only displays the "reply to" address of incoming SMS messages, there's no way for users to verify the identity of the depicted sender, or to determine if it has been sent from someone other than the displayed phone number (unless the message is delivered via Apple's iMessage, which is both encrypted and unaffected by the SMS flaw because it is not an SMS).
In describing the SMS issue, Pod2g says "I consider [the flaw] to be severe, while it does not involve code execution."
A malicious user could send "spoofed" SMS messages that appear to come from another source (which is routinely done with email spam, as the standard email specification does not authenticate parties in header data either), falsely appearing to come from a friend or trusted source (such as a bank) for example.
The hacker asks Apple to address this issue before releasing iOS 6, noting that this behavior is still present in the latest, fourth developer beta of iOS 6.
15 Comments
Another hacker getting fame exploiting the media's love of Apple for getting page hits. If his interest was just in seeing it fixed he would have quietly told Apple.
I would not say this is severe at all. So what if they send a text saying "I'm your bank, send me your pin" because the reply isn't going to them. You always know who your replying to… Seems like an issue the carriers need to verify if they really don't want someone to specify another reply-to address, iOS seems to be behaving according to the standard.
SMS spoofing is an issue that predates iPhone, and there's really nothing Apple can do about it since it is caused by exactly the same constraints that allow E-mail spoofing: trusting all relays between the sender and the receiver. Without cryptographic public-key signatures, which are unfeasible in the case of SMSes due to their short maximum size, there is no way for the receiver to authenticate the sender.
[quote name="dev200" url="/t/151979/hacker-discovers-iphone-sms-spoofing-issue-asks-apple-to-fix-for-ios-6#post_2170266"]I would not say this is severe at all. So what if they send a text saying "I'm your bank, send me your pin" because the reply isn't going to them. You always know who your replying to… Seems like an issue the carriers need to verify if they really don't want someone to specify another reply-to address, iOS seems to be behaving according to the standard. [/quote] Of course. But reality doesn't get as many headlines as "Major new security flaw affects only iPhones".
2 jailbreak apps already let you spoof text messages. SpoofTexting and SpoofCard both in Cydia.