Merge branch '7or8bit-decode'

.gitignore

@@ -1,4 +1,9 @@
 venv/
+__pycache__/
 .idea/
-testing.py
+# misc testing scripts
+testing*.py
+# i have a symlink here so testing scripts can import gpgmymail
+# as python expects `import gpgmymail` to be importing `gpgmymail.py`
+gpgmymail.py
 

gpgmymail

@@ -34,6 +34,8 @@ import email.mime.application
 import email.mime.multipart
 import email.mime.message
 import typing
+# for decode_email:
+import quopri
 
 # see: https://gnupg.readthedocs.io/en/latest/
 import gnupg
@@ -49,6 +51,86 @@ def is_message_encrypted(message: email.message.Message) -> bool:
 
     return message.get_content_subtype() == "encrypted"
 
+def decode_email(message: email.message.Message) -> email.message.Message:
+    """Turn a quoted-printable or base64 encoded email into a 7or8bit encoded
+    email
+
+    :param message: email.message.Message to be decoded
+    :return: decoded email.message.Message"""
+    # this is a kinda hacky way to do this by manipulating the message as a
+    # string but i couldn't get it to work any other way
+    # decoding needed:
+    # as_string() gives us str, encode() gives us bytes
+    decoded_bytes = message.as_bytes()
+    decoded_bytes = quopri.decodestring(decoded_bytes)
+
+    # replace any instances of the Content-Transfer-Encoding header
+    # quopri version, we do base64 version down there
+    decoded_bytes = decoded_bytes.replace(
+        b'Content-Transfer-Encoding: quoted-printable',
+        b'Content-Transfer-Encoding: 7bit'
+    )
+
+    # REALLY hacky but i had issues with the more sensible ways to do this.
+    # iterates through a Message object to find CTEs of base64
+    # gets the b64 payload and the decoded payload
+    # then find and replaces in decoded_bytes the b64 payload
+    # with the decoded payload
+    # lol
+
+    def decode_b64_part(
+        part: email.message.Message,
+        decoded_bytes: bytes,
+        most_recent_boundary: str = None
+    ) -> bytes:
+        if part.get("Content-Transfer-Encoding") == "base64":
+            b64_str = part.get_payload()
+            # remove the boundary as we don't want to change this
+            if most_recent_boundary:
+                b64_str = b64_str.replace(most_recent_boundary, "")
+            # sometimes we have leftover hyphens from a boundary, so strip:
+            # hyphens not in base64 so we know not to use them
+            # strip whitespace first
+            b64_str = b64_str.strip()
+            b64_str = b64_str.strip('-')
+            b64_str = b64_str.encode()  # turn into bytes-like object
+            # this will also decode the boundary so there'll be some nonsese
+            # chars at end of email but it's nbd
+            decoded_b64_str = part.get_payload(decode=True)
+            return decoded_bytes.replace(
+                b64_str,
+                decoded_b64_str
+            )
+
+    quopri_decoded_message = email.message_from_bytes(decoded_bytes)
+    if quopri_decoded_message.is_multipart():
+        most_recent_boundary = None
+        for part in quopri_decoded_message.walk():
+            # multipart and has boundary (not None)
+            if part.is_multipart() and part.get_boundary():
+                most_recent_boundary = part.get_boundary()
+            else:
+                decoded_bytes = decode_b64_part(
+                    part,
+                    decoded_bytes,
+                    most_recent_boundary
+                )
+    else:
+        decoded_bytes = decode_b64_part(
+            quopri_decoded_message,
+            decoded_bytes,
+            None
+        )
+
+    decoded_bytes = decoded_bytes.replace(
+        b'Content-Transfer-Encoding: base64',
+        b'Content-Transfer-Encoding: 7bit'
+    )
+    
+    # if i do message_from_bytes it bizarrely changes it back to base64?
+    # utf-8 has encoding issues so do latin1
+    return email.message_from_string(decoded_bytes.decode("latin1"))
+
 def encrypt(
         message: email.message.Message,
         recipients: typing.List[str],
@@ -67,10 +149,14 @@ def encrypt(
 
     :return: The encrypted email as a string"""
     
+    # exclusion criteria:
     # some mail clients like Thunderbird don't like twice-encrypted emails,
     # so we return the message as-is if it's already encrypted
     if is_message_encrypted(message) and not unconditionally_encrypt:
         return message.as_string()
+
+    # make necessary changes to message
+    message = decode_email(message)
     
     gpg = gnupg.GPG()
     gpg.encoding = encoding