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88 lines
2.7 KiB
TypeScript
88 lines
2.7 KiB
TypeScript
/**
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* This file is used to pad message buffer and attachments
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*/
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const PADDING_BYTE = 0x00;
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/**
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* Unpad the buffer from its padding.
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* An error is thrown if there is no padding.
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* A padded buffer is
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* * whatever at start
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* * ends with 0x80 and any number of 0x00 until the end
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*/
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export function removeMessagePadding(paddedData: ArrayBuffer): ArrayBuffer {
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const paddedPlaintext = new Uint8Array(paddedData);
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window?.log.info('Removing message padding...');
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for (let i = paddedPlaintext.length - 1; i >= 0; i -= 1) {
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if (paddedPlaintext[i] === 0x80) {
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const plaintext = new Uint8Array(i);
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plaintext.set(paddedPlaintext.subarray(0, i));
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return plaintext.buffer;
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} else if (paddedPlaintext[i] !== PADDING_BYTE) {
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window?.log.warn('got a message without padding... Letting it through for now');
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return paddedPlaintext;
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}
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}
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throw new Error('Invalid padding');
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}
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/**
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* Add padding to a message buffer
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* @param messageBuffer The buffer to add padding to.
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*/
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export function addMessagePadding(messageBuffer: Uint8Array): Uint8Array {
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window?.log?.info('Adding message padding...');
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const plaintext = new Uint8Array(getPaddedMessageLength(messageBuffer.byteLength + 1) - 1);
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plaintext.set(new Uint8Array(messageBuffer));
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plaintext[messageBuffer.byteLength] = 0x80;
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return plaintext;
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}
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function getPaddedMessageLength(originalLength: number): number {
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const messageLengthWithTerminator = originalLength + 1;
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let messagePartCount = Math.floor(messageLengthWithTerminator / 160);
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if (messageLengthWithTerminator % 160 !== 0) {
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messagePartCount += 1;
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}
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return messagePartCount * 160;
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}
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/*
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* If the attachment has padding, remove the padding and return the unpad attachment
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*/
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export function getUnpaddedAttachment(
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data: ArrayBuffer,
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unpaddedExpectedSize: number
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): ArrayBuffer | null {
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window?.log?.info('Removing attachment padding...');
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// to have a padding we must have a strictly longer length expected
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if (data.byteLength <= unpaddedExpectedSize) {
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return null;
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}
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// we now consider that anything coming after the expected size is padding, no matter what there is there
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return data.slice(0, unpaddedExpectedSize);
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}
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export function addAttachmentPadding(data: ArrayBuffer): ArrayBuffer {
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const originalUInt = new Uint8Array(data);
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window?.log.info('Adding attchment padding...');
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const paddedSize = Math.max(
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541,
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Math.floor(Math.pow(1.05, Math.ceil(Math.log(originalUInt.length) / Math.log(1.05))))
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);
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const paddedData = new ArrayBuffer(paddedSize);
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const paddedUInt = new Uint8Array(paddedData);
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paddedUInt.fill(PADDING_BYTE, originalUInt.length);
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paddedUInt.set(originalUInt);
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return paddedUInt.buffer;
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}
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