The engine will match the first possible way to accept the current character and proceed to the next one. Most Regex engines will work very similarly (with minor differences).
The dramatic difference is due to the way regular expressions get evaluated. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The entire process of testing it against a 30 characters long string takes around ~52ms. $ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'ġ.79s user 0.02s system 99% cpu 1.812 total It most cases, it doesn't take very long for a regex engine to find a match: $ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'Ġ.04s user 0.01s system 95% cpu 0.052 total The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD D Finally, we ensure this section of the string ends with a 'D'.
The + at the end of this section states that we can look for one or more matches of this section.
(B|C+)+ The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the + matches one or more times). A The string must start with the letter 'A'. This regular expression accomplishes the following: Let’s take the following regular expression as an example: regex = /A(B|C+)+D/ Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down. The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process. Var attack_str = "\u001B["+" ".repeat(i*10000) Ĭonsole.log("attack_str.length: " + attack_str.length + ": " + time_cost+" ms")ĭenial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. txt).Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) due to the sub-patterns ()# ?]* and PoC import ansiRegex from 'ansi-regex' The best way -and only?- to check if the flac are 100% correct is uncompressing the flac I have now to wav and compare the md5 of the wav I get with the md5 of the original wav (I have it on a. I have the original wav md5 (the ripper ripped the Cd to wav and then converted it to ape, so I have both md5). ape albums that I transfered to flac, using first Monkey's Audio 5.59 to convert ape to wav, and then I used flac_frontend to convert the wav to flac. (If one chooses to compare new and old MD5, then beware of a possibly fake MD5 in the old file). Suggestion: "verify" by comparing new and old. 
I found them by searching up the temporary files and fixing the file suffix, and then they were bit-identical. In addition, a few files were not successfully renamed. The application would then overwrite the old FLAC files with "empty" ones, destroying the music. However, I then tried to fill a drive completely and put the recompression at work. I used it to recompress a larger number of files, and upon bitcomparing afterwards, I found a couple to be truncated by a few minutes the new files were technically valid FLAC files though.įresh copies from the backup then recompressed just fine, and I was never able to reproduce the error as such. Quote from: Porcus on 07:32:56 The application is not safe to use, not even with the verify option.
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