check_resource_allowed treats /api/../admin as under /api

What happened

check_resource_allowed pads trailing slashes and then does requested_path.startswith(configured_path). It does not collapse . / ...

On main @ 08a3bc8 these return True:

• requested https://example.com/api/../admin vs configured https://example.com/api
• requested https://example.com/mcp/.. vs configured https://example.com/mcp
• requested https://example.com/api/%2e%2e/admin vs configured https://example.com/api

tests/shared/test_auth_utils.py already rejects /api123 vs /api (path-boundary). Dot-segments are not covered.

What I expected

A requested path that walks out of the configured prefix should not match. /api/foo/../v1 vs /api can still match after normalisation, because it stays under /api.

How to reproduce

from mcp.shared.auth_utils import check_resource_allowed

check_resource_allowed("https://example.com/api/../admin", "https://example.com/api")
# True today. I expected False.

I can send a PR that percent-decodes once, runs posixpath.normpath, then keeps the existing trailing-slash prefix rule. Happy to do that if you want it.

Written with AI assistance. I read auth_utils.py next to the path-boundary tests and reproduced it locally.

从 auth_utils.py 中的 check_resource_allowed 开始，检查 tests/shared/test_auth_utils.py 中现有的路径边界用例。为点段、百分号编码的点段以及仍位于已配置前缀下的路径添加覆盖，然后运行相关的 auth utility 测试。完成标准是：超出已配置前缀的路径不匹配，而仍位于其下的规范化路径仍然匹配。