pdfdump crashes with UnicodeEncodeError

Brief description

When dumping packets with random bytes the following happens:

Traceback (most recent call last):
  File "/home/user/test2.py", line 10, in <module>
    packet.pdfdump("test.pdf")
  File "/home/user/.local/lib/python3.10/site-packages/scapy/base_classes.py", line 474, in pdfdump
    canvas = self.canvas_dump(**kargs)
  File "/home/user/.local/lib/python3.10/site-packages/scapy/packet.py", line 930, in canvas_dump
    vt = pyx.text.text(XSTART + 3.5, (YTXT - y) * YMUL, r"\font\cmssfont=cmss10\cmssfont{%s}" % tex_escape(fval))  # noqa: E501
  File "/home/user/.local/lib/python3.10/site-packages/pyx/text.py", line 1455, in wrapped
    return f(self, *args, **kwargs)
  File "/home/user/.local/lib/python3.10/site-packages/pyx/text.py", line 1491, in text
    return self.instance.text(*args, **kwargs)
  File "/home/user/.local/lib/python3.10/site-packages/pyx/text.py", line 1331, in text
    return self.text_pt(unit.topt(x), unit.topt(y), *args, **kwargs)
  File "/home/user/.local/lib/python3.10/site-packages/pyx/text.py", line 1305, in text_pt
    left_pt, right_pt, height_pt, depth_pt = self.do_typeset(expr, self.texmessages_run_default + self.texmessages_run + texmessages)
  File "/home/user/.local/lib/python3.10/site-packages/pyx/text.py", line 1225, in do_typeset
    return self._execute(expr, texmessages, STATE_TYPESET, STATE_TYPESET)
  File "/home/user/.local/lib/python3.10/site-packages/pyx/text.py", line 1085, in _execute
    expr.encode(self.texenc)
UnicodeEncodeError: 'ascii' codec can't encode character '\u0700' in position 32: ordinal not in range(128)

It seems that texenc in pyx is set to default ASCII. If I change it to 'utf-8' everything works fine.

Scapy version

2.5.0

Python version

3.10

Operating system

Kubuntu 22.04

Additional environment information

No response

How to reproduce

This will eventually fail

from scapy.layers.inet import Ether, UDP, IP
from scapy.compat import raw
import numpy as np
import time

while True:
  packet = Ether(dst="00:00:00:00:00:00", src="00:00:00:00:00:00", type=0x800)/IP(src="0.0.0.0", dst="0.0.0.0")/UDP(sport=0, dport=0)
  packet = packet/raw(np.random.bytes(512))
  packet.pdfdump("test.pdf")
  time.sleep(1)

Actual result

Exception

Expected result

A PDF

Related resources

No response

Start with scapy/base_classes.py at pdfdump and scapy/packet.py at canvas_dump, then reproduce the failure with the random-bytes script and inspect the PyX text encoding path shown in the traceback. Done means packet.pdfdump("test.pdf") produces a PDF without raising UnicodeEncodeError for random byte payloads.