fonttools: Uncaught exception when loading font

The following program raises an uncaught exception:

import io
import sys
import atheris

from fontTools import ttLib
from fontTools.ttLib import TTFont
import xml         

def TestOneInput(data):
  randfile = "/tmp/random2.ttx"
  with open(randfile, "wb") as f:
    f.write(data)
  try:
    otf = TTFont(randfile)
  except ttLib.TTLibError:
    pass
  except AssertionError:
    pass
  except ImportError:
    pass
  
data = (b"\x4f\x54\x54\x4f\x00\x4b\x46\x32\x74\x63\x70\x46")                    
TestOneInput(data)

Where the atheris module refers to https://pypi.org/project/atheris/

The program is a derivative of the fuzzer here https://github.com/google/oss-fuzz/blob/master/projects/fonttools/fuzz_ttfont.py

The following program is a shortened version of above, without fuzzing-related logic:

from fontTools import ttLib
from fontTools.ttLib import TTFont

randfile = "/tmp/random2.ttx"
with open(randfile, "wb") as f:
  f.write(b"\x4f\x54\x54\x4f\x00\x4b\x46\x32\x74\x63\x70\x46")
try:
  otf = TTFont(randfile)
except ttLib.TTLibError:
  pass
except AssertionError:
  pass
except ImportError:
  pass

This produces the stack trace:

# python3 ./reproducer.py 
Traceback (most recent call last):
  File "./reproducer.py", line 24, in <module>
    otf = TTFont(randfile)
  File "/usr/local/lib/python3.8/site-packages/fontTools/ttLib/ttFont.py", line 164, in __init__
    self.reader = SFNTReader(file, checkChecksums, fontNumber=fontNumber)
  File "/usr/local/lib/python3.8/site-packages/fontTools/ttLib/sfnt.py", line 89, in __init__
    entry.fromFile(self.file)
  File "/usr/local/lib/python3.8/site-packages/fontTools/ttLib/sfnt.py", line 490, in fromFile
    sstruct.unpack(self.format, file.read(self.formatSize), self)
  File "/usr/local/lib/python3.8/site-packages/fontTools/misc/sstruct.py", line 88, in unpack
    elements = struct.unpack(formatstring, data)
struct.error: unpack requires a buffer of 16 bytes

This was found by way of OSS-Fuzz and the set up here: https://github.com/google/oss-fuzz/tree/master/projects/fonttools If you find this issue helpful then it would be great to have maintainer emails in the project.yaml to receive notifications of bug reports, which contain all details similar to what I posted above – namely they contain the stacktrace, crashing input and identification of the fuzzer.