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SheetZilla (sheets in ghidra)
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docz/docs/03-demos/32-extensions/41-ghidra.md
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357
docz/docs/03-demos/32-extensions/41-ghidra.md
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---
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title: Sheets in Ghidra
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sidebar_label: Ghidra
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pagination_prev: demos/cloud/index
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pagination_next: demos/bigdata/index
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sidebar_custom_props:
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summary: Generate spreadsheets from Ghidra-generated bitfield tables
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---
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import current from '/version.js';
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import CodeBlock from '@theme/CodeBlock';
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[Ghidra](https://ghidra-sre.org/) is a software reverse engineering platform
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with a robust Java-based extension system.
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[SheetJS](https://sheetjs.com) is a JavaScript library for reading and writing
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data from spreadsheets.
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The [Complete Demo](#complete-demo) uses SheetJS to export data from a Ghidra
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script. We'll create an extension that loads the [V8](/docs/demos/engines/v8)
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JavaScript engine through the Ghidra.js[^1] integration and uses the SheetJS
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library to export a bitfield table from Apple Numbers to a XLSX workbook.
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:::note Tested Deployments
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This demo was tested by SheetJS users in the following deployments:
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| Architecture | Ghidra | Date |
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|:-------------|:---------|:-----------|
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| `darwin-arm` | `11.1.2` | 2024-10-13 |
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:::
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## Integration Details
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Ghidra natively supports scripts that are run in Java. JS extension scripts
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require a [JavaScript engine](/docs/demos/engines/) with Java bindings.
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Ghidra.js[^1] is a Ghidra integration for [RhinoJS](/docs/demos/engines/rhino),
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[GraalJS](/docs/demos/engines/graaljs) and [V8](/docs/demos/engines/v8#java).
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The current version uses [the Javet V8 binding](https://www.caoccao.com/Javet).
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### Loading SheetJS Scripts
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The [SheetJS NodeJS module](/docs/getting-started/installation/nodejs) can be
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loaded in Ghidra.js scripts using `require`:
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```js title="Loading SheetJS scripts in Ghidra.js"
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const XLSX = require("xlsx");
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```
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:::caution pass
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SheetJS NodeJS modules must be installed in a folder in the Ghidra script path!
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:::
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### Bitfields and Sheets
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Binary file formats commonly use bitfields to compactly store a set of Boolean
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(true or false) flags. For example, in the XLSB file format, the `BrtRowHdr`
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record[^2] encodes [row properties](/docs/csf/features/rowprops). Bit offsets
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91-96 are interpreted as flags marking if a row is hidden or if it is collapsed.
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#### Assembly Implementation
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Functions that parse bitfields typically test each bit sequentially:
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```nasm title="x86_64 sample assembly with mnemonics"
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CASE_1c
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41 0f ba e5 1c BT R13D,0x1c
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73 69 JNC CASE_1d
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;; .... Do some work here (bit offset 28)
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CASE_1d
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41 0f ba e5 1d BT R13D,0x1d
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73 69 JNC CASE_1e
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;; .... Do some work here (bit offset 29)
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```
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:::note pass
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The assembly is approximated by the following TypeScript snippet:
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```typescript title="Approximate TypeScript"
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/* R13 is a 64-bit register */
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declare let R13: BigInt;
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/* NOTE: asm R13D is technically a live binding */
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let R13D: number = Number(R13 & 0xFFFFFFFFn);
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if((R13D >> 28) & 1) {
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// .... Do some work here (bit offset 28)
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}
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if((R13D >> 29) & 1) {
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// .... Do some work here (bit offset 29)
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}
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```
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:::
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#### Array of Objects
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A bitmask or bit offset can be paired with a description in a JavaScript object.
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For example, in the `BrtRowHdr` record, bit offset 92 indicates whether the row
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is hidden (if the bit is set) or visible (if the bit is not set). The offset and
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description can be stored as fields in an object:
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```js title="Sample metadata for BrtRowHdr offset 92"
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const metadata_92 = { Offset: 92, Description: "Hidden flag" };
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```
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Each object can be stored in an array:
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```js title="Array of sample metadata for BrtRowHdr"
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const metadata = [
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{ Offset: 91, Description: "Collapsed flag" },
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{ Offset: 92, Description: "Hidden flag" },
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// ...
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];
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```
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This is an ["Array of Objects"](/docs/api/utilities/array#arrays-of-objects).
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The SheetJS `json_to_sheet` method[^3] can generate a SheetJS worksheet object
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from the array:
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```js title="Generating a worksheet from the metadata"
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const ws = XLSX.utils.json_to_sheet(metadata);
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```
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The SheetJS `book_new` method[^4] generates a SheetJS workbook object that can
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be written to the filesystem using the `writeFile` method[^5]:
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```js title="Exporting the worksheet to file"
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const wb = XLSX.utils.book_new(ws, "Offsets");
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XLSX.utils.writeFile(wb, "SheetJSGhidra.xlsx");
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```
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### Java Binding
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Ghidra.js exposes a number of globals for interacting with Ghidra, including:
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- `currentProgram`: information about the loaded program.
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- `JavaHelper`: Java helper to load classes.
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Ghidra.js automatically bridges instance methods to Java method calls. It also
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handles the plugin and file extension details.
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#### Launching the Decompiler
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`ghidra.app.decompiler.DecompInterface` is the primary Java interface to the
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decompiler. In Ghidra.js, `JavaHelper.getClass` will load the class.
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_Java_
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```java title="Launch decompiler process in Java (snippet)"
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import ghidra.app.script.GhidraScript;
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import ghidra.app.decompiler.DecompInterface;
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import ghidra.program.model.listing.Program;
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public class SheetZilla extends GhidraScript {
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@Override public void run() throws Exception {
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DecompInterface ifc = new DecompInterface();
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boolean success = ifc.openProgram(currentProgram);
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/* ... do work here ... */
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}
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}
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```
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_Ghidra.js_
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```js title="Launch decompiler process in Ghidra.js"
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const DecompInterface = JavaHelper.getClass('ghidra.app.decompiler.DecompInterface');
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const decompiler = new DecompInterface();
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decompiler.openProgram(currentProgram);
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```
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#### Identifying a Function
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The `getGlobalSymbols` method of a symbol table instance will return an array of
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symbols matching the given name:
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```js
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/* name of function to find */
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const fname = 'MyMethod';
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/* find symbols matching the name */
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// highlight-next-line
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const fsymbs = currentProgram.getSymbolTable().getGlobalSymbols(fname);
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/* get first result */
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const fsymb = fsymbs[0];
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```
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The `getFunctionAt` method of a function manager instance will take an address
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and return a reference to a function:
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```js
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/* get address */
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const faddr = fsymb.getAddress();
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/* find function */
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// highlight-next-line
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const fn = currentProgram.getFunctionManager().getFunctionAt(faddr);
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```
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#### Decompiling a Function
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The `decompileFunction` method attempts to decompile the referenced function:
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```js
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/* decompile function */
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// highlight-next-line
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const decomp = decompiler.decompileFunction(fn, 10000, null);
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```
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Once decompiled, it is possible to retrieve the decompiled C code:
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```js
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/* get generated C code */
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const src = decomp.getDecompiledFunction().getC();
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```
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## Complete Demo
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In this demo, we will inspect the `_TSTCellToCellStorage` method within the
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`TSTables` framework of Apple Numbers 14.2. This particular method handles
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serialization of cells to the NUMBERS file format.
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The implementation has a number of blocks which look like the following script:
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```js
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if(flags >> 0x0d & 1) {
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const field = "numberFormatID";
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const current_value = cell[field];
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// ... check if current_value is set, do other stuff
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}
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```
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Based on the bit offset and the field name, we will generate the following row:
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```js
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const mask = 1 << 0x0d; // = 8192 = 0x2000
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const name = "number format ID";
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const row = { Mask: "0x" + mask.toString(16), "Internal Name": name };
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```
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Rows will be generated for each block and the final dataset will be exported.
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### System Setup
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0) Install Ghidra, Xcode, and Apple Numbers.
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<details>
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<summary><b>Installation Notes</b> (click to show)</summary>
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On macOS, Ghidra was installed using Homebrew:
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```bash
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brew install --cask ghidra
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```
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</details>
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1) Add the base Ghidra folder to the PATH variable. The following shell command
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adds to the path for the current `zsh` or `bash` session:
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```bash
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export PATH="$PATH":$(dirname $(realpath `which ghidraRun`))
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```
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2) Install `ghidra.js` globally:
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```bash
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npm install -g ghidra.js
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```
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:::note pass
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If the install fails with a permissions issue, install with the root user:
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```bash
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sudo npm install -g ghidra.js
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```
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:::
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### Program Preparation
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3) Create a temporary folder to hold the Ghidra project:
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```bash
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mkdir -p /tmp/sheetjs-ghidra
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```
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4) Copy the `TSTables` framework to the current directory:
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```bash
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cp /Applications/Numbers.app/Contents/Frameworks/TSTables.framework/Versions/Current/TSTables .
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```
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5) Create a "thin" binary by extracting the `x86_64` part of the framework:
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```bash
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lipo TSTables -thin x86_64 -output TSTables.macho
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```
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:::info pass
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When this demo was last tested, the headless analyzer did not support Mach-O fat
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binaries. `lipo` creates a new binary with support for one architecture.
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:::
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6) Analyze the program:
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```bash
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$(dirname $(realpath `which ghidraRun`))/support/analyzeHeadless /tmp/sheetjs-ghidra Numbers -import TSTables.macho
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```
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:::note pass
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This process may take a while and print a number of Java stacktraces. The errors
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can be ignored.
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:::
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### SheetJS Integration
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7) Download [`sheetjs-ghidra.js`](pathname:///ghidra/sheetjs-ghidra.js):
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```bash
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curl -LO https://docs.sheetjs.com/ghidra/sheetjs-ghidra.js
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```
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8) Install the [SheetJS NodeJS module](/docs/getting-started/installation/nodejs):
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<CodeBlock language="bash">{`\
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npm i --save https://cdn.sheetjs.com/xlsx-${current}/xlsx-${current}.tgz`}
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</CodeBlock>
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9) Run the script:
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```bash
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$(dirname $(realpath `which ghidraRun`))/support/analyzeHeadless /tmp/sheetjs-ghidra Numbers -process TSTables.macho -noanalysis -scriptPath `pwd` -postScript sheetjs-ghidra.js
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```
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10) Open the generated `SheetJSGhidraTSTCell.xlsx` spreadsheet.
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[^1]: The project does not have a website. The [source repository](https://github.com/vaguue/Ghidra.js) is publicly available.
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[^2]: `BrtRowHdr` is defined in the [`MS-XLSB` specification](/docs/miscellany/references)
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[^3]: See [`json_to_sheet` in "Utilities"](/docs/api/utilities/array#array-of-objects-input)
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[^4]: See [`book_new` in "Utilities"](/docs/api/utilities/wb)
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[^5]: See [`writeFile` in "Writing Files"](/docs/api/write-options)
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@ -86,6 +86,7 @@ in the [issue tracker](https://git.sheetjs.com/sheetjs/docs.sheetjs.com/issues)
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- [`MATLAB`](/docs/demos/extensions/matlab)
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- [`Stata`](/docs/demos/extensions/stata)
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- [`Maple`](/docs/demos/extensions/maple)
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- [`Ghidra`](/docs/demos/extensions/ghidra)
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### Cloud Platforms
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@ -181,7 +181,7 @@ const config = {
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}
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})
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},
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additionalLanguages: [ "visual-basic", "swift", "java", "php", "csharp", "perl", "ruby", "cpp", "applescript", "liquid", "rust", "dart", "wolfram", "matlab", "stata", "zig", "diff", "bash", "json" ],
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additionalLanguages: [ "visual-basic", "swift", "java", "php", "csharp", "perl", "ruby", "cpp", "applescript", "liquid", "rust", "dart", "wolfram", "matlab", "stata", "zig", "diff", "bash", "json", "nasm" ],
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},
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liveCodeBlock: {
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playgroundPosition: 'top'
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70
docz/static/ghidra/sheetjs-ghidra.js
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docz/static/ghidra/sheetjs-ghidra.js
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const { utils: { book_new, json_to_sheet }, writeFileXLSX } = require("xlsx");
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/* start decompiler */
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const DecompInterface = JavaHelper.getClass('ghidra.app.decompiler.DecompInterface');
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const decompiler = new DecompInterface();
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decompiler.openProgram(currentProgram);
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/* get decompiled C source */
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const src = (() => {
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const fname = '_TSTCellToCellStorage';
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/* find address to function */
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const fsymbs = currentProgram.getSymbolTable().getGlobalSymbols(fname);
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if(!fsymbs) throw new Error(`Global Symbol ${fname} cannot be found`);
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/* find function */
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const fn = currentProgram.getFunctionManager().getFunctionAt(fsymbs[0].getAddress());
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if(!fn) throw new Error(`Function ${fname} cannot be found`);
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/* decompile function */
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const decomp = decompiler.decompileFunction(fn, 10000, null);
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if (decomp.isTimedOut() || !decomp.decompileCompleted()) throw new Error(`Function ${fname} at ${fn} could not be decompiled`);
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/* get and return generated C code */
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const src = decomp.getDecompiledFunction().getC();
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if(!src) throw new Error(`Function ${fname} at ${fn} decompilation`);
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return src;
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})();
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/* offset[n] will be the name of the field at bit `n` (mask `1 << n`) */
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let offset = [];
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/* combine split lines and lazily extract data from C source */
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let n = -1;
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src.split(/[\r\n]+/).reduce((acc,row,i) => {
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if(i <= 9) acc.rows.push(row);
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else if(row.match(/[{};]$/)) {
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if(acc.buf) { row = acc.buf + row.trim(); acc.buf = ""; }
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acc.rows.push(row);
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} else acc.buf += acc.buf ? row.trim() : row.replace(/[\r\n]+$/,"");
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return acc;
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}, {rows:[], buf:""}).rows.forEach(line => {
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if(line.match(/^ if.*(char|short| >> | & )/)) {
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n = -1;
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if(!line.match(/Var/)) return;
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if(line.match(/char/)) n = 7;
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else if(line.match(/short/)) n = 15;
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else if(line.match(/>>/)) n = parseInt(line.match(/>> ([1-9]\d*|0x[0-9a-f]+)/)[1]);
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else if(line.match(/&/)) n = Math.round(Math.log2(parseInt(line.match(/& ([1-9]\d*|0x[0-9a-f]+)/)[1])));
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} else if(line.match(/PTR__objc_msgSend/) && n >= 0) {
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if(line.match(/AssertionHandler|NSString|stringWithUTF8String|Failure/)) return;
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if(!line.match(/,/)) return; // suppress noop
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const ptr = line.match(/PTR_s_\w+/)[0];
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offset[+n] = ptr;
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n = -1;
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}
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});
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/* construct objects with "Mask" (hex string) and "Internal Name" */
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const aoo = offset.map((name, idx) => ({
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Mask: "0x" + (1 << idx).toString(16),
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"Internal Name": name.replace(/^PTR_s_|_[0-9a-f]*$/g,"").replace(/[A-Z]/g, " $&").toLowerCase().replace(/ i d/, " ID")
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}));
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/* create worksheet */
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const ws = json_to_sheet(aoo);
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/* write workbook */
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const wb = book_new(ws, "Offsets");
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/* write to XLSX */
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writeFileXLSX(wb, "SheetJSGhidraTSTCell.xlsx");
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