fix(storage-simulator): prevent path traversal in mock S3 server#14915
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adrianjoshua-strutt wants to merge 1 commit into
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fix(storage-simulator): prevent path traversal in mock S3 server#14915adrianjoshua-strutt wants to merge 1 commit into
adrianjoshua-strutt wants to merge 1 commit into
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The mock storage simulator (localhost:20005) was vulnerable to path traversal via crafted object keys combined with the prefix query parameter. An attacker with network access to the simulator could read, write, or delete arbitrary files on the developer workstation. Root cause: parseUrl() applied path.normalize() to the full request URL including the query string, causing ../ sequences in query parameter values to be resolved as path traversal. Additionally, the single-character leading dot/slash strip was insufficient to prevent traversal when the prefix query parameter injected multiple ../ sequences. Fix: 1. Strip query string before calling path.normalize() on the URL 2. Add post-normalization check rejecting paths containing .. or absolute paths (falls back to basename only) 3. Add defense-in-depth assertPathWithinRoot() validation in every filesystem-accessing handler (GET, PUT, POST, DELETE, LIST) Tested: normal S3 operations (put, get, delete, list, multipart) continue to work. Path traversal attempts are blocked.
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Summary
Fixes a path traversal vulnerability in the mock storage simulator (
amplify-storage-simulator) that allows arbitrary file read/write/delete outside the configured storage directory on a developer's workstation.Root Cause
parseUrl()inutils.tscalledpath.normalize(decodeURIComponent(request.url))on the full URL including the query string. This caused../sequences in query parameter values (e.g.?prefix=../../) to be resolved as filesystem path traversal bypath.normalize(). Combined with the insufficient single-character strip of a leading.or/, an attacker with network access to the simulator (localhost:20005) could escape the storage root.Attack vector:
PUT /test-bucket/ESCAPE/pwned.txt/?prefix=../..writes a file one level above the configured storage directory.Fix
request.url.split('?')[0]before passing topath.normalize()params.paththat starts with..or is absolute after all normalization (falls back topath.basename())assertPathWithinRoot()checks - added to every handler (GET, PUT, POST, DELETE, LIST) that performs filesystem operations, validating that the resolved path stays within the storage rootTesting
Impact
Limited to developers running
amplify mock storagewho also have port 20005 reachable from untrusted networks or processes. No AWS production infrastructure affected.