src/pqc_rag_signing/verifier.py
| 1 | """Retrieval-time verification wrapper for RAG pipelines.""" |
| 2 | |
| 3 | from __future__ import annotations |
| 4 | |
| 5 | from dataclasses import dataclass, field |
| 6 | from datetime import datetime, timezone |
| 7 | from typing import Iterable |
| 8 | |
| 9 | from pqc_rag_signing.chunk import SignedChunk |
| 10 | from pqc_rag_signing.errors import TamperedChunkError |
| 11 | from pqc_rag_signing.signer import ChunkSigner, VerificationResult |
| 12 | |
| 13 | |
| 14 | @dataclass |
| 15 | class RetrievalResult: |
| 16 | """Aggregate result of verifying a batch of retrieved chunks.""" |
| 17 | |
| 18 | total: int |
| 19 | verified: list[SignedChunk] = field(default_factory=list) |
| 20 | failed: list[tuple[SignedChunk, VerificationResult]] = field(default_factory=list) |
| 21 | verified_at: str = "" |
| 22 | trusted_signers: set[str] = field(default_factory=set) |
| 23 | |
| 24 | @property |
| 25 | def all_verified(self) -> bool: |
| 26 | return len(self.failed) == 0 |
| 27 | |
| 28 | @property |
| 29 | def verified_count(self) -> int: |
| 30 | return len(self.verified) |
| 31 | |
| 32 | @property |
| 33 | def failed_count(self) -> int: |
| 34 | return len(self.failed) |
| 35 | |
| 36 | def verified_texts(self) -> list[str]: |
| 37 | """Return ONLY the text content of verified chunks - safe for LLM.""" |
| 38 | return [c.text for c in self.verified] |
| 39 | |
| 40 | |
| 41 | class RetrievalVerifier: |
| 42 | """Verify chunks retrieved from a vector DB before passing to an LLM. |
| 43 | |
| 44 | Supports optional allow-list of trusted signer DIDs. Chunks signed by |
| 45 | anyone NOT in the allow-list (if set) are rejected even if cryptographically |
| 46 | valid. |
| 47 | |
| 48 | Usage: |
| 49 | verifier = RetrievalVerifier( |
| 50 | trusted_signers={"did:pqaid:abc123..."}, |
| 51 | strict=True, |
| 52 | ) |
| 53 | result = verifier.verify_retrieved(signed_chunks) |
| 54 | if not result.all_verified: |
| 55 | # handle failures |
| 56 | ... |
| 57 | safe_texts = result.verified_texts() |
| 58 | """ |
| 59 | |
| 60 | def __init__( |
| 61 | self, |
| 62 | trusted_signers: set[str] | None = None, |
| 63 | strict: bool = True, |
| 64 | ) -> None: |
| 65 | self.trusted_signers = trusted_signers |
| 66 | self.strict = strict |
| 67 | |
| 68 | def verify_retrieved( |
| 69 | self, |
| 70 | chunks: Iterable[SignedChunk], |
| 71 | ) -> RetrievalResult: |
| 72 | """Verify each chunk, bucket into verified vs failed.""" |
| 73 | result = RetrievalResult( |
| 74 | total=0, |
| 75 | verified_at=datetime.now(timezone.utc).isoformat(), |
| 76 | trusted_signers=self.trusted_signers or set(), |
| 77 | ) |
| 78 | for chunk in chunks: |
| 79 | result.total += 1 |
| 80 | verification = ChunkSigner.verify_chunk(chunk) |
| 81 | |
| 82 | if ( |
| 83 | verification.valid |
| 84 | and self.trusted_signers |
| 85 | and chunk.signer_did not in self.trusted_signers |
| 86 | ): |
| 87 | verification = VerificationResult( |
| 88 | valid=False, |
| 89 | chunk_id=chunk.chunk_id, |
| 90 | signer_did=chunk.signer_did, |
| 91 | algorithm=chunk.algorithm, |
| 92 | error=f"signer {chunk.signer_did} not in trusted allow-list", |
| 93 | ) |
| 94 | |
| 95 | if verification.valid: |
| 96 | result.verified.append(chunk) |
| 97 | else: |
| 98 | result.failed.append((chunk, verification)) |
| 99 | |
| 100 | return result |
| 101 | |
| 102 | def verify_or_raise( |
| 103 | self, |
| 104 | chunks: Iterable[SignedChunk], |
| 105 | ) -> list[SignedChunk]: |
| 106 | """Like verify_retrieved, but raises on any failure.""" |
| 107 | result = self.verify_retrieved(chunks) |
| 108 | if not result.all_verified: |
| 109 | first_fail = result.failed[0] |
| 110 | raise TamperedChunkError( |
| 111 | f"{result.failed_count}/{result.total} chunks failed " |
| 112 | f"verification. First failure: {first_fail[1].error}" |
| 113 | ) |
| 114 | return result.verified |
| 115 | |