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Belts and braces: normalise paths before globbing

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This commit is contained in:
Miguel Jacq 2026-06-22 15:06:46 +10:00
parent c4448226c0
commit e10a3f62b0
Signed by: mig5
GPG key ID: 03906B4110AAD3B8
2 changed files with 97 additions and 10 deletions
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55
enroll/ignore.py
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@ -97,6 +97,34 @@ BLOCK_START = b"/*"
BLOCK_END = b"*/"
def normalize_for_match(path: str) -> str:
"""Lexically normalize a path string for deny/allow glob matching.
This collapses redundant separators ("//"), resolves "." and ".."
segments, and strips trailing slashes using ``os.path.normpath`` -- a
pure string operation that never touches the filesystem.
It is deliberately NOT ``os.path.realpath``/``Path.resolve``: resolving
symlinks would stat the filesystem and reintroduce a time-of-check /
time-of-use window before the later ``O_NOFOLLOW`` open in
``inspect_file``. The goal here is only to stop a non-canonical *string*
(e.g. "/etc//shadow" or "/etc/foo/../shadow") from slipping past a deny
glob like "/etc/shadow". It is defense-in-depth on top of the no-follow
open, not a load-bearing control by itself.
``normpath`` preserves a leading "//" because POSIX treats it as
implementation-defined; for glob matching we collapse it to a single
leading slash so patterns anchored at "/" still match.
"""
if not path:
return path
normalized = os.path.normpath(path)
if normalized.startswith("//") and not normalized.startswith("///"):
normalized = normalized[1:]
return normalized
@dataclass(frozen=True)
class FileInspection:
"""Bytes and metadata captured from one safely-opened source file."""
@ -145,26 +173,31 @@ class IgnorePolicy:
yield raw
def _path_deny_reason(self, path: str) -> Optional[str]:
# Match against a lexically-normalized path so non-canonical spellings
# (e.g. "/etc//shadow", "/etc/foo/../shadow") cannot slip past a deny
# glob. The original path is still what gets opened/recorded.
match_path = normalize_for_match(path)
# Always ignore plain *.log files (rarely useful as config, often noisy).
if path.endswith(".log"):
if match_path.endswith(".log"):
return "log_file"
# Ignore editor/backup files that end with a trailing tilde.
if path.endswith("~"):
if match_path.endswith("~"):
return "backup_file"
# Ignore backup shadow files
if path.startswith("/etc/") and path.endswith("-"):
if match_path.startswith("/etc/") and match_path.endswith("-"):
return "backup_file"
if not self.dangerous:
for g in self.deny_globs or []:
if fnmatch.fnmatch(path, g):
if fnmatch.fnmatch(match_path, g):
return "denied_path"
return None
def _content_deny_reason(self, path: str, data: bytes) -> Optional[str]:
if b"\x00" in data:
match_path = normalize_for_match(path)
for g in self.allow_binary_globs or []:
if fnmatch.fnmatch(path, g):
if fnmatch.fnmatch(match_path, g):
# Binary is acceptable for explicitly-allowed paths.
return None
return "binary_like"
@ -251,8 +284,9 @@ class IgnorePolicy:
No size checks or content scanning are performed for directories.
"""
if not self.dangerous:
match_path = normalize_for_match(path)
for g in self.deny_globs or []:
if fnmatch.fnmatch(path, g):
if fnmatch.fnmatch(match_path, g):
return "denied_path"
try:
@ -283,16 +317,17 @@ class IgnorePolicy:
"""
# Keep the same fast-path filename ignores as deny_reason().
if path.endswith(".log"):
match_path = normalize_for_match(path)
if match_path.endswith(".log"):
return "log_file"
if path.endswith("~"):
if match_path.endswith("~"):
return "backup_file"
if path.startswith("/etc/") and path.endswith("-"):
if match_path.startswith("/etc/") and match_path.endswith("-"):
return "backup_file"
if not self.dangerous:
for g in self.deny_globs or []:
if fnmatch.fnmatch(path, g):
if fnmatch.fnmatch(match_path, g):
return "denied_path"
try: