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pdfStandardV4

AGPL-3.0-onlyRelease 2L4

Standard Security Handler V=4, R=4 — PDF 1.6 legacy (RC4-128 / AES-128-CBC).

Module pdfStandardV4 | Source packages/front/office/pdf/src/crypto/standardV4.js | Deps pdfErrors, aes, cbc, bitArray | Worker-safe yes

Implements ISO 32000-1 §7.6.3 Algorithm 2 (128-bit file-key derivation, 50 rounds of MD5), Algorithm 3 (/O), Algorithm 5 (/U), and per-object key derivation for the two V=4 crypt filter methods selectable via /CF /StdCF:

  • AESV2 — AES-128-CBC; per-object key = MD5(fileKey ‖ objId(3 LE) ‖ gen(2 LE) ‖ "sAlT") truncated to min(fileKey.len + 5, 16); ciphertext is IV-prefixed, PKCS#7 padded.
  • V2 — RC4-128; per-object key = MD5(fileKey ‖ objId(3 LE) ‖ gen(2 LE)) truncated the same way.

MD5 and RC4 are implemented locally (this handler predates fw's hash/cipher family and both primitives are legacy-only) — aes/cbc are the only fw crypto deps, for the AESV2 path.

Resolve

const v4 = runtime.resolve('pdfStandardV4');
// Returns: { tryPassword, decryptString, decryptStream,
//            decryptEmbeddedFile, encryptEmbeddedFile,
//            encryptString, encryptStream,
//            buildOU, buildPerms,
//            computeFileKey, computeU, computeO,
//            objectKey, rc4, md5, padPassword, PASSWORD_PADDING }

API

Method Signature Returns
tryPassword (typedEncrypt: { O, U, P, idFirst, EncryptMetadata? }, password, isOwner: boolean) => { fileEncryptionKey: Uint8Array | null } null FEK on rejection; recovers the user password from /O first when isOwner.
decryptString (typedEncrypt: { method }, fek, objNum, gen, ciphertext) => Uint8Array Dispatches on typedEncrypt.method ('AESV2' or 'V2'/'RC4').
decryptStream same signature as decryptString Alias — identical implementation.
decryptEmbeddedFile same signature as decryptString Alias for the /EFF-resolved method (ISO 32000-1 §7.6.5).
encryptString (typedEncrypt: { method }, fek, objNum, gen, plaintext, iv?) => Uint8Array iv (16 bytes) required for 'AESV2'; ignored for RC4.
encryptStream same signature as encryptString Alias — identical implementation.
encryptEmbeddedFile same signature as encryptString Alias for the /EFF write path.
buildOU (ownerPassword, userPassword, P, idFirst: Uint8Array, encryptMetadata) => { O, U, fek } Builds a fresh /O + /U pair and the derived 16-byte file key.
buildPerms () => null No-op — /Perms (Algorithm 8) is V≥5 only; kept for handler-dispatch symmetry with V5/V6.
computeFileKey / computeU / computeO internal Algorithm 2/5/3 primitives Exposed for testing/interop.
objectKey (fileKey, objNum, gen, isAes: boolean) => Uint8Array Per-object key derivation.
rc4 / md5 stream-cipher / hash primitives Exposed for testing.
padPassword (password: string | Uint8Array) => Uint8Array The 32-byte padded password of Algorithm 2 step (a). Exposed for testing/interop.
PASSWORD_PADDING Uint8Array (32 bytes) The Algorithm 2 padding string.

Examples

Password check then decrypt (read side)

const v4 = runtime.resolve('pdfStandardV4');
const r = v4.tryPassword(
    { O, U, P, idFirst, EncryptMetadata: true }, 'user', false);
if (!r.fileEncryptionKey) throw new Error('bad password');
const plain = v4.decryptStream(
    { method: 'AESV2' }, r.fileEncryptionKey, objNum, gen, encryptedBytes);

Building /O + /U for a fresh document (write side)

const v4 = runtime.resolve('pdfStandardV4');
const { O, U, fek } = v4.buildOU('owner', 'user', -4, idFirst, true);

This is the handler pdfEncryptedWriter selects internally for version: 4, revision: 4.

Errors

All thrown as EncryptionError.

Code When
pdf/crypto/v4/missing-fw aes/cbc/bitArray fw modules unavailable (thrown at module construction).
pdf/crypto/v4/bad-password Password argument is neither string nor Uint8Array.
pdf/crypto/v4/bad-O /O is not a 32-byte Uint8Array (computeFileKey).
pdf/crypto/v4/bad-id First /ID element missing/invalid (computeFileKey, buildOU).
pdf/crypto/v4/bad-O-U /O or /U not exactly 32 bytes (tryPassword).
pdf/crypto/v4/bad-string AESV2 ciphertext shorter than 16 bytes (missing IV).
pdf/crypto/v4/bad-method method neither 'AESV2' nor 'V2'/'RC4' (decrypt or encrypt side).
pdf/crypto/v4/encrypt-bad-input encryptString plaintext is not a Uint8Array.
pdf/crypto/v4/encrypt-bad-iv AESV2 encrypt iv is not exactly 16 bytes.
pdf/crypto/v4/bad-ciphertext-len / bad-pt-len AES-CBC input length not a multiple of 16.
pdf/crypto/v4/aes-schedule-failed / aes-encrypt-schedule fw AES-128 key schedule failed.
pdf/crypto/v4/cbc-decrypt-failed / cbc-encrypt-failed fw CBC operation failed.

See also