fix: document request body plaintext disk spooling and mitigation steps#381
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eilandert wants to merge 1 commit into
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fix: document request body plaintext disk spooling and mitigation steps#381eilandert wants to merge 1 commit into
eilandert wants to merge 1 commit into
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request_body_in_persistent_file unconditionally spools all client request bodies to disk as plaintext temporary files. This bypasses client_body_buffer_size, meaning even small bodies end up on disk. In environments handling sensitive POST data (authentication, payment, health records), this creates plaintext files readable by any process with access to client_body_temp_path, which defaults to a world- accessible directory under the nginx prefix. Add a security comment at the point of the flag assignment documenting: - The nature of the exposure (plaintext temp files regardless of buffer) - The recommended mitigation: client_body_temp_path to a tmpfs mount such as /dev/shm/nginx_body with 0700 permissions - The recommended size limits to constrain disk usage A proper fix would only spool to disk when body size exceeds client_body_buffer_size and use the configured temp path with restrictive permissions. This comment serves as a clear callout for operators reviewing the source and for future refactoring. Severity: High in multi-tenant environments, Medium in single-tenant Reported-by: Security audit 2026-05-13
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Pull request overview
This PR adds an in-source security comment above the r->request_body_in_persistent_file = 1; assignment in the ModSecurity-nginx access handler. The comment documents that ModSecurity-nginx forces request bodies to be spooled to disk as plaintext, and suggests operator mitigations (tmpfs-backed client_body_temp_path, restrictive permissions, and size limits).
Changes:
- Adds a multi-line
SECURITY NOTEcomment inngx_http_modsecurity_access_handlerdescribing the disk-spooling behavior and mitigations. - No functional/code changes.
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request_body_in_persistent_file unconditionally spools all client request bodies to disk as plaintext temporary files. This bypasses client_body_buffer_size, meaning even small bodies end up on disk.
In environments handling sensitive POST data (authentication, payment, health records), this creates plaintext files readable by any process with access to client_body_temp_path, which defaults to a world- accessible directory under the nginx prefix.
Add a security comment at the point of the flag assignment documenting:
A proper fix would only spool to disk when body size exceeds client_body_buffer_size and use the configured temp path with restrictive permissions. This comment serves as a clear callout for operators reviewing the source and for future refactoring.