fix: prevent cross-session image leakage and cross-instance nonce replay#40
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nirholas wants to merge 1 commit into
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fix: prevent cross-session image leakage and cross-instance nonce replay#40nirholas wants to merge 1 commit into
nirholas wants to merge 1 commit into
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Three bugs fixed: 1. Cross-session image leakage (agent.py + tools.py) IMAGE_STORAGE was a module-level dict written by every session. When two concurrent invocations ran, the first response to extract IMAGE_STORAGE could receive images belonging to the other session, then clear() left the second response empty. Images are now stored and extracted from per-session SessionStorage exclusively; the global fallback dicts are removed. 2. Cross-instance nonce replay (both seller Lambdas) processedPayments was an in-process Map. AWS Lambda scales horizontally, so a second Lambda instance had no knowledge of nonces seen by the first. An attacker could submit the same EIP-712 signature to a fresh instance and receive content without paying. Nonces are now written atomically to DynamoDB (ConditionExpression: attribute_not_exists) before verification passes, shared across all instances. Falls back to the in-process Map when NONCE_TABLE_NAME is absent so local dev is unaffected. 3. Stale signature replay (both seller Lambdas) The seller never checked whether a payment signature was recent. Signatures older than MAX_PAYMENT_AGE_SEC (300 s) are now rejected with payment_expired before they reach the facilitator. Also adds startup configuration validation in agent.py (validate_config()) so misconfigured deployments fail immediately with a clear error instead of at request time.
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Three bugs fixed:
Cross-session image leakage (agent.py + tools.py) IMAGE_STORAGE was a module-level dict written by every session. When two concurrent invocations ran, the first response to extract IMAGE_STORAGE could receive images belonging to the other session, then clear() left the second response empty. Images are now stored and extracted from per-session SessionStorage exclusively; the global fallback dicts are removed.
Cross-instance nonce replay (both seller Lambdas) processedPayments was an in-process Map. AWS Lambda scales horizontally, so a second Lambda instance had no knowledge of nonces seen by the first. An attacker could submit the same EIP-712 signature to a fresh instance and receive content without paying. Nonces are now written atomically to DynamoDB (ConditionExpression: attribute_not_exists) before verification passes, shared across all instances. Falls back to the in-process Map when NONCE_TABLE_NAME is absent so local dev is unaffected.
Stale signature replay (both seller Lambdas) The seller never checked whether a payment signature was recent. Signatures older than MAX_PAYMENT_AGE_SEC (300 s) are now rejected with payment_expired before they reach the facilitator.
Also adds startup configuration validation in agent.py (validate_config()) so misconfigured deployments fail immediately with a clear error instead of at request time.
Issue #, if available:
Description of changes:
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