awaforge

pdfLegacyRc4Read

AGPL-3.0-onlyRelease 2L4

RC4 v2/v3 password validation + stream decrypt, read-only — legacy.

Module pdfLegacyRc4Read | Source packages/front/office/pdf/src/extra/legacy-rc4-read.js | Deps pdfErrors | Worker-safe yes

Implements the RC4 stream cipher locally plus the read side of the Standard Security Handler PDF 1.7 §7.6.3.3-4: 40-bit RC4 (revision 2, V=1) and 128-bit RC4 (revision 3, V=2), password validation against /O//U, per-object key derivation (file-key ‖ objectId/MD5) for /Encrypt V <= 2. PDF 2.0 forbids RC4 on write; this module is intentionally read-only.

Resolve

const ext = runtime.resolve('pdfLegacyRc4Read');
// Returns: { rc4, md5, padPassword, computeFileKey, computeU,
//   validateUserPassword, objectKey, decryptString,
//   decryptStream, PASSWORD_PADDING }

API

Member Signature Returns
rc4 (key: Uint8Array, data: Uint8Array) => Uint8Array Stream cipher.
md5 (bytes) => Uint8Array(16) Hash.
padPassword (password) => Uint8Array(32) §7.6.3.3 step 1.
computeFileKey (password, params: { O, P, idFirst, revision, keyLength, encryptMetadata }) => Uint8Array File-key derivation, §7.6.3.3 Algorithm 2.
computeU (fileKey, idFirst, revision) => Uint8Array Computes the /U value.
validateUserPassword (password, params: { O, P, idFirst, revision, keyLength, encryptMetadata, U }) => { ok: true, fileKey } | { ok: false }
objectKey (fileKey, objNum, gen) => Uint8Array Per-object key.
decryptString / decryptStream (fileKey, objNum, gen, bytes) => Uint8Array
PASSWORD_PADDING Uint8Array(32) Padding constant, §7.6.3.3.

Examples

Validate a password

const ext = runtime.resolve('pdfLegacyRc4Read');
const r = ext.validateUserPassword('', {
    O, P, idFirst, revision: 3, keyLength: 128, encryptMetadata: true, U
});
if (!r.ok) throw new Error('wrong password');
const fileKey = r.fileKey;

Decrypt a stream

const plain = ext.decryptStream(fileKey, 5, 0, encStreamBytes);

Errors

Code Class When
pdf/rc4/bad-input EncryptionError rc4 arguments invalid.
pdf/md5/bad-input EncryptionError md5 input is not a Uint8Array.
pdf/rc4/bad-password EncryptionError Password/pad input invalid.
pdf/rc4/bad-O EncryptionError /O invalid (must be a 32-byte Uint8Array).
pdf/rc4/bad-id EncryptionError /ID first element missing/invalid.

See also