Generate FLIRT signatures from analyzed binaries (Makesig)

The built-in Makesig plugin is a tool for generating FLIRT signatures from a current database. This tutorial shows how to create signatures from an analyzed binary.

For more background on the Makesig plugin, see the Makesig plugin overview on the Hex-Rays blog.

How to make signatures from a working database

1. Export the patterns from the database into a .sig file.

   • In the opened database, navigate to File → Produce file → Create SIG file....

   • Configure the options in the Create .sig file dialog and click OK.

   

   Create .sig file dialog

   By default, Makesig skips unnamed functions (sub_, loc_, etc.). To include them, uncheck Valid, user-specified names only in the Create .sig file dialog.

2. Re-import the .sig into the target database.

   • Go to File → Load file → FLIRT signature file... and select the .sig file you exported.

Example: Migrating function names across binary versions

Here is a real scenario: a long-term reversing project with frequent new versions. With the Makesig plugin, you can migrate the carefully curated list of functions that you already reverse-engineered and exported as a signature file into the current binary (given that compiler flags didn’t change too much between releases). Say you identified an interesting function in the older release (source) binary and want to port that information to the newer binary:

You can export a signature file for this function via File → Produce file → Create SIG file...

Create .sig file dialog

Then, in the target database, you can import the signature file in the Signatures window. Open it via View → Open subviews → Signatures. Right-click to open the context menu and choose Apply new signature.... In the List of available library modules dialog, click Load SIG file... and select the .sig file you exported earlier.

Import signature

IDA applies the signature and reports that it found a match in the new database. And indeed, you can find the function, labeled as a library function, because its function name came from the signature file:

Applied signature