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Fix sig cipher and n function extraction #86

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Dec 8, 2024
Merged

Fix sig cipher and n function extraction #86

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40 changes: 18 additions & 22 deletions common/src/main/java/dev/lavalink/youtube/cipher/SignatureCipherManager.java
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Original file line number Diff line number Diff line change
Expand Up @@ -50,17 +50,17 @@ public class SignatureCipherManager {
private static final String BEFORE_ACCESS = "(?:\\[\\\"|\\.)";
private static final String AFTER_ACCESS = "(?:\\\"\\]|)";
private static final String VARIABLE_PART_ACCESS = BEFORE_ACCESS + VARIABLE_PART + AFTER_ACCESS;
private static final String REVERSE_PART = ":function\\(a\\)\\{(?:return )?a\\.reverse\\(\\)\\}";
private static final String SLICE_PART = ":function\\(a,b\\)\\{return a\\.slice\\(b\\)\\}";
private static final String SPLICE_PART = ":function\\(a,b\\)\\{a\\.splice\\(0,b\\)\\}";
private static final String SWAP_PART = ":function\\(a,b\\)\\{" +
"var c=a\\[0\\];a\\[0\\]=a\\[b%a\\.length\\];a\\[b(?:%a.length|)\\]=c(?:;return a)?\\}";
private static final String REVERSE_PART = ":function\\(\\w\\)\\{(?:return )?\\w\\.reverse\\(\\)\\}";
private static final String SLICE_PART = ":function\\(\\w,\\w\\)\\{return \\w\\.slice\\(\\w\\)\\}";
private static final String SPLICE_PART = ":function\\(\\w,\\w\\)\\{\\w\\.splice\\(0,\\w\\)\\}";
private static final String SWAP_PART = ":function\\(\\w,\\w\\)\\{" +
"var \\w=\\w\\[0\\];\\w\\[0\\]=\\w\\[\\w%\\w\\.length\\];\\w\\[\\w(?:%\\w.length|)\\]=\\w(?:;return \\w)?\\}";

private static final Pattern functionPattern = Pattern.compile(
"function(?: " + VARIABLE_PART + ")?\\(a\\)\\{" +
"a=a\\.split\\(\"\"\\);\\s*" +
"((?:(?:a=)?" + VARIABLE_PART + VARIABLE_PART_ACCESS + "\\(a,\\d+\\);)+)" +
"return a\\.join\\(\"\"\\)" +
"function(?: " + VARIABLE_PART + ")?\\(([a-zA-Z])\\)\\{" +
"\\1=\\1\\.split\\(\"\"\\);\\s*" +
"((?:(?:\\1=)?" + VARIABLE_PART + VARIABLE_PART_ACCESS + "\\(\\1,\\d+\\);)+)" +
"return \\1\\.join\\(\"\"\\)" +
"\\}"
);

Expand All @@ -80,14 +80,14 @@ public class SignatureCipherManager {
private static final Pattern splicePattern = Pattern.compile(PATTERN_PREFIX + SPLICE_PART, Pattern.MULTILINE);
private static final Pattern swapPattern = Pattern.compile(PATTERN_PREFIX + SWAP_PART, Pattern.MULTILINE);
private static final Pattern timestampPattern = Pattern.compile("(signatureTimestamp|sts):(\\d+)");

private static final Pattern nFunctionPattern = Pattern.compile(
"function\\(\\s*(\\w+)\\s*\\)\\s*\\{" +
"var\\s*(\\w+)=(?:\\1\\.split\\(.*?\\)|String\\.prototype\\.split\\.call\\(\\1,.*?\\))," +
"\\s*(\\w+)=(\\[.*?]);\\s*\\3\\[\\d+]" +
"(.*?try)(\\{.*?})catch\\(\\s*(\\w+)\\s*\\)\\s*\\{" +
"\\s*return\"enhanced_except_([A-z0-9-]+)\"\\s*\\+\\s*\\1\\s*}" +
"\\s*return\\s*(\\2\\.join\\(\"\"\\)|Array\\.prototype\\.join\\.call\\(\\2,.*?\\))};", Pattern.DOTALL
);
"\\s*return\"[\\w-]+([A-z0-9-]+)\"\\s*\\+\\s*\\1\\s*}" +
"\\s*return\\s*(\\2\\.join\\(\"\"\\)|Array\\.prototype\\.join\\.call\\(\\2,.*?\\))};", Pattern.DOTALL);

private final ConcurrentMap<String, SignatureCipher> cipherCache;
private final Set<String> dumpedScriptUrls;
Expand Down Expand Up @@ -244,9 +244,9 @@ private SignatureCipher extractFromScript(@NotNull String script, @NotNull Strin
String swapKey = extractDollarEscapedFirstGroup(swapPattern, actionBody);

Pattern extractor = Pattern.compile(
"(?:a=)?" + Pattern.quote(actions.group(1)) + BEFORE_ACCESS + "(" +
"(?:\\w=)?" + Pattern.quote(actions.group(1)) + BEFORE_ACCESS + "(" +
String.join("|", getQuotedFunctions(reverseKey, slicePart, splicePart, swapKey)) +
")" + AFTER_ACCESS + "\\(a,(\\d+)\\)"
")" + AFTER_ACCESS + "\\(\\w,(\\d+)\\)"
);

Matcher functions = functionPattern.matcher(script);
Expand All @@ -255,23 +255,19 @@ private SignatureCipher extractFromScript(@NotNull String script, @NotNull Strin
throw new IllegalStateException("Must find decipher function from script.");
}

Matcher matcher = extractor.matcher(functions.group(1));
Matcher matcher = extractor.matcher(functions.group(2));

if (!scriptTimestamp.find()) {
dumpProblematicScript(script, sourceUrl, "no timestamp match");
throw new IllegalStateException("Must find timestamp from script: " + sourceUrl);
}

String nFunction = "";

if (nFunctionMatcher.find()) {
nFunction = nFunctionMatcher.group(0);
} else {
// Don't throw any exceptions here since if n function is not extracted audio still can be played
if (!nFunctionMatcher.find()) {
dumpProblematicScript(script, sourceUrl, "no n function match");
throw new IllegalStateException("Must find n function from script: " + sourceUrl);
}

SignatureCipher cipherKey = new SignatureCipher(nFunction, scriptTimestamp.group(2), script);
SignatureCipher cipherKey = new SignatureCipher(nFunctionMatcher.group(0), scriptTimestamp.group(2), script);

while (matcher.find()) {
String type = matcher.group(1);
Expand Down
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