Lushu

Lushu (short for the Chinese 记录树, 录树), is a system that detects and reacts to user-defined string events in a never-ending stream of text, in real time. The idea is to have pugglable reactions (JVM functions) be triggered whenever the string event occurs. That reaction can be obfuscation of the string, counting occurrences, sending an alert email, etc. To know more about Lushu, read its companion paper or watch its video tutorial.

Running

Video Tutorial

Check out this 3-minute Lushu Tutorial on YouTube.

Simulate Lushu

Run gradle fatJar to generate the file ./Lushu/build/libs/Lushu.jar. Run it following the example:

cat example/log/test/cpf-is-sensitive.log | \
  java -jar ./Lushu/build/libs/Lushu.jar \
    ./example/config.yaml ./example/log/train/cpf-is-sensitive.log

You should see an output like the following:

Training Lushu Grammar with file './example/log/train/cpf-is-sensitive.log'
----------------------------------------
Training with log: The user <s>000.000.000-01</s> logged in on 2023-04-29 21:42:04.
Training with log: A new user <s>586.431.715-65</s> was created on 2023-04-30 12:48:53.
Training with log: The user <s>000.000.000-01</s> sent a message to user <s>417.231.715-86</s> on 2023-04-30 12:52:47.
Training with log: The product with ID RZbhCMwa was added to the cart by user <s>316.819.054-49</s> on 2023-04-30 12:53:36.
----------------------------------------
Finished training grammar

A new user ***** was created on 2023-04-30 13:16:51.
A payment of $1957800,00 was processed on 2023-04-30 13:16:51.
The user ***** downloaded video.mp4 on 2023-04-30 13:16:51.
...

Generate example Lushu Grammar

Run gradle grammarJar to generate the file ./Lushu/build/libs/Grammar.jar. Run it following the example:

cat example/log/test/simple-ip.log | \
  java -jar ./Lushu/build/libs/Grammar.jar ./example/config.yaml

You should see an ouput like the following:

R0 :: [023]{4,4}[-]{1,1}[04]{2,2}[-]{1,1}[29]{2,2} | R1
R1 :: [0]{2,2}[:]{1,1}[0]{2,2}[:]{1,1}[0]{2,2}[,]{1,1}[123456789]{3,3} | R2
R2 :: [RScdeimov]{4,8} | R3
R3 :: [ehoqrstu]{5,7} | R4
R4 :: [acfmoryz]{4,5} | R5
R5 :: [0123456789]{1,3}[.]{1,1}[0123456789]{1,3}[.]{1,1}[0123456789]{1,3}[.]{1,1}[0123456789]{1,3} | [glo]{3,3} | R6
R6 :: [ehr]{4,4} | R7
R7 :: [abl]{3,3} | R8
R8 :: [abl]{3,3}

Note that the first production of the grammar in rule R5 has the format of an IP address. This is because the file example/log/test/simple-ip.log we gave as an input contains examples of IP addresses at that position.

Run the Merger

Run gradle mergerJar to generate the file ./Lushu/build/libs/Merger.jar. Run it following the example:

echo '8.8.8.8 0.0.0.0' | java -jar ./Lushu/build/libs/Merger.jar ./example/config.yaml

You should get the result:

[08]{1,1}[.]{1,1}[08]{1,1}[.]{1,1}[08]{1,1}[.]{1,1}[08]{1,1}

Notice that both IP addresses 8.8.8.8 and 0.0.0.0 were merged into a single regular expression. Try different combinations, and different number of words! Here are some more examples of words you can input:

• Date: 2023/03/26 2023/02/26 2023/12/11 1999/09/09
• Timestamp: 00:00:00 12:34:56 12:34:57
• Key in KV database: key1#secondary key2#secondary

Also, try specifying different YAML configuration files. You may find it easier to edit the example file in ./example/config.yaml.

Testing

To test, run gradle test. Find all source code for the tests under ./Lushu/src/test/.

Theory

Lushu includes a novel way to merge regular expressions, based on a lattice we call the Regex Lattice. The meet of two regexes in the Regex Lattice indicates the result of their merge. A single word may be composed of multiple lattice nodes. It all depends on how we structure the lattice. For instance, if we say that punctuations are "blacklisted" by "alpha" characters, then their meet will go to the lattice top. This can be configured by the following config.yaml file:

latticeBase:
  alpha:
    interval: 1,32
    charset: "abcdefghijklmnopqrstuvwxyz"
  punct:
    interval: 1,2
    charset: "\"!#\\$%&'()*+,-./:;<>=?@\\[\\]^_`{}|~\\\\"
    blacklist:
      - alpha

Arbitrary text is not in the format we require, originally. So the first thing we do with text is divide it into words separated by space. We call these words tokens. Each token might be composed of multiple lattice nodes. For instance, suppose we have two tokens, ab:c and de:fg. They are first transformed to primitive lattice nodes:

[a]{1,1}[b]{1,1}[:]{1,1}[c]{1,1}
[d]{1,1}[e]{1,1}[:]{1,1}[f]{1,1}[g]{1,1}

These are called primitive because the charset for each node is a single character, and the interval is (1,1). Then, we reduce these primitive nodes into a more compact format. We collapse as much as possible, using the lattice meet to check if the GLB is the Top node. If it is the top node, we do not merge the nodes. For our example:

reduce([a]{1,1}[b]{1,1}[:]{1,1}[c]{1,1}) ==>
  [ab]{2,2}[:]{1,1}[c]{1,1}

reduce([d]{1,1}[e]{1,1}[:]{1,1}[f]{1,1}[g]{1,1}) ==>
  [de]{2,2}[:]{1,1}[fg]{2,2}

Finally, two turn these two regular expressions into one, we perform a zip and then a map operation (in the functional sense). The zip operation checks that the lists must have the same size and forms pairs like ([ab]{2,2}, [de]{2,2}). For each pair, we map their elements to their lattice meet. In a pseudo-functional syntax:

map(zip(nodes1, nodes2), (first, second) => {
     lattice.meet(first, second)
})

If the lattice goes to top, the words are not mergeable. Otherwise, we merge them. The result for our example would be:

merge(ab:c, de:fg) =
  map(zip(reduce(ab:c), reduce(de:fg)), (first, second) -> {
    lattice.meet(first, second).then { it ->
        when(it) {
            is Top: not mergeable
            else: it
        }
  })

==> merge(ab:c, de:fg) = [abde]{2,2}[:]{1,1}[cfg]{1,2}