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Vulnerability Advisory ====================== Remote SMS/MMS Denial of Service - "Curse Of Silence" for Nokia S60 phones URL === https://berlin.ccc.de/~tobias/cos/s60-curse-of-silence-advisory.txt Video ===== https://berlin.ccc.de/~tobias/cos/s60-curse-of-silence-demo.avi Affected Products ================= All Nokia Series60 2.6, 2.8, 3.0, 3.1 devices, see detailed list at the end of the document. Requirements to Execute Attack ============================== - MSISDN of the target - mobile phone contract that allows sending of SMS messages - (almost) any Nokia phone (or some other means of sending SMS messages with TP-PID set to "Internet Electronic Mail") Risk Level ========== Medium (for S60 2.8 and 3.1 devices): Target will not be able to receive any SMS or MMS messages while the attack is ongoing. After that, only very limited message receiving is possible until the device is Factory Resetted High (for S60 2.6 and 3.0 devices): Target will not be able to receive any SMS or MMS messages until the device is Factory Resetted Summary ======= Emails can be sent via SMS by setting the messages Protocol Identifier to "Internet Electronic Mail" and formatting the message like this: <email-address><space><message body> If such messages contain an <email-address> with more than 32 characters, S60 2.6, 2.8, 3.0 and 3.1 devices are not able to receive other SMS or MMS messages anymore. 2.6 and 3.0 devices lock up after only one message, 2.8 and 3.1 devices after 11 messages. Details ======= 3GPP TS 23.040 specifies a method for sending emails via SMS in section 3.8 ("SMS and Internet Electronic Mail interworking"). In its most basic form, such a SMS message starts with the from- (MT-SMS) or to-email-address (MO-SMS), followed by a space character, and then the message body. The TP-Procotol-Identifier of the SMS message has to be set to "Internet Electronic Mail" (value: 50 / 0x32). It is not specified how such a message should be displayed when received by the phone. Before S60 2.6, Series60 devices displayed such messages exactly as they were sent. Starting with S60 2.6, when the part of the message that should contain the from-address looks anything like an email address (i.e. it contains an "@" somewhere), this address is then displayed as the message sender instead of the usually shown TP-Originating-Address. If this email address is longer than 32 characters, Series60 2.6, 2.8, 3.0 and 3.1 devices fail to display the message or give any indication on the user interface that such a message has been received. They do, however, signal to the SMSC that they received the message by sending an RP-ACK. Devices running S60 2.6 or 3.0 will not be able to receive any other SMS message after that. The user interface does not give any indication of this situation. The only action to remedy this situation seems to be a Factory Reset of the device (by entering "*#7370#"). Devices running S60 2.8 or 3.1 react a little different: They do not lock up until they received at least 11 SMS-email messages with an email address that is longer than 32 characters. The device will not be able to receive any other SMS message after that - upon receiving the next message, the phone will just display a warning that there is not enough memory to receive further messages and that data should be deleted first. This message is even displayed on an otherwise completely "empty" device. After switching the phone off and on again, it has limited capability for receiving SMS messages again: If it receives a SMS message that is split up into several parts (3GPP TS 23.040, 220.127.116.11.1 Concatenated Short Messages) it is only able to receive the first part and will display the "not enough memory" warning again. After powercycling the device again, it can then receive the second part. If there is a third part, it has to be powercycled again, and so on. Also, an attacker now just needs to send one more "Curse Of Silence" message to lock the phone up again. By always sending yet another one as soon as the status report for delivery of the previous message is received, the attacker could completely prevent a target from receiving any other SMS/MMS messages. Only Factory Resetting the device will restore its full message receiving capabilities. Note that, if a backup is made using Nokia PC-Suite *after* being attacked, the blocking messages are also backuped and will be sent to the device again when restoring the backup after the Factory Reset. Note that not being able to receive SMS messages also means not being able to receive MMS messages, since they are signalled by sending an SMS message to the device. "Curse Of Silence" messages can be generated with any phone or cellular modem that supports 3GPP TS 27.005 AT commands and with most Nokia phones also directly from the user interface. For example, on S60 devices, when in the message editor, the type of the message can be switched to "E-mail" under "Options" -> "Sending options" -> "Message sent as". The 6310i conveniently offers a "Write email" menu entry in the messaging menu. The simplest form of content for a Curse Of Silence would be something like "email@example.com " (the digits are used only to illustrate the length of the "email address" of more than 32 characters). Note the space at the end of the message! Workaround ========== None known for the user side. Until a firmware fix is available, network operators should filter messages with TP-PID "Internet Electronic Mail" and an email address of more than 32 characters or reset the TP-PID of these messages to 0. Credits ======= Tobias Engel <firstname.lastname@example.org> November 9, 2008 Many thanks to Frank Rieger for spending countless hours cutting and editing the video. Detailed List of Affected Products ================================== Tested on several S60 2.6, 3.0 and 3.1 devices. Since the vulnerable component is a S60 base functionality, it seems safe to assume that all devices with these OS versions are affected. S60 3rd Edition, Feature Pack 1 (S60 3.1): Nokia E90 Communicator Nokia E71 Nokia E66 Nokia E51 Nokia N95 8GB Nokia N95 Nokia N82 Nokia N81 8GB Nokia N81 Nokia N76 Nokia 6290 Nokia 6124 classic Nokia 6121 classic Nokia 6120 classic Nokia 6110 Navigator Nokia 5700 XpressMusic S60 3rd Edition, initial release (S60 3.0): Nokia E70 Nokia E65 Nokia E62 Nokia E61i Nokia E61 Nokia E60 Nokia E50 Nokia N93i Nokia N93 Nokia N92 Nokia N91 8GB Nokia N91 Nokia N80 Nokia N77 Nokia N73 Nokia N71 Nokia 5500 Nokia 3250 S60 2nd Edition, Feature Pack 3 (S60 2.8): Nokia N90 Nokia N72 Nokia N70 S60 2nd Edition, Feature Pack 2 (S60 2.6): Nokia 6682 Nokia 6681 Nokia 6680 Nokia 6630 Change History ============== December 30, 2008: Removed auth details since they are no longer required December 21, 2008: Corrected version numbers for S60 2nd Edition December 13, 2008: S60 2.8 devices react like S60 3.1 devices, not like S60 2.6 or 3.0 devices