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declare proc_dir earlier and resolve exact proc_dir #1001

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declare proc_dir earlier and resolve exact proc_dir #1001

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11 changes: 8 additions & 3 deletions dmoj/cptbox/isolate.py
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Original file line number Diff line number Diff line change
Expand Up @@ -344,13 +344,19 @@ def _access_check(self, debugger: Debugger, file: str, fs_jail: FilesystemPolicy

# normpath doesn't strip leading slashes
projected = normalized = '/' + os.path.normpath(file).lstrip('/')
proc_dir = f'/proc/{debugger.tid}'
if normalized.startswith('/proc/self'):
# modify file so that the correct realpath is used
file = os.path.join(f'/proc/{debugger.tid}', os.path.relpath(file, '/proc/self'))
projected = '/' + os.path.normpath(file).lstrip('/')
elif normalized.startswith(f'/proc/{debugger.tid}/'):
elif normalized.startswith(
proc_dir + '/'
): # Use a slash because otherwise if we are 123 then /proc/12345 matches
# If the child process uses /proc/getpid()/foo, set the normalized path to be /proc/self/foo.
# Access rules can more easily check /proc/self.
normalized = os.path.join('/proc/self', os.path.relpath(file, f'/proc/{debugger.tid}'))
normalized = os.path.join('/proc/self', os.path.relpath(file, proc_dir))
elif normalized == proc_dir:
normalized = '/proc/self'
real = os.path.realpath(file)

try:
Expand All @@ -367,7 +373,6 @@ def _access_check(self, debugger: Debugger, file: str, fs_jail: FilesystemPolicy
raise DeniedSyscall(ACCESS_EACCES, f'Denying {file}, normalized to {normalized}')

if normalized != real:
proc_dir = f'/proc/{debugger.tid}'
if real.startswith(proc_dir):
real = os.path.join('/proc/self', os.path.relpath(real, proc_dir))

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