Merge branch 'MP3Extractor' of https://github.com/n1073645/CyberChef into n1073645-MP3Extractor

This commit is contained in:
n1474335 2020-03-26 12:01:30 +00:00
commit ad0a2e6f58

View File

@ -780,7 +780,7 @@ export const FILE_SIGNATURES = {
1: 0xfb
}
],
extractor: null
extractor: extractMP3
},
{
name: "MPEG-4 Part 14 audio",
@ -3067,6 +3067,79 @@ export function extractWAV(bytes, offset) {
}
/**
* MP3 extractor.
*
* @param {Uint8Array} bytes
* @param {Number} offset
* @returns {Uint8Array}
*/
export function extractMP3(bytes, offset) {
const stream = new Stream(bytes.slice(offset));
// Constants for flag byte.
const bitRateIndexes = ["free", 32000, 40000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 160000, 192000, 224000, 256000, 320000, "bad"];
const samplingRateFrequencyIndex = [44100, 48000, 32000, "reserved"];
// ID3 tag, move over it.
if ((stream.getBytes(3).toString() === [0x49, 0x44, 0x33].toString())) {
stream.moveTo(6);
const tagSize = (stream.readInt(1) << 21) | (stream.readInt(1) << 14) | (stream.readInt(1) << 7) | stream.readInt(1);
stream.moveForwardsBy(tagSize);
} else {
stream.moveTo(0);
}
// Loop over all the frame headers in the file.
while (stream.hasMore()) {
// If it has an old TAG frame at the end of it, fixed size, 128 bytes.
if (stream.getBytes(3) === [0x54, 0x41, 0x47].toString()) {
stream.moveForwardsBy(125);
break;
}
// If not start of frame.
if (stream.getBytes(2).toString() !== [0xff, 0xfb].toString()) {
stream.moveBackwardsBy(2);
break;
}
// Read flag byte.
const flags = stream.readInt(1);
// Extract frame bit rate from flag byte.
const bitRate = bitRateIndexes[flags >> 4];
// Extract frame sample rate from flag byte.
const sampleRate = samplingRateFrequencyIndex[(flags & 0x0f) >> 2];
// Padding if the frame size is not a multiple of the bitrate.
const padding = (flags & 0x02) >> 1;
// Things that are either not standard or undocumented.
if (bitRate === "free" || bitRate === "bad" || sampleRate === "reserved") {
stream.moveBackwardsBy(1);
break;
}
// Formula: FrameLength = (144 * BitRate / SampleRate ) + Padding
const frameSize = Math.floor(((144 * bitRate) / sampleRate) + padding);
// If the next move goes past the end of the bytestream then extract the entire bytestream.
// We assume complete frames in the above formula because there is no field that suggests otherwise.
if ((stream.position + frameSize) > stream.length) {
stream.moveTo(stream.length);
break;
} else {
stream.moveForwardsBy(frameSize - 3);
}
}
return stream.carve();
}
/**
* FLV extractor.
*