Server working

client/api.py

@@ -0,0 +1,52 @@
+import requests
+
+class APIError(Exception):
+    "A custom error we'll use when something goes wrong with the API"
+
+class SubRosaAPI:
+    """An API for the SubRosa server.
+    """
+
+    def __init__(self, url):
+        self.url = url
+
+    def get_user(self, username):
+        route = "/users"
+        params = {'name': username}
+        return self.get(route, params)
+
+    def create_user(self, username, public_key):
+        route = "/users/new"
+        params = {'name': username, 'public_key': public_key}
+        return self.post(route, params)
+
+    def get_messages(self, username):
+        route = "/messages"
+        params = {'name': username}
+        return self.get(route, params)
+
+    def send_message(self, sender, recipient, ciphertext, time_sent, time_sent_signature):
+        route = "/messages/send"
+        params = {
+            'sender': sender, 
+            'recipient': recipient,
+            'ciphertext': ciphertext,
+            'time_sent': time_sent,
+            'time_sent_signature': time_sent_signature,
+        }
+        return self.get(route, params)
+
+    def get(self, route, params):
+        response = requests.get(self.url + route, json=params)
+        if response.ok:
+            return response.json()
+        else:
+            raise APIError(response.json()['error'])
+
+    def post(self, route, params):
+        response = requests.post(self.url + route, json=params)
+        if response.ok:
+            return response.json()
+        else:
+            raise APIError(response.json()['error'])
+

client/user_interface.py

@@ -0,0 +1,106 @@
+from pathlib import Path
+from api import SubRosaAPI, APIError
+from datetime import datetime
+import sys
+sys.path.insert(0, ".")
+from encryption import PrivateKey, PublicKey
+
+class SubRosaUI:
+    """A user interface to the SubRosa chat system.
+    """
+    def __init__(self, private_key_file, url):
+        self.api = SubRosaAPI(url)
+        if Path(private_key_file).exists():
+            self.private_key = PrivateKey.load(private_key_file)
+        else:
+            self.private_key = PrivateKey.generate()
+            self.private_key.save(private_key_file)
+        self.public_key = self.private_key.get_public_key()
+
+    def run(self, username):
+        self.username = username
+        self.user = self.get_or_create_user(username)
+        print("Welcome to SubRosa.")
+        while True:
+            choice = self.choose_action_from_menu()
+            if choice == 'VIEW':
+                self.show_messages()
+            elif choice == 'SEND':
+                self.send_message()
+            print("=" * 80)
+
+    def get_or_create_user(self, username):
+        """Gets user info from the server, or creates the user. 
+        If the user already exists, checks that our public key matches
+        the server's public key for the user. 
+        """
+        try:
+            user = self.api.get_user(username)
+            if user['public_key'] != str(self.public_key):
+                raise ValueError(f"Invalid key for {username}")
+        except APIError:
+            user = self.api.create_user(username, str(self.public_key))
+        return user
+
+    def choose_action_from_menu(self):
+        """Gets a choice from the user. 
+        """
+        print("What would you like to do?")
+        print("1. See messages")
+        print("2. Send a message")
+        while True:
+            choice = input("> ").strip()
+            if choice == '1':
+                return 'VIEW'
+            elif choice == '2': 
+                return 'SEND'
+
+    def show_messages(self):
+        messages = self.api.get_messages(self.username)['messages']
+        if messages:
+            for i, message in enumerate(messages):
+                cleartext = self.private_key.decrypt(message['ciphertext'])
+                print('-' * 80)
+                print(f"{i}. From {message['sender']}:")
+                print(cleartext)
+        else:
+            print(f"No messages for {self.username}.")
+
+    def send_message(self):
+        try:
+            recipient_name = input("Username of recipient: ").strip()
+            recipient = self.api.get_user(recipient_name)
+        except APIError:
+            print(f"No user named {recipient_name}.")
+            return
+        recipient_public_key = PublicKey.load(recipient['public_key'])
+        plaintext = input("Message: ")
+        ciphertext = recipient_public_key.encrypt(plaintext)
+        time_sent = self.get_current_time()
+        time_sent_signature = self.private_key.sign(time_sent)
+        self.api.send_message(
+            self.username, 
+            recipient_name, 
+            ciphertext, 
+            time_sent, 
+            time_sent_signature,
+        )
+        print('-' * 80)
+        print(f"Message sent to {recipient_name}")
+
+
+    def get_current_time(self):
+        return datetime.utcnow().isoformat()
+
+def main():
+    from argparse import ArgumentParser
+    parser = ArgumentParser()
+    parser.add_argument("username")
+    parser.add_argument("-k", "--key", default="subrosa_private_key.pem")
+    parser.add_argument("-s", "--server-url", default="http://127.0.0.1:5000")
+    args = parser.parse_args()
+    ui = SubRosaUI(args.key, args.server_url)
+    ui.run(args.username)
+
+if __name__ == '__main__':
+    main()

encryption.py

@@ -19,11 +19,13 @@ class PrivateKey:
     @classmethod
     def load(cls, pem):
         """Loads an existing private key.
-        When `pem` is of type bytes, assumes it is a pem serialization.
+        Pem may be a bytes or a string representation of the PEM-formatted key, 
-        Otherwise, assumes `pem` is a path to a pem file.
+        or a path to a pem file. 
         """
         if isinstance(pem, bytes):
-            key = serialization.load_pem_private_key(pem)
+            key = serialization.load_pem_private_key(pem, password=None)
+        elif isinstance(pem, str) and pem.startswith("-----BEGIN RSA PRIVATE KEY-----"):
+            key = serialization.load_pem_private_key(pem.encode('ascii'), password=None)
         elif isinstance(pem, (str, Path)):
             with open(pem, 'rb') as key_file:
                 key = serialization.load_pem_private_key(
@@ -58,7 +60,7 @@ class PrivateKey:
             encoding=serialization.Encoding.PEM,
             format=serialization.PrivateFormat.TraditionalOpenSSL,
             encryption_algorithm=serialization.NoEncryption()
-        ).decode('utf8')
+        ).decode('utf8').strip()
 
     def __repr__(self):
         return "<PrivateKey>"
@@ -106,11 +108,13 @@ class PublicKey:
     @classmethod
     def load(self, pem):
         """Loads an existing public key.
-        When `pem` is of type bytes, assumes it is a pem serialization.
+        Pem may be a bytes or a string representation of the PEM-formatted key, 
-        Otherwise, assumes `pem` is a path to a pem file.
+        or a path to a pem file. 
         """
         if isinstance(pem, bytes):
             key = serialization.load_pem_public_key(pem)
+        elif isinstance(pem, str) and pem.startswith("-----BEGIN PUBLIC KEY-----"):
+            key = serialization.load_pem_public_key(pem.encode('ascii'))
         elif isinstance(pem, (str, Path)):
             with open(pem, 'rb') as key_file:
                 key = serialization.load_pem_public_key(key_file.read())
@@ -126,7 +130,7 @@ class PublicKey:
         return self.key.public_bytes(
             encoding=serialization.Encoding.PEM,
             format=serialization.PublicFormat.SubjectPublicKeyInfo
-        ).decode('utf8')
+        ).decode('utf8').strip()
 
     def __repr__(self):
         return "<PublicKey>"

poetry.lock

@@ -17,6 +17,17 @@ typing-extensions = {version = ">=4", markers = "python_version < \"3.11\""}
 [package.extras]
 tests = ["mypy (>=0.800)", "pytest", "pytest-asyncio"]
 
+[[package]]
+name = "certifi"
+version = "2024.2.2"
+description = "Python package for providing Mozilla's CA Bundle."
+optional = false
+python-versions = ">=3.6"
+files = [
+    {file = "certifi-2024.2.2-py3-none-any.whl", hash = "sha256:dc383c07b76109f368f6106eee2b593b04a011ea4d55f652c6ca24a754d1cdd1"},
+    {file = "certifi-2024.2.2.tar.gz", hash = "sha256:0569859f95fc761b18b45ef421b1290a0f65f147e92a1e5eb3e635f9a5e4e66f"},
+]
+
 [[package]]
 name = "cffi"
 version = "1.16.0"
@@ -81,6 +92,105 @@ files = [
 [package.dependencies]
 pycparser = "*"
 
+[[package]]
+name = "charset-normalizer"
+version = "3.3.2"
+description = "The Real First Universal Charset Detector. Open, modern and actively maintained alternative to Chardet."
+optional = false
+python-versions = ">=3.7.0"
+files = [
+    {file = "charset-normalizer-3.3.2.tar.gz", hash = "sha256:f30c3cb33b24454a82faecaf01b19c18562b1e89558fb6c56de4d9118a032fd5"},
+    {file = "charset_normalizer-3.3.2-cp310-cp310-macosx_10_9_universal2.whl", hash = "sha256:25baf083bf6f6b341f4121c2f3c548875ee6f5339300e08be3f2b2ba1721cdd3"},
+    {file = "charset_normalizer-3.3.2-cp310-cp310-macosx_10_9_x86_64.whl", hash = "sha256:06435b539f889b1f6f4ac1758871aae42dc3a8c0e24ac9e60c2384973ad73027"},
+    {file = "charset_normalizer-3.3.2-cp310-cp310-macosx_11_0_arm64.whl", hash = "sha256:9063e24fdb1e498ab71cb7419e24622516c4a04476b17a2dab57e8baa30d6e03"},
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+    {file = "charset_normalizer-3.3.2-cp39-cp39-musllinux_1_1_x86_64.whl", hash = "sha256:ff8fa367d09b717b2a17a052544193ad76cd49979c805768879cb63d9ca50561"},
+    {file = "charset_normalizer-3.3.2-cp39-cp39-win32.whl", hash = "sha256:aed38f6e4fb3f5d6bf81bfa990a07806be9d83cf7bacef998ab1a9bd660a581f"},
+    {file = "charset_normalizer-3.3.2-cp39-cp39-win_amd64.whl", hash = "sha256:b01b88d45a6fcb69667cd6d2f7a9aeb4bf53760d7fc536bf679ec94fe9f3ff3d"},
+    {file = "charset_normalizer-3.3.2-py3-none-any.whl", hash = "sha256:3e4d1f6587322d2788836a99c69062fbb091331ec940e02d12d179c1d53e25fc"},
+]
+
 [[package]]
 name = "cryptography"
 version = "42.0.7"
@@ -195,6 +305,17 @@ files = [
     {file = "environ-1.0.tar.gz", hash = "sha256:4df7f1dfeb7d1c988d2e19a8bd5d547a526e0400aeb35adf732032472f35dcb0"},
 ]
 
+[[package]]
+name = "idna"
+version = "3.7"
+description = "Internationalized Domain Names in Applications (IDNA)"
+optional = false
+python-versions = ">=3.5"
+files = [
+    {file = "idna-3.7-py3-none-any.whl", hash = "sha256:82fee1fc78add43492d3a1898bfa6d8a904cc97d8427f683ed8e798d07761aa0"},
+    {file = "idna-3.7.tar.gz", hash = "sha256:028ff3aadf0609c1fd278d8ea3089299412a7a8b9bd005dd08b9f8285bcb5cfc"},
+]
+
 [[package]]
 name = "pycparser"
 version = "2.22"
@@ -206,6 +327,27 @@ files = [
     {file = "pycparser-2.22.tar.gz", hash = "sha256:491c8be9c040f5390f5bf44a5b07752bd07f56edf992381b05c701439eec10f6"},
 ]
 
+[[package]]
+name = "requests"
+version = "2.31.0"
+description = "Python HTTP for Humans."
+optional = false
+python-versions = ">=3.7"
+files = [
+    {file = "requests-2.31.0-py3-none-any.whl", hash = "sha256:58cd2187c01e70e6e26505bca751777aa9f2ee0b7f4300988b709f44e013003f"},
+    {file = "requests-2.31.0.tar.gz", hash = "sha256:942c5a758f98d790eaed1a29cb6eefc7ffb0d1cf7af05c3d2791656dbd6ad1e1"},
+]
+
+[package.dependencies]
+certifi = ">=2017.4.17"
+charset-normalizer = ">=2,<4"
+idna = ">=2.5,<4"
+urllib3 = ">=1.21.1,<3"
+
+[package.extras]
+socks = ["PySocks (>=1.5.6,!=1.5.7)"]
+use-chardet-on-py3 = ["chardet (>=3.0.2,<6)"]
+
 [[package]]
 name = "sqlparse"
 version = "0.5.0"
@@ -243,7 +385,24 @@ files = [
     {file = "tzdata-2024.1.tar.gz", hash = "sha256:2674120f8d891909751c38abcdfd386ac0a5a1127954fbc332af6b5ceae07efd"},
 ]
 
+[[package]]
+name = "urllib3"
+version = "2.2.1"
+description = "HTTP library with thread-safe connection pooling, file post, and more."
+optional = false
+python-versions = ">=3.8"
+files = [
+    {file = "urllib3-2.2.1-py3-none-any.whl", hash = "sha256:450b20ec296a467077128bff42b73080516e71b56ff59a60a02bef2232c4fa9d"},
+    {file = "urllib3-2.2.1.tar.gz", hash = "sha256:d0570876c61ab9e520d776c38acbbb5b05a776d3f9ff98a5c8fd5162a444cf19"},
+]
+
+[package.extras]
+brotli = ["brotli (>=1.0.9)", "brotlicffi (>=0.8.0)"]
+h2 = ["h2 (>=4,<5)"]
+socks = ["pysocks (>=1.5.6,!=1.5.7,<2.0)"]
+zstd = ["zstandard (>=0.18.0)"]
+
 [metadata]
 lock-version = "2.0"
 python-versions = "^3.10"
-content-hash = "c3f2c06832bafe7f40cadca2f6a067ca8f7cdaf5098d6e1e15da97e00634cede"
+content-hash = "cac991f3d0e9e354a9e492ba15735644e560ec8c9f7dfb8f9f05570b863a5a88"

pyproject.toml

@@ -10,6 +10,7 @@ packages = [{include = "lab_subrosa"}]
 python = "^3.10"
 django-banjo = "^0.5.1"
 cryptography = "^42.0.7"
+requests = "^2.31.0"
 
 
 [build-system]

server/app/models.py

@@ -7,7 +7,7 @@ from banjo.models import (
 
 class User(Model):
     name = StringField(unique=True)
-    public_key = StringField(unique=True)
+    public_key = StringField()
 
     def to_dict(self):
         return {
@@ -20,3 +20,10 @@ class Message(Model):
     recipient = ForeignKey(User, related_name="messages_received")
     ciphertext = StringField()
     read = BooleanField()
+
+    def to_dict(self):
+        return {
+            'sender': self.sender.name,
+            'recipient': self.recipient.name, 
+            'ciphertext': self.ciphertext,
+        }

server/app/views.py

@@ -2,7 +2,10 @@ from banjo.urls import route_get, route_post
 from app.models import User, Message
 from banjo.http import NotFound, NotAllowed
 from datetime import datetime
-import rsa
+from cryptography.exceptions import InvalidSignature
+import sys
+sys.path.insert(0, "..")
+from encryption import PrivateKey, PublicKey
 
 @route_post("users/new", args={'name': str, 'public_key': str})
 def create_user(params):
@@ -27,14 +30,14 @@ def get_user(params):
 def get_messages(params):
     "Return all the messages for a user"
     try:
-        user = User.objects.get(name=params['name'])
+        recipient = User.objects.get(name=params['name'])
     except User.DoesNotExist:
         raise NotFound(f"There is no user named {params['name']}")
-    messages = Message.objects.filter(user=user)
+    messages = Message.objects.filter(recipient=recipient)
     return {'messages': [m.to_dict() for m in messages]}
 
 @route_get("messages/send", args={'sender': str, 'recipient': str, 'ciphertext': str,
-        'time_sent': str, 'auth': str})
+        'time_sent': str, 'time_sent_signature': str})
 def send_message(params):
     """Securely sends an encrypted message from `sender` to `recipient`
     Sender and recipient should be recognized usernames. 
@@ -44,18 +47,28 @@ def send_message(params):
     """
     try:
         sender = User.objects.get(name=params['sender'])
-        recipient = User.objects.get(name=['recipient'])
+        recipient = User.objects.get(name=params['recipient'])
     except User.DoesNotExist:
-        raise NotFound(f"There is no user named {params['name']}")
+        raise NotFound(f"User not found.")
     try: 
         time_sent = datetime.fromisoformat(params['time_sent'])
     except ValueError:
         raise NotAllowed(f"Time sent ({params['time_sent']}) must be in isoformat")
-    if (datetime.now() - time_sent).seconds > 10:
+    now = datetime.utcnow()
+    if (now - time_sent).seconds > 10:
         raise NotAllowed(f"The message is too old. Time sent must be within ten seconds")
-    if not 
+    sender_public_key = PublicKey.load(sender.public_key)
-
+    try:
-
+        sender_public_key.verify_signature(params['time_sent'], params['time_sent_signature'])
+    except InvalidSignature:
+        raise NotAllowed("Invalid signature.")
+    message = Message(
+        sender=sender,
+        recipient=recipient,
+        ciphertext=params['ciphertext'],
+    )
+    message.save()
+    return message.to_dict()