- Aug 6, 2014
- 1,044
Researchers at Johns Hopkins University have cracked the encryption on Apple’s iMessage service, proving that a skilled attacker is capable of reading messages sent between iPads, iPhones and Macs despite the security measures protecting the devices.
The attack relies on a flaw in iMessage which will be fixed in iOS 9.3, released today. But until the software update is released, and the companion update for Mac OS, users’ messages are vulnerable to eavesdropping from a determined attacker.
The vulnerability comes as attention worldwide is focused on Apple’s encryption protocols. The FBI is in the process of suing the firm in an attempt to force it to help weaken the security on an older iPhone which was in the possession of the gunman in the San Bernardino shootings, and Apple has fought strongly against that mandate.
Although the iMessage encryption, which protects text messages in transit, is not the same as the iPhone encryption, which protects the data at rest in an individual iPhone, in other situations the strength of iMessage’s encryption has also worked against law enforcement. Even Apple itself cannot read (properly) encrypted iMessages, which led it to refuse a US court order in September last year.
The iMessage vulnerability will not help the FBI break in to the San Bernardino shooter’s iPhone, but does underscore remarks made by former US counter-terror chief Richard Clarke: that all software has vulnerabilities, and if the FBI simply wanted to break into the iPhone, rather than set legal precedent, then the agency would have other ways in.
“If I were in the job now, I would have simply told the FBI to call Fort Meade, the headquarters of the National Security Agency, and NSA would have solved this problem for him,” Clarke told NPR. “They’re not as interested in solving this problem as they are in getting a legal precedent.”
Although the latest iMessage flaw affects every Apple device, it still requires a determined attacker to exploit it. The specific bug, uncovered by a team of researchers led by Matthew D Green and first reported by the Washington Post, calls for an attacker to successfully perform a “man in the middle” attack, convincing the target’s iPhone to connect to a fake iMessage server rather than Apple’s real servers.
Typically, doing so would not help the attacker read the stolen message, as it is encrypted, but the bug discovered by Green’s team makes it easy to guess the key used to protect the message. Initially, Green himself warned Apple of the bug, which he discovered by reading the technical description of the encryption process. But after a few months had passed and there had been no fix forthcoming, he and his students decided to build a proof-of-concept attack to show that the bug was real.
Although the attack doesn’t reveal the encryption key directly, it allows the attacker to guess it by changing an individual letter or digit in the key and sending it back to the phone. If the guess is correct, the phone will confirm it as so, allowing them to rapidly build up knowledge of the real encryption key.
That flaw drastically reduces the number of guesses needed to guess the encryption key through brute force. Without it, guessing a password wouldn’t be possible before the sun exploded billions of years into the future; with it, it can be done in an afternoon.
David Kennerley, of threat research firm Webroot, pointed out that the new flaw shows how important it is to keep operating systems up to date. “Although not simple to crack, news of this zero day exploit arrives at a very interesting time. The continuing debate around backdoors in encryption is only a debate if the encryption we use to keep our data and communications safe is non-exploitable.
“Users should always keep their devices OSs up to date – I’m sure Apple are very thankful to Johns Hopkins University for finding this flaw – hopefully before the bad guys. It’s also a reminder that sometimes even the more vocal players don’t get it right first time.”
In a statement, Apple acknowledged the flaw, saying: “Apple works hard to make our software more secure with every release. We appreciate the team of researchers that identified this bug and brought it to our attention so we could patch the vulnerability.”
The attack relies on a flaw in iMessage which will be fixed in iOS 9.3, released today. But until the software update is released, and the companion update for Mac OS, users’ messages are vulnerable to eavesdropping from a determined attacker.
The vulnerability comes as attention worldwide is focused on Apple’s encryption protocols. The FBI is in the process of suing the firm in an attempt to force it to help weaken the security on an older iPhone which was in the possession of the gunman in the San Bernardino shootings, and Apple has fought strongly against that mandate.
Although the iMessage encryption, which protects text messages in transit, is not the same as the iPhone encryption, which protects the data at rest in an individual iPhone, in other situations the strength of iMessage’s encryption has also worked against law enforcement. Even Apple itself cannot read (properly) encrypted iMessages, which led it to refuse a US court order in September last year.
The iMessage vulnerability will not help the FBI break in to the San Bernardino shooter’s iPhone, but does underscore remarks made by former US counter-terror chief Richard Clarke: that all software has vulnerabilities, and if the FBI simply wanted to break into the iPhone, rather than set legal precedent, then the agency would have other ways in.
“If I were in the job now, I would have simply told the FBI to call Fort Meade, the headquarters of the National Security Agency, and NSA would have solved this problem for him,” Clarke told NPR. “They’re not as interested in solving this problem as they are in getting a legal precedent.”
Although the latest iMessage flaw affects every Apple device, it still requires a determined attacker to exploit it. The specific bug, uncovered by a team of researchers led by Matthew D Green and first reported by the Washington Post, calls for an attacker to successfully perform a “man in the middle” attack, convincing the target’s iPhone to connect to a fake iMessage server rather than Apple’s real servers.
Typically, doing so would not help the attacker read the stolen message, as it is encrypted, but the bug discovered by Green’s team makes it easy to guess the key used to protect the message. Initially, Green himself warned Apple of the bug, which he discovered by reading the technical description of the encryption process. But after a few months had passed and there had been no fix forthcoming, he and his students decided to build a proof-of-concept attack to show that the bug was real.
Although the attack doesn’t reveal the encryption key directly, it allows the attacker to guess it by changing an individual letter or digit in the key and sending it back to the phone. If the guess is correct, the phone will confirm it as so, allowing them to rapidly build up knowledge of the real encryption key.
That flaw drastically reduces the number of guesses needed to guess the encryption key through brute force. Without it, guessing a password wouldn’t be possible before the sun exploded billions of years into the future; with it, it can be done in an afternoon.
David Kennerley, of threat research firm Webroot, pointed out that the new flaw shows how important it is to keep operating systems up to date. “Although not simple to crack, news of this zero day exploit arrives at a very interesting time. The continuing debate around backdoors in encryption is only a debate if the encryption we use to keep our data and communications safe is non-exploitable.
“Users should always keep their devices OSs up to date – I’m sure Apple are very thankful to Johns Hopkins University for finding this flaw – hopefully before the bad guys. It’s also a reminder that sometimes even the more vocal players don’t get it right first time.”
In a statement, Apple acknowledged the flaw, saying: “Apple works hard to make our software more secure with every release. We appreciate the team of researchers that identified this bug and brought it to our attention so we could patch the vulnerability.”
