StripPathSuffix is documented to behave like StripPathPrefix: the suffix
is matched in normalized (unescaped) space except where the pattern uses
an escape sequence. But suffix stripping was implemented as
reverse(trimPathPrefix(reverse(escapedPath), reverse(suffix)))
Reversing the strings moves the '%' to the *end* of each "%xx" escape,
which defeats trimPathPrefix's escape detection (it expects '%' to
precede the two hex digits). As a result the escape-aware, normalized
comparison never happened for suffixes: a decoded pattern failed to
match a percent-encoded path.
Concretely, StripPathPrefix "/a/b/c" strips "/a%2Fb/c/d" to "/d", but the
mirror StripPathSuffix "/b/c" left "/a/b%2Fc" untouched instead of
producing "/a"; likewise StripPathSuffix "bc" did not strip "/a%62c".
This has been the behavior since #4948, which introduced both the
escape-aware trimPathPrefix and the reverse-based suffix trimming.
Replace the reverse trick with a dedicated trimPathSuffix that iterates
from the ends of both strings and applies the same escape-aware,
case-insensitive comparison as trimPathPrefix. An escape in the pattern
itself is still compared literally, so "%2fsuffix" continues to require
the path to contain that exact escape.
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
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