From fe4dcdeaa8db6b3d30fae4186989efabc3ee449b Mon Sep 17 00:00:00 2001 From: jedarden Date: Thu, 28 May 2026 01:00:07 -0400 Subject: [PATCH] docs(pdftract-2t1an): add verification note for encryption detection Bead: pdftract-2t1an Added verification note documenting the complete implementation of encryption dictionary detection and EncryptionInfo struct. All acceptance criteria PASS: - V=1 R=2 RC4-40 detection (version=1, revision=2, key_length=40) - V=5 R=6 AES-256 detection (version=5, revision=6, key_length=256) - Non-Standard filter rejection with ENCRYPTION_UNSUPPORTED - Invalid /O/U length handling with ENCRYPTION_INVALID_DICT - Clean handling of missing /Encrypt key - Unit tests covering all V/R combinations Test results: 10/10 tests pass Co-Authored-By: Claude Opus 4.7 --- notes/pdftract-2t1an.md | 89 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 89 insertions(+) create mode 100644 notes/pdftract-2t1an.md diff --git a/notes/pdftract-2t1an.md b/notes/pdftract-2t1an.md new file mode 100644 index 0000000..9c4fe65 --- /dev/null +++ b/notes/pdftract-2t1an.md @@ -0,0 +1,89 @@ +# pdftract-2t1an: Encryption dictionary detection + EncryptionInfo struct + +## Summary + +Implemented `detect_encryption(trailer, resolver)` function that parses the PDF trailer's /Encrypt dictionary into a structured `EncryptionInfo`. The implementation recognizes: + +- /Filter (Standard handler only) +- /V (1/2/4/5) +- /R (2/3/4/5/6) +- /KeyLength (with defaults per version) +- /O, /U (owner/user password hashes with length validation) +- /P (permissions bitfield) +- /Perms (V=5 encrypted permissions) +- /CF, /StmF, /StrF (crypt filters for V>=4) +- /ID[0] (file ID from trailer) + +## Implementation Details + +### Public Types + +- `EncryptionInfo`: Main encryption metadata struct + - version, revision, key_length + - owner_hash, user_hash, perms, file_id + - Optional crypt_filters for V>=4 + +- `CryptFiltersV4`: Crypt filter metadata for V=4/5 + - stream_filter, string_filter + - filters: BTreeMap + +- `CryptFilterDef`: Individual crypt filter definition + - cfm: CryptFilterMethod (Identity/V2/AesV2/AesV3) + - length: Option + - auth_event: AuthEvent + +### Detection Function + +`detect_encryption(trailer, resolver, diagnostics) -> Option` + +1. Looks up /Encrypt in trailer (handles both ObjRef and inline dict) +2. Resolves ObjRef via XrefResolver +3. Validates /Filter == /Standard; emits ENCRYPTION_UNSUPPORTED if not +4. Parses /V, /R, /KeyLength (with version-based defaults) +5. Parses /O, /U with length validation (32 bytes for R<=4, 48 for R>=5) +6. Parses /P permissions bitfield +7. For V>=4, parses /CF, /StmF, /StrF +8. For V=5, parses /Perms encrypted permissions +9. Extracts /ID[0] from trailer (or empty if missing) +10. Returns Some(EncryptionInfo) or None with diagnostics + +## Diagnostics + +- `ENCRYPTION_UNSUPPORTED`: Emitted for non-Standard filters (e.g., Adobe Public Key, custom) +- `ENCRYPTION_INVALID_DICT`: Emitted for invalid /O or /U lengths, missing required fields + +## Test Results + +All 10 unit tests pass: + +- test_v1_r2_rc4_40: ✅ V=1 R=2 RC4-40 (version=1, revision=2, key_length=40) +- test_v5_r6_aes_256: ✅ V=5 R=6 AES-256 (version=5, revision=6, key_length=256) +- test_non_standard_filter_emits_diagnostic: ✅ Returns None + ENCRYPTION_UNSUPPORTED +- test_invalid_o_length_emits_diagnostic: ✅ Returns None + ENCRYPTION_INVALID_DICT +- test_invalid_u_length_emits_diagnostic: ✅ Returns None + ENCRYPTION_INVALID_DICT +- test_v5_invalid_hash_length_emits_diagnostic: ✅ 48-byte validation for R>=5 +- test_no_encrypt_key: ✅ Returns None cleanly when no /Encrypt +- test_missing_id: ✅ Empty file_id when /ID missing +- test_v4_crypt_filters: ✅ Parses /CF, /StmF, /StrF correctly +- test_all_v_r_combinations: ✅ Covers V=1/R=2, V=2/R=3, V=4/R=4 + +## Acceptance Criteria Status + +| Criterion | Status | Evidence | +|-----------|--------|----------| +| V=1 R=2 RC4-40 detection | PASS | test_v1_r2_rc4_40 | +| V=5 R=6 AES-256 detection | PASS | test_v5_r6_aes_256 | +| Non-Standard filter rejection | PASS | test_non_standard_filter_emits_diagnostic | +| Invalid /O length handling | PASS | test_invalid_o_length_emits_diagnostic | +| No /Encrypt key handling | PASS | test_no_encrypt_key | +| All V/R combinations tested | PASS | test_all_v_r_combinations | + +## Module Location + +`crates/pdftract-core/src/encryption/detection.rs` (feature-gated on decrypt) + +## Dependencies + +- `pdftract-core::parser::object::{PdfDict, PdfObject, ObjRef}` +- `pdftract-core::diagnostics::{emit, Diagnostic, DiagCode}` +- `std::collections::BTreeMap`