docs: publish blog post about new scanner (#168)

site/content/blog/a-new-parser-for-yara/index.md

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+---
+title: "An new parser for YARA"
+description: ""
+summary: ""
+date: 2024-07-31T00:00:00+01:00
+lastmod: 2024-07-31T00:00:00+01:00
+draft: true
+weight: 50
+categories: [ ]
+tags: [ ]
+contributors: [ "Victor M. Alvarez" ]
+pinned: false
+homepage: false
+seo:
+  title: "" # custom title (optional)
+  description: "" # custom description (recommended)
+  canonical: "" # custom canonical URL (optional)
+  noindex: false # false (default) or true
+---
+
+One of the design goals for YARA-X was to create a parser that could be reused
+in various tools like code formatters, linters, automatic rule generators. In
+YARA, the parser is so tightly coupled with the code generator that it cannot
+be repurposed. This forced developers to write their own parser for YARA rules,
+leading to many unofficial parsers that often fell behind the official version.
+
+From the outset, YARA-X aimed to address this by providing a reusable parser
+that produced both an Abstract Syntax Tree (AST), and a Concrete Syntax Tree
+(CST), also known as a lossless syntax tree. The CST retains all source code
+details, like comments, newlines, and spacing, which are crucial for tools like
+code formatters. This parser was initially based in the
+excellent [Pest](https://pest.rs/) library.
+
+However, starting with version 0.6.0, we decided to replace Pest with our own
+custom-made parser. The reasons are twofold: first, the Pest parser is not
+error-tolerant and aborts parsing at the first syntax error; second, the
+produced CST is not modifiable, making it impractical for use cases like
+automated code refactoring.
+
+This issue was highlighted by [Tomáš Ďuriš](https://github.com/TommYDeeee)
+and [Marek Milkovič](https://github.com/metthal) from Gen Digital. At Gen
+Digital they are heavy users of YARA and were excited about the YARA-X project.
+They contacted me early on, offering their help and many interesting ideas. One
+of areas in which they wanted to contribute was in creating a Language Server
+for Visual Studio Code.
+
+A Visual Studio Code Language Server implements the Language Server Protocol
+(LSP), which allows for features such as code completion, error checking,
+navigation, and refactoring. It enhances the coding experience by providing
+real-time feedback and intelligent code editing features. However, while the
+Pest-based parser was an improvement over the legacy YARA parser, it was still
+insufficient for implementing an LSP.
+
+With the help of Tomáš Ďuriš, who conducted the initial research and
+prototyping, I embarked on a major refactoring effort. This resulted in the
+complete removal of the Pest-based parser and the creation of a new parser that
+addresses all the previously mentioned shortcomings.
+
+The new parser is error-resilient, and in the future it will be capable of
+producing a modifiable CST. Additionally, it is faster for certain rules that
+were pathologically bad cases for the Pest-based parser. For instance, this
+seemingly simple YARA rule fails to compile with YARA-X 0.5.0 but works
+perfectly with version 0.6.0.
+
+```yara
+rule bad { condition: (((((((((( true )))))))))) }
+```
+
+With these changes, the groundwork has been laid for developing more advanced
+and powerful tools that can leverage the improved parsing capabilities.